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Editors Selection IGR 16-4

Progression: Agreement of VF interpretation

Comment by Chris Johnson on:

45509 Agreement of visual field interpretation among glaucoma specialists and comprehensive ophthalmologists: comparison of time and methods, Lin AP; Katz LJ; Spaeth GL et al., British Journal of Ophthalmology, 2011; 95: 828-831

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As indicated by Lin et al. (1081), the determination of visual field progression and rate of visual field progression in glaucoma remains as an enigma, and a variety of approaches have been developed to address this problem.¹ In general, approximately six visual fields obtained over a period of two to three years are necessary to achieve good performance (sensitivity, specificity, positive predictive and negative predictive value, etc). Test-retest variability and other factors make it difficult to distinguish pathology related visual field changes from other confounding influences on repeated visual field examinations. Unfortunately, there is no clear consensus as to which analytical or statistical approach is preferred, a factor that depends on the goals of the evaluation (e.g., early detection, optimal performance, determination of rate). Several investigations have also demonstrated that the most commonly used procedures only agree with each other about 50-65% of the time.^2-5 and the reasons for the lack of agreement among these approaches remains an open question at the present time.

Approximately six visual fields obtained over a period of two to three years are necessary to achieve good performance

An even more challenging issue concerns evaluation of glaucomatous visual field progression by practitioners. Each eye care specialist has individual preferences and biases that weight the relative importance of a variety of different parameters associated with the visual field. Additionally, the criteria that are used by individual practitioners can vary considerably. The present study indicates that using several statistical and analytical tools for evaluation of visual field progression, glaucoma specialists are moderately better than comprehensive ophthalmologists in assessing visual field progression, and are able to accomplish these determinations in a shorter period of time. Part of this is undoubtedly due to the more extensive importance of visual fields in a glaucoma practice, the greater experience in evaluating visual fields and the more constant exposure of glaucoma specialists to visual field information. I find it impressive that glaucoma specialists and comprehensive ophthalmologists are able to perform assessments of visual field progression at a performance level that is essentially equivalent to the extensively developed algorithms that have been formally developed to address this issue.

Glaucoma specialists and comprehensive ophthalmologists are able to perform assessments of visual field progression at a performance level that is essentially equivalent to the extensively developed algorithms

When detailed, formal criteria are developed to assess visual field progression or change, and repeated practice sessions are provided with feedback, agreement among visual field readers can approach levels nearing 90%, and test-retest evaluations of the same reader can be better than 95%.⁶ However, this is not a procedure that could be used on a routine basis in a busy clinical setting, but has been implemented for multicenter clinical trials. To achieve better performance and agreement among practitioners, additional training procedures are needed. The authors of this paper have provided useful information about the status of visual field interpretation for monitoring glaucoma patients, which should serve as an incentive for investigators to develop more refined and consistent methods.

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