At-home contrast sensitivity test allows early detection of vision changes
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An internet-based contrast sensitivity measurement tool can help patients self-monitor vision at home, alerting them and their doctor when a visit is needed.
“Our aim in developing SPARCS was to provide an easy-to-use home-testing tool, able to detect and quantify visual loss from whatever cause, accessible to all people, independent of their language, alphabet, literacy and educational status,” George L. Spaeth, MD, director emeritus of the glaucoma service at Wills Eye Hospital, said.
SPARCS — short for Spaeth/Richman Contrast Sensitivity — was inspired by an ethical concern.
“A study performed at the John Hopkins Wilmer Institute some years ago found that 50% of the people who had glaucoma in that area, next to one of the greatest eye institutes in the world, were not diagnosed, an immoral, tragic situation, which we realized was not different in many other parts of the world,” Spaeth said.
The Tajimi Study showed that 80% of glaucoma cases are undiagnosed in Japan. A similar 71% rate was found by the Wroclaw Epidemiological Study in Poland. The Andhra Pradesh Eye Disease Study and Aravind Comprehensive Eye Survey showed that the majority of people with glaucoma, up to 90%, are undiagnosed in India.
“Our medical system pays a lot of attention to the wealthy, totally ignoring the great majority of people. That is not right and has to be changed,” Spaeth said.
With his colleague Jess Richman, MD, Spaeth and his son Eric worked on developing a sensitive testing method that would allow people to test themselves anywhere for free.
Highly related to daily life
The basis for vision is seeing boundaries, and contrast sensitivity tests how well one can see boundaries, Spaeth said. The SPARCS test uses gray vertical bars on a white background and gradually decreases the gray until it blends with the white. The contrast gratings are visualized on the computer screen in a small central area and in four larger quadrants in the periphery.
“The change in size is because neurons in the retina are packed close together in the central area. In terms of number of neurons, the small area in the center is about the same as the large areas in the periphery, so the scores that come up are comparable with each other,” Spaeth said.
While patients maintain central fixation, the gratings appear at random in different areas, and patients click where and when they see them. Both central vision and peripheral vision are assessed in this way.
There are two different forms of the same test. The quick test, which takes only 30 seconds per eye, is for gross screening to detect significant vision loss. The full test has 17 levels, is more complex and longer, and can be used to detect small changes in contrast.
Studies have shown that contrast sensitivity correlates better than visual acuity with the ability to perform daily tasks. Driving, for instance, even if visual acuity is good, is difficult and dangerous when contrast sensitivity is reduced.
“We studied this extensively in my department and developed the Assessment of Disability Related to Vision (ADREV) test in which we had people performing nine tasks, such as find boxes in a room, navigate an obstacle course, recognize faces, read signs at distance and so on. We tested them with visual acuity, visual field (VF) and contrast sensitivity and found that the correlation between the ability to perform these tasks and contrast sensitivity was much better than the correlation with VF because VF does not test central vision, and central vision is essential for most people. And it was better than the correlation with visual acuity because a person can have excellent central vision but a loss of peripheral field. Our contrast sensitivity test assesses both central and peripheral vision,” Spaeth said.
Finally, while many people in the world do not use Latin letters and not everyone is literate, contrast is universal, and everybody can recognize gratings.
Advantages of home testing, self-care
The SPARCS test is known by ophthalmologists worldwide and has been used over the past decade in numerous clinical trials in academic institutions in the U.S. and abroad. With the strong interest in telehealth fueled by the COVID-19 pandemic, home-based tools such as SPARCS have come into the limelight as a valuable addition to clinical work.
“I am a strong believer in the importance of clinical examination, but home monitoring has the potential to cut out unnecessary visits and related costs while providing a huge amount of data,” Spaeth said.
If physicians integrate it well into their practice, giving patients the instructions for self-testing in a way that is empathic, encouraging and understandable, remote monitoring can greatly improve personalized care and strengthen the doctor-patient relationship.
“Dr. Richman has been following lots of glaucoma patients at home, and many have discovered changes in their visual field long before their appointment,” Spaeth said.
A free practice test is available at sparcscontrastcenter.com. Through the same website, physicians can create their account, register their patients and monitor their at-home test results. Patients need a computer and internet connection, and they should take the test consistently, every time in the same room, with the same light conditions, sitting at a distance of 50 cm from the screen. Doctors can review patients’ test results by logging in and identifying each patient by their ID numbers.
“It is not a diagnostic test. It is not designed to diagnose a specific condition but to detect signs of vision deterioration, whatever the pathology,” Spaeth said.
The ability to accumulate vast amounts of data allows this simple test to detect trends and changes earlier and more reliably than more sophisticated technologies.
“Studies have shown that at least six VF tests are needed to be sure that a change that is seen on the test is real. Electroretinography started to become useful when the computer managed to average thousands of responses,” Spaeth said. “With SPARCS, there is no expensive technology involved, no time-consuming procedures, and you can rely on a huge amount of data.”
Finally, SPARCS is a way of encouraging patient engagement in self-care.
“No care system anywhere is going to work if it is not based on self-care. People must learn to take care of themselves, and doctors must assist them in this process,” Spaeth said. – by Michela Cimberle
- References:
- Dandona L, et al. Ophthalmology. 2000;doi:10.1016/s0161-6420(00)00275-x.
- Iwase A, et al. Ophthalmic Epidemiol. 2014;doi:10.3109/09286586.2013.867510.
- Nizankowska MH, et al. Ophthalmic Epidemiol. 2005;doi:10.1080/09286580500212904.
- Ramakrishnan R, et al. Ophthalmology. 2003;doi:10.1016/S0161-6420(03)00564-5.
- For more information:
- George L. Spaeth, MD, can be reached at Wills Eye Hospital, 840 Walnut St., Philadelphia, PA 19107; email: gspaeth@willseye.org.
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