Corneal astigmatism is often documented during preoperative biometry measurements in children and adults. In infancy, there is a high prevalence (≥42%) of astigmatism (≥1.00 D).¹,²,³,⁴,⁵,⁶,⁷,⁸,⁹,¹⁰,¹¹,¹²,¹³A reduction in this infantile astigmatism occurs in the first years of life because of a natural decrease in toricity of the cornea and the anterior lens, along with a decrease in the variation of the cornea and lenticular surfaces.¹⁴ Hispanic and African-American children are more likely to have astigmatism than are non-Hispanic white children, and this association remains even after correcting for the presence of spherical equivalent refractive error (myopia or hyperopia).¹⁵ In adults, residual postoperative corneal astigmatism, if uncorrected, has been noted to reduce uncorrected visual acuity and induce symptomatic blur, ghosting of images, and halos.¹⁶ Children with astigmatism >2.00 D in 3-year-olds or >1.50 D in 4-year-olds have been shown to have visual motor integration deficits.¹⁷ Amblyopia treatment seems to be less favorable in patients with either hyperopic or myopic against-the-rule (ATR) astigmatism.¹⁸

To meet parents’ expectations for good visual acuity after cataract surgery and to help amblyopic management, it is important to address both sphere and cylinder errors that may affect final refractive outcomes. Parents want to know how clear the vision will be when glasses are removed, even if it has been explained that the child’s best visual acuity will always be with bifocal glasses. Preoperative assessment for cataract surgery should be followed by comprehensive counseling that focuses on a patient’s individual vision needs. The refractive part of the discussion should include a discussion about the refractive aim for immediately after surgery and also what the refraction is expected to be years later. In a young child, this may include a discussion of far-sighted bifocal glasses after surgery with a gradual reduction in the strength of the glasses as the eye grows. If the child is older than 3 years and has preoperative astigmatism, parents are told that the astigmatism will likely be unchanged after surgery and will be corrected with glasses. For older children, a review of surgical options for reducing astigmatism is becoming more common. These options include astigmatism management with peripheral corneal-relaxing incisions (PCRIs), toric intraocular lens (IOL) (Fig. 30.1), and the possibility of postoperative laser refractive surgery. It is important to estimate the likelihood of less spectacle dependence based on the age that can realistically be achieved with a given surgical option. Videos or computer- based illustrations may be a useful and effective way of explaining the different approaches. Spherical refractive errors are managed by accurate biometry and IOL power calculations. The target refraction should be based on age at surgery and other factors (see Chapter 7). Relying solely on manual keratometry to characterize a patient’s corneal curvature is commonly done during standard biometry for IOL power calculations. However, if the surgeon desires to surgically manage astigmatism, manual keratometry may be insufficient. Significant cylindrical errors may exist inside and outside the central 3.2-mm optical zone measured by keratometry. In addition, meridian changes over the entrance pupil and irregular astigmatism may be missed. Using the IOL Master^® (Carl Zeiss Meditec, CA, USA) for corneal curvature measurements can result in similar mistakes.¹⁹ For these reasons, computerized corneal topography is the current standard of care when astigmatism correction is being considered. Topography accurately measures the global corneal astigmatism, quantifies the nature of the astigmatism (i.e., symmetric bow tie versus asymmetric or irregular astigmatism), and identifies the steep meridian of astigmatism. Patients implanted with monofocal IOLs usually achieve better-uncorrected visual acuity if the spherical error approaches emmetropia and residual manifest astigmatism is less than 1 D. For patients implanted with multifocal IOLs, the postoperative refractive goal is to achieve <0.75 D of residual corneal astigmatism. However, as mentioned above, children have a targeted refraction that depends on age at surgery. Final results are also dependent on the pupil size and the amount of residual spherical error. Overcorrections and large rotations in the axis of residual astigmatism should be avoided.

Astigmatism correction at the time of cataract surgery or in aphakic/pseudophakic eyes of children is still uncommon and is only now beginning to be reported.²⁰,²¹ However, witnessing impressive outcomes in adults, pediatric cataract surgeons have started discussing correction of astigmatism in children. In the following sections of this chapter, we review the literature on astigmatism correction in adult eyes. We anticipate a more conservative approach in the growing eyes of children.