Case 13-2. Focal Nerve Fiber Layer Defect
A 72-year-old woman with normal tension glaucoma had undergone laser trabeculoplasty four months earlier in her left eye and was taking timolol 0.5% twice daily. The intraocular pressure in this eye was 13 mm Hg and the visual acuity was 20/25. Slit-lamp examination showed an open angle throughout 360°. Ophthalmoscopy (A) revealed a moderately cupped disc with an attenuated neuroretinal rim temporally. The nerve fiber layer reflex (B) displayed a focal reduction in the superotemporal area. A Humphrey visual field (D) revealed an inferior arcuate scotoma consistent with the nerve fiber laver defect and an earlv superior nasal step as well.
A 3.4 mm diameter circular scan (E) around the optic disc delineated focal thinning of tiie superotemporal nerve fiber layer consistent with the clinically observed focal nerve fiber layer defect. The depression appeared to arise from both the superficial and deep margins of the nerve fiber layer and reached a minimum thickness of 50 (Am in the image. The average nerve fiber layer thickness at 1:( 0, determined by the computer, was correspondingly reduced to 87 jim.
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