Keratoconus

Keratoconus is a disorder of the eyes affecting the cornea. The cornea of the eye is the clear transparent, dome shaped tissue that covers the iris and the pupil. The cornea shields the eye from germs, dust and other harmful matter. It also acts as the eye’s outer lens. Much like a window, the cornea controls light entering the eye. It contributes to the eye’s ability to focus. Keratoconus is deterioration in the structure of the cornea that produces a bulging from the normal round shape to a cone shape. Patients with keratoconus typically complain of deteriorating vision such as distortions, glares/flares in vision, double vision or ghost images, often affecting their ability to drive and read fine print.

Who gets keratoconus?

The prevalence of keratoconus is relatively high and occurs in 1 in 2000 people. The disease occurs in all race groups. Males are more likely to develop keratoconus than females. It affects both eyes but commonly one eye is more affected than the other. The disease starts in puberty but is usually diagnosed at age 27.

What causes keratoconus?

The cause is not clearly understood. There is a hereditary component and blood relatives of one who has keratoconus are more likely to develop the disease than those with no affected relatives .  Some conditions are often associated with keratoconus including patients with Down syndrome, patients with other connective tissue diseases such as ???? and heart value prolapse, allergic people are also more prone to the disease. Hormonal changes have been associated with keratoconus as it starts at puberty and occasionally progresses during pregnancy but no direct evidence of this exists. Eye rubbing is common in patients with conus. It is said that because the cornea is already weakened, the rubbing can cause the thinning and protrusion of the cornea. Patients that have worn hard contact lenses for longer than 12 years, for more than 15 hours a day, can develop the disease.

How does keratoconus progress?

One of the most common questions asked by patients is what to expect with regard to his / her quality of vision and whether there is a need for surgical correction , now or in their future. Studies have shown that 13% of patients will have had surgery for a corneal transplant on average 7 years after diagnosis or by age 34. This depends on a number of factors including:

• the age at which the disease was diagnosed
• longer contact leans wearing history
• if they have a more serious form of the disease
• have worst visual acuity
•  have scaring and damage to the cornea

Progression is more rapid in patients diagnosed at a younger age. The disease plateaus in most patients after about seven to ten years. There is still controversy about whether wearing hard contact lenses influences the progression of the disease or improves the vision and can be used to delay the progression.

How keratoconcus is managed

Most patients are managed by wearing spectacles and contact lenses. Usually patients start off with spectacles or spherical/toric soft contact lenses. As the vision deteriorates, rigid lenses are indicated for the best visual outcome. Contact lens wear is often complicated by episodes of intolerance, allergic reactions, corneal abrasions and other problems leading to total intolerance. As stated above 13 to 20% of patients will require a corneal transplant on one or both eyes during their lifetime. There are various surgical techniques used in correcting the keratoconus. It is advisable that patients consult a cornea specialist or a contact lens specialist who can provide appropriate contact lens care. An ophthalmologist who is a cornea specialist can advise on identifying the appropriate timing and clinical condition for a specific surgical intervention. The speciality contact lens practitioner, usually an optometrist, monitors the contact lens care to optimize vision while minimizing the complications of contact lens wear.

Patients should be advised to avoid rubbing their eyes vigorously.

There is no medication routinely indicated for keratoconus. Nonsteroidal anti-inflammatory drops, mast cell stabilizers and antihistamines (e.g. Patanol® or Zaditen® eye drops) are occasionally helpful in controlling the associated signs of ocular allergies, especially itching, that can lead to eye rubbing.

What are the complications of keratoconus?

Rarely, advanced keratoconus progresses to where breaks occur in one of the layers of the cornea which can lead to acute corneal hydrops. This is oedema in the layers of the cornea and scarring of the cornea. Patients will complain of a sudden vision loss and some pain or discomfort in the eye. There is not much that can be done for this other than making the eye feel comfortable. Many corneas flatten after hydrops and sometimes visual acuity and contact lens application may improve. If the scarring is severe a corneal transplant / surgery may be needed.

All the complications of contact lens wear develop in patients with keratoconus especially abrasions and giant papillary conjunctivitis (an allergic reaction). These can be treated with topical mast cell stabilizers such as Patanol® or Zaditen® eye drops and occasionally steroid eye drops, only after the consideration of increased risk of cataract, glaucoma and decreased ability to resist infection has been taken into account.

Conclusion

Most patients with keratoconus do well with rigid contact lens care. Although 10 to 20% of patients eventually need a corneal transplant, this number will decrease if good contact lens care is available. Studies have shown that although the disease is progressive it stabilises in most patients after some time.