To evaluate the causes of secondary macular hole after vitrectomy and the possibility of their prevention.

27 patients (28 eyes) who experienced macular hole formation after vitrectomy were reviewed retrospectively. Age, sex, operation methods, duration between the vitrectomy and the secondary macular hole surgery and causes of the primary vitrectomy were recorded. Best-corrected visual acuity (BCVA) before and after primary vitrectomy; preoperative and postoperative macular findings with optical coherence tomography and fundus examination; and BCVA before and after macular hole surgery were analyzed.

Of the 2945 eyes that had undergone vitrectomy, 28 eyes (0.96%) experienced macular hole formation. As causes of primary vitrectomy, 12 eyes had proliferative diabetic retinopathy, 6 eyes had rhegmatogenous retinal detachment, 2 eyes had branch retinal vein occlusion, 3 eyes had age-related macular degeneration and 5 eyes had trauma such as eyeball rupture or intraocular foreign body. The mean duration between primary vitrectomy and macular hole formation was 20.4 months (4 days-115 months). The estimated causes of macular hole formation included cystoid macular edema (CME) (n = 13), thinning of the macula (n = 6), thickening of internal limiting membrane or recurrence of preretinal membrane (PRM) (n = 7), recurrence of subretinal hemorrhage (n = 1) and macular damage during vitrectomy (n = 2). Final BCVA after macular hole surgery decreased in most cases compared to BCVA before macular hole formation except in 7 eyes (25%).

Close observation of the macula after primary vitrectomy especially in eyes with continuous CME, and recurrent PRM and proper management on them including timely removal of the tangential traction force are necessary for preventing macular hole formation. In addition, surgeons should make efforts not to exert excessive tractional force on the macula to avoid iatrogenic damage during removal of the preretinal membrane.