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Cover Focus | Sep 2015

Hitting the Spot

Determining the location of the corneal vertex may be helpful in planning refractive cataract surgery treatments and in correcting residual refractive errors.

Finding the corneal vertex and basing a refractive cataract surgery treatment around this axis is one surgeon’s strategy for hitting his target refraction and correcting residual refractive errors postoperatively.

According to Damien Gatinel, MD, Assistant Professor and Head of the Anterior Segment and Refractive Surgery Department at the Rothschild Ophthalmology Foundation, Paris, and a CRST Europe Editorial Board member, all refractive surgery procedures—including cataract surgery with premium IOL implantation—achieve better postoperative results when the treatment is centered close to the corneal vertex.1 This is because the corneal vertex is closer to the visual axis than other spots on the cornea.

Dr. Gatinel follows two rules in centering his treatments:
(1) He chooses an axis between the center of the entrance pupil and the corneal vertex; and, (2) the larger the angle K (the angle between the line of sight and the pupillary axis), the closer to the corneal vertex he places the treatment axis. He has also found that centering the capsulorrhexis temporally allows him to position the IOL nasally, resulting in good postoperative stability.

The corneal vertex is visible on clinical images as the projection of the center of the first Purkinje image when the patient fixates on a light source that is coaxial with the camera. Diagnostic technologies that can be used to locate the vertex include the iTrace (Tracey Technologies), OPD Scan (Nidek), AcuTarget HD (AcuFocus/SensoMetric Instruments), and Orbscan (Bausch + Lomb).

1. Gatinel D. Centering corneal and intraocular procedures: Surgeon’s perspective. Paper presented at: The XXXII Congress of the ESCRS; September 13-17, 2014; London.