Partial thickness PTK improves healing in recurrent corneal erosion patients
Roibeard ó'hÉineacháin
in Munich
Mike Holzer
A phototherapeutic keratectomy (PTK) technique that leaves the internal layers of the epithelium intact can provide recurrent corneal erosion patients with a faster and less painful recovery without any refractive change. The use of autologous serum in place of artificial tears can further enhance the healing process, according to a German ophthalmologist.
The procedure, called transepithelial PTK (t-PTK), involves the excimer laser ablation of the outer 20-30 microns of the central 7.0 mm of the corneal epithelium,
Mike Holzer MD told the XXI Congress of the ESCRS. "If you do a standard PTK what you do is remove the whole of the epithelium down to the depth of Bowman's membrane and let the epithelium grow back. The re-growth can take up to 2-3 days, during which time patients can be in pain that is at least equal to that of a bad toothache. An additional problem with standard PTK is that if you go a little too deep you might induce some kind of hyperopic shift and scarring of the cornea."
In a study involving 25 eyes of 25 patients with recurrent corneal erosions who underwent t-PTK, 20 eyes were free of any further recurrence during a follow-up period of six to 20 months. Moreover, the average time to epithelial re-growth was only one day, after which time patients had no further pain. In addition, the technique did not induce any refractive changes in any eyes.
"There were no recurrent erosions in 80% of eyes, which was similar to published results with standard PTK. We also saw no change in refraction after the procedure, which might have occurred if we had performed a conventional PTK. So t-PTK may be a safer procedure." Of the five eyes that had recurrences after t-PTK, one eye had an erosion induced during removal of the lid speculum and another eye had a recurrence due to non-compliance with the postoperative autologous serum eyedrop regimen. Only one eye with a recurrence required a repeat t-PTK, and in the remaining four eyes the recurrences resolved with the eyedrop regimen alone.
Dr Holzer and his associates performed the t-PTK procedure with the Schwind Keratom excimer laser. They applied 2x 40 pulses to achieve an ablation depth of 20-30 microns into the epithelium. Postoperatively, patients received a regimen of autologous serum eye drops, which they applied six times a day for a minimum of six weeks.
The autologous serum eyedrops may promote epithelial healing to a greater extent than either the natural tear film and commercially produced artificial tears. They may also be of particular benefit to patients prone to corneal erosions, he noted.
"Autologous serum eyedrops have been described before in the treatment of severe dry eye. As recurrent corneal erosion patients often have dry eyes you can use the drops to treat their dry eye syndrome as well as to help heal the cornea. The eyedrops have 10 times higher concentration of fibronectin and a 2,300 times higher concentration of Vitamin A than the normal tear film. Also the drops do not have any preservatives and therefore do not induce allergic reactions."
Preparation of the autologous serum eyedrops is a simple and inexpensive procedure, Dr Holzer noted. It involves taking 50 ml of blood from the patient, placing it in a centrifuge and pouring the supernatant serum into eyedrop bottles. A 50 ml blood sample is sufficient to produce three bottles of eyedrops or about three weeks supply."As they have no preservatives they have to be stored in the refrigerator and we tell patients to be very careful not to touch the eye. The drops may be produced in your own office. In LASIK patients you might use it as artificial tears as some patients need artificial tears for several months."
r Holzer noted that since the trial did not compare the results with and without the serum eye drops it was difficult to say how much each component of the treatment contributed the rapid epithelial healing they observed. "Based on our findings we would advise surgeons to use t-PTK as their primary surgical intervention in patients with recurrent corneal erosions and only perform a conventional PTK if the results are unsatisfactory. The use of autologous serum eyedrops is part of our practice style and we find that they are a very well tolerated, easily produced, and inexpensive form of artificial tears," he added.
Dr Holzer's presentation was awarded first prize in the refractive category of the XXI ESCRS Congress poster competition.
