Cataract Following Refractive Surgery
Patients who have undergone corneal refractive surgery and later develop a visually significant cataract present several unique challenges. Measurement of corneal power after refractive surgery is problematic, requiring multiple instruments and/or formulas to try to determine the new corneal power. Moreover, accurate axial length measurement (eg, with optical biometry) is required. Advanced IOL calculations are used to determine the appropriate power. (For a detailed discussion of IOL power calculation, see Chapter 7 in this volume and BCSC Section 13, Refractive Surgery.) Irregular astigmatism resulting from a refractive surgical procedure may compromise the ultimate vision outcome after cataract removal (Fig 12-3). Because unanticipated postoperative refractive results may occur, it is important to inform the patient about the limits of precision in lens power calculation and the possible requirement for postsurgical refractive correction to obtain optimal vision.
In general, postoperative hyperopia is more commonly encountered after cataract surgery in patients who have undergone previous refractive surgery. The corneal refractive incisions in eyes that have undergone radial keratotomy (RK) often swell after cataract surgery, thereby flattening the cornea and inducing hyperopia. Swelling may require more than 3 months to resolve. If a clear corneal incision is chosen, it should be placed between the RK incisions. Violating a prior RK incision can destabilize the wound, causing it to pull apart. The presence of multiple deep RK incisions or unstable wounds increases the likelihood of AC shallowing during cataract surgery and makes final closure of the wound difficult. Unless adequate clearance between RK incisions can be ensured with a clear corneal approach, a scleral tunnel incision is preferable to reduce the likelihood of violating an RK incision.
Figure 12-3 Accurate lens implant power is difficult to determine when the corneal surface is abnormal, as shown here by an irregular corneal topographic map (left) and distorted corneal rings (right, arrows).
(Courtesy of Lisa Rosenberg, MD.)
In eyes that have undergone laser in situ keratomileusis (LASIK), the surgeon should make the clear corneal cataract incisions posterior enough and avoid a long tunnel that could disrupt the LASIK flap. Corneal swelling after LASIK may require more than 1 month to resolve. Cataract surgery in eyes that have undergone photorefractive keratectomy (PRK) does not present the same type of technical challenges of surgery in post-LASIK eyes.
Because patients who have undergone refractive surgery may have corneal aberrations from the initial surgery, it is important to carefully assess the use of multifocal, extended depth of focus, or toric lenses.
Excerpted from BCSC 2020-2021 series: Section 11 - Lens and Cataract. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.