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LRIs reduce astigmatism with neutral effect on corneal aberrations
Limbal relaxing incisions performed after cataract surgery and IOL implantation reduced corneal astigmatism and had a negligible impact on corneal aberrations, a study found.
The retrospective study included 45 eyes of 36 patients that underwent coaxial micro-incision cataract surgery. Mean patient age was 63 years.
Single limbal relaxing incisions (LRIs) were performed on 23 eyes of 17 patients; 22 eyes of 19 patients did not undergo LRIs.
LRIs were performed on the steepest meridian of corneal topography. The DONO-Donnenfeld nomogram was used to determine degrees of arc.
An AcrySof SN60WF IOL (Alcon) was implanted in all eyes.
Corneal topography and wavefront analysis over a 6-mm pupil were performed preoperatively and at 1 month postoperatively. The Alpins vectorial method was used to analyze target induced astigmatism vector, surgically induced astigmatism vector, difference vector, magnitude of error, flattening effect and torque.
Both groups had similar mean preoperative astigmatism and root mean square of individual higher order aberrations (HOAs).
Mean topographic astigmatism decreased from 1.60 D preoperatively to 0.87 D at 1 month postoperatively in the LRI group, a statistically significant difference (P < .0001), and from 1.30 D preoperatively to 1.23 D at 1 month postoperatively in the control group, which was not a statistically significant difference.
Mean surgically induced astigmatism was 1.29 D, or 0.04 D lower than mean target induced astigmatism in the LRI group.
Corneal higher order aberrations changed insignificantly in both groups. However, quatrefoil aberration increased significantly in the LRI group, from 0.04 m to 0.13 m (P = .01), but changed insignificantly in the control group. – by Matt Hasson
Disclosure: The study authors report no relevant financial disclosures.
Perspective
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This paper is interesting because it shows how properly performed limbal relaxing incisions are effective in correcting moderate amounts of astigmatism during cataract surgery without changing significantly the optical quality of the cornea.
This paper points out how through the use of an on-axis incision, appropriately selected nomogram, being conservative in the selection of patients, especially the amount of astigmatism to be corrected, and, conversely, the aggressiveness of the surgery, these manual incisions can be an excellent alternative to toric lenses for clear correction of astigmatism, especially in lower ametropia. The role of limbal relaxing incisions in low astigmatism, up to 1.5 D to 2D, is what is established today as an alternative to toric lenses in which the variability is largely due to the role of the posterior corneal surface and the difficulty in calculating the toricity.
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Eliwa TF, et al. J Refract Surg. 2016;doi:10.3928/1081597X-20160121-02.