Refractive astigmatism following toric intraocular lens implantation without consideration of posterior corneal astigmatism

Session Details

Session Title: Toric IOL Calculations & Alignment

Session Date/Time: Sunday 23/09/2018 | 08:00-10:00

Paper Time: 08:58

Venue: Room A5

First Author: : K.Teeluck UK

Co Author(s): :    H. Oliphant   M. Nanavaty                 

Abstract Details

Purpose:

To determine the natural course of refractive astigmatism (RA) following toric intraocular lens (IOL) insertion without consideration of posterior corneal astigmatism for patients with keratometric astigmatism (KA) between 0.75D and 2.5D.

Setting:

Brighton and Sussex University Hospitals NHS Trust, Brighton, UK.

Methods:

34 patients with keratometric astigmatism (KA) between 0.75D and 2.5D underwent toric IOL implantation (Rayner T-flex, Rayner UK) by a single surgeon. Preoperative assessment included Scheimpflug (Pentacam, Oculus, Germany) imaging and KA was classified based on the steep meridian as against-the-rule (ATR) (180 +/- 15 degrees), with-the-rule (WTR) (90 +/- 15 degrees), and oblique (OB) (45/135 +/- 30 degrees). Toric IOL power and axis was calculated using RayTrace premium IOL calculator (https://www.raytrace.rayner.com/), which did not consider posterior corneal astigmatism. The refractive astigmatism (RA) was assessed at 12 months postoperatively and was also classified as ATR, WTR and OB.

Results:

Preoperatively KA was WTR, ATR and OB in 53% (18 eyes), 32% (11 eyes) and 15% (5 eyes) of the eyes. In the eyes with WTR KA preoperatively, 72% had no residual RA and 28% become ATR RA postoperatively. Of the 11 eyes with ATR KA preoperatively, 55% had no residual RA and 45% had remained ATR with RA postoperatively. Of the 5 eyes that had OB KA preoperatively, 20% had no residual RA, 20% had become WTR with RA, and 40% of eyes changed to ATR with RA postoperatively.

Conclusions:

When posterior corneal astigmatism is not considered in the toric IOL calculation formula, postoperative refractive emmetropia is achieved in approximately 2/3rd , ½ and 1/5th of eyes with preoperatively WTR, ATR and OB KA respectively. Around 1/4th of eyes with WTR KA preoperatively is overcorrected to ATR RA whereas ½ of ATR remains undercorrected at 12 months. The majority of eyes with preoperative OB KA are under-corrected with WTR or ATR RA postoperatively. This study suggests the importance of using modern toric IOL calculation formulas, which takes into account the posterior corneal astigmatism

Financial Disclosure:

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