It has long been thought that blindness after brain lesions is irreversible and that damage to the optic nerves leads to permanent impairments in everyday activities such as reading, driving, and spatial orientation. A new study published in Elsevier’sBrain Stimulation suggests that treating such patients with low levels of non-invasive, repetitive, transorbital alternating current stimulation (rtACS) for 10 days (30-40 min per day) significantly reduces visual impairment and markedly improves vision-related quality of life.

The authors reported eye exam findings in seven astronauts as well as an analysis of post-flight questionnaires regarding in-flight vision changes in approximately 300 additional astronauts. The seven astronauts with ocular anomalies had returned from long-duration space missions to the International Space Station (ISS) and all seven subjects had undergone complete eye examinations, including dilated exams and photographs of the back of the eye. Several had MRI scans, spinal taps, and computerized analysis of their optic nerve. After 6 months of space flight, all 7 astronauts had eye findings, including swollen optic nerves, distortion of the shape of the eyeball, and retinal changes. Most became more farsighted, and had blurred vision, especially at near. The spinal taps showed either top normal or slightly elevated pressures in the spinal fluid surrounding the brain and optic nerves.
The 300 post-flight questionnaires documented that approximately 29% and 60% of astronauts on short and long-duration missions, respectively, experienced a worsening of distance or near visual acuity. Some of these vision changes remain unresolved years after flight. The authors theorized that changes may have resulted from fluid shifts brought about by prolonged exposure to low gravity. The findings might represent parts of a spectrum of ocular and brain responses to extended exposure to low gravity. Future research is ongoing for astronauts entering new missions. 

When we gaze at a shape and then the shape disappears, a strange thing happens: We see an afterimage in the complementary color. Now a Japanese study has observed for the first time an equally strange illusion: The afterimage appears in a “complementary” shape – circles as hexagons, and vice-versa.

“The finding suggests that the afterimage is formed in the brain, not in the eye,” the author, Hiroyuki Ito of Kyushu University, wrote in an email. More specifically, the illusion is produced in the brain’s shape-processing visual cortex, not the eye’s light-receiving, message-sending retina. The findings appear in an upcoming issue ofPsychological Science, a journal published by the Association for Psychological Science.