Search PubMed⌕ Search

Biomedical subjects

R W Massof

Publications and source records attributed to R W Massof.

44 records · Page 3Linked to original sources
PubMed1975

Changes in the contrast sensitivity function induced by contact lens wear.

Contrast sensitivity functions (i.e. minimum contrast required to resolve a sine wave grating as a function of spatial frequency) were determined for subjects when wearing normal spectacle corrections and when wearing either hard or soft contact lenses. Corections provides a more definitive evaluation of visual performance with contact lenses than do the conventional clinical procedures.

Adult↗
PubMedDate not supplied

Visual function assessment questionnaires.

With increased emphasis on functional outcomes in ophthalmology, third-party health care payers and research funding agencies have turned their attention to the development and use of visual function questionnaires. Since 1980, more than a dozen such self-report visual function questionnaires have been developed. All of these instruments include items that ask about specific daily activities; patients must respond with a rating that represents the level of difficulty that they experience with the activity described. This article reviews all of the known instruments, with special attention paid to their validity and reliability. Most validation studies have reported high response consistency across items and significant correlations of instrument scores with visual impairment measures. Only two studies have measured test-retest reliability. The developers of visual function questionnaires typically divide the items into several different subscales, suggesting that different variables are being measured. Although the items are very similar for the different instruments, there is little agreement among instruments on the definition of subscales. All instruments are scored as the average of the ordinal patient ratings across items for each subscale and/or for the total instrument. Measurement issues underlying the scoring of ordinal patient ratings are discussed. It is argued that unless the instruments can be converted to interval scales, the averaging of patient ratings does not yield true measurements. The three visual function questionnaires that were calibrated with a statistical item response model, which estimates interval scales, are reviewed. It is concluded that future research and development should devote additional attention to the measurement properties of functional assessment instruments.

Psychometrics↗