The influence of corneal asphericity on the refractive outcome of IOL implantation in cataract surgery

Session Details

Session Title: Cataract Surgery Outcomes

Session Date/Time: Tuesday 16/09/2014 | 08:00-10:30

Paper Time: 08:42

Venue: Capital Hall A

First Author: : G.Savini ITALY

Co Author(s): :    K. Hoffer   P. Barboni           

Abstract Details

Purpose:

To investigate the possible influence of corneal asphericity on the refractive outcome of eyes undergoing intraocular lens (IOL) implantation after cataract surgery.

Setting:

Private practice, Bologna, Italy

Methods:

IOL power was calculated by the Haigis, Hoffer Q, Holladay 1 and SRK/T formulas with optimized constants for simulated keratometry (Keratron, Optikon 2000) and axial length measurement by immersion ultrasound biometry. Asphericity (Q-value) was measured at 8mm with a Placido-disc corneal topographer (Keratron), a rotating Scheimpflug camera (Pentacam, Oculus), and a rotating Scheimpflug camera combined to Placido-disc (Sirius, CSO). The relationship between the arithmetical error in refraction prediction (i.e. the difference between the expected refraction and the refraction measured at one month after surgery) and the Q-value was assessed by linear regression.

Results:

The same IOL model (AcrySof SA60AT) was implanted in 115 consecutive eyes of 115 consecutive patients. The regression analysis showed a statistically significant relationship between the error in refraction prediction and the Q-value with all formulas and all devices. Using the Keratron measurements, the p values were <0.001 for the Haigis, Hoffer Q and Holladay 1 formulas, and 0.001 for the SRK/T formula. Using the Pentacam measurements, the p values were 0.012 for the Haigis formula, and 0.001 for the Hoffer Q, Holladay 1 and SRK/T formulas. Using the Sirius measurements, the p values were 0.006 (Haigis), 0.001 (Hoffer Q), 0.005 (Holladay 1), and 0.048 (SRK/T). In all cases, a more negative Q-value, i.e. a prolate cornea, was associated to a myopic outcome, whereas a more positive Q-value, i.e. an oblate cornea, was associated to a hyperopic outcome. The highest coefficient of determination R2 (0.2630) was detected between the Hoffer Q formula and the Keratron, for which the error in refraction prediction (y) was related to the Q-value (x) according the formula y= -0.2641 + 1.4589*x.

Conclusions:

Corneal asphericity influences the refractive outcome of IOL implantation and should be taken into consideration when using third generation IOL power formulas.

Financial Interest:

One or more of the authors... gains financially from product or procedure presented