Macular Ganglion Cell Complex Reduction Preceding Visual Field Loss in a Patient With Chiasmal Compression With a 21-Month Follow-Up: Comment

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We appreciate Dr. Montiero's comments sharing his experience with ganglion cell loss from compressive lesions. We did observe that patients can have normal visual fields and no symptoms, despite what seems to be rather severe ganglion cell complex (GCC) thinning on optical coherence tomography (OCT) both before and after decompression of the chiasm (1). However, patients can have visual field loss and symptoms before structural changes are observed from axonal compression or, more specifically, because of reversible distortion of the nodes of Ranvier (2). Therefore, visual field testing in patients with compressive lesions remains very important. Because OCT is an easier test for patients and is objective, we believe that OCT should also be used in the detection of compressive lesions and during follow-up of affected individuals, especially because we and Dr. Montiero have shown that GCC loss can precede visual field loss.
In Dr. Horton's comments about our article, he stated that conventional visual field testing may not be sensitive enough to detect functional changes associated with ganglion cell damage (3). We agree, but we also have been impressed with the possibility that, despite what seems to be significant GCC loss, there are enough ganglion cells remaining, especially in the macula, for patients to retain excellent visual function. In other words, the GCC loss may not have reached a “tipping point” as suggested by Dr. Costello, who also commented on our study (4). This seems to occur in other conditions, including Leber hereditary optic neuropathy in which, despite what seems to be almost complete loss of macular ganglion cells, some patients, over time, may regain excellent visual acuity and visual fields.

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