When should refractive surgery be avoided?

A panel of ophthalmologists gives an overall view of the main contraindications of LASIK and PRK.

MILAN — When should refractive surgery be avoided? This question was discussed in a symposium here during the 2001 Videorefractive meeting organized by Lucio Buratto, MD.

Maurizio Zanini, MD, the roundtable’s chairman, said there are few absolute contraindications to refractive surgery. In some cases particular techniques, but not all, should be avoided. In some other cases, LASIK might be preferable to photorefractive keratectomy (PRK) or vice-versa, and alternative solutions such as phakic IOLs or Intacs implantation can be used. At the moment, though, in most cases there are no definitive answers. The debate is still open, and often surgeons may have very different opinions on the same matter.

Corneal problems

In his review of possible contraindications, Dr. Zanini said that particular attention must be paid to the presence of corneal epithelium dystrophy and/or recurrent erosions.

“If these alterations are present, a corneal abrasion may occur during the passage of the microkeratome, and this may carry the risk of epithelial ingrowth. LASIK in such cases may also be the cause of pain, infections, late visual recovery and Sands of the Sahara syndrome,” he said.

Both phototherapeutic keratectomy (PTK) and PRK are otherwise considered by many authors beneficial to treat recurrent erosions and have been successfully used in patients with this type of problem.

Limbal neovascularization requires some precautions when performing LASIK. “Some bleeding may occur, but this should not be considered an absolute contraindication to LASIK. PRK, on the other hand, presents no problems at all,” he said.

Herpes keratitis, however, should always be considered as an absolute contraindication to refractive surgery, according to Dr. Zanini.

“Although there are studies demonstrating that PRK and PTK do not increase the incidence of relapses in these eyes, other authors show evidence that both techniques reactivate the herpes. Surgical trauma, UV radiation or topical steroids may function as a trigger. As for LASIK, there are no studies demonstrating the occurrence of relapses, but I agree with those (Buratto, Brint, Machat) who suggest avoiding the use of LASIK on these eyes,” he said.

Mind keratoconus

Keratoconus is usually a contraindication for both LASIK and PRK, due to the risk of inducing iatrogenic corneal ectasia.

“I never do refractive surgery on keratoconus patients,” said Thomas Kohnen, MD. “Cases of ectasia and irregular astigmatism have been reported by colleague surgeons after LASIK in eyes with form fruste keratoconus, and cases of decreased visual acuity have been reported in non-form fruste keratoconus. PRK is even more controversial. Some studies report a good percentage of visual improvement, but iatrogenic ectasia has also occurred in some cases after PRK. Personally, I recommend extreme caution.”

Alternative techniques seem to be more promising in this type of patients.

“Intracorneal ring segments (Intacs, KeraVision) have been reported to be effective in reducing astigmatism and improving visual acuity. They certainly have the advantage of not reducing the corneal thickness in these eyes,” Dr. Zanini said.

ELLKAT (excimer laser lamellar keratoplasty of augmented thickness) was also presented as a possible effective alternative.

Caution was also recommended in eyes with endothelial alterations.

“The endothelial cell loss that normally occurs after refractive surgery may not be significant and may also be transitory. However, in my opinion it would be better to avoid photorefractive surgery in eyes with fewer than 1,500 cells,” Dr. Zanini said.

Glaucoma and retinal breaks

According to Roberto Bellucci, MD, glaucoma is the most important issue when considering contraindications of refractive surgery.

“This is because many myopic patients suffer, or will in the future suffer from glaucoma, and our ability to measure IOP decreases after refractive corneal surgery,” he said.

LASIK may be contraindicated in glaucoma patients because of the sudden IOP spike induced by the suction. Further, in case of narrow angle glaucoma there is the risk of angle closure, which may occur also some months after surgery.

“Also, PRK may be contraindicated because steroid therapy increases the IOP,” he said.

Phakic IOLs, on the other hand, may cause pigment dispersion, especially in hyperopic eyes and pupillary block, he added.

Retinal breaks, if preoperatively treated, do not contraindicate LASIK and PRK, according to Dr. Zanini.

“Even a retinal detachment, if successfully operated in the past, is not a contraindication,” he said. He mentioned some cases of retinal detachment after LASIK that were reported by surgeons during the past 2 years.

“Often the retinal tears were located in areas that did not show alterations preoperatively. However, the incidence of this complication is low, and a cause-effect relationship has not been proved,” he said.

As far as retinitis pigmentosa is concerned, Dr. Zanini believes this may be considered a contraindication due to the risk of optic nerve damage and cystoid macular edema.

Systemic diseases

Among systemic diseases, collagenopathies represent an absolute contraindication to PRK, since they may be associated to stromal melting.

“I would advise against LASIK as well,” said Dr. Zanini. “We must also consider the high incidence of dry eye syndrome in collagenopathies and the increased possibility that LASIK causes in these eyes the LASIK-induced neurotrophic epitheliopathy.

Regarding diabetes, Dr. Zanini said there are no reports of complications of LASIK or PRK induced by diabetes.

“Nevertheless, we must remember that diabetic patients often have unstable refraction, which may affect preoperative evaluation. Their wounds also heal more slowly and their corneal epithelium is extremely brittle. The risk of infection is also much higher. These patients are also more exposed to early occurrence of cataract,” he said.

Pregnancy, keloids

The panel agreed that refractive surgery should never be performed in pregnant women.

“Cases of regression, haze and overcorrection have been reported after myopic PRK and, although there is little evidence that pregnancy causes alterations in LASIK, the Food and Drug Administration considers it a contraindication,” Dr. Bellucci said.

Additional factors should also be considered. First, pregnancy is associated with refractive fluctuations that hinder the preoperative evaluation of the refractive error. Second, after both PRK and LASIK there might be the need to prescribe drugs that might be dangerous for the baby. Keloids, according to recent studies, should not be regarded as a contraindication to refractive surgery, Dr. Zanini said.

“Wound healing complications were never detected in LASIK patients affected with keloids, and there is evidence that keloids do not interfere with the postoperative course of PRK,” he said.

Residual corneal thickness essential

Corneal thickness must be considered as an essential factor in both LASIK and PRK, according to the panel.

“The evaluation of the residual corneal thickness is crucial in order to prevent corneal ectasia,” said Michael Knorz, MD. “The residual thickness of the stromal bed after LASIK should be at least 250 µm, and 300 µm after PRK should be kept to be on the safe side. In the event of insufficient thickness, we have to consider all the available solutions, first of all the reduction of the diameter of the optical and transition zones.”

“The pachymetric maps provided by the Orbscan (Bausch & Lomb) provide us with reliable information concerning the recognition of cases at risk of keratectasia,” said Paolo Vinciguerra, MD.

According to Dr. Vinciguerra, alerting parameters are: a small bow-tie pattern on the axial map; a mean curvature higher than 50 D; an island pattern on the altitudinal map; an asymmetry between the steepest and the thinnest point of the pachymetric map; and a thickness less than 540 µm at the thinnest point.

Large scotopic pupils rule out both LASIK and PRK if the optical zone diameter is smaller than the pupil itself, according to Dr. Kohnen.

“The treatment zone should be at least as large as the scotopic pupil, and never smaller than 6 mm,” he said.

Dry eye, patients’ fears

Dry eye syndrome is considered by Dr. Zanini a relative contraindication to both LASIK and PRK.

“The denervation following LASIK can decrease the production of tears, and this condition may be worsened if the eye is dry preoperatively. As far as PRK is concerned, a pre-existing dry eye may affect the process of re-epithelialization,” he said. In his opinion, phakic IOLs and intraocular rings may be a better option in these eyes.

“I don’t think dry eye syndrome is a contraindication for LASIK,” argued Dr. Knorz. “On the other hand, dry eye is one of the most common complications of the technique, and more research should be carried out to find an effective treatment for it.”

As a closing topic, the psychological conditions of the patients were considered.

“Refractive surgery is not psychologically a problem for most patients,” Dr. Kohnen said. “However, the occurrence of a panic crisis can seriously jeopardize the outcome of surgery. Unexpected movements during the microkeratome cut or during ablation are bound to cause decentration of the flap and of the ablation. A good preoperative sedation can avoid this problem and make surgery easier.”

Dr. Knorz agreed. “I sedate 100% of my patients. I think it’s mandatory, as you can never be sure of your patient’s reactions during surgery. There is also another good reason to do so: patients will keep a good memory of the treatment, as they don’t feel the anxiety, and will come back more happily, if needed. It’s better for them and better for you!”

For Your Information:

• Maurizio Zanini, MD, can be reached at Centro Salus, Via Saffi 4/h, 40131 Bologna, Italy; +(39) 051-555-311; fax: +(39) 051-524-486; e-mail: salus@eyeproject.com. Dr. Zanini has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned.
• Roberto Bellucci, MD, can be reached at tel./fax: +(39) 036-543-678; e-mail: robbell@tin.it. Dr. Bellucci has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned.
• Paolo Vinciguerra, MD, can be reached at the Istituto Clinico Humanitas, Milan, Italy; +(39) 025-521-1388; fax: +(39) 025-741-0355; e-mail: vincieye@tin.it. Dr. Vinciguerra has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned.
• Michael Knorz, MD, can be reached at fax: +(49) 621-383-1984; e-mail: knorz@eyes.de. Dr. Knorz has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned.
• Thomas Kohnen, MD, can be reached at Johann Wolfgang Goethe University, Theodor Stern kai 7, Frankfurt am Mein, 60590, Germany; +(49) 696-301-6739; fax: +(49) 696-301-3893; e-mail: kohnen@em.uni-frankfurt.de. Dr. Kohnen has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned.