Progression of visual field loss not always easy to test, analyze

Reviewed by Chris A. Johnson, PhD, DSc, FAAO, FARVO

Assessing visual field progression in glaucoma may be more of an art than a science-and there is no one test to give reliable information that is needed about a patient, said Chris A. Johnson, PhD, DSc, FAAO, FARVO, professor, Department of Ophthalmology, and director, Visual Field Reading Center, University of Iowa, Iowa City.

One barrier when looking at progression of visual field loss in glaucoma is there can be various types of impairment, be they systemic or ocular. This can include cataracts, corneal problems, retina disease, or optic neuropathies or systemic issues such as diabetes, inflammatory, infiltrative, or compression lesions.

Other challenges include subjective analyses and reliability of results, as well as considerable variability from one test to another, Dr. Johnson said.

Another challenge is that assessing progression is usually different when comparing multi-center trials with routine management.

Click here to enlarge Image 1. The first slide presents two initial baseline visual fields and a representation of the Mean Deviation (MD) values over time in the lower left plot. 

Click here to enlarge image 2. The second slide presents visual fields obtained for six follow up exams. It uses a combination of event analysis (change from baseline) and trend analysis (confirmation of change from baseline for additional tests).  A change from baseline that is confirmed on the next test is classified as possible progression, and if it is confirmed on 2 successive tests (three in a row, counting the initial occurrence) it is classified as likely progression. Images courtesy of Chris A. Johnson, PhD, DSc, FAAO, FARVO.

Sometimes, circumstances specific to a patient can make assessment of visual field progression difficult. Dr. Johnson referred to a visual field from a patient who would seem to get worse every 6 months and then get better, but then get worse again before getting better.

“Has this person progressed or not? That’s the critical issue,” he said.

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