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12 | EYEWORLD DAILY NEWS | MAY 17, 2020 DAILY NEWS ASCRS VIRTUAL ANNUAL MEETING continued on page 16 Diagnostics, monitoring, and more in 'Glaucoma Essentials' symposium reported that while CCT allows for correction of IOP measure- ments, its main value is its relationship to glaucoma risk. CCT even more so than IOP, his presentation noted, predicts glaucoma development and progression. He then discussed corneal hysteresis, a measurement of the cornea absorbing and dis- sipating energy. Hysteresis, Dr. Radcliffe explained, indicates the likelihood of a cornea be- ing able to manage increasing pressure and thus the expected rate of glaucoma progression. He noted that there are dozens of peer-reviewed publications that establish corneal hysteresis as an independent indicator for risk of POAG progression. He also noted a study that estab- lished hysteresis as a risk factor for progression in NTG cases and a separate study that used hysteresis to predict response to glaucoma therapy. In one study, 68 eyes with OAG were assessed with corneal hyster- esis and IOP before selective laser trabeculoplasty (SLT) and Goldman applanation to- nometry is considered the gold standard for measuring IOP via applanation tonometry, but Dr. Radcliffe discussed devices that conduct other types of tonom- etry as well, including those in categories of dynamic contour tonometry, non-contact or air-puff tonometry, electronic indentation tonometry, pneu- motonometry, and impression tonometry. He mentioned the CATS (Correcting Applanation Tonometry Surface) Tonome- ter Prism (CATS Tonometer), which was FDA approved in 2018. This device was de- scribed as allowing for more accurate IOP measurement with less influence from cor- neal thickness, hysteresis, tear film, and corneal curvature. Pachymetry uses ultra- sound to measure corneal thickness. A healthy eye has a mean central corneal thickness (CCT) of about 545 μm, and thicker corneas can lead to an overestimated IOP and thinner CCT an underestimated IOP. Dr. Radcliffe described CCT as a key glaucoma variable. He migraines, and Raynaud's phenomenon. Dr. Shukla also noted the Collaborative Nor- mal-Tension Glaucoma Study published in 1998, which found that IOP lowering of 30% or more in NTG patients reduced their 5-year risk of visual field progression from 35% to 12%. • Ocular hypertension: It's thought 4–7% of U.S. adults older than 40 have ocular hypertension, which is char- acterized by an IOP of more than 21 mm Hg without dis- cernable gonioscopy findings or visual field/retinal nerve fiber layer defects. According to the Ocular Hypertension Treatment Study, lowering IOP by 20% in this group re- duced glaucoma risk by 50%. • Secondary open angle glaucoma: Two types of secondary angle glaucoma conditions mentioned by Dr. Shukla included pseu- doexfoliation glaucoma and pigmentary glaucoma. • Primary angle closure glauco- ma: Dr. Shukla discussed the classification from primary angle closure suspect to ac- tual angle closure to primary angle closure with evidence of glaucoma. • Secondary angle closure glaucoma: This includes two common types—neovascular glaucoma and ciliochoroidal effusions—and others that are less common, such as ma- lignant glaucoma, persistent fetal vasculature, retinopathy of prematurity, iridocorne- al endothelial syndrome, epithelial and fibrous down- growth, and lens-induced. Nathan Radcliffe, MD, New York, New York, discussed how glaucoma cases are examined/ monitored, focusing on gonios- copy, elevated IOP, and central corneal thickness and hyster- esis. by Liz Hillman Editorial Co-Director A symposium gave view- ers a comprehensive overview of glaucoma, from the basic disease states to diagnostics and moni- toring progression to treatment options. Aakriti Shukla, MD, Philadelphia, Pennsylvania, presented on the definition and classification of glaucoma. Glaucomatous optic neurop- athy showcases as vertical elongation of the cup, thinning or notching of the neuroretinal rim, retinal nerve fiber layer loss, disc hemorrhage, and changes that are progressive. Patients experience patterns of visual dysfunction that includes a loss of vision in the mid-periphery, though some- times centrally, and it's often asymmetrical along the hori- zontal midline. Glaucomatous damage can occur at all levels of untreated IOP; IOP is not the only modifiable risk factor. Dr. Shukla went on to define the different types of glaucoma: • Primary open angle glauco- ma (POAG): This type, she said, accounts for two-thirds of all glaucoma cases, and shows an open anterior chamber angle. It is usually bilateral but often presents asymmetrically. Risk factors include age, race, family history, and a thin central corneal thickness. • Normal tension glaucoma (NTG): Dr. Shukla noted that it's unclear if this is truly a distinct disease from POAG. The visual field defects are often closer to fixation and deeper than POAG. Its prev- alence is higher in patients of Asian descent, those with vasospastic disorders, auto- immune diseases, history of Dr. Radcliffe describes various examinations and measures for glaucoma. Viewing the angle with gonioscopy can help determine whether it's open or closed. Source: Nathan Radcliffe, MD, screenshot from presentation

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