Investigators examined the effect of manifest refraction spherical equivalent error on visual acuity in eyes with trifocal IOLs.
Study design
This was a prospective study that assessed the effect of different spherical equivalent errors of 60 eyes of 30 patients implanted with the Panoptix trifocal IOL. Preoperative exclusion criteria were any pathology of the cornea, macula or optic nerve; opaque media other than cataract; history of ocular inflammation or surgery; corneal astigmatism of +1.0 D or greater; marked irregular astigmatism; amblyopia; and any difficulties with examinations or follow up.
At 6 months or more postoperatively, the patient’s full distance manifest refraction via autorefraction was obtained and visual acuity (VA) was measured with addition of +1.0, +0.5, 0.0, -0.5, and -1.0 D were placed over the refraction at distances of infinity, 5, 3, 2, 1, 0.7, 0.5 and 0.3 m.
Outcomes
A mean logMAR VA of 0 was achieved at all distances except at 0.3 m in the no lens group. A mean logMAR VA of 0 was achieved at intermediate and near distances for the +0.5 D and +1.0 D groups, but not for infinite distance. A mean logMAR VA of 0 was achieved only at intermediate distance in the -1.0 D group, while a mean logMAR VA of 0 was achieved at intermediate and far distances in the -0.5 D group.
Limitations
Monofocal, and especially diffractive, IOLs are sensitive to defocus. Although this study simulated the manifest refraction spherical equivalent, it did not examine the actual postoperative spherical equivalent error on uncorrected visual acuity, only the simulation of refractive error. Only an autorefraction was performed instead of a manifest refraction, which decreases the predictability of the study. Astigmatism of up to 1.0 D was included and not treated, which is a significant confounding variable as astigmatism degrades VA of diffractive IOLs more so than monofocal ones. Finally, this study did not compare the results with other multifocal or extended depth of focus lenses.
Clinical significance
Trifocals are not available yet in the United States, but knowing and understanding the potential options in the future will allow for a better initial experience when the IOLs arrive. Realizing that the IOL is less sensitive to a slightly myopic target will allow for better targeting when the IOL gains approval. As this targeting strategy is similar to current technologies, this should allow for easier adoption of this new technology and provide better overall patient satisfaction.