Surgical Options for Correcting Astigmatism in Cataract Patients
A recent study of 4,540 eyes of 2,415 patients showed that corneal astigmatism was present in the majority of patients undergoing cataract surgery, with at least 1.50 D measured in 22.2% of study eyes1. Approximately 38% of eyes undergoing cataract surgery have at least 1.00 D of preexisting corneal astigmatism, and 72% of patients have 0.50 D or more. For good uncorrected distance vision, we surgeons must achieve a refractive result of less than 0.75 D of astigmatism. In truth, we want to get that amount as close to zero as possible.
Studies have shown that astigmatism of as little as 0.50 D can reduce visual acuity by 1 line and that its impact on dynamic, functional visual acuity and low-contrast acuity is even greater. Our goal is to reduce or eliminate their need for bifocals or readers after cataract surgery and Heart of Texas Eye Institute offers an array of surgical options.
For patients that have less than 1.25 diopters of corneal astigmatism, a LRI is usually the best option. The incision is along the steep axis of astigmatism, with its depth and length determined by the amount of astigmatism to be treated; a longer (up to 90 degrees) and deeper cut, closest to visual axis, leads to greater dioptric flattening. The use of manual limbal relaxing incisions (LRIs), although moderately effective, has been an art form with inherent variability in its predictability. Femtosecond or laser assisted LRIs have greatly increased precision by creating reproducible incisions at the desired optical zone, depth and length. This technology has made astigmatism correction using the LRI method more precise and more predictable.
For patients that have greater than 1.25 diopters of astigmatism, we use a toric IOL. The toric IOLs we use range from 1.25 D to 6 D. Toric IOLs are fantastic and accurate. With less than 3 diopters of corneal cylinder approximately 98% of patients are spectacle independent.
Between 3-6 diopters about 92% are spectacle independent. however, for patients willing to reduce their need for reading glasses, the new Symfony Toric Multifocal has been a warm and welcome solution (available up to 3.00 diopters). This lens allows patients to do most things, most of the time, without the need for glasses. It also gives patients an extended range of focus from far distance up to about 12 inches, which is nice for the patient to not have to hold objects at an exact distance in order see clearly.
The rewards of correcting low or high cylinder in the cornea are well worth a little extra effort.
Postoperatively, these patients are some of the happiest in my practice.
1 Ferrer-Blasco T, Montés-Micó R, Peixoto-de-Matos SC, et al. Prevalence of corneal astigmatism before
cataract surgery. J Cataract Refract Surg. 2009;35:70-75.
Hill W. Expected effects of surgically induced astigmatism on AcrySof toric intraocular lens results. J
Cataract Refract Surg. 2008;34:364-367.
Abbey A, Ide T, Kymionis GD, Yoo SH. Femtosecond laser-assisted astigmatic keratotomy in naturally
occurring high astigmatism. Br J Ophthalmol. 2009;93:1566-1569.
Donnenfeld ED Femtosecond laser arcuate incision astigmatism correction in cataract surgery. Presented
at: XXX Congress of the ESCRS ; September 8-12, 2012; Milan, Italy.