Astigmatism management at the time of cataract surgery

Abstract

Patients expect their vision to improve after cataract surgery and, increasingly, they expect to be free of the encumbrance of glasses and contact lenses. These expectations are driven by technological advancements throughout the ophthalmic industry and the experiences of family and friends. To meet or exceed patient expectations, cataract surgeons must pay increasing attention to the management of pre-existing corneal astigmatism at the time of cataract surgery. Pre-existing corneal astigmatism is a significant component of preoperative ametropia. To achieve satisfactory postoperative refractive results, it is important to correct pre-existing spherical errors by accurate biometry and intraocular lens (IOL) power calculation, and to manage preoperative corneal cylinder errors by a suitable method. Guided by preoperative corneal topography, patients with varying degrees of corneal astigmatism can be placed into a variety of dioptric categories. These categories dictate a systematic ‘stepladder’ approach to guide the optimum approach to surgical correction. For patients with less than 1 D of corneal astigmatism, the preferred approach is to place the phacoemulsification incision on the steep corneal meridian. For 1–3 D of corneal astigmatism, single or paired peripheral corneal-relaxing incisions may be used. Alternately, for astigmatic errors of 1–4 D, toric IOLs can be implanted. Astigmatism of 4.5–7 D may be addressed using a combined approach of toric IOL implantation and peripheral corneal relaxing incision placement in the steep meridian of corneal cylinder. Moreover, high-powered toric IOLs, currently available in select European and Asian markets and not currently approved by the US FDA, may be implanted in the USA if an ophthalmologist obtains a compassionate use exemption from the FDA and local Institutional Review Board approval. If visually significant refractive errors are present after cataract surgery, surgical management options include piggyback IOL implantation, IOL exchange, toric IOL rotation, photorefractive keratectomy and laser-assisted in situ keratomileusis. Of these options, photorefractive keratectomy and laser-assisted in situ keratomileusis usually provide the most simple solution to manage suboptimal refractive outcomes. This simple stepladder approach to astigmatism management, which is based on preoperative corneal topography, enables cataract surgeons to achieve excellent unaided visual acuity in the absence of vision-limiting ocular comorbidities.