Comparative evaluation of refractive surgery candidates with Placido topography, Orbscan II, Pentacam, and wavefront analysis

Abstract

Several parameters provided by the Pentacam, Orbscan II, WaveScan, and pachymetry were statistically correlated with keratoconus suspect, defined by higher asymmetry and steeper curvature on Placido topography.

Characterization of corneal structure in keratoconus

“…[14][15][16][20][21][22] Specifically, in keratoconus and also in keratoconus suspect, significantly larger values of BFS 14,16,21 and posterior elevation 15,16,22 have been reported (Figure 3). Schlegel et al 16 report a mean aconic astigmatism for the posterior corneal surface of 2.29 D G 1.71 (SD) in a sample of 48 keratoconussuspect patients using scanning-slit technology.…”

“…The term keratoconus suspect was coined for designating corneas not showing biomicroscopic keratoconic signs but subtle topographic features similar to early stages of keratoconus. [14][15][16][17][18][19] In such conditions, other diagnostic tests and examinations may be helpful to confirm the potential presence of an incipient ectatic condition.…”

“…There is evidence that both anterior and posterior curvatures are affected in keratoconic eyes and also in keratoconus suspect eyes. 20 Likewise, significantly larger values of best-fit sphere (BFS) 14,16,21 and posterior elevation 15,16,22 have been reported in clinical keratoconic eyes and keratoconus suspect eyes. Therefore, manifestations of the ectasia also occur at the posterior corneal surface, even in early stages of the disease.…”

Keratoconus: an inflammatory disorder?

“…30,31 The disease has been shown to be more prevalent also in patients searching for refractive surgery, as a consequence of self-selection bias, due to their refractive error. [33][34][35][36][37] A study in Colombia reported 3.9% prevalence in a group of patients that underwent an ophthalmic evaluation in a refractive surgery center. 37 In Yemen, prevalences of 15.5% of keratoconus and 9.4% of forme fruste keratoconus were found among refractive surgery candidates.…”

“…33 In a study in the United States, 25.5% of eyes evaluated for refractive surgery met the Rabinowitz criteria for keratoconus suspect. 34 A vast majority of the studies state that the age of onset of the disease is between 20 and 30 years. Some studies report a higher prevalence in male patients, whereas others indicate that there is no significant difference between genders.…”