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Maaike Langelaan, Bill Wouters, Annette C. Moll, Michiel R. de Boer, Ger H. M. B. van Rens; Functional Field Score: The Effect of Using a Goldmann V-4e Isopter Instead of a Goldmann III-4e Isopter. Invest. Ophthalmol. Vis. Sci. 2006;47(5):1817-1823. doi: 10.1167/iovs.04-1345.
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purpose. To investigate the underestimation of field loss in functional field score (FFS) between the Goldmann isopters III-4e and V-4e in visually impaired patients, in order to develop a predictive model for the FFSIII-4e based on FFSv-4e that adjusts for possible confounders. Although the visual field is generally evaluated using Goldmann isopter III-4e, it has the disadvantage that not all low-vision patients are able to see the stimulus corresponding to this isopter.
methods. Goldmann visual fields were obtained from 58 patients with a variety of eye diseases. Eligibility criteria were age of 18 years or older and valid results of a Goldmann III-4e and V-4e visual field test in at least one eye. Linear regression was used to develop the model, setting FFSIII-4e as the dependent variable and FFSV-4e as the independent one.
results. The FFSV-4e was higher than the FFSIII-4e, the mean difference being 14.56 points (95% CI, 12.48 –16.64). Multiple linear regression analysis showed that age, functional acuity score, primary eye disease, and central–peripheral loss were not confounders for the prediction of FFSIII-4e. FFSIII-4e was estimated with the following equation: FFSIII-4e = −19.25 + 1.063 · FFSV-4e.
conclusions. The relationship between FFSIII-4e and FFSV-4e is linear, and the FFSV-4e can be used to estimate the FFSIII-4e. In practice, just subtracting 19.25 points of the value of FFSV-4e will be sufficient to estimate the value of FFSIII-4e. This model should give confidence about using the bigger isopter for determining the visual impairment of a person by the FFS.
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