Abstract
Purpose: :
An important, though not well recognized, cause of thyroid related optic neuropathy is stretch optic neuropathy. Of the few reported cases, none has documented the rate of vision loss due to continuous stretching of the optic nerve. Animal models have provided information on the tensile strength of the optic nerve, but to our knowledge no in vivo studies of the tensile strength of the human optic nerve have been reported. We present 3 cases of stretch optic neuropathy, one of which provided a unique opportunity to quantify and estimate the rate of vision loss from progressive stretching of the optic nerve.
Methods: :
Retrospective chart review of 3 cases of stretch optic neuropathy.
Results: :
All cases presented with blurry or spotty vision. Best corrected visual acuity ranged from 20/20 to 20/40. Automated perimetry showed arcuate scotoma visual field defects. The range of proptosis was 24 to 27 mm on Hertel exophthalmometry. Ocular motility was normal. Two cases had dot hemorrhages in the fundus simulating venous stasis retinopathy. Computed tomography showed thin extraocular muscles and expanded orbital fat volume. Orbital decompression improved the visual function. One case had progressive visual field loss over a 9-month period, providing a unique opportunity to quantify and estimate the rate of vision loss from progressive stretching of the optic nerve to complete blindness to be 775 days from onset of visual symptoms.
Conclusions: :
Stretch optic neuropathy is an infrequent, but potentially reversible, cause of visual loss and blindness from thyroid associated optic neuropathy.
Keywords: neuro-ophthalmology: optic nerve • visual impairment: neuro-ophthalmological disease • visual fields