By Ng Shu Yi, Optometrist, International Eye Cataract Retina Centre, Singapore
Glaucoma is a heterogenous group of eye disorders which causes damage to the optic nerve and permanently impairs vision. Left untreated, it eventually leads to irreversible blindness. In fact, data from World Health Organisation (WHO) disclose that glaucoma is the second most common cause of blindness globally.
Glaucomatous damage to the optic nerve is usually associated with an increased fluid pressure in the eye, known as the intraocular pressure (IOP). The IOP maintains the shape of the eye and ranges from 10 to 21 mmHg (millimetres of mercury) in the normal eye.
There are three main types of glaucoma: primary open angle glaucoma, primary angle closure glaucoma and secondary glaucoma. A variant of primary open angle glaucoma is low or normal tension glaucoma.
Two important clinical tests to aid the diagnosis of glaucoma are tonometry and gonioscopy.
Tonometry is an eye test to measure the IOP. Goldmann applanation tonometry is currently considered the gold standard for clinical IOP measurement. During this test, the eye care professional uses a tiny probe to touch the anaesthetized cornea to measure the force required to flatten the cornea. This allows the IOP to be measured.
Gonioscopy examines the eye’s drainage angle between the iris and cornea. The angle is also known as the anterior chamber angle or the iridocorneal angle. During gonioscopy, the eye care professional places a special lens with mirrors on the surface of an anesthetized eye and examines the structures in the angle to aid in the diagnosis and treatment of glaucoma patients.
Dr Au Eong Kah Guan, Medical Director and Senior Consultant in International Eye Cataract Retina Centre, gave a demonstration of Goldmann applantation tonometry and gonioscopy to first year Ngee Ann Polytechnic optometry students on 2 February 2018. A few of the students were lucky to have hands-on practice on each other under Dr Au Eong’s guidance. During the session, Dr Au Eong also shared tips and pearls from his vast clinical experience and encouraged the students to pay attention to eye examination when they graduate.