Multifocal Intraocular Lens Differentiation Using Defocus Curves

Abstract

PURPOSE. To determine the most appropriate analysis technique for the differentiation of multifocal intraocular lens (MIOL) designs by using defocus curve assessment of visual capability.METHODS. Four groups of 15 subjects were implanted bilaterally with either monofocal intraocular lenses, refractive MIOLs, diffractive MIOLs, or a combination of refractive and diffractive MIOLs. Defocus curves between À5.0 D and þ1.5 D were evaluated by using an absolute and relative depth-of-focus method, the direct comparison method, and a new ''area-offocus'' metric. The results were correlated with a subjective perception of near and intermediate vision. RESULTS.Neither depth-of-focus method of analysis was sensitive enough to differentiate between MIOL groups (P > 0.05). The direct comparison method indicated that the refractive MIOL group performed better at þ1.00 diopter (D), À1.00 D, and À1.50 D and worse at À3.00 D, À3.50 D, À4.00 D, and À5.00 D than did the diffractive MIOL group (P < 0.05). The area-of-focus intermediate zone was greater with the refractive than with the diffractive MIOL group (P ¼ 0.005) and the near zone was better with the diffractive (P ¼ 0.020) and ''mix and match'' (P ¼ 0.039) groups than with the refractive MIOL group. The subjective perception of intermediate and near vision agreed best with the area-of-focus metric for the intermediate (r s ¼ 0.408, P ¼ 0.010) and near zone (r s ¼ 0.484, P < 0.001).CONCLUSIONS. Conventional depth-of-focus metrics provide a single value to quantify the useful range of vision; however, they fail to provide sufficient detail to differentiate between MIOL designs. The direct comparison method provides a large amount of information, although the results can be complex to interpret. The proposed area-of-focus metric provides a simple, but differentiating method of evaluating MIOL defocus curves. (Invest Ophthalmol Vis Sci. 2012;53:3920-3926 Previous in vivo MIOL studies have examined the visual range of MIOLs by using measurements of visual acuity (VA) either at varying distances 4-6 or through different levels of spectacle lens defocus.7-9 However, the more physical method of measuring VA at varying distances is often impractical owing to the need to control angular image size and luminance.Measuring VA through a range of spectacle lenses creates a defocus curve profile. A previous study has suggested that VA measured with this method provides an underestimation of the true VA at the corresponding distance owing to the magnification effects of lenses in the spectacle plane (although this can be compensated for mathematically 10 ) and the disrupted natural associated convergence and pupil response. 11The two focal points created by the conventional bifocal MIOL result in a distinctive defocus curve profile with two peaks of optimum acuity: one at the distance focal point and the other at the near focus. 6 Hence, defocus curves demonstrate the strength of the near addition (the separation in diopters between the distance and near peak) as well as the quality of vis...

Randomized Crossover Trial of Silicone Hydrogel Presbyopic Contact Lenses

“…There was an interaction between lens types and acuity at different levels of defocus, showing that the lens types worked differently from one another, with monovision and the Biofinity design generally outperforming the OASYS and Air Optix Aqua designs. However, similar to the findings of Gupta et al, 3 the near-vision peak, commonly observed in multifocal intraocular lens designs, 37 was not evident in the present study. This is likely to occur because of the difficulty in constructing sharp transitions in lens molds leading to intermediate distance focused transitions even in the less aspheric designs.…”

Visual outcomes in eyes with a distance-dominant diffractive multifocal intraocular lens with low near addition power

“…A recent trend is the combined implantation of different multifocal IOLs in each eye. Studies showed that combined implantation of refractive and diffractive multifocal IOLs provides better near vision than bilateral implantation of the same IOL due to binocular summation 24 25. Accordingly, combined implantation of the ReSTOR +2.5 D and other near-dominant diffractive IOL may be a useful option for correcting presbyopia.…”

Short‐term outcomes of combined implantation of diffractive multifocal intraocular lenses with different addition power

“…Buckhurst et al. () reported that patients who underwent combined implantation of refractive and diffractive MIOLs have binocular near and intermediate vision comparable to that of patients who underwent bilateral implantation of the same refractive or diffractive MIOL. No studies to date, however, have examined binocular visual function with mix and match implantation of diffractive MIOLs.…”

“…Recent studies using a stricter study design also showed that combined implantation of refractive and diffractive MIOLs provided better near vision than bilateral implantation of the same refractive IOL (Buckhurst et al. ; Lin et al. ).…”