October 10, 2014
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New contrast sensitivity test may be reliable in detecting glaucoma

The self-administered Internet-based test is designed to gauge the contrast threshold of central and peripheral vision.

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A new contrast sensitivity test demonstrated high reliability in identifying patients with glaucoma, according to a study.

The Spaeth/Richman Contrast Sensitivity (SPARCS) test is designed to evaluate central and peripheral vision.

“In this study, it was very important to show that the test results were reproducible,” Jesse Richman, MD, lead author and co-designer of the SPARCS test, told Ocular Surgery News. “The reliability of this test was beyond what we expected.”

The SPARCS test provides a global assessment of contrast sensitivity, Richman said.

“Most contrast sensitivity tests only assess vision centrally, but if patients are losing vision from glaucoma, more often it’s more than just centrally,” he said. “A lot of times it’s a diffuse disease, affecting more than just a focal spot in their vision. SPARCS captures more than just a central portion of the vision. It really tests the whole aspect of the visual function.”

The Internet-based test can be administered on a standard computer in an office setting or in the patient’s home.

The SPARCS test is undergoing clinical trials at Wills Eye Hospital in Philadelphia and the Aravind Eye Hospital in India. It is available at www.sparcscontrastcenter.com.

The study was published in the British Journal of Ophthalmology.

Self-administered test

The SPARCS test features multiple answer choices and a bracketing technique to determine contrast threshold. The website has instructions on how to take the test.

A patient seated 50 cm from a computer fixates on the central area of SPARCS. Vertical square wave gratings with a spatial frequency of 0.4 cycles per degree appear for 0.3 seconds in one of five tested areas. The patient identifies the area that appeared different from the others. The patient momentarily breaks fixation to select the area. The patient again fixates on the central area and clicks it to activate the program to show the next image. The test takes 3 to 5 minutes.

The SPARCS program records correct and incorrect responses until a contrast threshold is determined for each area. The central area and four peripheral areas are scored separately. A perfect score from all five areas is 100.

“If a patient is in the office, it’s not quite the same thing as doing a visual field, where you need to be coaching them along to keep them focused on the central area and keep them motivated,” Richman said.

Patients, methods and results

The prospective study included 261 eyes of 157 patients; 136 eyes had glaucoma or suspected glaucoma and a control group comprised 125 healthy eyes.

The researchers used SPARCS and the Pelli-Robson chart to assess contrast sensitivity.

“Pelli-Robson simply focuses on the center portion of the vision. It does a very nice job at testing contrast sensitivity for the central portion of the vision,” Richman said.

An intraclass correlation coefficient and coefficient of repeatability were used to assess the reliability of each test.

The intraclass correlation coefficient was 0.97 for SPARCS and 0.98 for Pelli-Robson. The coefficient of repeatability was 6.7% for SPARCS and 6.4% for Pelli-Robson.

Using the SPARCS test, glaucoma patients were identified with 80% sensitivity and 93% specificity.

Patients in the control group had significantly higher SPARCS scores than patients with glaucoma and suspected glaucoma (P < .05).

A total SPARCS score of less than 70 was associated with 80% sensitivity and 92.8% specificity for glaucoma. A Pelli-Robson score of 1.35 or lower showed 80.5% sensitivity and 76% specificity for glaucoma. – by Matt Hasson

Reference:

Richman J, et al. Br J Ophthalmol. 2014;doi:10.1136/bjophthalmol-2014-305223.

For more information:

Jesse Richman, MD, can be reached at Wills Eye Hospital, Glaucoma Service, 840 Walnut St., Suite 1110, Philadelphia, PA 19107; 215-928-3200; email: jesse_richman@yahoo.com.

Disclosure: Richman and co-authors Eric Spaeth and George L. Spaeth, MD, hold a patent on the Spaeth/Richman Contrast Sensitivity test.