Residual Amblyopia Research Articles

Randomized Trial to Evaluate Combined Patching and Atropine for Residual Amblyopia

Randomized Trial to Evaluate Combined Patching and Atropine for Residual Amblyopia

The 20 D base-in prism with headlight test as a predictor of need for future amplyopia treatment

Introduction: In orthotropic children with previous infantile and acquired esotropia, it would be useful to have a test to predict which child will need patching for residual amblyopia when they are older and able to perform on a reliable visual acuity test. A new test for predicting future need for amblyopia treatment, the 20-Diopter Base-In with Headlight Test makes use of the Hirschberg corneal reflection test generated by the headlight to determine which eye is fixing.

Cerebral venous sinus thrombosis: a diagnosis not to be missed

A 47-year-old woman was admitted with a severe headache of 5 days' duration, vomiting and collapse with transient loss of consciousness in December 2002. She had been taking black cohosh, a herbal preparation containing plant oestrogen for menopausal symptoms, for 2 years. Her father had a history of pulmonary embolism and her sister had systemic lupus erythematosus. Clinical examination was normal except for slight neck stiffness and photophobia. Brain computed tomography was normal and lumbar puncture revealed normal CSF; CSF pressure was not recorded. Her symptoms improved slowly and she was discharged home with an appointment with the neurologist arranged as an outpatient. Five days post-discharge from the hospital, she was readmitted because of the persisting headache and was found to have papilloedema on neurological examination. Chest X-ray, full blood count, erythrocyte sedimentation rate, clotting screen, urea and electrolytes, liver function tests, serum glucose, immunoglobulins, complement and autoantibody screening were normal or negative. Magnetic resonance imaging and venogram showed deep venous thrombosis in the superior sagittal sinus (Figure 1). She was anticoagulated with heparin followed by warfarin. Her headaches settled and she was discharged home 8 days later. Further investigations confirmed heterozygosity for the prothrombin gene variant (G20210A). She continued to describe ‘pressure headaches’ with tinnitus. Repeat brain magnetic resonance imaging and venogram was normal in 2004. Her headaches recurred and the diagnosis of secondary intracranial hypertension was made and acetazolamide and bendrofluazide were commenced. Further magnetic resonance imaging of the brain with venogram in September 2007 revealed a hypoplastic left transverse sinus and patent superior sagittal sinus. She was referred to the neurosurgeons and had a lumbo-thecal peritoneal shunt insertion in November 2007 with improvement in her symptoms, despite a small frontal subdural collection on brain computed tomography postoperatively, which had resolved on repeat magnetic resonance imaging in March 2008. She is regularly followed up in the neurology and ophthalmology clinics for residual bilateral papilloedema and left amblyopia and continues on ramipril, bendrofluazide and warfarin.

Pilot Study of Levodopa Dose as Treatment for Residual Amblyopia in Children Aged 8 Years to Younger Than 18 Years

Pilot Study of Levodopa Dose as Treatment for Residual Amblyopia in Children Aged 8 Years to Younger Than 18 Years

A Pilot Study of levodopa as treatment for residual amblyopia in children 8 to 17 years old

Michael X. Repka, M.D.1, Raymond T. Kraker, M.S.P.H.2, Roy W. Beck, M.D., Ph.D.2, Scott C. Atkinson, M.D.3, Darron A. Bacal, M.D.4, Don L. Bremer, M.D.5, Patricia L. Davis, M.D.6, Matthew D. Gearinger, M.D.7, Stephen R. Glaser, M.D.8, Darren L. Hoover, M.D.9, Daniel M. Laby, M.D.10, David G. Morrison, M.D.11, David L. Rogers, M.D.5, Nicholas A. Sala, D.O.12, Donny W. Suh, M.D.13, and Maynard B. Wheeler, M.D.14 for the Pediatric Eye Disease Investigator Group (PEDIG)* 1 Johns Hopkins University School of Medicine, Baltimore, MD 2 Jaeb Center for Health Research, Tampa, FL 3 St. John’s Clinic, Eye Specialists, Springfield, MO 4 Eye Physicians & Surgeons, PC, Milford CT 5 Pediatric Ophthalmology Associates, Inc., Columbus, OH 6 Progressive Eye Care, Lisle, IL 7 University of Rochester Eye Institute, Rochester, NY 8 Stephen R. Glaser, M.D., P.C., Rockville, MD 9 Everett and Hurite Ophthalmic Association, Cranberry TWP, PA 10 Daniel M. Laby, M.D., Sharon, MA 11 Vanderbilt Eye Center, Nashville, TN 12 Pediatric Ophthalmology of Erie, Erie, PA 13 Wolfe Clinic, West Des Moines, IA 14 Concord Eye Care P.C., Concord, NH

A randomized trial to evaluate combined patching and atropine for residual amblyopia

A randomized trial to evaluate combined patching and atropine for residual amblyopia

Visual Outcome in 879 Children Treated for Strabismus: Insufficient Accommodation and Vision Deprivation, Deficient Emmetropisation and Anisometropia

Purpose: To identify the effect of infant hypermetropia on residual amblyopia in children remaining after treatment.Materials and Methods: 879 strabismic children had cycloplegic retinoscopy at the age of 6 months and later when strabismus was diagnosed. A total of 26 hypermetropes consistently wore glasses from the age of 6 months, and 305 other hypermetropes had their accommodation periodically assessed by dynamic retinoscopy before strabismus was diagnosed. The relation between the last known visual acuity after treatment and all other clinical findings was analysed using t-tests and regression analysis.Results: Vision less than 6/12 in nonfixing eyes was associated with infantile hypermetropia > +5.0D, and in rare instances in excess of -3.0D of myopia. In hypermetropes only, anisometropia was associated with worse amblyopia. Astigmatism was associated with myopia and low levels of hypermetropia but not with worse vision. The vision of fixing eyes that were hypermetropic was significantly worse than that of emmetropic or myopic eyes. Wearing spectacles from the age of 6 months was associated with better vision in the nonfixing eye. Vision in the nonfixing eye of 19 hypermetropic heterotropes who started wearing glasses between 6 and 18 months of age also was better than that of those who started wearing glasses after 18 months of age. Insufficiency of accommodation was related to the degree of infantile hypermetropia, to worse vision and to failure to emmetropise. Difference in amplitude of accommodation between the eyes was largest in hypermetropes with anisometropia > +1.50 D and was marginally associated with worse vision in microtropes who became anisometropic after infancy. Hypermetropia decreased more in fixing eyes than in nonfixing eyes, thereby causing anisohypermetropia to increase after infancy. This change was most pronounced in hypermetropic microtropes. Conversely, failure of fixing eyes to emmetropise was associated with an increase in their inability to accommodate and heterotropia.Conclusions: On the basis of these findings, severe residual amblyopia in children remaining after treatment could be explained by additional vision deprivation. It can be reduced by starting spectacle correction of hypermetropia before the age of 18 months. Anisometropia seemed the result of deficient emmetropisation.

The spatial and neural deficit of human amblyopia

Abstract Purpose Human functional imaging studies confirm deficits of V1 identified from animal models and suggest additional extrastriatal areas of dysfunction. This study aims to investigate spatial visual and neural deficits in human amblyopia. Methods Participants were 6 adults (mean age=20±2 years) with amblyopia; anisometropia (n=2); mixed (n=4) and 3 normal adults (mean age=31±4 years). Cortical activation for each eye was measured using functional magnetic resonance imaging (fMRI) and psychophysical methods. Stimuli included four attributes of spatial vision known to be deficient in individuals with amblyopia: visual resolution, contrast sensitivity, vernier acuity and global motion. In each subject, retinotopic mapping experiments were also performed to establish locations of different visual areas and to act as regions of interest. All paradigms used a block design: 18 seconds stimulus ‘on’ alternated with 18s ‘control’, stimulus subtending 15x15 degrees and flickering at a temporal frequency of 8 Hz. The scans were performed on a Siemens Trio 3.0 Tesla System at Royal Holloway University. Results All participants with amblyopia had residual amblyopia following treatment. Mean logMAR visual acuity was 0.24 (sd 0.06) and ‐0.08 (sd 0.06) for amblyopic and fellow eyes respectively. Mean visual acuity for the normals was ‐0.06 (sd 0.06). Global motion was reduced significantly in the amblyopic (p=0.04) and fellow eyes (p=0.05) of observers compared to the normals; amblyopic eye: 54%(25%); fellow eye: 41%(16%); normals: 25%(7%). Conclusion Amblyopic observers show significant deficits of global motion for amblyopic and fellow eye stimulation. This is suggestive of extrastriatal deficits of amblyopia in addition to those in V1.

Treatment of capillary hemangiomas causing refractive and occlusional amblyopia

Capillary hemangiomas of the eyelid and orbit are treated when amblyopia secondary to anisometropic astigmatism or pupillary occlusion is present or when rapid growth of the hemangioma threatens to occlude the pupil. The goal of this study was to determine whether treatment of hemangiomas resolves or prevents occlusion or results in decrease in astigmatism. The records of 54 patients who underwent treatment for reduction in the size of a capillary hemangioma causing amblyopia or threatened amblyopia in two pediatric ophthalmology practices were reviewed. Twenty-eight patients were treated for amblyopia due to anisometropic astigmatism. The average amount of pretreatment astigmatism was 2.71 D, while the average amount of post-treatment astigmatism was 0.46 D. Fifteen of these patients could be tested for optotype visual acuity and all had vision acuity of 20/40 or better. Only 1 of the 15 patients treated for threatened occlusion of the pupil developed occlusion. Six of these patients cooperated with optotype visual acuity and all had vision acuity of 20/30 or better. Eleven patients were treated for pupillary occlusion. Occlusion resolved in all cases. Of the five patients treated for occlusion who cooperated with optotype visual acuity, two had a vision acuity of 20/100 or worse. Treatment to reduce the size of capillary hemangiomas results in resolution of occlusion, reduction in astigmatism, and prevention of pupillary occlusion. Those with occlusion are at higher risk for severe residual amblyopia and require prompt and definitive treatment.

Vision Screening Essentials: Screening Today for Eye Disorders in the Pediatric Patient

1. Donald H. Tingley, MD* 1. *OcuSight Eye Care Center, Rochester, NY After completing this article, readers should be able to: 1. Discuss the role of early intervention for vision-threatening problems. 2. Explain how to screen patients for the most common vision problems. 3. Recognize when to screen for vision problems. 4. Describe who should be screened for vision problems. Screening for eye disorders and vision problems is essential in preparing pediatric patients for the future. For this reason, regular vision evaluations are recommended by the American Academy of Pediatrics (AAP). Significant problems affecting vision are common in children. Vision problems occur in 5% to 10% of all preschoolers and include refractive error, strabismus, and amblyopia. Strabismus is present in 4% of preschool-age children, and amblyopia affects up to 40% of those having strabismus. Major refractive errors requiring correction occur in 5% to 7% of preschool-age children. Cataracts in children are far less common (0.1% incidence), but vision can be affected seriously without early treatment. A simple screening can check effectively for such problems during a time when treatment is most critical without requiring all patients to have a “gold standard” complete eye evaluation at every age, saving both time and health-care resources. Screening improves visual acuity. In a randomized, longitudinal study, intensive early screening led to a 60% decreased prevalence of amblyopia and improved visual acuity compared with a one-time screening at 37 months of age. (1) Amblyopia responds to therapy, and results are best when treatment is started early in life. The same study showed a 70% lower prevalence of residual amblyopia after treatment when therapy was initiated before age 3 years. The single most effective screening test for the presence of amblyopia is the determination of visual acuity via noninvasive screening. The consequences of not finding vision-related problems can include adverse effects on school and social performance as well as adult self-image. Further, …

The development of motor fusion in strabismic amblyopes using the Bangerter foil

Purpose: To examine the possibility the Bangeter foil encourages the development of motor fusion in strabismic amblyopes without motor fusion. Methods: Fifty-four consecutive amblyopes with small to moderate angle horizontal strabismus (“flick” to 20Δ), spectacles, and no motor fusion for at least 1 year previous were given a (0.1) Bangeter foil 4 hours/day to treat residual amblyopia or for maintenance. Motor fusion was tested by looking for a convergent version of the amblyopic eye in response to a 10Δ base-out prism while binocularly viewing a near target without the foil. Data on visual acuity, angle, and results of the 10Δ test were collected for a minimum of 2 years. Results: Twenty-eight of 46 patients (60%) developed motor fusion (“converters”) after a mean of 201 days. Seven patients were lost to follow-up, and one required surgery. There was no significant difference in the mean initial visual acuity in the amblyopic eye (20/40+, 20/30−) or initial horizontal angle (8.25Δ, 10.12Δ) between converters and nonconverters, respectively. There were significant differences in mean initial age (4.78 years, 5.85 years; p = 0.043) and final angle (6.14Δ, 9.25Δ; p = 0.022). There was also a significant decrease in the mean angle (−2.33Δ; p = 0.007) associated with conversion. Conclusions: Amblyopes with small to moderate horizontal angles, good initial visual acuities, and no motor fusion as measured by a 10Δ base-out test may develop motor fusion when treated with the Bangeter foil. These results are consistent with Parks’ 4 to 8Δ rule and further suggest there may be a mechanism for realignment.

Anisometropic Amblyopia Treated with Spectacle Correction Alone: Possible Factors Predicting Success and Time to Start Patching

To evaluate factors predicting resolution of amblyopia and the time course of improvement in VA in children 3 to 7 years old with anisometropic amblyopia treated with spectacles alone. Prospective, noncomparative intervention. Measurement of corrected amblyopic logMAR visual acuity (VA) in newly diagnosed children at four-weekly intervals until VA stabilized or amblyopia resolved. The time course of improvement in VA and the factors related to amblyopia resolution were assessed. Sixty children with a mean age of 5.3 years and mean anisometropia of 2.95 diopters (D) were included. Amblyopia improved by 2 or more logMAR lines in 56 patients (93%) and resolved in 27 patients (45%), with a mean improvement in VA of 0.38 logMAR. The improvement in VA in the amblyopic eye was considerable at four to 12 weeks then reached a plateau, after which it improved only slowly. Resolution of amblyopia was related to better initial VA (0.2 to 0.6 logMAR) and lesser amounts of anisometropia (<4 D). The time to resolution ranged from four to 40 weeks, but no patient with residual amblyopia showed an improvement in VA of more than 0.1 logMAR over four consecutive visits. With spectacle correction alone, 3- to 7-year-old children with previously untreated anisometropic amblyopia achieved approximately four-line improvement and resolved nearly in half. The nearly two-month plateau periods during improvement of VA should be noticed. After four months with no improvement in VA, occlusion therapy or atropine penalization may be considered.

The VF-14 and Psychological Impact of Amblyopia and Strabismus

To assess the impact of amblyopia, strabismus and glasses on subjective visual and psychological function among amblyopes. Questionnaires were administered to 120 teenagers with amblyopia (cases), with residual amblyopia after treatment, or with or without strabismus and 120 control subjects (controls) Cases underwent ophthalmic examination including cycloplegic refraction. Two questionnaires (visual function 14 [VF-14] and a newly designed eight-item questionnaire) were administered to assess the psychological impact score of general daily life, having a weaker eye, glasses wear, and current noticeable strabismus. Questionnaires were validated in 60 subjects in each group by a second administration of the questionnaire. The VF-14 scores, psychological impact scores, and clinical data were compared. The VF-14 and psychological impact scores were highly reproducible. The mean VF-14 score for the control group was 95.5 and for the cases was 78.9 (P < 0.0001), but the scores did not correlate with the severity of amblyopia. The psychological impact score in general daily life was sensitive in discriminating between mild (median score 31) and moderate to severe (median score 56) amblyopes (P < 0.02). The cases segregated into two clear groups; those who scored high (large detrimental psychological impact) on psychological impact, with subjectively noticeable manifest strabismus, and those who scored low (low detrimental psychological impact), without noticeable strabismus. The subjective experience of patching treatment differentiated the two groups best of all. Subjective visual and psychological functions are altered compared with normal subjects due to amblyopia, strabismus, and a previous unpleasant patching experience. The mean VF-14 score was similar to that previously published for patients with glaucoma. The study underlines that amblyopia and/or strabismus have an impact on teenagers' subjective visual function and well-being.

Does Treatment of Capillary Hemangiomas for Amblyogenic Factors Result in a Resolution of the Amblyogenic Factors?

Factors Result in a Resolution of the Amblyogenic Factors? Shirah R. Schwartz, MD, Francine Blei, MD, Emily Ceisler, MD, Mark Steele, MD, Louis Furlan, MD, Sylvia R. Kodsi, MD; North Shore–Long Island Jewish Health System, Great Neck, NY Introduction: Treatment of capillary hemangiomas is initiated when there is amblyogenic anisometropic astigmatism, when there is pupillary occlusion, or when rapid growth of the hemangioma threatens to occlude the pupil. The goal of this study was to determine whether treatment of hemangiomas results in resolution or prevention of occlusion or decrease of astigmatism. Methods: The records of 55 patients who underwent treatment for reduction in size of a capillary hemangioma in two pediatric ophthalmology practices were reviewed. Indication for treatment, age at first visit, cycloplegic refraction at the initial and final visits, type of treatment, need for patching or spectacles, and final visual acuity were recorded. Results: This is the largest case series of children with capillary hemangiomas with recorded pretreatment and posttreatment cycloplegic refraction who were followed through the duration of treatment. Twelve patients were treated for pupillary occlusion. Occlusion resolved in all cases. Of the six patients with a final measurable visual acuity (FMVA), two had a vision of 20/100 or worse. Thirty patients were treated for anisometropic astigmatism. The average amount of pretreatment astigmatism was 2.68 D, while the average amount of posttreatment astigmatism was 0.53 D. All 15 patients with an FMVA had a vision of 20/40 or better. The 13 patients treated for threatened occlusion of the visual axis did not develop occlusion. The six patients with a FMVA all had vision of 20/30 or better. Conclusion: Treatment to reduce the size of capillary hemangiomas results in resolution of occlusion, reduction in astigmatism, and prevention of pupillary occlusion. Those with occlusion are at higher risk for severe residual amblyopia and require more aggressive treatment.

The Treatment of Amblyopia

Recent studies suggest that children with amblyopia associated with anisometropia, strabismus, or both should be treated initially with best refractive correction until visual acuity is stable. This may take several months, and a proportion of children will achieve equal visual acuity with glasses alone. For residual anisometropic and strabismic amblyopia, the initial choice of patching or atropine should involve the parent and the child. The dose of prescribed patching or atropine may initially be quite modest, such as 2 hours of patching a day or twice weekly atropine. Treatment should be offered to children until at least 12 years of age and possibly to teenagers. Ongoing studies are addressing the role of undertaking near activities while patched and the role of atropine for severe amblyopia and for older amblyopic children. Future studies are needed to investigate the best treatment strategies for residual amblyopia, whether weaning treatment is needed at the end of a course, and how compliance can be enhanced.

Treatment of Unilateral Amblyopia: Factors Influencing Visual Outcome

To identify factors that influence the outcome of treatment for unilateral amblyopia, as a part of the Monitored Occlusion Treatment of Amblyopia Study (MOTAS). This was an intervention study consisting of three nonoverlapping phases: "Baseline", "refractive adaptation" (18 weeks of full-time spectacle wear), and "occlusion" (6 hours of patching per day, objectively monitored). Condition factors: type of amblyopia, age of participant, initial severity of amblyopia, fixation, and binocular vision status; treatment factors: refractive adaptation and occlusion (total dose [hours] and dose rate [hours per day]) were assessed for their influence on visual outcome. Visual outcome was expressed in three ways: logMAR (logarithm of the minimum angle of resolution) change, residual amblyopia, and proportion of the deficit corrected. The study included 85 participants (mean age, 5.1 +/- 1.4 years) with amblyopia associated with strabismus (n = 32) or anisometropia (n = 20) or associated with both anisometropia and strabismus (n = 33). Treatment factors: cumulative occlusion dose exceeding 50 hours, and dose rates > or =1 hour per day resulted in (P < or = 0.01) lower residual amblyopia and a greater proportion of the deficit corrected. Condition factors associated with poor outcome (high residual amblyopia) were presence of eccentric fixation, severe initial amblyopia, and no binocular vision. Factors influencing outcome with treatment for amblyopia are occlusion dose (the rate of delivery and cumulative dose worn), the initial severity of the amblyopia, binocular vision status, fixation of the amblyopic eye, and the age of the subject at the start of treatment.

Prevalence and Outcomes of Childhood Visual Disorders

Purpose: This population-based study examines the prevalence of childhood visual disorders: amblyopia (strabismus, refractive errors) and organic disease. It also assesses treatment outcomes, visual impairment and residual amblyopia. Methods: 1582 children were retrospectively analysed on treatment completion (age 8-9 years). Significant visual disorders included: esotropia, exotropia, anisometropia (hyperopia ≥1.50DS, astigmatism ≥1.00DC, myopia ≥1.50DS), ametropia (hyperopia ≥1.50DS, astigmatism ≥1.0DC, myopia ≥0.75DS) and organic defects. Results: 198 children (12.5%) had a significant visual disorder: strabismus (3.98%), eso:exo rate 5:1, anisometropia (2.34%), ametropia (5.82%), organic defects (0.38%). Organic disease caused visual handicap (< 6/18 in better eye) in 0.13%. Amblyopic visual impairment (6/18; 6/24-6/60) occurred in 1.13%; 2.02% had residual amblyopia (6/12 or worse). Conclusions: Childhood visual disorders are a common problem. Unfavourable visual outcomes in esotropia are related to two sub-groups and particularly with poor concordance to treatment. Suggested strategies to improve outcomes include health promotion, an “Amblyopia Nurse” and a “Patch Club”.

Visual acuity, residual amblyopia and ocular pathology in a screened population of 12-13-year-old children in Sweden.

To establish the distribution of visual acuity and the prevalence of residual amblyopia and other ocular disorders in a vision-screened population group of 12-13-year-old children. In total 1046 children were examined in a field study in Sweden. The examination included visual acuity, stereopsis, cover testing, red reflex, refractive retinoscopy and examination of the posterior pole. In selected cases VEP was also performed. Visual acuity > or =1.0 in at least one eye was present in 98% of cases. Residual amblyopia (< or =0.5) was found in 1.1% of the population. Manifest strabismus was found in 2.7%. There were only a small number of ocular opacities and posterior pole abnormalities. Ocular albinism was found in 7 cases. In 15 children the cause of subnormal VA was unexplained. Results for visual acuity, residual amblyopia and other ocular disorders are very similar to previous Nordic, vision-screened populations.

Subnormal visual acuity syndromes (SVAS): albinism in Swedish 12-13-year-old children.

The vision of 12-13-year-olds in Sweden was examined in a field study. The study was designed as being a part of a large European-Latin American study, the DESAMI project. The objective was to evaluate the prevalence of residual amblyopia and ocular disorders, atiologies of subnormal vision and some normal visual parameters in this group of children. The children had to be born in Sweden in 1985 in order to have the opportunity to be included in the voluntary screening visual examinations. The full results of the study will be presented elsewhere. This paper presents clinical and VEP data of those children who had visual acuity of 0.8 or below in one or both eyes which could not be increased with glasses, or other visual/eye disturbances not explained as common amblyopia, i.e., subnormal visual acuity or pathological visual states of unknown cause, SVAS (subnormal visual acuity syndromes). In all, 1046 children were examined: 76 had visual disturbances of such severity that they were referred to a paediatric ophthalmologist (AS). Eighteen children could not be pathologically classified, and they were referred to another ophthalmological examination and VEP (visual evoked potential) recordings. VEP reveals an asymmetric response after monocular stimulation in albinism. Twelve children turned up for a second examination and VEP was recorded from 10 children. Nine children showed iris translucency. Seven children showed an asymmetric VEP and were classified as albinos. The albinoic VEPs could be subdivided into two types, (1) including all parts of the response and (2) partly excluding the P1/P100 potential complex. The VEP response was normal, showing symmetry and no other abnormality, in three of the children. The results indicate that albinism is common in Sweden. A prevalence value of approximately 1% is about 100 times higher than previous figures. This high prevalence may indicate another form of heredity, with genetical contribution to albinism from a varying number of albino genes and varying expression in the phenotypes, in the Scandinavian population. It is emphasised that in investigations of children with SVAS, electrophysiological examinations are important, not only to reveal albinism but also to exclude or verify neurometabolic conditions, for example.

Preschool vision screening: outcome of children referred to the hospital eye service.

To assess the outcome of children referred to the hospital eye service (HES) from an orthoptist based preschool vision screening programme. A retrospective study was conducted of children referred from screening during a 2 year period. Children were screened by community orthoptists at 3 1/2 years of age. The main outcome measures were (1) HES findings for children referred from screening, and (2) visual outcome for amblyopic children after completion of treatment. The attendance rate at screening was 79.3% (6794 children): 348 children (5.1% of those screened) were referred to the HES. The HES findings were refractive error (32.9%), amblyopia (29.9%), false positive referral (20.1%), strabismus (13.2%), and other ocular disorders (3.9%). The positive predictive value of screening was 79.9%. Screening detected 48 children with straight eyed amblyopia and 43 children with strabismic amblyopia. A visual acuity of 6/9 or better in the amblyopic eye was achieved by 87.2% of straight eyed amblyopes and 64.3% of strabismic amblyopes (chi 2 = 5.27, p = 0.02). Residual amblyopia of 6/24 or worse occurred in only 5.6% of amblyopic children. Most amblyopic children detected by preschool vision screening achieve a good visual outcome with treatment. While treatment earlier in the sensitive period might be expected to give improved results, it remains to be demonstrated that preschool screening results in a better outcome than screening at school entry. Preschool vision screening also detects a significant number of children without amblyopia who have reduced vision due to refractive errors. This group of children must be included in any analysis of the cost effectiveness of preschool vision screening.