Keratoconus is a progressive non-inflammatory bilateral corneal disease characterized by paraxial thinning of stroma, which leads to an irregularity of the corneal surface. Loss of vision occurs due to an abnormal astigmatism and myopia as well as due to scarring of the cornea.
Specific features of keratoconus are thinning of the cornea, ruptures in the bowman membrane, deposition of iron in the basal cells of the epithelium and the development of Fleischer rings, folds in the stroma, as well as tearing of the descemet membrane, which results in an acute swelling.
In most patients, keratoconus develops between 12 and 20 years of age, but there are also cases of congenital keratoconus, as well as its occurrence over the age of 50 years (according to Hall).
The progression of its development is different. In some patients, keratoconus can develop within six months or one year, while in other patients keratoconus can progress for years and alternate with periods of relative stabilization.
The main method of optical rehabilitation of patients with keratoconus is the use of rigid gas permeable contact lenses, which provide the best visual acuity, correct refractive errors and irregular astigmatism. Only in cases of early keratoconus when initial changes took place it is possible to use spectacles or soft contact lenses as means of correction.
Scleral contact lenses have become the most widely used type of rigid gas permeable contact lenses for keratoconus.
Scleral lenses have the following features:
- rest on the sclera only, while not touching the cornea and can be used in cases of intolerance to corneal contact lenses;
- have a more convex shape than other types of contact lenses, and the space between the anterior surface of the cornea and the posterior surface of the lens is filled with a liquid medium, which leads to the absence of mechanical effects on the cornea and provides better comfort for patients.
“Lens Factory” produces modern scleral lenses from Contamac rigid gas-permeable material (possible options of Dk/t are 100, 125 and 200).
Two types of scleral lenses are available: “One Fit” and “One Fit Med” (they have a slightly more complex design and are suitable for more pronounced irregularity of the cornea or certain anatomical features). These lenses are classified as mini-scleral lenses that provide a greater comfort when handling and during wearing, and thanks to the design features of the lens, enable a very good oxygen permeability. This prevents the occurrence of hypoxic complications.
In case of keratoconus, especially on its more pronounced stages, scleral lenses provide a significant increase in visual acuity compared to spectacles and soft contact lenses.
Scleral lenses have a wide range of indications for use in addition to keratoconus. They are used for other types of keratectasias, corneal dystrophies, dry eye syndrome treatment, neurotrophic keratitis, thermal and chemical burns of the cornea, aniridia and many other pathologies.
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