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Cup shape measurement useful for evaluating optic nerve head changes associated with glaucoma
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Small optic nerve head variations associated with progression of retinal nerve fiber layer defects may be detectable using Heidelberg Retina Tomograph parameters, according to a retrospective study. However, most of the parameters correlated with detecting these defects differ from parameters used for detecting glaucoma.
Ville Saarela, MSc, and P. Juhani Airaksinen, MD, evaluated retinal nerve fiber layer (RNFL) photographs and HRT scanning laser measurements obtained for 68 eyes with open-angle glaucoma. Specifically, 34 eyes demonstrated progression of an RNFL defect over follow-up and 34 eyes showed no progression of RNFL defects.
The investigators found that the cup shape parameter was the only optic nerve head parameter that showed a statistically significant correlation with progression of an RNFL defect (P = .049).
The maximum cup depth and the linear cup-to-disc area ratio measurements were the best combination of two parameters included in the study (P = .009), the authors noted.
In addition, they identified maximum cup depth, the linear cup-to-disc area ratio and the horizontal cup-to-disc area ratio as the best combination of three parameters (P = .007).
Sensitivity and specificity values were 52.9% and 73.5% for the cup shape measure, 70.6% and 73.5% for the two-parameter combination, and 76.5% and 79.4% for the three-parameter combination.
The researchers found that the area under the receiver operating characteristic curve was greater for the three-parameter combination (0.753) than the two-parameter combination (0.724) and the cup-shape parameter (0.617), according to the study, published in the September issue of Acta Ophthalmologica.