Seeing more on glaucoma

UNSW scientists have bridged a key knowledge gap in the diagnosis of glaucoma, allowing observable damage to the optic nerve caused by the condition to be accurately and directly linked to vision loss.

Glaucoma is one of the leading causes of irreversible blindness in the world ⎼ more than 300,000 Australians are estimated to have the condition.

Sometimes referred to as the “sneak thief of sight”, it is often asymptomatic in the early stages of the disease, with about half of all cases in the general population estimated to remain undiagnosed. Glaucoma leads to irreversible damage of the optic nerve, resulting in loss of vision.

Clinically, glaucoma is diagnosed through a combination of clinical tests including eye pressure measurement; visual inspection of eye structures, specifically around the optic nerve; and assessment of functional loss using a technique referred to as standard automated perimetry, which measures a person’s field of vision.

Recently, new imaging instruments that allow precise measurements of the optic nerve thickness and integrity have been increasingly used for diagnosis.

For decades, clinicians and scientists have been baffled by a mismatch between structural and functional deficits and noticing that, in some cases, there was no detectable loss of vision despite obvious damage to the optic nerve.

This is contrary to theoretical work suggesting eye structure and eye function should change at the same time.

This mismatch potentially prevents accurate and timely diagnosis of glaucoma and creates a high risk of irreversible vision loss for patients not being treated in time.

Researchers at the Centre for Eye Health and UNSW School of Optometry and Vision Science have previously patented a new perimetry technique allowing glaucoma to be detected earlier than with standard automated perimetry.

Now, for the first time, they have established a model that can robustly predict changes in ganglion cells ⎼ the neurons making up the optic nerve ⎼ that occur with age or with the disease and correlated them with functional loss.

The study, led by Dr Barbara Zangerl, is published in Investigative Ophthalmology and Visual Science, one of the top-ranking journals in the field.

“Neither the functional nor structural models currently applied in clinical practice adequately reflect our understanding of changes in retinal ganglion cells responsible for glaucomatous damage and thus may be not be sensitive to early disease detection,” study first author and PhD candidate Nayuta Yoshioka said.

Centre Director Professor Michael Kalloniatis said: “By developing better models to describe both functional and structural changes in the ganglion cell layer of the retina, we were able to consolidate our theoretical understanding of retinal changes occurring with age and with disease. This work has shown how they are directly related.”

The Centre for Eye Health is a joint initiative of UNSW Sydney and Guide Dogs NSW/ACT. A core goal of the organisation is to reduce the incidence of preventable blindness in the community by providing imaging services, high-quality education for the optometric profession and research into eye disease, results of which are published in high-impact peer-reviewed journals.