Femtosecond Laser-Assisted Penetrating Keratoplasty With Polymer Devise As A Prevention Of Secondary Ectasia

Published 2025 - 43rd Congress of the ESCRS

Reference: PO589 | Type: Free paper | DOI: 10.82333/2b06-m803

Authors: Ozlem Dikmetas Sandıkcı* ¹ , Selman Bozkır ² , Ceren Ozkorkmaz ¹ , Sibel Kocabeyoğlu ¹

¹Ophthalmology,Hacettepe University,Ankara,Türkiye, ²Computer Engineering,Hacettepe University,Ankara,Türkiye

Purpose

A previously conducted histological study of corneas with confirmed secondary ectasia (SE) after keratoplasty demonstrated that the development of SE originates in the altered peripheral recipient tissue. It is essential to refine the technique of penetrating keratoplasty (PKP) to prevent recurrence.

Setting

The study took place at The S. Fyodorov Eye Microsurgery Federal State Institution including the six-year follow-up.

The study included 25 patients with Advanced Keratoconus (AK). All patients underwent femtosecond laser-assisted penetrating keratoplasty (FS-PKP) with the implantation of a polymer ring (PR) under intraoperative optical coherence tomography (OCT) guidance.

Methods

We developed a new laser control algorithm for creating a personalized cutting pattern to form a tunnel for implanting a 360° PR within the residual stromal tissue of the recipient’s cornea, providing additional structural support. The algorithm considers the recipient(R) cornea thickness at the incision site and the diameter of the implanted PR(7.0-9.0mm) based on the R’s WTW corneal diameter. For donor(D) and R corneal trephination, a “mushroom” pattern was used with a 0.5mm difference in trephination diameter. The cutting depth in the transplant, accounting for corneal swelling, was 100microns greater than that of the R. The laser created a closed tunnel symmetric to the trephination opening, allowing the PR to evenly tension the cornea.

Results

According to OCT data, the polymer ring maintained a stable position at the specified depth, uniformly along its entire length, with an average value of 341.33±7.11 μm. We observed an earlier improvement in visual function, with an increase on the 7th day post-surgery: uncorrected visual acuity (UCVA) was 0.2±0.05 diopters and corrected visual acuity (CVA) was 0.27±0.08 diopters. After suture removal, UCVA increased to 0.5±0.21 diopters and CVA to 0.65±0.29 diopters. The spherical refractive component after suture removal was 1.2±1.3 diopters, assuming that the average axial length (AL) of the patients’ eyes was 24.1±2.6 mm. The cylindrical refractive component after suture removal was 2.6±1.1 diopters. No cases of SE were observed.

Conclusions

The method gives earlier improvement in visual acuity but recommended to myopic eyes due to the shift toward hypermetropia even with the thinnest ring (150 microns). It prevents SE due to its location in the recipient residual stroma (histologic examination is attached). The device material is well studied and safe, no immunologic rejections were found. The method does not involve repeated medical intervention to remove the ring, the patients had no complaints of halo effects, which is due to the lack of location of the ring at optic zone.