Eyeworld

EW GLAUCOMA 130 March 2015 by Tony Realini, MD, MPH, EyeWorld Contributing Writer may in fact be revealed as a paracen- tral arcuate defect on a 10-2 field. "I obtain a central 10-2 visual field on virtually all of my patients at some point," Dr. Liebmann said. "Even if it is normal, it serves as an important baseline for future assess- ment." Ronald Gross, MD, West Virgin- ia University, agreed. "In particular, "the foveal threshold value is a useful parameter to follow. A normal foveal threshold is a robust base- line," he said. David Greenfield, MD, Univer- sity of Miami, uses 10-2 perimetry as well. "I reserve its use for pa- tients with a visible field defect on 24-2 testing. The 10-2 expands the lesion," he explained, and makes it easier to follow over time. He cau- tioned, however, that perimetry soft- ware does not currently offer robust automated progression detection capacity for 10-2 fields. The strategy of manually comparing serial field tests is still necessary. Diabetic retinopathy Imagine a patient with advanced neovascular glaucoma who has pro- gressive changes on OCT and visual field testing. How do we determine whether her glaucoma or her diabet- ic eye disease is responsible for the changes? Diabetic retinopathy can certainly cause visual field defects. In addition, panretinal photoco- agulation (PRP) for proliferative retinopathy can cause significant field defects. To make matters more complicated, "PRP scars can enlarge over time, mimicking glaucoma progression," said Kouros Nouri- Mahdavi, MD, University of California, Los Angeles. Furthermore, he added that "imaging can also be misleading in these eyes due to the concurrent structural pathology." Young Kwon, MD, University of Iowa, agreed. "PRP does cause retinal nerve fiber layer thinning," which can mimic glaucoma progres- sion. Dr. Gross takes a pragmatic approach to these patients. "Assum- ing the patient has derived maximal benefit from PRP and vascular en- dothelial growth factor inhibition, there is nothing else I can do for her diabetic retinopathy. I can, howev- er, treat her glaucoma, and in such cases I advocate for advancing her glaucoma therapy because it's all I have to offer her." Dr. Greenfield added that ischemic eyes may have higher susceptibility to nerve damage from elevated IOP. Dr. Nouri-Mahdavi concluded, "In these eyes, the decision to ad- vance glaucoma therapy should be driven by the level of IOP current- ly achieved versus the target IOP desired." Optic nerve drusen Drusen of the optic nerve are clumps of protein and calcium within the substance of the optic nerve. They are typically benign and are noted as incidental findings. They can, however, affect both structural and functional testing of the optic nerve. When they occur in eyes with concurrent glaucoma, this can be problematic. "There is no question that drusen alone can cause visual field defects, and these defects can progress over time," Dr. Gross said. And because there is no straightfor- ward way to distinguish between glaucoma progression and drusen progression, he discusses the risks and benefits of treatment versus no treatment with the patient. Dr. Nouri-Mahdavi pointed out "there is no evidence that lower- ing IOP is helpful for optic nerve drusen." However, in eyes with both drusen and glaucoma, there may be a benefit. "An optic nerve with pre-exist- ing damage attributable to drusen may be more susceptible to further damage," said Dr. Gross. "In such eyes, our target IOP should probably be lower than for similar eyes with- out drusen." Dr. Liebmann supported this ap- proach. In the setting of drusen with a progressive field defect, the only 2 options are IOP reduction or doing nothing at all. "Perhaps the mechanism of drusen damage is similar to glauco- ma damage and may be amenable to IOP reduction," Dr. Liebmann said. "I would offer the patient treatment, given the very low risk of daily pros- taglandin analogue therapy." EW Editors' note: The physicians have no financial interests related to their comments. Contact information Liebmann: jml18@earthlink.net Gross: grossrl@wvuhealthcare.com Nouri-Mahdavi: nouri-mahdavi@jsei.ucla.edu Kwon: young-kwon@uiowa.edu Greenfield: dgreenfield@med.miami.edu Comorbidity confounds glaucoma progression detection How do we distinguish worsening of glaucoma from progression of concurrent ocular disease? D etecting progression of glaucoma is difficult enough. Visual field tests have high inter-test vari- ability. Optic nerve imag- ing platforms evolve so quickly that longitudinal studies establishing their ability to detect progression can be obsolete before they are com- pleted. And in the era of imaging and electronic health records—many with only rudimentary drawing capacity—clinical examination and documentation of optic nerve appearance may be a dying art. Even when these obstacles are eventually overcome, there is no consensus on the degree of change in either struc- tural or functional status of the optic nerve that is required to declare progression. Throw in a second ocular con- dition, such as age-related macular degeneration (AMD) or diabetic ret- inopathy, which can independently affect both structural and functional glaucoma tests, and a difficult task can seem almost impossible. How then are we to manage glaucoma in the presence of con- current eye disease? A panel of glaucoma specialists discussed this important clinical issue at the Amer- ican Academy of Ophthalmology's Glaucoma Subspecialty Day 2014 in Chicago. Macular degeneration Clearly, macular lesions associat- ed with AMD can produce central visual field defects. How impactful is this when assessing glaucoma in AMD-affected eyes? "Glaucoma is a macular dis- ease," said Jeffrey Liebmann, MD, Columbia University Medical Cen- ter. We typically think of glaucoma as a disease of the peripheral retina and peripheral visual field. However, "30% of the retinal ganglion cells reside in the macula," he explained, "and arcuate paracentral defects are common in glaucoma." A closer look may be beneficial. What appears to be a central defect on a 24-2 or 30-2 visual field strategy A preop view of extensive, proliferative diabetic retinopathy with tractional macular detachment and somewhat hazy view secondary to associated cataract Source: Tamer H. Mahmoud, MD

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