Management of pellucid marginal degeneration (PMD) is a subject of ongoing research in the field of corneal ectasia. There is no universally accepted method for managing these patients, especially subjects who cannot wear any type of contact lens. In the current pilot study we introduce a new surgical method for management of high irregular astigmatism due to PMD.

In this prospective study, we implanted allograft-based intrastromal corneal ring segments (AG-ICRS) in four eyes of 3 patients with PMD as a new surgical procedure. A femtosecond laser-assisted stromal canal 4 mm in width was created in the 5.5 to 9.5 mm corneal zone. An AG-ICRS was implanted in the canals. CTR assisted technique was used for implantation (included Video). Dimensions of the implanted AG-ICRS were ring shaped with width of 2 mm and arc length of 160,180 and 240 degree in three eyes and crescent shaped with maximum width and thickness of 3mm and 350 micron respectively, and arc length of 180 degree in one eye. The arc lengths, width, thickness and shape were determined based on the power and area of inferior steepening.

Uncorrected visual acuity and best-corrected visual acuity was improved 6 months after surgery in all eyes. The steep areas were displaced superiorly and the amount of irregular astigmatism was reduced on topography (Figure 1). Implanted AB-ICRSs were clear and stable on the day after implantation and thereafter on all examinations during the follow up period. No significant side effect or complication was observed during the six month follow up period.

AB-ICRS is a safe, effective and inexpensive method for management of PMD, with advantages of customized shape (ring segment, crescent shaped), width and arch length. 
Longer follow up and more cases are needed to confirm our findings.