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Toric lens improves simulated night driving performance more than PRK
J Refract Surg. 2010;26(5):321-326.
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A toric implantable lens performed better than PRK in a night driving simulation with and without glare, a study showed.
"A carefully constructed performance-based task, such as night driving simulator testing, can accurately assess real-life visual performance, and several such studies have been reported," the study authors said. "The results have intrinsic meaning and, by definition, can relate directly to a task performance. One of the strengths of this study is that it used a performance-based task to assess surgical outcomes."
The prospective, randomized study included 43 eyes implanted with the Visian Toric Implantable Collamer Lens (TICL, STAAR Surgical) and 45 eyes that underwent PRK with mitomycin C.
All eyes presented with 6 D to 20 D of myopia measured at the spectacle plane and 1 D to 4 D of astigmatism.
A subset of 27 eyes of 14 patients implanted with the TICL and 41 eyes of 21 patients who underwent PRK took a simulated night driving test. The detection and identification of road signs and hazards were measured with and without glare preoperatively and 6 months postoperatively.
Study data showed no significant between-group differences between preoperative and postoperative distance detection with the simulator.
Patients in the TICL group identified the distance of business signs, traffic signs and pedestrian hazards without glare significantly better than those in the PRK group. However, with glare, the TICL patients identified only pedestrian hazards better than those in the PRK group.
Acuity of vision on an eye chart is one thing, but visual function for certain tasks is how we really gauge our satisfaction overall when it comes to surgical correction of vision. This study evaluates two different procedures, one that is gaining in use, and the other that is not used anymore, as wavefront-guided procedures have replaced standard procedures over the last several years as they have been shown to improve night vision overall.
Still, the information is clinically useful, as it is also our clinical judgment that as we encounter higher levels of myopia, that implants work better than laser vision correction. As more information is accumulated and presented, we will be able to come up with better information to help us decide when intraocular procedures are better than corneal procedures. To get that information, we would need a study similar to this with similar numbers to this study in each of several groups — for example –6 D to –8 D, –8 D to –10 D, –10 D to –12 D, etc. In my practice, I typically switch to intraocular procedures around –8 D if all else is normal for an eye, but even at lower levels of correction — usually about –6 D — if LASIK is not an option and PRK would be needed. Hopefully, further studies like this will answer those questions in the future.
– David R. Hardten, MD
OSN
Cornea/External Disease Section Editor
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