Image quality of great value in glaucoma screening devices

FT. LAUDERDALE, Fla. — Image quality should be taken into account when assessing discriminatory output of glaucoma imaging devices, said Kyung Rim Sung, MD here at the International Society for Imaging in the Eye meeting.

In a study of 164 eyes of 164 patients enrolled in the Advanced Imaging for Glaucoma Study, image qualities were evaluated to compare the discrimination capabilities between healthy and glaucomatous eyes examined with scanning laser polarimetry (GDx VCC), optical coherence tomography (OCT) and confocal scanning laser ophthalmoscopy (HRTII).

“Diagnostic accuracy of imaging devices can be affected by many factors,” Dr. Sung said.

Those factors include quality of image, quality of analysis and the individual variance of structure, such as optic disc size, physiological cupping and peripapillary atrophy, she said.

In this study, 102 of the patients were normal, and 62 were confirmed glaucoma patients. All of the patients were scanned with all three of the imaging devices used.

The quality parameters for each scan were quality score for GDx, signal strength for OCT and standard deviation for HRT. The discriminatory parameters were nerve fiber indicator for GDx, nerve fiber layer for OCT and Moorfields regression analysis classification for HRT.

Based on manufacturers’ suggested cut-off criteria for image quality, the GDx had 22.6% poor quality scans; the OCT had 1.2% poor quality scans, and the HRT produced 10.4% poor quality scans, Dr. Sung said.

“To our surprise the results were different among machines,” Dr. Sung said.