In a study published in this week’s PLoS ONE (October 24, 2007) they demonstrate that a compelling visual illusion known as the induced twinkle after-effect (TAE) can accurately identify the location and breadth of actual blind spots in people with retinal disease. The twinkle after-effect is a “twinkling” that people can see in a blind spot when they stare at a blank screen after staring at a noisy visual target such as a detuned television screen.
“Our hope is that we can make this simple technique available online or on a DVD,” says Dr. Peter Bex, associate scientist at Schepens Eye Research Institute and the principal investigator of the study. “This will be particularly helpful with patients who have glaucoma, diabetic retinopathy or macular degeneration where early detection of changes in vision can impact the effectiveness of treatments.”
According to Bex, many people fail to seek help when they develop blind spots in their vision, because their brains automatically compensate or “fill in” the missing information in their visual field. Since everyone has a blind spot where the optic nerve meets the retina, this perceptual “fill in” process is useful for normally sighted people, allowing them a complete visual image. “But this innate process can mask the effects of serious disorders such as diabetic retinopathy and glaucoma and keep sufferers from seeking help until the vision loss is very serious or they bump into objects they can no longer see.”
The traditional gold standard method for detecting blind spots (scotomas) is very expensive and time consuming and must be done in an ophthalmologist’s office. The technique known as retinal specific microperimetry is a diagnostic tool that costs nearly 50 thousand dollars and requires specialized training to apply.
In 1992 scientists became aware of what they eventually named the “twinkle after effect.” They discovered that when someone looks at a television screen filled with static noise while covering part of their visual field with a small patch, the formerly patched area is left with a twinkling sensation after the noise is turned off and the person looks at a blank screen. The rest of the visual field does not experience the twinkling effect, which was described by one patient as resembling a moving cumulous cloud. “While this discovery was intriguing, it wasn’t clear how it could be used for patients,” says Bex.
In the past several years, Bex and his team began to understand its potential. “We theorized that if people with blind spots stared at a noisy screen, the blind areas would “twinkle” when the screen was turned off and their eyes focused on a blank screen. These ‘twinkling’ blind spot areas could then easily be mapped,” he says.
To test their theory, Bex and his team asked eight patients with macular degeneration to undergo the retinal specific microperimetry test and his “twinkling after-effect” test. The team provided a blank touch screen--after the noisy screen--so patients could outline the twinkling areas with their finger.
The team found that the results of the two tests matched in 75 percent of cases, and visual defects could be detected in areas that are not accessible to conventional microperimetry, confirming his belief that TAE could be used diagnostically. “This tool cannot replace the more sophisticated technique but we believe it is a powerful, simple tool that patients can use daily in the privacy of their home to detect any changes in their vision,” he says. “If a patient detects a change, his or her physician can then study it more closely and offer therapy.”
While the results of this small study are very encouraging, Bex says the next step is to do a larger clinical study.
Ultimately Bex sees this type of test being free to the public on the Internet or distributed through a public health entity. “We really believe this could have a great impact on the visual health of the community,” says Bex.
Other members of the study team are Michael D. Crossland and Steven C. Dakin of the UCL Institute of Ophthalmology, London, UK.
Schepens Eye Research Institute is an affiliate of Harvard Medical School and the largest independent eye research institute in the world.
Andrew Hyde | alfa
Biofilm discovery suggests new way to prevent dangerous infections
23.05.2017 | University of Texas at Austin
Another reason to exercise: Burning bone fat -- a key to better bone health
19.05.2017 | University of North Carolina Health Care
Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.
The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....
An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.
We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...
Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.
Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...
An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...
In the race to produce a quantum computer, a number of projects are seeking a way to create quantum bits -- or qubits -- that are stable, meaning they are not much affected by changes in their environment. This normally needs highly nonlinear non-dissipative elements capable of functioning at very low temperatures.
In pursuit of this goal, researchers at EPFL's Laboratory of Photonics and Quantum Measurements LPQM (STI/SB), have investigated a nonlinear graphene-based...
23.05.2017 | Event News
22.05.2017 | Event News
17.05.2017 | Event News
24.05.2017 | Life Sciences
24.05.2017 | Life Sciences
24.05.2017 | Physics and Astronomy