Overview of Radial Keratotomy Correction
Refractive surgery is a type of laser surgery to change the way the eye focuses light. This can lessen a patient’s need to constantly wear glasses or contact lenses. Radial keratotomy (RK) is one type of refractive surgery that was very popular in the 20th century. In fact, around 10% of eye doctors in the U.S. have performed hundreds of thousands of RK surgeries.
RK was first proven effective by a doctor named Lans in the late 1800s. He showed that making deep cuts on the clear surface of the eye, called the cornea, made the center of the cornea flatter and the edges steeper. This helped improve vision. Later, a doctor named Sato also performed RK surgeries, but his method wasn’t as successful because it harmed the back surface of the cornea. As a result, as many as 70% of his patients ended up having serious eye problems like corneal swelling.
Better methods of RK that only involve making incisions on the front surface of the cornea were developed in Russia in the 1970s. During this time, doctors started using special formulas and charts that considered both the patient’s specifics and surgical factors. This improved the predictability of the surgery’s outcome. RK was introduced to the US in 1978 by several doctors who reported their findings and noted that there were very few complications. The National Institutes of Health then funded a study to evaluate the safety and effectiveness of RK.
With time, the RK surgery technique was further refined. Young patients often healed faster and needed more surgeries than older patients to get the same results. New tools, like diamond blades and ultrasonic pachymeters, were also developed to make the surgery even more predictable.
Over time, however, RK’s popularity has decreased due to the introduction of other more precise and stable types of refractive surgery. This includes surgeries like photorefractive keratectomy (PRK), Laser In Situ Keratomileusis (LASIK), small incision lenticule extraction (SMILE), and lens replacement surgery. Despite this, our knowledge of RK is still very important as it allowed us to treat many patients who may need to have the procedure revised or revisited to improve their vision later in life.
Anatomy and Physiology of Radial Keratotomy Correction
The eye works a bit like a camera, with the cornea (the clear front surface of the eye) and the lens helping to focus light onto the retina (the light-sensitive tissue at the back of the eye). In a perfectly sighted eye, these parts of the eye work together so that light rays coming in from a distance are focused exactly on the retina, creating a clear picture. However, in some eyes, which are either too long or too short, or if there is an irregularity in the shape of the eye (astigmatism), the light isn’t focused correctly and the picture isn’t clear.
The cornea is a clear structure on the front of the eye that has no blood vessels. It’s curved, measures about 11.5 mm across, and is thicker around the edges than in the middle. The cornea has nerves that come from a larger nerve in your head called the trigeminal nerve. The cornea has different layers, including the epithelium (the outermost layer), Bowman’s layer, stroma (the largest layer that gives the cornea strength), pre-Descemet’s layer (also known as Dua’s layer), Descemet’s layer, and endothelium (the innermost layer).
The epithelium acts as the main protector of our eyes, and tears create an optically smooth surface. When this layer gets damaged, for example, when a corneal abrasion occurs, stem cells from the edge (periphery) of the cornea grow (proliferate) and move in to fix the damage.
Bowman’s layer is the part of the cornea right below the epithelium and it is mostly made of tightly packed type I collagen fibres. Below that, the stroma layer provides stability and consists of collagen fibres, cells called keratocytes, and compounds called glycosaminoglycans that are packed together. When eye surgeries that involve making cuts in the cornea (incisional surgeries like RK) are done, they can disrupt this layer and permanently weaken the cornea.
Descemet’s layer, another part of the cornea, is layered and gets thicker as a person ages. Lastly, the corneal endothelium, a single layer of cells at the back of the cornea, is responsible for maintaining the correct amount of fluid in the cornea, which prevents the cornea from swelling (edema) and becoming unclear (losing transparency). This layer can’t regenerate, and its cell count typically decreases as a person ages.
In a surgery called radial keratotomy, doctors change how the front of the cornea bends light to correct blurry vision. This is done by creating several deep cuts into the stroma, which is most of the thickness of the cornea. Various factors such as the length, depth, and number of cuts, as well as the patient’s sex and age, can affect the success of the surgery.
Why do People Need Radial Keratotomy Correction
Radial keratotomy is a type of surgery that can correct moderate nearsightedness, which is a condition also known as moderate myopia. This procedure can be of benefit to you if you are at least 18 years old. This age requirement is in place because your vision prescription needs to be stable for the surgery to be effective and safe, and because you need to be old enough to understand and agree to the surgery (a process called informed consent).
If you wear contact lenses, you will need to stop wearing them for a while before the surgery. This is because contacts can change the shape of your eyes, and your doctor needs to get accurate measurements of your eyes’ natural shape. This process involves getting several repeated corneal topography scans, which provide a detailed map of the surface of your eye, and cycloplegic refractions, which measure your eye’s ability to focus light properly.
The purpose of these tests is to ensure that your vision prescription is not changing, which is known as refractive stability. Once these conditions are met, you can move forward with the surgery.
When a Person Should Avoid Radial Keratotomy Correction
There are certain conditions that can make radial keratotomy, a type of eye surgery to correct vision, risky or unsuitable. These include:
– If your vision has changed a lot within the past year (changes greater than 0.5 Diopters), it’s not advised.
– Certain health conditions, like pregnancy and uncontrolled diabetes, can also lead to unstable vision.
– Other medical conditions such as lupus, Sjögren’s syndrome, Graves’ disease, rheumatoid arthritis, and inflammatory bowel disease can affect the eye and slow healing after surgery.
– If you have a weak or thin cornea, or if you have a disease called keratoconus where the cornea is shaped like a cone, the surgery might weaken your cornea even more and lead to a condition called cornea ectasia.
– If you have an active infection or inflammation in your eye, surgery can actually make it worse.
There are also some conditions that might make this surgery less effective or more risky, but not necessarily impossible:
– Elderly people who are starting to develop cataracts might not see much improvement from the surgery. Instead, they might do better with cataract surgery.
– If your cornea has any scarring, or if you have corneal dystrophy or herpetic eye disease, it might be harder to improve your vision with this surgery, and there’s a greater risk of losing vision.
– If your pupils tend to be larger, especially in low light, you could have more side effects after surgery, such as seeing halos or glare.
– For patients with glaucoma (a disease that increases pressure in the eye), this surgery could make it harder to monitor and control the pressure in the eye.
Equipment used for Radial Keratotomy Correction
To carry out a procedure known as radial keratotomy, your doctor will need several items. These include eye drops that numb the eye (known as topical anesthetic drops), a special kind of ink called gentian ink that is used to make marks on the cornea (the clear front surface of your eye), and special tools called an optical zone marker and a corneal incision marker.
The doctor will also use an ultrasonic pachymeter, which is a device that measures the thickness of your cornea. One of the main tools needed is a unique knife made from diamond known as a gem-quality diamond blade knife with a 45-degree cutting angle. This knife is used to make precise cuts on the cornea.
Finally, antibiotic eye drops are necessary to prevent infection after the procedure, and steroid eye drops help to reduce inflammation and assist the healing process.
Who is needed to perform Radial Keratotomy Correction?
A radial keratotomy, which is a surgical procedure for the eyes, involves a broad range of medical professionals. An eye surgeon, or ophthalmic surgeon, is the main individual who will perform the procedure. They are supported by optometrists, who are eye care specialists that can help evaluate and manage your eye health.
There are also ophthalmic nurses or assistants who help the surgeon during the procedure, and theater staff who assist in preparing the surgical space. Orthoptists, professionals who specialize in eye movement disorders, may be involved in your care as well. Imaging technicians are responsible for any pictures or scans that need to be taken of your eye.
Finally, medical assistants are present to help make sure everything runs smoothly before, during, and after your surgery. Each person on this team plays a crucial role in ensuring that your eye surgery goes as planned and that you receive the best care possible.
Preparing for Radial Keratotomy Correction
Before undergoing eye surgery, it’s important that doctors gather a detailed medical history and do a thorough physical examination to ensure there’s no reason the surgery can’t occur, known as contraindications. They also need to understand your job and what you hope to achieve from having the surgery.
One of the vital steps when preparing for eye surgery includes inspecting the eye’s surface using a device called a Slit-Lamp. This device helps doctors to check for dry eyes, measure the pressure inside your eye, evaluate the health of your cornea (the clear, front surface of your eye), determine if you have any cataracts (cloudy patches in the lens of your eye), and have a comprehensive look at the back of your eye after dilation (widening of your pupils).
If you wear contact lenses, you should cease wearing them 1 to 2 weeks before having images taken of your cornea. This pause aids in getting accurate measurements. It’s standard for doctors to assess your cornea using keratometry (which measures the curve of the cornea), topography (a technique for mapping the surface of the cornea), and ultrasound pachymetry (thickness measurements of your cornea) leading up to your surgery.
How is Radial Keratotomy Correction performed
Before your eye surgery, we ensure all equipment is safe and double-check your data to lower any chances of mistakes. We also make sure to obtain your written consent which is typically done before the surgery day. This way you will have time to discuss any questions or concerns you may have.
The surgery in question is called radial keratotomy, and it might sound complex, but it includes these quite approachable steps:
- Applying the right anesthesia (medicine to stop pain)
- Marking the path for the incisions (cuts) on your eye
- Measuring the thickness of your cornea (the clear front surface of your eye)
- Adjusting the depth of the surgical knife
- Making the cuts on the cornea
- Applying antibiotic eye drops after the surgery
We use an anesthesia that’s applied directly to your eye so as not to interfere with your eye movement during the surgery. The size of the clear area at the center of your eye, which we’ll be working on, depends on what your surgeon thinks is best. We measure how thick your cornea is in four different quadrants from the clear area of your eye that we marked earlier. Based on this measurement, we adjust the depth of the surgical knife. We generally make up to 8 cuts, but this can vary depending upon your level of nearsightedness. If you still have vision issues after the surgery, we can consider making more cuts. The specific way we make these cuts – including where we start, the direction, depth, and length – can be altered as needed to get the best results and maintain good long-term vision stability.
Unlike past procedures, today we routinely use eye drops after the radial keratotomy to prevent infection. At times, we use steroids to help influence how your wounds heal. If your eyes feel dry after surgery, we can prescribe eye drops to make them feel more comfortable. It’s worth noting that maintaining consistent vision long term can be a challenge after this surgery, so you’ll need to check in with your doctor regularly.
A different kind of surgery called astigmatic keratotomy (AK) might be used if you have a different eye condition called astigmatism. Similarly to the main procedure, this involves making deep cuts in your cornea. The result typically is that the part where the cut was made becomes flatter, while the opposite area becomes steeper. The cuts are made about 95% deep in the middle part of the cornea, and this procedure can also be used after other types of eye surgeries.
If you’re having cataract surgery and you also have astigmatism, another procedure, known as limbal relaxing incisions (LRIs), can be used. These cuts are made slightly shallow than the thinnest part of your cornea near your iris (the colored part of your eye). Cuts for these specialized surgeries are usually made using a laser for better precision.
Possible Complications of Radial Keratotomy Correction
Radial Keratotomy (RK), a type of eye surgery, may be associated with potential complications that can affect your vision. Serious, or ‘sight-threatening’, complications are quite rare, affecting 1% to 3% of patients. In these cases, people can suffer from serious infections, such as bacterial and fungal keratitis and endophthalitis. If the incisions made during the surgery are too deep, it could lead to additional issues like trauma, development of cataracts, and bleeding.
Sometimes, the cuts made during the surgery can cause the structure of the eye to weaken. This reduction in stability could potentially lead to the globe (the outer wall of the eye) bursting along the surgery scars. In a study, it was observed that 3% of patients lost some visual acuity, which is a measure of sharpness of vision.
There are also ‘non-sight-threatening’ complications, which do not pose a serious risk to your vision but can still be bothersome. For instance, some patients may experience dry eyes after surgery due to lesser tear production. The cuts made during the surgery may damage the nerves responsible for triggering tear production.
Other visual disturbances, such as seeing halos or glare around lights, hazy vision, and decreased ability to distinguish contrast, might occur after the surgery. These vision problems often relate to the changes in the eye from the surgery and can increase if the pupils become larger.
Long term observation of patients who have gone through Radial Keratotomy revealed something known as “hyperopic regression”. Basically, it’s when the person’s vision starts to return back to what it was before the surgery, 10 years after the operation. Also, around 22% of patients experienced a shift toward hyperopia (farsightedness), and 2% shifted toward myopia (nearsightedness) within 5 years after the surgery. A few patients experienced changes in visual sharpness, the eye’s ability to refract or bend light, and the distinct physical characteristics of the eye 10 years after surgery.
What Else Should I Know About Radial Keratotomy Correction?
If you’ve had a radial keratotomy (a surgery to correct nearsightedness), it’s possible that you could experience complications that could affect your vision, both immediately after the surgery and in the long term. These complications could include changes in the quality of your vision throughout the day and a slow return to being farsighted. You could also start to develop presbyopia (a condition where your eyes lose the ability to focus on nearby objects) and cataracts (cloudiness in the lens of the eye), which could make it even harder for you to see clearly.
Doctors have come up with ways to help improve the power measurements in the artificial lens (intraocular lens) that could be used to help restore vision after radial keratotomy. More recently, doctors have also started to use more specialized versions of radial keratotomy to help treat keratoconus (a condition that causes the cornea, the clear front part of the eye, to become thin and bulge outward).
When thinking about these kinds of surgeries, it’s important to consider factors such as the overall strength and stability of the cornea that can affect the measurements, the presence of irregular astigmatism (a condition that makes your vision blurry), the size of the optic zone (the part of the lens that light passes through), and the location of the incisions. If the cornea is significantly unstable, irregular, or has scars, you may need an initial treatment of collagen crosslinking (a treatment that strengthens the cornea) with or without a type of laser surgery known as therapeutic excimer laser ablation (used to remove scars), in order to help get more accurate measurements.