The tooth has more uses than chewing. It can also help restore vision in some cases.
An eye for an eye only makes the world go blind, said Mahatma Gandhi. But using the tooth can help restore vision in blind patients with terminal corneal disease. This revolutionary procedure affords the priceless gift of sight to patients otherwise destined to a lifetime of darkness.
Originally described by Strampelli in Italy, it was modified extensively by Giancarlo Falcinelli, his student, who termed the procedure modified Osteo-Odonto Keratoprosthesis (MOOKP). He has perfected the technique over the past 40 years and facilitated the transfer of knowledge – allowing patients in India to benefit from the complex surgery – since 2003.
The term OOKP refers to the use of a bone-tooth (osteo-odonto) complex to create a plastic cornea (keratoprosthesis). This composite is the heart of this surgery and allows patients unsuitable for corneal transplantation to see again. Since the plastic cylinder does not require nutrition to remain clear and viable, this surgery can work even in extremely dry eyes.
Such ocular conditions are encountered in persons who have suffered extensive chemical burns to the eyes, severe drug reactions (termed Stevens Johnson syndrome), immunological destruction of the ocular surface, and in other conditions like poorly fitted contact lenses, multiple ocular surgical procedures, and other genetic conditions.
In persons who have such disease in both eyes, vision can be limited to light perception only, and they are unable to move around without help and support. Since many of these conditions affect young adults in the prime of their life, there are considerable economic and social implications to this problem. The MOOKP offers help to such patients.
When assessing patients for suitability, the doctor will look at the potential for vision, the state of the teeth and general health of the patient. If found suitable, the surgery is performed in two stages with a three-month interval between the two. It is a complex procedure requiring eye surgeons, dentists, and skilled anaesthetists.
The first stage is preparatory; the canine tooth is harvested and the surface of the eye is prepared by removing scar tissue and is reconstructed using a mucosal flap from the inside of the cheek. The tooth is bonded to the plastic cylinder and the composite is placed in a skin pocket under the eye to develop a connective tissue covering.
Three months later, the composite is removed from its pocket. The mucosal flap on the eye is peeled back and a hole is made in the cornea. The interior of the eye is prepared for the cylinder, after which the composite lamina is placed with the cylinder inside the eye. The mucosal flap is then replaced to protect the cylinder, which protrudes through an opening in the mucosa.
Post-operative care includes use of antibiotics to protect against infection and regular dressings to ensure the health of the implant and the mucosa. After a week of such care, the visual improvement can be determined. Further care is less intensive and patients can return to their normal activities thereafter.
Although the procedure can help restore vision in patients with advanced ocular surface damage who cannot be helped by any other procedure, it requires extensive surgery – often two stages, each lasting six hours or so.
The post-operative appearance of the eye is unlike that of the normal eye due to the use of the mucosal flap.
While central vision is often normal, the use of a plastic cylinder restricts the field of vision to about 30 to 35 degrees. However, this is quite enough to restore functional capabilities to such patients – some of whom can even drive vehicles – albeit carefully. Long-term results with this procedure have also proven quite encouraging.
There are many advances in medicine and ophthalmology, but the resurgence of this technique in the past decade – due to the kindness of the Italian surgeon and the endeavours of the Indian surgeons has helped more than 100 Indian patients regain the gift of sight. The tooth thus has uses other than chewing and smiling.
The writers are Chennai-based consultant ophthalmologists. E-mail: email@example.com