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Aspheric, spherical IOLs yield similar corrected distance visual acuity
J Cataract Refract Surg. 2010;36(9):1536-1542.
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A single-piece aspheric IOL yielded markedly less spherical aberration than a spherical IOL, a study found.
However, both implants showed similar stability in the capsular bag, the study authors said.
"We found that the hydrophobic acrylic aspheric IOL significantly reduced postoperative ocular spherical aberration, which is reflected in improvement in subjective visual function under mesopic conditions," they said. "Although the aspheric IOL is single-piece, it attained a satisfactory level of centration in the capsular bag that was no different from that of the multi-piece spherical IOL."
The prospective, randomized study included 56 eyes of 28 patients implanted with a single-piece aspheric Tecnis ZCB00 IOL in one eye and a Sensar AR40e spherical IOL (both Abbott Medical Optics) in the contralateral eye. Patients had a mean age of 66.05 years.
Patients with corrected distance visual acuity below 0.05 logMAR, corneal astigmatism of more than 1.5 D, irregular astigmatism, and ocular pathologies aside from cataract that may compromise visual function were excluded.
Primary outcome measures were distance visual acuity, wavefront aberrometry and contrast visual acuity. Patients were evaluated 1 day, 1 week, 3 weeks and 2 months postoperatively. In addition, a patient questionnaire was used to assess subjective visual quality.
Study results showed a statistically insignificant between-group difference in postoperative corrected distance visual acuity. Eyes implanted with aspheric IOLs had statistically significantly lower spherical aberration than eyes that received the spherical IOL.
The aspheric IOL group had statistically better mesopic contrast sensitivity than the spherical IOL group. On the questionnaire, 20 of 28 patients reported better visual quality in the eye implanted with an aspheric IOL. One patient reported better visual quality with a spherical IOL. Seven patients reported no differences between eyes.
There were no significant between-group differences in postoperative ocular coma or trefoil, the authors said.
Drs. Assaf and Kotb evaluated differences in contrast sensitivity and spherical aberration in a comparison study of hydrophobic acrylic aspheric and spheric IOLs. They found that the aspheric IOLs yielded better results in terms of photopic and mesopic contrast sensitivity and were preferred by the masked patients in regards to quality of vision. This preference for the aspheric IOLs is an important finding since the traditional methods of testing visual acuity did not yield a significant difference, yet in subjective measures, the patients noticed the improvement in visual quality. The results of this study explain why the use of aspheric IOLs has been steadily increasing worldwide.
– Bonnie An Henderson, MD
OSN Cataract
Surgery Board Member