PTK reduces bullae formation, pain after cataract surgery

May 15, 2006

All of the PTK-treated eyes experienced pain relief that persistedthrough follow-up.

New Delhi, India-In eyes with nonresolving corneal edema after cataract surgery, phototherapeutic keratectomy (PTK) appears to be effective for preventing progression to bullous keratopathy and for decreasing pain, reported Jeewan Titiyal, MD.

He presented the results of a prospective, randomized study conducted at the RP Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India. The trial included 17 patients who underwent PTK with a 100-μm ablation and compared their outcome with 15 patients who received treatment with topical hyperosmotics.

Bullae were absent at study entry in all eyes, and developed in only a single PTK-treated eye (5.9%) during 1 year of follow-up. In contrast, bullae developed in 12 (80%) of 15 eyes in the control group.

"These results suggest PTK may be considered as an alternative mode of therapy for patients with nonresolving corneal edema due to corneal decompensation after cataract surgery while they are awaiting their turn for penetrating keratoplasty. Considering the paucity of donor tissue in developing countries, this technique may have particular importance in those areas of the world," said Dr. Titiyal.

To be eligible for enrollment in the study, patients had to have nonresolving corneal edema present for at least 3 months. Other inclusion criteria required corneal thickness in the affected eye to exceed 600 μm or be increased by 30% relative to the fellow eye or preoperative thickness. In addition, patients had to have controlled IOP and intraocular inflammation.

The PTK procedure was performed with a standard technique using topical anesthesia and 0.5% proparacaine. The epithelium was first mechanically debrided, and the PTK ablation was performed at a 6-mm optical zone. Postoperatively, patients wore a bandage contact lens and used tobramycin four times a day and artificial tears every 4 hours. Topical hyperosmotic treatment was not allowed.

Patients in both study groups had a mean age of about 60 years and were, on average, 1 year postcataract surgery. Mean pachymetry at baseline was also similar in the PTK and non-PTK groups, 781 and 771 μm, respectively. Patients who underwent PTK had a slightly longer mean duration of symptoms compared with the controls, 9.0 versus 6.5 months, respectively.

In the PTK group, pachymetry was reduced from 781 μm at baseline to 672 μm 1 month after the ablative treatment. At 3 months, there was a slight further reduction in mean pachymetry to 644 μm while it increased to 664 μm at 6 months and remained at about that level after 1 year. In contrast, pachymetry increased progressively throughout follow-up in the non-PTK group with an average total increase of about 100 μm at 6 months after study entry.

At the 1-day postop visit, patients who underwent PTK experienced an improvement in visual acuity, although the benefit disappeared by 1 month. At that visit and throughout the rest of the study, mean visual acuity was similar to the pretreatment level. Patients using the topical hyperosmotics had no change in visual acuity throughout the study.

None of the non-PTK patients developed a scar. However, by 1 year, a scar was present in 12 of 17 eyes that underwent PTK.

Dr. Titiyal noted that PTK has been used successfully to treat pseudophakic bullous keratopathy. In that application, its benefits were measured by reduction in pain and bullae recurrence. Its mechanism of action in achieving those results is thought to be multimodal.

"Pain is mitigated as a result of ablation of the subepithelial nerve plexus. In addition, by ablating Bowman's membrane, the procedure results in increased adhesion between the epithelium and stroma, thereby reducing bullae formation. By reducing corneal thickness, the procedure is also thought to reduce the osmotic workload on the endothelium to enable the efficacy of dehydration by the remaining endothelium and thereby reduce epithelial edema and decrease or stabilize corneal thickness," Dr. Titiyal said.