A recent study from Italy has shown that performing corneal topography over a multifocal lens is an acceptable and accurate method to assess centration. The researchers found the technique’s reliability was not affected by operator experience. They also hope that their topography method could be expandable to other multifocal lens designs.

The study fitted daily disposable multifocal lenses on both eyes of 22 subjects. For each lens fit, the researchers took a slit lamp digital picture and videokeratograph image in a rapid but randomized sequence. The researchers then used photo-editing software to retrospectively assess the position of the lens’ center with respect to the pupil’s center as taken from the slit lamp photograph, and an algorithm automatically detected the position of the lens center as the point of maximum curvature from the videokeratography.

The study then had four practitioners each perform three manual and qualitative procedures to detect the multifocal’s center, comparing a template of the contact lens’s optic zones to the videokeratographic image using three different algorithms. The researchers found the accuracy of the four topographic assessments to be good.

“Considering that the slit lamp assessment of multifocal lens centration does not allow an easy detection of centration due to the need for analysis on a digital image, the videokeratography assessment of multifocal lens centration could represent a suitable tool in clinical practice that in a near future could be incorporated in new releases of topographer’s software,” the researchers concluded. 

Zeri F, Di Vizio A, Guida M, et al. Accuracy, inter-observer and intra-observer reliability in topography assessment of multifocal contact lens centration. Cont Lens Anterior Eye. February 19, 2020. [Epub ahead of print].