What is Keratoconus?
Keratoconus is a condition where the cornea of the eye, over the time, starts thinning and bulging outwards and becomes cone shaped. This results in blurred vision and sensitivity to light. Keratoconus commonly affects both the eyes. Individuals aged 10 to 25 years are more affected by this condition. Keratoconus may gradually progress for 10 years or more. If this problem is detected in early stages, then glasses or soft contact lenses can correct any problems with the vision. As keratoconus advances, other types of contact lenses can be used such as rigid gas permeable contact lenses etc. Corneal transplant may be required for advanced keratoconus.
Causes of Keratoconus
The cause of keratoconus is not known, but it usually occurs with the following conditions:
- Rubbing of the eyes forcefully can be one of the causes of Keratoconus.
- Other eye problems such as retinitis pigmentosa, vernal keratoconjunctivitis and retinopathy of prematurity can also be a cause for Keratoconus.
- Keratoconus can also be caused due to other disorders like enzyme abnormalities or hereditary factors such as Down’s syndrome.
- Use of contact lenses for a prolonged period of time.
Risk Factors for Keratoconus
- Certain diseases such as Down’s syndrome, Ehlers-Danlos syndrome, Leber’s congenital amaurosis, or osteogenesis imperfect increases the risk for developing keratoconus.
- It is hereditary; i.e. having a family history of keratoconus increases the risk for developing keratoconus.
Symptoms of Keratoconus
- Blurred/distorted vision is one of the symptoms of Keratoconus.
- Increased sensitivity to bright or flashing lights.
- Not being able to see clearly during the night.
- Multiple changes in prescriptions for eyeglasses.
- Sudden worsening or clouding of vision occurring due to a condition where the posterior region of the cornea ruptures and fills with fluid.
Serious Symptoms of Keratoconus Requiring Immediate Medical Attention:
- Rapidly deteriorating eyesight.
Tests to Diagnose Keratoconus
- Medical history and eye examination.
- Eye refraction to check for astigmatism and other problems with vision.
- Slit-lamp examination is a test where a vertical beam of light is directed on the eye’s surface and a low-powered microscope is utilized to examine the eye. This test helps in evaluating the cornea’s shape and also helps in detecting other potential problems in the eye. There may be a repetition of this test with instillation of eye drops which help in dilating the pupils and makes viewing the posterior region of the cornea easier.
- Keratometry is a test where the ophthalmologist focuses a circle of light on the cornea and the reflection is measured to assess the curve of the cornea.
- Computerized corneal mapping or optical scanning techniques, such as the corneal topography and optical coherence tomography are used to take images of the cornea which helps in generating topographical map of the surface of the cornea and helps in measuring the corneal thickness.
Treatment for Keratoconus
Treatment for Keratoconus depends on the severity of the condition and the rate of deterioration of the condition.
Eyeglasses or contact lenses are used to treat mild to moderate keratoconus. The cornea becomes stable after a few years in majority of the patients. The chances of having severe vision problems with further treatment are less. Surgery is required in those patients where the keratoconus causes scarring of the cornea thus preventing the use of contact lenses.
Types of Lenses used for Treating Keratoconus:
- Eyeglasses or Soft Contact Lenses are the usual line of treatment for keratoconus. They help in rectifying blurry or distorted vision in early stages of keratoconus; however, people need frequent change of prescription for their eyeglasses or contacts due to the changing shape of their corneas.
- Rigid Gas Permeable Contact Lenses for Treating Keratoconus: Also known as hard contact lenses are the second choice in treating advancing keratoconus. These lenses may not be comfortable at first, but as the time goes on, many people get used to wearing them. Rigid gas permeable lenses can be custom made to fit the corneas.
- Piggyback Lenses for Treating Keratoconus: These lenses are recommended if rigid lenses are uncomfortable for the patient suffering from Keratoconus. This involves “piggybacking” a hard contact lens above the soft one. Trying to fit a combination of lenses takes a lot of meticulousness and expertise by the doctor.
- Hybrid Lenses for Keratoconus: These contact lenses are characterized by a rigid center surrounded by a softer ring, which gives added comfort. Patients suffering from Keratoconus who are not able to adjust to hard contact lenses may try hybrid lenses.
- Scleral Contact Lenses for Keratoconus: These lenses are used if there are any irregular changes in the cornea and in advanced keratoconus. The difference from the traditional lenses is that these lenses rest on the white region of the eye, i.e. the sclera, and go above the cornea without touching it.
Patient should get the rigid or scleral contact lenses fitted by an ophthalmologist who is experienced in treating keratoconus. Patient should also follow regular checkups and re-fittings, as an ill-fitting hard contact lens could cause corneal damage.
Surgery for Keratoconus
Surgery for treating Keratoconus is required in case of corneal scarring, acute thinning of the cornea, bad vision despite using the strongest prescription lenses or if the patient is not able to wear any type of contact lenses. There are many surgeries available for Keratoconus, which are selected depending on the region of the bulging cone and the severity of the condition. Given below are the surgical options:
- Surgical Treatment For Keratoconus Using Corneal Inserts / Intracorneal Ring Segments:In this surgery for treating Keratoconus, the doctor inserts two clear, tiny, crescent-shaped plastic inserts into the cornea. These inserts help in:
- Flattening the cone.
- Supporting the shape of the cornea.
- Improving the vision.
- Restoring normal corneal shape.
- Slowing the progress of keratoconus.
- Reducing the need for corneal transplant.
- Better fitting and tolerance of the contact lenses.
This procedure can be considered a temporary step, as the corneal inserts can be removed. The patient should remember that this surgery has risks, like any other surgery, such as infection and injury to the eye during surgery.
- Keratoplasty or Corneal Transplant to Treat Keratoconus: This is required if there is scarring or extreme thinning of the cornea. The different types of keratoplasty are:
- Lamellar Keratoplasty: This is a partial-thickness transplant where only a part of the cornea’s surface is replaced.
- Penetrating Keratoplasty: This is the most common corneal transplant and is a full-corneal transplant where the entire portion of the cornea is replaced with donor tissue.
- Deep Anterior Lamellar Keratoplasty (DALK): This helps in preserving the inner layer i.e. endothelium, of the cornea. It helps in preventing rejection by the endothelial cells in case of a full-thickness transplant.
Recovery Period for Keratoconus
It takes up to a year to recover after keratoplasty and the patient may need to wear rigid contact lenses in order to have a clear vision. It may take several years after the transplant to achieve complete improvement in vision. Although corneal transplantation is very successful to treat Keratoconus, it carries some complications such as astigmatism, poor vision, graft rejection, infection, and not being able to wear contact lenses.
Evolving Treatment For Keratoconus
There is a new treatment known as collagen cross-linking, which shows a potential for treating keratoconus. This procedure comprises of instillation of riboflavin drops in the cornea, then the eye is exposed to ultraviolet (UVA) light. This procedure helps in strengthening the cornea so that further thinning or bulging is prevented. This treatment is still in the experimenting phase and requires further studies before it can be used on patients.
- American Academy of Ophthalmology. “Keratoconus.” https://www.aao.org/eye-health/diseases/keratoconus
- Mayo Clinic. “Keratoconus.” https://www.mayoclinic.org/diseases-conditions/keratoconus/symptoms-causes/syc-20351352
- Cleveland Clinic. “Keratoconus.” https://my.clevelandclinic.org/health/diseases/17731-keratoconus
- American Optometric Association. “Keratoconus.” https://www.aoa.org/healthy-eyes/eye-and-vision-conditions/keratoconus
- American Academy of Ophthalmology. “Collagen Cross-Linking (CXL) for Keratoconus.” https://www.aao.org/eye-health/treatments/corneal-crosslinking