How the cornea contributes to IOL power calculation

Chicago-Under the best of circumstances-meaning when cataract surgery is performed in an eye with a normal cornea by expert hands and with use of an advanced IOL power calculation formula-the achieved refractive outcome will be more than 0.5 D off target in 1 out of every 11 eyes.

And in eyes with more complex corneas, cataract surgeons face a heightened challenge for achieving accuracy in their IOL power calculations.

“There is clearly much that needs to be done,” said Douglas D. Koch, MD, The Allen, Mosbacher, and Law Chair of Ophthalmology and Professor of Ophthalmology, Baylor College of Medicine, Houston, delivering the 73^rd Jackson Memorial Lecture at AAO 2016.

In his talk, “Hiding in Plain Sight: The Enigmatic Cornea and IOL Calculations,” Dr. Koch used a case-based discussion to review how the cornea contributes to IOL power calculation errors, the progress that has been made toward overcoming the various problems, and areas of forthcoming advances for solving the challenges that remain. 

Dr. Koch demonstrated how inaccurate measurements of anterior corneal power represent one source for IOL power calculation errors.

Therefore, in listing requirements for reducing and managing corneal measurement errors, Dr. Koch identified the importance of having well-trained technicians to obtain the measurements and of ensuring that the cornea is as healthy as possible with an optimal tear film.

In addition, he emphasized the need for surgeons to be skeptical about the data they are given, critically evaluating its quality and looking for inter-device agreement using more than one instrument for measurement. 

Several cases presented by Dr. Koch highlighted the importance of accounting for the effect of the posterior cornea on total corneal power.

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