Comment on the value of vision by Knauer et al.,

Abstract

s Archive for Clinical and Experimental Ophthalmol-ogy (2008) 246:477-482 entitled “The value of vision.” Theauthors use, as the basis for their commentary, work that hasbeen done to evaluate how much patients with ophthalmicdiseases are concerned about their visual loss. One methodof estimating this is to use the technique discussed by theauthors, “the time trade-off method,” in which patientsdecide how many years of their life they would give up toachieve the desired outcome [6]. Knauer and Pfeiffercomment correctly that some of the studies that have beendone on ophthalmic disease indicate that vision is of greatimportance to patients [1–3].They compare the valuesobtained for other conditions such as AIDS and stroke, andconclude that the relative value of the patient’s vision is trulyextraordinarily great [ 4, 5].The authors, however, do not consider an extremelyimportant issue, which may well invalidate their conclu-sion. Time trade-off studies related to the value of visionask the question, “What is the maximum number of years—if any—you would be willing to give up if you could have anormal vision in both of your eyes for the remainder ofyour life?” Note, the question has to do with recoveringvision. But in contrast, in the standard time trade-offmethodology patients are asked, “What is the maximumnumber of years—if any—you would be willing to give upif you could have perfect health for the remainder of yourlife?”“Vision ” and “health” arenotthesamething.Presumably, vision influences a person’s health. It may bethat some individuals consider vision the most importantaspect of their health. It may also be that some individualsconsider vision an unimportant aspect of their health. But itis not proper to compare the results of those studies done bythe Browns, in which they are asking patients aboutrecovering vision, with those of the great majority of timetrade-off studies, in which subjects are asked aboutrecovering health.As an ophthalmologist, I would love to believe that theBrowns, and Knauer and Pfeiffer are correct in commentingthat patients value vision ahead of being hospitalized withtuberculosis for 3 months, or having a stroke that results ina level of disability causing the person to be unable to walkand unable to wash himself or herself; however, that this isthe case is speculation, and cannot be supported bycomparing two different methodologies, one studyingvision, and the other studying health.References