To the Editor.
—In their case-control study, "Risk Factors of Branch Vein Occlusion," Johnston et al, in the December 1985 issue of the Archives,1 state that systemic hypertension is a risk factor, with 60% of cases studied being hypertensive as compared with 47% of controls (P =.011). The answer to the several important methodological questions that follow would be helpful in assessing their claim: (1) Was hypertension determined comparably in the retrospective cases vs the prospective controls; ie, how often was the determination made by patient history vs blood pressure measurement in cases vs controls? When the assessment was performed by blood pressure measurement, how was blood pressure measured (eg, one or more readings, by whom, under what patient conditions, and using a random zero manometer)? In patients with branch retinal vein occlusion, how often was hypertension diagnosed by the internist based primarily on the existence of a new
Finkelstein D, Kimball A. Risk Factors of Branch Retinal Vein Occlusion. Arch Ophthalmol. 1986;104(6):795. doi:10.1001/archopht.1986.01050180025008
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