Match patients’ needs to refractive surgery option

When it comes to referring patients for refractive surgery, numerous choices in surface and lens procedures for customized treatment are available. To make an informed recommendation, optometrists first need to know the options.

Corneal-based refractive surgeries include LASIK, photorefractive keratectomy (PRK), conductive keratoplasty (CK), laser-assisted in situ epithelial keratomileusis (LASEK) and epi-LASIK.

Sondra R. Black

“Nearly all the procedures we perform are corneal procedures,” Sondra R. Black, OD, clinical director at TLC Laser Eye Center of Toronto, said in an interview. About 80% are LASIK and about 20% PRK, she said.

The center also performs custom ablation on every patient, using the Intralase (Irvine, Calif.) laser for creating the corneal flap. “This allows us more options for patients with thinner corneas because we are able to make a thinner flap with the Intralase,” Dr. Black said.

The eye center is involved in clinical trials of presbyopic laser surgery with Visx/Advanced Medical Optics (Santa Clara, Calif.). Results from the hyperopia segment “are very good,” Dr. Black said. “We are waiting for Canadian approval to go forward with this as a conventional treatment.”

The myopic arm of the study is in progress.

CK, LASEK, epi-LASIK

“With epi-LASIK, we actually remove the epithelium with an epi-keratome,” Richard L. Lindstrom, MD, of Minnesota Eye Consultants in Minneapolis told Primary Care Optometry News in an interview. “This is demonstrating some benefits in both rate of visual rehabilitation and rate of epithelial wound healing. Patients experience less pain and morbidity.”

As a LASIK surgeon, Dr. Lindstrom’s first choice in surface procedures is Intralase custom LASIK with the Visx laser. “This combination has provided me the best outcomes,” he said. “Our studies show a more rapid visual recovery.”

Richard L. Lindstrom

The studies also suggest a biomechanically strong cornea after the procedure, as well as a more consistent reproducible flap and a lower rate of flap complications.

Dr. Lindstrom, also a Primary Care Optometry News Editorial Board member, noted that within the next 6 months, Visx/AMO is scheduled to launch a transepithelial laser for surface ablation. “You will be able to treat through the epithelium with the excimer laser,” he said. “This should be a pretty attractive option. The outcome will likely be similar to the epi-microkeratome epithelial removal.”

About 15% of patients at Minnesota Eye Consultants require a surface option other than LASIK, primarily because of abnormal topography, thin cornea, recurrent erosions or superficial scarring, Dr. Lindstrom said. The practice occasionally performs CK for presbyopia, astigmatism and select cases of hyperopia. Astigmatic keratotomy is also scheduled occasionally.

IOL choices

The armamentarium of IOLs at Minnesota Eye Consultants includes standard monofocal lenses, aspheric lenses, multifocal lenses, toric lenses and an accommodating lens. “I favor the aspheric lenses when I am not using a ‘premium channel’ presbyopia-correcting IOL,” Dr. Lindstrom said. “I also like a toric lens for significant astigmatism.”

Dr. Lindstrom also prefers combining an accommodating lens with a mini-monovision approach as opposed to implanting a multifocal IOL.

Phakic IOLs “are definitely a good option” for patients who are highly myopic (over -10 D) who lack sufficient corneal thickness, Dr. Black said. “However, patients prefer a corneal procedure because they feel it is safer than an intraocular procedure,” she said. “In fact, only about 1% of our overall refractive procedures are lens-based procedures. The best patients for a refractive lensectomy are the very high hyperopes.”

However, her center will not perform a corneal procedure in a hyperope who is over +4 D. Likewise, a 20-year-old hyperope “is rarely a candidate for any refractive procedure,” Dr. Black said. “There is too great a risk for dry eye and healing abnormalities as well as the issues with accommodation.”

Similarly, a high myope should refrain from a refractive lensectomy because of the higher risk of retinal detachment associated with myopes. “High myopes should consider a phakic IOL,” she said.

PRK vs. LASIK

When choosing between PRK and LASIK, influencing factors include corneal thickness, corneal shape and degree of asymmetry.

A thinner cornea should be treated with PRK. “If a patient has pachymetry under 500 microns we discuss PRK as our procedure of choice. That is where we draw the line for LASIK,” Dr. Black said.

Corneas 480 microns or less tend to have surface ablation at Minnesota Eye Consultants. Corneas that show abnormal topography or any evidence suggesting forme fruste keratoconus will generally have surface ablation rather than intraocular surgery. Patients with anterior basement membrane dystrophy (ABMD) are candidates for surface ablation as well.

However, Minnesota Eye Consultants performs no excimer laser refractive surgery on myopia over -12 D and rarely over -10 D. The limits for hyperopia are usually over +4 D and rarely over +3 D, Dr. Lindstrom said.

“If the patient is slightly asymmetrical, we feel it is safer to perform PRK and not go as deep,” Dr. Black added.

Patients with a tendency towards dry eye will also generally do better with PRK, she said. There are also those paients who are afraid of the flap with LASIK and prefer the PRK option. Patients with any type of ABMD will also be scheduled for PRK rather than LASIK.

As for the final visual outcomes from PRK and LASIK, “the average patient with the average prescription and average corneal thickness should see no difference,” Dr. Black said. “Our efficacy has been good for both procedures when using custom ablation.”

Intraocular refractive surgery seldom performed

Although surgeons at TLC Laser Eye Center of Toronto seldom perform intraocular refractive surgery, “some surgeons perform it frequently,” Dr. Black said. “It all depends on the surgeon and his or her comfort level. Some consider a phakic IOL as soon as the patient reaches a -8 D.”

According to Dr. Lindstrom, last year about 1.4 million excimer laser treatments were performed in the United States and only about 60,000 refractive lens exchanges. At his practice, 1% to 2% of refractive procedures are phakic IOLs and 3% to 4% clear lensectomy. Multifocal or accommodating lenses are implanted into about 8% to 10% of cataract patients.

“Do patients want the best possible distance vision and are they happy wearing reading glasses?” Dr. Lindstrom said. In these cases, an aspheric IOL may be appropriate. Other times, a different kind of lens will be implanted in each eye to create monovision.

“A lot of combinations are available,” Dr. Lindstrom said.

At the TLC center, only about 0.5% of procedures involve phakic IOLs, 0.5% clear lensectomy and few multifocal IOLs. “Our surgeon tends to still favor a monofocal lens,” Dr. Black said.

Contraindications

According to Dr. Black, the most common postoperative issue with phakic IOLs has been cataracts. “You then have a very high myope who requires a clear lens extraction,” she said. “The risk with such an extraction is retinal detachment. Even though the risk is small, it can be a serious complication.”

A clear lens extraction is also not advised for a young patient with full accommodation. “You can make them see well at distance, but you don’t want a 25-year-old to be totally dependent on reading glasses,” Dr. Black said.

The major problem with multifocal lenses appears to be night glare issues, she said. She also anticipates more research on accommodative lenses. “This may be the wave of the future for a clear lens extraction,” she said.              

For more information:

• Sondra R. Black, OD, can be reached at 4101 Yonge St., Ste. 100, Toronto, Ontario M2P1N6, Canada; (416) 733-2020; fax: (416) 733-0316; e-mail: sondra.black@tlcvision.com. She has no direct financial interest in the products mentioned in this article, nor is she a paid consultant for any companies mentioned.
• Richard L. Lindstrom, MD, can be reached at Minnesota Eye Consultants, 710 E. 24th St., Minneapolis, MN 55404; (612) 813-3633; fax: (612) 813-3660; e-mail: rlindstrom@mneye.com. Dr. Lindstrom is a consultant for AMO, Intralase and Visx.