Calculation of phakic IOLs: questions and errors

Session Details

Session Title: Phakic IOLs I

Session Date/Time: Monday 07/09/2015 | 14:30-16:30

Paper Time: 15:12

Venue: Room 10

First Author: : B.Babayeva AZERBAIJAN

Co Author(s): :    B. Leyla                    

Abstract Details

Purpose:

Using of phakic intraocular lens for correction of myopia and hyperopia became popular recently. Laser refractive surgery has been overwhelming prevalence over the past decade, however it has significant limitations in the selection of patients and to obtain the desired results. Some authors determine refractive errors in more than 1/3 of patients older than 40 years. Young and medium age, high socio-economic activity of duofakic patients would lead us to accurate calculation of phakic IOLs. As shown by our observations, calculation of phakic IOL in different ways does not allow the surgeon to be sure of the correct selection.

Setting:

All studies were conducted at the Azerbaijan National Center of Ophthalmology named after Academician Z.A.Alievoy

Methods:

Taking into account above, we set out to calculate and compare the optical power of phakic IOLs in according to the formula: IOL=1336/(1336/(K+Refc)- ELP)-1336/(1336/K- ELP) and by IOL-Master at patients with various biometric conditions. We analyzed the results obtained in 2 groups. Group 1: ACD from 2.0 to 5.0 mm with 0.1 mm step and refraction, presented the following subgroups: -3.0; -6.0; - 9.0; -12.0; -15.0; -18.0; -21.0 D. The average keratometry was unchanged at 43.5 D. In each case, the optical power of phakic IOL (Oftek Artisan) was calculated using the formula I IOL=1336/(1336/(K+Refc)- ELP)-1336/(1336/K- ELP) and by IOL-Master.

Results:

In moderate myopia difference in phakic IOL power was no greater 1.0D, -9.0D - up to 1,5D, -12.0D - 1.5D- 3,0D. Refraction -15,0D gives a difference 2.5-3.0D, -18,0D - 3.5D -4,0D, -21.0 -5.0D. Also we compared the optical power of phakic IOLs, when ACD = 3.5 mm, constant average keratometry= 43.5D, while refraction ranged -3.0 -21.0D. In cases of refraction -3.0 to -3.5D difference was not observed. When refraction was -4,0-7,0D difference was 0.5D; from -7.5 to -10,5D - 1.0D; from -11.0 to -12,0D - 1.5D; -12,5-13,5D - 2,0D; -14,0-15,5D - 2.5D; -15,5-17,5D - 3.0D; -18,0-19,5D - 4,0D; -20,0-21,0- 4.5D.

Conclusions:

Thus, it becomes apparent that under identical biometric data, the results obtained by calculation according to the formula and the IOL-master, are significantly different from each other. The difference can be up to 4,5-5,0D. In summary, there are no objective data, allows the surgeon to make the right choice. This approach to the selection of phakic IOL, based only on surgeon's personal preferences, is completely inappropriate at the present level of surgery and requires serious and voluminous studies.

Financial Interest:

NONE