According to a new study, the idea that your pupils dilate when aroused is no popular myth.
Researchers from Cornell University used a specialized infrared lens to measure the changes to individuals' eyes while they watched erotic videos.
The study published in the scientific journal PLoS ONE, noted that a person's pupils widened most to videos of people who participants found attractive.
Pupil dilation could thereby reveal where participants were on the sexual spectrum from heterosexual to homosexual.
A person's pupils dilate when they are aroused
In a statement, researchers said that until now there was no scientific evidence that sexual orientation could be revealed by pupil dilation to attractive people.
Previous research explored these mechanisms either by simply asking people about their sexuality, or by using physiological measures such as assessing their genital arousal. These methods, however, come with substantial problems.
Find out what else your eyes reveal about you... BELOW
"We wanted to find an alternative measure that would be an automatic indication of sexual orientation, but without being as invasive as previous measures. Pupillary responses are exactly that," says Gerulf Rieger, lead author and research fellow at Cornell, in a statement.
"With this new technology we are able to explore sexual orientation of people who would never participate in a study on genital arousal, such as people from traditional cultures. This will give us a much better understanding how sexuality is expressed across the planet."
The pupils (the black circle in the centre of the eye) in normal people are usually symmetrical, the same size and react in the same way when exposed to sunlight. If one pupil is bigger or smaller than the other, there could be an underlying medical problem. Experts claim that differences in pupil size could indicate that the person is at a higher risk of having a stroke, brain or optic nerve tumour, or brain aneurysm. If you spot any changes to your pupils, raise this with your GP, optometrist or ophthalmologist.
If your eyes are always dry and ultra sensitive to light, it could signal an immune system disorder, Sjogren, which impairs the glands in the eyes and mouth. The condition affects women over 40 with autoimmune disorders, such as rheumatoid arthritis or lupus. Seek advice from your GP if this sounds like you, as artificial lubricant can be prescribed and you'll be advised to drink plenty of water. "Dry eyes are more common in women over 50 due to hormonal changes," adds Larry Benjamin from The Royal College of Ophthalmologists.
If your eye is covered in a 'cloud' and your vision is impaired because of it, you may have a cataract. This causes a clouding of the lens inside the eye and can be corrected with surgery. This condition mainly occurs in older people but in younger people, it is commonly caused as a side effect of diabetes, tumours and some medication.
Although there are many things that can cause itchiness around the eyes, the most common reason could be pinpointed to an allergic reaction. The eye, and the area around it, is delicate and sensitive and more vulnerable to infections and allergies. Triggers could be anything from airborne pollens, dust or animal fur. If you suffer from red itchy eyes, try antihistamines to ease the redness, or visit your GP to organise an allergy test. If your eye and eyelids become puffy and sore, this could be a sign that you're sleep deprived. "Fluid moves around your head when you sleep and normally disperses when you wake from a good night's sleep. "However, lack of sleep causes this fluid to retain around the eye area for longer," explains Larry Benjamin from The Royal College of Ophthalmologists.
If your eye has a light grey ring around the cornea (the coloured circle in your eye), you may have a condition called arcus senilis, which is often linked to high cholesterol levels and triglycerides - fatty acids found in the blood. These are linked to higher risk of heart disease and strokes, so if you spot a grey ring circling your eye, visit your GP to discuss changing your diet.
Although it's natural for eyebrows to become thinner as we age, if you notice your brows literally 'disappearing' from the outer third of the eyebrow, this could signal a thyroid dysfunction. Loss of eyebrow hair from the outer edges of your face is a common sign of hyperthyroidism (overactive thyroid) or hypothyroidism (under active thyroid). Thyroids help regulate the metabolism and thyroid hormones are vital for hair production. If in doubt, book an appointment with your GP.
"Watery eyes can indicate infection," explains Larry Benjamin from The Royal College of Ophthalmologists. "If the eye is watery, you've most likely got an infection caused by a virus. If it's sticky, you might have a bacterial infection." If your vision becomes blurry, this could also be the result of Computer Vision Syndrome (CVS), caused by eyestrain from lack of contrast on a computer screen. This makes the eyes work harder focusing on the pixels on the screen. If in doubt, speak to your employer about booking an eye test, which is free if you use visual display units (VDU) for long periods of time.
Yellow lumps, also known, as xanthelasma palpebral, which appear on your eyelids could be a warning signal that your cholesterol levels are sky high. These are fatty deposits, which clump together and live in the eyelid. These are very often mistaken for a stye. Although these are quite common, it's best to get them checked by your optician or GP, as it can sometimes be an early sign of coronary artery disease. If you spot any coloured spots on your eyelids, in particular brown spots, visit your GP immediately as it could be an early sign of skin cancer. These usually appear on the lower part of the eyelid and will look a brownish colour with tiny blood vessels.
If your eyes are always blood-shot with broken blood vessels making them look blotchy and sore, this could be a sign that you have high blood pressure. Your optician will be able to confirm this by looking at your retina (the inner part of the eye). High blood pressure causes the blood vessel in the retina to 'kink and twist', causing them to break and look red. This could increase your risk of a stroke, so raise it with your GP as soon as possible.
If the whites of your eyes have a yellow tint rather than pearly white, you may have jaundice, which is linked to various liver and gall bladder problems. A simple blood test will confirm this, so if you're in doubt, book an appointment with your GP.
The new Cornell study adds considerably more to the field of sexuality research than merely a novel measure.
As expected, heterosexual men showed strong pupillary responses to sexual videos of women, and little to men; heterosexual women, however, showed pupillary responses to both sexes.
This result confirms previous research suggesting that women have a very different type of sexuality than men.
Moreover, the new study feeds into a long-lasting debate on male bisexuality. Previous notions were that most bisexual men do not base their sexual identity on their physiological sexual arousal but on romantic and identity issues.
Contrary to this claim, bisexual men in the new study showed substantial pupil dilations to sexual videos of both men and women.
"We can now finally argue that a flexible sexual desire is not simply restricted to women – some men have it, too, and it is reflected in their pupils," says co-author Ritch Savin-Williams.
"In fact, not even a division into 'straight,' 'bi,' and 'gay' tells the full story. Men who identity as 'mostly straight' really exist both in their identity and their pupil response; they are more aroused to males than straight men, but much less so than both bisexual and gay men," Savin-Williams notes.Here are more tips on how to find out if someone's straight or gay...