Chapter

Lacrimal Gland, Tear Film, and Dry Eye Syndromes 3

Volume 506 of the series Advances in Experimental Medicine and Biology pp 1141-1147

Predicting Optical Effects of Tear Film Break Up on Retinal Image Quality Using the Shack-Hartmann Aberrometer and Computational Optical Modeling

  • Nikole L. HimebaughAffiliated withSchool of Optometry Indiana University Bloomington
  • , Larry N. ThibosAffiliated withSchool of Optometry Indiana University Bloomington
  • , Carolyn G. BegleyAffiliated withSchool of Optometry Indiana University Bloomington
  • , Arthur BradleyAffiliated withSchool of Optometry Indiana University Bloomington
  • , Graeme WilsonAffiliated withSchool of Optometry Indiana University Bloomington

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Abstract

The pre-corneal tear film is the most anterior refracting surface of the eye. The large change in refractive index from air to tears makes it the surface with the greatest optical power. Therefore, a tear film of non-uniform thickness can potentially have a significant impact on the optical quality of the eye. 1.2 Many clinical studies have shown that, during periods between blinks, the tear film is not stable and does not remain uniform on the surface of the eye. Instead, it appears to disrupt locally, a phenomenon termed tear film breakup by clinicians, resulting in a tear film which is non-uniform in thickness. Although tear breakup is not usually regarded as an optical phenomenon, there is experimental evidence supporting the hypothesis that local changes in tear film thickness impact the optical quality of the eye. 3.5 The conclusions from these experimental studies are supported by clinical evidence of “blurry,” 6.7 “disturbed,” 8.9and “fluctuating” vision, and reduced visual acuity reported by dry eye patients and contact lens wearers.