The dynamics of the astigmatic cornea: total astigmatism of the cornea, resulting from vector analysis of corneal front and back surfaces, before and after routine cataract surgery

Session Details

Session Title: Toric IOL Calculations & Alignment

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

Paper Time: 09:04

Venue: Room A5

First Author: : L.Tutchenko UKRAINE

Co Author(s): :    S. Patel   O. Voytsekhivskyy   O. Horak   M. Skovron           

Abstract Details

Purpose:

To determine if the total astigmatism of the cornea was affected by routine uncomplicated phacoemulsification in cases of clear corneas free of gross surface irregularities.

Setting:

Department of Ophthalmology, Shupyk National Medical Academy of Postgraduate Education, Kyiv, Ukraine Kyiv City Clinical Ophthalmological Hospital “Eye Microsurgery Center”, Ukraine

Methods:

Astigmatism at both corneal surfaces, within the central 3 and 5mm optical zones, was evaluated using Orbscan II (Bausch & Lomb) prior to, and at 2 months after, surgery. The data were subjected to vector analysis to calculate total astigmatism of the cornea before and after surgery in each case. Surgery was standard routine phacoemulsification under topical anaesthesia (2.2 mm incision at 12 o’clock), subconjunctival injection of dexamethasone and parabulbar injection of betamethasone. Postop topical levofloxacin, dexamethason, indomethacin, dexpanthenol, trehalose and hyaluronic acid. Only one type of nontoric IOL was implanted in all cases.

Results:

Reporting the chief findings. In plus cylinder format over the central 5mm optical zone, 1) the total astigmatism of the cornea (mean[±s.d] power followed by axis) at pre- and postop respectively was 2.37DC (±2.04) 93.3° (±46.3) and 3.23DC (±2.10) 97.5° (±36.1). The change power was significant (p=0.025,n=37). 2) There was a significant linear relationship between the change in total astigmatism (y) and total astigmatism at preop where, y=0.783x-2.721 (r=0.613,n=37,p<0.001). 3) Astigmatic power at front surface remained stable. The back surface changed significantly (p=0.014) from 2.28DC(±1.64) to 3.10DC (±2.01).

Conclusions:

The total astigmatism of the cornea is significantly affected by routine phacoemulsification. The change occurs mainly at the back surface of the cornea. In individual cases, refractive surprises may result from unexpected changes at the back surface of the cornea. The overall change in the total astigmatic power could result from a variety of sources including orthogonal variations in corneal hydration.

Financial Disclosure:

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