The Symptoms,Risks and Sings of Primary Open Angle Glaucoma

Primary open angle glaucoma

Primary open angle glaucoma is the most common form of glaucoma and is the third most common cause of registration of blindness in the United Kingdom. The resistance to outflow through the trabecular meshwork gradually increases, for reasons not fully understood, and the pressure in the eye slowly increases, causing damage to the nerve. The level of IOP is the major risk factor for visual loss. There may be other damage mechanisms, particularly ischaemia of the optic nerve head.

Symptoms

Because the visual loss is gradual, patients do not usually present until severe damage has occurred. The disease can be detected by screening high risk groups for the signs of glaucoma. At present most patients with primary open angle glaucoma are detected by optometrists at routine examinations.

Groups at risk

The prevalence increases with age from 0.02% in the 40-49 age group to 10% in those aged over 80. Those with an increased risk include first degree relatives of patients (1 in 10), patients with ocular hypertension (particularly those with thin corneas, larger cup to disc ratios and higher IOPs), people with myopia, and people of African-Caribbean origin (X5 risk in Caucasians). Recently, genetic mutations have been identified that account for 3-4% of primary open angle glaucomas.

Signs

The eye is white and on superficial examination looks normal. The best signs for the purpose of detection are the optic disc changes. The cup to disc ratio increases as the nerve fibres atrophy. Asymmetry of disc cupping is also important, as the disease often is more advanced in one eye than the other. Haemorrhages on the optic disc are a poor prognostic sign. Longer term changes in disc cupping are best detected by serial photography, and the more recently introduced scanning laser ophthalmoscope may be able to detect structural changes in the nerve at an early stage of the disease.

Visual field loss is difficult to pick up clinically without specialised equipment until considerable damage (loss of up to 50% of the nerve fibres) has occurred. Computerised field testing equipment may detect nerve fibre damage earlier, particularly if certain types of stimuli such as fine motion or blue on yellow targets are used. Computer assisted field testing is also the best method for detecting long term change and deterioration of visual fields.

The classical signs of glaucoma (field loss and optic disc cupping) often are seen in patients who have pressures lower than the statistical upper limit of normal (21 mm Hg).

However, many clinicians now feel that these two glaucomas are part of the same spectrum of pressure dependent optic neuropathies, although these patients are sometimes referred to as having normal tension glaucoma. For an accurate measurement of IOP, intraocular pressure phasing, taking multiple measurements throughout the day is useful, so that any spikes can be detected.

Some frequently asked questions about glaucoma

• Q: What is childhood glaucoma and how can I prevent the disease from progressing?

A: Childhood glaucoma, also known as infantile or congenital glaucoma, is a disease of infants and is sometimes inherited. It involves a developmental abnormality of the trabecular meshwork, which is the drainage tissue of the eye. Treatment options include medications to lower intraocular pressure and/or anterior chamber angle surgery. Some patients may also need other types of glaucoma surgery. The goal of treatment is to lower the intraocular pressure to prevent permanent visual loss. It is also important to monitor the visual function and to treat any delay in the affected eye’s visual development.

• Q: I have been given a variety of eye drops in a failed attempt to control elevated eye pressure that was apparently caused by retinal vein occlusion in my left eye. I had many problems with the eye drops, including a terribly upset stomach, nausea, indigestion, heartburn and gas. My doctor changed my prescription to Xalatan and Timolol. I have noticed that the pupil in my left eye has become significantly larger than the pupil in my right eye, which is not being treated. Can Timolol cause this symptom and is it safe to continue to use it?

A: Timolol is a topical beta-blocker that acts to reduce intraocular pressure and is very commonly prescribed for the treatment of glaucoma. Timolol has not been shown to cause pupillary dilation. The size of your left pupil may be related to the prior retinal vein occlusion. Other causes of pupillary dilation include topical medications, iris neovascularization, prior intraocular surgery, and others. Your eye doctor should be able to determine the cause of your pupillary asymmetry.

• Q: Is it true that glaucoma patients cannot take medications like Actifed or Sudafed for relief of cold symptoms because they can cause a dangerous increase in eye pressure?

A: Cold medicines such as Actifed and Sudafed can cause mild pupil dilation, which can affect eye pressure. Patients with very narrow angles or untreated angle-closure should not take cold medications. Patients who have been treated for narrow-angle glaucoma or open-angle glaucoma can take cold medicines safely. Your eye care provider should be able to advise you as to the safety of this medication class in your particular case.

• Q: My husband is 36 years old and was just diagnosed with early-stage glaucoma in his left eye. There is no history in his family. Why did he develop this condition and will he be OK? He is now being treated with eye drops. Can you help me?

A: Primary open-angle glaucoma is a multifactorial disease that can affect patients in their 30s. Some patients have no family history of the disease. Glaucoma that affects only one eye may be related to other conditions such as trauma and pseudoexfoliation. Glaucoma that is detected in the early stages carries a better prognosis than glaucoma that is diagnosed at an advanced stage. Treatment involves reduction of the intraocular pressure and monitoring of the optic nerve function. With diligent treatment and follow-up, your husband should maintain vision throughout his lifetime.