Management of Astigmatism in Cataract

Abstract

With the recent advances in the instrumentation and intraocular lens (IOL) technology, cataract surgery has, over the past few years, become quite akin to refractive surgery allowing greater control over the patients’ refractive and visual outcome. Now the patients expect perfect vision after cataract surgery and surgeons strive hard to deliver the same. In this respect residual astigmatism after cataract surgery is viewed as an undesirable outcome both by the patients and surgeons. In a general cataract population, approximately 10% of patients have astigmatism with greater than 2 D of cylinder, 20% have between 1 and 2 D, and 70% have less than 1 D.1-4 Therefore one may consider treating pre-existing astigmatism in about one out of every three patients. The aim would be to leave the patient with a refractive outcome, for both sphere and cylinder, of 0.50 D or less. However, some surgeons advocate a litt le less aggressive approach to the reduction of residual cylinder as a litt le astigmatism could, in fact, improve uncorrected near vision. Traditionally it has been perceived that residual myopic against the rule cylinder may improve uncorrected near vision.5 In a study conducted recently at our centre, it was seen that myopic astigmatism, up to 1D, in any axis, helps to partially restore uncorrected near visual acuity to some extent but with a proportional loss of distance acuity in pseudophakic eyes with monofocal IOL implant. However, uncorrected myopic astigmatism more than 1 D results in a large loss of distance acuity at no additional benefi t to near acuity. Also, uncorrected hyperopic astigmatism, in any axis, results in deterioration of both distance and near acuities of pseudophakic eyes.6 So a myopic astigmatism less than 1.0 D may be considered benefi cial for near vision by some surgeons, but of doubtful value beyond that. Various approaches have been advocated for tackling preexisting astigmatism in patients having cataract surgery. These include on-axis corneal incision (OCI), limbal relaxing incisions (LRI), paired opposite clear corneal incisions (OCCI), Toric IOLs and fi nally Over the past few years, cataract surgery has, become quite akin to refrac ve surgery allowing greater control over the pa ents’ refrac ve and visual outcome. Now the pa ents expect perfect vision a er the cataract surgery and surgeons strive hard to deliver the same. In this respect a residual as gma sm a er the cataract surgery is viewed as an undesirable outcome both by the pa ents and surgeons. Various approaches have been advocated for tackling the pre-exis ng as gma sm in pa ents having cataract surgery. These include on-axis corneal incision (OCI), limbal relaxing incisions (LRI), paired opposite clear corneal incisions (OCCI), Toric IOLs and fi nally biop cs, where one exploits the advanced technology and exquisite accuracy of excimer laser. A number of popular nomograms are currently available for making accurate correc on in the as gma sm during cataract surgery among which, the nomograms by Nichamin and Donnenfeld are more popular for LRIs and commonly used. The online availability of these nomograms as well as that of Toric IOLs calculators have made the pre-op planning for the as gma sm correc ons much easier than before. Based on the eff ec ve results of all these techniques, one can consider the simple stepladder approach to guide as gma sm management at the me of cataract management. A surgeon may become more comfortable with one par cular technique as compared to another and should, therefore, choose an approach which works best in his or her hands. Recent Advances