Imagine that a surgeon could remove an appendix or unclog a coronary artery without cutting into the skin. It would pay a number of dividends: anesthesia risks would decrease, iatrogenic infection rates would drop to zero, and the recovery period would be much easier, just to name a few. Such surgery may sound like science fiction, but one femtosecond laser has been able to perform intrastromal treatments to correct refractive error while leaving the outside of the eye intact.
The procedure has been performed primarily for presbyopia using the Femtec laser (20/10 Perfect Vision,
It avoids the problems with a flap and avoids the problems with surface ablation, says Luis Ruiz, M.D., of
Its completely intrastromal, he says. We dont touch epithelium, Bowmans, Descemets or the endothelium. The idea is to do a treatment by which we can change the biomechanics of the corneal stroma and change the shape of the cornea.
To perform the procedure, Dr. Ruiz enters patient data into the laser, including keratometry, hysteresis values, refraction and corneal thickness. The system then develops a customized photodisruption pattern for that patient.
Femtecs maker says the laser uses a proprietary fixation approach with a curved patient interface. The interface is essentially a sterile, disposable, curved contact lens. It is placed on the application end of the femtosecond laser and fixates on the cornea with a suction ring.
In a study of 59 mostly emmetropic and hyperopic patients who underwent the intrastromal procedure, patients went from about 20/70 pre-op (or about J8) to about 20/25 (or a little better than J3) at one month post-op. The procedure also preserved the patients uncorrected distance vision.
The procedure is so innocuous that some patients wonder if anything has been done. Because we dont have a wound, theres no chance of infection, Dr. Ruiz says. Thin corneas arent a contraindication unless its actually keratoconus, and we dont have to worry about dry eye post-op. Its a very simple procedure.
Dr. Ruiz says his main question at first was about stability. When I saw the first group of patients on the first day, they did very well But, when we saw them at one week, one month, two months, and three months, theyre the same as the first day post-op. Still, further follow-up is needed, he says.
Also, the patients quality of vision has been good. A number will have halos for one to one-and-a-half months post-op, but they dont complain about them, he says.
For myopes and hyperopes, Dr. Ruiz is taking small steps with the procedure. Were working with myopia of -2.50D or less and hyperopia up to +2.50D to +3.00D. Well have to study the procedure for two to three years, Id say, to know its real limits.
