Fitting contact lenses after myopic keratomileusis

Abstract

After lamellar refractive surgery, the topography of the cornea is significantly altered. Although the postoperative keratometry readings are steeper than the actual curvature, they are reasonably reliable for determining the base curve of the initial trial lens, validating the use of conventional methods of fitting rigid contact lenses in patients who have had MKM.

Comparison of Axial and Tangential Topographic Algorithms for Contact Lens Fitting After LASIK

“…A large range exists in the literature, from fitting 0.1 mm to more than 0.4 mm (0.50 D to more than 2 D) steeper than the flat or mean postoperative keratometry value. 4,[15][16][17][18] Only two studies have used CVK maps to guide in the selection of base curves after b Significant and high correlation between gas-permeable lens base curve and corneal curvature.…”

“…In the traditional method of diagnostic trial lens application, simulated keratometry was used as a starting point for lens base curve selection. The formula used was based on findings from a study by Chou et al, 17 who fitted a series of patients after myopic keratomileusis with GP lenses on average 1.3 diopters (D) steeper than the mean postoperative flat keratometric reading. Once the diagnostic lens was applied, the fit was titrated to achieve central clearance, alignment in the mid periphery, and a peripheral band of 2 to 3 mm of adequate axial edge lift to provide even corneal clearance but not enough to break the tear meniscus.…”

“…9 -11 Several studies in the literature that discuss methods for fitting patients who have undergone photorefractive keratectomy (PRK) or LASIK use manual keratometric readings for base curve selection. 4,[12][13][14][15][16][17][18] Because CVK has become the standard method to measure the corneal curvature after LASIK, we sought to find the optimal use of CVK data to which clinicians should refer when fitting GP lenses.…”

Contact lens fitting following unsuccessful refractive surgery

“…As such, no adverse physiological problems such as oedema were identified with contact lens wear in this study. As with PRK, most authors advocate the use of rigid gas permeable lenses in post‐LASIK eyes (Szczotka and Aronsky, 1998; Chou et al , 1999; Bufidis et al , 2000; Ward, 2001).…”

“…Excessive central pooling, poor stability and centration may occur with conventional rigid gas permeable (CRGP) lenses because the corneal topography is typically flatter centrally. Some studies have, however, reported success with the use of CRGP and soft contact lenses after refractive surgery (Shipper et al , 1995; Astin et al , 1996; Lee and Kastl, 1998; Chou et al , 1999; Lim et al , 1999; Ward, 2001). When a larger refractive error is attempted (>−7 dioptres), the ablated zone may be wider and deeper, which makes lens fitting even more challenging (Astin et al , 1996; Chou et al , 1999; Astin, 2000).…”