Study: How scleral lenses affect corneal shape in keratoconus patients
Effect of Scleral Lenses on Corneal Topography in Keratoconus. A Case Series of Cross-Linked Versus Non–Cross-Linked Eyes Severinsky et al, Cornea, May 21 2019
Purpose: To evaluate the changes in anterior corneal topography induced by short-time wear of scleral contact lenses (SLs) in keratoconic subjects with and without a history of corneal cross-linking (CXL).
Methods: Nine keratoconic patients (14 eyes) were fitted with 18.5 mm SLs for optical rehabilitation. Subjects were divided into 2 groups: 7 eyes without a history of CXL (Non-CXL group) and 7 with a history of CXL (CXL group). Corneal topography was performed at baseline and after 2 and 5 hours of lens wear. The differences for simulated flat (Kflat), steep (Ksteep) and maximal (Kmax) corneal curvatures, central corneal astigmatism (CCA), and central cornea thickness were evaluated.
Results: No statistically significant difference was detected between Non-CXL and CXL groups in any of these measures. Statistically significant flattening was detected in Ksteep Repeated measures analysis of variance ([RM-ANOVA), F (2,24) = 11.32, P < 0.0001], CCA [RM-ANOVA, F (2,24) = 15.34, P < 0.0001], and Kmax [RM-ANOVA, F (2,24) = 19.10, P < 0.0001). From baseline to 5 hours of SL wear, Ksteep decreased on average from 53.1 to 52.4 D, Kmax decreased from 56.7 to 55.8 D, and CCA decreased from 7.2 to 6.3 D. Kmax showed a trend toward more flattening in the Non-CXL group. Central cornea thickness showed significant thickening over time from baseline (451 μm) to 5 hours (458 μm) of SL wear [RM-ANOVA, F (1,12) = 319.3, P < 0.0001].
Conclusions: Short-term scleral lens wear in keratoconic patients may cause flattening of the anterior cornea. A history of CXL treatment does not guarantee corneal shape stability after scleral lens wear. Practitioners should be aware of these changes because scleral lens wear may mask the signs of keratoconus progression.