Factors affecting long term results of successfully treated amblyopia: initial visual acuity and type of amblyopia

Human deprivation amblyopia: treatment insights from animal models

Amblyopia is a common visual impairment that develops during the early years of postnatal life. It emerges as a sequela to eye misalignment, an imbalanced refractive state, or obstruction to form vision. All of these conditions prevent normal vision and derail the typical development of neural connections within the visual system. Among the subtypes of amblyopia, the most debilitating and recalcitrant to treatment is deprivation amblyopia. Nevertheless, human studies focused on advancing the standard of care for amblyopia have largely avoided recruitment of patients with this rare but severe impairment subtype. In this review, we delineate characteristics of deprivation amblyopia and underscore the critical need for new and more effective therapy. Animal models offer a unique opportunity to address this unmet need by enabling the development of unconventional and potent amblyopia therapies that cannot be pioneered in humans. Insights derived from studies using animal models are discussed as potential therapeutic innovations for the remediation of deprivation amblyopia. Retinal inactivation is highlighted as an emerging therapy that exhibits efficacy against the effects of monocular deprivation at ages when conventional therapy is ineffective, and recovery occurs without apparent detriment to the treated eye.

Recovery from Amblyopia in Adulthood: A Meta-Analysis

Purpose

The effectiveness of traditional amblyopia therapies is largely restricted to childhood. However, recovery in adulthood is possible following removal or vision-limiting disease of the fellow eye. Study of this phenomenon is currently limited to isolated case reports and a few case series, with reported incidence ranging from 19-77% 1-5 . We set out to accomplish two distinct goals: (1) define the incidence of clinically meaningful recovery and (2) elucidate the clinical features associated with greater amblyopic eye gains.

Methods

A systematic review of 3 literature databases yielded 23 reports containing 109 cases of patients ≥18 years old with unilateral amblyopia and vision-limiting fellow eye pathology.

Results

Study 1 revealed 25/42 (59.5%) of adult patients gained ≥2 logMAR lines in the amblyopia eye after FE vision loss. The overall degree of improvement is clinically meaningful (median 2.6 logMAR lines). Study 2 showed that for cases with amblyopic eye visual acuity improvement, recovery occurs within 12 months of initial loss of fellow eye vision. Regression analysis revealed that younger age, worse baseline acuity in the amblyopic eye, and worse vision in the fellow eye independently conferred greater gains in amblyopic eye visual acuity. Recovery occurs across amblyopia types and fellow eye pathologies, although disease entities affecting fellow eye retinal ganglion cells demonstrate shorter latencies to recovery.

Conclusions

Amblyopia recovery after fellow eye injury demonstrates that the adult brain harbors the neuroplastic capacity for clinically meaningful recovery, which could potentially be harnessed by novel approaches to treat adults with amblyopia.

The impact of COVID-19 on compliance to amblyopia treatment in a tertiary eye care center

Purpose

To investigate the impact of the coronavirus disease 2019 (COVID-19) outbreak on compliance to amblyopia therapy from the perspective of parents of amblyopic children.

Methods

The participants for the qualitative study were enrolled from the medical records of a tertiary eye care center during the COVID-19 pandemic. The trained researcher conducted telephonic interviews consisting of validated 15 open-ended questions for 15 min. The questions were related to patients' compliance toward amblyopia treatment and the date of follow-up with their practitioners. The data collected were entered on Excel sheets in the participant's own words and later converted to a transcript for analysis.

Results

A total of 217 parents of children with amblyopia who were due for follow-up were contacted through telephone. The response rate for willingness to participate was only 36% (n = 78). Of these, 76% (n = 59) of parents reported that their child was compliant toward the treatment during the therapy period and 69% reported that their child was currently not on treatment for amblyopia.

Conclusion

In the current study, we have observed that although reported compliance by parents during the therapy period was good, around 69% of patients had discontinued amblyopia therapy. The main reason for the discontinuation of therapy was the failure to visit the hospital during the scheduled follow-up with the eye care practitioner.

Factors predicting regression of visual acuity following successful treatment of anisometropic amblyopia

Objective

To identify factors associated with visual acuity regression following successful treatment of anisometropic amblyopia.

Design and method

This was a retrospective cohort study. Database records for 100 and 61 children with anisometropic amblyopia who met at least one criterion for successful treatment proposed by the Pediatric Eye Disease Investigator Group (PEDIG) and had at least 1 year of follow-up data available after the criterion was met were analyzed. The study sample was split into two groups, those who regressed within 1 year of successful treatment (no longer met any of the PEDIG criteria for successful treatment) and those who did not. A two-step analysis involving a least absolute shrinkage and selection operator (LASSO) regression and a logistic regression were used to identify predictor variables for increased risk of regression. A broad range of clinical, perceptual, and demographic variables were included in the analyses.

Results

Sixty-eight (42.5%) children regressed within 1 year of successful treatment. Among the 27 predictor variables considered within the statistical modeling process, the three most important for predicting treatment regression were the extent of amblyopic eye visual acuity improvement, age at first hospital visit and sex. Specifically, lower risk of regression was associated with larger amblyopic eye visual acuity improvement with treatment, younger age at initiation of treatment and female sex.

Conclusion

Patients who received treatment at a younger age and responded well to treatment had a lower risk of treatment regression. This pattern of results suggests that early detection of amblyopia and strategies that enhance treatment adherence may reduce the risk of treatment regression. The higher risk of regression in boys than girls that we observed may reflect known sex differences in brain development and /or sex differences in environment within our sample of children from South China.

Video game treatment of amblyopia

Amblyopia is visual impairment characterized by a structurally normal eye showing significantly lower visual acuity than the fellow eye. Traditional treatment of amblyopia includes patching the good eye to force the amblyopic eye to work during normal daily activities; however, this approach is are limited by low compliance. Recently, researchers proposed a new treatment for amblyopia: video game playing. In the current review, we discuss whether video game playing can treat amblyopia, whether video game playing could better treat amblyopia than traditional treatments, and how the video game treats amblyopia and its possible mechanism. Based on results from our literature review and meta-analysis, we suggest there is strong evidence for the effectiveness of video game treatments. Moreover, multiple factors within and outside of video games could influence the treatment effect.

Long-term follow-up of an amblyopia treatment study: change in visual acuity 15 years after occlusion therapy

Purpose

To determine change in visual acuity (VA) in the population of a previous amblyopia treatment study (Loudon 2006) and assess risk factors for VA decrease.

Methods

Subjects treated between 2001 and 2003 were contacted between December 2015 and July 2017. Orthoptic examination was conducted under controlled circumstances and included subjective refraction, best corrected VA, reading acuity, binocular vision, retinal fixation, cover‐uncover and alternating cover test. As a measure for degree of amblyopia, InterOcular VA Difference (IOD) at the end of occlusion therapy was compared with IOD at the follow‐up examination using Wilcoxon’s signed‐rank test. Regression analysis was conducted to determine the influence of clinical and socio‐economic factors on changes in IOD.

Results

Out of 303 subjects from the original study, 208 were contacted successfully, 59 refused and 15 were excluded because of non‐amblyopic cause of visual impairment. Mean IOD at end of therapy (mean age 6.4 years) was 0.11 ± 0.16 logMAR, and IOD at follow‐up examination (mean age 18.3 years) was 0.09 ± 0.21 logMAR; this difference was not significant (p = 0.054). Degree of anisometropia (p = 0.008; univariable analysis), increasing anisometropia (p = 0.009; multivariable), eccentric fixation (p < 0.001; univariable and multivariable); large IOD (p < 0.001; univariable and multivariable) and non‐compliance during therapy (p = 0.028; univariable) were associated with IOD increase.

Conclusion

Long‐term results of occlusion therapy were good. High or increasing anisometropia, eccentric fixation and non‐compliance during occlusion therapy were associated with long‐term VA decrease. Subjects with poor initial VA had a larger increase despite little patching, but often showed long‐term VA decrease.

Organic visual loss measured by kinetic perimetry and retinal electrophysiology in children with functional amblyopia

PURPOSE

To demonstrate an organic (retinal) amblyogenic defect in functional amblyopes not responding to treatment.

METHODS

Twenty-four children (Mean age: 5.9 ± 1.8 years; range: 4-10 years) with functional amblyopia were recruited for this study. All these children underwent complete ophthalmic and orthoptic evaluation. In addition, Kinetic Goldman Visual Fields (KGVF), Spectral Domain Optical Coherence Tomography (SD-OCT), full field flash electroretinograms (ffERG) and multifocal electroretinograms (mfERG) were also performed. Ratios were subsequently derived by comparing the amplitudes obtained from the amblyopic eye (AE) to the good eye (GE) for the a- and b-waves of the ffERG, as well as for the ring analysis of the mfERG.

RESULTS

KGVF showed a central scotoma of varying size (3°-7°) and density (absolute to relative), with increasing target size in 14/24 patients whose best post-treatment vision in the AE ranged from 20/100 to 20/40. The scotoma decreased in size and density with improving vision until a plateau of recovery was reached. The remaining 10/24 patients with a vision ≥ 20/30 showed no scotoma. SD-OCT showed no significant difference between the AE and GE. ffERG and mfERG were obtained in 18/24 patients. The ffERG AE/GE ratio was abnormal in 7 patients, 5 of which had large scotomas on KGVF. The mfERG ring 1 AE/GE ratio was significantly (p < .05) attenuated in 9/18 patients out of which 3 were no longer amblyopic. However, there was no significant difference (p > .05) in ring 1 AE/GE amplitude ratio between those who achieved 20/50-20/40 (.81 ± .26) and those with ≥ 20/25(.86 ± .25).

CONCLUSIONS

The combined findings of central scotoma on KGVF and mfERG anomalies in patients who did not achieve optimal vision with treatment suggest an underlying organic defect impairing macular function.

Fixational eye movements abnormalities and rate of visual acuity and stereoacuity improvement with part time patching

Residual amblyopia is seen in 40% of amblyopic patients treated with part-time patching. Amblyopic patients with infantile onset strabismus or anisometropia can develop fusion maldevelopment nystagmus syndrome (FMNS). The purpose of this study was to understand the effects of presence of FMNS and clinical subtype of amblyopia on visual acuity and stereo-acuity improvement in children treated with part-time patching. Forty amblyopic children who had fixation eye movement recordings and at least 12 months of follow-up after initiating part-time patching were included. We classified amblyopic subjects per the fixational eye movements characteristics into those without any nystagmus, those with FMNS and patients with nystagmus without any structural anomalies that do not meet the criteria of FMNS or idiopathic infantile nystagmus. We also classified the patients per the clinical type of amblyopia. Patching was continued until amblyopia was resolved or no visual acuity improvement was noted at two consecutive visits. Children with anisometropic amblyopia and without FMNS have a faster improvement and plateaued sooner. Regression was only seen in patients with strabismic/mixed amblyopia particularly those with FMNS. Patients with FMNS had improvement in visual acuity but poor stereopsis with part-time patching and required longer duration of treatment.

Macular Thickness, Foveal Volume, and Choroidal Thickness in Amblyopic Eyes and Their Relationships to the Treatment Outcome

Purpose

To assess the correlations between the retinal/choroidal structure and the treatment outcomes of amblyopic children.

Methods

This study enrolled eyes with amblyopia resulting from strabismus, anisometropia, or ametropia. All patients underwent detailed eye examinations, including spectral domain optical coherence tomography (SD-OCT) scan. All of the subjects received amblyopic treatment and were divided into 2 groups after 6 months of follow-up: the recovered amblyopic group with a best-corrected visual acuity (BCVA) ≥0.8 and the persistent amblyopic group with a BCVA <0.8 on the Landolt C chart.

Results

Forty-four amblyopic children were included, of which 26 were in the recovered amblyopic group after 6 months of follow-up. The patients with strabismic anisometropic amblyopia and severe amblyopia (initial VA ≤ 0.3) were significantly predisposed to developing persistent amblyopia (P=0.049 and P < 0.001, respectively). After correcting with Littmann's formula, the thickness and volume of the parafoveal and perifoveal retinal regions in the persistent amblyopia group did not show significant differences with the recovered amblyopia group.

Conclusions

The initial severity of amblyopia and the type of amblyopia were the risk factors related to the poor outcome of amblyopic treatment. The foveal thickness, foveal volume, and choroidal thickness were not associated with the treatment outcome.

Atropine vs patching for treatment of moderate amblyopia: follow-up at 15 years of age of a randomized clinical trial

IMPORTANCE

Initial treatment for amblyopia of the fellow eye with patching and atropine sulfate eyedrops improves visual acuity. Long-term data on the durability of treatment benefit are needed.

OBJECTIVE

To report visual acuity at 15 years of age among patients who were younger than 7 years when enrolled in a treatment trial for moderate amblyopia.

DESIGN, SETTING, AND PARTICIPANTS

In a multicenter clinical trial, 419 children with amblyopia (visual acuity, 20/40 to 20/100) were randomly assigned to patching (minimum of 6 h/d) or atropine sulfate eyedrops, 1% (1 drop daily), for 6 months. Treatment after 6 months was at the discretion of the investigator. Two years after enrollment, an unselected subgroup of 188 children were enrolled into long-term follow-up.

INTERVENTION

Initial treatment with patching or atropine with subsequent treatment at investigator discretion.

MAIN OUTCOMES AND MEASURES

Visual acuity at 15 years of age with the electronic Early Treatment Diabetic Retinopathy Study test in amblyopic and fellow eyes.

RESULTS

Mean visual acuity in the amblyopic eye measured in 147 participants at 15 years of age was 0.14 logMAR (approximately 20/25); 59.9% of amblyopic eyes had visual acuity of 20/25 or better and 33.3%, 20/20 or better. Mean interocular acuity difference (IOD) at 15 years of age was 0.21 logMAR (2.1 lines); 48.3% had an IOD of 2 or more lines and 71.4%, 1 or more lines. Treatment (other than spectacles) was prescribed for 9 participants (6.1%) aged 10 to 15 years. Mean IOD was similar at examinations at 10 and 15 years of age (2.0 and 2.1 logMAR lines, respectively; P = .39). Better visual acuity at the 15-year examination was achieved in those who were younger than 5 years at the time of entry into the randomized clinical trial (mean logMAR, 0.09) compared with those aged 5 to 6 years (mean logMAR, 0.18; P < .001). When we compared subgroups based on original treatment with atropine or patching, no significant differences were observed in visual acuity of amblyopic and fellow eyes at 15 years of age (P = .44 and P = .43, respectively).

CONCLUSIONS AND RELEVANCE

At 15 years of age, most children treated for moderate amblyopia when younger than 7 years have good visual acuity, although mild residual amblyopia is common. The outcome is similar regardless of initial treatment with atropine or patching. The results indicate that improvement occurring with amblyopia treatment is maintained until at least 15 years of age.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00000170.

Factors predicting recurrence in successfully treated cases of anisometropic amblyopia

Context:

Recurrence after successful treatment of amblyopia is known and understanding the risk factors could help effective management.

Aim:

To measure incidence of recurrence in successfully treated cases of anisometropic amblyopia and evaluate factors predicting it.

Settings and Design:

Cohort Study at a tertiary level institution.

Materials and Methods:

Successfully treated anisometropic amblyopes aged 4−12 years were followed up for 1 year after stopping therapy. Best corrected visual acuity (BCVA), refractive error, stereoacuity and contrast sensitivity were evaluated at baseline and follow-up.

Statistical Analysis:

Intergroup analysis with appropriate tests: Chi-square test, Fisher's exact test, Wilcoxon rank sum test and paired t-test.

Results:

One hundred and two patients with mean age at diagnosis 7.06 ± 1.81 years were followed-up for a mean duration of 1.0 ± 0.2 years. The mean pre-treatment BCVA (LogMAR score) at diagnosis was 0.73 ± 0.36 units which improved to 0.20 ± 0.00 with treatment and after 1 year of stopping treatment was 0.22 ± 0.07. Thirteen (12.74%) patients showed amblyopia recurrence during follow-up. Risk of recurrence was higher with older age of onset of treatment (6.64 ± 1.77 years without recurrence v/s 8.53 ± 1.39 years with recurrence, P = 0.0014). Greater extent of improvement of VA (P = 0.048) and final VA at stopping occlusion (P = 0.03) were associated with higher recurrence. Binocularity status or stereoacuity changes were not associated with risk of recurrence.

Conclusions:

Significant numbers of children suffer recurrence of amblyopia after stopping therapy. Older age, better BCVA after stopping therapy and greater magnitude of improvement in BCVA are important risk factors for recurrence. Careful follow-up is essential for early detection and management of recurrence.

Visual functions in amblyopia as determinants of response to treatment

PURPOSE

To describe the visual functions in amblyopia as determinants of response to treatment.

METHODS

Sixty-nine patients with unilateral and bilateral amblyopia (114 amblyopic eyes) 3 to 15 years old (mean age: 8.80 ± 2.9 years), 40 males (58%) and 29 females (42%), were included in this study. All patients were treated by conventional occlusion 6 hours per day for mild to moderate amblyopia (visual acuity 0.70 or better) and full-time for 4 weeks followed by 6 hours per day for severe amblyopia (visual acuity 0.8 or worse). During occlusion, near activities requiring hand-eye coordination were advised. The follow-up examination was done at 3 and 6 months. Improvement in visual acuity was evaluated on the logMAR chart and correlated with the visual functions. Statistical analysis was done using Wilcoxon rank sum test (Mann-Whitney U test) and Kruskal-Wallis analysis.

RESULTS

There was a statistically significant association of poor contrast sensitivity with the grade of amblyopia (P < .001). The grade of amblyopia (P < .01), accommodation (P < .01), stereopsis (P = .01), and mesopic visual acuity (P < .03) were found to have a correlation with response to amblyopia therapy.

CONCLUSIONS

The grade of amblyopia (initial visual acuity) and accommodation are strong determinants of response to amblyopia therapy, whereas stereopsis and mesopic visual acuity have some value as determinants.

Can perceptual learning be used to treat amblyopia beyond the critical period of visual development?

BACKGROUND

Amblyopia presents early in childhood and affects approximately 3% of western populations. The monocular visual acuity loss is conventionally treated during the 'critical periods' of visual development by occluding or penalising the fellow eye to encourage use of the amblyopic eye. Despite the measurable success of this approach in many children, substantial numbers of people still suffer with amblyopia later in life because either they were never diagnosed in childhood, did not respond to the original treatment, the amblyopia was only partially remediated, or their acuity loss returned after cessation of treatment.

PURPOSE

In this review, we consider whether the visual deficits of this largely overlooked amblyopic group are amenable to conventional and innovative therapeutic interventions later in life, well beyond the age at which treatment is thought to be effective.

RECENT FINDINGS

There is a considerable body of evidence that residual plasticity is present in the adult visual brain and this can be harnessed to improve function in adults with amblyopia. Perceptual training protocols have been developed to optimise visual gains in this clinical population. Results thus far are extremely encouraging; marked visual improvements have been demonstrated, the perceptual benefits transfer to new visual tasks and appear to be relatively enduring. The essential ingredients of perceptual training protocols are being incorporated into video game formats, facilitating home-based interventions.

SUMMARY

Many studies support perceptual training as a tool for improving vision in amblyopes beyond the critical period. Should this novel form of treatment stand up to the scrutiny of a randomised controlled trial, clinicians may need to re-evaluate their therapeutic approach to adults with amblyopia.

Termination of amblyopia treatment: when to stop follow-up visits and risk factors for recurrence

BACKGROUND

This study estimated when it is safe to stop follow-up visits after cessation of amblyopia treatment and to identify factors associated with deterioration of visual acuity.

METHODS

Study patients included 282 patients aged 7 to 13 years who were monitored for deterioration after cessation of amblyopia treatment (median follow-up: 3.9 years).

RESULTS

Six (2.1%) patients lost 2 or more logarithm of the minimum angle of resolution levels of visual acuity and 77 (27.3%) patients lost 1 or more Snellen lines of visual acuity. Good compliance with re-treatment stopped further deterioration and lost visual acuity was regained (average follow-up after re-treatment: 3.3 years). Life table analysis indicated that 95% of the cases that deteriorated occurred within 24 months after cessation of treatment. Multivariable analysis corrected for duration of treatment uncovered factors independently associated with deterioration.

CONCLUSION

A clinically important risk of deterioration of visual acuity was found during the first 2 years after cessation of amblyopia treatment. Follow-up time longer than 2 years is recommended in the presence of a developing risk factor such as increasing anisometropia. With prompt re-treatment and good compliance, deterioration can be stopped and visual acuity can be restored.

Efficacy of Occlusion Treatment in Amblyopia and Clinical Risk Factors Affecting the Results of Treatment

PURPOSE

To evaluate the factors influencing visual outcome in strabismic, strabismic-anisometropic and anisometropic amblyopia following occlusion treatment.

METHODS

Records of 128 pediatric patients who had been treated for amblyopia by occlusion of the fellow eye between March 1992 and March 2003 were reviewed retrospectively. Age and level of visual acuity at initiation of treatment, occlusion time (full-time, part-time or minimal) and type of amblyopia were analyzed for the effect on visual outcome.

RESULTS

The mean age of the patients was 5.69 +/- 2.01 years (3 to 12 years). Mean follow-up time was 3 years 2 months (6 months to 10 years). Mean visual acuity improvements were similar for the subtypes of amblyopia (strabismic amblyopia 0.38 +/- 0.29 logMAR units, strabismic-anisometropic amblyopia 0.46 +/- 0.40 logMAR units, anisometropic amblyopia 0.35 +/- 0.24 logMAR units). Level of initial visual acuity, age at initiation of treatment and type of occlusion correlated with the final visual acuity (p = 0.000, p = 0.035, p = 0.012, respectively). When the analysis was performed according to the subtypes of amblyopia, initial visual acuity was the only factor associated with the final visual acuity in all types of amblyopia (p < 0.05).

CONCLUSION

The level of initial visual acuity is the most significant factor determining the success of treatment in amblyopia.

A randomized trial of atropine vs patching for treatment of moderate amblyopia: follow-up at age 10 years

OBJECTIVE

To determine the visual acuity outcome at age 10 years for children younger than 7 years when enrolled in a treatment trial for moderate amblyopia.

METHODS

In a multicenter clinical trial, 419 children with amblyopia (visual acuity, 20/40-20/100) were randomized to patching or atropine eyedrops for 6 months. Two years after enrollment, a subgroup of 188 children entered long-term follow-up. Treatment after 6 months was at the discretion of the investigator; 89% of children were treated.

MAIN OUTCOME MEASURE

Visual acuity at age 10 years with the electronic Early Treatment Diabetic Retinopathy Study test.

APPLICATION TO CLINICAL PRACTICE

Patching and atropine eyedrops produce comparable improvement in visual acuity that is maintained through age 10 years.

RESULTS

The mean amblyopic eye acuity, measured in 169 patients, at age 10 years was 0.17 logMAR (logarithm of the minimum angle of resolution) (approximately 20/32), and 46% of amblyopic eyes had an acuity of 20/25 or better. Age younger than 5 years at entry into the randomized trial was associated with a better visual acuity outcome (P < .001). Mean amblyopic and sound eye visual acuities at age 10 years were similar in the original treatment groups (P = .56 and P = .80, respectively).

CONCLUSIONS

At age 10 years, the improvement of the amblyopic eye is maintained, although residual amblyopia is common after treatment initiated at age 3 years to younger than 7 years. The outcome is similar regardless of initial treatment with atropine or patching.

Current concepts in the management of amblyopia

Traditional treatment of amblyopia, although still in use and of great value, has recently been challenged by data from studies relative to efficacy of different modalities and regimens of therapy. LogMAR-based acuity charts should be used, whenever possible, for diagnosis and monitoring. Refractive errors of certain magnitude should be prescribed, and correction worn for at least 4 months before occlusion or penalization are used. Occlusion has a linear dose-response effect (1 logMAR line gain per 120 hours of patching), and outcomes of 2 hour/day dosage are similar to more extended therapy, at least in moderate amblyopia, but increasing dosage beyond hastens the response. Pharmacologic, optical, or combined penalization is useful as an alternative or maintaining therapy, and is presumably of particular efficacy in anisometropic amblyopia. At least in moderate amblyopia, atropine penalization is as effective as patching in terms of visual acuity improvement and stereoacuity outcome.

Strabismus might be a risk factor for amblyopia recurrence

BACKGROUND

Previous reports have suggested that one-fourth of amblyopic subjects present with recurrence of amblyopia even after successful primary treatment. Risk factors for amblyopia recurrence are insufficiently studied, but therapy weaning has recently been suggested as a method for reducing the risk of recurrence.

METHODS

In the second phase of a prospective study examining the results of treatment for amblyopia, all 35 children with successful primary amblyopia treatment were put on maintenance therapy. Maintenance therapy consisted of low-intensity patching, atropine, or blurring filter, and all children were regularly examined up to at least 8 years of age. Mean age at start of maintenance therapy was 4.3 years (range, 2-7 years).

RESULTS

Of the 35 cases with successful primary treatment, 6 cases deteriorated >or=0.2 logMAR, which was considered recurrence of amblyopia. Two of these cases had a second recurrence. Notably, all six subjects presenting with recurrence had microstrabismus. This finding was just outside statistical significance at the 95% confidence level (p = 0.06), but the sample size was small. All but one of the recurrences appeared within 6 months after successful primary treatment. Age at successful primary treatment or initial interocular difference of visual acuity did not affect the risk of recurrence.

CONCLUSIONS

Recurrence of amblyopia occurred in 17% of patients despite maintenance therapy and was associated with microstrabismus. The majority of recurrences occurred within the first 6 months after primary treatment.

Factors associated with recurrence of amblyopia on cessation of patching

PURPOSE

In a prospective observational study, we previously reported that weaning (tapering or gradually reducing) treatment in children treated with 6 to 8 hours of daily patching for amblyopia resulted in a 4-fold reduction in odds of recurrence. We now report the association of additional factors with recurrence or regression of amblyopia in this same cohort.

DESIGN

Prospective, nonrandomized, observational study.

PARTICIPANTS

Sixty-nine children aged <8 years with successfully treated anisometropic or strabismic amblyopia (improved > or =3 logarithm of the minimum angle of resolution [logMAR] lines).

METHODS

Patients were enrolled at the time they stopped patching for amblyopia. Patients were classified according to whether patching was stopped abruptly or weaned before cessation. They were followed off treatment for 52 weeks to assess recurrence of amblyopia.

MAIN OUTCOME MEASURE

Recurrence of amblyopia defined as a > or =2-logMAR level reduction of visual acuity from enrollment (cessation of patching) confirmed by a second examination. Recurrence was also considered to have occurred if treatment was restarted with a > or =2-logMAR level reduction of visual acuity, even if it was not confirmed by a second examination.

RESULTS

The risk of recurrence was higher with better visual acuity at the time of cessation of treatment (adjusted risk ratio [RR], 0.68 per line of worse visual acuity; 95% confidence interval [CI], 0.51-0.90), a greater number of lines improved during the previous treatment (adjusted RR, 1.5 per line increase; 95% CI, 1.1-2.0), and a history of recurrence (adjusted RR, 2.7; 95% CI, 1.5-4.9). Orthotropia or excellent stereoacuity at the time of patching cessation did not appear to have a protective effect on the risk of recurrence.

CONCLUSIONS

The higher risk of recurrence in the most successfully treated children with amblyopia and absence of protection from orthotropia and excellent random dot stereoacuity suggests that careful and prolonged follow-up is needed for all children who have been previously treated for amblyopia.

Stability of visual acuity after the cessation of amblyopia treatment: review of the literature

INTRODUCTION AND PURPOSE

The treatment of amblyopia in children is frequently discussed in the literature. Less attention, however, has been given to the durability of the visual acuity results attained with therapy. The objective of this review is to conduct an in-depth analysis of the existing literature, on the stability of visual acuity following cessation of amblyopia treatment, and to identify any gaps in the literature, which could guide future investigations.

RESULTS

There did not appear to be any one consistent risk factor affecting the stability of vision after cessation of amblyopia treatment. Most of the reviewed studies varied with respect to lengths of follow-up visits, patient population, and method of visual acuity assessment. There was also a generalized lack of standardization of visual acuity measurements in these previous investigations. Only one of the studies analyzed was a prospective design.

CONCLUSION

The area of study in amblyopia is fraught with contradictions. It is obvious from this review that there exists uncertainty regarding the recurrence of amblyopia following treatment. Previous studies have failed to identify any common, predictive, influencing factors necessary for the maintenance of visual acuity after cessation of therapy. Also lacking is discussion on the potential role that therapy tapering plays in the recurrence of amblyopia following the cessation of treatment.

Factors affecting the stability of visual function following cessation of occlusion therapy for amblyopia

AIM

To identify factors that predict which children with amblyopia are at greatest risk of regression of visual acuity (VA) following the cessation of occlusion therapy.

METHOD

A retrospective analysis was performed of 182 children (mean age at cessation of treatment; 5.9+/-1.6 years) who had undergone occlusion therapy for unilateral amblyopia, and had been followed up at least once within 15 months of cessation. Statistical analysis was used to identify whether change in VA following treatment cessation had any association with various factors, including the child's age, type of amblyopia, degree of anisometropia, initial severity of amblyopia, binocular vision status, length and dose of occlusion therapy, and VA response to treatment.

RESULTS

At 1 year, follow-up from treatment cessation, children with "mixed" amblyopia (both anisometropia and strabismus) demonstrated significantly (p=0.03) greater deterioration in VA (0.11+/-0.11 log units) than children with only anisometropia (0.02+/-0.08 log units) or only strabismus (0.05+/-0.10 log units). However, none of the other factors investigated were found to be significant predictors.

CONCLUSION

This study supports previous research that it is possible to identify those children most at risk of deterioration in VA following cessation of occlusion therapy. The presence of mixed amblyopia was the only risk factor identified in this study. Management of amblyopia should take this into account, with a more intensive follow-up recommended for those with both anisometropia and strabismus (mixed) amblyopia.

Successful treatment of anisometropic amblyopia with spectacles alone

BACKGROUND

The efficacy of treating anisometropic amblyopia with occlusion therapy is well known. However, this form of treatment can be associated with risks. Spectacle correction alone may be a successful and underutilized form of treatment.

METHODS

The records of 28 patients treated successfully for anisometropic amblyopia with glasses alone were reviewed. Age, initial visual acuity and stereoacuity, and nature of anisometropia were analyzed to assess associations with time required for resolution, final visual acuity, and stereoacuity. Incidence of amblyopia recurrence and results of subsequent treatment, including patching, were also studied.

RESULTS

Mean time to amblyopia resolution (interocular acuity difference <or=1 line) was 5.8 months (range 2 to 15 months). Worse best corrected initial visual acuity was associated with longer time to resolution (Spearman's rho = 0.37, P = 0.05), while age, initial stereoacuity, amount, and type of anisometropia were not (P = 0.43, 0.68, 0.26, 0.47, respectively). None of the astigmatic or myopic patients achieved visual acuity of 20/20 in the amblyopic eye, while seven (39%) of the hyperopic patients did. This difference was significant (P = 0.03). Better initial stereoacuity predicted good final stereoacuity (P = 0.01). Only four (14%) patients developed amblyopia recurrence over an average follow-up period of 1.7 years. All were successfully treated with updated spectacles or patching.

CONCLUSIONS

Treatment of anisometropic amblyopia with spectacles alone can be a successful option. Patients treated with spectacles alone may experience a lower amblyopia recurrence rate than those treated with occlusion therapy.

Controversy in amblyopia management

BACKGROUND AND PURPOSE

Much has been written about amblyopia treatment. However, there is no consensus on the most efficacious therapeutic modality for amblyopia. The intensity of therapy needed to maximize visual acuity is also widely debated. The diversity of opinions emphasizes that the optimum treatment for amblyopia is unknown. Part of the uncertainty stems from the lack of standardization in the management of amblyopia. The objective of this paper is to conduct an in-depth review of the literature in an attempt to clarify the amblyopia treatment conundrum.

CONCLUSIONS

The treatment of amblyopia in children is frequently discussed in the literature. It is obvious from the literature that there is the need for prospective studies with consistent controls, clear definitions of what constitutes successful therapy endpoints, and standardization of testing procedures.

Amblyopia characterization, treatment, and prophylaxis

Amblyopia has a 1.6-3.6% prevalence, higher in the medically underserved. It is more complex than simply visual acuity loss and the better eye has sub-clinical deficits. Functional limitations appear more extensive and loss of vision in the better eye of amblyopes more prevalent than previously thought. Amblyopia screening and treatment are efficacious, but cost-effectiveness concerns remain. Refractive correction alone may successfully treat anisometropic amblyopia and it, minimal occlusion, and/or catecholamine treatment can provide initial vision improvement that may improve compliance with subsequent long-duration treatment. Atropine penalization appears as effective as occlusion for moderate amblyopia, with limited-day penalization as effective as full-time. Cytidin-5'-diphosphocholine may hold promise as a medical treatment. Interpretation of much of the amblyopia literature is made difficult by: inaccurate visual acuity measurement at initial visit, lack of adequate refractive correction prior to and during treatment, and lack of long-term follow-up results. Successful treatment can be achieved in at most 63-83% of patients. Treatment outcome is a function of initial visual acuity and type of amblyopia, and a reciprocal product of treatment efficacy, duration, and compliance. Age at treatment onset is not predictive of outcome in many studies but detection under versus over 2-3 years of age may be. Multiple screenings prior to that age, and prompt treatment, reduce prevalence. Would a single early cycloplegic photoscreening be as, or more, successful at detection or prediction than the multiple screenings, and more cost-effective? Penalization and occlusion have minimal incidence of reverse amblyopia and/or side-effects, no significant influence on emmetropization, and no consistent effect on sign or size of post-treatment changes in strabismic deviation. There may be a physiologic basis for better age-indifferent outcome than tapped by current treatment methodologies. Infant refractive correction substantially reduces accommodative esotropia and amblyopia incidence without interference with emmetropization. Compensatory prism, alone or post-operatively, and/or minus lens treatment, and/or wide-field fusional amplitude training, may reduce risk of early onset esotropia. Multivariate screening using continuous-scale measurements may be more effective than traditional single-test dichotomous pass/fail measures. Pigmentation may be one parameter because Caucasians are at higher risk for esotropia than non-whites.

Efficacy of amblyopia therapy initiated after 9 years of age

AIMS/PURPOSE

To evaluate the efficacy of occlusion therapy initiated after 9 years of age.

METHODS

A total of 16 amblyopes of 9 years or older (range, 9.0-14.5 years; mean, 10.5 years) with a difference in visual acuity of over two lines between the eyes alter 4 weeks of first full-time spectacle wear were included. None of the children had undergone a previous ocular examination, had ever worn spectacles, received occlusion therapy, or had strabismus surgery. Initial worst visual acuity after 4 weeks of full-time spectacle wear was 20/100 in three patients, between 20/80 and 20/40 in 11 patients, and 20/30 in two patients. Full-time occlusion was performed in 14 patients and part-time occlusion in two patients.

RESULTS

The final visual acuity of 15 out of 16 patients (94%) improved at least two lines. The final visual acuities ranged from 20/30 to 20/20 in 14 patients, 20/40 in one patient, and 20/50 in one remaining patient who began amblyopia therapy at 14.5 years of age, with the poorest compliance among the patients.

CONCLUSIONS

Occlusion therapy for anisometropic and strabismic amblyopia can be successful even if initiated after the age of 9 years.

Long-Term Changes in Visual Acuity and Refractive Error in Amblyopes

PURPOSE

To report long-term changes in visual acuity and refractive error for strabismic, anisometropic, and isoametropic amblyopes.

METHODS

Records of patients with strabismic amblyopia, anisometropic amblyopia, and isoametropic amblyopia who were treated from 1983 to 1993 were reviewed. Excluded were patients having ocular or neurological diseases, developmental delay, and follow-up <4 years after treatment cessation. Data included best-correctable visual acuity and spherical equivalent refractive error of the amblyopic and the nonamblyopic eye at pretreatment, posttreatment, and long-term follow-up.

RESULTS

Records for 61 patients met the inclusion criteria. For strabismic amblyopia (n = 22), mean visual acuity in amblyopic and nonamblyopic eyes improved 0.36 and 0.05 logarithm of the minimum angle of resolution (logMAR) units after a mean treatment time of 1 year. At long-term follow-up (mean = 9.3 years after treatment), visual acuity in the amblyopic eye regressed 0.09 logMAR and visual acuity in the nonamblyopic eye improved 0.10 logMAR units. For anisometropic amblyopia (n = 26), mean visual acuity in amblyopic and nonamblyopic eyes improved 0.30 and 0.02 logMAR units, respectively, after a mean treatment period of 1.1 year. At the long-term follow-up visit (mean = 7.1 years after treatment), visual acuity in the amblyopic eye regressed 0.09 logMAR unit and in the nonamblyopic eye improved 0.03 logMAR unit. Repeated-measures analysis of variance showed no significant effect of type of amblyopia on visual acuity of the amblyopic eye and a significant effect of visit due to treatment but not regression. The changes in visual acuity in the nonamblyopic eye from the pretreatment to the follow-up visit were significant and interacted with type, the changes being larger in strabismic amblyopia. For strabismic amblyopia, the mean refractive error in amblyopic and nonamblyopic eyes changed from +2.15 D and +1.85 D, respectively, initially to +0.45 D and +0.58 D, respectively, at the follow-up visit. For anisometropic amblyopia, the mean refractive error in amblyopic and nonamblyopic eyes changed from +1.04 D and +0.12 D, respectively, initially to +0.23 D and -0.94 D, respectively, at the follow-up visit. The effect of visit on amblyopic and nonamblyopic refractive errors was significant. For isoametropic amblyopia (n = 13), visual acuity in both right and left eyes initially was 0.39 logMAR unit and improved to 0.14 logMAR unit in each eye after a mean follow-up of 8.9 years. Refractive error in the right and the left eyes changed from -1.22 D and -1.14 D, respectively, to -2.68 D and -2.56 D, respectively, at follow-up. These differences were all significant.

CONCLUSIONS

After treatment and with long-term follow up, visual acuity regresses but not significantly in the amblyopic eye in strabismic amblyopia and anisometropic amblyopia. At the same time, visual acuity in the nonamblyopic eye improves slightly. Visual acuity also improves significantly over time in isoametropic amblyopia. The refractive error of both amblyopic and nonamblyopic eyes tends to show a myopic shift regardless of the type of amblyopia.

Photorefractive keratectomy for anisometropic amblyopia in children

PURPOSE

To assess the safety and efficacy of photorefractive keratectomy (PRK) in children with anisometropic amblyopia and to define the characteristics of children who may be candidates for PRK.

METHODS

This thesis comprises four parts: (1) a retrospective analysis of risk factors predictive of amblyopia treatment failure in 104 children, (2) a prospective study of pachymetry in 198 eyes of 108 children, (3) development and implementation of a protocol to perform PRK under general anesthesia, and (4) a prospective interventional case-comparison study of PRK in 11 noncompliant children with anisometropic amblyopia to evaluate safety and long-term outcomes. Compliant and noncompliant children with anisometropic amblyopia were analyzed as controls.

RESULTS

Factors associated with conventional anisometropic amblyopia treatment failure were poor compliance (P = .004), age 6 years or older (P = .01), astigmatism > or = 1.5 diopters (P = .0002), and initial visual acuity of 20/200 or worse (P = .02). Central and paracentral pachymetry measurements were similar to published adult values. The general anesthesia protocol was efficient, and the laser functioned properly in all cases. All children did well with no anesthesia-related or treatment-related complications. Two years following PRK, the mean reduction in refractive error was 9.7 +/- 2.6 diopters for myopes (P = .0001) and 3.4 +/- 1.3 diopters for hyperopes (P = .001). The cycloplegic refractive error in 9 of 11 treated eyes was within 3 diopters of that in the fellow eye. Uncorrected visual acuity in the amblyopic eye improved by > or = 2 lines in seven of nine children; best-corrected visual acuity improved by > or = 2 lines in six of nine children. Stereopsis improved in five of nine children. The mean visual acuity of the PRK patients at last follow-up was significantly better than that of noncompliant controls (P = .003). The safety and efficacy indices for PRK in this study were 1.24 and 1.12, respectively.

CONCLUSIONS

Photorefractive keratectomy can be safely performed in children with anisometropic amblyopia. Visual acuity and stereopsis improved in most eyes, even in older children. Photorefractive keratectomy may have an important role in the management of anisometropic amblyopia in noncompliant children.

The relationship between stereopsis and visual acuity after occlusion therapy for amblyopia

PURPOSE

To investigate the relationship between visual acuity (VA) and stereoacuity after occlusion therapy in patients with various types of amblyopia.

DESIGN

Retrospective noncomparative case series.

PARTICIPANTS

Sixty-one children with amblyopia caused by anisometropia with no strabismus (26 children), small angle (</=8 prism diopters) or intermittent strabismus (20), or both (15).

METHODS

All were treated with occlusion therapy. Visual acuity and near stereopsis using the Titmus test (Stereo Optical Inc., Chicago, IL) were measured at each clinic visit.

MAIN OUTCOME MEASURE

The change in near stereopsis relative to distance VA after occlusion therapy.

RESULTS

Mean age at initiation of therapy was 5.1 years (range = 3.5-8) and mean follow-up 52.3 weeks (range = 13-192). Mean duration of occlusion was 36 weeks (range = 12-102). After occlusion treatment, mean VA of all children improved from 0.43 to 0.78 (P<0.0001), whereas mean stereoacuity improved from 1167.4 seconds of arc to 101 (P<0.0001). By the last visit, 85.2% (52 of 61) of patients demonstrated at least 2 lines of improvement in VA. There was a significant linear relationship between VA and stereoacuity (P<0.001). The 26 anisometropic patients without strabismus enjoyed improvement in VA and stereopsis (P<0.0001) similar to that of the 35 with small-angle or intermittent strabismus (P<0.0001).

CONCLUSIONS

When employing occlusion therapy for amblyopia (due to anisometropia, small-angle or intermittent strabismus, or a combination), as VA improves, stereopsis generally also improves.

Long term visual outcome in amblyopia treatment

AIM

To evaluate long term visual outcome of treatment for amblyopia.

METHODS

In a previous study, 44 children with unilateral amblyopia caused by strabismus or anisometropia were enrolled in a prospective study investigating the results of treatment. All children were regularly examined up to at least 8 years of age and outcome was evaluated. All subjects were invited to a re-examination and in total 26 subjects attended. Two of these were excluded because of insufficient records. The final sample consists of 24 subjects. Mean follow up time was 10.4 (SD 1.9) years.

RESULTS

For the amblyopic eyes, 17% deteriorated in visual acuity, 50% were stable, and 33% gained in visual acuity. For the non-amblyopic eyes, 8% lost one line in visual acuity, 38% were stable, and 54% gained in visual acuity. No eye in any subject shifted more than 0.2 logMAR units. The increase in visual acuity for the non-amblyopic eyes was significant, while the increase for the amblyopic eyes was not. All straight eyed anisometropic amblyopes showed a distinct decrease in magnitude of anisometropia.

CONCLUSIONS

Visual acuity was essentially stable in the amblyopic eyes 10 years after cessation of treatment in the studied population.

Long-term follow-up of occlusion therapy in amblyopia

OBJECTIVE

To determine whether the results of occlusion therapy for amblyopia are maintained into adulthood.

DESIGN

Prospective, observational case series.

PARTICIPANTS

Fifty-four patients, who were successfully treated in childhood for unilateral amblyopia by occlusion, were followed up to the age of 9 years, were evaluated in 1984 for long-term results 6.4 years on average after cessation of treatment, and accepted our invitation for reevaluation in 1999.

METHODS

All patients were given a complete eye examination. The visual acuity (VA) was measured.

RESULTS

The average period of follow-up was 21.5 years (range, 17.2-25.1 years). The mean age at the most recent examination was 29.0 +/- 2.1 years (range, 25.1-34). At this examination, a best-corrected visual acuity (BCVA) of 20/40 or better was achieved by 72.3% of the patients. The mean BCVA was 20/35 (20/25-20/70) at the end of occlusion therapy, 20/45 (20/20-20/300) in 1984, and 20/34 (20/15-20/100) at the present examination. Relative to the results at the end of therapy, BCVA at the present examination was maintained or improved in 66.7% of the patients. Relative to 1984, the BCVA in 1999 was maintained or improved in 87% of the patients.

MAIN OUTCOME MEASURE

Visual acuity.

CONCLUSION

Comparative evaluation of BCVA at a long-term follow-up examination, performed 21.5 years on average after cessation of occlusion therapy, showed that VA was maintained or improved in two thirds of patients who had been successfully treated by occlusion for unilateral amblyopia in childhood.

Considerations in the routine assessment and treatment of anisometropic amblyopia

Anisometropic amblyopia has traditionally been treated by direct occlusion with or without refractive correction of the anisometropia. This treatment has generally been considered so successful that practitioners prescribe occlusion for a time and consider treatment complete when visual acuity is no longer improving. The aetiology of anisometropic amblyopia, addressing the functional deficits of the amblyopic system and patient compliance issues, are important to the success of amblyopia treatment in anisometropia and are briefly reviewed in this paper. We propose that, while each case of anisometropic amblyopia may have slightly different attributes, initially they should all be treated with occlusion and full-time spectacle correction. Some presentations may be responsive to individual treatment strategies to correct binocular functions such as stereopsis, accommodative response and fusional vergences.

Natural history of amblyopia untreated owing to lack of compliance

AIMS

A prospective study of the efficacy of amblyopia treatment in preschool children has recently been called for, requiring an untreated control group. The present study assessed data from patients with amblyopia untreated owing to lack of compliance, or with amblyopia risk factors, to determine outcome.

METHODS

Longitudinal data were obtained from 18 4-6 year old patients who had initially been screened for amblyopia, strabismus, and/or bilateral refractive error, failed to comply with prescribed treatment, and in whom amblyopia was detected at a rescreening approximately a year later. The data from three previous studies comparing outcome of patients compliant and non-compliant with amblyopia treatment were also reanalysed.

RESULTS

One child of the 18, who wore glasses sporadically, showed some improvement in visual acuity in the amblyopic eye. Otherwise, no child showed an improvement, and seven of the 17 (41%) for whom visual acuities were available at both screenings showed a deterioration of visual acuity in the amblyopic eye, including three who apparently developed amblyopia for the first time. A child with an ametropic risk factor for amblyopia whose visual acuity was not obtained at the first screening and who was largely non-compliant presented with amblyopia at the second screening. The reanalysed data from the three previous studies demonstrated a significantly poorer visual acuity outcome in the amblyopic eye in the non-compliant patient groups than in the compliant groups in each study.

CONCLUSION

Preschool children with amblyopia or its risk factors are at risk of having the current amblyopia deteriorate, or of developing amblyopia, if not treated. These results raise questions about the ethical acceptability of a prospective study of amblyopia treatment at these ages.

Movement hyperacuity in childhood amblyopia

BACKGROUND

Amblyopia results in deficits in a number of visual functions in both the amblyopic and dominant eye. The present work describes oscillatory movement displacement thresholds (OMDT) in childhood amblyopia.

METHODS

The OMDT from the dominant and amblyopic eyes of 50 orthoptic patients (aged 74 (SD 16) months) were compared with those from a group of 24 controls (79 (21) months). OMDT were measured using a forced choice staircase procedure. Subjects were asked to identify which of the computer controlled monitors displayed the oscillating stimulus. Visual acuity and stereoscopic responses were noted from clinical records.

RESULTS

Amblyopic children demonstrating stereopsis showed no significant OMDT deficit in the amblyopic eye. Those children having no stereopsis had elevated OMDT in the amblyopic eye (p < 0.05). Results suggest that the dominant eye of children with amblyopia may also have a pattern of visual development which is anomalous (difference in correlation coefficient with age; p < 0.05).

CONCLUSION

OMDT deficits demonstrated in some amblyopic eyes indicate that amblyopia is incompletely described by its "clinical" definition. Results suggest that the dominant eye in those with unilateral amblyopia may not be "normal".

An inner city preschool visual screening programme: long-term visual results

AIMS

The aim of this study was to investigate the long-term outcome of the treatment of amblyopia as a sequel to preschool screening, which has not hither-to been described.

METHODS

All patients originally referred from a preschool screening programme were recalled for examination by letter. 255 patients were reviewed at least 4 years after discharge of which 88 were definitely amblyopic at presentation and 107 were not amblyopic at presentation and were used as controls.

RESULTS

79% of the amblyopes improved or maintained visual acuity after discharge but this was reduced to 42% after an age induced increase (estimated from the controls) was compensated for. The mean drop in visual acuity in the amblyopic eyes which deteriorated was 0.23 (SD 0.15) logMAR units. Stepwise multiple linear regression showed that the best single predictor of post-discharge deterioration in visual acuity was the improvement in visual acuity seen during treatment (R2 = 19%). Eccentric fixation at time of follow up (increasing R2 to 47%) and good presenting acuity (further raising R2 to 57%) contributed additional information, and were both associated with greater post-discharge deterioration in visual acuity.

CONCLUSIONS

The majority of amblyopes who attended for follow up maintained or improved their visual acuities after discharge. Those patients who demonstrated deterioration of their amblyopia had usually improved well during the programme and were often fixating eccentrically at follow up.

Long-term effect of hypermetropic anisometropia on the visual acuity of treated amblyopic eyes

AIM

To evaluate the effect of the extent of hypermetropic anisometropia on the long term visual acuity results in amblyopic eyes following their treatment by occlusion.

METHODS

The visual acuity of 86 patients, who had been treated for unilateral amblyopia by occlusion of the fellow eye and followed up at least to the age of 9 years, was examined 6.4 years, on average, after cessation of treatment. Patients were divided into two groups--those with a small amount of hypermetropic anisometropia, where the spherical equivalent difference between the eyes ranged between 0 and +1.50 dioptres, and those with a large amount of hypermetropic anisometropia, where the difference was +1.75 dioptres or greater.

RESULTS

Deterioration of visual acuity after cessation of occlusion treatment occurred in 51% of the patients in the group with a small amount of anisometropia and in 75% of the patients in the group with a large amount. At cessation of treatment, the average visual acuity in both groups was 20/40+. At the long term follow up examination, however, the average visual acuity was 20/40- and 20/70, respectively. This difference was statistically significant.

CONCLUSIONS

Hypermetropic anisometropia greater than 1.50 dioptres appears to be a risk factor for deterioration of visual acuity in the long term, following treatment of amblyopic eyes by occlusion of the fellow eye.

Treatment for amblyopia: results using occlusive contact lens

PURPOSE

Amblyopia treatment occasionally is complicated by patch intolerance, resulting in a poor outcome. Therefore, a prospective study was designed to examine the efficacy and safety of using occlusive contact lenses in the treatment of amblyopia.

METHODS

Twenty-five patients, aged 2.5 to 9.5 years, who were using an opaque hydrogel contact lens for the treatment of amblyopia, were followed prospectively.

RESULTS

Overall, 92% of patients improved at least one line of visual acuity. Eight patients improved > or = 2 octaves and 12 other patients improved > or = 1 octave. In three patients, the change in visual acuity was < 1 octave. Complications were seen in nine patients: contact lens irritation in five; poor contact fit in three; and peeking around the lens in one. The recurrence rate was high. In 11 of 25 patients, amblyopia rapidly returned to a reduced level when the contact lens was discontinued.

CONCLUSIONS

Occlusive contact lenses can be used in treating amblyopia in children. This treatment is ideal in patients who were patch-intolerant and failed with conventional treatment. Patients should have close follow up, however, to monitor any anterior segment complications from contact lens use and to identify the patients in whom amblyopia recurs.

Preschool vision screening: rationale, methodology and outcome

Although population outcome studies support the utility of preschool screening for reducing the prevalence of amblyopia, fundamental questions remain about how best to do such screening. Infant photoscreening to detect refractive risk factors prior to onset of esotropia and amblyopia seems promising, but our current understanding of the natural history of these conditions is limited, thus limiting the prophylactic potential of early screening. Screening for strabismic, refractive and ocular disease conditions directly associated with amblyopia is more clearly proven, but the diversity of equipment, methods and subject populations studied make it difficult to draw precise summary conclusions at this point about the efficacy of photoscreening. Sensory-based testing of preschool-age children exhibits a similar combination of promise and limitations. The visual acuity tests most widely used for this purpose are prone to problems of testability and false negatives. Moreover, the utility of random-dot stereograms has been confused by misapplication, and new small-target binocularity tests, while attractive, are as yet inadequately field-proven. The evaluation standard for any screening modality is treatment outcome. However, variables in amblyopia classification and quantitative definition differences, timing of presentation, nonequivalent treatment comparisons, and compliance variability have been uncontrolled in virtually all extant studies of amblyopia treatment outcome, making it difficult or impossible to evaluate either the relative efficacy of different treatment regimens for amblyopia or the effects of age on treatment outcome within the preschool age range. The latter issue is a central one, since existence of such an age effect is the primary rationale for screening at younger rather than older preschool ages. The relatively low prevalence of amblyopia makes it difficult to achieve a high screening yield in terms of predictive value, but functionally increasing prevalence by selective screening of high risk populations causes further problems. Unless a "supertest" can be devised, with very high sensitivity and specificity, health policy decisions will be required to determine which of these two characteristics should be emphasized in screening programs. Performance of screening tests can be optimized, however, with adequate training, perhaps via instructional videotapes.