Astigmatism and Amblyopia among Native American Children (AANAC): design and methods

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.

Preliminary report: examination of young children with Lea symbols

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.

Screening for amblyopia in preverbal children with photoscreening photographs. III. improved grading criteria for hyperopia

OBJECTIVE

To examine the ability of the Medical Technology and Innovations (MTI), Inc., Photoscreener (Cedar Falls, IA) to detect hyperopia and to improve the photograph grading criteria to screen for amblyopiogenic levels of hyperopia.

DESIGN

Cross-sectional study and reanalysis. PARTICIPANTS AND TESTING: In previous work, 392 participants received a complete ophthalmologic examination and were photographed using the MTI Photoscreener. For this study, all 209 participants with normal examination findings (65 children) or hyperopia without anisometropia (144 children) were selected. The data were reanalyzed using modified photograph grading and ophthalmologic examination failure criteria. Potential reasons for why many children with hyperopia passed photoscreening were explored.

MAIN OUTCOME MEASURES

We determined whether a study participant would pass or fail screening with a given photograph grading and ophthalmologic examination failure criteria.

RESULTS

Most children with hyperopia of +2.00 to +3.50 diopters (D) passed screening with the MTI instrument, in most cases because their photographs lacked bright crescents. When bright crescents in at least two of the four possible meridians were the grading guideline for screening failure and the pediatric ophthalmologists' consensus hyperopia failure criteria (> +3.50 D) were adopted, the sensitivity for hyperopia detection was 100% and the specificity was 88%. Identical results were obtained using the American Academy of Ophthalmology Preferred Practice Pattern hyperopia failure criteria (>/= +4.50 D).

CONCLUSIONS

The MTI photograph grading guidelines can be simplified, and the ophthalmologic examination failure criteria for hyperopia can be improved. The presence of a bright crescent in the lower or the left pupillary margin indicate hyperopia in an amblyopiogenic range (> +3.50 D).

Screening for amblyopia in preverbal children with photoscreening photographs: II. Sensitivity and specificity of the MTI photoscreener

OBJECTIVE

To determine the sensitivity and specificity of vision screening using the Medical Technology and Innovations (MTI), Inc., PhotoScreener.

DESIGN

Cross-sectional study. PARTICIPANTS AND TESTING: Three hundred ninety-two children less than 4 years of age received a complete ophthalmologic examination and were photographed using the MTI PhotoScreener. One hundred three children had normal examinations, and the remaining 284 children had conditions of interest for pediatric screening: ptosis, media opacity, refractive error, or strabismus. Five children were excluded.

MAIN OUTCOME MEASURES

The grading of the photographs by the manufacturer's representative was compared with the results of the ophthalmologic examinations. Sensitivity and specificity of vision screening were determined.

RESULTS

The analysis of all informative photographs resulted in a sensitivity of 65% and a specificity of 87%. The sensitivity of detection for children with some forms of strabismus was high, up to 95% for esotropia of 10Delta or more. Sensitivities for the detection of ptosis, media opacity, and refractive error were poor in patients where strabismus was not also present.

CONCLUSIONS

The MTI PhotoScreener may play a role in preverbal vision screening; identification of two of three children with amblyopiogenic factors before age 4 would be an exciting advance in public health. However, improvement in the ability to identify children with media opacity and refractive error is necessary. Improvements may be possible with modifications of the examination failure and photograph grading criteria.

Screening for amblyogenic factors using a volunteer lay network and the MTI photoscreener. Initial results from 15,000 preschool children in a statewide effort

PURPOSE

To describe the results from a statewide preschool vision screening program using the MTI PhotoScreener (Medical Technology and Innovations, Inc., Cedar Falls, IA).

DESIGN

Cross-sectional study.

PARTICIPANTS

A total of 15,059 children aged 6 to 47 months enrolled in childcare and preschool settings throughout the state of Tennessee.

METHODS

Volunteers from local Lions Clubs took photoscreening photographs of children in a statewide effort. Photographs were interpreted at the Vanderbilt Ophthalmic Photography Reading Center using predetermined criteria. Children who failed the screening were referred to community ophthalmologists or optometrists who performed a comprehensive evaluation and forwarded the results to the authors.

MAIN OUTCOME MEASURES

Referral rate, unreadable rate, and predictive value positive (PVP).

RESULTS

During the 2 years of the screening program, 15,059 children were screened in 850 screenings. The screening referred 1013 children (6.7%), and 704 photographs (4.7%) were unreadable. Children who failed the screening had a significant abnormality (strabismus, anisometropia, high hypermetropia, high astigmatism, or high myopia) in 320 of the 531 cases where adequate follow-up results were reported. The PVP ranged from 84% when a diagnosis of strabismus was suggested by the photoscreen reading to 41% for astigmatism. Despite intense attention to follow-up, many children who failed the screening never received a formal eye examination.

CONCLUSIONS

The MTI PhotoScreener can be used by volunteers to screen preschool children and can have a high PVP in organized settings, provided that meticulous attention is paid to photograph interpretation and quality control. The PVP of the MTI PhotoScreener depends on the diagnosis suggested when the photograph is read. Significant obstacles exist in obtaining care for those who fail screening.

Long term follow up of premature infants: detection of strabismus, amblyopia, and refractive errors

AIM

To establish recommendations for long term ophthalmological follow up of prematurely born infants.

METHODS

130 infants with a gestational age (GA) <37 weeks and born between 1 November 1989 and 31 October 1990 were enrolled in a prospective study about the development of strabismus, amblyopia, and refractive errors. Infants were subdivided in three groups according to GA: A <28 weeks (n=32), B >/=28-</=32 weeks (n=64), C >32-<37 weeks (n=34). Ophthalmological assessment took place at the postconceptional age of 32 weeks, at term and at 3, 6, 12, and 30 months post term. At the age of 5 years parents received a questionnaire and a majority of the children was examined again (n=99).

RESULTS

At the age of 5 years 46 infants were known to have strabismus (n=29) and/or amblyopia (n=22) and/or refractive errors (n=22). Statistical analysis showed that gestational age, duration of supplementary oxygen, and duration of hospitalisation were important predictive variables for the development of strabismus, amblyopia, or refractive errors (SAR) at the age of 5 years (p<0.05). Infants with a GA </=32 weeks had a significantly higher risk of developing SAR than infants with a GA >32 weeks, who developed an incidence comparable with the normal population. Strabismus developed mainly in the first year of life and at the age of 5 years. Most infants with amblyopia were detected at the age of 2-3 years. Refractive errors were found in the first year of life and at the age of 2.5 and 5 years.

CONCLUSION

Infants with a GA <32 weeks should be selected for long term ophthalmological follow up. These infants should be screened at the age of 1 year, in the third year of life (preferably at 30 months), and just before school age (including testing of visual acuity with optotypes).

A new test of contour integration deficits in patients with a history of disrupted binocular experience during visual development

Previous studies have suggested that the integration of orientation information across space is impaired in amblyopia. We developed a method for quantifying orientation-domain processing using a test format that is suitable for clinical application. The test comprises a graded series of cards where each card includes a closed path (contour) of high contrast Gabor signals embedded in a random background of Gabor signals. Contour visibility in both normals and patients with histories of abnormal binocular vision depends jointly on the spacing of elements on the contour as well as background element density. Strabismic amblyopes show significant degradation of performance compared to normals. Small but significant losses in sensitivity were also observed in a group of non-amblyopic strabismus patients. Threshold measurements made with contrast reducing diffusers indicated that the amblyopic loss is not due to the reduced contrast sensitivity of the amblyopic eye. An abnormal pattern of long-range connectivity between spatial filters or a loss of such connectivity appears to be the primary source of contour integration deficits in amblyopia and strabismus.

Early screening for amblyogenic risk factors lowers the prevalence and severity of amblyopia

PURPOSE

To evaluate the efficacy of a mass screening program for amblyopia and amblyogenic risk factors in infants.

METHODS

Since 1968, children between the ages of 1 and 2(1/2) years in the city of Haifa, Israel, have been systematically screened for amblyopia and amblyogenic risk factors. The screening is performed by the Ophthalmology Department of Bnai-Zion Medical Center (formerly known as Rothchild Hospital). In 1995, we compared the prevalence and severity of amblyopia in two populations of 8-year-old children in elementary school: one group was a cohort of 808 children from the city of Haifa and its vicinity, who had been screened in infancy (between 1988 and 1990); and the second group, the control group, was a cohort of 782 children from Hadera and its vicinity, where this early screening program is not conducted. Amblyopia was defined as corrected visual acuity of < or =5/10 (20/40), or >1 line difference in corrected visual acuity between the two eyes. Referral rate, treatment rate, sensitivity, specificity, and positive predictive value and negative predictive value of the screening test in detecting factors that later resulted in the development of amblyopia were examined.

RESULTS

The prevalence of amblyopia in the 8-year-old population screened in infancy was found to be 1.0% compared with 2.6% in the 8-year-old population that had not been screened in infancy (P =.0098). The prevalence of amblyopia with visual acuity of < or =5/15 (20/60) in the amblyopic eye was 0.1% in the screened population compared with 1.7% in the non-screened population (P =.00026). In the screened infant population, 3.6% were referred from the screening examination to a confirmatory examination and 2.2% were treated. The screening examination had a sensitivity of 85.7% and a specificity of 98.6% for amblyopia. The positive predictive value of the screening examination was 62.1% and the negative predictive value was 99.6%.

CONCLUSIONS

The screening program for amblyopia and amblyogenic risk factors in infants, followed by appropriate treatment, is effective in significantly reducing the prevalence and severity of amblyopia in children.

Evaluation of the iScreen digital screening system for amblyogenic factors

BACKGROUND

A digital photoscreener, the iScreen screening system, is now available to detect amblyogenic factors. We carried out a prospective study to evaluate the accuracy of the device in detecting anisometropia, significant refractive error, strabismus and opacities of the ocular media.

METHODS

A total of 449 consecutive patients (median age 7 years) from a private pediatric ophthalmology practice underwent screening with the iScreen photoscreener operated by a minimally trained technician. The results were compared to the masked clinical examination of a pediatric ophthalmologist.

RESULTS

The iScreen device had a sensitivity of 92.4%, specificity of 89.1%, positive predictive value of 94.1% and false-negative rate of 13.8%. Of the 21 patients with a false-negative result, 12 had myopia of less than -1.50 dioptres. High hyperopia was missed in two patients, high astigmatism in one, unequal cylindrical error in one and strabismus in five.

INTERPRETATION

The iScreen digital photoscreener produced accurate and timely screening for potentially amblyogenic defects in the study population.

The Alaska Blind Child Discovery project: rationale, methods and results of 4000 screenings

BACKGROUND

Photoscreening allows lay persons to adapt the Enhanced Brückner Test to preschoolers in an attempt to identify refractive amblyopia. The Alaska Blind Child Discovery (ABCD) project is charitably funded and administered.

METHODS

MTI photoscreening was offered to children in rural and urban communities in southern Alaska from 1996 through June 1999. Parents answered questions concerning the child's health, family ocular history and whether the child had any eye "Warning Signs." The MTI images were interpreted by two eye doctors using a modification in MTI published guidelines.

RESULTS

Out of 4000 screenings performed on 3930 children, there was an overall "not normal" interpretation of 9% and an inconclusive rate of 1%. The mean S.D. age was 3.9 2 years. Only 6% had had a prior eye exam. The average number of Polaroid pictures per screening was 1.16. Follow-up data on "not normal" results was obtained on just over 50%. The positive predictive value during the first two years was 77% but improved to 92% from 1998-1999. Affirmative answers to the questions concerning previous eye exam, child's health, siblings eye health and positive "Warning Signs" were significantly associated with "not normal" interpretations but affirmative answers about eye health of mother, father and relatives were not. Community penetrance of photoscreening to the target age-group ranged from only 5% for Anchorage to almost 100% for the Bristol Bay public health nurses. Five percent of parents of "positive" results surveyed would not have recommended screening for their friends. Equipment functioned dependably even in remote Alaska.

CONCLUSION

Charitable volunteer Polaroid photoscreening detected amblyopia and significant pediatric eye disease in over 300 children during the first 3.5 years of ABCD.

Cost-effectiveness of orthoptic screening in kindergarten: a decision-analytic model

PURPOSE

The purpose of this study was to analyze the cost-effectiveness of orthoptic screening for amblyopia in kindergarten.

METHODS

A decision-analytic model was used. In this model all kindergarten children in Germany aged 3 years were examined by an orthoptist. Children with positive screening results were referred to an ophthalmologist for diagnosis. The number of newly diagnosed cases of amblyopia, amblyogenic non-obvious strabismus and amblyogenic refractive errors was used as the measure of effectiveness. Direct costs were measured form a third-party payer perspective. Data for model parameters were obtained from the literature and from own measurements in kindergartens. A base analysis was performed using median parameter values. The influence of uncertain parameters was tested in sensitivity analyses.

RESULTS

According to the base analysis, the cost of one orthoptic screening test was 7.87 euro. One ophthalmologic examination cost 36.40 euro. The total cost of the screening program in all kindergartens was 3.1 million euro. A total of 4,261 new cases would be detected. The cost-effectiveness ratio was 727 euro per case detected. Sensitivity analysis showed considerable influence of the prevalence rate of target conditions and of the specificity of the orthopic examination on the cost-effectiveness ratio.

CONCLUSIONS

This analysis provides information which is useful for discussion about the implementation of orthoptic screening and for planning a field study.

[A study of the visual acuity and amblyopia in infants aged 3 to 5 from El Hierro island]

PURPOSE

To discover the prevalence of visual alterations in a static child population, like that of El Hierro island, and to evaluate the efficacy of having infant teachers carrying out visual screening in infants.

METHODS

Infant teachers tested the visual acuity of children between 3 and 5 years of age, and referred those who did not reach a previously established visual level to the Ophthalmology Department of the island's Hospital. There, a complete ophthalmological study was undertaken. Subsequently, a group of children that the teachers considered normal was also checked.

RESULTS

Of the 240 children between 3 and 5 years of age who live on the island, 205 had the visual acuity tested by teachers. It was found that 21 did not achieve the desired visual level for their age. Of these, 9 were truly pathological (6 of them were amblyopes). The other 12 were normal, ophthalmologically speaking. Of the 184 children which the teachers considered normal, 81 were studied in the ophthalmology department. Two children were found to be pathological (2.5% of false negatives), both being slightly myopic. The degree of correlation between the visual acuity taken by the teachers and by the ophthalmologists was r=0.6 and the mean difference was 0.07.

CONCLUSIONS

We believe that infant teachers are a good choice for initial screening of visual abnormalities in infancy. Strategies are being discussed to diminish the high rate of false positives

Improving the reliability of visual acuity measures in young children

Whilst the methodology of adult letter acuity measurement has been substantially refined over the last two decades, relatively little development has occurred in methods for quantifying letter acuity in young children. This study compares a recently developed visual acuity test (Glasgow Acuity Cards), which incorporates several key design features used in adult test charts to improve the sensitivity and reliability of visual acuity measurements. The equivalence of acuity measurements made with Glasgow Acuity Cards were compared with the Bailey-Lovie logMAR chart and Snellen chart in adults, and with traditional Single Letter Acuity and a modified Single Letter Acuity test in children. The test-retest reliability of acuity measurements made with Glasgow Acuity Cards and the Single Letter Acuity tests were also assessed in a large group of visually normal children. In addition, the ability of the pre-school letter acuity tests to detect differences in acuity between the two eyes, and to detect amblyopia were examined. Ninety-five percent of vision measurements made with the Bailey-Lovie chart and Glasgow Acuity Cards differ by less than 0.07 log unit. Furthermore, the sensitivity of Glasgow Acuity Cards to detecting changes in acuity longitudinally and inter-ocular differences in acuity is considerably greater as compared with traditional Single Letter Acuity tests. Improvements in paediatric acuity chart design are important for the effective detection and management of children with amblyopia.

[Cost effectiveness of mass orthoptic screening in kindergarten for early detection of developmental vision disorders]

PURPOSE

Orthoptic screening in the kindergarten is one option to improve early detection of amblyopia in children aged 3 years. The purpose of this study was to analyse the cost-effectiveness of such a screening programme in Germany.

METHODS

Based on data from the literature and own experience gained from orthoptic screening in kindergarten a decision-analytic model was developed. According to the model, all children in kindergarten, aged 3 years, who had not been treated for amblyopia before, were subjected to an orthoptic examination. Non-cooperative children were reexamined in kindergarten after one year. Children with positive test results were examined by an ophthalmologist for diagnosis. Effects were measured by the number of newly diagnosed cases of amblyopia, non-obvious strabismus and amblyogenic refractive errors. Direct costs were estimated from a third-party payer perspective. The influence of uncertain model parameters was tested by sensitivity analysis.

RESULTS

In the base analysis the cost per orthoptic screening test was DM 15.39. Examination by an ophthalmologist cost DM 71.20. The total cost of the screening programme in all German kindergartens was DM 6.1 million. With a 1.5% age-specific prevalence of undiagnosed cases, a sensitivity of 95% and a specificity of 98%, a total of 4,261 new cases would be detected. The cost-effectiveness ratio was DM 1,421 per case detected. Sensitivity analysis showed considerable influence of prevalence and specificity on the cost-effectiveness ratio. It was more cost-effective to re-screen non-cooperative children in kindergarten than to have them examined by an ophthalmologist straight-away.

CONCLUSIONS

The decision-analytic model showed stable results which may serve as a basis for discussion on the implementation of orthoptic screening and for planning a field study.

Prevalence of amblyopia among defaulters of preschool vision screening

The prevalence of amblyopia among screening defaulters is an important determinant of the efficacy of amblyopia detection by preschool vision screening. A retrospective cohort study was therefore performed to assess an orthoptist-based preschool vision screening programme. The preschool vision screening status of children in the cohort was determined by reviewing their Community Child Health records. The prevalence of amblyopia among screening defaulters was determined by reviewing each child's school entry vision test (performed at 5.5 years of age), with retesting if a Snellen line acuity of 6/6 in each eye had not been documented. For comparison, the prevalence of amblyopia among screening attenders was also determined. The preschool vision screening status was known for 86.0% (772/898) of the cohort. The attendance rate at preschool vision screening was 79.2%. The prevalence of amblyopia among screening defaulters was 1.3% (95% CI 0.2% to 4.5%). The prevalence of amblyopia among screening attenders was 2.5% (95% CI 1.4% to 4.1%). There was no significant difference in the prevalence of amblyopia between screening defaulters and screening attenders (P=0.53). The efficacy of amblyopia detection by preschool vision screening is therefore highly dependent on its attendance rate. Preschool vision screening programmes with a low attendance rate will fail to detect a significant proportion of children with amblyopia.

Photoscreening for amblyogenic factors by public health personnel: the Eyecor Camera System

OBJECTIVES

This pilot study was designed to assess the ability of a photoscreening camera to detect amblyogenic factors such as high refractive error, anisometropia, media opacities and strabismus in children, compared to the standard vision screening techniques employed by the local state public health screening personnel.

METHODS

Public health personnel in Illinois used the Eyecor prototype to the current commercially available MTI PS-100 photoscreening camera (manufactured by Medical Technology Inc.) to screen 127 non-dilated subjects, ages 7 months to 20 years (mean age, 6 years), for amblyogenic factors. All participants were concurrently subjected to the "standard" vision screening employed routinely by state public health personnel. The study participants included a group of normal inner-city children and one group of special-needs children. The normal children came from both a public school and a private school. The special-needs children included a group of children from a state-run school for the deaf and hard-of-hearing and a separate group of children attending a multi-disciplinary Easter Seals clinic.

RESULTS

In the population of normal children, the mean sensitivity and specificity for the observers using the Eyecor Camera system was 81% and 83% with a mean positive predictive value of 83%, and a mean negative predictive value of 55%. Standard vision screening techniques employed by public health service certified vision screeners had a sensitivity of 88%, a specificity of 91%, a positive predictive value of 67% and a negative predictive value of 97% in the same subjects. In the population of special-needs children with hearing impairment and developmental delay, the mean sensitivity and specificity for the observers using the Eyecor Camera system was 74% and 82% with a mean positive predictive value of 69% and a mean negative predictive value of 85%. Standard vision screening techniques employed by public health service certified vision screeners had a sensitivity of 100%, a specificity of 55%, a positive predictive value of 62% and a negative predictive value of 100% in the same subjects. (See Table 1)

CONCLUSIONS

This study shows that the Eyecor Photoscreening Camera is useful in screening normal children for amblyogenic factors. Photoscreening was at least as effective as standard screening methodologies performed by certified vision screeners as required by state public health policy. In addition, photoscreening is particularly useful in testing those children "unscreenable" by conventional vision screening procedures.

Binocular fixation pattern and visual acuity in children with strabismic amblyopia

BACKGROUND

A prospective study was undertaken to compare the binocular fixation pattern and presence of amblyopia in strabismic children.

METHODS

Fifty-three children with manifest strabismus and the ability to cooperate with an optotype acuity test were examined. The binocular fixation pattern and logMAR visual acuity were recorded by separate, masked observers under standardized conditions. The binocular fixation pattern was divided into four grades from alternation to uniocular fixation.

RESULTS

Patients who freely alternated did not have amblyopia, while those who maintained or preferred fixation with a given eye tended to have amblyopia in the nonpreferred eye.

CONCLUSION

The binocular fixation pattern can be rapidly assessed with minimal equipment and training. These findings confirm the usefulness of a graded assessment of the binocular fixation pattern in the detection of amblyopia.

Lea symbols: visual acuity assessment and detection of amblyopia

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.

Congenital trigeminal anesthesia in two siblings and their long-term follow-up

PURPOSE

To alert ophthalmologists to congenital trigeminal anesthesia as a cause of corneal scarring and amblyopia and its effective treatment with tarsorrhaphies.

METHODS

Case reports. A 2-month-old infant presented with bilateral corneal erosions and complete corneal anesthesia. Her sister presented at age 3 years with a corneal ulcer and corneal hypoesthesia (sensation markedly decreased). The father and paternal grandmother of the siblings also had corneal hypoesthesia.

RESULTS

Further investigation of the infant revealed bilateral hearing loss, swallowing difficulties, and decreased sensation in the trigeminal nerve distribution. A diagnosis of congenital trigeminal anesthesia was made. The corneal erosions of the patient resolved with bilateral two-thirds width tarsorrhaphies. The girl continues to do well now at 10 years of age with ocular lubrication and superficial corneal scar removal. Her older sister initially required antibiotic ointment for her corneal ulcer but now requires only ocular lubrication for congenital trigeminal anesthesia.

CONCLUSION

This study describes the earliest reported use of tarsorrhaphies in an infant with congenital trigeminal anesthesia. The presence of this condition in her sister and relatives makes it one of the few reports of congenital trigeminal anesthesia in more than two generations. Early recognition of this condition is essential in the preservation of useful vision.