Corneal refractive surgery can eliminate or lessen a patient’s dependency on glasses or contact lenses. Many postoperative patients will require at least part-time correction if they experience regression or enter presbyopia. For these patients, contact lenses may be an option.
Molded frequently replaced soft contact lenses are designed to fit the virgin eye that has a prolate shape. By definition, corneal refractive surgery changes the shape of the cornea to correct refractive error.
For patients who have undergone hyperopic refractive surgery, the cornea maintains a prolate geometry, and lens selection is not necessarily limited. There is a geometry change from prolate to oblate for patients who have myopic refractive corneal surgery.
Relatively minor to moderate correction (5.00D or less) doesn’t necessarily cause enough shape change that it limits lens selection type (DeNaeyer, 2011). However, for every diopter of additional surgery, the corneal change can be enough that it will negatively affect lens performance of frequently replaced soft lenses. The mismatch between a molded soft lens and an oblate cornea can potentially cause distortion of the lens optics and lead to a less-than-ideal fitting relationship that results in failure.
For post-refractive surgery patients who are unable to successfully wear soft lenses, scleral contact lenses offer a solution. Scleral lenses vault over the cornea and fit to the part of the ocular surface that has been untouched by surgery.
A reverse geometry design should be utilized for oblate topographies to uniformly vault the corneal surface. Include front-surface toricity, if needed, to maximize acuity. Induced higher-order aberrations secondary to postoperative irregularity will be masked by the tear lens under the GP lens. Multifocal optics can be added for presbyopic patients.
Case in Point
A 70-year-old patient complained of decreased distance vision in his left eye 15 years after 10.00D of myopic laser-assisted in situ keratomileusis (LASIK) and two enhancements. Prior to LASIK, he wore GP lenses and had failed in soft contact lenses post-surgery secondary to fit issues.
At a recent follow-up exam, a 15.5mm scleral lens was designed directly from his corneo-scleral topography. The lens had 5.50D of reverse geometry to accommodate his oblate cornea and a spherical back surface haptic (Figure 1). The patient’s visual acuity with the lens measured 20/20, and he reported his vision to be “fantastic” with excellent lens comfort. The right eye was left uncorrected for monovision.
There is a significant niche of patients who have needed post-refractive surgery correction and want to wear contact lenses, but have been unsuccessful with soft lenses. Scleral lenses are not only an option, but might be the only type of lens that they can successfully wear. CLS
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