Irregular Cornea

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Contact Lens for Irregular Cornea

Cornea is the most exterior “window” of the eyes, it is both the eyes’ first line of defense and a critical factor in focusing the light onto the retina. When the cornea is curved in a normal prolate way, it can help to focus the light ultimately onto the retina, so we can see clearly. Generally, irregular cornea occurs when the cornea is curved in a non-uniform and uneven way, preventing image from being focused properly on the retina. This can create moderate to severe distortion of image, resulting blurred vision at all distances. Irregular cornea profiles can range from oblate shape to hyper-prolate shape as shown below.

Prolate (Normal Cornea Shape)
Oblate
Hyper-Prolate

Due to asymmetrical corneal shape, the resultant aberrations cannot be optimally corrected by glasses or standard contact lenses. To mask the abnormal corneal surface, specialty lenses like semi-scleral contact lenses will help to reduce the aberration and improve the sharpness in vision. While up to date in Malaysia, the most common cause of irregular cornea is keratoconus.

Normal cornea
Keratoconus

Keratoconus (kerato – cornea, conus – cone) is a degenerative disorder of the eye in which structural changes within the cornea cause thinning and hence, changing into a conical shape. It is caused by a progressive, non-inflammatory and usually bilateral corneal ectasia, where protein fibers in the eyes called collagen become weaker and the cornea can no longer hold its shape.

What is it like living with keratoconus?

Due to its conical shape, patients with keratoconus do experience symptoms like extreme blurring and distortion of vision (where straight lines appear bent), extreme glare especially at night or even eye redness. Most often, keratoconic patients may experience changes in their prescription every year due to its progressive changes.

What causes keratoconus?

In Malaysia, keratoconus is estimated to affect 1 in every 2000 people, especially teenagers up to the early 30 year-old seem to occur in populations throughout the world.

Besides, keratoconus is also associated with:

  • – Excessive exposure to ultraviolet (UV) rays from the sun.
  • – Excessive eye rubbing due to allergies like eczema, asthma, food allergy or chronic eye irritation.
  • – Systemic diseases like Down Syndrome or Marfan Syndrome.
  • – Genetic predisposition – this explains why keratoconus often affects more than one member in a family.-

Semi-Scleral Lenses - An Option for Keratoconus

Keratoconic corneas are as unique as fingerprints, thus there is no such thing as one lens size that fits all. Like other contact lenses, the condition of the cornea should be carefully assessed before semi-scleral lenses can be prescribed. However, the shape of a keratoconic cornea is different from a healthy cornea, relatively smaller lenses may distribute their weight onto the uneven corneal surface, leading to destabilization of lenses.

In Malaysia, keratoconus is estimated to affect 1 in every 2000 people, especially teenagers up to the early 30 year-old seem to occur in populations throughout the world. Additionally, the liquid reservoir can provide adequate wearing comfort too! This is not only because the lenses are not touching or irritating the cornea, but also helping to hydrate the eyes, keeping them well-lubricated and healthy during lens wear.

Semi-scleral lenses are generally ranging from 13mm to 15mm in diameter. The size of the lenses used is often judged by the degree of complexity of keratoconic condition. Milder form of keratoconus can be easily managed by lenses at the smaller end of the spectrum, whereas more complex keratoconus might require lenses with larger liquid reservoir as they can have higher capacity to bridge larger changes of the corneal curvature.

Keratoconus is a progressive eye condition, therefore, no two patients are quite the same in terms of the shape of cornea. Surely, it takes higher expertise and definitely longer chair time to get you an ideal lens. Consult us for more and allow us to help you on the right decision for an ideal visual experience.