Measurement Repeatability in Contemporary Aberrometry

A Comparative Study of Measurement Repeatability for Two Aberrometers

Wavefront scans are a common form of diagnostic test applied in preparing patients for laser eye surgery. An optical map of the eye is created by wavefront scanning, and information from these maps is used to program lasers used to correct focusing errors in the eye. Here the investigators are comparing how repeatable measurements are with a new wavefront scanner and one that is already in widespread use.

Aberrometers are used to measure each element of defocus (aberration) in an optical system. In LASIK, information derived from aberrometry (scans performed using aberrometers) is used to program the pattern of laser pulses delivered by an excimer laser in therapeutic reshaping of the cornea to correct defocus. To do this accurately, aberrometry findings need to be repeatable and correspond closely to manifest refraction. Here the investigators compare repeatability of measurements for a new aberrometer (Peramis) versus the aberrometer most widely used in contemporary wavefront guided laser vision correction (iDesign).

The test aberrometer will be:

Peramis (Schwind Eye-tech Solutions, Kleinostheim, Germany).

Control aberrometer will be:

iDesign (AMO, Santa Clara, CA)

Inclusion Criteria:

• Myopic LASIK candidates (manifest refraction spherical equivalent range 0 to -10 diopters with up to 6 diopters cylinder) or patients attending corneal service with stage II-III keratoconus or post-keratoplasty

Exclusion Criteria:

• Visually significant co-pathology (CDVA<6/6) other than irregular astigmatism;
• Patients unable to complete a sequence of 2 good scans (acquisition diameter >5mm) in one eye within 4 attempts