Our contact lens toolboxes are limited when it comes to providing optimal, non-customized correction for astigmatic presbyopes. Add to the mix the corneal profiles belonging to post-refractive surgery patients (Figures 1 and 2), and we can almost guarantee that an off-the-shelf contact lens will be inadequate for providing the best quality of vision. What factors work against us and may limit contact lens fitting success?
Post-Refractive Surgery Factors that Affect Lens Fitting Success
- Corneal Shape After refractive surgery—such as laser-assisted in situ keratomileusis (LASIK) to correct myopia, for example—the anterior surface of the cornea takes on a new shape and becomes more oblate, with a flattened central treatment zone area and paracentral steepening relative to the apex. This change in shape can affect stabilization of a soft multifocal toric contact lens on the eye.
- Corneal Aberrations Higher-order aberrations can sometimes increase following refractive surgery. Introducing soft multifocal toric optics to an already compromised visual system can lead to a loss of low-contrast acuity as well as to excessive symptoms of glare and halos, especially during night driving.
- Tear Film Instability Postoperative dry eye is a known complaint of many post-refractive surgery patients. This discomfort coupled with unsatisfactory acuity will further limit contact lens management in these cases.
A Clinical Alternative
Hybrid multifocal contact lenses designed for normal eyes can be empirically ordered based on keratometric readings, horizontal visible iris diameter, pupil size, and spectacle prescription for the type of straightforward post-refractive surgery eyes such as those in Figures 1 and 2. While post-refractive surgery corneas deviate from the typical prolate shape of a regular eye, the spherical GP central portion of a hybrid lens can correct low-to-moderate amounts of corneal cylinder with the underlying tear lens.
Determine a patient’s dominant eye and add power in-office and decide whether center-near, center-distance, or a combination of both optics at what zone size will best suit the patient’s needs. The high-Dk GP center and silicone hydrogel soft skirt promote a healthy supply of oxygen to the corneal surface. If there is poor surface wetting of the hybrid lens secondary to poor tear quality, a surface coating can be applied to the lens to improve lens surface wettability and overall comfort with lens wear.
For post-refractive surgery patients who require a multifocal toric correction and who present with corneal cylinder upwards of –4.00D, your chances of the lens successfully remaining stable on the eye and providing accurate vision go down, and alternative methods of contact lens correction should be pursued. However, for low-to-moderate amounts of regular corneal astigmatism in post-refractive surgery patients, keep in mind that hybrid multifocal lenses can be successfully fit in this distinct clinical population. CLS