Amblyopia is a condition of decreased vision associated with strabismus, refractive errors, anisometropia and cataract. Maturation of visual pathways is affected in amblyopia. Amblyopia occurs without any structural abnormality. Amblyopia is present in 1.6 to 3.6% population. It is a major cause of decreased vision in infancy. Visual cortex neurons are affected in amblyopia, which occurs mostly in first 2 years of life. Amblyopia can cause visual disability if not treated before the age of 8 years. Management consists of correcting refractive error, eye patching and atropine eye drops to the fellow eye. The ideal treatment is occlusion of fellow eye with fabric patch. Improvement with occlusion therapy is present in 80% within 6 weeks. 2-6 hours of patching can improve visual acuity under 13 years of age.
Occlusiont herapy is an effective and better
treatment for improvement vision in amblyopia.
MATERIALS AND METHODS:
This descriptive case series study was conducted in Ophthalmology department of Jinnah Postgraduate Medical Centre Karachi from 1st January 2018 to 1st January 2019. A total of 68 patients aged between 5 to 12 years with amblyopia were included in the study based on inclusion and exclusion criteria after informed consent from their parents. Proformas were filled out. Ocular examination included decreased Best Corrected Visual Acuity with snellen’s chart of less than 6/6, anterior segment examination with slit lamp bio microscopy which is normal in amblyopia and posterior segment examination by fundoscopy which is also normal in amblyopia. Amblyopia was diagnosed after examination. Occlusion therapy by eye patching was given to amblyopic children according to their age for 2 to 6 hours per day for 6 weeks. Final outcome was considered after 6 weeks at which time presence of improvement in visual acuity of two or more snellen line after occlusion therapy was labeled as yes and absence of improvement was labeled as no. Confounding factor such as patient compliance was overcome by appropriate counseling.
Data analysis procedure: The database developed on the basis of the filled proformas was analyzed using SPSS version 20. Frequency and percentages were calculated for qualitative variables including gender, Best Corrected Visual Acuity (before and after eye patching), Occlusion time, Improvement in Visual Acuity after 6 weeks of occlusion therapy. Mean and standard deviation was calculated for quantitative variables including age of the patient and duration of disease. Stratification was done to control effect modifiers like age, gender and duration of disease. Chi square test was applied. P-value of ≤ 0.05 was considered as significant.
Sixty eight patients with amblyopia were included in this study. There were 42(61.76%) children belonged to 5 to 7 years and 26(38.24%) were in 8 to 12 years of age as shown in figure 1.
The average age of the children was 6.96±1.96 years while mean duration of amblyopia and occlusion time was 7.38±1.09 months and 2.56±0.69 hours as shown in table 1.
Out of 68 patients, 26(38.24%) female and 42(61.76%) male as presented in figure 2.
Affected site of the patients is also shown in figure 3.
Frequency of best corrected visual acuity before and after the eye patching is presented in table 2.
Outcome in term of improvement in visual acuity after 6 weeks of occlusion therapy in amblyopic children is shown in table 3 and 85.29% (58 of 68) of patients demonstrated at least 2 lines of improvement in Visual acuity.
Stratification analysis of the patients was performed and seen that no significant change in improvement of visual acuity was observed with respect to age group, sex and duration of amblyopia as shown in table 3, 4 and 5 respectively.
Amblyopia is a reduced visual acuity (VA) caused by abnormal binocular interaction or visual deprivation during a sensitive period of visual development in early childhood. The incidence of amblyopia is reportedly at 3.5% worldwide, 1.6% - 3.5% in the United Kingdom and 2.0% - 2.5% in the United States. Its prevalence varies in different ethnic groups. Amblyopia was detected in 2.6% of Hispanic/Latino children and 1.5% of African-American children. The overall prevalence in Singapore was 0.35% with no racial difference among Chinese (0.34%), Malays (0.37%), and Indians. The principles of amblyopia treatment are to eliminate any obstacle in vision, correct refractive error, force the patient to use the poorer eye by penalization with atropine or by patching of the better eye, and lastly, surgery to treat the cause of the amblyopia, if applicable. These options may be used alone or in combination depending on the nature of amblyopia. The aim of amblyopia treatment is to improve visual acuity and to prevent or reverse vision impairment. With timely intervention, the reduction in visual acuity caused by amblyopia can be completely or partially reversed.[6,19] In our study to determine visual outcome after occlusion therapy, Sixty eight patients with amblyopia were included, 61.76% children belonged to 5- 7 years age group while rest 38.24% were in 8 to 12 years of age group. The average age of the children was 6.96±1.96 years. Out of 68 patients, 38.24% female and 61.76% were males showing predominance of male sex. Gopal Bhandari et al in their study also found that amblyopia was more prevalent in males than females (P=0.049 ) Woodruff et al in their study reported that Amblyopia occurs with equal frequency in boys and girls. There have been controversial debates on the concept that success of amblyopia treatment depends on patient’s age at initiation of the treatment.[22,12,23] Various studies have favored amblyopia treatment at age <6–7 years[22,24] but few studies have reported better outcomes in older children.[25,26] Our study results are also in concordance to the published literature where visual outcomes were independent of patient’s age; suggesting that amblyopia can be treated successfully beyond the age that is considered to be the critical period for the visual development. In our study, Amblyopia was diagnosed after examination. Occlusion therapy by eye patching was given to amblyopic children according to their age for 2 to 6 hours per day for 6 weeks. On determining the outcome in term of improvement in visual acuity after 6 weeks of occlusion therapy in amblyopic children, 85.29% of patients demonstrated at least 2 lines of improvement in Visual acuity showing occlusion therapy as an effective therapy for amblyopia. Our results are supported by many other studies. In a retrospective study of 246 children with amblyopia treated with occlusion therapy, successful outcomes (linear acuity 6/12 or better) were achieved in 85 percent of the children. The Amblyopic Treatment Study 2A conducted on 3-7 years of age group showed that patients with severe amblyopia had an improvement of 4.7 lines in those patched full time and for at least 6 hours. Similarly Amblyopic Treatment Study 2B also conducted on 3-7 years of age group showed a 2.4 line improvement in those with mild to moderate amblyopia when patched for 2-6 hours.
We conclude that Occlusion therapy is an effective and better treatment for improvement in vision in amblyopia, Hence a comprehensive vision screening program should be made over the course of childhood to detect amblyopia early enough to allow successful treatment to save the future generation from this life time visual disability. Patching is not always an easy task. Working with parents to increase their understanding of amblyopia and visual development and encouraging the use of positive reinforcement can greatly improve compliance and ultimately result in better visual outcomes