Intra Corneal Rings
This is a mechanical treatment for keratoconus correction and shortsightedness (myopia), called INTACS (intra corneal ring segments). INTACS create a whole new category of vision correction, without having to wear glasses or contact lenses.
WHAT ARE INTACS?
INTACS are made of Polymethyl-methacrylate (PMMA), a biocompatible material which has been used safely in intraocular lenses during cataract surgery and also for hardcontact lenses, for over 50 years.
Two ultra-thin, clear, precision-engineered crescents, each with an arc length of 150 degrees, are placed in the periphery of the cornea of the eye to correct the corneal shape. Placed outside of the central optical zone, INTACS are designed to reshape the corneal curvature without cutting or removing tissue from the optical zone of the cornea
INTACS cornea ring segments
The rings are very small, and practically invisible. They are designed to be permanent, although can be replaced or removed in case you need a different correction, or simply change your mind to having them removed.
HOW DO INTACS WORK?
The condition, myopia, has to do with the shape of the eye. In order to see images, light rays pass through the clear cornea, through the pupil, and focuses on the retina.
The cornea is responsible for 75% of the focusing of light. In a myopic eye, the curve of the cornea is too steep, therefore light focuses in front of the retina, causing the images of far away objects to be blurred.
INTACS are placed midstromal into the cornea, but outside the central optical zone, (a 3-4mm diameter area in the centre of the cornea through which light rays pass) which is crucial for crisp, clear vision.
INTACS are unique in the fact that they reshape the cornea mechanically by adding material to the eye instead of cutting or removing tissue like other surgical vision correction procedures. They flatten the myopic cornea so that light rays are correctly focused onto the retina, thereby eliminating the need for glasses or contact lenses.
HOW ARE INTACS INSERTED?
The first INTACS segment placed in the tunnel The dashed line indicates corneal flattening.
The procedure takes about 15 minutes and is performed on an outpatient basis. Patients are given a mild sedative and eye drops to anaesthetise or numb the eye. A tiny opening, less than 2mm, is made near the upper edge of the cornea near the eyelid with a diamond knife. INTACS are inserted through this opening to rest between the layers of tissue in the cornea, outside the central optical zone. The incision is closed with one nylon stitch, which is removed after one week.
The eye will then be patched and the patient is discharged immediately after surgery. No pain is experienced during the procedure. Some patients mentioned that they only had mild discomfort during surgery.
LIFE AFTER INTACS SURGERY…
A significantly improved vision from the first day postoperatively, is notable by majority of the patients. Normal activities are resumed within 2 or 3 days after surgery. Eye drops are used for about 1 week after the surgical procedure. INTACS cannot be felt when blinking because they are placed within the cornea beneath the nerve endings.
Most patients have 20/25 vision or better visual acuity 2 months postoperatively. Very little regression, if any is experienced after surgery.
The refractive outcome of INTACS is predictable, and very rewarding for patient as well as surgeon. In the U.S. clinical trials 97% of patients achieved 20/40 or better vision (criteria of obtaining a driver’s license), 74% of patients achieved 20/20 or better vision (normal or 100% vision), 53% of patients achieved 20/16 or better vision (excellent vision) at their year-end examinations.
Clinical trials also revealed that 97% or more of the eyes treated demonstrated stability of refractive effect within 1.00D of their previous test for intervals from 3 months to 2 years after the procedure. Thus, INTACS provide a stable refractive correction over time.
Extensive clinical trials in the U.S. have shown that infection, which is a risk in any surgical procedure, occurred in less than 0.5% with INTACS surgery. In these cases, where INTACS were removed, the patients returned to the level of corrected vision they had prior to the procedure. Some patients experienced visual symptoms after the procedure, such as difficulty with night vision, glare, blurry vision, halos, double vision and fluctuating distance vision. If the results of the procedure are not satisfactory, you may need to exchange you INTACS for another size or have them removed, and vision will, in most cases, return to the preoperative refraction.
INTACS is an option for myopic people, 18 years and older and people with keratoconus.
Patients who have had previous laser refractive surgery, and have residual myopia are able to have INTACS corneal ring implanted in order to eliminate the residual myopia, and additionally stabilises the cornea to prevent further myopic regression. Even patients with keratoconus are good candidates for INTACS since the corneal ring will create a symmetric cornea and also stabilise their corneas. This is in contrast with other refractive surgeries that may temporarily eliminate the refractive error, but further thins out the cornea, which causes destabilisation and potential regression or unstable refractive errors.
Although stable refractive errors are recommended prior to the INTACS procedure, because the ring is removable and replaceable, natural regression may be corrected by substituting a thinner ring with a thicker ring, which will correct a higher refractive error if regression is taking place.
With the new solid state intralase machines, the tunnel for intacs can be made more accurately and therefore would make this a better procedure.