Glaucoma is a disease caused by increased pressure from a malformation or malfunction of the eye's drainage systems. Left untreated, such elevated pressure causes irreversible damage to the optic nerve and retinal fibres resulting in progressive, permanent vision loss mostly experienced as "tunnel vision". Fortunately, early detection and treatment can slow, or even halt the disease’s progression.
The eye constantly produces aqueous clear fluid which fills the anterior chamber (the space between the cornea and iris). The aqueous fluid filters out of the anterior chamber through a complex drainage system and the delicate balance between production and drainage of aqueous determines the eye’s intraocular pressure (IOP). Most people’s IOPs fall between 8 and 21. Pressures which are too high indicate glaucoma.
Open angle (also chronic open angle or primary open angle) is the most common type of glaucoma and with this, even though the eye’s anterior structures appear normal, aqueous fluid builds within the anterior chamber, causing elevated IOP. Left untreated, this may result in permanent damage of the optic nerve and retina.
Because glaucoma mostly does not cause symptoms, those who are aged 40 years or older should have an examination every two years including a measurement of the intraocular pressure. Those who are more likely to develop glaucoma (such as a family history of it) require more frequent testing. Glaucoma evaluation has several components. Besides measuring intraocular pressure, the optometrist will also evaluate the health of the optic nerve (ophthalmoscopy) and test peripheral vision (visual field test), before making a diagnosis.
The above photos show progressive optic nerve caused by glaucoma. Notice the pale appearance of the nerve on the right as compared to the nerve on the left.
Glaucoma’s progression is monitored with a visual field test which maps peripheral vision to determine vision loss and effectiveness of treatment. This is repeated periodically to verify that intraocular pressure is being adequately controlled.
Most glaucoma patients require only medication to control intraocular pressure although sometimes several complementary medications are necessary. When medication fails to lower the pressure, surgery - some involving laser - is used. The objective of any glaucoma operation is to allow fluid to drain from the eye more efficiently.
Diabetes occurs when the pancreas does not secrete enough insulin or the body is unable to process it properly. The disease can affect children and adults, and most importantly, it can impact on your eye health.
Research has shown that diabetic patients who maintain appropriate blood sugar levels have fewer eye problems than those who do not. Diabetics can also greatly reduce the possibilities of eye complications by routine eye examinations. Many problems can be treated much more successfully when caught early.
Patients with diabetes are more likely to develop eye problems such as cataracts and glaucoma, but the disease’s effect on the retina - diabetic retinopathy - is the main threat to vision.
Over time, diabetes affects the retina’s circulatory system. In the disease’s earliest phase, the retina’s arteries become weakened and leak, forming small, dot-like hemorrhages. These leaking vessels often lead to swelling or edema in the retina and decreased vision. With further circulation deterioriation, areas of the retina become oxygen-deprived or ischemic. While new, fragile, vessels develop as the circulatory system attempts to maintain adequate oxygen levels within the retina, these delicate vessels hemorrhage easily and may leak into the retina and vitreous, causing spots or floaters, along with decreased vision.
In diabetes’ later phases, continued abnormal vessel growth and scar tissue may cause serious problems such as retinal detachment and glaucoma.
Diabetic patients should have routine eye examinations so problems can be detected and treated as early as possible. Diabetic retinopathy is diagnosed from a detailed examination of the retina with an ophthalmoscope and most patients with it are referred to ophthalmologists who specialise in treating this disease.
Diabetic retinopathy can be treated in many ways depending on the disease's progression and the specific eye problem. The abnormal growth of tiny blood vessels and associated bleeding is one of the most common problems and laser surgery called pan retinal photocoagulation (PRP) is usually the treatment of choice.
A cataract is a clouding of the natural lens, the part of the eye which focuses light and produces clear, sharp images. It does not form as a film on the eye, as many think, but actually forms within the eye.
Eye without a cataractEye with a cataract
For most people, cataracts result from ageing and they are the leading cause of vision loss among people aged 55 and older. Eye injuries, certain medications, excessive UV exposure and diseases such as diabetes and alcoholism have also been known to cause cataracts.
The natural lens is contained in a sealed bag or capsule and as old cells die they become trapped within this capsule. Over time, the cells accumulate causing the lens to cloud and images appear blurred or fuzzy.
The main symptoms of cataracts are blurred vision reducing the capacity to read or see clearly in the distance, and glare which may be a problem with bright sunlight or headlights at night.
Sunglasses may help prevent the progression of cataracts and can also help reduce symptoms of glare which can occur with cataracts. Regular eye examinations by an optometrist are important to check for cataracts and any changes in them so you can get the best advice on treatment options.
Through recent medical and surgical advances, cataract surgery has become a very gentle procedure performed through tiny incisions in the cornea (the transparent covering of the front of the eye) which do not even require stitches resulting in minimal recovery time and best possible vision.
To remove the cataract - situated inside the lens capsule which is like an elastic bag - the front portion of the capsule is carefully opened and the cataract is gently broken up using ultrasonic vibrations before being vacuumed out of the lens capsule. This technique is called phacoemulsification. The capsule is left undisturbed so a tiny lens implant can be inserted in place of the original lens. Most implants are made of either hard plastic or soft, foldable silicone to best suit the patient.
The macula is the central retina of the eye and it degenerates with age, a condition called age-related macular degeneration (AMD). For people over 50, this is a very common cause of vision loss and its prevalence increases with age. Arteries nourishing the retina harden with age and this deprives the sensitive retinal tissue of essential oxygen and nutrients resulting in deteriorating central vision.
The severity of macular degeneration varies greatly from slight distortion to complete loss of central vision, making reading or driving impossible. Fortunately, it does not cause total blindness since it does not affect the peripheral vision.
There are two main types of AMD - wet (neovascular) or dry (non-neovascular). About 10 per cent of patients who suffer from macular degeneration have wet AMD which occurs when new vessels form to improve the blood supply to oxygen-deprived retinal tissue. However, these new vessels are very delicate and break easily, causing bleeding and damage to surrounding tissue. Dry macular degeneration is more common and typically results in a less severe, more gradual loss of vision. The retina of an eye with dry ARMD
Regular visits to your optometrist are essential to diagnose and monitor AMD. Your optometrist will examine your eyes, particularly the central retina, and refer you for specialist treatment of necessary.
Genetics, age, nutrition, and smoking can cause macular degeneration and even UV exposure may play a role so wear sunglasses.
There is no proven medical therapy for dry macular degeneration. However, in some wet macular degeneration cases, some treatments can seal leaking or bleeding vessels. Unfortunately, this usually does not restore lost vision, but it may prevent further loss.
Early diagnosis is critical for successful treatment of wet macular degeneration and therefore regular eye examinations are important.
Several recent studies suggest a strong link between poor nutrition and the development of macular degeneration. It has been scientifically demonstrated that people with diets high in fruits and vegetables (especially leafy green) have a lower incidence of the condition. The types of fats in a diet are also important; transfatty acids derived from the processing of vegetable oils should be avoided.
Studies have indicated that antioxidants may help reduce the degree of vision lost in those with AMD. Supplements such as Macu-vision from Blackmores with its combination of antioxidants and zinc can help and is available at pharmacies and health food stores. Remember, supplements are not a cure for AMD and you should discuss their use with your GP.