Positional accommodative intraocular lens power error induced by the estimation of the corneal power and the effective lens position

Purpose:

To evaluate the predictability of the refractive correction achieved with a positional accommodating intraocular lenses (IOL) and to develop a potential optimization of it by minimizing the error associated with the keratometric estimation of the corneal power and by developing a predictive formula for the effective lens position (ELP).

Materials and Methods:

Clinical data from 25 eyes of 14 patients (age range, 52–77 years) and undergoing cataract surgery with implantation of the accommodating IOL Crystalens HD (Bausch and Lomb) were retrospectively reviewed. In all cases, the calculation of an adjusted IOL power (P_IOLadj) based on Gaussian optics considering the residual refractive error was done using a variable keratometric index value (n_kadj) for corneal power estimation with and without using an estimation algorithm for ELP obtained by multiple regression analysis (ELP_adj). P_IOLadj was compared to the real IOL power implanted (P_IOLReal, calculated with the SRK-T formula) and also to the values estimated by the Haigis, HofferQ, and Holladay I formulas.

Results:

No statistically significant differences were found between P_IOLReal and P_IOLadj when ELP_adj was used (P = 0.10), with a range of agreement between calculations of 1.23 D. In contrast, P_IOLReal was significantly higher when compared to P_IOLadj without using ELP_adj and also compared to the values estimated by the other formulas.

Conclusions:

Predictable refractive outcomes can be obtained with the accommodating IOL Crystalens HD using a variable keratometric index for corneal power estimation and by estimating ELP with an algorithm dependent on anatomical factors and age.     

Chromatic-achromatic perimetry in four clinic cases: Glaucoma and diabetes

Background:Some diseases that affect the visual system may show loss of chromatic-achromatic sensitivity before obvious physical signs appear in the usual examination of the eye''s posterior segment. A perimetric study has been conducted with four typical patients with glaucoma and diabetes, at different stages of the disease.Results:The results seem to indicate losses in the achromatic-parvocellular perimetry and both chromatic perimetry tests, undetected by conventional SAP.Conclusions:Our results illustrate that our patients without visible retinal alterations show signs of suspicion in multichannel perimetry.