Hello again, dear readers. We hope you've been having an enjoyable summer and that our recent columns about sunscreen, ticks and mosquitos have come in handy. We've been hearing from a lot of you and, as always, you've given us great information to share, as well as a few things to clarify.
• Let's start with the column about floaters. Those gently drifting specks and strands some of us get in our field of vision generated quite a few letters. Some were sweet thank-you notes, to which we say, thank you for reading the column! And a few disagreed with the idea that, over time, one's brain will adjust and "ignore" floaters.
A reader from Baker, Louisiana, put it most succinctly: "Every time I read an article or hear a doctor say that given time, 'your brain will tag floaters as unimportant information and, for the most part, will let you forget them,' I have to laugh. Laugh through gritted teeth, to be sure, but laugh nonetheless."
Some of you wrote with questions regarding the newest research into the use of lasers to reduce or remove floaters. It's an intriguing area of study, and we will look into it for you in the future.
In that same column, we stated that a sudden increase in floaters, when accompanied with flashes of light, could indicate a serious problem. In answer to the reader who (very politely) took us to task for not specifying what that problem might be, the answer is that it may indicate a retinal detachment. That's why, as we said, that set of symptoms means it's very important to check in with your eye doctor.
• After publication of our column about yellow fever, we heard from many world travelers who want to know whether they need to get re-vaccinated. We have good news. According to guidelines updated by the World Health Organization in 2013, a single primary dose of the yellow fever vaccine gives lifelong protection. A booster dose of the vaccine is not needed. The Centers for Disease Control and Prevention have adopted the WHO recommendations.
• After our column about testing for prostate cancer, a reader asked for information about the IsoPSA test. This is a new test and it is now undergoing additional study. Initial findings suggest that the IsoPSA may be more precise than the existing prostate antigen test at distinguishing cancer from benign conditions, and in identifying patients who are at higher risk of developing the disease. We'll keep an eye on future developments.
• Finally, thank you to all of you astronomers who let us know that the most recent total solar eclipse in North America was actually more recent than what our column stated. An excerpt from one of the letters:
"There was a total eclipse in Canada in February of 1979 and I know that because I was visiting my parents in Winnipeg, Manitoba, at the time and was very blessed to witness the total eclipse at approximately 9:30 a.m. It was an amazing sight, corona and all."
As ever, thank you for taking the time to write to us. We know we are fortunate to have readers like you.