Subjective refraction in eyes with multifocal IOLs.

To the Editor: Piñero et al,1 in the August 2010 issue of the Journal of Refractive Surgery, addressed the complexity of obtaining refraction in eyes that have been implanted with multifocal intraocular lenses (IOLs). It has been shown that automated and wavefront refractors may not yield accurate measurement of residual refractive error for secondary laser vision correction in eyes with multifocal IOLs,2 and manifest refractions are likely to be affected by the multifocality of these lenses.3 Piñero et al1 suggested an averaging approach to the midpoint where the patient maintains 20/20 vision. This subjective clue should at least partly avoid the variability in the spherical component of the refraction. We describe our approach in refracting such eyes especially when a keratorefractive enhancement is planned. 1. Create a high mesopic (9 lux) or photopic condition. 2. Correct the keratometric cylinder error (at the spectacle plane) if needed (it is assumed that the multifocal IOL is not tilted); add the corresponding sphere (1⁄2 cylinder of opposite sign). For partial monovision, we aim for mild distance dominance in the right eye and mild near dominance in the left eye (this should be modifi ed based on the patient’s lifestyle, occupational demand, and ocular dominance). 3. Right eye: we move the distance point farther with a minus lens (beyond IOL calculation error; approximately 2.00 diopters [D]). Then, we decrease the minus to achieve 20/20 distance vision. If simultaneous J2 (or even J3) or better near acuity is present, this is the endpoint. 4. Left eye: we move the distance point close with a positive lens (approximately 2.00 D). Then, we decrease the positive. As soon as J1 acuity at 40 cm is achieved, we check the distance vision; if an acuity of 20/25 or better is reached, this is the endpoint. 5. Binocular vision is measured next. The patient is expected to see 20/20 and J1 simultaneously. This highly subjective and customized approach is a necessity. Conventional refraction in eyes with multifocal IOLs is unstable and highly dependent on the ambient light; therefore, any discussion about visual acuity without noting the luminance level is of little value.4 Step 3 of our method is similar to what has been suggested previously, ie, pushing toward the most hyperopic refraction possible that refracts the distance portion of the lens.3 However, this does not ensure fulfi llment of far and near visual demands and does not address ocular dominance. Correcting these eyes through wavefront-guided ablation is controversial.5 The laser would try to rectify higher order aberrations as well as the spherocylindrical residual error.2 Multifocality and higher order aberrations are two facets of the same phenomenon and create depth of fi eld. Therefore, an aberrometry-guided correction may attenuate this desired symmetrical aberration induced by a multifocal IOL. S-Farzad Mohammadi, MD Nazanin Rahman-A, MD Arash Mazouri, MD Tehran, Iran