As regular readers know, we don’t often run guest editorials, but from time to time important topics arise that demand broad attention. Don Hood is the James F. Bender Professor of Psychology and Professor of Ophthalmic Science in Ophthalmology at Columbia University. He currently serves as Editor-in-Chief of Investigative Ophthalmology and Visual Science and on the Editorial Board of the Journal of Glaucoma. Don received the Research Excellence Award from the Optometric Glaucoma Society in 2014 and is among the world’s brightest minds in understanding visual system function and physiology. He has a special interest in glaucoma. What Don has to say is very important:


On Improving Our Ability to Detect Glaucoma

Over the past decade, my laboratory has been able to show that macular vision is affected early in the glaucomatous process. This finding goes against conventional wisdom, which holds that that glaucoma affects the peripheral field first and the macular region last. Our work has demonstrated that arcuate field defects near fixation are common, can affect reading and often progress toward fixation. Most importantly, macular field defects can be missed by 24-2 visual fields as well as by conventional OCT scans of the optic disc and simple analyses of peri-papillary circle scans of the retinal nerve fiber layer (RNFL).

Today, the best OCT test for detecting macular glaucomatous damage is a cube scan that includes the central ±10° (corresponding approximately to a 6mm x 6mm square of retina). Thus, we believe that best practice is to obtain OCT images of both the macula and the optic nerve and surrounding tissues. In some OCT instruments, this requires two cube scans, one centered on the macula and one centered on the disc, while in others the scan is wide enough to include both disc and macula. In either case, our OCT instruments are up to the task.

However, it still is important to confirm and stage glaucoma with visual fields. The commonly used 24-2 test pattern of the Humphrey Visual Field Analyzer (Carl Zeiss Meditec) may miss and/or underestimate macular damage simply because its test points are spaced 60 apart, leaving room for scotomas to fall between the points. The Humphrey 10-2 test pattern covers the central 100 with its points spaced 20 apart and can typically detect these defects. But, here is the problem: Because of testing time and billing considerations, many clinicians find it difficult to obtain both a 24-2 and 10-2 visual field. Based upon our research, we and colleagues have helped Zeiss select points to add to the 24-2 to create a 24-2C pattern that would test both the central and macula region. Now we can have our 24-2 and pick up most macular defects as well!

Or so we thought. The latest word from Zeiss is that the 24-2C will only be available on the new HFA3. Perhaps Zeiss does not yet understand the importance of the 24-2C to their customers and to our patients. Recent knowledge has improved our ability to detect glaucomatous damage, and it is important that as many patients as possible enjoy the benefits of this improvement. Zeiss should reconsider making the 24-2C test pattern available on older models of the HFA. 

- Don Hood, PhD

Arthur B. Epstein, OD, FAAO Chief Medical Editor artepstein@optometricphysician.com