Why do humans and other mammals have eyelashes?
Experts have been batting rival theories around for years.
Eyelashes are dust catchers, snaring things that would otherwise drift into the eye, went one idea.
Or they were sensors, acting like a cat's whiskers, to warn the eye of wind-borne grit or other dangers, according to another hypothesis.
Some suggested that eyelashes were for expression -- to enhance the impact of the eye for communication or sexual allure.
In fact, said a team of biologists Wednesday, the answer is this: eyelashes direct airflow around the eye to shield it from airborne particles, bacteria, viruses and mites.
And they prevent the protective coating of tears on the eyeball -- a mix of mucus, oil and water -- from drying out.
Unlike the hairs in the nose and airway, which act as physical traps, eyelashes act as "a passive dust-controlling system," found the study headed by researcher David Hu at the Georgia Institute of Technology in the American city Atlanta.
"They reduce evaporation and particle deposition by up to 50 percent."
Delving into the enigma, Hu's team measured the lashes of 22 mammal species, from hedgehogs to humans.
In all of them, the length of the eyelash was about one-third of the width of the eye, the probe found -- optimal for minimising airflow over the eye surface without obstructing vision.
The rule applied even when a species, like the giraffe, has multiple layers of lashes to cope with a dusty, arid environment.
With engineering help, the researchers next built a small wind tunnel with a replica of the mammalian eye on one end.
The fake eye consisted of a two-centimetre (0.8-inch) dish with a thin coat of water surrounded by imitation eyelashes.
The wind was set at walking speed, directed at the "eye".
The team found the eyelashes directed airflow away from the dish, preventing evaporation of the test fluid and deflecting particles.
The experiments back medical observation that people who lack eyelashes have a higher risk of optical infection caused by so-called dry eye.
Other intriguing research has found that children with allergies have 10 percent longer and denser lashes compared to those without.
The reason: specialised cells in the eyelid respond to irritants by releasing a compound called prostaglandin, which increases hair growth to protect the eye.
False eyelashes could be a weapon against "dry eye," suggests the study.
And the simple, easy-to-clean design could inspire industrial design.
Eyelash-inspired screens may one day protect photovoltaic solar panels, which lose six percent in efficiency per year because of dust buildup on their surface, said the paper.
The findings were published in the Journal of the Royal Society Interface.
AFP
Wed Feb 25 2015
Other intriguing research has found that children with allergies have 10 percent longer and denser lashes compared to those without.
Who is Prabowo Subianto, incoming president of Indonesia?
A wealthy ex-general with ties to Indonesia's popular outgoing president and its dictatorial past, looks set to be its next leader.
Iran's supreme leader says Hamas leader's death will not halt 'Axis of Resistance'
The "Axis of Resistance", built up with years of Iranian support, includes Hamas, the Lebanese Hezbollah group, the Houthi movement in Yemen, and various Shi'ite groups in Iraq and Syria.
Putin says Russia willing to seek compromises between Iran and Israel
Russia is ready to help seek compromises between arch-foes Israel and Iran, President Vladimir Putin said on Friday, saying these would be difficult but possible.
What proposals will Russia push at the BRICS summit?
The proposal is also to establish a BRICS reinsurance company to allow uninterrupted shipment of goods and key commodities between members.
Indonesia's free meals plan in the spotlight as Prabowo readies for office
Prabowo calls the programme one of the main drivers of economic growth, eventually set to add an estimated 2.5 million jobs.
Astro AWANI's revamped English news website, AWANI International, launches on Oct 21
Astro AWANI's revamped English platform delivers in-depth global news and expert analysis to keep you informed on key developments.
Israeli strikes kill 33 people in Jabalia refugee camp in Gaza, medics say
Residents of Jabalia said Israeli tanks had reached the heart of the camp after pushing through suburbs and residential districts.
Liam Payne's ex-partner calls for media restraint after 'painful' death
Cheryl Tweedy used her statement to urge the media to remember they had a seven-year-old son, Bear, who could read the reports.
Analysts: Indonesia's strong MoF leadership team to boost investor confidence
Sri Mulyani Indrawati as head of Indonesia's Ministry of Finance is expected to instil confidence among investors.
Biden offers both a carrot and a stick to Israel as his term nears an end
Israel has frequently resisted US advice and has caused political difficulties for the Biden administration.
Putin says BRICS will generate most of global economic growth
Russian President Vladimir Putin will host a summit of the group in the city of Kazan on Oct. 22-24.
ISIS Malaysia's perspective of Budget 2025
An excellent rakyat-centric budget under the overarching principle of a caring and humane economy.
Budget 2025: Record increase in STR, SARA aid initiatives
The government will provide a significant boost to the Sumbangan Tunai Rahmah (STR) and Sumbangan Asas Rahmah (SARA) initiatives next year.
Budget 2025: EPF contributions to be made mandatory for foreign workers – PM Anwar
The government plans to make it compulsory for all non-citizen workers to contribute to the Employees Provident Fund (EPF).
What policies to expect from Indonesia's new President Prabowo
Prabowo will be open to foreign investment, his aide has said, such as by offering investors management of airports and sea ports.
Budget 2025: Govt allocates RM470 mil to empower women's participation in PMKS
The Women's Leadership Apprenticeship Program will be intensified as an effort to produce more female corporate personalities.
Israel sends more troops into north Gaza, deepens raid
Residents of Jabalia in northern Gaza said Israeli tanks had reached the heart of the camp, using heavy air and ground fire.
Indonesia ramps up security ahead of Prabowo's inauguration
Prabowo Subianto will be sworn in as Indonesia's president on Sunday with Vice President-elect, Gibran Rakabuming Raka, also taking office.
Immediate allocation of RM150 mil for local authorities, DID to tackle flash floods
Datuk Seri Anwar Ibrahim said this allocation is intended to address the recent flash floods that hit the capital and several major towns.
Budget 2025: Sabah, Sarawak to continue receiving among highest allocations - PM
Sabah and Sarawak continues to be prioritised under Budget 2025, with allocations of RM6.7 billion and RM5.9 billion respectively.