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Hiroko Terasaki, Yozo Miyake, Ryoji Nomura, Chang-Hua Piao, Kenji Hori, Takashi Niwa, Mineo Kondo; Focal Macular ERGs in Eyes after Removal of Macular ILM during Macular Hole Surgery. Invest. Ophthalmol. Vis. Sci. 2001;42(1):229-234.
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purpose. The removal of the internal limiting membrane (ILM) for traction
maculopathy has recently been advocated. However, it is generally
believed that the ILM plays an important role in retinal function,
because it is the basal lamina of the Müller cells that are
involved in the generation of the electroretinogram (ERG) b-wave. To
date, there has been no objective assessment of retinal function on
removing the ILM. In this study, the changes of each component of the
focal macular electroretinograms (FMERGs) were investigated in eyes
before and after the ILM was removed in the macular area during surgery
for idiopathic macular holes (IMHs).
methods. FMERGs were elicited by a 15° stimulus centered on the fovea and
monitored by an infrared fundus camera. FMERGs were recorded from 49
eyes of 48 patients with IMHs before and 6 weeks after anatomically
successful macular hole surgery. Whether an eye had or did not have the
ILM removed was randomly determined. The ILM was removed in 30 eyes
(ILM-off group) and 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 eyes 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 oscillatory 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
increased significantly 6 months after surgery (P =
0.0093, P = 0.0019, P = 0.0024,
respectively, paired t-test). In the ILM-off group, the
a-wave amplitude 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-wave 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 after
surgery suggests an alteration of retinal physiology in the macular
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