The frequency of amblyopia among visually impaired persons

To investigate the frequency of amblyopia among visually handicapped patients.

The study is a retrospective investigation of all living patients registered in four Visual Rehabilitation Centres in a region in southern Sweden. The area's total population numbered 865,612 persons of whom 11,365 were registered as visually handicapped (with visual acuity < or = 0.3 in the better eye).

Amblyopia was the main cause of decreased visual acuity in one eye in 1.72% (195 of 11,365) of the patients. The average age of the patients with amblyopia was 69 years (9-95 years) and 28.2% of these patients were less than 65 years old (the age for retirement in Sweden). The median visual acuity in the amblyopic eye among these patients was 0.1. The median visual acuity in the nonamblyopic eye was 0.2. The most common cause of decreased vision in the nonamblyopic eye was macular degeneration (39.5%). Bilateral amblyopia was present in 13 (6.7%) of the amblyopic patients. By comparing this study with earlier studies, we can calculate that about 1.2% of the persons with amblyopia 0.3 or lower will eventually become visually handicapped.

A small but considerable number of patients who attend the Visual Rehabilitation Centres have amblyopia as a cause of their visual impairment. Since amblyopia can be treated if detected in childhood, later visual rehabilitation of these patients can be avoided or delayed, thereby reducing rehabilitation costs for society.