This prospective study compared the changes in the photopic negative response of the focal macular electroretinogram (fmERG) caused by retinal ganglion cell complex (GCC) thinning at the macula between patients with open angle glaucoma (OAG) and 12 months after successful macular hole repair surgery (MH). It has been shown that optical coherence tomography can determine the thickness of the GCC layer and that it can be used in diagnosing and monitoring progression in glaucoma patients. In addition, GCC thinning has been correlated to the functional loss of vision determined by visual field testing in glaucoma patients. In patients who have undergone successful macular hole repair surgery a dissociated optic nerve fibre layer appearance has been noted to occur. Thinning of the GCC layer has also been demonstrated in these patients, however, any functional visual correlation to this postoperative thinning remains controversial. In this study there was significant thinning of the GCC layer in both the OAG group and MH group compared to healthy controls. However, whilst the OAG group showed a significant reduction in fmERG response, there was no significant reduction in fmERG in the MH group compared to the control group. The results show that although the GCC layer is thinned in the MH the function of GCCs remains preserved. However, in the study limitations they postulate whether longer follow-up of these patients may then reflect a possible reduction in GCC function. The study shows an interesting finding of preservation of macular function demonstrated by fmERG in patients who have undergone macular hole repair surgery, where the GCC layer is thinner than control subjects in contrast to patients with early glaucoma who have similar GCC thinning but demonstrate functional loss through fmERG. However, it remains unclear as to why this difference occurs and further study is needed before any final conclusions can be made. – KB

Differences in functional loss associated with ganglion cell complex thinning between patients with glaucoma and postoperative macular hole.
Machida S, Tamada K, Ohzeki T, et al.
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Khadijah Basheer

Moorfields Eye Hospital, London, UK.

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