Reliability and repeatability of swept-source Fourier-domain optical coherence tomography and Scheimpflug imaging in keratoconus

Abstract

No author has a financial or proprietary interest in any material or method mentioned.

New clinical pathways for keratoconus

“…Keratometry measurement repeatability in keratoconic eyes (stage II, 3 mm zone steep Kr53D) has been shown to be significantly poorer than in normal corneas, with a 1D CoR for steepest keratometry (Kmax) using Fourier-domain anteriorsegment OCT (Casia SS-1000 Tomey Corp., Nagoya, Japan) and 1.5D using a Scheimpflug-based imaging device (Pentacam HR, Oculus GmbH, Wetzlar, Germany). 16 This compares with CoR values in normal corneas of o0.5D for both imaging devices. 16 Based on this, a change in Kmax of þ 1.5D vs measurement at presentation on Pentacam image comparison maps may be a useful contemporary threshold indication for CXL using a widely available corneal tomography device.…”

“…16 This compares with CoR values in normal corneas of o0.5D for both imaging devices. 16 Based on this, a change in Kmax of þ 1.5D vs measurement at presentation on Pentacam image comparison maps may be a useful contemporary threshold indication for CXL using a widely available corneal tomography device. A lower threshold ( þ 1D vs baseline Kmax) is used in contemporary studies (Table 2).…”

“…Spontaneous disease regression does not normally occur in keratoconus, and apparent disease regression (decrease in KmaxZ1D) in 10% of control eyes in RCTs may simply reflect limitations in measurement accuracy for contemporary topographers 16 -a problem compounded by corneal warpage in rigid contact lens Table 2 Criteria for keratoconus progression vs baseline measurement used in contemporary clinical trials of corneal collagen crosslinking 14,18,21 Kmax Z1D increase Kmax À Kmin Z1D increase Kmean Z0.75D increase Pachymetry Z2% decrease in CCT Corneal apex power 41D increase MRSE 40.5D wearers. These limitations and varying inclusion criteria (Table 2) in contemporary studies underline the problem of defining disease progression in keratoconus and defining thresholds for intervention.…”

Evaluation of the anterior chamber angle in keratoconus and normal subjects

“…It follows that peripheral structural alterations and changes in the corneal curvature may modify its relative relationship to the uvea. The corneal ectasia, as one would expect and as is well documented [13][14][15] will demonstrate an anterior chamber depth that increases with KC. However, this finding does not describe the changes that may occur in the peripheral regions of the cornea in KC.…”

“…An evaluation of the anterior chamber angle in KC subjects is most frequently screened during biomicroscopy using van Herick's technique. However, this technique may induce errors since the anterior chamber depth may be influenced by localized apical protrusion and thinning which would increase the measured depth thus giving a false impression of the angle [13][14][15]. In cases of suspected narrow angles, the measurement can be more accurately determined using gonioscopy, which is a more invasive procedure for the ocular surface.…”