Keratoconus is an eye disease characterized by thinning of the cornea and forward bending over time. Keratoconus, which causes deterioration of the perfect shape of the cornea and accordingly vision problems; It has symptoms such as blurred vision, light sensitivity, redness of the eye and the need for glasses. This corneal disease, which usually progresses over years, can worsen rapidly in some people. Keratoconus is a disease whose progression can be slowed or stopped rather than curable.
After giving general information about keratoconus, “What is keratoconus?”, “What are the symptoms of keratoconus?” and “How to treat keratoconus?” I will explain the answers to your questions. First of all, I would like to give a brief information about the structure and functions of the cornea in order to understand keratoconus disease more clearly.
The cornea, which has the ability to filter ultraviolet rays from the sun, is a dome-shaped transparent layer located outside the eye. The cornea has two important functions due to its tissue and position in the eye anatomy. In a healthy eye, the cornea properly focuses the incoming light on the retina and also protects the eye against external factors. Since the cornea has vital functions, any problem that occurs in this layer significantly affects the vision of the person. Keratoconus is a disease that occurs as a result of structural changes in the cornea.
What is Keratoconus?
As I mentioned in the introduction to my article, keratoconus is an eye disease that causes thinning of the cornea and a dome-shaped protrusion towards the front of the eye. Keratoconus, which is a non-inflammatory and progressive disease, usually progresses over years. The eyes of people with keratoconus can be affected in many different ways. The latest research reveals that the incidence of keratoconus is much higher today than in the past. While keratoconus was seen in one of 2000 people in the past, today this rate has increased 400 times. Unfortunately, the reason for the increase in the incidence of keratoconus is not yet known. One possibility is that the disease is now better known by doctors and that the testing equipment is developed may be among the factors affecting the increase in the number of patients diagnosed with keratoconus.
Since keratoconus causes irregularities in the shape of the cornea, the clarity of vision of the patients decreases, their sensitivity to light increases, and these complaints increase significantly as the disease progresses.
What Causes Keratoconus?
“What causes keratoconus disease?” There is no definite answer to the question yet, so it becomes a more accurate option to examine the risk factors rather than the causes of the disease.
Protein fibers called collagen in our eyes are responsible for maintaining the perfect shape of the cornea.
If the tissue of the fibers deteriorates and begins to weaken, the functions of protecting the shape of the cornea decrease. There is an important correlation between the reduction of antioxidants that protect the cornea and the weakening of collagen fibers. As the antioxidants decrease and the strength of the fibers in the cornea weakens, it becomes more difficult to maintain the shape of the cornea. Therefore, I can state that oxidative stress is an important risk factor for keratoconus.
It is accepted that there is a relationship between keratoconus disease and family history. For this reason, it is recommended that those with a family history of keratoconus have regular eye examinations.
Keratoconus usually occurs during adolescence, but in some people it can be seen in childhood or after the age of 30. The shape of the cornea can deteriorate in a short time or over years. Various complaints occur related to the changes in the shape of the cornea, such as gradually decreasing and blurring of the patient’s vision, flashes of light and a continuous increase in the number of glasses.
One of the most important features of keratoconus disease is the unpredictability of the progression of the disease. Both eyes of people with keratoconus will be affected by this disease, albeit to a different degree. In severe cases of keratoconus, corneal scarring may occur due to excessive stretching of collagen fibers.
What Are the Symptoms of Keratoconus?
The symptoms of keratoconus may differ according to the course of the disease, from person to person, and even in both eyes. It cannot be said that all symptoms will occur at the same level in every patient. Since the symptoms and complaints change as the disease progresses, I will consider the symptoms of keratoconus in two different ways: early keratoconus symptoms and future keratoconus symptoms.
– Early Keratoconus Symptoms
In cases where keratoconus has not progressed very far, it causes symptoms such as a slight blurring of vision, distorted and wavy vision when looking at lines, increased light sensitivity and light flashing.
– Keratoconus Symptoms in the Future Period
Keratoconus generally has a progressive profile over the years. In the advanced stage, the most common symptoms of keratoconus include significant blurring and deterioration in vision, a continuous increase in the degrees of refractive disorders (myopia or astigmatism), and the inability to wear contact lenses due to irregularity of the corneal shape.
I would like to say that people who experience the symptoms of keratoconus should not ignore these problems and should consult their ophthalmologist without wasting time. As the disease progresses, vision problems that cannot be straighten with glasses or contact lenses may occur due to the progressive deterioration of the shape of the cornea. In addition, untreated keratoconus disease can also cause corneal injury.
Keratoconus Diagnosis and Treatment
It is possible to diagnose keratoconus with a routine eye examination. During the examination, ophthalmologists listen to the complaints of the patients, evaluate the shape of the cornea and whether there is a curvature in the cornea. For the definitive diagnosis of the disease, corneal topography is requested. With the corneal topography, which gives detailed information about the tissue of the patient’s cornea, the diameter, refractive power, thickness, anterior camera depth and surface curvatures of the cornea are determined.
Based on the data, treatment of keratoconus is initiated. Keratoconus treatment should be planned according to the patient’s symptoms and the degree of corneal curvature. The period in which the symptoms are infrequent will not be the same as the treatments that should be applied in the future.
Keratoconus treatment usually starts with glasses treatment. In unease cases, glasses will be sufficient to provide clearing of the blurred vision of the patients. However, as the disease progresses, glasses alone begin to be unsufficent to provide good enough vision.
In this situation, gas-permeable rigid or scleral contact lenses may be recommended. These special lenses are very effective in increasing the clarity of vision by eliminating the dome of the cornea. However, as the disease continues to progress, the use of lenses will be insufficient. In this case, the patient’s health status should be evaluated and CCL treatment, also called CXL, or intracorneal ring treatment should be planned.
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Contact Lenses for Keratoconus Treatment
Glasses or Soft Contact Lenses: Glasses or soft contact lens treatment is activated in the early stages of keratoconus disease. The aim of this treatment is to clarify the blurred and distorted vision of the person. As the cornea shape changes, glasses and contact lens numbers also need to be changed.
Hard Contact Lenses: Gas permeable hard contact lenses are preferred for patients who cannot be treated with glasses or soft lenses and whose disease progresses. Hard contact lenses may cause discomfort in the initial phase, but over time, patients will get used to these lenses.
Piggyback Contact Lens: Patients who cannot adapt to gas-permeable hard lenses and have decreased comfort can apply gas-permeable hard lenses on soft lenses. Piggyback contact lenses can make a significant difference in the treatment of keratoconus when both lenses have high gas permeability.
Scleral Contact Lenses: Scleral contact lenses can be used in patients with high myopia and astigmatism and irregularities in the corneal topography. These lenses have the feature of covering a larger part of the cornea compared to gas permeable hard lenses. They can be easily removed and worn, offer comfort close to soft lenses and can be used in all stages of keratoconus.
Hybrid Contact Lenses: Contact lenses in which the optical center is made of hard material and the periphery of it is made of soft material, are called hybrid lenses. It is widely preferred.
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Corneal Cross-Linking (CCL) Applications in Keratoconus Treatment
Corneal Cross-Linking is the only effective treatment method performed all over the world to stop the progression of keratoconus disease or slow down the rate of progression of the disease. The treatment is to strengthen the weakened collagen fibers in keratoconus patients, which are responsible for keeping the corneal shape stable. In addition to being the only treatment that can stop the worsening of progressive keratoconus, CXL treatment may also decrease the probability of resorting to corneal transplants.
However, in order to apply this treatment method, the corneal thickness of the patients should not be less than 400 microns. For this reason, before the treatment planning is made, the corneal thickness of the patients should be measured and the corneal topography should be taken.
In the CCL application, first anesthetic drops are applied to the eyes, and then eye drops containing vitamin B2 (riboflavin) are applied to enable the cornea of the patients to absorb light better. It takes approximately 30 minutes for the vitamin-containing drop to be absorbed by the cornea. In the last stage of the treatment, UV light of a certain wavelength is applied to the eye. CCL application is also divided into two different types in itself.
Epi-Off Technique: In this technique, the corneal epithelium is peeled before dripping drops containing vitamin B2. After the epithelium is removed, a solution containing vitamin B2 is dripped into the eye, and after the drop is absorbed, ultraviolet radiation is given to the cornea. Then, a protective contact lens is placed on the patient’s eye.
Epi-On Technique: Epi-On method is mostly preferred in patients with insufficient corneal thickness. Unlike the Epi-Off technique, the epithelium of the cornea is not peeled off in the Epi-On technique. All operations are performed on the epithelial layer. The steps we mentioned in the CXL application are also applied in the CXL Epi – On technique.
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Ring Applications in Keratoconus Treatment
The thickness and length of the inner corneal rings, which consist of micro-sized, transparent and half-moon-shaped pieces, vary according to the amount of diopters that need to be shaped. In patients who do not want to use contact lenses or who cannot use contact lenses due to the shape of the cornea, intracorneal ring application may provide successful results if keratoconus did not went bad.
With the developing technologies, intraocular ring application can be performed in a few minutes. The treatment, which is based on the creation of channels in the cornea with a femtosecond laser and the placement of the rings in these channels, is completed in a short time of approximately 2 minutes for each eye.
Another alternative in the treatment of keratoconus is corneal transplantation. However, the need for this treatment method has now decreased. Moreover, the high risk of tissue rejection after corneal transplantation, such as 15-20%, reduces the frequency of corneal transplantation.