Epithelial And Stromal Remodeling After Myopic Photorefractive Keratectomy. A Comprehensive Study.
Published 2023 - 41st Congress of the ESCRS
Reference: PO1034 | Type: Free paper | DOI: 10.82333/2qz7-5823
Authors: Benjamin Memmi* 1 , Juliette Knoeri 2 , Loïc Leveziel 1 , Nacim Bouheraoua 1 , Vincent Borderie 1
1CHNO 1520,Paris,France, 2Ophtalmology,CHNO 1520,Paris,France
Purpose
To describe corneal epithelial and stromal remodeling after myopic photorefractive keratectomy (PRK) as well as interactions between the cornea and the WaveLight® EX500 excimer laser and their influencing factors.
Setting
Tertiary university hospital (Hôpital National des 15-20, Paris, France).
Methods
164 myopic PRK performed from January 2019 to December 2022 were retrospectively analyzed. Preoperative, 1, 3, and 6-month visual acuity, specular corneal topography (SimK, mean simulated keratometry), and spectral-domain optical coherence tomography (CET, central epithelial thickness; CST, central stromal thickness) data were recorded. Data are shown as average values and 10°/90°-percentiles.
Results
The mean spherical equivalent was -3.27D (-6.25D, -1.25D) preoperatively and -0.17D (-0.50D, +0.50D) at M6. Compared with the preoperative values, CET decreased by 4.5µm at M1 and increased by 2.0µm at M3, and 3.8µm at M6 (p<0.00001). CST decreased by 62.5µm at M1 (p<0.00001), then remained stable. The measured ablation depth exceeded the laser-estimated ablation depth by 8.5µm (p<0.00001). SimK decreased by 3.0 D at M1 (p<0.00001), remained stable between M1 and M3 and increased by 0.1D from M3 to M6 (p =0.009). The difference between measured and programmed ablation depth showed no significant association with mitomycin use, pachymetry, keratometry, epithelial debridement technique (mechanical versus alcohol), and optic zone size.
Conclusions
Post-PRK corneal remodeling follows a well-established sequence over time. The corneal epithelium thickness decreases during the first postoperative month and then increases progressively above the preoperative values. Mid-term correction regression is associated with central epithelial thickening. Whereas stromal thickness remains stable after treatment, the WaveLight® EX500 laser treatment results in a significantly deeper ablation depth than expected in some patients. Factors influencing the laser-cornea interaction remain to be identified in further studies.