PURPOSE. The removal of the internal limiting membrane (ILM) for traction m
aculopathy has recently been advocated. However, it is generally believed t
hat the ILM plays an important role in retinal function, because it is the
basal lamina of the Muller cells that are involved in the generation of the
electroretinogram (ERG) b-wave. To date, there has been no objective asses
sment of retinal function on removing the ILM. In this study, the changes o
f each component of the focal macular electroretinograms (FMERGs) were inve
stigated in eyes before and after the ILM was removed in the macular area d
uring surgery for idiopathic macular holes (IMHs).
METHODS. FMERGs were elicited by a 15 degrees stimulus centered on the fove
a and monitored by an infrared fundus camera. FMERGs were recorded from 49
eyes of 48 patients with IMHs before and 6 weeks after anatomically success
ful macular hole surgery. Whether an eye had or did not have the ILM remove
d was randomly determined. The ILM was removed in 30 eyes (ILM-off group) a
nd was not removed in 19 eyes (ILM-on group). Six months after surgery, the
same examination was performed in 27 eyes of the ILM-off group and in 15 e
yes of the ILM-on group. The amplitudes and implicit times of the a- and b-
waves and the mean amplitudes and implicit times of the first three oscilla
tory potentials (OP1 to OP3) were compared before and after surgery within
and between the groups.
RESULTS. Visual acuity increased significantly after surgery in both groups
. In the ILM-on group, the amplitude of the a- and b-waves and the OPs incr
eased significantly 6 months after surgery (P = 0.0093, P = 0.0019, P = 0.0
024, respectively, paired t-test). In the ILM-off group, the a-wave amplitu
de and mean OP amplitudes were significantly larger 6 months after surgery
(P = 0.0077, P = 0.0030, respectively, paired t-test). The b-wave amplitude
, however, did not change significantly. The percentage increase in the b-w
ave amplitude 6 months after surgery was significantly higher in the ILM-on
group (44.0%) than in the ILM-off group (15.0%; P = 0.037, t-test).
CONCLUSIONS. The removal of the ILM had no adverse effect on visual acuity.
However, the selective delay of recovery of the FMERG b-wave 6 months afte
r surgery suggests an alteration of retinal physiology in the macular regio