Corneal Disease and Damage
The cornea is the transparent outer covering of the eye. It helps protect the eye against germs, dust, and other particles. The cornea also acts like a lens. As light enters the eye, it's refracted or bent by the cornea and aimed onto the retina, which captures the image and sends it for processing by the brain. To maintain transparency, the cornea contains no blood vessels. Instead, the cells get nourishment from tears and oxygen from the air.
The cornea can be damaged from an eye injury or unsuccessful corneal surgery. There are also several diseases that can lead to corneal damage. Stevens-Johnson Syndrome (erythema multiforme major) causes painful blisters on the skin and mucous membranes. In the eye, the condition can lead to severe conjunctivitis, iritis (an inflammation inside the eye), and blisters, erosion, or holes in the cornea. Keratoconus is a progressive thinning in the middle of the cornea, causing the development of an outward cone-like bulge. The process changes the shape of the cornea and causes vision impairment. Keratoconus is a progressive disease that usually affects both eyes, although sometimes at different rates. Ocular cicatricial pemphigoid is an inflammation of the mucous membranes of the eyes and oral cavity. Blisters may develop, causing pain, redness, tearing and sensitivity to light. Patients may also develop a loss of the tear film over the eye and scarring, ulceration, or perforation of the cornea.
The Boston Scleral Lens
Contact lenses can improve the vision of some people with corneal damage or disease. However, not all patients can withstand the pressure or friction of a contact on the eye. As the disease/damage progresses, a corneal transplant may become the only option for saving sight.
Doctors have developed a new type of contact lens that may be helpful for some people with corneal disease or damage. The Boston Scleral Lens is about the size of a quarter. It's made of a highly oxygen-permeable plastic, so it is more comfortable than hard contact lenses. The lens is also shaped differently, with an outward bulge in the center of the eye. That allows the outer portion of the lens to rest comfortably on the sclera (the white part of the eye). Artificial tears are placed in the "bowl-like" center of the lens, providing a cushion of nutrients and oxygen for the eye. The lens protects the eyes from exposure to air and friction from blinking. It also fills in the corneal irregularities, restoring vision. In patients who have been blind from corneal damage, the lenses have restored functional vision.
Eye care professionals are careful to point out the lens is not for everyone with eye problems. It won't help patients with glaucoma, cataracts, macular degeneration, diabetic retinopathy, or retinitis pigmentosa. However, it may be useful for patients with severe corneal disease who are facing a corneal transplant (such as Stevens Johnson Syndrome or keratoconus).
So far, about 300 patients have had their vision restored with the Boston Scleral Lens. It can be fitted in adults and children. The cost of the lenses, which includes design and fitting, is about $5,500. It's not generally covered by insurance. However, doctors don't turn people away because they are unable to pay. A foundation has been set up to take donations to help cover the cost of the lenses for people who need them. Currently, the lens is only available at the Chestnut Hill site in Massachusetts. Other eye care professionals are being trained in the fitting process, hopefully expanding availability around the world. To be considered for a fitting, patients must get a referral from their eye care doctor.
Corneal Disease and Damage