Exploring pupil dynamics in cataract patients
Pupil location and dynamics are very important in cataract and refractive surgery, but they are still in uncharted territory, Dr Imène Salah-Mabed told delegates attending the XXXV Congress of the ESCRS.
Dr Salah-Mabed said that because the human eye is a non-centred optical system, the pupillary axis, the line of sight and the visual axis do not match up.
“The corneal vertex is a good reference for studying pupil centre location,” she said. This is represented by Purkinje I, which, using the coaxially sighted the corneal reflex, correlates with the corneal vertex.
Dr Salah-Mabed used Alcon’s Topolyzer Vario to perform measurements of myopic and hyperopic eyes. She demonstrated that the pupil centre location is temporal to the corneal vertex. The distance is around 250 microns under mesopic and photopic conditions, and this distance is greater in hyperopic eyes than in myopic eyes.
“Treatments can thus be de-centred nasally by 75% of the distance between the pupil centre and the corneal vertex,” she advised. The repeatability of these measurements using the Topolyzer has been demonstrated, and the results were published earlier this year in the Journal of Refractive Surgery.
Also of note, pupil diameters decrease after cataract surgery, and the postoperative pupil size can be predicted, which is useful to identify patients who might be appropriate for multifocal IOLs.