Acta Ophthalmol (Copenh). 1980 Aug;58(4):507-11.
Hyvärinen L, Näsänen R, Laurinen P.
A new test chart was developed for the measurement of visual acuity of pre-school children. The symbols of the test are circle, square, apple and house. These were so designed that each symbol measures visual acuity similarly. This feature of the test was verified experimentally. The visual acuity values measured by the individual symbols correlated highly with the visual acuity values measured with the whole test (0.82-0.86). The correlation between the visual acuity values measured repeatedly, the reliability of the new test, was found to be 0.94 for adult subjects. The new visual acuity test thus fulfils the statistical criteria of a good visual acuity test. Because both children and nurses seem to like the new test, it may be useful in the assessment of visual acuity in pre-school children.
Optom Vis Sci.2009 May 4. [Epub ahead of print]
Vision in Preschoolers (VIP) Study Group.
The Vision in Preschoolers (VIP) Study Group conducted a multicenter, multidisciplinary, two-phase study to evaluate the performance of vision screening tests for identifying pre-school children with amblyopia, strabismus, significant refractive error, or unexplained reduced visual acuity (VA). The results of the VIP Study provide evidence-based guidelines for preschool vision screening. The best screening tests administered by eye care professionals were non-cycloplegic retinoscopy, Retinomax Autorefractor, SureSight Vision Screener, and linear, crowded Lea Symbols VA at 10 feet. The best screening tests administered by trained nurses and/or lay screeners were Retinomax, SureSight, and VIP single, crowded Lea Symbols VA screening test system at 5 feet. Eye care professionals can improve detection of strabismus by combining unilateral cover test with a refraction test and trained lay screeners can improve detection of strabismus by combining Stereo Smile II with SureSight. The best performing tests had high testability whether performed by trained eye care professionals, nurses, or lay screeners (>/=98%). Although very few children were unable to complete these tests, a child who was "unable" was much more likely to have a vision problem than a child who passed; therefore, children who are unable to complete one of these tests should be referred for further evaluation. When screening using the Retinomax, repeated testing to achieve the manufacturer's suggested confidence number is valuable and improves specificity. Federal initiatives to increase the number of pre-school children receiving vision screening or examination will increase the number of pre-school children identified with amblyopia, strabismus, and/or significant refractive error. Although there is general agreement regarding the importance of early detection of amblyopia, controversy exists regarding the importance of early detection of refractive error. Because of the high prevalence of significant refractive errors and lack of evidenced-based guidelines for correction of refractive error in pre-school children, future research is needed to evaluate the value of correcting refractive errors in preschoolers who do not have amblyopia and/or strabismus.
J AAPOS. 2009 Apr 2. [Epub ahead of print]
A comparison of Lea Symbol vs ETDRS letter distance visual acuity in a population of young children with a high prevalence of astigmatism.
Dobson V, Clifford-Donaldson CE, Miller JM, Garvey KA, Harvey EM.
Author affiliations: Department of Ophthalmology and Vision Science, the University of Arizona, Tucson, Arizona.
PURPOSE: To compare visual acuity results obtained by use of the Lea Symbols chart with results obtained with Early Treatment Diabetic Retinopathy Study (ETDRS) charts in young children who are members of a population with a high prevalence of astigmatism. METHODS: Subjects were 438 children ages 5 through 7 years who were enrolled in kindergarten or first grade on the Tohono O'odham Reservation: 241 (55%) had astigmatism >/=1.00 D in one or both eyes (range, 0.00-6.75 D). While wearing best correction, each child had right eye visual acuity tested with the 62 cm by 65 cm Lea Symbols chart at 3 m and with the 62 cm by 65 cm ETDRS chart at 4 m. Visual acuity was scored as the smallest optotype size at which the child correctly identified 3 of a maximum of 5 optotypes. ETDRS visual acuity also was scored based on the total number of letters that the child correctly identified. RESULTS: Correlation between Lea Symbols visual acuity and ETDRS visual acuity was 0.78 (p < 0.001). Mean Lea Symbols visual acuity was one-half line (0.04-0.06 logMAR) better than mean ETDRS visual acuity (p < 0.001). The difference between Lea Symbols and ETDRS visual acuity was not correlated with the mean of the Lea Symbols and ETDRS visual acuity scores, which ranged from -0.3 logMAR (20/10) to 0.74 logMAR (20/110). CONCLUSIONS: In this population of young children, in whom the primary source of reduced visual acuity is astigmatism-related amblyopia, the Lea Symbols chart produced visual acuity scores that were about 0.5 line better than visual acuity scores obtained with ETDRS charts.
Ophthalmology. 2009 May;116(5):1002-8. Epub 2009 Feb 20.
Optical treatment reduces amblyopia in astigmatic children who receive spectacles before kindergarten.
Dobson V, Clifford-Donaldson CE, Green TK, Miller JM, Harvey EM.
Department of Ophthalmology and Vision Science, University of Arizona, 655 N. Alvernon Way, Tucson, AZ 85711, USA.
OBJECTIVE: To examine the effect of spectacle correction of astigmatism during preschool on best-corrected recognition visual acuity (VA), grating VA, and meridional amblyopia (difference between acuity for vertical versus horizontal gratings) once the children reach kindergarten. DESIGN: Comparative case series. PARTICIPANTS: Seventy-three astigmatic (right eye > or =1.50 diopters [D] cylinder) Native American (Tohono O'odham) children 5 to 7 years of age. All had with-the-rule astigmatism. In 28 children, the astigmatism was simple myopic, compound myopic, or mixed (M/MA), and in 45 children, it was simple or compound hyperopic (HA). INTERVENTION: Thirty-nine children (Treated Group) had spectacle correction of refractive error, prescribed for full-time wear, in preschool (0.8-2.4 years before testing). Thirty-four children (Untreated Group) had no prior correction. MAIN OUTCOME MEASURE: Comparison of Treated versus Untreated Groups for mean best-corrected right-eye recognition VA, measured with the Early Treatment Diabetic Retinopathy Study (ETDRS) chart and the Lea Symbols chart, for grating VA, measured with modified Teller acuity card stimuli, and for meridional amblyopia, based on grating acuity results. RESULTS: Mean ETDRS VA was significantly better in the Treated Group (20/37) than in the Untreated Group (20/48; P<0.003), but the difference between mean Lea Symbols VA in the Treated Group (20/33) and in the Untreated Group (20/38) was not significant. No significant Treated versus Untreated Group differences were found for either vertical or horizontal grating acuity. Meridional amblyopia differed between the M/MA group, which showed better acuity for vertical than for horizontal gratings, and the HA group, which showed better acuity for horizontal than for vertical gratings. However, in neither the M/MA group nor the HA group was there a significant difference in magnitude of meridional amblyopia in the Treated versus the Untreated Group. CONCLUSIONS: Spectacle correction during the preschool years results in a significant improvement in best-corrected letter recognition acuity in astigmatic children by the time they reach kindergarten. However, grating acuity was not improved and magnitude of meridional amblyopia was not reduced in children who had received early spectacle correction. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found after the references.
J Pak Med Assoc. 2008 Mar;58(3):125-8.
Causes of amblyopia in children coming to ophthalmology out patient department Khyber Teaching Hospital, Peshawar.
Sethi S, Sethi MJ, Hussain I, Kundi NK.
Khyber Teaching Hospital, Peshawar.
OBJECTIVE: To find the causes of amblyopia in patients 4 to 14 years old attending out patient Ophthalmology department of Khyber teaching Hospital Peshawar. METHODS: In this prospective cohort hospital based study 200 children aged 4-14 years were studied over a period of 12 months from December 2005 to November 2006 in outpatient department of Ophthalmology, Khyber Teaching Hospital. Visual acuity was checked with Snellen's and Lea symbols depending on level of cooperation of patient. Cycloplegic refraction and orthoptic assessment was performed on all patients. Amblyopia was classified as strabismic, anisometropic, combined and stimulus deprivation. Treatment consisted of optical correction, patching, atropinization and surgery. RESULTS: Out of 200 patients 126 (63%) were male and 74 (37%) were female, 114 (57%) were in age group 4-9 years while 86 (43%) were between 10-14 years. Strabismic amblyopia was present in 110 (55%), Anisometropic amblyopia in 42 (21%), combined mechanism amblyopia in 32 (16%), ammetropia in 12 (6%) and stimulus deprivation amblyopia in 4 (2%) Binocularity could not be assessed in 16 (8%), was present in 38 (19%) and absent in 148 (73%). CONCLUSION: Amblyopia was more common in males than females. Most of the children presented in younger age group of 4-9 years. Strabismic amblyopia was the most common cause of amblyopia. Amblyopia was more common in esotropes than exotropes. Half of the patients had moderate amblyopia, while the remaining were suffering from either mild or severe amblyopia. Binocularity was absent in 73% of the patients
Invest Ophthalmol Vis Sci. 2007 Jul;48(7):3115-25.
Does assessing eye alignment along with refractive error or visual acuity increase sensitivity for detection of strabismus in preschool vision screening? Vision in Preschoolers Study Group.
The Vision in Preschoolers Study Group, The Ohio State University, College of Optometry, Columbus, OH 43210-1280, USA.
PURPOSE: Preschool vision screenings often include refractive error or visual acuity (VA) testing to detect amblyopia, as well as alignment testing to detect strabismus. The purpose of this study was to determine the effect of combining screening for eye alignment with screening for refractive error or reduced VA on sensitivity for detection of strabismus, with specificity set at 90% and 94%. METHODS: Over 3 years, 4040 preschool children were screened in the Vision in Preschoolers (VIP) Study, with different screening tests administered each year. Examinations were performed to identify children with strabismus. The best screening tests for detecting children with any targeted condition were noncycloplegic retinoscopy (NCR), Retinomax autorefractor (Right Manufacturing, Virginia Beach, VA), SureSight Vision Screener (Welch-Allyn, Inc., Skaneateles, NY), and Lea Symbols (Precision Vision, LaSalle, IL and Good-Lite Co., Elgin, IL) and HOTV optotypes VA tests. Analyses were conducted with these tests of refractive error or VA paired with the best tests for detecting strabismus (unilateral cover testing, Random Dot "E" [RDE] and Stereo Smile Test II [Stereo Optical, Inc., Chicago, IL]; and MTI PhotoScreener [PhotoScreener, Inc., Palm Beach, FL]). The change in sensitivity that resulted from combining a test of eye alignment with a test of refractive error or VA was determined with specificity set at 90% and 94%. RESULTS: Among the 4040 children, 157 were identified as having strabismus. For screening tests conducted by eye care professionals, the addition of a unilateral cover test to a test of refraction generally resulted in a statistically significant increase (range, 15%-25%) in detection of strabismus. For screening tests administered by trained lay screeners, the addition of Stereo Smile II to SureSight resulted in a statistically significant increase (21%) in sensitivity for detection of strabismus. CONCLUSIONS: The most efficient and low-cost ways to achieve a statistically significant increase in sensitivity for detection of strabismus were by combining the unilateral cover test with the autorefractor (Retinomax) administered by eye care professionals and by combining Stereo Smile II with SureSight administered by trained lay screeners. The decision of whether to include a test of alignment should be based on the screening program's goals (e.g., targeted visual conditions) and resources.
Invest Ophthalmol Vis Sci. 2007 Jan;48(1):83-7.
Children unable to perform screening tests in vision in preschoolers study: proportion with ocular conditions and impact on measures of test accuracy.
Maguire MG; Vision in Preschoolers Study Group.
Coordinating Center, 3535 Market Street, Suite 700, Philadelphia, PA 19104-3309, USA.
PURPOSE: To examine the relative prevalence of ocular conditions among children who are unable to perform preschool vision screening tests and the impact on measures of screening test performance. METHODS: Trained nurse and lay screeners each administered a Lea Symbols visual acuity (VA) test (Good-Lite, Inc., Steamwood, IL), Stereo Smile II test (Stereo Optical, Inc., Chicago, IL), and Retinomax Autorefractor (Right Manufacturing, Virginia Beach, VA), and SureSight Vision Screener (Welch Allyn, Inc., Skaneateles Falls, NY) examinations to 1475 children who later received a comprehensive eye examination to identify amblyopia, strabismus, significant refractive error, and unexplained reduced VA. The outcomes of the examination for children for whom screeners were unable to obtain results (Unables) were compared to the outcomes of children who passed and children who failed each screening test. When estimating sensitivity, specificity, and positive and negative predictive values (PPV and NPV), Unables were classified as either screening failures or screening passers. RESULTS: Less than 2% of children were classified as Unables for each test. The percentage with an ocular condition was at least two times higher for Unables than for screening passers for six of the eight modes of screening (P < 0.05). Considering Unables as screening failures, rather than screening passers, increased the estimate of sensitivity by 1% to 3% (depending on test) and decreased the estimate of specificity by 0% to 2%; PPV decreased by 0% to 4% for most tests, whereas NPV increased by <1%. CONCLUSIONS: Preschool children who are unable to perform VIP screening tests are more likely to have vision disorders than are children who pass the tests. Because < or =2% of children were unable to do each test, referring these children for an eye examination had little impact on the PPV and NPV of the tests, as administered in VIP.
Acta Ophthalmol Scand. 2006 Dec;84(6):807-11.
Sensitivity and specificity of a visual acuity screening protocol performed with the Lea Symbols 15-line folding distance chart in preschool children.
Bertuzzi F, Orsoni JG, Porta MR, Paliaga GP, Miglior S.
Policlinico di Monza Hospital, Ophthalmology Clinic, University of Milano-Bicocca, Milan, Italy.
PURPOSE: The aim of this study was to assess the feasibility of a visual acuity (VA) test using the Lea Symbols 15-line folding distance chart and its diagnostic validity in detecting VA deficiency in preschool children. METHODS: A group of 149 children aged 38-54 months underwent VA examination performed with the Lea 15-line folding optotype at a distance of 3 metres, according to a test protocol described in the Methods section. After the VA test, a complete ophthalmological examination, including cycloplegic retinoscopy, a cover test and examination of the anterior and posterior segments, was performed on each child in order to detect any VA-threatening ocular abnormality. The Lea Symbols test's sensitivity, specificity, positive and negative likelihood ratios (LR +, LR -) and the receiver operating characteristic (ROC) curve were calculated by means of standard procedures using each VA level of the chart from 0.1 to 1 (1-0 logMAR) as a cut-off point. RESULTS: The Lea Symbols test could be successfully used in 95.9% of the population. The most useful cut-off points for screening preschool children were found to be 0.8 (LR + 5.73, LR - 0.05) or 0.63 (LR + 11.7, LR - 0.23). CONCLUSION: The Lea Symbols test proved to be clinically useful in detecting VA deficiency in preschool children. The choice between the two best performing cut-off levels should be made according to the expected cost-effectiveness of the screening programme.
J Pediatr Ophthalmol Strabismus. 2006 May-Jun;43(3):157-60.
Ruttum MS, Dahlgren M.
The authors are from the Eye Institute, Medical College of Wisconsin, Milwaukee, Wisconsin 53226-4812, USA.
PURPOSE: To determine whether the Lea symbols visual acuity test, compared with the HOTV visual acuity test, overestimates visual acuity in patients with amblyopia. PATIENTS AND METHODS: Fifty-nine patients with amblyopia or a history of amblyopia treatment had visual acuity measurements in both eyes with the HOTV and Lea symbols tests. Crowding bars, separated by a width of 1 optotype, and the original pilot-testing protocol in the Amblyopia Treatment Study were used to quantify visual acuity. RESULTS: The patients' ages ranged from 4 to 35 years (mean age, 10.1 years). Visual acuity in the amblyopic eyes ranged from 20/20 to 20/250. The mean visual acuity difference (HOTV scores vs Lea symbols scores) was -0.056 logMAR units (P < .001), slightly more than half of a line. The negative value indicates that patients performed better on the HOTV test. In nonamblyopic eyes, the mean difference was -0.05 logMAR units (P < .001). Patients with strabismic amblyopia had a mean difference of -0.05 logMAR units (P = .08); those with anisometropic amblyopia had a mean difference of -0.07 logMAR units (P = .002). Patients 8 years and younger had a mean difference of -0.04 logMAR units (P = .05); those older than 8 years had a mean difference of -0.06 logMAR units (P = .002). CONCLUSIONS: In both amblyopic and nonamblyopic eyes, visual acuity measurements were better on HOTV testing compared with Lea symbols testing. The differences persisted regardless of patient age and the cause and severity of amblyopia. Overestimation of visual acuity by the Lea symbols test was not found.
Invest Ophthalmol Vis Sci. 2006 Feb;47(2):614-9.
Chen SI, Chandna A, Norcia AM, Pettet M, Stone D.
Vision Assessment Unit, Department of Ophthalmology, Royal Liverpool Children's Hospital, Liverpool, United Kingdom.
PURPOSE: The main purpose of this work was to measure repeatability of line-by-line logMAR (logarithm of the minimum angle of resolution) acuity in normal and amblyopic children, while adequately controlling for optical defocus. METHODS: The Lea Symbols Chart is a constant-crowding, equal-logMAR increment chart similar in design to the Early Treatment Diabetes Retinopathy Study [ETDRS] chart. LogMAR visual acuity was tested twice in each eye of 32 amblyopic and 11 normal children. Each test commenced with screening in which one of the three central symbols was chosen for identification starting with the 1.0- or 0.9-logMAR line, progressing to every second line until incorrect identification occurred. Symbol-by-symbol presentation then commenced at the logMAR line containing the last correctly identified symbol. The threshold was recorded as the last logMAR line where four of four or four of five correct responses occurred (i.e., line-by-line scoring). Retesting by the same examiner was identical and occurred within the same session. RESULTS: There was no significant difference in repeatability among normal, fellow, or amblyopic eyes. The difference between test and retest thresholds lay between +/-0.10 logMAR in 93% of eyes. The 95% limits of agreement for the difference was +/-0.18 logMAR. Repeatability in eyes tested first did not differ from that in those tested second in either the normal or amblyopic groups. CONCLUSIONS: In the age-group tested, the line-by-line method of threshold scoring compares favorably with previous reports of both line-by-line and interpolated threshold scoring. There was no clinically meaningful difference in repeatability between the normal and amblyopic children tested.
Invest Ophthalmol Vis Sci. 2005 Aug;46(8):2639-48.
Preschool vision screening tests administered by nurse screeners compared with lay screeners in the vision in preschoolers study.
The Vision in Preschoolers Study Group.
PURPOSE: To compare the performance of nurse screeners with that of lay screeners in administering preschool vision screening tests. METHODS: Trained nurse and lay screeners administered the Retinomax Autorefractor (Right Manufacturing, Virginia Beach, VA), SureSight Vision Screener (Welch Allyn, Inc., Skaneateles Falls, NY), crowded Linear Lea Symbols visual acuity (VA) test at 10 ft (Precision Vision, Inc., La Salle, IL), and Stereo Smile II test (Stereo Optical, Inc., Chicago, IL) to 3- to 5-year-old Head Start participants. Lay screeners also administered a crowded Single Lea Symbols VA test at 5 ft (Good-Lite, Inc.). Screening results were compared with the classification of the children according to the presence of one or more of four conditions (amblyopia, strabismus, significant refractive error, and unexplained reduced VA) based on the results of a gold standard eye examination by study-certified optometrists and ophthalmologists. The primary outcome measure was sensitivity for detecting children with one or more targeted conditions at 0.90 specificity. RESULTS: Nurse screeners achieved slightly higher sensitivities with the Retinomax, SureSight, and Stereo Smile II tests than did lay screeners; however, most differences were small and not statistically significant. Nurse screeners achieved significantly higher sensitivity with the Linear Lea Symbols VA test than did lay screeners. Lay screeners achieved strikingly higher sensitivity with the Single Lea Symbols VA test than did nurse or lay screeners using the Linear Lea Symbols VA test. Combining the Stereo Smile II test with each of the other tests did not result in improved sensitivities for detecting one or more targeted conditions. CONCLUSIONS: Nurse and lay screeners can achieve similar sensitivity, when specificity is set at 0.90, for detecting preschool children in need of a comprehensive eye examination.
J Coll Physicians Surg Pak. 2005 Jun;15(6):353-7.
Shah M, Khan MT, Khan MD, Habib ur Rehman.
Department of Ophthalmology, Khyber Institute of Ophthalmic Medical Sciences (KIOMS), Hayatabad Medical Complex, Peshawar.
OBJECTIVE: To study the clinical profile of amblyopia in children age 3 to 14 years. DESIGN: A cohort study. PLACE AND DURATION OF STUDY: The study was conducted over a period of two years from June 2001 to June 2003 at Khyber Institute of Ophthalmic Medical Sciences, Hayatabad Medical Complex, Peshawar, Pakistan. PATIENTS AND METHODS: This study included 316 children. Visual acuity was tested with Snellen type and Lea symbols chart according to the level of cooperation of the children. Cycloplegic refraction and orthoptic assessment was performed on all children. RESULTS: One hundred and eighty-two children were between 3 to 8 years age and 134 were between 8 to 14 years. Mean age was 8 years. One hundred and twenty children had strabismic amblyopia, 136 children had anisometropic amblyopia, while 60 children had combined mechanism amblyopia (strabismus and anisometropia both). CONCLUSION: The results indicate the importance of screening school-going children for refractive error and amblyopia and the importance of a future prospective study on the magnitude, cause and treatment of amblyopia at more treatable age.
Optom Vis Sci. 2005 May;82(5):432-8.
Sensitivity of screening tests for detecting vision in preschoolers-targeted vision disorders when specificity is 94%.
Ying GS, Kulp MT, Maguire M, Ciner E, Cyert L, Schmidt P; Vision in Preschoolers Study Group.
The Ohio State University, College of Optometry, Columbus, OH 43218-2342, USA.
PURPOSE: To compare the sensitivity of 11 preschool vision screening tests administered by licensed eye care professionals for the detection of the 4 Vision in Preschoolers (VIP)-targeted vision disorders when specificity is 94%. METHODS: This study consisted of a sample (n = 2588) of 3- to 5-year-old children enrolled in Head Start programs, 57% of whom had failed an initial Head Start vision screening. Screening results from 11 tests were compared with results from a standardized comprehensive eye examination that was used to classify children with respect to the four VIP-targeted vision disorders: amblyopia, strabismus, significant refractive error, and unexplained reduced visual acuity (VA). With overall specificity set to 94%, we calculated the sensitivity for the detection of each targeted vision disorder. RESULTS: With the overall specificity set to 94%, the most accurate tests for detection of amblyopia were noncycloplegic retinoscopy (NCR) (88% sensitivity), the SureSight Vision Screener (80%), and the Retinomax Autorefractor (78%). For detection of strabismus, the most accurate tests were the MTI Photoscreener (65%), the cover-uncover test (60%), the Stereo Smile II stereoacuity test (58%), the SureSight Vision Screener (54%), and the Retinomax Autorefractor (54% in year 1, 53% in year 2). The most accurate tests for detection of significant refractive error were NCR (74%), the Retinomax Autorefractor (66%), the SureSight Vision Screener (63%), and the Lea Symbols VA test (58%). For detection of reduced VA, the most accurate tests were the Lea Symbols Distance VA test (48%), the Retinomax Autorefractor (39%), and NCR (38%). CONCLUSIONS: Similar to the previously reported results at 90% specificity, the screening tests vary widely in sensitivity with specificity set at 94%. The rankings of the sensitivities for detection of the 4 VIP-targeted vision disorders are similar to those with specificity set to 90%.
Optom Vis Sci. 2004 Sep;81(9):678-83.
Preschool visual acuity screening with HOTV and Lea symbols: testability and between-test agreement.
Vision in Preschoolers Study Group.
PURPOSE: To compare the performance of 3- to 5-year-old children on visual acuity screening with HOTV letters vs. Lea symbols as optotypes. METHODS: Subjects included 1253 Head Start children who were aged either 3 or 4 years on September 1 of the school year of testing. The sample over-represented children who had not passed a Head Start screening. Binocular pretesting at 1 m demonstrated the child's ability to identify the optotypes verbally or by matching optotypes on a lap card. Acuity was tested monocularly at 3 m using crowded single lines of optotypes. Lines tested were based on age at the beginning of the school year (September 1) with 3-year-old children tested with lines 10/100, 10/32, 10/25, and 10/20 and 4-year-old children tested with 10/100, 10/25, 10/20, and 10/16. RESULTS: Overall, 99% of children were able to complete the binocular pretest for each test successfully, and there was no difference between the tests (p = 0.83). Children's ability to complete the pretest increased slightly with age. HOTV test scores were slightly worse than Lea symbols test scores (p = 0.047), primarily because more children were unable to pass the monocular 10/100 card for the HOTV test than for the Lea symbols test (2.6% vs. 1.3%). The percentage of identical results on HOTV vs. Lea overall was 67.3% and increased significantly with age. When the results were different, 3-year-old children, but not 4- and 5-year-old children, tended to have worse results on the HOTV letter test. CONCLUSIONS: The vision of nearly all 3- to 5-year-old children can be screened using either HOTV letters or Lea symbols. HOTV letters may be slightly more difficult than Lea symbols for 3- to 5-year-old children, with the largest difference between acuity results on the two tests occurring in 3-year-old children.
Vision Res. 2004;44(14):1623-34.
Harvey EM, Dobson V, Miller JM, Sherrill DL.
Department of Ophthalmology, The University of Arizona, 655 N. Alvernon, Suite 108, Tucson, AZ 85711, USA.
Best-corrected acuity was measured for vertical and horizontal gratings and for Lea Symbols recognition acuity in 3- to 5-year-old children with high astigmatism and in non-astigmatic children. There was significant amblyopia among astigmatic children at baseline. There was no evidence that eyeglass correction of astigmatism resulted in a reduction in amblyopia over a 4-month average treatment duration (although vision in astigmatic children was significantly improved immediately upon eyeglass correction, indicating that eyeglass correction did provide a visual benefit). Treatment outcome results are discussed in terms of both methodological issues and theoretical implications.
Optom Vis Sci. 2004 Apr;81(4):245-54.
Leat SJ, Wegmann D.
School of Optometry, University of Waterloo, Ontario, Canada.
PURPOSE: The Hiding Heidi (HH) test and the LEA low-contrast symbols are two commercially available charts of contrast sensitivity (CS) for children. However, there are no published normal data and no indication of how CS measured by these charts relates to other measures of CS. In this study, normal age-related data for both tests are reported, and validity against the Pelli-Robson (PR) chart is measured. METHODS: Eighty-eight normally sighted children were divided into four age groups: 1 to <2.5 years, 2.5 to <4 years, 4 to <6 years, and 6 to <8 years. An adult group with normal vision and with low vision also took part. CS was measured with the HH test, the LEA symbols at 1 m and 28 cm, and the PR chart, as the child's ability permitted. Because there were obvious differences between the contrast levels of the PR chart and the nominal contrast for the children's charts, each contrast level for the children's tests was recalibrated. RESULTS: The HH test and the LEA symbols at 28 cm and 1 m all showed a floor effect; that is, most children of all ages correctly responded to the lowest contrast. The median CS for the LEA symbols at 28 cm and 1 m was 2.22 log CS, which was 1.65 when recalibrated. There was a significant difference of PR CS between the 6- to <8-year-olds and adults (p < 0.001). Of the children's charts, the LEA symbols at 28 cm, once recalibrated for contrast, had the best agreement with the PR chart. CONCLUSION: The LEA and HH charts cannot measure a true contrast threshold for children with normal vision because of the floor effect. The LEA symbols at 28 cm gave the most useful information, once recalibrated for contrast, and may be useful to predict performance of children with low vision, when CS is likely to be compromised.
Ophthalmology. 2004 Apr;111(4):637-50.
Ophthalmology. 2004 Dec;111(12):2313-4; author reply 2314-5.
Ophthalmology. 2004 Dec;111(12):2313; author reply 2313.
Comparison of preschool vision screening tests as administered by licensed eye care professionals in the Vision In Preschoolers Study.
Schmidt P, Maguire M, Dobson V, Quinn G, Ciner E, Cyert L, Kulp MT, Moore B, Orel-Bixler D, Redford M, Ying GS; Vision in Preschoolers Study Group.
College of Optometry, The Ohio State University, 320 West Tenth Avenue, PO Box 182342, Columbus, OH 43218-2342, USA.
PURPOSE: To compare 11 preschool vision screening tests administered by licensed eye care professionals (LEPs; optometrists and pediatric ophthalmologists). DESIGN: Multicenter, cross-sectional study. PARTICIPANTS: A sample (N = 2588) of 3- to 5-year-old children enrolled in Head Start was selected to over-represent children with vision problems. METHODS: Certified LEPs administered 11 commonly used or commercially available screening tests. Results from a standardized comprehensive eye examination were used to classify children with respect to 4 targeted conditions: amblyopia, strabismus, significant refractive error, and unexplained reduced visual acuity (VA). MAIN OUTCOME MEASURES: Sensitivity for detecting children with > or =1 targeted conditions at selected levels of specificity was the primary outcome measure. Sensitivity also was calculated for detecting conditions grouped into 3 levels of importance. RESULTS: At 90% specificity, sensitivities of noncycloplegic retinoscopy (NCR) (64%), the Retinomax Autorefractor (63%), SureSight Vision Screener (63%), and Lea Symbols test (61%) were similar. Sensitivities of the Power Refractor II (54%) and HOTV VA test (54%) were similar to each other. Sensitivities of the Random Dot E stereoacuity (42%) and Stereo Smile II (44%) tests were similar to each other and lower (P<0.0001) than the sensitivities of NCR, the 2 autorefractors, and the Lea Symbols test. The cover-uncover test had very low sensitivity (16%) but very high specificity (98%). Sensitivity for conditions considered the most important to detect was 80% to 90% for the 2 autorefractors and NCR. Central interpretations for the MTI and iScreen photoscreeners each yielded 94% specificity and 37% sensitivity. At 94% specificity, the sensitivities were significantly better for NCR, the 2 autorefractors, and the Lea Symbols VA test than for the 2 photoscreeners for detecting > or =1 targeted conditions and for detecting the most important conditions. CONCLUSIONS: Screening tests administered by LEPs vary widely in performance. With 90% specificity, the best tests detected only two thirds of children having > or =1 targeted conditions, but nearly 90% of children with the most important conditions. The 2 tests that use static photorefractive technology were less accurate than 3 tests that assess refractive error in other ways. These results have important implications for screening preschool-aged children.
J AAPOS. 2003 Dec;7(6):396-9.
Threshold visual acuity testing of preschool children using the crowded HOTV and Lea Symbols acuity tests.
Cyert L, Schmidt P, Maguire M, Moore B, Dobson V, Quinn G; Vision in Preschoolers (VIP) Study Group.
Northeastern State University, College of Optometry, Tahlequah, OK, USA.
PURPOSE: To compare the testability and threshold acuity levels for very young children on the crowded HOTV logMAR distance visual acuity test presented on the BVAT apparatus and the Lea Symbols logMAR distance visual acuity chart. METHODS: Subjects were 87 Head Start children from age 3 to 3.5 years. Testing consisted of binocular pretraining at near using a lap card as needed, binocular pretraining at 3 m, and threshold testing for each eye. The testing procedure, adapted from the Amblyopia Treatment Study, presented optotypes until the child was unable to correctly name or match three of three or three of four optotypes of a given size. Threshold acuity was the smallest size for which at least three optotypes were correctly identified. RESULTS: Both near and distance pretraining were completed by 71% of children for HOTV and by 75% for Lea Symbols (P =.39). The distribution of threshold acuities differed between the two tests. For the 69 eyes of 53 children who were successfully tested with both optotypes, results from the crowded HOTV acuity test were on average 0.25 logMar (2.5 lines) better than those from the Lea Symbols acuity test (P <.001). CONCLUSIONS: The proportion of children between 3 and 3.5 years of age whose monocular visual acuity could be assessed was high and was similar for the two charts tested. Crowded HOTV acuity results were better on average than results using Lea symbols. The different formats of the two tests may explain the observed differences in threshold acuity level.
Optom Vis Sci. 2003 Sep;80(9):650-4.
Visual acuity results in school-aged children and adults: Lea Symbols chart versus Bailey-Lovie chart.
Dobson V, Maguire M, Orel-Bixler D, Quinn G, Ying GS; Vision in Preschoolers (VIP) Study Group.
The Vision in Preschoolers Study Center, Ohio State University College of Optometry, 320 West Tenth Avenue, PO Box 182342, Columbus, OH 43218-2342, USA.
PURPOSE: To compare visual acuity results obtained using the Lea Symbols chart with visual acuity results obtained with the Bailey-Lovie chart in school-aged children and adults using a within-subjects comparison of monocular acuity results. METHODS: Subjects were 62 individuals between 4.5 and 60 years of age, recruited from patients seen in five optometry clinics. Each subject had acuity of the right eye and the left eye tested with the Lea Symbols chart and the Bailey-Lovie chart, with order of testing varied across subjects. Outcome measures were monocular logarithm of the minimum angle of resolution (logMAR) visual acuity and inter-eye acuity difference in logMAR units for each test. RESULTS: Correlation between acuity results obtained with the two charts was high. There was no difference in absolute inter-eye acuity difference measured with the two acuity charts. However, on average, Lea Symbols acuity scores were one logMAR line better than Bailey-Lovie acuity scores, and this difference increased with worse visual acuity. CONCLUSIONS: The Lea Symbols chart provides a measure of inter-eye difference that is similar to that obtained with the Bailey-Lovie chart. However, the monocular acuity results obtained with the Lea Symbols chart differ from those obtained with the Bailey-Lovie chart, and the difference is dependent on the individual's absolute level of visual acuity.
Invest Ophthalmol Vis Sci. 2003 Sep;44(9):3756-63.
Miller JM, Dobson V, Harvey EM, Sherrill DL.
Department of Ophthalmology, The Optical Sciences Center, The University of Arizona, Tucson, Arizona 85711, USA.
PURPOSE: To design and test a cost-efficient, community-based vision screening program for a population of Native American preschool children in which there is a high prevalence of astigmatism. METHODS: Based on analysis of vision screening and eye examination data from a preschool population with a 33% prevalence of astigmatism, comparative costs to conduct a 1000-child screening program with a target sensitivity of 90% were estimated for photoscreening, noncycloplegic autorefraction, autokeratometry, and Lea symbols distance visual acuity testing. Results of the cost analysis and examination of sensitivity and specificity data from the preschool population led to development of a hybrid screening program of autokeratometry and visual acuity screening with referral thresholds of 2.25 D of corneal astigmatism or inability to read a 20/63 Lea symbols line on two separate attempts. The screening program was prospectively implemented in a community-based screening of a similar cohort of 167 children, and its efficiency was evaluated by comparison to results of cycloplegic refraction. RESULTS: The community-based screening showed 96.8% sensitivity and 79.2% specificity for detecting the presence of refractive astigmatism of 1.50 D or more. CONCLUSIONS: Referring children who have at least 2.25 D of corneal astigmatism or acuity worse than 20/63 on two attempts, provides the high sensitivity and specificity associated with automated keratometry while maintaining an acuity component that can detect other causes of reduced acuity in the absence of astigmatism.
Vision Res. 2003 Apr;43(9):1081-90.
Dobson V, Miller JM, Harvey EM, Mohan KM.
Department of Ophthalmology, University of Arizona, 655 N. Alvernon, Suite 108, Tucson, AZ 85711, USA.
Best-corrected acuity was measured for vertical and horizontal gratings and for recognition acuity optotypes (Lea Symbols) in a group of three- to five-year-old children with a high prevalence of astigmatism. Results showed meridional amblyopia (MA) among children with simple/compound myopic or mixed astigmatism, due to reduced acuity for horizontal gratings. Children with simple/compound hyperopic astigmatism showed no MA, but did show reduced acuity for both grating orientations. Reduced best-corrected recognition acuity was shown by both myopic/mixed and hyperopic astigmats. These results suggest that optical correction of astigmatism should be provided prior to age three to five years, to prevent development of amblyopia.
Br J Ophthalmol. 2002 May;86(5):513-6.
Comment in: Br J Ophthalmol. 2002 May;86(5):489-90.
Becker R, Hübsch S, Gräf MH, Kaufmann H.
Department of Strabology and Neuroophthalmology, University of Giessen, Giessen, Germany.
AIMS: In order to establish normal values and interocular differences of visual acuity, Lea symbols were applied to neurologically and ophthalmologically normal children. METHODS: 385 children (21-93 months old) were examined, within a routine check up in an urban paediatric practice where Lea symbol acuity (LS) was measured. Of these children, 90 were re-examined in hospital comparing Lea symbol acuity (LS) and Landolt C acuity (LC). Strabismus, ametropia, and any organic eye disease were excluded. RESULTS: In the paediatric practice, LS could be measured on both eyes in 54% of the children. In the age group above 36 and 48 months the success rate was 76% and 95%, respectively. Acuity in the paediatric practice ranged from 0.1 to 2.0 (median 1.25) in the whole group. Interocular acuity difference was one line or less in 80%. In the hospital, LS and LC could be measured on both eyes of 77% and 48% of the 90 children, respectively. Cooperation increased with age. LS in the hospital ranged from 0.32 to 2.0 (median 1.0) and LC from 0.16 to 1.25 (median 0.8). Interocular difference of LS acuity was one line or less in 90%. CONCLUSION: Lea symbols were found to be useful for visual acuity assessment in early childhood. Significant variability of visual acuity in this age group is caused by cooperation. When monocular measurements are possible on both eyes, however, the intraindividual interocular difference of visual acuity usually does not exceed one line.
Br J Ophthalmol. 2002 May;86(5):489-90.
Comment on: Br J Ophthalmol. 2002 May;86(5):513-6.
Invest Ophthalmol Vis Sci. 2001 Apr;42(5):917-24.
Comparison of preschool vision screening methods in a population with a high prevalence of astigmatism.
Miller JM, Dobson V, Harvey EM, Sherrill DL.
Department of Ophthalmology, University of Arizona, Tucson 85711, USA.
PURPOSE: To compare the effectiveness of four methods of screening 3- to 5-year-old children for astigmatism high enough to require spectacle correction. METHODS: Lea Symbols Visual Acuity Screening (LSVAS), MTI Photoscreening (MTIPS), Nidek KM-500 Keratometry Screening (KERS), and Retinomax K-Plus Noncycloplegic Autorefraction Screening (NCARS) were attempted on 379 preschool children who are members of a Native American tribe having a high prevalence of astigmatism that is primarily corneal in origin. The need for spectacle correction was determined by cycloplegic refraction. Receiver Operating Characteristic (ROC) curves were fit, confidence intervals were determined, and area under the curves was compared. RESULTS: Astigmatism > or = 1.00 D was present in the right eye of 47.5% and in the left eye of 48.0% of children. Spectacles were prescribed for children < 48 months of age who had cylinder > or = 2.00 D and children > or = 48 months who had cylinder > or = 1.50 D, with the result that 33% of subjects required spectacles. Area under the ROC curve was 0.98 for NCARS, 0.92 for KERS, 0.78 for MTIPS, and 0.70 for LSVAS, and each of these values differed significantly from the other three (all P < 0.007). Testability was significantly higher for NCARS (99.5%) and KERS (99.7%) than for MTIPS (93.5%) and LSVAS (92.0%). CONCLUSIONS: In a population that included many children with astigmatism, objective, fully automated screening methods (NCARS and KERS) were superior to both visual acuity screening and photoscreening with subjective interpretation in identifying children who had astigmatism requiring spectacle correction.
Strabismus. 2000 Sep;8(3):209-13.
Becker RH, Hübsch SH, Gräf MH, Kaufmann H.
Department of Strabismology and Neuroophthalmology, University of Giessen, Giessen, Germany.
BACKGROUND: Lea symbols are highly sensitive for detection of amblyopia in cooperative patients. They are favorable for visual acuity assessment in childhood. Therefore, we assessed age-related normal values and interocular differences of Lea symbol visual acuity. METHODS/PATIENTS: We reexamined 50 out of 193 children aged 21 months to 7 years who came for a routine pediatric examination between January and November 1999. Lea symbol acuity (Lea Symbols Single Symbol Book (LS) and Lea 15-Line Folding Distance Chart (CLS)) and Landolt-C acuity (single (LC) and crowded with 2.6' inter-optotype distance (LC(2.6))) were measured. A three out of four criterion was used. Strabismus and any organic eye disease were excluded by orthoptic and ophthalmologic examination, consisting of biomicroscopy, ophthalmoscopy, retinoscopy or refractometry, cover test or Hirschberg test and Lang Stereotest. RESULTS: Only 26% of the parents (50 out of 193) accepted an examination in our hospital. In 35 (32) of the 50 children, visual acuity could be measured in both eyes separately with single (crowded) Lea symbols, while 26 (25) children could be examined in both eyes monocularly with the Landolt-C with single (crowded) optotypes. Except for one 3-year-old boy, all of the children older than 30 months could be tested with single Lea symbols. Lea acuity surpassed Landolt acuity. The difference was about 1.5 lines (1.5 dB) for both the single and the crowded optotypes. In 63% (69%) of the children who could be tested monocularly, LS acuity (CLS acuity) was higher than 0.8 (0.63). 89% (83%) of the children had an interocular difference of maximum 1 line for single (crowded) Lea symbols. CONCLUSIONS: The youngest child whose visual acuity could be assessed with Lea symbols was 23 months old. Almost every child older than 30 months could be tested with Lea symbols. Lea acuity higher than 1 and an interocular difference less than 2 lines is not suspect for amblyopia. Children with a difference of more than one line should be reexamined.
Ophthalmic Epidemiol. 2000 Sep;7(3):187-207.
Miller JM, Dobson VM, Harvey EM, Sherrill DL.
Department of Ophthalmology, University of Arizona, Tucson, Arizona, United States of America.
The overall goal of the AANAC study is to improve detection of astigmatism and prevention of amblyopia in populations with a high prevalence of astigmatism. To meet this goal, the study will evaluate four methods of screening for astigmatism in preschool children and will assess both the short-term and long-term benefits of early correction of astigmatism in improving acuity and preventing amblyopia. This paper presents an overview of the design and methodology of the AANAC study. Subjects are members of the Tohono O'Odham Nation, a Native American tribe with a high prevalence of astigmatism. Preschool-age children who attend Head Start are screened with four tools: the Marco Nidek KM-500 autokeratometer, the MTI photoscreener, the Nikon Retinomax K-Plus autorefractor, and the Lea Symbols acuity chart. Sensitivity and specificity for detection of significant astigmatism, as measured by a technique that uses both cycloplegic retinoscopy and cycloplegic autorefraction, is determined for each of the four screening tools. Presence of amblyopia is evaluated by measurement of best-corrected recognition acuity and acuity for orthogonal gratings. Spectacles are provided to all 3-year-old children with > or =2.00 diopters (D) of astigmatism and all 4- and 5-year-old children with > or =1.50 D of astigmatism. Persistence of amblyopia after glasses wearing is evaluated by follow-up measurement of best-corrected recognition acuity and acuity for orthogonal gratings, conducted 2-5 months after glasses are prescribed. Long-term effectiveness of early screening and glasses prescription is evaluated through measurement of recognition acuity in two groups of first-grade children: one group who participated in the Head Start program before the intensive vision screening program was initiated, and a second group who participated in the study's Head Start vision screening program.
Graefes Arch Clin Exp Ophthalmol. 2000 Jan;238(1):53-8.
Gräf MH, Becker R, Kaufmann H.
Department of Strabismology and Neuroophthalmology, University of Giessen, Friedrichstrasse 18, D-35385 Giessen Germany.
OBJECTIVE: Lea symbols can be used for measuring visual acuity in childhood. Therefore, these symbols might be useful for early detection of amblyopia. We evaluated whether the visual acuity determined with Lea symbols (LS) corresponds to the visual acuity determined with the Landolt-C (LC). PATIENTS AND METHODS: In 55 strabismic amblyopic volunteers aged 5-59 years, the monocular visual acuity of both eyes was determined using LC and LS. For comparison, the right eye of 20 healthy volunteers was examined. Single optotypes (LC, LS) were used in 55 amblyopes and crowded optotypes (LC(17.2), LC(2.6), CLS) in 40 amblyopes. The luminance of the test charts was 180-200 cd/m(2), with a contrast >85%. The refraction of the subjects was corrected beforehand. RESULTS: In the 40 amblyopic eyes tested under each condition, LS exceeded CLS and LC by about 1 line (dB), LC(17.2) by 2 lines and LC(2.6) by 3 lines (mean values +/- SD: LS 0.62+/-1.8 dB, CLS 0.46+/-1.7 dB, LC 0.5+/-2. 0 dB, LC(17.2) 0.41+/-2.3 dB, LC(2.6) 0.29+/-2.3 dB). The non-amblyopic fellow eyes and healthy eyes showed smaller differences (fellow eyes LS 1.32+/-1.1 dB, CLS 1.17+/-1.1 dB, LC 1. 15+/-0.9 dB, LC(17.2) 1.05+/-0.9 dB, LC(2.6) 0.93+/-1.1 dB; healthy eyes LS 1.74+/-0.9 dB, CLS 1.58+/-0.8 dB, LC 1.48+/-0.6 dB, LC(17.2) 1.41+/-0.7 dB, LC(2.6) 1.32+/-1.1 dB). In the amblyopic eyes, the reduction of LC was more distinct than the reduction of LS. Fifty-two amblyopes had an amblyopia >1 dB of LC, LC(17.2) and LC(2. 6), while 50 had an interocular acuity difference >1 dB CLS. CONCLUSIONS: Using Lea symbols, a recognition acuity can be determined and amblyopia can reliably be detected. Due to their design, the Lea symbols are particularly suitable and recommendable for application in young children. However a slight systematic difference between LS and LC has to be considered.
J AAPOS. 1999 Jun;3(3):160-5.
Visual acuity screening versus noncycloplegic autorefraction screening for astigmatism in Native American preschool children.
Miller JM, Harvey EM, Dobson V.
Department of Ophthalmology, University of Arizona, Tucson, USA.
INTRODUCTION: Visual acuity screening (VAS) is less reliable in preschoolers than in school-aged children as a means of detecting significant refractive error. We wished to compare the effectiveness of VAS with the effectiveness of an objective method, noncycloplegic autorefraction screening (NCARS), in detecting the presence of significant astigmatism warranting spectacle correction. METHODS: We examined 245 Native American Head Start registrants aged 3 to 5 years. We attempted to obtain uncorrected visual acuity using Lea Symbols logMAR Chart (Precision Vision Inc, Villa Park, Ill), noncycloplegic autorefraction using the Nikon Retinomax K-plus (Nikon Corp, Melville, NY), and cycloplegic refraction (CR) on each eye. The VAS failure criterion was either a 2-line acuity difference between eyes or acuity worse than 20/40 in either eye. The NCARS and CR failure criterion was the spectacle correction threshold exceeding the 50th percentile on the basis of a survey of AAPOS members. RESULTS: We completed VAS in 96% of children and NCARS and CR in 100% of children. There was high prevalence (31%) of significant astigmatic refractive error in this sample. Ten subjects who did not permit bilateral visual acuity measurements were scored as having a positive test result. The sensitivity and specificity of VAS were 90% and 44%, respectively. NCARS had sensitivity and specificity of 91% and 86%, respectively. NCARS becomes cost-effective after 1044 children are screened, assuming that the cost of the autorefractor is 300 times the cost of the referral examination. CONCLUSION: VAS offers high sensitivity but suffers from poor specificity. NCARS greatly reduces the number of unnecessary referrals. In this population, NCARS becomes cost-effective after approximately 1000 children are screened.
J Ophthalmic Nurs Technol. 1997 Mar-Apr;16(2):68-73.
Hered RW, Murphy S, Clancy M.
Nemours Children's Clinic, Jacksonville, Florida, USA.
J Pediatr Ophthalmol Strabismus. 1997 Jan-Feb;34(1):24-8.
Hered RW, Murphy S, Clancy M.
Nemours Children's Clinic, Jacksonville, FL 32207, USA.
PURPOSE: Two preliterate acuity charts, the Lea Symbol chart and the HOTV chart, were compared prospectively in an established preschool vision screening program. The charts were compared by measuring time required to test, reliability coefficients, and the percentage of children testable with each chart. METHODS AND MATERIALS: Seven hundred and seventy-seven 3- to 5-year-old children were randomized to four screening sequences that determined the order of chart use. Each child was screened on two occasions within 6 weeks. Testing was performed at 10 feet, and optotypes were not isolated for testing. RESULTS: Mean test time was significantly less for older children, but was not related to the chart used. Reliability coefficients were similar for the Lea Symbols and the HOTV charts. The percentage of children testable by each chart improved with increased age of the child. More 3 year olds were testable with the Lea Symbols chart compared to the HOTV chart (92% versus 85%, P = .05). CONCLUSIONS: Vision screening with either chart was more rapid and more frequently achieved with 4- and 5-year-old children compared with the 3 year olds. For the population as a whole, each chart gave similar results. Among the 3 year olds, however, testability rates were better for the Lea Symbols chart. The Lea Symbols chart is an acceptable option for preschool vision screening, and may be more efficacious than the HOTV chart for screening 3-year-old children.
Strabismus. 1999 Mar;7(1):1-24.
Rydberg A, Ericson B, Lennerstrand G, Jacobson L, Lindstedt E.
Department of Ophthalmology, Karolinska Institute, Huddinge University Hospital, Sweden.
The aim of the study was to assess different visual acuity tests in the age group 1 1/2-6 years in 105 children with assumed normal vision, visual impairment due to ocular disease or strabismus. Acuity tasks for young children can be divided into three subtypes according to the kind of stimulus used. For "detection acuity", the stimulus should be detected or distinguished from the background, as assessed with the Stycar Rolling Balls. For "resolution acuity", the stimulus pattern should be resolved, as assessed with the Preferential Looking procedure (Teller Acuity Cards). For "recognition acuity", the stimulus must be recognized by the subject as assessed with the BUST-D symbol test, Sheridan Gardiner (S-G) single letters, LH single symbols and line tests, and also the HVOT test. Different acuity values were obtained with regard to detection, resolution and recognition acuities. Assessment with the Stycar Rolling Balls only gave a rough estimate of the visual function. There was an overestimation of the acuity values in all groups of children when using the Preferential Looking technique. Good agreement was found between the LH line and HVOT tests. The BUST-D test, S-G single letters, and LH single symbols gave slightly better acuity values than linear recognition tests. A "crowding ratio" was calculated by dividing the single optotype acuity by the linear acuity, and also by dividing the grating acuity by the optotype linear and single acuity. The crowding ratio varied in the individual children and in the different groups, being highest for strabismic amblyopia. The general conclusion is that reliable visual acuity measurements were not obtained until the visual acuity could be assessed with a recognition test using linear letters or symbols.
Acta Ophthalmol Scand. 2005 Feb;83(1):76-80.
Is vision screening in 3-year-old children feasible? Comparison between the Lea Symbol chart and the HVOT (LM) chart.
Kvarnström G, Jakobsson P.
Division of Ophthalmology, LinkÃ¶ping University Hospital, SE-581 85 LinkÃ¶ping, Sweden.
PURPOSE: The aim of this prospective study was to compare visual screening at the age of 3 years with screening at 4 years using two different charts. METHODS: A total of 478 3-year-old children were tested at four child health care centres (CHCCs). Of these children, 440 were tested again at the age of 4 years. A third group, a control group, consisting of 229 children, was examined only at the age of 4 years. All children were tested with both the HVOT chart and the Lea Symbol chart. RESULTS: Testability rates for 3-year-olds were almost the same with the Lea Symbol chart and the HVOT chart (82.8% and 84.8%, respectively). The corresponding rates for the same children tested at 4 years of age were 96.5% and 97.0%, and for the 4-year-olds not previously tested 92.9% and 92.8%. The mean testing time was somewhat shorter for the Lea Symbol chart in all three groups, but the difference was not statistically significant. The difference in the assessment of visual acuity between the two charts was small and less than 1/10th of a line. The positive predictive value was lower at 3 years (58%) than has previously been found at 4 years (74.6%). CONCLUSION: Three-year-old children co-operate well in visual acuity testing. However, the examination time is a little longer and the testability rate is about 10% lower than at 4 years. Both 3-year-old and 4-year-old children can be tested equally well with the HVOT and the Lea Symbol charts.