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22 | EYEWORLD DAILY NEWS | APRIL 23, 2022 ASCRS ANNUAL MEETING DAILY NEWS D uring Friday's Glaucoma Day program, Harry Quigley, MD, gave a keynote lecture on "How research in optic nerve head dynamics will improve glauco- ma's diagnosis and treatment." Dr. Quigley first noted that glauco- ma injures retinal ganglion cell (RGC) axons, blocking transport at the lamina cribrosa. IOP affects the optic nerve head by hoop stress and translaminar gradient. We usually think mostly about the translaminar gradient as physicians, he said. The normal human lamina cribrosa connective tissue remodels by action of astrocytes. In glaucoma, the lamina deforms and widens and deepens. In human eyes, you can study with imaging, you can come down to indi- vidual beams of lamina cribrosa and count them and see how they change in glaucoma eyes. Glaucoma causes cells to fill in pores, he said. He also mentioned a histologi- cal study of human lamina cribrosa changes in glaucoma. With increasing glaucoma severity, there are more astrocytes, more microglial cells, thin- ner connective beams, smaller axonal compartments, and collagen IV fills in pores. Dr. Quigley noted how the region of the lamina with the least support strains more and causes typical RGC loss and arcuate field defects. This stresses that there's a mechanical angle going on in glaucoma. Dr. Quigley also mentioned Robert Shaffer, who observed that the cup/ disc got smaller in children when IOP lowered surgically. Dr. Quigley showed photos indicating child ONH decrease in cup/disc ratio after trabeculotomy. He then looked at measuring ONH strain by OCT live in 24 radial scans. If you were to take these scans and mark where the lamina cribrosa is, you could see, when you change the eye pressure, whether the whole thing moved, he said. Now, we've been able to measure the strain within the lamina cribrosa, specifically how much it elongates. Dr. Quigley noted a study to recon- struct the lamina from 24 radial scans, where IOP was lowered by suturelysis after trabeculotomy. This takes 3-D data and looks at individual 3-D cubes of tissue. You can look at higher and lower pressures to see how the tissue moves and calculate the stress/strain relationship. He said that the lamina expands at lower IOP after suturelysis "tensile strain." He further went into detail on OCT strain findings in 29 suturelysis eyes in study. The greater the IOP change, the greater the strain. Every eye had vertical expansion in the lamina (ten- sile strain). All had radial contraction (nerve head narrowed), and all had significant shear strain. The larger the IOP decrease, the larger the strain. Most surprisingly, Dr. Quigley said the worse the glaucoma damage in RNFL/ field, the more strain. Dr. Quigley also addressed human postmortem eye strains in normal versus glaucomatous eyes. Glaucoma lamina in mildly damaged eyes is stiff- er than normal, he said, but the worse the glaucoma, the more compliant the lamina. So in glaucoma, which is better—a stiffer eye or a more compliant eye? Dr. Quigley said a stiffer sclera causes worse glaucoma damage in mice. He noted proposed myopia treatments may be unsafe. He said that treating a glaucoma mouse with oral losartan causes much less damage. It reduces activation of TGFβ. He added that other drugs that lower blood pressure make glaucoma worse. In conclusion, Dr. Quigley high- lighted how physicians might be able to soon "try this at home," though he noted that this is only for suturelysis patients. You can add or stop an eye drop and do OCT, when approved, then 1 week later, repeat OCT and get strain measure. Physicians can predict the likelihood of future damage and deter- mine aggressiveness of IOP-lowering therapy. He added that a longitudinal, prospective study is needed to validate this. Editors' note: Dr. Quigley has no relevant financial interests. Glaucoma Day keynote lecture highlights optic nerve head dynamics Dr. Quigley gives a keynote lecture at Glaucoma Day.

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