We usually think of contact lenses as simple medical devices to correct our vision problems. In fact, contact lenses are so common and widespread throughout the world that the public regards them as commodities rather than medical devices. But today, contact lenses are being used to treat severe medical eye problems. For a long time, eye doctors have used “bandage contact lenses” to treat eye problems such as filamentary keratitis, recurrent epithelial erosions, and corneal defects and abrasions.
More recently, contact lens devices such as Prokera are bringing healing properties to the cornea through amniotic tissue. The amniotic tissue is taken from the placenta and used to create a type of bandage lens to aid in healing the cornea. However, researchers have begun using contact lenses to help culture and healthy stem cells to patients. These stem cell-rich lenses are being used to treat severe eye surface diseases.
What Are Stem Cells?
Stem cells are cells in our body that are undifferentiated and waiting to be turned into specialized cells to perform certain functions. There are two types of stem cells: embryonic stem cells and adult stem cells (sometimes referred to as somatic stem cells.) These cells can differentiate into different cell types such as skin, eye, nerve and muscle cells. Adult stem cells are found in many places in the body and remain dormant until disease or tissue injury occurs. They then differentiate into different cell types to replace tissue. They are thought to be able to divide and replicate themselves indefinitely.
By contrast, embryonic stem cells only come from a 4-5 day old human embryo. When used for research, they are developed in a laboratory and not obtained directly from the public. Embryonic stem cells are able to differentiate into any tissue in the human body, whereas adult stem cells are limited to what they can develop into. Controversy exists surrounding the use of stem cells in medical care, but this usually involves embryonic stem cells as adult stem cells can be obtained directly from the body and do not involve human embryos at all.
How Does It Work?
Simple and inexpensive, the procedure is non-invasive and does not require the use of foreign human tissue or animal products. A very small amount of tissue from a patient’s eyes is harvested for stem cells. They are placed on FDA-approved hydrogel contact lenses. These cells are nurtured and grown in the patient’s own serum.
The stem cells grow rapidly and cover the surface of the contact lens in a matter of two to three weeks. When the lens is placed on the patient’s eye, the cells migrate to the cornea in a process that scientists don’t yet understand. The cells began to grow and create a new transparent layer of cells that can hopefully restore vision and correct eye surface disorders. The lens can be biodegradable. There are no sutures and no fancy equipment needed to complete the procedure.
Previous treatments using stem cells involved grafting the cells onto the eye using donated human tissue. However, the success rate varies and can fail after a few years as the healing eye cannot retain the stem cells. Using the patient’s stem cells instead of a donor’s stem cells could do away with concerns about rejection. This might be more helpful in situations in which regular corneal tissue banks are depleted or unavailable, or in places that don’t have corneal tissue banks for transplant. The newer biodegradable contact lenses contain pockets to house and protect the stem cells.
What Do Stem Cell Contact Lenses Treat?
Contact lenses loaded with stem cells are primarily aimed at treating disorders of the cornea, the clear dome-like structure on the front part of the eye. Corneal injuries most commonly affect the outermost layer of the cornea, the epithelial cells, and can be caused by scars from surgery, traumatic scars, infections, hereditary corneal defects and inflammation from severe dry eyes. Symptoms of the corneal disease include pain, tearing, fluctuating vision, and light sensitivity.
The most common condition that is treated with stem cell is grown contact lenses is limbal stem cell deficiency. Limbal stem cell deficiency can be caused by trauma from chemical burns, thermal burns and a genetic condition called congenital aniridia. Interestingly, doctors are seeing an increase in patients with limbal stem cell deficiency from other sources such as long-term contact lens wear, ocular surface disease such as chronic dry eye, cataract surgery, and certain glaucoma and pterygium surgeries.