'Eye' Spy with My Little Eye... Quiz

Answer: retina

The retina is the light-sensitive layer of tissue at the back of the eye, made up of a variety of cells called rods and cones. Light entering the eye is projected onto the retina, which then translates it into signals to be sent to the brain.

Damage to the retina, including tears or retinal detachment, can cause blindness if it cannot be repaired - therefore getting speedy medical treatment if you suspect a problem is really important. There are also a variety of diseases that can cause problems with the retina, such as macular degeneration (a gradual deterioration of the nerve endings in the retina) and diabetic retinopathy (which damages the blood vessels in the eye).

Answer: cornea

The cornea is the transparent 'cover' over the front of the eye that also plays a crucial role in providing the focus necessary for clear vision. Refractive 'laser' eye surgery to correct sight problems usually involves reshaping the cornea to change the focus.

If your cornea becomes damaged then various surgical repairs are available, although serious cases can require a transplant. The replacement of an entire cornea is known as penetrating keratoplasty and generally requires tissue from a deceased donor. The first successful recorded transplant was carried out in 1905 by the Czech doctor Eduard Zirm and it is now estimated that around 100,000 procedures take place every year worldwide.

Answer: pupil

The pupil is the aperture through which light enters the eye and is visible as a black circle surrounded by the coloured iris. When there is a lot of light (and particularly if someone shines a bright light into your eye) the pupil will constrict to reduce the amount of light entering the eye to maintain vision and protect the retina. By contrast, in a dark room, the pupil will expand to try and get as much light into the eye as possible.

The reactions of your pupils to various stimuli can also be an important health indicator. If the pupils are of unequal size or do not react appropriately to light, this can suggest a problem in the brain. In the most dramatic example of this, pupils that are fixed and dilated can be indicative of the fact that a person is dead.

Answer: eyelash

Having any sort of eel (ashy or otherwise) in your eye would be a particularly strange and probably extremely painful experience. However, getting an eyelash stuck in your eye is relatively common and usually easily resolved by rinsing out the eye or waiting for the offending hair to drift out of the eye naturally during sleep.

However, eyelashes are not just a decorative addition to your eyelid, waiting menacingly to invade your eyes. They actually play an important role in protecting the eye from dust and are sensitive enough to act as an early warning system that a foreign object is getting too close to the eye.

Answer: vitreous humour

The vitreous humour (otherwise known as the vitreous or the vitreous body) is a gel-like solution that fills the space in the eyeball between the lens and the retina and is responsible for ensuring that the eyeball is a 'ball' rather than some sort of slumped, flat shape.

Your vitreous humour is something that you can't see and generally won't notice. However, if any other cells such as blood or fluid get into it then they can be seen as 'floaters'. People with significant myopia (short-sightedness) are more likely to develop floaters, which are essentially harmless but can become irritating as they 'float' across the field of vision.

Answer: optic nerve

The optic nerve (or second cranial nerve) is part of the central nervous system and provides a conduit for signals to pass between the eye and the brain.

Sadly, like many other parts of the central nervous system such as the spinal cord, damage to the optic nerve is often permanent and can result in a severe loss of vision or total blindness in the affected eye. The most common conditions that result in damage to the optic nerve include glaucoma, anterior ischemic optic neuropathy (a 'stroke' of the optic nerve) or optic neuritis (inflammation of the optic nerve).

Although the structure of a pig's eye and optic nerve bears some similarity to that of humans, I wouldn't recommend consulting a vet about your own eyes - let alone a porcine one.

Answer: spectacles

The history of spectacles (aka eyeglasses or just glasses) dates back to 13th century Italy, although the identity of the actual inventor is not known. Early designs involved two lenses in a frame that needed to be held in front of the eyes, but the more modern design involving metal legs to hook over the ears can be seen in paintings dating from around the 16th and 17th centuries.

Despite their similarity in appearance to ancient designs, modern spectacles are made from a wider variety of materials and are capable of correcting a wider range of vision defects. Concave lenses to correct short-sightedness were developed in the 15th century, bifocals are believed to have been invented by Benjamin Franklin in the 18th century and lenses to correct astigmatism were developed in 1825 by George Airy, a British astronomer.

Answer: pink eye

Pink eye is another name for conjunctivitis - the inflammation of the conjunctiva (the outer surface of the eye and the inner surface of the eyelid). Unsurprisingly, the colloquial name for the condition comes from the characteristic redness that is one of the main symptoms.

Conjunctivitis is generally caused by a viral infection, bacterial infection, allergic reaction or a chemical injury to the eye. However, there are also other infectious types of conjunctivitis that particularly affect newborn babies.

Answer: contact lens

Contact lenses are thin lenses placed directly in contact with the eye - hence the name I suppose! They are primarily used for correcting vision (as a much more discreet option compared to spectacles) but can also be applied for cosmetic purposes, such as changing the colour or appearance of the eye, or medical purposes (for example if part of the iris is damaged).

The first contact lenses designed specifically to correct vision were made in 1888 by a German ophthalmologist named Adolf Fick and produced from brown glass. Modern lenses now tend to be made from either oxygen-permeable polymers (rigid lenses) or silicon hydrogels (soft lenses) and are available in a range of different types from daily disposables to those designed to be worn for up to a month.

Answer: tears

Although tears are produced in a variety of emotional situations, their primary physiological purpose is to lubricate the eye or to clean and remove debris from it. Despite what you might think, tears are not solely formed from water, but also include a selection of proteins and minerals (such as mucins, glucose and salt) and technically count as part of the immune system.

Tears produced to lubricate the eye are often referred to as basal tears, while those produced in response to a foreign body entering the eye are called reflex tears. Emotional tears produced due to crying or weeping actually have a different chemical composition to the more practical basal and reflex tears - they tend to contain more hormones and even some natural painkiller!