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Options abound in refractive surgery spectrum

Careful evaluation will match each patient with the appropriate refractive surgical procedure.

In the past decade we have seen the convergence of refractive surgery with cataract surgery, which makes sense because the most commonly performed refractive procedure is phacoemulsification with IOL implantation. Corneal-based refractive surgery has evolved, with precise treatments with excellent outcomes. We are also learning more about phakic IOLs and newer devices such as intracorneal inlays. The key to success is to select the best refractive surgical procedure for each patient.

LASIK, PRK, phakic IOLs

LASIK and PRK have a long track record for success with excellent visual outcomes and very low risk as long as the patient is a strong candidate. The newer femtosecond lasers are able to create LASIK flaps that are far more accurate and predictable than using a bladed microkeratome. There are, however, the rare patients in whom a microkeratome may be preferred, such as those with corneal scars and perhaps some patients with prior radial keratotomy. Femtosecond lasers have improved considerably in both speed and quality of the flaps created, with complete treatments under 30 seconds with minimal issues with opaque bubble layers. Patients who meet topographic, tomographic and pachymetric criteria can do well with femtosecond laser-created LASIK flaps.

While the approved range of treatment for the current generation of excimer lasers is very wide, having a more conservative approach may be safer and produce better quality vision. Limiting the upper range of myopic treatments, which flatten the central cornea, to the –9 D or –10 D range will result in better residual bed thickness as well as better quality vision. Hyperopic treatments are more challenging because the cornea must be steepened by peripheral corneal ablation, which limits the upper range to about the +3 D or +4 D range to keep maximum visual quality even though the laser may be approved for higher treatments. PRK can be a good option for patients who want an alternative to LASIK, but it works far better in myopic ablations compared with hyperopic treatments.

For ultra-myopic patients, phakic IOLs can be an option, although there can be downsides. Anterior chamber phakic IOLs, which are fixated to the iris, can induce corneal endothelial cell loss, and they require a large incision for implantation. Posterior chamber phakic IOLs, which are placed behind the iris but in front of the crystalline lens, can induce cataracts in as many as 40% of patients within 5 years, according to a recent Swiss study.

Figure 1. Four years after implantation, this posterior chamber phakic IOL has induced an anterior cataract. The phakic IOL and cataract will both be removed and replaced with an IOL in the capsular bag.

Images: Devgan U

Figure 2. This 61-year-old highly hyperopic patient elected to have a refractive lensectomy with placement of a multifocal IOL. Although she had some nighttime halos while driving, she was absolutely thrilled with her visual outcome and freedom from glasses.

Cataract surgery with IOL implantation

If the patient has any degree of cataractous changes, it does not make sense to do LASIK or phakic IOLs. These are typically patients in their 60s who already have a degree of nuclear sclerosis. Even though they can be corrected to 20/20 with a refraction, LASIK surgery should be avoided because these patients will be able to achieve the same correction or even better correction with cataract surgery.

Cataract surgery can correct an immensely large range of dioptric powers while maintaining excellent visual quality. With IOL powers available from –10 D to +40 D, the refractive errors that can be addressed range from about –30 D to +15 D at the spectacle plane. While the risks of IOL surgery are low, be aware that very myopic patients may have additional risks with retinal detachment, and all patients with extreme eyes may have less accurate IOL calculations.