Age-related macular degeneration (AMD) is the leading cause of severe vision loss in older Americans. AMD is a degenerative disease that affects the macula, or the central part of the retina, which has the highest density of photoreceptors, allowing for high-resolution central visual acuity. An estimated 1.75 million persons in the United States were diagnosed with AMD in 2000, an incidence that is expected to increase to nearly 3 million by 2020.[1]
There are two major forms of AMD: nonexudative ("dry") and exudative or neovascular ("wet"). Nonexudative AMD accounts for 85%-90% of all cases and neovascular AMD the remaining 10%-15%; however, the latter form is responsible for more than 80% of cases of severe vision loss or legal blindness (ie, visual acuity of 20/200 or worse) resulting from AMD.[2] The main cause of vision loss in wet AMD is the development of choroidal neovascularization (CNV), which has been shown to occur in 18% of patients over 5 years.[3]
In the early stages of AMD, patients may not experience any changes in their vision or symptoms, which may not be noticed until the disease has progressed or affected both eyes. Symptoms of AMD can vary and include blurred, distorted vision; visual scotomas; and decreased contrast and color sensitivity. With advanced dry AMD, the central visual loss and scotomas can occur over months to years. With wet AMD, the vision loss can be profound and occur within days to weeks as a result subretinal bleeding or fluid secondary to CNV.
With the advent of anti-vascular endothelial growth factor (anti-VEGF) therapy, treatment of wet AMD is now possible and is most effective when initiated promptly when CNV first develops.[4]
Wet AMD is diagnosed through scheduled dilated eye examinations or, more often, depends on patients' self-referral after visual symptoms develops. Early diagnosis and detection is key to prevent vision loss from wet AMD.[5] The conversion from dry AMD to wet AMD can occur over days to weeks; thus, home monitoring systems can improve diagnostic and treatment paradigms of AMD.
This article will discuss the existing and potential devices used to monitor and manage AMD.
Existing Home AMD Monitoring Systems
First introduced by Marc Amsler in 1947, the Amsler grid is a pattern of white lines on a black background that is used to evaluate patients with macular disease.
Amsler noted that patients with macular disease experienced visual disturbances that could be documented on the grid.[6] Owing to its low cost, ease of use, and widespread availability, the Amsler grid has been the standard means for patients to self-monitor their vision at home. However, the Amsler grid has limitations of perceptual completion and lack of patient compliance, which reduces its overall sensitivity of detecting wet AMD to < 50%.[7,8,9]
Preferential hyperacuity perimetry (PHP) uses the principle of hyperacuity or Vernier acuity to measure one's ability to distinguish misalignment. PHP is a computerized test that asks the patient to identify any misalignments, which are presented through a series of dotted lines with purposefully placed dots that are out of alignment. In a prospective case-control study comparing PHP and the Amsler grid in patients with CNV, PHP was positive in 94% of patients, compared with 34% using the Amsler grid.[10,11]
The original PHP was created for use in the doctor's office but led to the development of the ForeseeHome® AMD Monitoring Program (Notal Vision Inc.; Tel Aviv, Israel), a sensitive AMD home screening method. ForeseeHome AMD Monitoring Program has been approved by the US Food and Drug Administration (FDA) as a cloud-based home monitoring device to help patients with intermediate dry AMD detect early vision changes that may represent a conversion to wet AMD. The ForeseeHome system automatically connects to a monitoring center that sends any alerts to the patient's physician to trigger an in-office evaluation.[10]
The utility of the ForeseeHome device was validated in the HOME study,[12] conducted by the National Eye Institute. In this large multicenter clinical trial, 1520 patients at high risk for wet AMD were randomly assigned to either use of ForeseeHome device or Amsler grid monitoring. Results indicated that 94% of patients in the ForeseeHome device group maintained good visual acuity of 20/40 or better, compared with only 62% of the control group. In the patients who did convert from dry to wet AMD, those in the treatment group had a six-letter visual acuity benefit compared with the control group when starting treatment for AMD. The treatment group did so much better than the control group that this trial was stopped early for efficacy and obtained approval for reimbursement by the Centers for Medicare & Medicaid Services.
The myVisionTrack® app (Vital Art and Science; Dallas, Texas) is the second FDA-approved home vision monitoring device. Patients use the myVisionTrack app twice a week on their smartphone or tablet to test their ability to identify a unique shape. The data are then uploaded to a cloud system and analyzed by algorithms to determine whether any subtle vision changes have occurred. Per FDA guidelines, the results are sent to the physician, which can lead to a prompt in-office exam and possible treatment. The myVisionTrack app is currently being used in Genentech's phase II LADDER study investigating the sustained delivery of ranibizumab in patients with wet AMD, who can use this application to test their vision during their in-office appointment and at home. Long-term data on the use of myVisionTrack app are not yet available.
Alleye® (Oculocare Medical Inc.; Zurich, Switzerland), another mobile medical software program, has been available in Europe since 2017. In July 2018, Alleye obtained FDA approval. The software is designed to identify patients at risk for vision loss due to macular conditions, such as AMD and diabetic retinopathy, by detecting early central and paracentral metamorphopsia.
Alleye works on smartphones or tablets and asks patients to align the middle of three dots on an invisible line, a task that measures Vernier acuity or hyperacuity. The test itself takes a few minutes per eye, and the scored results are then accessible online by the patient's physician. Like the other current home-based monitoring systems, this device helps patients schedule a visit to their doctor at the "right" time so that they can be treated promptly when they have converted from dry to wet AMD or if their wet AMD has progressed.
What the Future May Hold
Optical coherence tomography (OCT) has revolutionized the diagnosis, monitoring, and management of AMD. A noninvasive imaging technique, spectral-domain OCT (SD-OCT) provides axial resolution of 5 µm and can produce in vivo "histologic sections" of the retina. The use of SD-OCT allows the detection of subclinical drusenoid change, subretinal fluid, or pigment epithelial detachments that might have been missed with slit-lamp biomicroscopy.
OCT is also invaluable in monitoring the treatment response of anti-VEGF therapy. In providing qualitative as well as quantitative data, OCT allows clinicians to measure the change in central retinal thickness, as well as monitor the distribution of intra- and subretinal fluid and the size of pigment epithelial detachments, thereby guiding treatment frequency with anti-VEGF therapy.
In light of the importance of OCT in the diagnosis and management of AMD, efforts are under way to move it from the retina specialist's office to the patient's home. Home OCT would provide several potential benefits for the monitoring and treatment of AMD. In combination with telemedicine, home OCT would allow for remote monitoring of AMD, reducing the number of necessary office visits and associated costs. Home OCT data would enable physicians to individualize treatment regimens after learning how long the anti-VEGF therapy remained effective for each patient. With this information, treat-and-extend regimens could be rapidly tailored for patients, minimizing the time they spend with active disease as well as office visits and injections.
Maloca and colleagues[13] compared a prototype home OCT, sparse OCT (spOCT), with conventional desktop OCT. The spOCT prototype provides rapid acquisition of a single-line macular OCT B-scan image in an automated fashion.
Although the device can produce high-resolution images comparable with those from commercially available desktop devices, the rapid-acquisition images appear more pixelated and grainy than conventional images. The device's central retinal thickness measurements were within 10% of reference values in 65% of images. However, roughly one third of measurements differed from reference values by more than 20 µm, which would be clinically significant in many cases. Also, although it was found to be comfortable for most patients, the device requires a patient's head to be bent forward, roughly parallel with the floor, which may be impossible for elderly patients with neck or back problems.
Although the spOCT device shows great potential, it is still in prototype form. It needs to meet the requirement of better correlation with established reference values for central retinal thickness. Patients with advanced disease would probably not be able to fixate properly for imaging on the prototype device, a problem that can be avoided by an experienced operator in the clinic setting. In addition, the limited data provided by a single-line scan would be insufficient for patients with pathology outside of fixation. In conventional OCT, many B-scan images are acquired and may be navigated by the clinician to diagnose and monitor disease outside of the fovea; such information would be unavailable with a single-line device.
Medscape Ophthalmology © 2018 WebMD, LLC
Any views expressed above are the author's own and do not necessarily reflect the views of WebMD or Medscape.
Cite this: AMD Monitoring Comes Home: The Promise of Innovative Remote Tech - Medscape - Dec 17, 2018.
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