Business Times - 28 Mar 2009
Giving sight to the blind
A complicated two-stage medical procedure called tooth-in-eye surgery has given 25 patients the ability to see. By Melissa Heng
SINGAPORE'S top eye surgeon Donald Tan has given 25 blind patients new sight, thanks to a compli-cated medical procedure called Osteo-Odonto-Keratoprosthesis, or simply, tooth-in-eye.
'Tooth-in-eye surgery is a difficult operation that is done in two stages and requires a team of specialists from the radiology, dental and eye divisions,' explains Professor Tan, head of the corneal service and director at the Singapore National Eye Centre (SNEC).
The tooth-in-eye procedure was developed by Italian doctors back in the 1960s but due to its complexity was abandoned - before being resurrected in recent years. Only five countries are offering it, including Singapore.
Those who'll benefit most from it will be patients who'd been blinded in accidents and chemical burns, says Prof Tan. 'Some suffer from Stevens-Johnson syndrome (SJS), while others have had multiple corneal graft failures. In all cases, maximal visual potential has been achieved.' (SJS is brought on by viral infection such herpes simplex or a drug allergy. It causes severe skin and mucosal blistering, especially the eyes, leading to scarring and blindness.)
Tooth-in-eye surgery takes more than two months and is done in two stages involving up to five different procedures.
'First, the eye is opened up and the entire inner surface of the eyelids, cornea and scar tissue is removed. We then transplant the inner mucosal lining of the cheek on to the new eye surface,' he explains.
'Next, we remove a canine tooth and some of the adjacent bone from the patient. We shave this down, drill a hole, and then fit it with an artificial cornea made of a medical-grade plastic optical cylinder. After this, we implant it into the patient's cheek to grow a new blood supply.'
The second stage, involving the actual insertion, is done about two months later.
'We open the cheek mucosal lining over the eye, remove the tooth-bone-cylinder from the cheek and insert this into the cornea,' says Prof Tan.
After the final surgery, light can enter through the plastic cylinder, and the patient will regain good vision.
'Over half of our patients achieve 20/20 vision, three-quarters regain at least driving vision of 20/40 and the rest reach their best visual potential,' says Prof Tan.
Only one eye is treated at a time, with the other eye 'in reserve'.
Selection for the operation is strict because there are conditions to be met due to the complexity of the surgery.
'The most basic criterion is that the retina and optic nerves must still have some function for visual recovery, as the treatment replaces the entire front of the eye only,' he says. 'So those who are born blind or are blind from retinal or optic nerve disease will not qualify,' he says.
Patients with glaucoma cannot regain full sight, though some vision can be restored. And only teenagers and adults qualify for the procedure - teeth from children are unsuitable.
Expertise aside, cost is an issue. 'Because of the nature of the procedure, costs can be astronomical,' says Prof Tan. 'The UK, for example, charges about $55,000. Thankfully, since SNEC has access to public funding, we can afford to charge a lot less - about $23,000.'
While there is no issue of rejection (since all the 'hardware' - tissue, bone and tooth - is taken from the patient) and with no cases of extrusion of the implant so far, patients who have their operations in Singapore will be offered lifelong follow-ups. 'We will continue to look out for our patients for the rest of their life,' says Prof Tan. 'Having a new eye doesn't mean the new eye is invincible. So we watch them every year with CT scans, etc, to make sure everything is going fine. Many of these patients also have glaucoma and retinal problems, which need ongoing management.'