Date of Award
Master of Science in Vision Science
Purpose: As variability in vision with a toric soft contact lens is related to cylinder power, providing the lowest acceptable amount of cylinder correction is sometimes a useful strategy. It would be useful clinically to have a reliable method of testing the acceptability of reduced cylinder correction prior to actually selecting and placing a trial soft toric contact lens on the eye. It would be useful to determine a patient's potential acceptance of a cylinder power and axis that is adjusted to those available in the soft contact lens.
Method: 18 myopic subjects (29 eyes), with astigmatism between 0.50D and 1.75D were evaluated. After determining optimal manifest refraction, the cylinder component of the refraction was adjusted to comply with those available in a single use toric soft lens such that the cylinder values and axes in the phoropter were set at -0.75 axis 180 degrees for with-the-rule eyes and -0.75 axis 90 degrees for against-the-rule eyes. Sphere power was then adjusted to best subjective acuity. High and low contrast visual acuity was determined through this attenuated refraction. Focus Dailies Toric lenses with power corresponding to the attenuated refraction were applied and allowed to settle. High and low contrast acuity were determined again, and compared with acuity obtained with the attenuated refraction.
Results: Analysis showed a reasonably linear relationship between the visual acuities obtained from the adjusted refraction and the trial contact lens, with a trend to better acuity with the contact lens. Acuity with the contact lens was the same or better than the attenuated refraction for 93% of eyes.
Conclusion: Practitioners performing an attenuated cylinder refraction prior to selecting a soft toric contact lens should be able to reliably predict the patient's visual acuity with the contact lenses.
Pethe, Douglas J. and Fedor, Ryan M., "Predicting toric soft lens acuity by attenuated cylinder refraction" (2004). College of Optometry. 1483.