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Eye and Vision Care

Testing Vision



I had a test by a Medical Dr where I put on glasses (one lens was green and the other red). With the glasses on I looked at a white piece of paper. The color of the paper seemed to change from red to green. Is this a valid way to test? Should it have been one eye covered and then the other? The Dr also tested by me looking at her finger as it was brought closer to my face. She said that she thought I needed a prism. Are these valid preliminary tests?


Yes, both are common vision tests.

The Red-Green glasses test determines whether both eyes are working well together. The right eye sees Red and the left eye sees Green. Therefore, you gave the correct response by saying the white paper was sometimes red and sometimes green.

The near-point-of-convergence test is done to determine how far the patient can voluntarily converge (turn-in) his eyes. If that distance is less than the patient's normal reading distance, prism can be prescribed in glasses to help the patient converge easier when reading.

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Response by:

Robert D Newcomb, OD, MPH, FAAO Robert D Newcomb, OD, MPH, FAAO
Professor Emeritus of Clinical Optometry
College of Optometry
The Ohio State University