Laser eye surgery is used to permanently correct eye disorders such as astigmatism

Glasses or contact lenses are the most common treatment for astigmatism

A stigmatism is perhaps one of the most common eye conditions people experience. Around one in three people have been told that they have some sort of astigmatism. The condition comes from an irregularity in the shape of the eye’s cornea. The cornea is normally a circular lens that works like a window, allowing light to pass through other parts of the eye, such as the lens and the retina. Among those with astigmatism, the shape of the cornea is slightly altered and is more oval, similar to the shape of an egg. The egg-like shape can either occur horizontally, when the cornea is wider than tall, or vertically, when it is taller than wide. Any alteration in the shape of the cornea affects the way light is projected into the eye, detected by optical sensory cells and interpreted by the brain. The result of such corneal alteration is blurred vision, headaches and eye strain.

Astigmatism is one of several eyesight disorders, the two most common being myopia (nearsightedness) and hyperopia (farsightedness). Similar to astigmatism, being either near or farsighted is related to the focal point that light reaches inside the eye. For farsighted individuals this point is behind the retina, and for nearsighted people is before. Astigmatism doesn’t have a single focal point, which leaves objects both in the foreground and at a distance blurry.

There are several causes of astigmatism, including a genetic disposition for the condition, physical trauma or surgery. It can also be made worse by rubbing the eye. Rubbing the eye too much can stretch the cells that make up the cornea, leading to a change in its shape. Treating astigmatism is relatively simple. A good pair of corrective lenses can refocus light that enters the eye and point it in the right direction to offset the shape of the cornea. For more severe cases, laser-assisted in situ keratomileusis (LASIK) surgery uses a high-powered laser to precisely cut and reshape the cornea.

Two bonobos engaging in daily grooming

BONOBO BIFOCALS

As we age, our eyesight naturally deteriorates and corneal astigmatism worsens, typically after the age of 50, and that applies to other primates, too. The eyesight of humankind’s closest relative, the bonobo (Pan paniscus), becomes increasingly farsighted as they age. In 2016, researchers studied bonobos grooming members of their troop. What they discovered is that bonobos under the age of 30 looked into their grooming partners’ fur from around ten centimetres. However, by the age of 45 that eyesight distance had gradually increased to around 40 centimetres, suggesting the older apes were farsighted.

CONE CORNEA

Keratoconus caused the eye’s cornea to bulge into a cone shape

© Getty

Astigmatism is one of the three most common eye disorders. However, when the eye’s cornea becomes too thin and its shape bulges into a cone, the result is a condition called keratoconus. Affecting around one in 2,000 people, keratoconus is a severe disease where the collagen within the cornea decreases. Sufferers of keratoconus experience blurred vision, sensitivity to light and a sudden worsening or clouding of vision. The disease typically starts during puberty and progresses into a person’s mid-30s, but the exact causes of keratoconus remain unclear to scientists. Research has shown that one in ten people with keratoconus share the condition with one of their parents. One of the most effective methods to treat keratoconus is a corneal transplant, whereby a donor cornea is inserted as a replacement.