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Editor,—It is well known that patients with glaucoma develop defects in their field of vision. It is generally assumed that these defects interfere with the affected individual’s visual function.
This study explored the relation between visual field loss and the perception of visual disabilities in patients with glaucoma.
A questionnaire designed to identify vision associated limitations in daily activities (VALDA, Table 1) was applied to 231 patients with glaucoma who had reliable computerised visual field examination with the Humphrey 24–2 program.1-6 Visual field loss was quantitatively evaluated (“mean deviation” (MD) and “pattern standard deviation” (PSD)). The relation between the presence of VALDA and visual field defects, visual acuity, and age was investigated.
There were 91 (39.4%) males and 140 (60.6%) females. The ages ranged from 13–90 years, with a mean age of 68.5 (SD 12.6) years. Most patients were white (n=213, 92.2%) and 18 (7.7%) were black. The mean duration since the diagnosis of glaucoma was 8.7 (SD 8.1) years (range 1–40). Ninety eight subjects (42%) reported a subjective perception of vision associated limitations in daily activities. Among the limitations mentioned by the patients, problems with night driving ranked first (97%) followed by difficulties reading newspapers (33%), and driving at any time (27%); limitations doing outdoor activities were present in 10%. The perception of VALDA was related to visual acuity and was significantly greater in older patients.
We analysed in patients with visual acuity better than or equal to 20/40 in both eyes (127 patients) the relation between the visual field defect and the VALDA score (Table 2). The perception of VALDA was related to the MD loss in both eyes, but not to the PSD.
Monocular visual field examinations are frequently used clinically in monitoring glaucoma, but, from a functional viewpoint, binocular visual fields or combined monocular visual fields would be more helpful in evaluating visual function. Esterman proposed a binocular scoring system of visual fields. However, software to perform Esterman’s binocular scoring system in automated perimeters is still under clinical investigation.3 4
Bernth-Petersen was the first to point out that some patients with cataracts have good visual function in spite of poor visual acuity.5 Because of this, he suggested that the performance of everyday tasks that are dependent on vision must be assessed in evaluations of visual function.5 6 It is the experience of most ophthalmologists that problems resulting from visual field loss contribute to those caused by reduced visual acuity. Thus, global assessment of visual limitations may provide information about a patient’s wellbeing, complementing the visual acuity or visual field data. Evaluation of visual function and quality of life in patients with ocular diseases has been done with several questionnaires.1-10 In glaucoma patients Parrish7 and Gutierrez et al 8found that vision targeted questionnaires were more sensitive than generic health related quality of life measure to visual field loss.
In this study, we found that the perception of limitation in daily activities is closely related to a general loss of visual field (MD loss) in both eyes. Although visual acuity played an important role in visual function (that is, VALDA), we found that, even with good visual acuity in both eyes, patients with high MD loss in both eyes reported a high rate of limitations in daily life. Our finding that few patients with bilateral normal visual fields reported VALDA (2.7%) demonstrates that patients rarely have remarkable functional disabilities before the appearance of clinically detectable visual field damage.
In conclusion, a questionnaire regarding vision associated limitations in daily activities provides information about patients’ wellbeing. Visual limitations, as measured in this study, appear to be related to the total amount of visual field loss. Some patients with visual field loss do not have any limitation in visual function.
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