Purpose
To evaluate the central visual field (CVF) with specialized Amsler grid testing methods that include contrast sensitivity
evaluation, in an attempt to detect abnormalities not identified with standard methods and to define new patterns of CVF deficits
in two different diseases.
Methods
3D computer-automated threshold Amsler grid testing (3D-CTAG) was performed at five levels of contrast in one eye of 37 patients
with diabetic macular edema (DME, n = 16) and exudative age-related macular degeneration (AMD, n = 21).
Results
3D-CTAG abnormalities were detected in six patients (16%) who had no abnormalities with conventional Amsler grid testing.
DME patients had more foci of CVF deficits (3.56 ± 2.92 defects/eye), than AMD patients (1.24 ± 0.89 defects/eye; P < 0.0002). The shape of the 3D-CTAG abnormality in DME was an inverted cone, while the deficits in AMD were always cylindrical.
All eyes showed significant increases in CVF deficit surface area at minimum contrast levels when compared to maximum contrast
(295% greater with DME, P < 0.02 and 150% greater with AMD, P < 0.03).
Conclusion
3D-CTAG detected CVF abnormalities not identified with conventional Amsler grid testing in 16% of subjects. Low-contrast conditions
elicited a larger defect in both DME (3-fold) and AMD (1.5-fold). DME and AMD have unique 3D-CTAG profiles, enabling diagnostic
discrimination. Measuring CVF defects with 3D-CTAG can quantitatively index disease severity and may be useful in longitudinal
studies of the natural history of disease, as well as providing a quantitative outcome measure of the response to therapy.
Keywords Age-related macular degeneration - Amsler grid - Contrast sensitivity - Diabetic macular edema - Macular edema - Scotomas
The results of this study have been presented in part at the Western Retina Study Club meeting in Pasadena, CA, USA, March
2007 and at the Association for Research in Vision and Ophthalmology (ARVO) meeting in Fort Lauderdale, FL, USA, May 2007.
The principal investigator, JS, had full access to all the data in the study, and takes responsibility for the integrity of
the data and accuracy of the data analysis. All authors agree to allow Graefe’s Archive for Clinical and Experimental Ophthalmology
to review their data if requested.
All human studies have been reviewed by the appropriate ethics committee and have therefore been performed in accordance with
the ethical standards laid down in the 1964 Declaration of Helsinki.
Competing interests: Authors AAS and WF may have proprietary interest in the 3D computer-automated threshold Amsler grid test
described in the study as patents on the technology are issued.