What Causes Keratoconus?
The precise cause of keratoconus is unidentified. There are many theories based on research. However, no one theory explains it all and it may be caused by a combination of factors.
It is thought that genetics, the environment and the endocrine system may contribute to keratoconus.
One hypothesis is that keratoconus is genetic because in some cases there does appear to be a familial association. From the currently available information there is less than a one in ten chance that a blood relative of a keratoconic patient will have keratoconus. The bulk of patients with keratoconus do not have other family members with this disease. Studies show that keratoconus corneas lack vital anchoring fibrils that structurally stabilize the cornea, which allows that cornea to “protrude forward” into a cone-shaped appearance.
Eye Rubbing: Keratoconus corneas are undoubtedly damaged by minor trauma such as eye rubbing. Poorly fit contact lenses that rub against the irregularity of the KC cornea have been implied as a possible cause of keratoconus.
Allergies: Many who have keratoconus report forceful eye rubbing and also have allergies, which result in itching, leading to eye rubbing, however the link to allergic disease also remains unclear. A higher percent of keratoconic patients have disorders such as hay fever, eczema, asthma, and food allergies, which are considered atopic diseases.
Hormonal: Another hypothesis is that the endocrine system may be involved because keratoconus is generally first detected at puberty and may progress during pregnancy. This theory has not been proven.
Signs Symptoms and Diagnosis:
The earliest signs of keratoconus are typically blurred vision and recurrent changes in eyeglass prescription, or vision that cannot be improved with glasses. Symptoms of keratoconus commonly begin in late teenage years or early twenties, but can start at any time.
Patients may report the additional following symptoms:
- Difficultly driving at night, increased light sensitivity and glare
- A halo around lights and ghosting (especially at night)
- Eyestrain, distorted images
- Headaches and general eye pain and discomfort
- Eye irritation, excessive eye rubbing
Keratoconus can typically be diagnosed with a microscopic slit-lamp examination. The characteristic signs of keratoconus that the doctor will observe when examining Keratoconic eyes include:
- Corneal thinning, measured by Pachemetry
- Distorted corneal curvature as measured by Topography
- Fleischer’s ring – an iron colored ring surrounding the cone
- Vogt’s striae – stress lines caused by corneal thinning
- Apical scarring – scarring at the apex of the cornea
- Irregular mires on Keratometric exam
Early Detection Of Subclinical Keratoconus
Drs. Li, Yang and Rabinowitz conducted a longitudinal study at the Cornea-Genetic Eye Institute, Cedars-Sinai Medical Center in Los Angeles, California to determine whether there would be a correlation between corneal topography and clinical signs of keratoconus that might be used for early detection of subclinical keratoconus. The study results established that there were significant differences at baseline topographical and Keratometric measures between the normal, keratoconus-suspect, and early keratoconus groups in all indices. Over a median follow-up of 4 years, approximately 28% in the keratoconus-suspect group progressed to early keratoconus and 75% in the early keratoconus group progressed to advanced keratoconus.
Keratoconus is usually managed by many distinctive contact lens designs. No one design is best for every type of keratoconus. Since each lens design has its own unique features, the doctor carefully assesses the needs of the individual condition to fit the lens that offers the greatest combination of visual acuity, comfort and corneal health.
Corneal Collagen Crosslinking (CXL)
CXL with Riboflavin (CXL) is an emerging keratoconus treatment. CXL works by increasing collagen crosslinks, which are the natural “anchors” within the cornea. These anchors are accountable for inhibiting the cornea from bulging out and becoming steep and distorted.
After patients have been successfully fit with contact lenses, a moderate percentage of complications and unfavorable reactions are related to skipping or modifying the prescribed method for cleaning, disinfecting, and storing their lenses. Compliance is the key to long-term success for all contact lens wearers. It is especially important for keratoconus patients, since they are virtually totally dependent upon contact lenses for all their visual tasks. Eye infections, while rare, can be harmful, preventing patients from wearing their contact lenses for days and occasionally may result in long-lasting corneal scarring and loss of vision. A comprehensive understanding of the role played by each of the rigid gas permeable lens care products will help keep lenses clean and eyes healthy.
Corneal Disease Management
The cornea is the front, clear window of the eye. Some describe it as the windshield or watch crystal of the eye. Diseases of the cornea can cause loss of vision, pain, and associated symptoms such as glare and headaches.
In order to diagnose corneal disease, the eye doctor will examine the cornea through a slit lamp microscope that gives a highly magnified view of all five layers of the cornea. If indicated, painless drops with stains can be used to check the surface cells of the cornea. Specialized scans can further evaluate the cornea: a topographic map of the corneal shape gives information about astigmatism, corneal dystrophy, and whether the patient is a good candidate for LASIK or other vision-correcting procedure; a one-second ultrasound measurement of corneal thickness helps rule out pathologic conditions; OCT scans of the cornea reveal deeper, invisible abnormalities.
Management of corneal infections is done with antibiotics, usually drops, and follow-up examination is easily performed using the slit lamp microscope to chart the progress of the treatment.
Conditions such as dry eye can affect the corneal surface. Your doctor will evaluate the tear film on the cornea with sophisticated measurements, including tear film osmolality, a new, objective means of determining in a few seconds how your tears’ concentration compares to normal subjects.
Irregular corneas, such as those seen in keratoconus, can now be managed in many ways, including specialized contact lens fitting and collagen cross-linking to stabilize the corneal shape.
Growths that develop on and around the cornea, such as pterygia and pingueculae, are removed as an in-office procedure with no patching required. Injury to the cornea can be managed with drops or a bandage soft contact lens that promotes healing of the corneal surface and relieves pain.
In cases where the cornea becomes opaque or very distorted, a corneal transplant can restore clear vision. There are different techniques now for this surgery, but it is performed as an outpatient procedure and, depending upon the indication for surgery, the success rate can be greater than 95%.
In some instances, corneal diseases are preventable. For example, good hygiene and regular vaccinations can protect against many infectious diseases. Glasses and sunglasses with 100% ultraviolet block can minimize damage from the sun’s rays, including pingueculae, pterygium, and eye surface cancers (carcinomas). Following directions about the appropriate use and care of contact lenses can help avoid corneal damage. Safety glasses protect against many types of trauma. A healthy diet with plenty of omega-3-fatty acids and sufficient vitamin A are especially important for maintaining a protective tear film layer. Regular eye examinations can detect certain conditions in their earliest stage when they might be most easily treated.