Keratoconus - Symptoms, Causes, Prevention, Treatment

Keratoconus

Normally, the cornea, or the eye’s clear outer lens, has a ball-like dome shape. Keratoconus occurs when the cornea thins and gradually bulges outward like a cone, unable to hold its round shape. It usually affects both eyes, the effect being more severe in one than the other.

Causes of Keratoconus

The exact causes of keratoconus remain unknown, though it is believed that people are most likely to get it from birth. Keratoconus occurs when there is a loss of collagen in the cornea. Collagen keeps the cornea strong and flexible and helps maintain its regular, ball-like shape. The loss of collagen can be caused by an imbalance between the production and destruction of the corneal tissue. There are a lot of theories that suggest that it is:

1. Developmental condition
2. Degenerative condition
3. hereditary dystrophy
4. An endocrine anomaly

Risk Factors of Keratoconus

The following factors can increase your chances of getting keratoconus:-

1. Age: Keratoconus usually starts in the teenage years but may also appear in childhood or your 30s. It can also affect people aged 40 or above, but that’s less likely to happen.
2. Family History: You have a greater chance of getting keratoconus if someone from your family has this condition. Almost 1 in 10 people with keratoconus have a parent with this condition. 
3. Inflammation: Inflammations from allergies, irritants, or atopic eye diseases can lead to a loss in the cornea tissue.
4. Eye Rubbing: Chronic eye rubbing can break down the cornea. Moreover, it may be a risk factor for disease progression. 
5. Disorders: Studies have found a connection between keratoconus and certain systemic conditions such as Downs syndrome and retinitis pigmentosa.

The symptoms of keratoconus change as the disease progresses, which include:-

1. Difficulty seeing at night
2. Glare and halos around lights
3. Increased sensitivity to bright light, making it hard to drive at night
4. Objects look blurry
5. Sudden clouding of vision
6. Double vision when looking with one eye
7. Triple ghost images
8. Light streaks
9. Eye pain and irritation
10. Headache
11. Nearsightedness
12. Irregular astigmatism (irregular curvature of the eye)

During the diagnosis of keratoconus, your eye doctor will review your family and medical history along with an eye exam. Other tests to diagnose keratoconus include:-

1. Eye refraction: The doctor measures your eyes to examine vision problems in this test. He/she may ask you to look through a piece of equipment with different lenses to evaluate which combination gives you the best vision. 
2. Keratometry: The eye doctor focuses a circle of light on your cornea to examine the reflection and determine the shape of the cornea. 
3. Slit-lamp examination: The doctor directs a vertical beam of light on the surface of your eyes to identify abnormalities in the middle and outer layers of the cornea. 
4. Computerised corneal mapping: Photographic tests, such as corneal topography, records images to create a detailed shape map of the cornea. 
5. Pachymetry: The test is used to measure the thinnest parts of the cornea.

Treatment of keratoconus depends on the severity and progression of the disease. There are two approaches to treating keratoconus: 

1. Slowing the progression: If your keratoconus is progressing, corneal crosslinking may be used to slow or stop the progression. However, this treatment does not improve the vision. 
2. Improving the vision: Improving vision depends upon the severity of keratoconus. Early to moderate keratoconus can be treated with contact lenses or eyeglasses. In the advanced stage of keratoconus, wearing contact lenses can become difficult, needing cornea transplant surgery. 

Contact Lenses

1. Eyeglasses: They can prevent blurry vision in the early stage of keratoconus. But you need to frequently change your prescription for eyeglasses as the shape of your cornea changes. 
2. Rigid Gas Permeable Contact Lenses: It allows oxygen to pass through the contact lenses and reshapes your cornea to minimise vision distortion. 
3. Hybrid Lenses: They have a rigid centre with a softer ring around the outside to provide increased comfort.  
4. Scleral Lenses: Similar to rigid gas permeable contact lenses, they provide a liquid layer between the contact lens and the front of the eye. 

1. Reduces the chances of disease progression
2. Improves visual acuity and hence the vision
3. Strengthens weakened cornea
4. Prevents corneal thinning

Risks in Delaying Treatment of Keratoconus

If left untreated, keratoconus progresses over time, leading to several side effects. In some rare cases, untreated keratoconus can even result in permanent vision loss. Other side effects include corneal scarring, making it difficult to wear contact lenses and leading to emotional distress. 

Stages of Keratoconus

Progression of keratoconus occurs differently in each eye. If the condition develops at an early age, the progression is generally more rapid. The disease's most rapid and significant progression occurs within the first 15-20 years after onset. 

Early Keratoconus

There is only a slight corneal distortion in this stage, having little or no effect on the quality of vision. Doctors usually recommend spectacles to correct myopia and astigmatism and provide adequate vision.

Moderate Keratoconus

In this stage, the corneal distortion increases, and the change in the shape of the cornea can be observed. The vision quality decreases with spectacles, and rigid gas permeable contact lenses become a better choice. 

Advanced Keratoconus

There is a slight to moderate scarring of the cornea and a substantial corneal distortion in this stage. To maintain the appropriate fitting, you may require rigid gas permeable contact lenses with steeper inside curvatures.

Severe Keratoconus

In this final stage of keratoconus, the corneal distortion is dramatic, along with substantial corneal scarring and thinning. You may need to consult an experienced corneal surgeon for a corneal transplant at this stage.