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J.P. Kelly, E. Seibel, B. Schowengerdt; Accommodation to a Confocal Scanning Laser Ophthalmoscope . Invest. Ophthalmol. Vis. Sci. 2004;45(13):2802.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: The confocal scanning laser ophthalmoscope (cSLO) has broad applications for imaging of the non–cyclopleged eye. However, little is known about the accommodative response of the eye while acquiring retinal images, and whether a laser–generated stimulus affects accommodation. Since cSLO stimuli are monochromatic they lack longitudinal chromatic aberration cues for reflex accommodation. Secondly the observer does not have binocular input to the cross–link mechanism for vergence accommodation. Methods: Three emmetropes and, one subject with astigmatism (–0.76, –2.75 x 10), were tested. All had > 3D of accommodation. A prototype compact cSLO (LDT inc) imaged the macula with a 780 nm beam and simultaneously generated targets on the macula with a 645 nm beam. Accommodation was measured under 4 conditions (reading acuity at 20 ft, darkness, while fundus imaging with a blank field (cSLO no image), and fundus imaging while the subject viewed a laser generated "Maltese cross" (cSLO image). Accommodation of the other eye was measured concurrently at 5 Hz using an autorefractor (Welch Allyn). Results: Accommodation to the cSLO was always significantly higher (means 0.6 – 0.9 D) compared to the distance and darkness conditions (t–test; p <0.0001 for all). The cSLO stimulus condition generated slightly less accommodation than the cSLO no image condition. Subjects continued to increase accommodation even when the cSLO was defocused by +1.25 D in order to relax accommodation. The s.d. accommodation amplitude increased slightly while subjects were tested with the cSLO (0.1 – 0.4 D). All subjects had dynamic changes of more than 1 diopter while acquiring static images with the cSLO. However, the velocity of accommodation was estimated to produce error at, or within, typical longitudinal reproducibility for current cSLO instruments. Conclusions: Ocular depth–of–focus, monochromatic stimuli, and proximal cues are potential factors affecting accommodation while viewing a cSLO. Adding a stimulus generated by the cSLO did not greatly improve accommodation. Although accommodation fluctuates considerably, the rate of change in the depth plane during accommodation was estimated to be acceptable.
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