Myopia, Refractive Errors and Eye Growth Regulation

Overview

Myopia (short-sightedness) is the most common refractive problem. It usually results when the axial length of the eye is too long for the eye's power. This means that images of distant objects are focussed in front of the retina (the light-detecting layer of the eye) and appear blurred. While spectacles, contact lenses and laser surgery can optically correct the myopia, there is no treatment that is effective in preventing the development of myopia. As the myopic eye is enlarged, the risk of eye diseases such as glaucoma and retinal detachment may be increased. A treatment to prevent or at least slow myopia development is thus much sought after.

The School of Optometry and Vision Science's myopia research group is located within the Institute of Health and Biomedical Innovation (IHBI) at QUT and is part of the institute's Vision Improvement domain. The group is involved in many research projects, with many national and international collaborators, investigating how eye growth is regulated and why myopia develops in some individuals. We are using both human based and animal based studies to shed light on different aspects of this complicated problem. In particular we are interested in how the environment alters refraction, the pathways from retina to sclera involved in eye growth control and the cellular and biochemical mechanisms involved.

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Lead unit Faculty of Health Other units
Research area
Vision Improvement
 

Details

Myopia - human based research

The length of a person's eye can be measured using A-scan ultrasonography. Here Dr Schmid measures the axial length of a patient attending our clinic for full myopia assessment and advice.

Human based research

Our human based research predominantly revolves around the hypothesis that myopia development is due to the presence of image blur. We are investigating this by studying the dynamics of the accommodation system and the visual system's sensitivity to image blur. We are also comparing the visual performance of myopes with that of non-myopes.

The length of a person's eye can be measured using A-scan ultrasonography. Here Dr Schmid measures the axial length of a patient attending our clinic for full myopia assessment and advice.


Myopia - independent pathways

Animal based research

Here we use the chick as a model for eye growth regulation. Eye growth is monitored using A-scan ultrasonography and refractive error changes using retinoscopy. Our two main areas of interest include:

  • determining how the eye guides its growth using visual feedback
  • investigating how different drugs alter eye growth.

We are also currently working on the role of the GABAergic, dopaminergic, muscarinic and serotonin systems in eye growth regulation.

An important question is what retinal transmitters may be involved in eye growth and how the signal to speed up or slow down growth gets from the retina, where it is thought to be generated, to the sclera, which ultimately has to change in size. Both the dopaminergic and muscarinic systems appear to have a role in this process. Their effects are not additive, but neither do they work in isolation (see diagram).

Projects

Recent projects in human based research

  • Comparison of accommodation stimulus response curves of myopes and emmetropes.
  • Hyperopia is predominantly axial in nature.
  • Refractive error changes of optometry students.
  • The effect of myopia on the retinal nerve fibre layer around the optic nerve head using the GDx.

Recent projects in animal based research

  • Effects on the compensatory responses to positive and negative lenses of intermittent lens wear and ciliary nerve section in chicks.
  • Contrast and spatial frequency requirements for emmetropization in chicks.
  • Inhibitory effects of stroboscopic light on form-deprivation and lens-induced myopias show different frequency tuning and patterns of axial change in chick.
  • Apomorphine inhibits lens-induced myopia but not lens-induced hyperopia in chick.
  • The inhibitory effects of apomorphine and atropine on form-deprivation myopia are not additive in chick.
  • Eye drops that lower intraocular pressure do not prevent myopia development in chick.
  • Sharp vision - a prerequisite for compensation to myopic defocus in the chick?
  • Imposed retinal image size changes - do they provide a cue to the sign of lens-induced defocus in chick?
  • Influence of controlled viewing conditions on emmetropization to imposed myopic defocus in the chick.