By MING WANG, MD, PHD
Summary: The Kamra corneal inlay is a minimally invasive surgery performed in the office with a laser. Candidates for the surgery can achieve improved reading vision and do most activities without the need for reading glasses. The AcuTarget HD is an instrument that measures the ocular wavefront to determine ideal candidates for the procedure.
Presbyopia refers to age-related loss of reading vision. It is a natural condition affecting all adults that starts around age 40. Reading glasses, prescription eyeglasses, and contact lenses are the main non-surgical treatments for this condition. The main surgical treatments have included LASIK to achieve monovision, where one eye is treated to see distance and one eye is treated to see near, or lens exchange, in which the natural lens is replaced with a specialized lens implant. Recently, advances have been made in the surgical treatment of presbyopia, and certain groups of patients can now benefit from minimally invasive laser surgery to improve reading vision.
One of these advances is the Kamra corneal inlay. It gained CE Mark approval in Europe in 2005 and FDA approval in the United States in April 2015. The Kamra corneal inlay is implanted in a brief in-office procedure.
A laser is used to create a small channel in the cornea, and the inlay is placed over the patient’s pupil. The Kamra corneal inlay is a small 3.8mm diameter ring made of polyvinylidene fluoride. The inlay has a 1.6mm diameter central aperture, which works to improve the depth of focus (or range of vision) in the implanted eye by restricting peripheral light rays. The result is that distance vision is maintained and reading vision is improved.
The Kamra procedure is designed for patients who have excellent distance vision and only need reading glasses. The Kamra is approved for use in patients 45 to 60 years of age who are not dependent on glasses or contact lenses for distance vision. For patients that do need distance correction, the procedure can sometimes be combined with other laser vision correction procedures such as LASIK. The Kamra corneal inlay is one of two corneal inlays currently approved in the United States. The Raindrop corneal inlay was also granted FDA approval in June 2016.
A specialized imaging device called the AcuTarget HD™ can be used to help identify candidates for corneal inlays. The AcuTarget is a double-pass wavefront diagnostic device that extracts light scatter pattern in a series of simple scans. The device objectively measures depth of focus, visual quality, tear film, and ocular landmarks without the need for subjective patient input.
By using this device, doctors are able to objectively measure a patient’s quality of vision. It can detect changes in the cornea and lens that can lead to blurry vision, such as early cataracts and corneal scars. It measures a patient’s tear quality over time, which can determine if dry eye is interfering with a patient’s visual quality. It identifies ocular landmarks that are used during surgery to guide precise inlay placement. It is also used after surgery to confirm that the inlay is placed in the optimal position.
By using this device, clinicians are able to identify optimal candidates for the Kamra corneal inlay procedure, as well as plan and execute the optimal placement of the inlay during the surgery. The result of a laser inlay surgery is a reduction in the need for reading glasses that eliminates many of the compromises that have existed with prior presbyopia surgeries such as loss of distance vision or the need for more invasive surgery.