Abstract
Purpose: :
Last year, we reported that blur tolerance (to dioptric spherical defocus) was related to measures of personality in a "young" population. We tested that relationship in a presbyopic population, and refined the personality questionnaire.
Methods: :
A computer-controlled Badal optometer was used to measure "just-noticeable" blur (depth of focus) and "objectionable" blur responses to positive lens defocus with natural pupils. Blur tolerance was defined as the difference between the just-noticeable and objectionable blur responses while viewing three 20/50 high-contrast letters. The personality questionnaire, including the two scales (12 items) found previously and a further 51 personality items that were hypothesized to be relevant, was administered using MediaLab software. Sixty-five normally-sighted subjects (median 58, range 42 to 86 years; median refractive error -0.2DS, range -5.2 to +5.3 DS; visual acuity < 20/25) completed both aspects of the study.
Results: :
The range of individual blur tolerances (0 to 1.4D) was similar to the young group (p=0.42). The personality scales exhibited acceptable reliability (Cronbach’s alpha = 0.68 to 0.90). The two ("low self confidence" and "disorganization") scales developed in the previous study were significantly correlated with blur tolerance (r = 0.34, 0.32) in this new population. Two new measures of low self-confidence and disorganization, based on different items, exhibited similar correlations with blur tolerance as did the previous scales, suggesting that these are robust constructs. Two other established scales were not significantly correlated. The novel sensory irritability questionnaire items most highly correlated with blur tolerance were factor analyzed and yielded two factors (alphas = 0.55, 0.66). The "visual acceptance" and "smell and noise acceptance" factors were positively correlated with blur tolerance (r = 0.25 and 0.24, respectively), and their composite correlated with blur tolerance (r = 0.36). In the personality literature, correlations of this magnitude are considered high. People who had tried bi/multifocal glasses had higher visual acceptance scores (p=0.03).
Conclusions: :
These results provide further evidence for a relationship between personality and blur tolerance. In addition to lacking self-confidence and being more disorganized, it appears that people who tolerate blur are more tolerant of other sensory irritations (e.g. dirty windshield, smells). If tolerance of blur is related to perception of image quality, personality may influence refractive error correction and other choices made when presented with degraded images.
Keywords: perception • adaptation: blur