Abstract
Purpose: :
To determine a possible correlation between retinal nerve fiber layer defects as visualized on Optos P200C ultra widefield imaging system with retinal nerve fiber layer measurements on the GDx and visual field loss.
Methods: :
A retrospective analysis of Optomap images from the initial six month installation of the P200C (n=700) was performed to determine visibility of retinal nerve fiber layer loss. 36 eyes with a visible RNFL defect of at least two vein diameters and no obvious cupping were identified. Charts were then reviewed for corresponding defects as recorded with GDx and 24-2 VF. Patients with glaucomatous or pale discs as imaged with P200C were excluded.
Results: :
RNFL loss detected on the P200C was correlated with a defect on the GDx deviation map or corresponding VF loss in 94% of patients. Optomap correlated with GDx defects in 83% of eyes and with visual field loss in 69%.
Conclusions: :
A significant correlation was established between RNFL loss visualized on the Optos P200C imaging system and GDx. Since Optomap is already widely used for retinal screening, it can easily be a useful adjuvant tool in glaucoma screening. Although not specifically designed to measure RNFL loss, P200C is capable of showing subtle defects which may be indicative of early glaucoma, prior to the development of cupping. Viewing may be enhanced by using the red free image channel. When loss of the nerve fiber layer is visible on the Optomap it is suggested that further testing be performed. Visible RNFL loss that was not correlated with GDx may represent a loss too small to result in a GDx defect and follow up studies are underway.
Keywords: nerve fiber layer • imaging/image analysis: clinical • retina