Accommodation during static retinal imaging with a confocal scanning laser ophthalmoscope.

摘要

PURPOSE: Accommodation of the eye can adversely affect optical tomography of the retina using a confocal scanning laser ophthalmoscope (cSLO). This study measured the dynamic accommodative response of young adult eyes while acquiring static retinal images with a cSLO without cycloplegia and also examined whether a scanned fixation target improves stability of accommodation. DESIGN: Experimental study. PARTICIPANTS: Four eyes of 4 controls whose ages ranged from 24 to 35 years. METHODS: Dynamic accommodation was measured by an infrared autorefractor during static cSLO imaging with a fixation target, without a target, while in darkness, and while viewing a Snellen chart at 20-feet distance. MAIN OUTCOME MEASURES: Mean accommodation across viewing conditions and rate of change of accommodation (velocity). RESULTS: Accommodation significantly increased in amplitude and in variability during imaging with the cSLO. Average peak velocity of accommodation was 1.37 diopters (D)/second, with a maximum of 2.27 D/second. Presenting a fixation target in the cSLO did not decrease accommodation but increased accommodation velocity in 3 of 4 subjects. CONCLUSION: Accommodation dynamically changes during acquisition of retinal images with a cSLO. Concurrent scanning of a visible target did not improve stability of accommodation reliably. Potential factors affecting accommodation include depth of focus (DOF), use of monochromatic stimuli, and nearby cues. Using the model eye, the error induced by accommodation is about 491 mum/second, with a maximum of 813 mum/second. In terms of the time to acquire individual optical sections, these estimates are consistent with previous reports of increased variability of topographic measurements in nondilated eyes.