The following is a roundup of some of the latest scientific studies on the novel coronavirus and efforts to find treatments and vaccines for COVID-19.

Changes in eyes help confirm long COVID diagnosis

Changes in nerve fibers in the eyes can help confirm a diagnosis of "long COVID" - debilitating symptoms that persist more than four week after recovery from the acute illness, according to new findings.

Because nerve fiber damage is suspected to underlie some of these lingering symptoms, ophthalmologists used a non-invasive technique called corneal confocal microscopy to check for nerve damage in the cornea.

In their study of 40 COVID-19 survivors - most of whom had not been sick enough to need extra oxygen - and 30 uninfected individuals, the researchers found "significant associations" between nerve fiber loss in the cornea and the presence and severity of long COVID symptoms related to nerves, muscles and bones.

The corneal changes were most evident in patients with persistent neurological symptoms, such as loss of taste and smell, headache, dizziness, numbness and nerve pain, according to a report published on Monday in the British Journal of Ophthalmology.

Corneas of patients with long COVID also contained more immune cells called dendritic cells, reflecting the body's response to injury.

"We believe corneal confocal microscopy ... will allow clinicians to make the diagnosis of long COVID with greater confidence," said coauthor Dr. Rayaz Malik of Weill Cornell Medicine Qatar.

Mental health issues tied to higher COVID-19 death risk

COVID-19 patients with mental health disorders are more likely to die from the virus than patients without psychiatric or cognitive diagnoses, according to two new analyses.

One study, published earlier this month in The Lancet Psychiatry, reviewed previously reported data on nearly 1.5 million COVID-19 patients.

The risk of death was roughly 75% higher in patients with substance use disorders or intellectual disabilities and developmental disorders, and it was roughly doubled in those with psychotic or mood disorders.

COVID-19 mortality risk was also linked with use of certain medications, such as antipsychotics, anxiety drugs, and antidepressants.

The other study, published on Tuesday in JAMA Psychiatry, analyzed data on more than 19,000 patients and found similar patterns. Dr. Bowen Chung of the University of California, Los Angeles, who was not involved in either study, said patients with mental health disorders tend to have other risk factors as well, such as diabetes, cardiovascular disease and respiratory disease, some of which can be linked to their medications.

"Antipsychotics in particular, have lots of metabolic effects, including obesity and high cholesterol," Chung said, and anxiety drugs can affect breathing. These individuals "also tend to have lower incomes and to not have as good access to healthcare."