Purpose:
To determine the characteristics of blur perception of the human eye in a large sample of inexperienced adult subjects
Methods:
Three groups of visually-normal subjects ages 40 - 50 years were tested under cycloplegia using 3 pupil sizes (3.0, 4.5 and 6.0mm). These included high myopes (SE-4.25D to -8.00D, n=32), low myopes (SE=plano to-4.00D, n=39) and hyperopes (SE=+0.25 to +4.00D, n=28). All subjects had low astigmatism (<-0.75D). 31 were male and 68 were female. The blur perception criteria were first noticeable blur (or depth of field), bothersome blur, and non-resolvable blur. Stimuli consisted of 20/50 text words in a Badal optical system. Subjects were tested monocularly with full distance single vision contact lens correction in place.
Results:
Mean blur thresholds (i.e. the dioptric interval between proximal and distal thresholds) and SEMs are summarized in the table below:The blur thresholds decreased with increased pupil size and increased from first noticeable blur to bothersome blur to non resolvable criteria. The blur thresholds were increased in low myopes as compared to high myopes on average by 0.34D.
Conclusions:
First, the results are consistent with earlier literature conducted with small numbers of highly experienced subjects using similar criteria and pupil sizes. Second, the increased blur thresholds in the low myopic group are consistent with the notion that they are more susceptible to the myopiagenic effects of retinal defocus, the high myopes however are less susceptible because of their decreased thresholds.
Keywords: myopia • optical properties • pupil