CSLO helps predict progression to glaucoma, research finds

La Jolla, CA-Many optic disc measurements obtained using confocal scanning laser ophthalmoscopy (CSLO) can help predict the development of primary open-angle glaucoma (POAG) in patients with ocular hypertension, according to the recently published results of an ancillary study to the National Eye Institute (NEI)-sponsored Ocular Hypertension Treatment Study (OHTS).

During up to 8 years of follow-up, 41 eyes of 36 patients included in the ancillary study developed POAG. Results of multivariate analyses showed many baseline CSLO topographic optic disc measurements were independently associated with the development of POAG. Those parameters included larger cup-to-disc area ratio, mean cup depth, mean height contour, cup volume below reference, and reference plane height. For several other CSLO topographic measurements, including rim area, rim area to disc area, rim volume above reference, and HRT classification, smaller values at baseline were significantly associated with the development of glaucoma.

CSLO parameters

Many of the CSLO parameters offered negative as well as positive predictive value. For example, considering the MRA classifications found to be significantly associated with the development of glaucoma, 14% to 40% of patients with values outside of normal limits for those parameters went on to develop POAG. About 95% of those whose MRA indexes were within normal limits at baseline did not develop POAG.

"Within the last few years, there has been an explosion in the use of imaging devices for assessing glaucomatous structural changes, including CSLO (HRT) as well as scanning laser polarimetry (GDx-VCC, Carl Zeiss Meditec) and ocular coherence tomography (Stratus OCT, Carl Zeiss Meditec). However, it has not been clear what benefit these instruments have in clinical practice," said Robert N. Weinreb, MD, principal investigator for the CSLO Ancillary Study. "For the first time, these results from OHTS validate in the setting of an appropriately designed, prospective clinical trial that an imaging instrument has a role in predicting the development of glaucoma among persons with ocular hypertension."

"The OHTS showed that baseline stereophotograph cup-disc ratio estimates along with IOP, corneal thickness, and visual field indices were associated with the development of glaucoma," said Linda M. Zangwill, PhD, co-investigator for the CSLO Ancillary Study. "Similarly, these first published results from the CSLO Ancillary Study show that objective assessment of the optic nerve head using CSLO is also associated with the development of glaucoma.

"Analysis of data from longer follow-up will help to estimate better the predictive accuracy of the CSLO measurements, but we believe the information that this technology provides will be helpful when used in conjunction with other clinical and ocular features for identifying patients at risk for progress from ocular hypertension to glaucoma," Dr. Zangwill added.

Dr. Weinreb, who is Distinguished Professor of Ophthalmology, University of California, San Diego, and director of the university's Hamilton Glaucoma Center, first began developing technology for evaluating the optic disc and retinal nerve fiber layer based on the principle of confocal imaging more than 20 years ago. The National Institutes of Health funded that research, and the technology was later commercialized as the HRT. When the OHTS protocol was being developed, Dr. Weinreb approached the study organizers with the idea of including CSLO measurements.