Measurement and clinical significant of posterior corneal astigmatism / 眼科新进展

Corneal astigmatism includes anterior astigmatism (AA) and posterior astigmatism (PA).According to the hterature,85.0％-96.1％ PA ranging from-0.01 to-1.10 D refers to astigmatism against the rule.With the age increasing,PA shows a significant trend from astigmatism against the rule to with the rule,while AA shows toward against-the-rule astigmatism.Therefore,PA often leads to partially decrease of total astigmatism (TA) in young adults,but the increase of TA in aged elderly.Clinically,ignorance of PA will lead to a false estimate of TA,thereby affecting visual quality after refractive cataract surgery.And this article aims to introduce the measurement of PA and its clinical significance for providing the reference in clinical practices.

Surgically Induced Posterior Corneal Astigmatism in 2.2 mm Microcoaxial Cataract Surgery Versus 2.85 mm Coaxial Conventional Cataract Surgery

PURPOSE: To compare the surgically induced posterior astigmatism of microcoaxial cataract surgery using a 2.2 mm incision and conventional cataract surgery using a 2.85 mm incision. METHODS: This study included 56 eyes that underwent phacoemulsification and intraocular lens insertion. Subjects were divided into 2 groups: 26 eyes receiving a microcoaxial cataract surgery using a 2.2 mm incision (MCCS group) and 30 eyes receiving a conventional cataract surgery using a 2.85 mm incision (CCS group). Anterior, posterior and total corneal astigmatism was measured. The surgically induced anterior astigmatism, surgically induced posterior astigmatism and surgically induced total astigmatism were compared between MCCS and CCS groups. Corneal astigmatism was measured using a Pentacam(R) device (Oculus, Wetzlar, Germany), uncorrected visual acuity, best corrected visual acuity and corneal aberrations of front and rear side was measured preoperatively and at 1 day, 1 month and 2 months postoperatively. RESULTS: There was no difference in surgically induced posterior astigmatism between CCS and MCCS groups, however, surgically induced anterior astigmatism and surgically induced total astigmatism were significantly lower in the MCCS group than in the CCS group (p = 0.005 and, p = 0.036, respectively). There was a significant positive linear correlation between surgically induced posterior astigmatism and surgically induced total astigmatism in the CCS group (p = 0.01, r = 0.563). There was also a significant positive linear correlation between surgically induced anterior astigmatism and surgically induced total astigmatism in both CCS and MCCS groups (CCS group: p = 0.00, r = 0.855; MCCS group: p = 0.039, r = 0.407). CONCLUSIONS: There was no significant difference in the surgically induced posterior astigmatism between the MCCS and CCS groups. However, surgically induced posterior astigmatism significantly affected surgically induced total astigmatism in the CCS group but not in the MCCS group. Considering both anterior and posterior astigmatism of the cornea, microcoaxial cataract surgery using a 2.2 mm incision affects surgically induced total astigmatism less than conventional cataract surgery.