A three-port standard pars plana vitrectomy was performed by a single surgeon using a 23-gauge vitrectomy system, either Associate®(Dutch Ophthalmic Research Center. Inc., Zuidland, The Netherlands) or Accurus®(Alcon Laboratories Inc., Fort Worth, USA), with one step scleral tunnel incision. In all cases, the peeling of the internal limiting membrane, approximately 1 disc diameter area from center of MH was conducted without assistance of dyes followed by complete fluid-gas exchange using 25% sulfur hexafluoride gas. Combined cataract surgery was performed in patients with visually significant cataracts or with incipient cataract in the subjects older than 60 years. All patients were instructed to maintain a face-down position for at least 7 days postoperatively.

the spectral domain optical coherence tomography scannings were performed at first postoperative visit, 1 month, 2 months, and 6 months after macular hole surgery. The inter-outer plexiform layer distance was measured based on optical coherence tomography images at defined time points

Best-corrected visual acuity was measured using early treatment diabetic retinopathy study chart at defined time points

The degree of metamorphopsia was measured using Metamorphopsia-chart at defined time points

The horizontal percent asymmetry was calculated as (nasal distance - temporal distance)/(nasal distance + temporal distance). The vertical percent asymmetry was also calculated as (superior distance - inferior distance)/ (superior distance + inferior distance.

The percent asymmetry was calculated as (horizontal inter-outer plexiform layer distance - vertical inter-outer plexiform layer distance)/(horizontal inter-outer plexiform layer distance + vertical inter-outer plexiform layer distance).