Temporal wedge defects common in glaucoma-related visual loss
Nearly half of patients with glaucoma-related mild central visual loss had defects in the far peripheral inferotemporal visual field, often in the form of temporal wedge or sector defects correlated with damage to the superior nasal optic disc nerve fiber bundles.
“We believe finding visual loss in the far peripheral field with OCT correlation could affect treatment decisions for glaucoma patients,” Michael Wall, MD, from the departments of ophthalmology and neurology at University of Iowa, College of Medicine, Iowa, and colleagues wrote in their study.
The study comprised 27 patients with mild visual loss due to glaucoma. The researchers designed a static automated perimetry test of the full visual field using Open Perimetry Interface (OPI). This test was used to determine if perimetric nerve fiber bundle defects existing outside 30 degrees correlate with areas of OCT retinal nerve fiber layer thinning in this population.
Wall and colleagues observed discrete temporal wedge defects on the OPI peripheral size V test in seven patients and more extensive inferior temporal loss including the temporal wedge defect region in six patients.
Additionally, they found two patients with thinning of the superior nasal disc without a visual field defect.
OCT data correlated best with the peripheral V test for eight patients, and the central 30-2 visual field tests correlated best for eight patients. The remaining patients’ central and peripheral tests correlated equally with OCT data.
“Since the presence and extent of visual field loss is an important factor in how aggressive treatment should be for glaucoma, finding a temporal sector defect with a normal or near normal central field would suggest more aggressive treatment could be warranted,” the researchers concluded. “Also, the presence of this nerve fiber bundle defect is useful for following patients as it may expand or deepen, suggesting more aggressive therapy is indicated.” – by Talitha Bennett
Disclosures: The authors report no relevant financial disclosures. The study was supported by a VA Merit Review Grant and an unrestricted grant to the Department of Ophthalmology from Research to Prevent Blindness, New York.
Perspective
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As the saying goes, everything old is new again.
Over the last several years, our awareness and understanding of glaucomatous damage of the macula has grown exponentially, driven at least in part by the evolution of OCT allowing accurate segmentation of the macular retinal ganglion cell layer. Although central involvement in early glaucoma was recognized over 40 years ago, conventional methods of assessment (primarily the 6° 24-2 and 30-2 automated visual field grids) were ill-suited to detect and monitor macular damage.
The same can be said for the temporal periphery. Noted for decades with kinetic visual field testing, temporal wedge defects at 25° to 30° eccentricity are poorly delineated by static perimetry. Through a custom interface, Wall and colleagues have demonstrated that nearly 50% of patients with early glaucoma manifest (primarily inferior) temporal field defects that correlate with structural change noted on OCT. Supporting this conclusion, Hood has identified the superior-nasal neuro-retinal rim, like the superior- and inferior-temporal, as being particularly vulnerable to glaucomatous damage.
In light of this, perhaps the enhancements to the AVF grid that began with the addition of central points should continue with inferior temporal testing, assessing another portion of the field that is critical for activities of daily living.
Reference:
Hood DC, et al. Invest Ophthalmol Vis Sci. 2013;doi:10.1167/iovs.13-1268.
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