The Effect Of Diurnal Fluctuations On Visual And Refractive Outcomes In Myopic Prk Surgery
Published 2026 - 44th Congress of the ESCRS
Reference: POREF237 | Type: Free paper | DOI: 10.82333/3v4c-3x49
Authors: Dr Adir Sommer* 1 , Dr Dror Ben Ephraim Noyman 1 , Dr Waseem Nasser 1 , Dr Margarita Safir 2 , Dr Avinoam Shye 1 , Mr Gur Munzer 3 , Mr Tzahi Sela 3 , Mr Shmuel Baruch 3 , A/Prof. Igor Kaiserman 4 , A/Prof. Michael Mimouni 1
1Rambam Health Care Campus,Haifa,Israel, 2Rabin Medical Center,Petah Tikva,Israel, 3Care-Vision Laser Center,Tel-Aviv,Israel, 4Barzilai Medical Center,Ashkelon,Israel
Purpose
Diurnal variations in corneal hydration and thickness may alter excimer laser ablation efficiency through differential water-mediated photon absorption. This study evaluated whether diurnal surgical timing affects visual outcomes and refractive predictability following myopic Photorefractive Keratectomy (PRK) surgery.
Setting
Retrospective comparative study, Care Vision Laser Center, Tel Aviv, Israel.
Methods
This retrospective study included 18,512 eyes of 12,359 patients who underwent myopic PRK (≥0.25D), stratified by surgical timing: Morning (07:30-09:30; N=9,255) and Afternoon (15:30-17:30; N=9,257). Pre-, intra-, and post-operative parameters were compared between the groups. Outcomes assessed included uncorrected and best-corrected visual acuity (UCVA, BCVA), spherical equivalent (SEQ), predictability (±0.5 D and ±1.0 D of target), and safety and efficacy indices. A multivariate analysis of covariance (MANCOVA) was performed, adjusting for the year of surgery.
Results
The two groups were comparable in all preoperative and intraoperative parameters (all P>0.05). Mean follow-up was ~147 days (P=0.555). No significant differences were found in postoperative SEQ (0.02±0.41 D vs. 0.02±0.41 D; P=0.903), UCVA (0.94 vs. 0.95; P=0.108), or refractive predictability within ±0.50 D (89.5% vs. 90.2%; P=0.56) and ±1.00 D (96.9% vs. 97.3%; P=0.559). Efficacy and safety indices were similar (1.02±0.14 vs. 1.02±0.14; P=0.855 and 1.03±0.12 vs. 1.04±0.12; P=0.802, respectively). MANCOVA confirmed time of day had no significant effect. A marginal difference in BCVA (0.95 vs. 0.96; P=0.046) favouring afternoon surgery was clinically negligible (mean difference 0.005 decimal lines; 95% CI: -0.009 to 0.000).
Conclusions
In this large-scale study, the time of day at which PRK was performed had no clinically or statistically meaningful effect on visual outcomes, refractive predictability, efficacy, or safety. These findings suggest that concerns regarding diurnal effects on visual and refractive outcomes do not translate into detectable outcome differences during standard clinical operating hours. PRK scheduling may be guided by logistical considerations without concern for time-of-day–related variability in surgical results.