Prevalence of visual disorders in Chinese schoolchildren.

We performed a vision screening of 1883 Chinese schoolchildren from 4 schools around Kuala Lumpur in June 1990. The group contained 1083-males and 800 females. Visual acuity, refractive error, oculomotor balance, and axial length were measured. The prevalence of myopia in Chinese schoolchildren was found to be 37% in the 6- to 12-year age group and 50% in the 13- to 18-year age group. Approximately 63% of the sample had unaided visual acuity of 6/6 or better and 24% had unaided acuity of 6/12 or worse. Six hundred twenty-five students (33%) failed the vision screening test and were referred for further examinations. The group which failed the vision screening test and had the highest rate of referral (46%) was the 11- to 12-year-old age group. The most common visual disorder was uncorrected myopia, accounting for 38% of the referrals (235 students). Only 26% of the sample were wearing a spectacle correction.

Progression of myopia in different ethnic groups in Malaysia.

A cross-sectional study on a normal clinical myopic population reveals that there is a difference in the pattern of myopic progression between Malays and Chinese in Malaysia. It shows that while myopia in Malays stays relatively constant throughout 10 to 50 years of age, myopia in Chinese progresses rapidly from 10 to 20 years of age, after which it starts to show hyperopic shift, reaching a level of myopia similar to that of Malays at around 35 years of age. In view of the above finding it is postulated that the difference in myopia between the two races may be due to excessive accommodation in Chinese, causing a temporary increase in crystalline lens power and hence an increase in myopia. Because the magnitude of myopia for both races for 10 +/- 1 years age group is relatively high, i.e. about -2.00 D, it is postulated that myopia in these ethnic groups may start much earlier than 10 years of age.

Effects of long-term visual display terminal usage on visual functions.

Since their rapid introduction into the workplace visual display terminals (VDT's) have been the source of a number of studies aimed at detecting effects on office workers. The published studies have been either short-term or cross-sectional, with one exception. The results have shown varying degrees of relation but by not having a comparable control group all have been limited in their value. We set out to monitor at regular intervals over a 2-year period specific visual functions that have been reported to be affected by VDT usage, and to compare VDT and non-VDT users in the same office environment. By assessing the VDT operators from the time the systems were introduced we have an accurate baseline to work from when assessing change due to the introduction of the VDT.

The effects of long-term VDT usage on the nature and incidence of asthenopic symptoms.

An opportunity arose in 1985 to become involved in a transition of working practice from hard copy to VDT. Over a two-year period, 161 VDT users and 65 control subjects in the same office environment were regularly and routinely examined for symptoms of asthenopia. The analysis of data shows that there are no significant differences in type, number and frequency of the work-related symptoms between VDT users and non-VDT users. It appears that reporting of symptoms within the group may be random, although certain symptoms do appear more frequently than others. Additionally, it appears that there is a significant difference between male and female users in the frequency of symptom reporting.

Effects of short-term VDT usage on visual functions.

An on-site comparative study was carried out on the effects of video display terminal (VDT) and non-VDT work on visual functions in two working populations in the same office environment. Both continuous VDT usage in a training situation over a few days and intermittent VDT usage in a normal working situation were assessed and particular attention paid to their effects on the refractive error of different refractive groups and for different age populations. Other visual functions measured were visual acuity (VA), accommodation, and convergence. Results show that VDT work does not have a significantly greater effect on visual function than non-VDT work.

Clinical evaluation of the Humphrey autorefractor.

A study is made of the accuracy and repeatability of the Humphrey autorefractor (HAR) objective refraction for different refractive groups as measured against subjective refraction. The value of the autofogging mechanism in objective refraction for different refractive groupings is assessed.