OOK Prosthesis - A Tooth for Restoration of Vision!

Humans have five basic senses: sight, hearing, smell, taste and touch. All are important for sustainable living but in my opinion, the one who’s loss affects life the most is – sight. Blindness pushes the visually impaired into literal darkness and opens doors to a different way of living life of which the sighted are unaware. Worst case scenario is for those individuals who’ve been sighted for some part of their lives and then lost their vision to corneal diseases. Corneal diseases are among the major cause of global blindness, secondary only to cataract. Corneal transplantation is a viable treatment modality to restore vision again. Can prosthetics help in regaining sight for cases where this surgery is not indicated? Osteo-Odonto Keratoprosthesis (OOKP), also known as 'tooth in eye surgery', is a unique form of artificial cornea surgery & prosthetic rehabilitation to restore the vision of patients with the most severe, end-stage forms of corneal blindness that are not amenable to corneal transplantation or other forms of surgery. OOKP is the ideal treatment for patients with end-stage inflammatory corneal diseases. A portion of tooth along with bone is used to support an optical cylinder to restore vision in such patients. It requires multidisciplinary approach involving dentists, ophthalmologists, and radiologists. HISTORY(1) OOKP was first described in 1963 by Professor Benedetto Strampelli, San Camillo Hospital in Rome. He had noted that gutta-percha will remain in the root canal of a tooth indefinitely, but will be rejected if implanted into soft tissues. So it would seem probable that if a polymethyl methacrylate or acrylic cylinder implant could be held in a piece of the patient's composite bone-tooth lamina, and the whole assembly placed in a corneal envelope, the tooth and bone would form an autograft picture-frame for the acrylic, and so prevent its extrusion . Falcinelli later modified the technique in a stepwise manner in the mid 1990’s. This is now known as Modified Osteo-Odonto-Keratoprosthesis (MOOKP) and is recognised internationally as giving the best, long-term visual and retention results among all keratoprostheses, especially in a dry eye. SELECTION CRITERIA OF PATIENT (2)

INDICATIONS- Patients with bilateral corneal blindness resulting from -	CONTRAINDICATIONS
Severe end stage Stevens-Johnson syndrome/Lyell Syndrome/ trachoma	Patients who are satisfied with their level of vision /unilateral blindness
Ocular cicatricial pemphigoid	Children under the age of 17
Chemical or thermal burns	Eyes that have no light perception
Perforating injuries	Evidence of phthisis
Severe keratitis/dry eyes	Advanced glaucoma
Multiple failed grafts / graft-versus-host disease	Irreparable retinal detachment

SELECTION CRITERIA OF MUCOSAL DONOR SITE & TOOTH(2) After intraoral examination and radiography, a mucosal donor site & tooth is selected.

• The mucosa should be normal in consistency and free from disease.
• Any site with lesions like recurrent aphthous ulceration, leukoplakia, lichen planus and oral submucous fibrosis should be avoided,
• Detrimental habits like smoking and betel nut chewing should be discontinued as it will compromise tissue quality.

Usually, buccal mucosal sites are preferred as lingual muco-periosteum is difficult to preserve.

INCLUSION CRITERIA FOR TOOTH	EXCLUSION CRITERIA FOR TOOTH
Tooth should be vital	Non-vitality,
Should be healthiest, best-positioned, best shape & size	Previous root canal therapy
Should have good covering of alveolar bone	Inadequate bone investing the root
Should be single rooted with a long and large root	Peri-radicular pathology
Extraction the tooth should be along with alveolar bone	Close proximity of adjacent teeth/vital structures.