Background: the prevalence of visual impairment is known to be higher in a diabetic population than in a non-diabetic population. How much of this visual impairment may be attributed to uncorrected refractive error is unclear. This study examined the prevalence of visual impairment in a Hong Kong diabetic population to determine the proportion of the visual impairment that could be corrected with prescription spectacles.
Methods: patients with type 2 diabetes mellitus (T2DM) were recruited as subjects for this study. All subjects underwent a standardised diabetic retinopathy screening that included measurement of presenting distant vision, biomicroscopic examination of the anterior eye and a retinal examination. For those subjects whose visual acuity was worse than 6/9.5, autorefraction was performed. In this study, we classified visual impairment into three categories: no visual impairment (visual acuity in the better eye better than or equal to 6/18), mild visual impairment (visual acuity in the better eye between 6/18 and 6/60) and severe visual impairment (visual acuity in the better eye less than or equal to 6/60).
Results: for the 2,301 subjects who participated in this study, the mean age at examination was 61.4 ± 10.5 years (range, 23 to 92 years). Regarding visual acuity, 11.3 per cent (259/2,301) of subjects had visual impairment with 10.6 per cent being mild (244/2,301) and 0.7 per cent severe (15/2,301). After correction with a prescription determined by autorefraction, the prevalence of visual impairment dropped to 4.0 per cent (91/2,301). Nearly 70 per cent (168/259) of visual impairment was correctable by prescription spectacles and 21.6 per cent (56/259) of subjects were likely to benefit from cataract surgery.
Conclusion: for our sample of diabetic patients, nearly 70 per cent of the visual impairment could be remedied by a spectacle correction. In the care of the diabetic eye, eye-care providers should not focus solely on diabetic retinopathy. The quality of life in people with T2DM can be improved simply by eliminating uncorrected refractive errors.