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    Improvements in detecting and measuring glaucoma round out 2015

    Powerful imaging allows researchers to examine glaucoma-neurological disorder link

     

    As 2015 progressed, researchers reported better ways to detect glaucoma, measure the damage it is causing, and understand how that damage is affecting their patients’ lives. No single innovation revolutionized the profession, but a wide range of technologies became more available to clinicians.

    Electrophysiology

    One of the newest diagnostic measures becoming available to clinicians is the use of visual evoked potentials (VEP) and electroretinography (ERG). These two techniques, collectively known as electrophysiology, can help account for unexplained scores on visual field examinations in patients whose IOP is normal and whose retinal nerve fiber layer also appears normal.

    VEP uses sensors placed on the patient’s head to track electrical activity from the retina to the visual cortex. The amplitude of the signal reveals the number of healthy retinal cells and the patient’s ability to discriminate between different-sized objects. In the clinic, low-contrast VEP protocol could help identify patients who have normal achromatic perimetry, but structural abnormalities consistent with glaucoma.

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    ERG also detects the size and speed of the electrical signal, but through the retinal ganglion cells rather than the optic nerve. ERG results can detect early states of glaucoma before the onset of visual field defects and before retinal nerve fiber loss shows up on optical coherence tomography (OCT).

    Researchers have used these techniques for a long time, but the size and expense of the equipment made it impractical for use in private practice. Now some manufacturers are bringing this technology to the clinic. Diopsys has led the pack with its Nova cart system. And in November, the company launched its Argos, intended to provide the same visual electrophysiology suite in a tabletop version. 

    Contrast sensitivity

    Contrast sensitivity, too, is making strides.  Researchers at Wills Eye Hospital at Jefferson Medical College in Philadelphia have developed the Spaeth/Richman contrast sensitivity test (SPARCS), which can be used through the internet making it available to patients at home.

    In a study reported in January, these researchers showed the test could detect patients with glaucoma with 79% sensitivity and 93% specificity, which compares well to accuracy of the Pelli-Robson, a standard method of measuring contrast sensitivity. Because of its high reproducibility, the SPARCS could also measure disease progression in an individual patient.

    Monitoring changes in IOP over the course of a day can also yield useful findings. The Sensimed Triggerfish uses a soft disposable silicone contact lens with an embedded micro-sensor to capture spontaneous circumferential changes at the corneoscleral area. In May, researchers reported that the system compared well to the pneumatonometer and may be practical for detecting sleep-induced IOP changes. 

    Relative afferent pupillary defect

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