All About Eyes
How we enjoy the miracle of vision and the workings of the eye has fascinated mankind for centuries. It's a field packed with confusing terms and concepts - but below we will unravel and explain some of their mysteries for you. More detailed explanations of many of these conditions and terms below can also be found at the Optometry Australia website. Please note that the information below is of a general nature and is not intended to constitute specific advice for the reader.
Astigmatism is a very common eye focus problem that blurs vision at both close and far distances, and frequently causes eyestrain and headaches when concentrating on visual tasks. It comes about from the eye growing into an imperfect shape, more like an AFL football than a perfectly round soccer ball. Astigmatism often occurs in conjunction with the other two main eye focus conditions, myopia and hyperopia. Optometry Australia's more detailed FAQs about astigmatism appear here.
Because the main cause of cataract is simply ageing, given that we are all living longer lives than our predecessors the incidence of cataract continues to rise. Essentially cataract means that the lens inside the eye is becoming cloudy, anywhere from a little bit cloudy to very cloudy. Cataract is not a film that grows across the front of the eye. Having cataract does not mean you are going blind. Cataract is a very normal change, especially from the 60s and 70s and beyond. The good news is that cataract surgeons have improved their skills and procedures to the point where having cataracts removed is almost a routine operation. Optometry Australia's more detailed FAQs about cataract appear here.
Diabetic Eye Disease
The retina, the light-sensitive film at the back of the eye, is lined and nourished by a network of fine blood vessels. These vessels can be damaged by the high blood sugar levels that occur in diabetes; as a consequence they may leak blood, causing the retina to swell and sometimes for new, even leakier vessels to grow. Left untreated, diabetic eye disease or retinopathy can ultimately cause blindness. If you are diabetic, in many cases your optometrist will recommend that you be examined annually rather than every two years. Control of underlying diabetes is very important in containing diabetic eye disease, although sometimes specialist treatment such as laser surgery to the retina by an ophthalmologist is also required. Optometry Australia's more detailed FAQs about diabetic eye disease appear here.
Glaucoma is a disease that progressively damages the optic nerve at the back of the eye. There are a number of forms of glaucoma, but generally it gradually and painlessly causes loss of parts of the field of vision. Sometimes but not always glaucoma is associated with high pressures inside the eye; other risk factors include a family history (first degree relative) with glaucoma, age, diabetes and high blood pressure. Because it is symptomless until well advanced, glaucoma can be difficult to diagnose, but newer technologies such as optical coherence tomography are making earlier diagnosis possible, along with long-established tests such as measuring the pressure inside the eye and the fields of vision with perimetry. Glaucoma is most usually treated with drops to reduce the pressure inside the eye, but sometimes surgery is required. Optometry Australia's more detailed FAQs about glaucoma appear here.
Hyperopia or long-sightedness ("sight set too far away") makes it more difficult to focus on closer objects. As well as noticing blurred near vision, long-sighted people often suffer from sore, tired eyes and/or headaches when doing close work. Although hyperopia primarily affects near vision, it can also affect distance vision too, and somewhat paradoxically being long-sighted does not necessarily mean that distance vision will be good. Hyperopia is usually well corrected with spectacles or contact lenses; these may not need to be worn all the time and in some circumstances only for close work. Optometry Australia's more detailed FAQs about hyperopia appear here.
Iritis, literally inflammation of the iris, is a relatively unusual but important condition that usually occurs in one eye at a time. It is also known as anterior uveitis, meaning inflammation of the front part of the uvea, which is the pigmented layer that lies in between the retina and the white outer casing of the eye, the sclera. Iritis is often painful and associated with a characteristic set of general body autoimmune diseases such as juvenile rheumatoid arthritis, ankylosing spondylitis, psoriasis, sarcoidosis and inflammatory bowel disease. Iritis typically presents as a painful, red eye, is more frequently seen in males and is often recurrent. Diagnosis and treatment (with drops) of iritis is generally straight-forward, but it is important to rule out involvement of the posterior uvea in each case.
The macula is the small, central part of the retina that provides the most detailed vision. Macular degeneration is an ageing change that disrupts the highly organised way in which the light receptors are positioned and reduces the ability to discern detail, without affecting peripheral vision. Central vision becomes blurred and/or distorted. The biggest risk factor for macular degeneration is age, but smoking is the major controllable risk factor; smokers are two to four times more likely to develop macular degeneration than non-smokers. There are two main forms of macular degeneration, "dry" and "wet". Dry macular degeneration tends to develop slowly but irreversably and currently cannot be treated. Wet macular degeneration causes a relatively rapid drop in vision but if caught early enough can be treated by injections into the eye. Regular eye examinations are extremely important in catching macular degeneration early. Optometry Australia's more detailed FAQs about macular degeneration appear here.
Myopia or short-sightedness ("sight set too short") makes it more difficult to focus on more distant objects. It is a very common condition; typically its onset is either from the mid-teens, but sometimes later in the twenties. There is considerable debate about whether myopia is inherited or whether it is exacerbated by doing excessive close work. There are a number of treatment options for myopia, including spectacles, soft or hard contact lenses, orthokeratology and laser refractive eye surgery; some or all of these may be suitable for you. Optometry Australia's more detailed FAQs about myopia appear here.
Presbyopia is a normal ageing change that makes reading more difficult and affects virtually everyone, typically from their mid-forties although it develops from childhood. Presbyopia can not be prevented and occurs whether you are short-sighted, long-sighted, or neither. It occurs because the lens inside the eye that normally changes shape to provide a change in focus has lost its elasticity and flexibility and is less able to change shape. Presbyopia resembles hyperopia in making close work more difficult, but is not the same. A common clue to presbyopia becoming evident is having to hold objects out at arms length to see them, and complaining that your arms are not long enough. Spectacles and sometimes contact lenses are used to correct presbyopia; multifocals are a popular spectacle lens option for this. Optometry Australia's more detailed FAQs about presbyopia appear here.
The sclera, or white part of the eye, is covered by a clear membrane called the conjunctiva. Sometimes the conjunctiva thickens, grows and encroaches onto the cornea, or clear tissue at the front of the eye - this is called a pterygium. Pterygia most commonly appear on the nasal (inner) sclera but can also appear on the outside. They are sometimes confused with cataracts, but cataracts are a clouding of the lens inside the eye whereas pterygia are on the outside of the eye. Pterygia are not a cancer or tumour, but are mainly caused by exposure to UV radiation so are more commonly seen in people who spend long hours outdoors and/or live in hot, sunny environments. They tend to exacerbate symptoms of dry eye. Wearing sunglasses when outdoors is perhaps the best way of avoiding pterygia; if they threaten to extend too far onto the cornea they are usually removed surgically under local anaesthetic.
Retinal Tears and Detachments
The retina is the film made up of light-sensitive nerve fibres at the back of the eye. This film is attached to the sclera, the outer casing of the eyeball. There are a number of circumstances where the retina tears and/or becomes detached from this casing, such as due to trauma; or when the vitreous liquifies, contracts and moves forward, and pulls the retina with it. Tears and detachments are painless; typically but not always they start in the peripheral retina, but left untreated spread to involve more central areas. People who are more highly short-sighted are at greater risk of developing retinal tears and detachments. Classical symptoms of a tear or detachment include photopsia (flashing lights), a sudden and dramatic increase in the number of floaters and the appearance of a veil or curtain across vision. Retinal tears and detachments need to be treated urgently, within a day or so, in order to preserve central vision in particular.
Smoking and Vision
Smoking is strongly related to poor health generally and the eyes are no exception. Smoking reduces the critical blood supply to the eyes because it narrows the blood vessels and thickens the blood. It directly accelerates the development of cataract and of particular importance significantly increases (by two to four times) the probability of macular degeneration. Smokers are over 80 per cent more likely to suffer dry eye disease than non-smokers, and contact lens wearers who smoke also encounter more difficulties with their wear than those who don't.
Vitreous floaters, usually just referred to as "floaters", are generally harmless but sometimes disturbing small, shadowy shapes that can appear in our vision at any stage of life but tend to become more common with age. They may be round or linear, and are often described as anything from spots, specks, clear bubbles, threads or even spider webs. Floaters occur as a result of changes to the vitreous, the clear gel inside the eye, as it breaks down and becomes more liquid over life. Sometimes they occur if the vitreous more quickly detaches or pulls away from the retina. If floaters are numerous, change suddenly, or are accompanied by flashing lights, this may be a sign of a retinal tear or detachment, and in these circumstances it is important to see an optometrist urgently, preferably that day.