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MR StevensonSFRADS; Longitudinal Analysis Suggest Adaptive Strategies to Visual Loss Which are not Picked up by Cross-sectional Methods . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3836.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose:To assess if visual functioning measured cross sectionally on two occasions across a group of visually impaired individuals provides the same information as a longitudinal analysis. Methods:Data from SFRADS which recruited 200 patients with exudative AMD across three UK centers was used. Patients were aged over 60 years with angiographic evidence of classic CNV and a distance acuity in the study eye of 1.0 logMAR or better. Visual functioning was assessed using the DLTV (a previously validated instrument) which was scored on a 0 (worst possible) to 100 (best possible) outcome scale. Multiple linear regression was used to examine the relationship between DLTV summary score and corrected distance visual acuity in the better eye (a) at baseline and b) at 24 months and longitudinally between change in DLTV and change in distance acuity over the same period. Potential covariates included when statistically significant (p < 0.05) were age, gender, bilateral visual impairment, history of smoking, and centre Results:Mapping across of DLTV scores to acuity at baseline showed that a difference of 5 units of the summary score corresponded to a difference of 1 line on the logMAR chart . The same relationship was found for the 24 month data. As acuity ranges from approximately -0.3 to +1.7 logMAR and there are 100 units on the DLTV scale, this result confirms what is intuitive. Examination of the data longitudinally however, showed that a difference of only 3 units of the DLTV summary score corresponded to 1 line of vision lost. Conclusion:Our findings suggest that patients adapt to loss of vision in terms of self reported visual functioning. Such compensation needs to be considered in the design of trials when using self reported visual functioning as an outcome measure.
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