Keratoconus is a non-inflammatory ectasia or protrusion of the cornea. It is characterized by a progressive thinning and steepening of the cornea. As the cornea steepens and thins, the patient experiences a decrease in vision which can be mild or severe depending on the amount of corneal tissue affected. The onset of keratoconus usually starts in the teenage years or early 20’s. It rarely develops after the age of 30. In general, keratoconus develops asymmetrically with one eye more advanced than the other.
In the early stages of this condition, many patients will be able to see clearly with soft contact lenses or eye glasses. As keratoconus progresses, rigid gas permeable lenses are the first choice to correct vision. Most of the time this is a permanent remedy. Because keratoconus can progress it is important that the lenses are fitted with great care and are reevaluated at least annually by the eye doctor. The lenses that we use have a complex geometry that take into account the irregular corneal surface for all stages of this condition. The lenses that we design have multiple curves and are custom designed to fit each individual cornea correctly without traumatizing the delicate compromised corneal tissue.
In the more advanced cases of keratoconus, Pellucid Marginal Degeneration and post-LASIK ectasia, small diameter lenses will not work. This is especially true when there is a degradation of the outer layer of the cornea known as the epithelium. When this layer of the cornea is compromised, the cornea will not be able to support any form of lens whether it be a soft lens, a hybrid lens or a gas permeable contact lens.
The only lens that will provide clear, comfortable vision will be a gas permeable scleral lens. This lens will work provide clear vision because it will not touch the cornea and will not pop out of the eye when the patient moves their eyes. The scleral lens vaults over the compromised cornea and is supported by the white portion of the eye known as the sclera. The space between the back surface of the lens and the front surface of the cornea is filled with sterile unpreserved saline solution. In other words, the compromised cornea is always in a liquid environment. Vision and comfort is almost always excellent.
Below are images of keratoconic corneas with and without specialty lenses.
This is an image of a cornea with keratoconus with a scleral lens over it. This image was taken with a new technology known as Optical Coherence Tomography. The two curved lines seen over the cornea represent the front and back surface of the scleral lens. The clear space between the back surface of the lens and the front surface of the cornea is a liquid reservoir filled will unpreserved sterile saline solution.
The lenses that you are wearing are probably not fit correctly. We see this often when the lenses are fit too flat, and the design of the lens is not appropriate. The lenses are moving excessively over the cornea with each blink causing abrasions to the apex of the cone. If this continues, irreversible scarring will result and visual acuity will diminish. When I get to see a cornea like this, I often have to refit with a new rigid lens over a special soft lens which acts as a bandage. The soft lens allows the cornea to heal, while the rigid lens provides vision. Typically, this “piggy back” combination lasts no more than a few weeks. As the cornea heals, new measurements of the corneal curves are taken. It is not unusual to encounter changes in the curves and contour of the healed cornea. As this takes place, new rigid lenses are ordered to fit the healed cornea.