A prospective study was carried out to test the null hypothesis that there is no additional benefit to be gained from second eye cataract extraction. Twenty-nine patients with unilateral cataract but contralateral pseudophakia completed a questionnaire enquiring into their visual disability and underwent testing of monocular and binocular visual acuity, contrast sensitivity, glare disability, fusion and stereopsis. These tests were repeated 4 months after second eye cataract extraction and lens implantation. Patients universally considered their vision to have been improved by second eye surgery and the prevalence of all symptoms were significantly reduced by this procedure. Normal binocular summation and stereopsis were restored following second eye cataract extraction. Symptomatic patients may benefit from second eye cataract extraction with lens implantation.