Commentary: Considerations regarding area of internal limiting membrane peeling during macular hole surgery

The internal limiting membrane (ILM) peeling is a recognised technique for management of various vitreoretinal disorders like macular holes, myopic foveoschisis, epiretinal membranes, vitreomacular traction, recalcitrant diabetic macular edema, retinal detachment, etc.[1] A Cochrane review in 2013 has concluded favourable role of ILM peeling in management of stages 2, 3 and 4 idiopathic macular holes.[2] ILM peeling causes reduction of tangential traction at fovea, increased retinal compliance and stimulation of retinal glial cells secondary to trauma to Muller cell end feet[2] as well as thickening of outer and middle inner retinal inner layers at macula. Papillofoveal distance is also shortened.[3,4] These changes are postulated to help in realignment of the external limiting membrane and photoreceptor restoration leading to macular hole closure and visual recovery. There is also thinning of retinal nerve fibre layer (RNFL), ganglion cell layer and inner plexiform layer, which is more marked in temporal side of the fovea than nasal. It could be attributed to instrument trauma or Brilliant Blue G (BBG) dye exposure.[3]

Various factors have been described in the literature to prognosticate the success of macular hole surgery. Intraoperative area of the ILM peel can also be considered as an important predictor.[5,6] In one of our studies, we have found a statistically significant association between size of ILM peel and anatomical closure of macular hole.[5] There is no general consensus which states the optimal extent of ILM area to be peeled for best surgical outcomes in macular holes. Various authors have tried to aim different sizes of ILM peel ranging from 0.5 disc diameters (DD) to 3 DD around centre of fovea to obtain favourable outcomes.[2] In our study, we demonstrated ILM peel of size >2 DD achieved anatomical closure in 95% cases (P = 0.04). We were able to assess the size of peel easily by taking distance from temporal margin of optic disc to centre of fovea. A larger area of peeling would ensure better outcomes. The present study has also elucidated the potential benefit of larger ILM peel (>3 DD) in large macular holes (>400μ) as well as another group (<400μ).[7] The authors have also described a novel method of real-time intraoperative assessment of area of ILM peel for favourable outcomes.

While achieving a large area of ILM peel, there can be chances of RNFL haemorrhages, which may result in visual field defects or iatrogenic retinal break formation.[1,6] Muller cells can be damaged causing structural breakdown leading to complications like dissociated optic nerve fiber layer and paracentral hole formation.[1] There may be a reduction of retinal sensitivity associated with relative or absolute microscotomas.[8]

There are also other well-established ways to increase macular hole closure such as inverted ILM flaps or use of adjuncts (like autologous platelets). Proper preoperative planning, meticulous use of vital dyes and surgical instruments along with gentle handling of tissues should be tried for achieving good outcomes in macular hole surgery.