Evaluation of corneal elevation and thickness indices in pellucid marginal degeneration and keratoconus
- 29 October 2012
- journal article
- research article
- Published by Ovid Technologies (Wolters Kluwer Health) in Journal of Cataract & Refractive Surgery
- Vol. 39 (1), 56-65
- https://doi.org/10.1016/j.jcrs.2012.08.053
Abstract
To determine and compare corneal elevation and thickness indices, thereby formulating a reliable index to distinguish eyes with pellucid marginal degeneration (PMD) from keratoconus eyes and normal (control) eyes. LV Prasad Eye Institute, Hyderabad, India. Initial model-building retrospective study. Anterior and posterior corneal elevations and thickness indices were obtained from the Orbscan IIz topographer. These values were analyzed and compared between PMD patients, keratoconus patients, and control subjects. Of the indices, the mean values of anterior elevation (AE), ratio of the AE to the anterior best-fit sphere, ratio of the average power values of nasal quadrant to the average power values of inferior quadrant, and difference between maximum keratometry (K) and minimum K were significantly different between the 3 groups (P<.05). The highest area under the receiver-operating-characteristic (AROC) curve in discriminating PMD from keratoconus was for asphericity (0.974; cutoff ≥-0.07; sensitivity 93.3%; specificity 90.6%) followed by the ratio of average power values of the nasal and temporal quadrants to the average power values of the inferior and superior quadrants (Avg NT((D))/IS((D))) (0.959; cutoff ≥1.005; sensitivity 96.7%; specificity 90.6%). The PMD index (AROC curve, 0.935), with a cutoff of 3.45 or higher had 90% sensitivity and 93.7% specificity to distinguish PMD from keratoconus and had 100% sensitivity and 100% specificity to distinguish PMD from control eyes, with a cutoff of 2.46 or higher (AROC curve, 1.000). The PMD index appeared to be highly sensitive and specific for diagnosing PMD. Asphericity and Avg NT((D))/IS((D)) were clinically relevant in discriminating PMD from other groups.Keywords
This publication has 23 references indexed in Scilit:
- What's in a Name: Keratoconus, Pellucid Marginal Degeneration, and Related Thinning DisordersAmerican Journal of Ophthalmology, 2011
- Corneal Elevation Topography: Best Fit Sphere, Elevation Distance, Asphericity, Toricity, and Clinical ImplicationsCornea, 2011
- Characteristics of ocular higher-order aberrations in patients with pellucid marginal corneal degenerationJournal of Cataract & Refractive Surgery, 2008
- Scheimpflug Photographic Diagnosis of Pellucid Marginal DegenerationCornea, 2008
- Comparison of and correlation between anterior and posterior corneal elevation maps in normal eyes and keratoconus-suspect eyesJournal of Cataract & Refractive Surgery, 2008
- Ectatic Disorders Associated With a Claw-shaped Pattern on Corneal TopographyAmerican Journal of Ophthalmology, 2007
- Corneal elevation indices in normal and keratoconic eyesJournal of Cataract & Refractive Surgery, 2006
- Risk factors and prognosis for corneal ectasia after LASIKOphthalmology, 2003
- Early Pellucid Marginal Corneal DegenerationCornea, 2002
- Iatrogenic keratectasia after laser in situ keratomileusis for less than −4.0 to −7.0 diopters of myopiaJournal of Cataract & Refractive Surgery, 2000