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Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study: methods and findings to date.

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Contact lens fitting relation and visual acuity in keratoconus.

K Zadnik1, D O Mutti

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Rigid contact lenses for keratoconus (KC) showed minimal visual acuity improvement with flatter base curves. While statistically significant, the gains were not clinically meaningful for patients with central cones.

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Area of Science:

  • Ophthalmology
  • Optometry
  • Corneal Disease

Background:

  • Keratoconus (KC) is a progressive corneal disease causing irregular astigmatism and visual decrement.
  • Current understanding of how contact lens fitting philosophies impact visual acuity in KC is limited.

Purpose of the Study:

  • To investigate the effect of different rigid contact lens fitting parameters on visual acuity in keratoconus patients.
  • To evaluate the clinical significance of visual acuity changes associated with varying lens base curves and diameters.

Main Methods:

  • Ten eyes with keratoconus were assessed using an automated visual acuity device.
  • Rigid contact lenses with varying base curves (flatter to steeper than keratometry) and diameters (large/flat vs. small/steep) were fitted.
  • Visual acuity was measured for each lens fitting condition.

Main Results:

  • A small, statistically significant improvement in visual acuity was observed with flatter-fitting lenses.
  • This improvement equated to approximately half a line of visual acuity and was not considered clinically significant.
  • A decrement in visual acuity was noted in keratoconus patients with centrally located cones.

Conclusions:

  • Contact lens fitting philosophies, specifically base curve selection, have a limited impact on visual acuity in keratoconus.
  • The observed visual acuity gains with flatter lenses are not clinically relevant for improving patient vision.
  • Centrally located cones in keratoconus may be associated with reduced visual acuity, warranting further investigation.