osbert chan

The major types of ametropia and visual problems for Hong Kong Chinese and Caucasian children are different. Consequently, the referral criteria developed for Caucasian children may not be applicable to Hong Kong children. Results of our study suggested that the referral criteria for Hong Kong children should be set as hyperopia of ≥+ 2.0 D, myopia of ≥ 1.0 D, anisometropis of ≥ 1.0 D and anisometropia of ≥ 1.25 D. Sensitivity using only these criteria for abnormal refraction in identifying children with amblyopia. Esotropia, exotropia and subnormal vision (< 6/12) was respectively 100%, 84.6%, 45.2% and 95.7%. The overall sensitivity for the identification of visual problems was 86.1 % and the overall specificity was 76%. If a cover test or a Hirschberg test was introduced into the screening battery so that all the strabismic cases were identified, the overall sensitivity would increase to 98.6%.

Twenty-seven Hong Kong Chinese children, aged 3 to 5 1/2 years, were recruited in this study to evaluate the relation between refractive error as measured retinoscopically before and after cycloplegia using cyclopentolate 1%. The noncycloplegic spherical refractive error of these children ranged from -0.75 to +2.50 D and approximately 98% of the Hong Kong pre-school children have a manifest spherical error within this range. The cycloplegic refractive error can be approximated by multiplying the spherical component of the manifest error by 1.45 and adding +0.39 D to the product, while keeping the astigmatic power and axis unchanged. Cyclopentolate 1% requires more time to produce mydriasis and cycloplegia in eyes with heavily pigmented irides; however, its final effect on refractive error is apparently independent of iris pigmentation and depends on the amount of spherical refractive error present.

Five hundred and seventy Chinese children aged between 36 and 65 months were recruited for refractive examination. The results show that both the spherical and cylindrical components of the refractive error tend to decrease with increasing age, although the changes were not statistically significant. The results of the present study, together with those of earlier studies carried out on Hong Kong Chinese children of different ages, show a pattern in the change of refractive errors in local children during the first 17 years of life. The combined results show that the average spherical refractive error decreases rapidly in hyperopic power during the 1st and the 6th to the 10th years of life; the astigmatic power decreases rapidly in the 1st year of life and remains thereafter rather constant until the age of 17 years.