Significant Differences in Corneal Parameter Measurements

As the recently published article in the journal Open Ophthalmology Journal shows, there are significant differences among the measures of corneal parameters obtained by the three most commonly used ophthalmic devices, called topographers.

This is a critical issue for doctors seeking to achieve the best patient outcomes for eyesight recovery after cataract surgery. The calculation of the astigmatic power required for the intraocular lens (IOL) that is to be implanted after cataract surgery is based on the magnitude and axis of corneal astigmatism considered, which can be measured and calculated using different topographers. The accuracy when calculating the appropriate IOL determines the quantity and quality of vision of the post-operative cataract patients and also defines their need for spectacles after the surgery.

This work, published by a team of ophthalmologists from Spain, compares the measures obtained from:

• Pentacam system (Oculus Optikgeräte GmbH, Wetzlar, Germany)
• Cassini (i-Optics, The Hague, The Netherlands, distributed by Ophtec)
• IOL-master 700 system (Carl Zeiss Meditec AG, Jena, Germany)

These three devices measure corneal parameters using different technologies.

The prospective comparative study reviews data from 94 eyes from 53 patients ranging in age from 29 to 77 years old, recruited from the anterior segment consultation at Vithas Eurocanarias Instituto Oftalmológico in Las Palmas de Gran Canaria (Spain).

"Standard and total keratometric readings and astigmatism measures obtained with these devices cannot be used interchangeably, as there are statistically significant and clinically relevant differences among the results obtained," notes Dr. Humberto Carreras, one of the three co-authors of the paper. "Therefore, if the data of these three systems are used for toric IOL power calculations, significant differences can be expected, what will affect the post-op vision in the cataract patients?"

The authors recommend that refractive predictability studies hold the answer to this question, and this needs to be investigated further for each type of optometric device.