OSN SuperSite Top Story 4/4/2007

Inaccurate preop measurements most frequent cause of incorrect IOL powers

An incorrect measurement of preoperative corneal power was the most frequent reason identified for implanting an incorrectly powered IOL leading to unexpected postoperative refractive errors, according to a study by researchers in Utah.

George J.C. Jin, MD, PhD, and colleagues reviewed 22 eyes treated with IOL exchange to correct unexpected refractive errors after cataract surgery.

The researchers sought to "determine the sources associated with the errors and derive an empiric approach to estimating the power for IOL exchange." They found that incorrect corneal power determination and incorrect axial length determination were the main causes of incorrect IOL power implantation.

Of the 22 eyes, five eyes (23%) had received an incorrectly powered IOL due to keratometry errors and three eyes (14%) had an incorrect axial length determination. In another three cases, surgeons had implanted the wrong IOL, according to the study authors.

After lens exchange, 18 eyes (82%) were within ±0.5 D of emmetropia and 19 eyes (86%) were within ±1 D. Also, 82% of eyes achieved an uncorrected visual acuity of 20/40 or better, and 95% achieved a best corrected visual acuity of 20/40 or better, the authors reported.

"The correlation between change of refraction and IOL power was significant (P < .002)," the authors said.

"The pre-exchange refraction can be used theoretically to calculate the IOL power for exchange," they noted.

The study is published in the March issue of Ophthalmology.

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