Frown Incision: A Means To Minimize Astigmatism

Minimize Astigmatism

Abstract

Associate Professor, Department of Ophthalmology, Sri Aurobindo Institute of Medical Sciences, Indore 453111, India
Abstract : Introduction: Modern day cataract surgery is aimed at giving optimal catarefractive outcome . This study was inspired by a chance finding of high astigmatic reading on performing retinoscopy three weeks after surgery in a female who underwent manual small incision cataract surgery. Aim of study: To study effect of scleral tunnel incision at different locations on pre-existing astigmatism ,and to calculate surgically induced astigmatism there from . Design: The scleral tunnel incision is known to undergo changes upto six weeks after cataract surgery .If pre operative value and post operative values at the end of six weeks are known ,SIA can be calculated. All patients operated free of cost for cataract are implanted an all PMMA non foldable 6.0mm intraocular lens hence we chose a six mm frown incision. From our study we aim to give cut off values of native astigmatism to chose incision site in order to provide least residual astigmatism, since this group of patients being non affording cannot undergo any additional surgical procedure to get astigmatism corrected . The higher order post cataract surgery residual error degrades quality of image ,hence accentuation of native error by SICS is non justifiable . Rather,our aim should be to regress existing error by 50% -75%. Method: In 150 eyes undergoing cataract surgery in the department of Ophthalmology, Aurobindo Institute Of Medical Sciences under eye camp, the preoperative keratometric values in vertical and horizontal axis were noted .At the end of six weeks after cataract surgery performed by 6mm incision at superior, superotemporal and absolute temporal locations , keratometry readings were noted again along the principle meridia .SIA was calculated from these two readings. At the end of six weeks keratometry and retinoscopy weres done. Result: From the study it was concluded that location of incision in the eye has a bearing on existing astigmatic error . A regression (or accentuation) in the existing error is dependent on the incision site and the magnitude of pre-existant error. With superior and absolute temporal scleral tunnel incision , SIA average was 0.77 Dioptres while with BENT( between nine and twelve) clock hours it was lesser (0.68 Dioptres) Except in thirteen eyes who accepted cylindrical lens in oblique meridia, all others accepted glasses in primary meridia. Conclusion: For upto 1 D astigmatism, ATR or WTR, placement of incision on steeper axis should be the choice. For WTR, of any degree, a superior location should be the choice. For ATR amounting to 1.25D, a superotemporal incision offers best results. For higher ATR absolute temporal location should be the choice if regression in astigmatism is desired.