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Jukka Ari Olavi Moilanen, Essi Peltomaa, Juha M. Holopainen; Contrast sensitivity and aberrations in good and supranormal visual acuity. Invest. Ophthalmol. Vis. Sci. 2016;57(12):212. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Applicants for fighter pilot training in the Finnish Air Force must have excellent uncorrected visual acuity. We compared test results from applicants with supranormal visual acuity (20/10 or better) and applicants with normal visual acuity in contrast sensitivity (CS), corneal tomography and wavefront aberrations to reveal physiological characteristics for supranormal vision.
Recruits' (44 male, 1 female, 18-21 years) right eyes were tested for visual acuity with Landolt-C-test; CS with Functional Vision Analyzer, FACT method in photopic and scotopic conditions; corneal tomography with Orbscan; higher order aberrations with Wavescan. Visual acuity and CS was cross-analyzed to different variables.
Average visual acuity in the study population was -0.25 (logMar, SD 0.07, range 20/16 - 20/9). Visual acuity better than 20/10 was observed in 8 subjects (supranormal group). Cyclorefraction (spherical equivalent) was +0.38 D (SD 0.43). The maximum refractive astigmatism was 0.5 D.Average corneal astigmatism in tomography was 0.61 D (SD 0.28 D). CS in different spatial frequencies (logarithmic average and SD) was 1.79 (0.15), 2.11 (0.09), 2.17 (0.09), 1.91 (0.15), and 1.59 (0.22) in daylight and 1.88 (0.12), 2.10 (0.08), 2.05 (0.15), 1.64 (0.22), and 1.23 (0.24) in night condition, in 1.5 cpd, 3.0 cpd, 6.0 cpd, 12 cpd, and18 cpd, respectively. There were no statistical differences in CS related to visual acuity or other parameters. In wavefront eamination, average root mean square (Rms) was 0.39 (SD 0.13). Rms more than 0.4 (0.45-0.7) was observed in 4 out of the 8 supranormal subjects. Corneal irregularities or Kappa angle did not show statistical differences to visual acuities.
There were no differences in the contrast sensitivity, corneal tomography details or higher order aberrations that could explain why some individuals have better visual acuity than others. Interestingly, best visual acuities were observed in subjects with more than average higher order aberrations (p=0.28). These findings suggest that our understanding of the visual function, or our methods to examine it, is still limited. Furthermore, the intention to improve visual acuity and contrast sensitivity with refractive surgery by decreasing higher order aberrations needs further investigation.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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