Autorefraction after Multifocal IOLs

Autorefraction after Multifocal IOLs Dear Editor: Subjective or manual refraction (MR) is the method of choice to determine the refractive status after cataract surgery, but it is a time-consuming procedure and requires trained technicians. To determine where to start MR, several techniques can be used, including autorefraction and retinoscopy. The popularity of autorefractors is attributable to their ease of use and availability, and they are now present in nearly all ophthalmology offices. However, autorefraction is not sufficiently accurate to be a substitute for MR for the purposes of determining best-corrected visual acuity after cataract surgery or for prescribing eyeglasses.1 Moreover, autorefraction’s accuracy decreases in clinical situations such as the presence of media opacities, an intraocular lens (IOL), or previous corneal refractive surgery.2,3 Multifocal IOLs are designed to reduce dependence on eyeglasses after cataract surgery.4,5 Multifocal IOLs provide projection onto the retinal plane of images set at various distances by using concentric rings of varying optical power. This may cause scattering of the infrared beams used by autorefractors, resulting in inexact measurements in the presence of these kinds of IOLs. We have studied the repeatability and accuracy of autorefraction compared with MR in patients implanted with 3 types of currently used multifocal IOLs: ReZoom (refractive) (AMO, Santa Ana, CA), ReStor (diffractive) (Alcon, Fort Worth, TX), and Tecnis Multifocal ZM900 (diffractive) (AMO). These IOLs are widely used in Europe after cataract and clear lens extraction procedures. Regarding repeatability of autorefraction measurements, we have found that the first autorefraction measurement and the 2 means of 3 consecutive autorefraction measurements for both nondilated and dilated pupils did not significantly differ. We also have found that multiple measurements did not improve agreement of autorefraction and MR measurements. In our experience, there is not significant variability across consecutive autorefraction measurements in the presence of any of these 3 types of multifocal IOLs for both nondilated and dilated pupils. In the case of the ReZoom IOL, autorefraction showed a tendency toward more negative values of sphere compared with MR, with a mean difference of approximately ⫺1.00

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diopter (D). However, in the case of the Tecnis Multifocal and ReStor IOLs spherical values determined by autorefraction and MR did not differ statistically. Autorefraction astigmatic measurements showed excellent agreement with MR astigmatism in the presence of the 3 kinds of multifocal IOLs, with ⬍10% of cylinder measurements by autorefraction more than 0.25 D different from the manifest values. Table 1 (available at http://aaojournal.org) shows the Pearson correlation coefficients between autorefraction and MR for the 3 components of vector analysis (M, J0, and J45) and for the 3 models of IOLs. Table 2 (available at http:// aaojournal.org) shows the mean difference between autorefraction and MR sphere and astigmatism for the 3 kinds of IOLs. In summary, in the presence of a diffractive multifocal IOL (Tecnis Multifocal or ReStor) autorefraction has proved useful as a starting point for MR, for both spherical and astigmatic values. In the presence of a refractive multifocal IOL (ReZoom), autorefraction astigmatic measurements can also be used as a starting point for MR, but autorefraction negative spherical values should be underestimated. For instance, if autorefraction gives a spherical value of ⫺2.00 D, the starting point of sphere for MR should be ⫺1.00 D. The ReZoom IOL uses 5 concentric refractive zones alternating distant and near zones, which may explain this kind of instrument pseudomyopia. GONZALO MUÑOZ CÉSAR ALBARRÁN-DIEGO HANI F. SAKLA Valencia, Spain References 1. Wood ICJ. A review of autorefractors. Eye 1987;1:529 –5. 2. Raj PS, Akingbehin T, Levy AM. Objective autorefraction in posterior chamber pseudophakia. Br J Ophthalmol 1990;74: 731–3. 3. Siganos DS, Popescu C, Bessis N, Papastergiou G. Autorefractometry after laser in situ keratomileusis. J Cataract Refract Surg 2003;29:133–7. 4. Bellucci R. Multifocal intraocular lenses. Curr Opin Ophthalmol 2005;16:33–7. 5. Leyland M, Zinicola E. Multifocal versus monofocal intraocular lenses in cataract surgery. A systematic review. Ophthalmology 2003;110:1789 –98.

Letters to the Editor Table 1. Correlation Coefficients between Autorefraction and Manifest Refraction for the 3 Components of Vector Analysis for the 3 Intraocular Lenses Used in the Study

Table 2. Mean Difference between Autorefraction and Manifest Refraction (MR) for the 3 Kinds of Intraocular Lenses Studied Difference (Autorefraction ⴚ MR)

Pearson Correlation ReZoom (n ⫽ 144) ReStor (n ⫽ 37) Tecnis MF (n ⫽ 65)

M

J0

J45

0.55 0.86 0.83

0.79 0.89 0.81

0.71 0.79 0.92

ReZoom (n ⫽ 144) ReStor (n ⫽ 37) Tecnis MF (n ⫽ 65)

Sphere

Cylinder

⫺0.94⫾0.87 0.03⫾0.09 ⫺0.05⫾0.11

⫺0.12⫾0.18 ⫺0.02⫾0.06 ⫺0.04⫾0.07

J0, J45 ⫽ cylinder values; M ⫽ spherical value.

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