Purchase this article with an account.
Sanjeev Kasthurirangan, Stan Bentow; Refractive and Corneal Astigmatism in Patients with Monofocal Intraocular Lens. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):2967.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Toric intraocular lenses (IOLs) have led to a renewed interest in understanding posterior corneal astigmatism and its inclusion in the calculation of toric IOL power for implantation. In this study, refractive astigmatism and anterior corneal astigmatism were compared in patients with a monofocal IOL to calculate the magnitude of posterior corneal astigmatism and surgically induced corneal astigmatism.
Corneal astigmatism (CA) and refractive astigmatism (RA) data from a previous multi-center clinical study in which subjects were implanted with a non-toric monofocal IOL or a toric IOL were analyzed. All corneal incisions were restricted to temporal 180 ± 15° in the study. Notably, in the non-toric IOL group, subjects had<br /> preoperative anterior CA of 0.75D to 1.50D. In the non-toric IOL group, the difference between postoperative anterior CA and postoperative RA can be attributed to the posterior CA, as the IOL does not have any cylindrical power. Main outcome measures were i) magnitude of posterior corneal astigmatism calculated as postoperative RA minus postoperative CA in the non-toric group (n = 208 eyes) and ii) surgically induced astigmatism (SIA), calculated as postoperative minus preoperative CA of all eyes (n = 535 eyes).
The non-toric group had mean ± SD preoperative CA of 0.98 ± 0.32 D, postoperative CA of 0.95 ± 0.45D and postoperative RA of 0.76 ± 0.53 D. Postoperative RA magnitude was statistically significantly different (One-way ANOVA, p < 0.05) for postoperative CA, grouped into “with-the-rule” (vertical steep meridians >60°-120°, RA: 0.41 ± 0.33 D), “against-the-rule” (horizontal steep meridians 0°-30° and >150°-180°; RA: 0.98 ± 0.53 D) and “oblique” (steep meridians >30°-60° and >120°-150°; RA: 0.68 ± 0.36 D). The mean posterior CA vector was 0.28D at 179.09°. The J0 vector component of SIA was statistically significantly different (One way ANOVA, p < 0.05) for preoperative CA into “with-the-rule” (SIA J0: 0.00 ± 0.57 D), “against-the-rule” (SIA J0: -0.33 ± 0.60 D) and “oblique” (SIA J0: -0.17 ± 0.55 D). The mean SIA vector was 0.19 D at 90.35°.
Generally, “against-the-rule” posterior corneal astigmatism resulted in reduced total refractive astigmatism when anterior corneal astigmatism was “with-the-rule.” Induced SIA was greater when the cataract incision was located along the steep meridian of corneal astigmatism.
This PDF is available to Subscribers Only