Journal of Clinical Medicine · 7 authors, 3 centres
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This retrospective study found that LASIK and PRK temporarily degrade retinal image quality and visual stability in the first month, with PRK showing a more significant early decline. By three months, both procedures restored most optical quality metrics, but objective scatter index (OSI) and vision break-up time (VBUT) remained slightly worse after PRK. These findings help explain early postoperative visual complaints that may not correlate with standard visual acuity tests.
**Background:** Laser vision correction (LVC) for myopia, including LASIK and PRK, commonly causes dry eye symptoms that may reduce visual quality despite good uncorrected visual acuity. Traditional assessments like wavefront aberrometry may overestimate optical quality by neglecting scattering. The double-pass aberrometer objectively measures retinal image quality and tear film dynamics. This study aimed to evaluate early postoperative changes in optical quality and visual stability after LASIK and PRK using double-pass aberrometry.
**Methods:** This retrospective study included 141 right eyes of 141 patients (52 LASIK, 89 PRK) from Shaare Zedek Medical Center, Jerusalem. All had myopia (up to −10 D) or myopic astigmatism. PRK was chosen when expected percentage tissue altered exceeded 40% or patient preference. Assessments were done preoperatively, at 1 month, and at 3 months postoperatively using the HD Analyzer (double-pass aberrometer). Parameters: objective scatter index (OSI; normal 0.46–1.3), modulation transfer function (MTF) cutoff (normal 53.3–31.1 cycles/degree), Strehl ratio (SR; normal ~0.3 for 4 mm pupil), and vision break-up time (VBUT; time for OSI to increase by 0.5 after blink). Statistical analysis used paired t-tests and Pearson correlations.
**Key Results:** At baseline, no significant differences existed between groups. After LASIK, no significant changes in any parameter were observed at 1 or 3 months, though minor deterioration occurred at 1 month. After PRK, all parameters significantly worsened at 1 month (p<0.01 for all). At 3 months, OSI remained elevated (increase of 0.14 ± 0.36, p<0.01) and VBUT remained shortened (decrease of 0.57 ± 2.3 s, p<0.01) versus baseline; MTF and SR recovered. Between 1 and 3 months, all parameters improved significantly in PRK; in LASIK, only VBUT significantly improved (increase of 0.78 ± 1.9 s, p=0.02). At 3 months, no differences existed between LASIK and PRK for any parameter. VBUT was 9.6 ± 1.05 s (LASIK) and 9.1 ± 2.2 s (PRK) at 3 months (p=0.11). No correlations were found between parameter changes and age, ablation depth, or postoperative spherical equivalent. However, moderate negative correlations existed between the magnitude of change at 3 months and preoperative values for all parameters.
**Clinical Implications:** LASIK and PRK both cause temporary optical quality degradation, with PRK showing more early impact. The persistent increase in OSI and shortened VBUT at 3 months after PRK likely reflects ongoing corneal healing, possibly mitigated by mitomycin C. The VBUT reduction directly captures the unstable tear film's effect on functional vision, explaining why patients may report fluctuating vision despite 20/20 acuity. This metric offers objective monitoring of subjective complaints post-LVC. The negative correlation between preoperative optical quality and degradation suggests patients with better baseline quality may notice more transient worsening. Overall, both procedures achieve similar optical quality by 3 months, but PRK requires a longer recovery.