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Friday, March 7, 2014
Eye and Vision Care
Humphrey Visual Field Exam
I have heard that the size of the dot during the exam can be adjusted to a bigger size? Is this true? I am very near sighted with astigmatism and it seems a larger dot would make the exam easier/more accurate. Also, is astigmatism accounted for in the lens used during the exam?
The target size and brightness used for visual field testing can be changed for individual patients. But since visual field testing requires the patient to report either "I see it" or "I do not see it", the target does not need to be in perfect focus; so correction for astigmatism is usually not necessary.
The art of visual field testing is to determine the patient's threshold; that is, the smallest and dimmest target the patient can reliably see. So testing with a very large and/or a very bright target defeats the goal of measuring the patient's ability to respond to more subtle light stimuli.
Thanks for an excellent question to Netwellness.
Robert D Newcomb, OD, MPH, FAAO
Professor Emeritus of Clinical Optometry
College of Optometry
The Ohio State University