All about glaucoma; symptoms, types and diagnosis of glaucoma

Glaucoma is a condition that leads to slow, but progressive loss of nerve fibres in the optic nerve. Many factors may increase the risk of this condition. If left untreated, this can lead to loss of peripheral vision (i.e. what can be seen at the sides of the visual field, rather than in the centre). In older people, glaucoma is one of the commonest causes of preventable blindness. If glaucoma progresses, it can affect all peripheral vision, then impair central vision, and -- very rarely -- may lead to very significant visual impairment. Treatments for glaucoma are aimed at bringing down the pressure in the eye to a level that is low enough to prevent harm to the optic nerve. Once the optic nerve is affected by glaucoma, lowering the pressure in the eye prevents further damage to the nerve. Damage already done to the optic nerve cannot be reversed. Screening for glaucoma is important from around age 40, every two years at least, unless you are in a higher risk group (eg Afro-caribbean race, or very strong family history of glaucoma).

Signs and symptoms of glaucoma

Symptoms of glaucoma are often absent in the early stages of the disease. Unfortunately, impaired vision is sometimes the first sign of glaucoma. Classically in angle closure glaucoma, symptoms and signs of glaucoma may include eye pain, cloudy vision, red eyes, headaches, and nausea.

How Is Glaucoma Diagnosed?

Frequent eye examinations are the best way to detect glaucoma. Your ophthalmologist will test the eye’s drainage angle, evaluate the optic nerve (ophthalmoscopy), measure eye pressure, and test the visual field of each eye (perimetry). The information from these examinations is compared at regular intervals to determine if glaucoma damage has progressed over time. Regular examinations play a critical role in the early detection of glaucoma.

Glaucoma Progression

Glaucoma typically initially affects side (peripheral) vision first. If left untreated, vision loss will continue, eventually resulting in total blindness. If glaucoma is identified early and treated appropriately, good eyesight can most likely be maintained.

Types of glaucoma.

There are several types of glaucoma, all of which affect the optic nerve. Open-angle glaucoma, the commonest form of the disease, develops when the angle between the cornea and the iris where fluid is supposed to drain from the eye is open, but the fluid drains out too slowly. Closed or narrow angle glaucoma occurs when the drainage angle is blocked by part of the iris and fluid cannot drain from the eye. Normal-tension glaucoma occurs in patients with normal intraocular pressure and is treated in the same way as open-angle glaucoma. Congenital glaucoma occurs when a child is born with a poor drainage outflow facility.

Treatment for glaucoma.

There are two main types of treatment for glaucoma: medication and surgery. Both of these treatments for glaucoma manage the disease by lowering the intraocular pressure. Medications and eye drops are common treatments, but there is the possibility of side effects, and they may eventually become ineffective over time. If the IOP cannot be managed by medications or eye drops alone, surgery or laser may be recommended. Your ophthalmologist will decide on your "target IOP" to help plan your treatment.

Recovery after Glaucoma Treatment

Glaucoma surgery is usually painless, although some patients may experience a slight stinging sensation following the procedure. Local anaesthetics are used to minimise any patient discomfort. After surgical treatments for glaucoma, it is possible to experience blurred vision or irritation. Typically, however, these effects are short-lived and normal activities, such as going to work or running errands, can be resumed after 2-3 days. This time period can be variable, it depends on the exact procedure performed.

Normal pressure glaucoma (or normal tension glaucoma) is an optic neuropathy associated with low intraocular pressure (ie less than 22 mmHg).

The following are known associations of normal pressure glaucoma:
• steroid use (eg nasal sprays, inhaled or oral steroids, or steroid creams) - in this case steroids may infact elevate IOP but this may not be detected and be falsely diagnosed as normal pressure glaucoma
• vasospasm – migraine / Raynauds
• coagulopathies – previous blood loss or shock like epsiode
• systemic nocturnal hypotension
• autoimmune disease
• thyroid disease (increased risk)
• sleep apnoea (especially in overweight men)
• Alzheimer's disease

Other problems to be considered
• intermittent IOP elevation - can be excluded with diurnal IOP measurements
• burnt out glaucoma
• congenital anomaly
• myopia with peri-papillary atrophy
• optic nerve coloboma
• vascular etiology
• carotid occlusion
• previous blood loss
• hereditary optic neuropathy
• Lebers optic neuropathy
• tonometric error (thin cornea)

Investigations
• FBC – rule out anaemia
• CRP / ESR – rule out a condition called "anterior ischaemic optic neuropathy"
• VDRL/FTA – syphilis is a very rare association
• ANA – autoimmune diseases, also Ro, La, Sm
• paraproteinaemia – rule out lymphoproliferative disease
• Lebers – mitochondrial testing where indicated

Imaging
• HRT / OCT / GDx
• MRI if asymmetry, unusual VF, progressive fields, dyschromatopsia, APD with mild cupping
• carotid dopplers
• CXR to rule out sarcoidosis

Other tests
• 24 hour ambulatory blood pressure monitoring

Treatment
• ALT not recommended
• Trabeculectomy with Mitomycin C, if IOP in single digits is required
• In some cases, your physician might recommend Ginkgo Biloba (40mg three times a day). There is some evidence that points to a benefit here, but this medication is not suitable for everyone and it's use is advised on a case-by-case basis, after discussion with your glaucoma specialist.
• Future medication, for selected subgroups of patients with glaucoma, may include memantine, a tablet medication that may have beneficial protective effects on the optic nerve (randomised controlled trials are awaited).

Ginkgo Biloba - not recommended for most patients with glaucoma - little evidence for benefit.