Abstract
Purpose: :
To compare the best corrected visual acuity (BCVA) and level of aberrations present in a series of keratoconus (KC) patients when corrected with both a habitual, and a new reverse geometry contact lens design.
Methods: :
Data from a group of patients (n=3) wearing a variety of KC contact lens designs was taken and compared to the same group refitted with a reverse geometry KC contact lens design. Measurements while wearing each of the lenses included high contrast (HC) and low contrast (LC) Bailey–Lovie BCVA’s, and the HC/LC MC (Mixed Contrast) card. Aberrations were measured using the Bausch & Lomb ZyWave. Decentration between the center of the contact lens and the visual axis was measured by the Bausch & Lomb Orbscan II system. Measurements were performed on each subject with both lens designs and compared.
Results: :
The BCVA HC, LC, and amount of lens decentration of the standard design ranged from 20/47–20/20 HC, 20/188–20/30 LC and 2.44–1.50mm decentration. The same measurements with the reverse geometry design were 20/23–20/15 HC, 20/47–20/24 LC, and 1.81–0.50mm decentration. The level of aberration variance (Coma) between lenses was analyzed to be 3.47–0.25 with standard lenses, and 0.72–0.16 with the XLT lens. The XLT lens required a reduction of power 2–22D in comparison to standard design. The amplitude of decentration and the power of the contact lenses are directly proportional to the BCVA, and the measured level of aberrations.
Conclusions: :
The BCVA and aberration of the KC patients fitted with contact lenses can vary depending on the fitting characteristics of the lens design. Factors that result in a higher level of BCVA and lower aberrations include a reduced level of both decentration and power as properties of the lens design.
Additional comments: :
The instruments used in this study were provided by Bausch & Lomb. The lens material was provided by Contamac. The XLT lenses were manufactured by Innovations in Sight.
Keywords: cornea: clinical science • keratoconus • visual acuity