Properties Of Human Photoreceptors Measured Using A Scanning Laser Ophthalmoscope To Illuminate And Image The Retina
Funder
National Health and Medical Research Council
Funding Amount
$352,000.00
Summary
Vision begins with the detection of light by the rod and cone photoreceptors in the retina lining the interior of the eye. Although much is already known about the way that light is detected and the signals are processed, a great deal remains to be learned. Some of the outstanding questions could be answered using modifications to a relatively new instrument called a scanning laser ophthalmoscope (SLO) which provides images of the interior of the eye. The aims of this project are to develop a mo ....Vision begins with the detection of light by the rod and cone photoreceptors in the retina lining the interior of the eye. Although much is already known about the way that light is detected and the signals are processed, a great deal remains to be learned. Some of the outstanding questions could be answered using modifications to a relatively new instrument called a scanning laser ophthalmoscope (SLO) which provides images of the interior of the eye. The aims of this project are to develop a modified SLO, which is able to measure the levels of visual pigment (rhodopsin) in the living eye, which is also able to deliver visual stimuli to the eye, and which finally is extended to use adaptive optics so that it can image and excite individual cone photoreceptors. Using this device, we will be able to measure the regeneration of visual pigment following exposures to intense illumination, to help explain the slow recovery of visual sensitivity after intense light. We will also be able to measure the electroretinogram (ERG) from localized retinal areas, to investigate how the properties of the photoreceptor cells vary across the retina. And finally we will be able not only to visualize the individual tiny cone photoreceptors, but also to stimulate them selectively, so that we can determine the responses of the different classes of cone (red-, green-, and blue-sensitive cones) in the living human eye.Read moreRead less
Electroretinogram Recordings Of Human Scotopic Dark Adaptation Following Intense Bleaching Exposures
Funder
National Health and Medical Research Council
Funding Amount
$272,250.00
Summary
After a human subject has been exposed to intense illumination, it can take many minutes for the eye to regain full sensitivity, as one experiences (for example) when entering a dark cave after being out on a bright sunny beach. This project will investigate the processes that occur in the cells of retina lining the back of the eye, that prevent the instantaneous recovery of vision following intense illumination. Electrical recordings will be made from the eyes of normal individuals, using new t ....After a human subject has been exposed to intense illumination, it can take many minutes for the eye to regain full sensitivity, as one experiences (for example) when entering a dark cave after being out on a bright sunny beach. This project will investigate the processes that occur in the cells of retina lining the back of the eye, that prevent the instantaneous recovery of vision following intense illumination. Electrical recordings will be made from the eyes of normal individuals, using new techniques that allow the activity of different types of nerve cell in the retina to be monitored. The study will determine how it is that events in the light-detector cells of the eye (the rod and cone photoreceptors) influence the activity of subsequent nerve cells in the visual system, and how these events contribute to the poor vision that one experiences following bright lights.Read moreRead less
Investigating The Mechanisms Underpinning The Dynamic Vessel Response In People With Diabetic Retinopathy
Funder
National Health and Medical Research Council
Funding Amount
$18,808.00
Summary
Endothelial dysfunction has been well-hypothesised as one of the key players in the pathogenesis of DR. However, there is strong evidence suggesting a neurovascular coupling mechanism in the retinal circulation during flicker. It is therefore unclear whether reduced flicker light induced vasodilation observed in diabetes and DR is associated with endothelial dysfunction, an impairment of neurovascular coupling or both. This project aims to address this important knowledge gap.
Functional Recovery From Retinal Degeneration: Genetic, Environmental And Senescent Models
Funder
National Health and Medical Research Council
Funding Amount
$265,888.00
Summary
This project is directed towards treatment for the blindness caused by retinal degeneration. The retina of the eye degenerates in several groups of diseases, and from several causes. Many cases affect young people and result from small genetic mutations in key proteins. Many appear to be caused by environmental damage to the retina, perhaps at birth. Retinal degeneration causes progressive blindness in a minority of younger people (about 1 in 4,000, so 5,000 Australians and 1-2 million people wo ....This project is directed towards treatment for the blindness caused by retinal degeneration. The retina of the eye degenerates in several groups of diseases, and from several causes. Many cases affect young people and result from small genetic mutations in key proteins. Many appear to be caused by environmental damage to the retina, perhaps at birth. Retinal degeneration causes progressive blindness in a minority of younger people (about 1 in 4,000, so 5,000 Australians and 1-2 million people world-wide). This condition is known as Retinitis pigmentosa. However, the normal retinal undergoes a slow loss of photoreceptors whose effect is cumulative, so that the vision of all peoples slowly fades towards the blindness of old age. In this form, retinal degeneration affects potentially everyone. We have recently published an 'oxygen toxicity' theory of retinal degeneration to account for both retinitis pigmentosa and senescent degeneration. The theory applies whether the dystrophy is preciptated by genetic mutation or by environmental factors . By the time a person becomes aware of blindness (commonly night blindness) from retinal degeneration, the loss of vision results (it is argued) from 2 causes: the death of some photoreceptors (the retinal cells which detect light) and damage to surviving photoreceptors. Both death and damage are caused by oxygen toxicity, arising from particular features of the retina's metabolism and blood supply. Further, the relentless progression of the blindness is inherent in the mechanisms of oxygen toxicity. In preliminary work we have been able to slow retinal degenerations and, importantly, to restore function in degenerating retinas by countering the oxygen toxicity. Experiments are proposed to expand this evidence and explore the time course, permanence and generality of these effects. The tests of retinal recovery and stability, and the mechanisms of countering oxygen toxicity will be readily applicable to clinical trials.Read moreRead less