Novel perimetry for identifying changes in visual field sensitivity in glaucoma

Glaucoma, a chronic, progressive, age-related degeneration of retinal ganglion cells, is characterised by a slow, irreversible loss of visual field. It is the world's leading cause of irreversible blindness, affecting approximately 500,000 people in England and Wales, and 80 million people worldwide. With an ageing population, prevalence of glaucoma is rising. The peripheral visual field is slowly lost first, often going unnoticed by patients until advanced. Perimetry, the clinical method for identifying visual field loss involves presenting stimuli (spots of light) to the retina and determining the dimmest that can be detected at multiple locations in the field. However, the current standard perimetry test was designed >40 years ago, before the disease mechanisms in glaucoma were understood. A test design that was largely imported from the predecessor of the current standard (Goldmann kinetic perimetry) when tests became more automated, and high associated measurement variability, make it difficult to identify glaucomatous loss in the first instance and detect signs of progression. In fact, it can take many years of repeated measures to identify even moderate rates of deterioration. There is a timely need to redesign perimetry with 40 years of knowledge and understanding from basic science (physiological, psychophysical) and clinical studies, as well as with more accessible and affordable technology, in order to increase accessibility to testing, detect visual loss sooner, treat sooner, and improve prognosis for vision. In this multi-disciplinary, multi-site project, we will initiate the path to translation of a novel, more evidence-based form of perimetry from the laboratory to the clinical setting on the basis of two recently discovered functional biomarkers for glaucoma. We propose a stage 1 programme of research in which we will optimise various test parameters to maximise the accuracy, precision, and efficiency of the novel test for identification of glaucomatous visual field loss.

Glaucoma is a chronic, progressive, degeneration of retinal ganglion cells, characterised by slow, irreversible loss of the peripheral visual field. Prognosis for vision is highest the earlier it is identified and treated. Perimetry, the clinical method for identifying visual field loss involves presenting stimuli (spots of light) to the retina to determine the dimmest that can be detected at multiple locations in the field. However, this technique has major limitations: a) low sensitivity to early damage, and b) high variability in moderate damage, making it difficult to identify further deterioration in those already diagnosed. The conventional test was developed >40 years ago, before the pathophysiology of glaucoma was understood, and has remained relatively unchanged since. With a design that is effectively arbitrary, it is unsurprising that glaucomatous changes are difficult to detect with the current standard clinical test. We recently discovered two functional biomarkers for glaucoma (changes in spatial and temporal summation) which will allow a redesign of perimetry for more accurate and precise measurements of changes in the visual field. In this multi-disciplinary, UK-wide, multi-site, project, we will initiate the path for translation of a novel, more evidence-based form of perimetry from laboratory to the clinical setting. This initial phase of the work will involve optimising clinical test parameters to maximise accuracy, test precision and efficiency in the novel test.