Toric IOLs Correct Astigmatism Similar to Spherical Lenses Plus Refractive Procedure

Relatively a third of those undergoing phacoemulsification and intraocular lens (IOL) implantation are affected by astigmatism and have the option to choose toric lenses or spherical IOLs combined with later corneal surface treatment. Patients often look to their physician for advice on advantages and disadvantages of each alternative, and this common procedure may be evolving into “refractive cataract surgery.”

An investigation published in BMC Ophthalmology compares refractive results for 60 eyes of 49 patients with astigmatism undergoing 1 of 3 procedures: spherical IOL implantation only, toric IOL, or spherical IOL followed in 3 months by wavefront-guided photorefractive keratectomy (PRK). Each group comprised 20 eyes — with no significant differences in mean age among cohorts (P =.06), as well as baseline cylinder calculated with biometry (P =.38).

Postoperative results indicated a small but significant reduction in mean astigmatism for the first group with spherical IOL only; from baseline 2.7±0.84 to 2.15±0.6 (P =.031). The second cohort which received toric IOLs experienced a significant change in refractive astigmatism; from 3.4±1.1 to 0.53±0.32 after surgery (P <.001). Similarly, the third group followed up at 3 months after PRK also had a significant improvement; from pre-op 3.0±0.8 to refractive astigmatism of 0.4±0.15 (P <.001).

The analysis notes that astigmatism can be measured more precisely after primary cataract removal, although laser correction of residual refractive errors involves a 2-step technique that includes added risks of a second procedure, such as corneal ectasia, a longer recovery time, and higher costs. Alternately, 1-step phacoemulsification with toric IOLs requires precise pre-op IOL and cylinder calculations, and risk for lens rotation after implantation that may have a canceling effect for the lens’ cylinder correction or need repositioning.

In the present study, 20% of eyes in the toric IOL set developed enough rotation to necessitate realignment, and 25% of eyes in the group undergoing PRK experienced dry eye that called for long-lasting lubricants. 

Previous studies have demonstrated that toric IOLs can prompt spectacle independence approximately 60% of the time, up to 97% bilaterally after fellow-eye surgery, and better uncorrected distance visual acuity (UDVA) compared with control cohorts — 60% to 80% achieving UDVA of 20/25 or better. In prior research that explores strategies to manage residual refractive error, such as IOL exchange, refractive surgery, and other techniques, laser produced better results with less surgical risk. PRK may lead to post-op pain and haze, although the current analysis reported no cases of haze formation.

The investigation was conducted at university hospitals in Egypt during 2017 and 2018. A limitation of the design was a short follow-up, precluding an analysis of treatment stability. The study authors recommend preoperative measurement of “very accurate k readings,” as well as early postoperative monitoring for centration. Researchers speculate that rotation can be minimized by “implantation of IOL on irrigating fluids not viscoelastic materials, meticulous removal of any viscoelastic materials, and reexamine IOL alignment after removal of the eye speculum.”

Reference

El-Shehawy A, El-Massry A, El-Shorbagy MS, et al. Correction of pre-existing astigmatism with phacoemulsification using toric intraocular lens versus spherical intraocular lens and wave front guided surface ablation. BMC Ophthalmol. Published online March 12, 2022. doi:10.1186/s12886-022-02347-5