Keratoconus

What is keratoconus?

Keratoconus is a condition that affects both eyes and is characterised by progressive thinning of the corneal tissue, accompanied by a conical protrusion of the cornea with the greatest thinning at its tip. It can arise as a result of genetic factors, enzyme or chromosomal abnormalities, certain surgical procedures and other mechanical factors. The reported rate of keratoconus in the general population is between 50 and 230 cases per 100,000 people and is similar in both sexes.

At what age does keratoconus most commonly appear?

Keratoconus most often appears around puberty and may affect the two eyes with different levels of severity. Progression of the disease often slows between the ages of 30 and 40. The condition may be associated with other eye disorders, including congenital cataract, underdevelopment or absence of the iris and retinopathy of prematurity, as well as systemic conditions such as asthma and various genetic disorders.

What are the symptoms and prognosis?

A person may notice reduced visual acuity, blurred or distorted images, increased sensitivity to light, double images and increased tearing.

If progression is not stopped, the mechanisms that make the cornea resistant to excess water may fail. This can lead to excessive accumulation of water in the cornea together with scarring, which threatens visual function.

Diagnosis

An ophthalmologist makes the diagnosis on the basis of:

• an eye examination, including assessment of visual acuity and examination of all eye structures with a slit lamp;
• keratometry, a procedure that uses an instrument to measure the dimensions and curvature of the cornea;
• corneal topography, which measures the shape and extent of irregularities in corneal curvature, as well as corneal thickness, using a device such as Orbscan;
• anterior segment OCT.

Classification

Based on keratometric measurements and the shape of the corneal protrusion, the condition is graded as mild, moderate, advanced or very severe.

Treatment

An ophthalmologist plans treatment according to the severity of keratoconus and the possibility of achieving the best vision correction. In the early stages, vision is corrected with glasses whenever possible.

A better solution for achieving higher-quality vision may be correction with different types of contact lenses, specialist lens-fitting methods and specialised Rose K contact lenses.

In more severe cases, implanting intracorneal ring segments into the corneal tissue can improve its shape and may improve the patient's visual acuity.

If keratoconus progresses and threatens to cause further thinning, a surgical method may be required to strengthen the cornea and prevent additional thinning.

1. Corneal cross-linking (CXL) is a surgical method used while the disease is progressing and sufficient corneal tissue thickness remains for the procedure. A vitamin B2 solution and specialised ultraviolet lamps are used to create cross-links within the collagen fibre network, thereby increasing the biomechanical strength of the cornea.
2. When the cornea has developed scarring, a surgical procedure called keratoplasty may be performed. The affected corneal tissue is removed and replaced with full-thickness donor tissue in a penetrating keratoplasty. A lamellar keratoplasty approach, known as DALK, has also increasingly been used in carefully selected cases.