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Optical coherence tomography may have a role in providing an honest assessment of visual potential for patients who have undergone surgery for visual loss due to compression.
In a case presented by Neil Miller, MD, Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, a 63-year-old man had poor vision in his left eye. Six months later he presented with complaints of reduced libido. The vision was 20/20 in the right eye and 20/100 in the left eye, in which there was a relative afferent pupillary defect. The visual field in that eye was very abnormal. The right eye had a superior temporal defect.
Endocrine analysis showed evidence of panhypopituitarism with a diagnosis of a nonsecreting pituitary adenoma compressing the anterior visual pathway. The tumor was resected with no improvement in the vision in the left eye-leaving a question as to whether any further surgery (such as a craniotomy), steroid treatment, or radiation treatment might improve vision further.
"[The ophthalmologist's role in a case such as this is] to provide honest assessments of the visual potential in these patients, and more importantly, to preserve their hope for potential improvement in vision," said Dr. Kardon, professor of ophthalmology and director of neuro-ophthalmology, University of Iowa; professor of ophthalmology, Surgery Division, Veterans Administration Hospital, Iowa City, IA; and director of the Iowa City VA Center for Prevention and Treatment of Visual Loss.
He discussed the mechanisms of visual loss in patients who had undergone surgery for decompression of the anterior visual pathway, but who did not have postoperative improvement of visual acuity in eyes in which the visual acuity was severely affected when compressive optic neuropathy was diagnosed.
In these patients, the tumor compressing the visual pathway causes conduction block of the nerve fiber, which if relieved may allow the nerve to function again. There is also nerve demyelination with chronic compression, which may return to normal over time, and the possibility of ischemia to the nerve. There can also be axon loss, in which case visual function will not completely return to normal over time, he explained.