Macular thickness remains stable after DALK, increases short-term after PK, study shows

Am J Ophthalmol. 2011;152(5):756-761.

Issue: January 10, 2012

Mean macular thickness showed a short-term increase after penetrating keratoplasty but did not change after deep anterior lamellar keratoplasty, a study found.

"Theoretically, given that there is almost no intraocular manipulation during DALK, the risk of macular edema after DALK surgery would be expected to be lower than that of [PK]," the study authors said.

The prospective study included 60 eyes of 60 patients with keratoconus who underwent routine corneal transplantation. DALK and PK were each performed in 30 eyes.

Mean patient age was 25.3 years in the DALK group and 26.2 years in the PK group.

Eyes with significant corneal scarring, cataract, graft rejection, iris or pupil abnormalities, glaucoma, retinal/macular disease, or previous intraocular surgery were excluded.

Investigators assessed corrected and uncorrected visual acuity, refraction, biometry, pachymetry and tonometry, and used spectral-domain optical coherence tomography to measure macular thickness preoperatively and 1 week, 1 month, 3 months and 6 months postoperatively.

Mean preoperative macular thickness was 218 µm in both the PK group and the DALK group.

Study results showed that after PK, mean macular thickness increased significantly at 1 week, remained stable at 1 month and returned to normal by 6 months. Mean macular thickness remained stable throughout the 6-month follow-up after DALK.

Mean macular thickness was significantly higher in PK eyes than in DALK eyes at 1 week (P < .001), 1 month (P < .001) and 3 months (P = .005), the authors said.

This nicely executed study showed DALK did not cause postoperative macular thickening, whereas PK did, when performed in keratoconic eyes that had not undergone any other surgical procedures. Transient macular thickening after PK correlated with reduced corrected distance acuity and resolved by the 6-month exam. The study findings are consistent with the fact that intraocular manipulation is minimized with DALK. By retaining host corneal endothelium, DALK also reduces the risk of immunologic graft rejection, and recent studies have shown that DALK results in favorable long-term endothelial cell survival and graft survival. This study shows that DALK can provide short-term, as well as long-term, benefits for patients.

– Marianne O. Price, PhD
Executive Director, Cornea Research Foundation of America, Indianapolis
Disclosure: Dr. Price has no relevant financial disclosures