Effect of Scleral Lenses on Corneal Topography in Keratoconus: A Case Series of Cross-Linked Versus Non-Cross-Linked Eyes (original) (raw)

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 mm) to 5 hours (458 mm) 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. A scleral contact lens (SL) is a rigid gas permeable lens that rests exclusively on the bulbar conjunctiva vaulting the cornea and the limbus. Using this type of lens geometry, a tear fluid reservoir, often referred to as "lens clearance," is created between the posterior lens surface and the anterior surface of the cornea. This liquid layer created underneath the SL acts as an optical lens neutralizing both regular and irregular corneal astigmatism, and optical aberrations generated by the anterior cornea, thereby improving vision. 1,2 Visual improvement is one of the primary indications for SL fitting, in particular, for optical rehabilitation of keratoconus (KC), other forms of corneal ectasia and after keratoplasty. 3,4 In addition, the postscleral lens tear fluid reservoir hydrates the underlying ocular tissues providing relief and treatment for a variety of ocular surface diseases, such as severe dry eye, neurotrophic keratopathy, and corneal scarring. 5 Since the advent of rigid gas permeable (RGP) contact lenses (CLs), it was widely described in the literature that both the geometrical shape and physiology of the cornea might be significantly altered by corneal CL wear. Numerous factors such as desiccation, mechanical rubbing with consecutive corneal microtrauma, and suboptimal corneal oxygen-ation are thought to cause these changes. 6,7 Rigid lens wear-related corneal warpage leads to a shift in central keratometry, corneal asphericity, and low-order and high-order aberrations, contributing to decreased retinal image quality. 7,8 Recovery time is highly variable and correlates with daily wearing time and overall length of RGP wear. 9 To date, little is known regarding the effect of scleral lens wear on corneal geometry. Recently, several researchers have studied the influence of SL wear on corneal topography in normal 10-13 and keratoconic eyes. 14-16 According to reports, the shape of the anterior and posterior corneal surfaces seems to be flattened and modified by SL wear, despite the fact that SLs do not have any mechanical interaction with the underlying corneal tissue.