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Yoko Hirohara, Tatsuo Yamaguchi, Mariko Kobayashi, Keisuke Yoshida, Takashi Fujikado, Toshifumi Mihashi; Chromatic Aberrations Of Normal Eyes With And Without Mydriasis In Visible And Near Infrared Wavelengths. Invest. Ophthalmol. Vis. Sci. 2012;53(14):162.
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© ARVO (1962-2015); The Authors (2016-present)
Chromatic difference of refraction (CDR) and Chromatic higher order wavefront aberrations (CHs) have been measured using a Shack-Hartmann wavefront aberrometer (SHWA) (Llorente 2003, Manzanera 2008). The measurement of refraction and wavefront aberrations (WAs) in a visible wavelength may be more accurate than that in a near infrared wavelength although visible light could reduce pupil size and induce accommodation. We investigated the validity of measuring chromatic aberrations with an SHWA with and without mydriasis.
We developed an SHWA which can measure objective refraction (OR) and WAs in three different wavelengths (561, 690, and 840 nm). We also developed a unique artificial eye to calibrate the SHWA for chromatic aberrations. The artificial eye was a catoptric type, and then not only monochromatic-aberration-free but chromatic-aberration-free. The range of spherical error of the artificial eye was from -0.1 to -10.1 diopter (D). The refractions of all the subjects were within this range. The ORs and WAs of six eyes of four normal subjects (36 years TY, 37 years YH, 41 years MS, 54 years TM) were measured ten times before and after dilation of pupils by topical tropicamide and phenylephrine (Midrin-P®). The SHWA measured ORs and WAs sequentially by switching the three light sources. The exposure time was under 0.2s for every wavelength. WAs were analyzed over a 3-mm diameter area in the center of the pupil and averaged 10 measurements. We compared spherical equivalents (SEs), higher order WAs (HWAs), and CDRs before and after mydriasis.
The SEs and WAs of the SHWA were calibrated and the calibration error of HWA was less than 0.03 um. We found statistically significant differences (the differences of SEs before and after mydriasis were -0.71 ± 0.44 D) in the SEs of normal eyes except TM’s before and after mydriasis. The pupils shrunk but the diameters were bigger than 3-mm before mydriasis, but CDRs were not statistically significantly different before and after mydriasis. The average of CDRs between 840 nm and 561nm was 1.1 D. The individual changes of the HWAs were under 0.02 um.
These experiments showed that objective measurements of refraction in the visible wavelength could be affected by the involvement of accommodation but measurements of CDR and HWAs were not.
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