Changes in the Higher Order Ocular Aberrations and Central Corneal Thickness After T-PRK and Fs-LASIK

ABSTRACT Introduction: Refractive surgery procedures, transepithelial photorefractive keratectomy (T-PRK), and femtosecond laser in situ keratomileusis (Fs-LASIK) are regarded as safe and efficacious methods for correcting myopia and myopic astigmatism. These two methods do not have many differences in results when treating spherical myopia while differences exist in the treatment of astigmatism correction. Vector analysis presents a powerful tool to show the real differences between these two methods regarding high ocular aberrations and central corneal thickness of treated eyes. Aim: The aim of the study is to investigate changes in higher order ocular aberrations (HOAs) and central corneal thickness (CCT) following treatment of myopia and myopic astigmatism above -5.00DS and up to -2.00DC after either T-PRK or Fs-LASIK. Methods: Patients (30 eyes per group) underwent T-PRK (group I) or Fs-LASIK (group II) procedure using the Schwind Amaris 750S laser. HOAs (3mm&5mm pupil) and CCT were measured objectively at pre-, 1, 3 & 6 months postop in each case. Results: Key results at 6 months were: i) mean values of trefoil (5mm pupil) were 0.092µm (sd, 0.055, 95% CI 0.072 to 0.112) & 0.126µm (sd, 0.078, 95% CI 0.098 to 0.154) in group I, and 0.088µm (sd, 0.058, 95% CI 0.067 to 0.109) & 0.064µm (sd, 0.034, 95% CI 0.052 to 0.076) in group II (P=0.001 at 6 months) ; ii) Changes in CTT (ΔCTT) and best spherical equivalent correction (ΔBSE) was significant in group II (ΔCCT=-26.55[ΔBSE]- 14.06, R=0.486, P=0.006) but not in group I (p=0.034). Conclusions: After T-PRK trefoil is worse than Fs-LASIK. The predictability of corneal changes is better following Fs-LASIK

Apparent Corneal Ectasia After Bilateral Intrastromal Femtosecond Laser Treatment for Presbyopia

Purpose: To report a case of apparent corneal ectasia after intrastromal femtosecond laser treatment for presbyopia (INTRACOR). Methods: A healthy 56-year-old male with low hyperopia underwent an unremarkable bilateral INTRACOR procedure in March/April 2011. The patient was discharged after follow-up and returned 5 years later. Results: Before discharge, the monocular logarithm of the minimal angle of resolution uncorrected distance visual acuity (UDVA) values were R, 0.0 and L, 0.10. In both eyes near (UNVA) visual acuities were 0.0. There were signs of slight posterior central corneal steepening without loss of corneal stability. Five years postop, monocular UDVA and UNVA values were 0.4 and 0.0, respectively. Ectasia was observed in both eyes, and the centrally placed 5 concentric rings after the INTRACOR procedure were visible under slit-lamp biomicroscopy. Conclusions: There is no clear reason to explain why the patient developed bilateral corneal steepening. It could be that the patient’s corneal stromal fibers gradually weakened over this 5-year period