Incidence of idiopathic full-thickness macular holes in fellow eyes. A 5-year prospective natural history study.

Purpose: This study aimed to determine the incidence of idiopathic full-thickness macular hole (FTMH) in normal fellow eyes and to evaluate the role of electrodiagnostic and psychophysical tests in identifying eyes at risk.
Patients and Methods: A prospective longitudinal natural history study of a cohort of patients with unilateral holes and normal, asymptomatic fellow eyes without posterior vitreous detachment was conducted. Subjects underwent baseline examination, pattern reversal electroretinography, electro-oculography (EOG), and color contrast sensitivity (CCS) testing for protan, deutan, and tritan thresholds and were recalled for clinical examination at 18 months and 5 years.
Results: At baseline, 114 patients were examined. Eighty were available for review at 18 months, of whom 6 had full-thickness macular holes develop in the fellow eye. At 5 years, 67 of the remaining 74 patients who had not developed holes at 18 months were re-examined and a further 5 were found to have holes develop in the fellow eye. A posterior vitreous detachment without hole formation had developed in 20 fellow eyes at 5 years. Although mean pattern reversal electroretinography and EOG responses were within normal limits in affected and fellow eyes at baseline, mean CCS protan, deutan, and tritan thresholds were elevated significantly in affected eyes at baseline (P = 0.0001). Unaffected fellow eyes showed normal mean protan and deutan thresholds, but significantly elevated mean tritan thresholds (P = 0.01) at baseline. Mean tritan CCS loss was, however, similar in fellow eyes in which holes later developed and in fellow eyes in which holes did not.
Conclusions: The Kaplan-Meier estimated risk of fellow eye involvement is 15.6% (range, 8.4%-22.3%; P = 0.05) at 5 years. Although electrodiagnostic and psychophysical testing was not predictive of fellow eye involvement, tritan CCS loss at baseline, in apparently normal fellow eyes, may indicate subclinical foveal dysfunction, the nature of which is unclear.