Posters

IOL optic power calculation in extreme myopia patients

Poster Details

First Author: A. Tsygankov RUSSIAN FEDERATION

Co Author(s):    A. Tsygankov   N. Pashinova   S. Legkih              

Abstract Details

Purpose:

Known formulas for IOL calculating are well adapted for the non-operated eyes with medium axial length (22.0-24.5 mm). However, phacoemulsification with IOL implantation in patients with high myopia requires further adjustment in the calculation formulas. Calculation and selection of the IOL is one of the major problems in modern refractive surgery. Our purpose was to identify the IOL optical power calculation characteristics, to optimize the constants and to choose the optimal calculation formula to achieve the target refraction ± 1,0 diopters in extremely high myopia patients.

Setting:

Excimer Eye Centre, Moscow, Russian Federation

Methods:

The study included 58 patients (88 eyes) with extremely high myopia (axial length more than 27.9 mm). All patients conducted cataract phacoemulsification (84.1%) or clear lens (15.9%) with IOL implantation (AcrySof MA60MA with optic power -5 - +5 D in 94.5% cases). Average follow-up was 12.4 ± 2.5 months. Patients were divided into two groups - with implantation of 'minus' IOL (n=18) and 'plus' IOL (n=70). IOL power calculation was performed using the formula SRK / T, retrospective comparison - Hoffer-Q, Holladay II, Haigis and Barrett formulas, the amount of SIA was determined with the help of SIA Calculator v.2.1.

Results:

Under the 'plus' -IOL each of the five investigated formulas (SRK / T, Hoffer-Q, Holladay II, Haigis and Barrett) can be used. Postoperative spherical equivalent was ± 1,0 diopters of refractive error target of 68%, 54%, 52%, 65% and 99%, respectively. In the group of 'minus' IOL there was a hyperopic shift, with the postoperative spherical equivalent ± 1,0 diopters of refractive target of 37%, 44%, 53%, 71% and 96% of cases. Optimization of constants for all five formulas was performed. The amount of SIA and frequency of intra- and postoperative complications between the two groups did not differ significantly.

Conclusions:

Cataract or clear lens phacoemulsification with IOL implantation in extremely high myopia patients is an effective method of correction of visual acuity. It does not affect the incidence of complications. In the group of patients with implantation of the 'plus'-IOL there were no significant differences between the target and calculated values of spherical equivalent using formulas SRK / T, Hoffer-Q, Holladay II and Haigis, using Barrett formula showed the best accuracy in IOL power prediction . For patients in the 'minus' -IOL group it is preferable to use the Barrett and Haigis formulas.

Financial Disclosure:

NONE