Keratoconus - Symptoms, Causes, Diagnosis & Treatment

What is Keratoconus?

Keratoconus is a rare eye disorder that affects about 1 in 1,000 people.⁴ It occurs when the transparent outer layer of the eye (cornea) becomes thin and bulges outward like a cone.  

The cornea focuses light that enters your eye. An irregular corneal shape can cause people with keratoconus to experience:

• Blurred vision
• Sensitivity to light
• Loss of visual acuity

Keratoconus usually occurs in both eyes, though one eye is often worse. Symptoms typically start between ages 10 and 25. Keratoconus can progress slowly for 10 years or longer before it stabilizes.

Keratoconus can’t be cured or reversed. If left untreated, it can lead to permanent vision loss.

Keratoconus Treatment

Treatment for keratoconus depends on the stage, severity, and rate of progression. The goals of treatment are to improve vision and slow the progression of keratoconus.

Treatment for Mild and Moderate Keratoconus

People with keratoconus usually have poor vision due to the cornea's irregular shape. For this reason, vision correction is often necessary.

Corrective Lenses

In the early stages of keratoconus, many people can achieve excellent vision with:

• Soft contact lenses. These comfortable, flexible contact lenses can correct blurry vision.
• Eyeglasses. Glasses are an option for people who are contact lens intolerant.

As keratoconus progresses, glasses and soft contact lenses no longer provide enough vision correction.

Corneal Collagen Cross-linking (CXL)

Progressive keratoconus can be slowed down by this minimally-invasive, advanced therapy. Corneal collagen cross-linking (CXL) is a new, in-office procedure that takes only three steps:

1. Your ophthalmologist numbs your eye with special drops, then removes part of your cornea’s outer layer.
2. They administer vitamin B (riboflavin) drops into your eye. They do this many times over 30 minutes or more.
3. Your doctor shines an ultraviolet light on your eye for 30 minutes more while they keep adding drops.

Cross-linking treatment works by reinforcing collagen bonds in the cornea. This makes the cornea stiffer, which can stop it from bulging outward.

Though CXL can slow the progression of the disease, it cannot reverse keratoconus or improve vision.

Treatment for Intermediate and Advanced Keratoconus

When eyeglasses and soft lenses are no longer effective, more advanced treatments and surgical options are available.

Specialized Contact Lenses

Various types of contact lenses may offer improved vision for people with advanced keratoconus:

• Rigid gas permeable contact lenses. Unlike soft lenses, rigid contact lenses don’t conform to the cornea’s shape. This allows them to correct visual distortions caused by a cone-shaped cornea.
• Piggyback lenses. These consist of a hard contact lens on top of a soft lens for comfort and optical clarity.
• Hybrid lenses. These lenses have a hard middle and soft edges for comfort.
• Scleral lenses. These are for severely misshapen corneas. They rest on the white part of the eye (sclera) instead of directly on the cornea.
• PROSE contact lenses. PROSE (prosthetic replacement of the ocular surface ecosystem) is a prosthetic device. It’s often a last resort before surgery.

Intrastromal Corneal Ring Segments (Intacs®)

Intacs corneal implants are plastic, crescent-shaped rings that flatten the corneal surface. When inserted into the cornea, Intacs help re-focus light rays onto the retina for clearer vision.

An Intacs procedure takes about 15 minutes and has a high success rate. However, some people with severe keratoconus may need to wear contact lenses after the procedure.

Your doctor may combine it with corneal collagen cross-linking to further slow the progression of keratoconus.

Corneal Transplant Surgery

If other keratoconus treatments prove ineffective, your doctor may recommend corneal transplant surgery. 

This surgical procedure involves removing your corneal tissue and replacing it with a donor cornea. It’s typically an outpatient procedure that takes about one hour.

You may have blurry vision for several months afterward. Nearly everyone who gets a corneal transplant must wear glasses or contact lenses after surgery.

How is Keratoconus Diagnosed? 

A comprehensive eye exam by a licensed ophthalmologist is used to diagnose keratoconus. 

During the examination, the eye doctor will:

• Look at the external appearance of the eye for a cone-shaped cornea
• Test visual acuity (clarity of distance vision)
• Use a slit-lamp (microscope) to look for corneal thinning 
• Utilize corneal topography (imaging study to look at the health of the cornea)

Can You Prevent Keratoconus? 

You cannot prevent keratoconus, but effectively treating and managing allergies and asthma can reduce eye rubbing, reducing the risk of developing keratoconus.  

What Causes Keratoconus?

Keratoconus occurs when collagen protein fibers in the eye grow weak and thin. Exactly why this happens remains unclear.

Experts believe genetic and environmental factors are responsible for the development of keratoconus. 

Risk factors for keratoconus include:

• Family history of keratoconus
• Repeated eye rubbing
• Down syndrome
• Ehlers-Danlos syndrome
• Retinitis pigmentosa
• Allergies and asthma

Summary

Keratoconus is a rare eye condition that causes the cornea to bulge and develop a cone shape, leading to distorted vision.  

Keratoconus typically starts during puberty. It progresses over several years and is linked to genetics and environmental factors. Symptoms include blurred vision and light sensitivity. Repeated eye rubbing can make keratoconus worse.

While keratoconus can’t be cured, several treatments can help slow progression and improve vision. These treatments include eyeglasses, hard and soft contact lenses, corneal cross-linking, and corneal transplant surgery.