Impact of Surgical Wound Size and Ocular Structure on Surgically Induced Astigmatism (SIA) after Cataract Surgery
Date Issued
2011
Date
2011
Author(s)
Chen, Yao-Lin
Abstract
Astigmatism is an optical defect in which vision is blurred due to the inability of the optics of the eye to focus a point object into a sharp focused image on the retina. Astigmatism correcting intraocular lens is an advanced technology product capable of correcting pre-existing corneal astigmatism, which increased postoperative visual quality and patient satisfaction in recent years. However, corneal incision in cataract surgery may induce certain amount of corneal astigmatism after surgery. The purpose of this study was to find the factors contributing to surgically induced corneal astigmatism. This retrospective study included 842 eyes acquired between 2004 and 2011 from Far Eastern Memorial Hospital following 2.2mm (cartridge D, Monarch III, N=248), 2.75mm (cartridge C, Monarch II, N=357; cartridge B, Monarch II, N=116), and 3.2mm (folding forceps, no injector, N=121) sized superior limbal incision phacoemulsification. The eyes were divided into four groups according to the corneal incision size and the cartridge used for intraocular lens insertion, namely 2.2mm+MIIID, 2.75mm+MIIB, 2.75mm+MIIC, 3.2mm+no injector. The patients averaged were 70±11, 68±11, 66±12, 69±10 years old. Intraocular pressure (IOP) was measured by Topcon CT80 pneumotonometer and corneal curvatures were measured by Topcon KR 8900 auto-refractor for all eyes. Preoperative axial length (AxL) and anterior chamber depth (ACD) were measured with Zeiss IOL Master in 2.2mm (cartridge D) and 2.75mm (cartridge C) groups. Postoperative corneal curvatures and IOP were measured at 1 day, 1 week, 1 month, and 3 months following surgery. All eyes underwent uneventful three planes coaxial micro incision cataract surgery (MICS) at superior limbus. The amount of the surgically induced astigmatism (SIA) was calculated by Alpin’s vector analysis method. Difference in SIA between various wound sizes was explored. Correlations between preoperative astigmatism, corneal curvatures, ACD, AxL, IOP, Age and SIA were analyzed for various wound sizes. In 2.2mm+MIIID group, the SIA was significantly smaller than those in 2.75mm+MIIC, 2.75mm+MIIB, and 3.2mm+no injector groups one week postoperatively. The SIA were 0.56±0.40 diopter (D), 0.71±0.68D, 0.75±0.54D, 0.80±0.63D one week postoperatively, and 0.5±0.45D, 0.58±0.55D, 0.52±0.41D, 0.54±0.33D three months postoperatively. 2.2mm+MIIID group had advantage in earlier stability of SIA and IOP after surgery. In addition to wound size, higher preoperative corneal astigmatism, older age, shallower ACD contributed to larger SIA for 2.2mm+MIIID and 2.75mm+MIIC groups. However, shorter AxL and lower IOP induced larger SIA in 2.75mm group, but not in 2.2 mm group. Therefore, decreasing limbal wound size and considering factors other than corneal astigmatism in predicting SIA could contribute to optimize refractive lens surgery.
Subjects
Surgically Induced Astigmatism(SIA)
diopter(D)
intraocular pressure(IOP)
anterior chamber depth(ACD)
axial length(AxL)
limbus
Type
thesis
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