AN ESTIMATED 20 to 25 million laser-assisted in situ keratomileusis (LASIK) procedures have been performed in the U.S. since the lasers were approved by the U.S. Food and Drug Administration (FDA) in 1999 (Joffe, 2021). The LASIK boom was about 10 to 20 years ago, and many patients at that time enjoyed correction-free vision, that is until they developed presbyopia or eventual ametropia due to gradual cataract formation as they aged.

These patients are often disappointed that they need visual correction again, but they areusually highly motivated to avoid glasses and consider contact lenses (CLs). Often, due to their past familiarity with soft CLs (SCLs), they expect this to be an easy solution for their visual needs.

However, postoperatively, especially for those patients who had previous myopic ablations, the cornea now has an oblate geometry rather than a prolate one. Standard SCLs are designed to fit prolate corneas of patients who fall in the center of the bell curve for shape and size; this now excludes those patients whose corneas have been surgically altered.

This means that, depending on the difference present between the flat central cornea and the steeper midperipheral cornea, standard SCLs may no longer fit appropriately or achieve desirable vision, making the task of refitting more challenging for the eyecare practitioner.

For low-powered uncomplicated corrections, and corneas with smaller differences in central cornea versus peripheral cornea curvatures, standard SCLs may work well. A low-modulus material is preferred, as it has a better chance of conforming to the irregular shape of the cornea and draping more easily (Steele and Davidson, 2007).

In Figure 1, this patient’s 1990 preoperative prescription was –4.00D OD and –3.25D OS. His current refractive error is +0.75D OD and –1.50 –0.50 x 175 OS, and he’s been noticing a decline in his distance vision. He is right eye dominant and was successfully fit with hydrogel daily disposable CLs with a 9.0mm base curve (BC) in both eyes to wear for sports; while at work, he would wear a CL in his right eye for monovision.

However, the challenge in fitting really arises when there is a significant difference between the central and peripheral corneal curvatures, such as that seen in a patient who was highly myopic prior to refractive surgery (Figure 2 available online). The mismatch between the sagittal height of the posterior surface of the standard SCL and the flatter anterior corneal surface will often result in excessive vault over the central cornea, leading to variable vision upon blinking, strange over-refractions, and unstable toric lens rotation (Gonzalez-Meijome et al, 2006).

In situations such as this, a custom soft lens that incorporates a reverse-geometry design will align better and provide more consistent vision. These lenses are designed with a flatter central base curve and a steeper peripheral curve.

The patient in Figure 2 self-reported as a –9.50D myope prior to photorefractive keratectomy (PRK) 10 years ago and now had a refractive error of –1.50sph in both eyes. She wanted to wear CLs for her upcoming wedding but had failed with numerous standard SCLs and was told she couldn’t wear CLs again. She was successfully fitted with a custom reverse-geometry soft lens with a 9.0mm central BC, 8.4mm peripheral curve, 15.0mm diameter, and –1.00sph OD and OS.

Post-refractive surgery patients can be some of the more challenging patients to refit into contact lenses. With the customizations available today, SCL success can be achievable for these patients, but sometimes it requires utilizing “off-the-shelf” designs.

REFERENCES

1. Joffe SN. The 25th Anniversary of Laser Vision Correction in the United States. Clin Ophthalmol. 2021 Mar 17;15:1163-1172.

2. Steele C, Davidson J. Contact lens fitting post-laser-in situ keratomileusis (LASIK). Cont Lens Anterior Eye, 2007 May;30:84-93.

3. González-Méijome JM, Sañudo-Buitrago F, López-Alemany A, Almeida JB, Parafita MA. Correlations Between Central and Peripheral Changes in Anterior Corneal Topography After Myopic LASIK and Their Implications in Postsurgical Contact Lens Fitting. Eye Contact Lens. 2006 Jul;32:197-202.