Astigmatism Research Today is a free monthly online journal that collates and summarizes the latest research about Astigmatism, including details on cornea, retina, treatment, types, signs, tests.

Evaluation of deep lamellar endothelial keratoplasty surgery using scatterometry and wavefront analyses.

Hindman HB, McCally RL, Myrowitz E, Terry MA, Stark WJ, Weinberg RS, Jun AS

Wilmer Eye Institute, Johns Hopkins Hospital, Baltimore, Maryland 21287, USA.

OBJECTIVE: To determine if postsurgical corneal interface abnormalities after deep lamellar endothelial keratoplasty (DLEK) cause increased light scattering or wavefront aberrations that may help to explain decreased best-corrected visual acuity in DLEK patients compared with penetrating keratoplasty (PK) patients. DESIGN: Prospective comparative case series. PARTICIPANTS: Clinically clear corneas of 4 eyes that had undergone DLEK surgery and 4 eyes that had PK were studied. Normal control data for light scattering was collected from 12 right eyes and 11 left eyes with normal corneas. METHODS: Corneal light scattering was measured with a scatterometer designed at the Johns Hopkins Applied Physics Laboratory, and wavefront analysis was performed using standard methods with a Hartmann-Shack wavefront sensor. MAIN OUTCOME MEASURES: Corneal scattering measurements were normalized by taking the ratio of the subject's corneal light scattering to a reference material. A scattering index was calculated as the ratio of the normalized scattering for a given patient's cornea to the average scattering of normal corneas. Astigmatism and higher-order aberrations were analyzed using standard data output from wavefront analysis and Zernike polynomial decomposition. RESULTS: The mean scattering index was significantly higher after DLEK (1.78+/-0.29, mean+/-standard deviation [SD]) than after PK (1.03+/-0.27; P = 0.043). The higher-order root mean square (RMS) wavefront error was significantly higher after PK (0.71+/-0.11 microm, mean+/-SD) than after DLEK (0.44+/-0.12 microm; P = 0.029). Zernike polynomial decomposition of the wavefront aberrations revealed that regular corneal astigmatism was the most important aberration component for both PK and DLEK, but the PK patients had significantly more regular astigmatism (1.7+/-0.45 diopters [D], mean+/-SD) than did the DLEK patients (0.84+/-0.27 D; P = 0.029). CONCLUSIONS: Our data quantitatively support subclinical corneal haze as an explanation for the limited visual acuity after DLEK as compared with PK. Intraoperative or postoperative modifications to reduce stromal haze after DLEK may result in better visual acuity outcomes.

Published 5 November 2007 in Ophthalmology, 114(11): 2006-12.
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