Written by Olivia Kingston

Glaucoma is the leading cause of irreversible blindness worldwide (1). As patients age, cells in the eye gradually deteriorate, causing patients to eventually go completely blind. Scientists at Liverpool University believe that by replacing these non-working cells with working ones, vision loss may be prevented!

What’s happening in glaucoma?

how glaucoma works
Figure 1. Pathophysiological changes in the eye as a result of elevated pressure in glaucoma. A schematic diagram showing how elevated intra ocular pressure in glaucoma puts pressure on the lamina cribrosa, causing tissue deformation and damage to optic nerve axons. Image based upon description and diagrams in Quigley, 2011.

Our eyes are filled with fluid, known as aqueous humour, that is constantly filtered by a tissue called the trabecular meshwork (2). In glaucoma, the cells that make up this tissue decrease in numbers and those remaining don’t function as they should do (3). This prevents the fluid from moving through the meshwork as it becomes stiffer and blocked by debris, causing pressure in the eye to increase (4). This pressure damages axons of the optic nerves preventing signals that contain visual information being sent to the brain (5).

Treating Glaucoma Today

Currently glaucoma treatments involve laser treatments or surgery to create channels for the fluid to drain out of the eye and reduce pressure, which unfortunately aren’t always effective (6). If the lost cells of the trabecular meshwork in glaucoma patients could be replaced with healthy cells, then the trabecular meshwork may be able to function normally and regulate pressure in the eye.

schematic diagram illustrating the pathway of aqueous humour. Important in regulating pressure in the eye.
Figure 2. The main aqueous humour outflow pathway via the trabecular meshwork into Schlemm’s canal. A schematic diagram showing the outflow pathway of aqueous humour. Aqueous humour is created at the ciliary body and flows into the anterior chamber and through the trabecular meshwork. Image and information from in Goel et al., 2010.

Hiding in plain sight?

The problem lies in how to develop these working cells and get them to where they need to be? Well, recent scientific discoveries find that these cells may be “hiding in plain sight”.

By changing the environment in the trabecular meshwork, we may be able to make use of cells already present in the eye, that have a unique ability to develop into specialised cell types, stem cells (7). In the right conditions, these stem cells can be encouraged to grow into healthy and functioning cells that could aid in aqueous humour outflow. What scientists need to know, is what changes are needed to make this happen…and that’s what is currently being investigated at Liverpool University!

Think of it like gardening. Flower seeds buried deep in dry and old soil, won’t blossom anytime soon. But if you replace the soil with fresh, nutritious compost and plenty of water you’ll have a flourishing garden. By finding the right compost and supplying water, scientists can replace non-working cells with healthy ones, without having to transplant new cells into patients.

Olivia Kingston is a PhD student studying glaucoma.

References

  • Liu, B. et al. (2018) ‘Aging and ocular tissue stiffness in glaucoma’, Survey of Ophthalmology. Elsevier USA, pp. 56–74. doi: 10.1016/j.survophthal.2017.06.007.
  • Tamm, E. R. (2009) ‘The trabecular meshwork outflow pathways: Structural and functional aspects’, Experimental Eye Research. Academic Press, pp. 648–655. doi: 10.1016/j.exer.2009.02.007.
  • Liton, P. B. et al. (2005) ‘Cellular senescence in the glaucomatous outflow pathway’, Experimental Gerontology. NIH Public Access, 40(8–9), pp. 745–748. doi: 10.1016/j.exger.2005.06.005.
  • dysregulation in glaucoma’, Experimental Eye Research. Academic Press, pp. 112–125. doi: 10.1016/j.exer.2014.07.014.
  • Quigley, H. A. (2011) ‘Glaucoma’, The Lancet, 377(9774), pp. 1367–1377. doi: 10.1016/S0140-6736(10)61423-7.
  • Weinreb, R. N., Aung, T. and Medeiros, F. A. (2014) ‘The pathophysiology and treatment of glaucoma: A review’, JAMA – Journal of the American Medical Association. American Medical Association, pp. 1901–1911. doi: 10.1001/jama.2014.3192.
  • Yun, H. et al. (2016) ‘Stem cells in the trabecular meshwork for regulating intraocular pressure’, Journal of Ocular Pharmacology and Therapeutics. Mary Ann Liebert Inc., 32(5), pp. 253–260. doi: 10.1089/jop.2016.0005.
  • Goel et al. (2010) ‘Aqueous Humour Dynamics; A Review’, The Open Opthamology Journal. 4(1) pp 52-9. doi: 10.2174/1874364101004010052.

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