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Improving gonioscopy

Automated imaging device opens the door to new understanding.

Cheryl Guttman Krader

Posted: Wednesday, April 1, 2020

Automated gonioscopy is a useful new imaging technique for topographic analysis of the iridocorneal angle, according to Professor Jean-Paul Renard MD.
Speaking at the ESCRS/EGS Glaucoma Day meeting, Prof Renard described the technology, its operation and limitations. He also provided numerous examples demonstrating its value for patient care, research, training and medicolegal documentation.
“By providing rapid visual access to the angle, automated gonioscopy allows more frequent examination of this essential zone in clinical practice. This device gives precise topographic localisation of any abnormalities and facilitates follow-up of the angle in glaucoma and all angular illnesses,” said Prof Renard, Ophthalmological Center Breteuil, and Hôpital Cochin Paris Descartes University, Paris, France.
The technology is based on the concept of an electronic image acquisition system adapted for an acquisition over 360°. It incorporates a Goldmann goniolens with 16 mirror-coated facetted lenses to observe the various sites of the angle.
The tip of the device comes in indirect contact with the ocular surface through a 1.5mm thick disk of ophthalmic gel on the surface of the prism. The examination is completed in approximately one minute.
Seventeen images are acquired from each facet of the prism on a focal length of 5mm. A rotary function scans all facets of the mirrors in order to acquire optimal images of each portion at various focal planes. The instrument’s software creates assembled images of the best focused images, providing both linear and circular 360° representation of the angle. The device also features data storage.
Prof Renard presented high-resolution images from examinations showing that automated gonioscopy allows analysis of the anatomical landmarks of the angle, the degree of angle opening, the iris root insertion level, the iris periphery and the amount of pigmentation. Additional examples included images from eyes with polycystic ciliary body disease, synechiae, traumatic glaucoma, ciliary body tumour or that had undergone various types of glaucoma filtration surgery and MIGS.
Prof Renard concluded by noting the device has limitations, which include a necessary learning curve and an inability to be used for dynamic examination to distinguish anterior synechiae from iridotrabecular apposition, but he reiterated its advantages, especially for the follow-up of the angle in glaucoma and exciting potential.
“We know that more precise and detailed analysis of the angle with the possibility of magnification offer the exciting possibility to study the relationships between angle closure and IOP and of the IOP curve and angle closure. More precise analysis of the new angular surgeries, and of the angular surgicals devices, also allows better understanding of its results and adverse events.”
Jean-Paul Renard: pr_renard@yahoo.fr