The outcomes of first-generation (visumax 500) and second-generation (Visumax 800) keratorefractive lenticule extraction surgeries for astigmatism

To evaluate the efficiency, predictability, and residual astigmatism between first- and second-generation keratorefractive lenticule extraction (KLEx) surgeries in a prominent astigmatism population. A retrospective cohort study was conducted, and individuals who underwent first- and second-generation KLEx surgeries were enrolled. A total of 31 and 35 eyes were categorized into first and second KLEx groups, respectively. Visual acuity, refraction, topographic parameters, and surgical indices were recorded. Independent t tests were used to compare the postoperative uncorrected distance visual acuity (UDVA), spherical equivalent (SE), and residual astigmatism between the two groups. The difference in UDVA was not significant three months after KLEx surgery (P = 0.509), and the SEs three months after surgery also presented similar values between the two groups (P = 0.552). The first KLEx group demonstrated greater residual astigmatism than did the second KLEx group throughout the three-month follow-up period (all P < 0.05). The values of surgically induced astigmatism (SIA), difference vector (DV), magnitude of error (ME) and correction index (CoI) were significantly better in the second KLEx group via vector analysis (all P < 0.05). Old age, high steep keratometry (K), high topographic cylinder, large angle kappa, and a small optic zone were correlated with greater residual astigmatism in the first KLEx group (all P < 0.05), whereas only a small optic zone was significantly correlated with greater residual astigmatism in the second KLEx group (P = 0.047). The second-generation KLEx is correlated with a lower risk of residual astigmatism.