I read with interest the announcement of iris scanning for identification purposes by the Immigration and Checkpoints Authority ("ICA to start collecting iris images for border clearance"; yesterday).

As an ophthalmologist, I have no doubt about the accuracy of iris imaging for identification purposes.

But the permanence of the human iris configuration is not a given.

The iris can be affected by eye diseases such as eye inflammation, and pigmentary and vascular disorders.

Episodes of extreme eye pressure elevation (glaucoma) can also affect iris muscles, and hence affect the appearance of the iris.

Furthermore, eye doctors often perform laser surgery on the iris for the treatment of glaucoma, effectively puncturing a hole or creating contractile scars on the iris to alleviate eye pressure.

In some unique cases, we even have to affix artificial lenses on the iris. Complications of eye surgery can also cause iris scars or defects.

Eye trauma is another instance where the iris may be altered.

Although milder cases may be imperceptible, severe injuries may require iris repair surgery, some to the extent of requiring implantation of artificial irises.

The advancement in artificial irises has been a milestone in eye reconstruction surgery.

State-of-the art artificial irises can now be matched both in colour and detail to another eye. Such artificial irises restore not only vision and visual quality, but also appearance and self-confidence, particularly in eyes with light-coloured irises.

I hope that the authorities are cognisant of the developments in the medical field with regard to eye diseases and treatments involving the iris.

When the need arises, the public may require the necessary support from their eyecare providers for certification of identity, such as in the event of eye disease, injury and treatment.

Daphne Han Chuk Yin (Dr)