Comparison of surgically induced astigmatism between anterior and total cornea in 2.2 mm steep meridian incision cataract surgery

Abstract

Background This study aimed to compare surgically induced astigmatism (SIA) on the anterior and total cornea during cataract surgery through a 2.2 mm steep meridian incision. Methods The study included 69 left eyes of 69 patients who had undergone cataract surgery. The 69 eyes were classified into three subgroups according to the preoperative steep meridian. Following phacoemulsification, an intraocular lens was inserted into the bag. The keratometric measurements were taken 12 months postoperatively, on the anterior cornea (automated keratometer and anterior keratometry [K] from a rotating Scheimpflug camera) and total cornea (equivalent K reading [EKR] 3.0 mm, EKR 4.5 mm, total corneal refractive power (TCRP) 2.0 mm ring, TCRP 3.0 mm zone, TCRP 4.0 mm zone). The SIA was analyzed for each parameter. Results On the double-angle polar plot, the summated vector mean values of SIA determined by the automated keratometer and Scheimpflug anterior K were 0.28 diopter (axis: 177°) and 0.37 diopter (axis: 175°) in with-the-rule (WTR) astigmatism; 0.03 diopter (axis: 156°) and 0.18 diopter (axis: 177°) in oblique astigmatism; 0.15 diopter (axis: 96°) and 0.17 diopter (axis: 73°) in against-the-rule (ATR) astigmatism. The mean SIAs on the total cornea ranged from 0.31 to 0.42 diopter in WTR astigmatism; from 0.16 to 0.27 diopter in oblique astigmatism; from 0.04 to 0.11 diopter in ATR astigmatism. Mean magnitude SIA ranged from 0.41 to 0.46 diopter on anterior corneal surface and 0.50 to 0.62 diopter on total cornea. J0 and J45 of the posterior cornea showed no significant changes after cataract surgery, and the changes in J0 and J45 did not show any statistical differences between the anterior and total cornea (all p > 0.05). Conclusions There were no differences in the summed vector mean values of SIA between the anterior cornea and the total cornea.

Surgically Induced Astigmatism after Cataract Surgery – A Vector Analysis

“…This is mostly caused by the steepening of the corneal back surface (0.04 dpt), whereas flattening of the corneal front surface is very low (0.01 dpt). In 2021 Yoon et al studied SIA based on measurements made with an automated keratometer and a Scheimpflug tomographer [26]. They found that in their study population including 69 eyes there was a very slight statistically non-significant decrease in the power of the anterior surface (on average -0.02 dpt) and in the power of the posterior surface (on average -0.01 dpt).…”

Evaluation of statistical correction strategies for corneal back surface astigmatism with toric lenses: a vector analysis

“…The toric IOL power was derived based on the “real power” value of the Casia 2 considering the corneal front and back surface based on a thick lens model, and the toric lens markers were aligned to the steep axis of the “real power.” After paralimbal 2.2-mm (astigmatism-neutral) microincision from the temporal side, the anterior chamber was filled with a cohesive ophthalmic viscosurgical device and the creation of a continuous curvilinear capsulorhexis (CCC) was slightly smaller than the IOL optic diameter (approximately 5.25 mm). 8,24–28 After a standard phacoemulsification procedure, the Vivinex tIOL was inserted and aligned with its marker at the steep corneal meridian (CASIA2) and the CCC and both paracenteses were hydrated.…”

“…After paralimbal 2.2-mm (astigmatism-neutral) microincision from the temporal side, the anterior chamber was filled with a cohesive ophthalmic viscosurgical device and the creation of a continuous curvilinear capsulorhexis (CCC) was slightly smaller than the IOL optic diameter (approximately 5.25 mm). 8,[24][25][26][27][28] After a standard phacoemulsification procedure, the Vivinex tIOL was inserted and aligned with its marker at the steep corneal meridian (CASIA2) and the CCC and both paracenteses were hydrated.…”

Efficacy Comparison Between Steep-Meridian Incision and Non-Steep-Meridian Incision in Implantable Collamer Lens Surgery with Low-to-Moderate Astigmatism

“…The steep-meridian corneal relaxing incision (SM–CRI) is made at the steep meridian of the cornea [ 6 ]. The basic principle is that the relaxing incision of the cornea flattens the steep meridian and steepens the flat meridian to reduce corneal astigmatism.…”