The impact of bilateral or unilateral cataract surgery on visual functioning: when does second eye cataract surgery benefit patients?

Aim To examine the impact of bilateral or unilateral cataract surgery on visual functioning. Methods The Singapore Malay Eye Study is a population-based study of 3280 Singapore Malay patients aged 40―80 years, of which 3225 had data available for inclusion. Cataracts were graded from digital lens photographs according to the Wisconsin scale. Study subjects were categorised as having: bilateral cataract surgery performed; unilateral cataract surgery performed with minimal cataract in the fellow eye; unilateral cataract surgery performed with significant cataract in the fellow eye; and bilateral cataract. Visual functioning was assessed using the modified VF-9 scale culturally adapted for Singaporean individuals, validated by Rasch analysis. The overall Rasch-modified vision-specific functioning score was compared across the four groups after adjusting for confounders such as age, gender, ocular and systemic comorbidities. Results Persons with bilateral cataract had poorer visual functioning than those who had bilateral cataract surgery (mean visual functioning scores 3.38 vs 3.11, respectively, p=0.029). When compared with bilateral surgery, visual functioning improvements among patients with unilateral cataract surgery depended on the status of the fellow eye, with improvements only seen if the fellow eye had significant cataract (mean visual functioning scores 2.81 vs 3.25, p=0.019) or poor visual acuity (mean visual functioning scores 2.78 vs 3.25, p=0.018) after adjusting for confounders. Conclusions Bilateral cataract surgery was associated with greater visual functioning over unilateral cataract surgery when the fellow eye had a significant cataract or poor presenting visual acuity, supporting the current practice of second eye surgery depending on the fellow eye's cataract status and visual acuity.