Keratoconus is a condition affecting both eyes, causing a non-inflammatory protrusion or ectasia of the cornea. Recent studies have demonstrated that about 1 in 2000 people may be affected by keratoconus. Early forms of the disease can be undetected unless advanced scans of the surface of the eye are done. In general, keratoconus causes the cornea to become thinner and steeper with time causing decrease vision, which can range from mild to severe.
For mild cases of keratoconus, eyeglasses or soft contact lenses may be able to provide the patient with clear and comfortable vision. For highly irregular corneas, however, eyeglasses or soft lenses do not provide a good outcome for visual correction. Corneal rigid gas permeable lenses can provide a better alternative to improve visual acuity but do not protect the ocular surface. If the lens does not center properly on the eye or moves excessively with blinks and causes discomfort, switching to a large-diameter scleral lens may solve the problem.
Many optometrists and ophthalmologists recommend scleral contact lenses to resolve this issue. The scleral lens does not touch the compromised cornea; it is fitted in a way to vault the cornea. For that reason, these lenses often are more comfortable for a person with keratoconus. The space between the back of the lens and the front surface of the cornea is filled with a non-preserved sterile saline solution. It maintains a constant reservoir of fluid between the lens and the cornea to ensure that it remains lubricated. More over, this fluid layer also compensates for the surface irregularities, leading to improved vision. This modality can provide the comfort of a soft lens with the optical quality of a gas permeable lens. Also, scleral lenses are designed to fit with little or no lens movement during blinks, making them more stable on the eye, compared with traditional corneal gas permeable lenses. Scleral lens designs currently available are considered the best option to provide health benefits and increased comfort compared to smaller corneal rigid lenses and, in this case, soft lenses.