Early Detection of Glaucoma by Means of a Novel 3-D Computer-automated Visual Field Test

Paul P Nazemi ¹, Wolfgang Fink ^2*, Alfredo A Sadun ¹, Brian A Francis ¹ and Don S Minckler ³

¹ Doheny Eye Institute, Keck School of Medicine at the University of Southern California, United States
² California Institute of Technology, United States
³ UC Irvine Department of Ophthalmology, United States

^* To whom correspondence should be addressed. E-mail: wfink{at}autonomy.caltech.edu.

Accepted 1 May 2007

Abstract

Purpose: A recently devised 3-D computer-based threshold Amsler grid test was used to identify early and distinctive defects in glaucoma suspects. Further, we characterized the location, shape and depth of these field defects. Finally, we compared the visual fields to those obtained by standard automated perimetry.

Patients and Methods: Glaucoma-suspects were defined as those having elevated intraocular pressure (> 21 mmHg) or cup to disc ratio of >=0.5. 33 patients and 66 eyes with risk factors for glaucoma were examined. 15 patients and 23 eyes with no risk factors were tested as controls. We used the recently developed 3-D computer-based threshold Amsler grid test. The test exhibits a grid on a computer screen at a preselected grayscale and angular resolution, and allows patients to trace those areas on the grid that are missing in their visual field using a touch screen. The 5-minute test required that the patients repeatedly outline scotomas on a touch screen with varied displays of contrast while maintaining their gaze on a central fixation marker. A 3-D depiction of the visual field defects was then obtained that was further characterized by the location, shape, and depth of the scotomas. The exam was repeated 3 times per eye. The results were compared to Humphrey visual field tests (achromatic standard or SITA standard 30-2 or 24-2).

Results: In this pilot study 79% of the eyes tested in the glaucoma-suspect group repeatedly demonstrated visual field loss with the 3-D perimetry. The 3-D depictions of visual field loss associated with these risk factors were all characteristic or compatible with glaucoma. 71% of the eyes demonstrated arcuate defects or a nasal step. Constricted visual fields were shown in 29% of the eyes. No visual field changes were detected in the control group.

Conclusions: The 3-D computer-automated threshold Amsler grid test may demonstrate visual field abnormalities characteristic of glaucoma in glaucoma-suspects with normal achromatic Humphrey visual field testing. This test may be used as a screening tool for the early detection of glaucoma.

Keywords: early detection, glaucoma, glaucoma suspects, threshold Amsler grid, visual field

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