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Mesopic pupil diameter affects spherical aberration after cataract surgery
J Cataract Refract Surg. 2009;35(1):57-63.
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Reduced spherical aberration improved visual function in photopic and mesopic conditions after cataract surgery.
Earlier studies showed that reduced postoperative spherical aberration by aspheric IOLs improved visual function, whereas other studies showed no significant difference in visual function between spherical IOLs and aspheric IOLs. These studies did not account for individual pupil diameter.
“This is important because corneal spherical aberration varies widely in the population, and pupil diameter, which affects the amount of spherical aberration, also varies widely among individuals,” the study authors said.
The study included 107 eyes of 79 patients with a mean age of 68 years. Investigators measured preoperative and postoperative best corrected visual acuity, higher-order aberrations, contrast sensitivity and pupil diameter under photopic and mesopic conditions 1 month after surgery.
After surgery, spherical aberration in photopic conditions ranged from –0.12 µm to +0.34 µm; spherical aberration in mesopic conditions ranged from –0.14 µm to +0.55 µm. Data showed no statistically significant link between pupil diameter and spherical aberration in photopic conditions. However, results showed a statistically significant correlation between pupil diameter and spherical aberration in mesopic conditions (P < .001).
Further study is needed to assess the feasibility of customizing spherical aberration on individual pupil diameter by an aspheric IOL.
In this study, patients were randomized to receive a variety of aspheric or spherical IOLs. The authors state that “this is the first study showing that postoperative visual function is negatively correlated with postoperative spherical aberration.” In fact, the night driving simulation study of the Tecnis IOL (Advanced Medical Optics) performed as part of the U.S. Food and Drug Administration-monitored clinical investigation demonstrated a similar statistically significant negative correlation of spherical aberration with identification distance for the pedestrian target under glare conditions. These findings support the concept of customized selection of aspheric IOLs based on preoperative corneal spherical aberration in order to minimize postoperative spherical aberration.
(Packer M, Fine IH, Hoffman RS. Aspheric intraocular lens selection: the evolution of refractive cataract surgery. Curr Opin Ophthalmol. 2008;19(1):1-4)
– Mark Packer, MD, FACS
Drs. Fine, Hoffman and Packer Ophthalmologists, Eugene,
Ore.