Thirty-eight patients with excellent visual acuity but poor visual function as measured by contrast sensitivity and glare testing were studied. Clinical characteristics of opalescent nuclear cataracts, which have previously been described biochemically, are reported. The findings indicate that opalescent nuclear sclerosis is responsible for increased lenticular myopia and increased glare disability. This form of cataract responds rapidly to low power phacoemulsification of short duration, allowing a satisfactory surgical result.