Risk, causes, and outcomes of visual impairment after loss of vision in the non-amblyopic eye: a population-based study

Background Screening for amblyopia in early childhood is done in many countries to ensure that affected children are detected and treated within the critical period, and achieve a level of vision in their amblyopic eye that would be useful should they lose vision in their non-amblyopic eye later in life. We aimed to investigate the risk, causes, and outcomes of visual impairment attributable to loss of vision in the non-amblyopic eye. Methods For 24 months from July, 1997, national surveillance was done to identify all individuals in the UK with unilateral amblyopia (acuity worse than 6/12) who had newly acquired vision loss in the non-amblyopic eye, resulting in acuity of worse than 6/12 or visual-field restriction precluding driving. Information about participants was obtained at presentation and 1 year later. Participants were categorised as having socially significant visual impairment, or visual impairment, severe visual impairment, or blindness, in accordance with WHO taxonomy. Findings Of 370 eligible individuals, at presentation 104 (28%) had socially significant visual impairment, 180 (49%) visual impairment, and 86 (23%) severe visual impairment or blindness. The minimum risk of permanent visual impairment by age 95 years was 32•9 (95% CI 29•1–36•9) per 100 000 total population. The projected lifetime risk of vision loss for an individual with amblyopia was at least 1•2% (95% CI 1•1–1•4). Only 36 (35%) of 102 people previously in paid employment were able to continue. Interpretation In the UK, where screening for amblyopia is under review, risk of serious vision loss affecting the non-amblyopic eye and its results are greater than that previously assumed. Thus, in addition to the benefits of improved vision in the amblyopic eye, treatment of amblyopia during childhood is a potentially valuable strategy to prevent incapacitating vision loss later in life.