NEW KERATOCONUS TREATMENT AUSTRALIA: CAIRS - CORNEAL ALLOGENIC INTRASTROMAL RING SEGMENTS
The first Corneal Allogenic Intrastromal Ring Segment (CAIRS) surgery in Australia was performed at the Queensland Eye Institute in May 2021 by Dr David Gunn, paving the way to better sight for many sufferers of the relatively common condition called keratoconus.
KERATOCONUS CAUSES LOSS OF VISION
Keratoconus is a disease of the cornea - the clear circular window at the front of the eye. The cornea normally has a regular spherical shape like a soccer ball. In keratoconus the cornea degenerates and becomes shaped more like a cone. This causes blurred and distorted vision. In the early stages of keratoconus an optometrist can fit glasses or contact lenses to help. Corneal cross linking is used to stop the disease from getting worse but has a very limited effect on improving the vision. Read more about Keratoconus.
HOW CAN THE VISION BE IMPROVED?
Once contact lenses are no longer helping or are not tolerated, there are procedures that can improve the shape of the cornea and vision. For mild disease, sculpting the cornea with laser improves the shape (1). However, this technique removes tissue and in more advanced disease would need to remove too much to be safe. Another technique first introduced in the late 1990’s, is to implant support rings called “ring segments” into a channel formed with a laser. These ring segments flatten and regularise the central part of the cornea which improves vision. This procedure is called Intracorneal Ring Segments or ICRS.
HOW EFFECTIVE ARE CORNEAL RING SEGMENTS?
Intracorneal ring segments have been shown to be highly effective in numerous studies, particularly in moderate keratoconus, reducing the number of patients that need full corneal graft surgery (2). The benefit of an implant is that it is removable. The real world results can be variable however and many patients will need enhancement of the result with laser resurfacing. Most patients will still require glasses to see well after surgery.
WHAT IS CAIRS?
Corneal Allogenic Intrastromal Ring Segments or “CAIRS” is the next progression of intracorneal ring segment surgery and was first described in 2017 (3). The procedure begins with harvesting a ring of corneal tissue from a donor graft. Channels are then formed in the patient’s cornea with a laser and the stromal ring segments are then threaded into the channels.
BENEFITS OF CAIRS
Human donor cornea tissue has a large number of benefits over plastic implants.
Biocompatibility
The main benefit of using corneal tissue is that it is a “like into like” implant. Acrylic material in the cornea is detected by the body as foreign material and leads to reactions that may lead to scarring.
Stability
Acrylic implants can migrate over time, particularly if patients continue to rub their eyes. If the ring is placed too shallow, the overlying cornea can melt and the implant can erode out onto the surface. This can be complicated by infection. CAIRS does not seem to have this risk as the corneal tissue is better integrated and remains stable.
Greater Effect
Acrylic ring segments are implanted at a depth of 80-85% due to the risk of extrusion. The downside of this deep placement is that they have less effect on the resulting shape on the front surface. CAIRS can be implanted at a shallower depth of 50% which can give a greater effect on the surface.
Larger Range of Candidates
Due to less concern of extrusion, patients with more severe disease and thinner corneas can have CAIRS who would not be candidates for ICRS. Previously the only option for these patients would have been a more invasive full corneal graft.
Greater Customisation
As the surgeon creates the implants with a laser, there is complete control over the dimensions of the implants. These can be customised to the patient’s needs.
Anterior segment scan comparison of Keraring above and CAIRS below. The CAIRS implant has integrated well to the host cornea without the risk of extrusion.
WHO IS A CANDIDATE FOR CAIRS?
Patients with keratoconus or other corneal conditions who have poor vision in glasses and are intolerant of contact lenses. In very advanced disease with corneal scar, traditional corneal transplant is the only option to improve vision.
COMMON PATIENT QUESTIONS
What is the CAIRS procedure experience like?
The procedure is performed under topical anaesthetic and twilight sedation which means your eye will be made numb with eye drops and you will sleep through most of the procedure. The procedure itself is painless and takes less than half an hour. Most patients do not remember having the procedure at all. Your eye will be a little scratchy for a day or two as the surface of the eye heals. You will need eye drops for a month after surgery. There is no requirement for long term steroid drops like would be required for a conventional corneal graft.
What will my vision be like after the surgery?
Some patients notice a big improvement quickly, while others do not. The response depends on how bad your vision is to begin with. At 3 months after surgery, the effect of the ring segments should be mostly stable and a new glasses prescription can be obtained. This is when most patients notice their improvement. Most patients still need glasses, but their prescription is reduced and the quality of vision in glasses is much better than before. Most patients with keratoconus have poor quality night vision with haloes and streaks from lights. Plastic intracorneal ring segments often make this worse, this doesn’t seem to be the case with CAIRS where Dr Gunn has seen no change or often an improvement in the night vision.
Is CAIRS the only procedure I will need?
For most, CAIRS is the first step in their visual rehabilitation. It will often be followed by cross linking on the same or a separate day a few weeks later. Dr Gunn prefers to separate the CAIRS and cross linking by at least a few weeks, but if you are travelling interstate for the procedure they can be performed on the same day for convenience. Following this topographic laser resurfacing 6-12 months later may be used to enhance the result.
I have already had cross linking, can I still have CAIRS?
Yes. CAIRS is still effective after corneal cross linking. There isnt any published data about outcomes in this group currently. Dr Gunn’s impression is that it may be a little less effective however and his preference is to perform CAIRS first if possible.
How long do I need off work / driving
The procedure is normally performed on a Thursday and you can be back at work on Monday. There is minimal pain during recovery. If cross linking is performed at the same time then recovery can be a little longer and Dr Gunn would recommend a week off.
Can I fly to Brisbane for the procedure?
Yes, currently Queensland Eye Institute is the only clinic in Australia offering this procedure to our knowledge. Dr Gunn is happy to see patients from around Australia and the Pacific for the procedure. Many patients travel to the Queensland Eye Institute for private eye care. There are hotels located right near the building that houses both the QEI clinic and South Bank Day Hospital. Two visits to Brisbane are required - once for your assessment and to order donor corneal tissue, followed by a second trip for the surgery at least 4-8 weeks later. The operation can be performed on a Friday at Southbank Day Hospital and you will be seen on the following Tuesday. After that appointment you can fly home and return to work. We prefer to review patients at 1 month and 3 months, thought the one month visit can be sometimes be done locally.
Can I do a telemedicine consult with Dr Gunn?
As of 2023 Dr Gunn is happy to do the initial assessment appointment via a telemedicine consultation to save patients from flying back and forth to Brisbane. To organise this appointment you will need to provide the below:
A referral letter to Dr Gunn from your optometrist or ophthalmologist
Your current uncorrected visual acuity (no glasses or contact lenses) and corrected visual acuity (with your glasses and or contact lenses on) and your subjective refraction (your glasses prescription numbers from the optometrist or ophthalmologist)
A recent tomography scan of both your eyes - Pentacam preferred.
How much does CAIRS cost?
Private health insurance with bronze level hospital cover or above will cover most of the cost of the procedure. Basic hospital or extras only cover does not cover eye surgery. Without insurance it is possible to self fund the procedure though there will be significant expense due to funding the corneal graft material. You can contact the Queensland Eye Institute for an estimate of costs, though these will not be confirmed until you see Dr Gunn to finalise your treatment plan.
WHAT ARE THE RISKS OF CAIRS?
CAIRS is an evolution of intracorneal ring segment surgery and so likely shares many of the same risks - a small chance of infection, scarring, haze, reduction in vision. It seems from experience from major centres that these risks are much lower in CAIRS than with ICRS. The main issue with CAIRS is that as it is a newer procedure, there is currently a lack of large scale long term published results. That said, 12 month outcomes have been reported and they are excellent (3). Thankfully the procedure shares much with traditional intracorneal ring segment surgery that is already a well established treatment used worldwide.
Dr David Gunn Eye Surgery Brisbane Queensland Eye Institute
FURTHER INFORMATION
Read more about Keratoconus here
Summary video of the CAIRS development 2017
1. Kanellopoulos AJ. Ten-Year Outcomes of Progressive Keratoconus Management With the Athens Protocol (Topography-Guided Partial-Refraction PRK Combined With CXL). J Refract Surg. 2019 Aug 1;35(8):478-483. doi: 10.3928/1081597X-20190627-01. PMID: 31393985.
2. Vega-Estrada, A., Alio, J.L. The use of intracorneal ring segments in keratoconus. Eye and Vis 3, 8 (2016). https://doi.org/10.1186/s40662-016-0040-z
3. Jacob S et al. Corneal Allogenic Intrastromal Ring Segments (CAIRS) Combined With Corneal Cross-linking for Keratoconus. J Refract Surg. 2018 May 1;34(5):296-303. doi: 10.3928/1081597X-20180223-01. PMID: 29738584. https://pubmed.ncbi.nlm.nih.gov/29738584/