Device improves irregular astigmatism in pseudophakic eyes

Take-home message: A pinhole implant placed in the ciliary sulcus can improve visual acuity and reduce dysphotic symptoms in pseudophakic eyes with irregular corneal astigmatism. Implantation is even easier with the latest version of the investigational device

By Cheryl Guttman Krader; Reviewed by Claudio C. Trindade, MD

Belo Horizonte, Brazil-Ciliary sulcus implantation of a pinhole intraocular implant is showing promise as a safe and effective method for treating irregular corneal astigmatism in pseudophakic eyes, according to Claudio C. Trindade, MD, its inventor.

The device is currently investigational and is being developed by Morcher. As of April 2015, Dr. Trindade had implanted the device, which is now in its third iteration, into 17 eyes that had a mean follow-up of 14 months.

Irregular astigmatism in these cases was associated with previous penetrating keratoplasty in 6 eyes, prior radial keratotomy in 5 eyes, and keratoconus in 6 eyes. All eyes benefited with improvement in visual acuity and reduction of dysphotopic symptoms.

So far, the device has remained well-centered with good clearance from the primary IOL, and there have not been any complications, noted Dr. Trindade, private practice, Cancado-Trindade Eye Institute, Belo Horizonte, Brazil, and a PhD Program member, University of Sao Paulo, Brazil

“A pinhole aperture minimizes the negative impact of corneal optical aberrations on image resolution by excluding peripheral ocular light rays, and it is well-known for its benefit of improving vision in eyes with irregular corneal astigmatism. The idea of implanting a pinhole device in the ciliary sulcus is based on the idea that the more physiological place for a small aperture device is close to the pupillary plane and takes into account the long track record of safety of piggyback IOLs,” he said.

“Results from bench testing of this device at an optical engineering laboratory showed it caused a remarkable reduction of total aberrations, and clinical experience with it so far has been positive. Now longer follow-up in more eyes is needed.”

The implant

The pinhole implant is constructed of a proprietary black hydrophobic acrylic material that blocks visible light, but is transparent to infrared light. Therefore, retinal examination is still possible with devices that use infrared light, such as optical coherence tomography and scanning laser ophthalmoscopy. The reduction in retinal luminance is counterbalanced by the improvement of dysphotopic symptoms.

According to Dr. Trindade, the implant does not constrict the visual field.

“Because of the proximity to the iris plane, there is no important impact on the visual field. There were some slight changes in retinal sensitivity, but they were clinically irrelevant,” Dr. Trindade said.

Design modifications

The implant “optic” has a concave-convex shape that was chosen to avoid any contact with the primary IOL. The first intraocular pinhole implant featured three closed loop haptics, and that design was chosen to ensure centration and stability within the ciliary sulcus. In order to avoid iris chafing and uveitis-glaucoma-hyphema syndrome, the haptics are angulated (10°) and were made thin (350 μm), round, and well-polished.

The latest generation version of the implant features two open loop haptics that are 250 μm thick.

“This foldable device is easily implanted through a 2.2-mm incision, and the redesign of the haptics facilitates implantation and further minimizes contact with the sulcus,” Dr. Trindade said.

Since the open loop haptics deflect more in the sulcus, the overall length of the implant was increased from 13.5 to 14.0 mm to assure proper sulcus stabilization. The current version of the implant also features a smaller pinhole size (1.3 versus 1.5 mm), which Dr. Trindade said provides a better balance between retinal luminance and visual acuity/reduction of corneal aberrations.

Claudio C. Trindade, MD

E: claudio.trindade@me.com

This article was adapted from Dr. Trindade’s presentation during the 2015 meeting of the American Society of Cataract and Refractive Surgery. Dr. Trindade holds a patent on the device and has a royalty agreement with Morcher.