Good Hope Eye Clinic

Intraocular hypertension

David Kinshuck

What is 'intraocular hypertension'? 

'Intraocular hypertension' is the medical way of saying 'too much pressure' in the eye. The eye contains fluid. The fluid is made in the middle chamber of the eye. From this middle chamber, it then flows into the front chamber, and from there it drains out of the eye itself.

If the 'drain' blocks a little, the fluid will become trapped in the eye, and the pressure will go up. This is just like pumping a tyre up a little too much.(The fluid is nothing to do with tears, which are on the outside of the eye.)

aqueous fluid is made in the middle chamber of the eye (in the ciliary body) and flows into the front chamber, and then out of the eye, through a drainage system

The eye is like a small ball, the size of a table-tennis ball. Fluid, a type of salt solution, is made in the eye (the 'tap'). The fluid circulates to the front of the eye (the arrow), and then drains out of the eye (shown in green), into the blood stream. enlarge

a blocked drain causes the eye pressure to rise and damage the optic nerveIf the drain blocks, the pressure in the eye builds up and may press on the nerve at the back of the eye, damaging the nerve and the sight.   enlarge

How does this affect the sight?

Generally the sight will be normal in this condition. But the condition is important, as sometimes 'glaucoma'  may develop. A few people with intraocular hypertension develop glaucoma each year; this occurs when the pressure on the nerve at the back of the eye actually damages the nerve.

In 'intraocular hypertension' the nerve at the back of the eye remains healthy. But in glaucoma the fluid pressure in the eye starts to press to hard on the nerve and damages it: this damages the sight.

The nerve is the 'electric wire' of the eye. It takes the messages from the eye about what you see, and sends them on to the brain.

If the drain blocks, the pressure in the eye builds up and may press on the nerve at the back of the eye, damaging the nerve and the sight.   enlarge

 

 

 

 

 

 

What do you need to do?

The ophthalmologist or optometrist needs to check the eyes regularly, in order to check that glaucoma has not developed. Generally yearly checks are needed. Three tests are needed:

  • eye pressure
  • an examination of the nerve (by the ophthalmologist or optometrist looking in)
  • a visual field test

goldmann tonometer

measuring eye pressure is painless. After some anaesthetic drops, the 'tonometer' touches the surface of the eye.

Eye Pressure

As opposite, the tonometer probe touches the surfcae of the eye to measure the pressure. This takes a few seconds.

 

 

 

 

 

Ophthalmoscopy of the optic nerve

The doctor looks at the optic nerve with an ophthalmoscope, a type of torch. This takes a few seconds. Often this test is carrried out whilst you are sitting at a slit lamp'. The slip lamp is simply a pair of binoculars with a light that shines in from the side.

 

Visual field test

A visual field test takes a little longer. It is a test to see that the nerve at the back of the eye is working properly. You have to sit with the head still looking straight ahead, and a light flashes from the side. If you see all the lights of a certain brightness, you press a button, and the computer keeps a record. it then prints out a 'map' of all the lights you can and cannot see, This test identifies whether or not the nerve is damaged. See

 

Who needs treatment

Risk of glaucoma
  • pressure > 25mmHg
  • glaucoma in the family
  • optic nerve slightly damaged from pressure
  • Afrocarribean
  • thinner corneas
  • young age
  • visual field changes
  • retinal vein occlusion

another study

  • older age
  • more cupping
  • field loss
  • not thinner corneas
  • notched disc
  • Eye 16

 

You will not know whether you have glaucoma in its early stages: this can only be detected by this examination. Glaucoma does not cause pain. Treatment is sometimes necessary to lower the eye pressure (as with Glaucoma) delaying glaucoma.

In practice many patients are recommended treatment. Those with the lowest pressure (eg 22mmHg, and none of these risk factors), may not need treatment. Many patients are 'in between' and a personal discussion may be helpful.

See more evidence and a search.

The increased risk for Afrocarribean's is more related to the increase risk factors, rather than 'race' itself (Delaying...2010).

Older patients with slightly high pressures (<24) without risk factors do not need treatment (Delaying...2010). There are of course many patients in between.

Patients with intraocular hypertension who develop a retinal vein occlusion need to be treated as though they have early glaucoma, and need a low pressure.

 

 

What is the cause of intraocular hypertension?

No one knows exactly why the drain of the eye blocks. (It is the blocked drain keeping the fluid inside the eye that causes the pressure in the eye to go up.) See animation. The blockage is not caused by smoking or anything you have done. However, the condition can run in the family. Scientists have found genes that can cause the condition. The genes, which you inherit from the parents, control the chemistry of the tiny cells in the 'drain'. The cells may work normally for 50 years, letting the fluid out of the eye, but then begin to stop working. The fluid then gets trapped in the eye.

 

Summary

Intraocular hypertension is a condition when the eye has a little too much fluid inside it, like a tyre being pumped up too hard. It is not harmful itself, but a few patients later develop glaucoma. Glaucoma is more serious, as the fluid pressure in the eye presses on the nerve at the back. This can damage the sight.To detect glaucoma in the very early stages, you need three tests at the optometrists each year:

  • eye pressure measurement
  • examination of the nerve at the back
  • visual field test (a test of the side vision)

You should look after the general health, and the brothers and sisters should be also be tested by their optometrist.

In addition to having the three tests above, a healthy lifestyle helps, as recommended by the Department of Health below.

Your general health in glaucoma/intraocular hypertension

Remember that your general health and lifestyle have a major impact on glaucoma and your sight. BJO 12

  • Smoking does increase the eye pressure, and will make your glaucoma worse BJO 16. It also increases the risk of retinal vein occlusion (which occur in glaucoma), macular degeneration, cataracts, stroke, and heart attacks. The exact risk is not known, but in some patients 20 cigarettes / day will increase loss of vision by 400%. Passive smoking 20 a day is equivalent to smoking 5 cigarettes a  day, and increase visual loss 100%.
  • Metabolic syndrome is strongly related intraocular pressure (Nature 2010   OO15). This is related to (as below) lack of exercise, high blood pressure, obesity and liver and kidney problems. Treatment of the metabolic syndrome will help lower eye pressure 0.8mmHg..
  • Exercise lowers the eye pressure, 'an hour a day (walking) will keep the doctor away', and half an hour will help a lot. See. Any exercise will do... eg walking, swimming, gardening.
  • High blood pressure will be harmful as this may, together with the glaucoma, cause a retinal vein occlusion. A blood pressure of 140 systolic or less, may be best, and may be lower the better as long as you feel well. See   But there are other views. We now know that eye pressure and blood pressure are related; the implication of this is that lowering blood pressure will help in the treatment of glaucoma. So keeping your blood pressure reasonably low is an important part of the treatment, although too much medication may cause problems.
  • Oily fish will help the circulation and probably help prevent retinal vein occlusions. Red meat  (including pork/ham) increase blood pressure; they are best replaced, at least in part, by fish, and pulses such as lentils and beans. Nuts have some healthy fats, and may be helpful in small amounts...but they are 'fattening' and help to put weight on.  A Mediterranean diet helps.
  • 9 portions of vegetables or fruit a day will also help to keep your retinal veins and macula healthy, and prevent cataract formation...9 a day (men) 7 (women) keeps the doctor away. BJO 16.
  • A high saturated fat diet is very harmful as it will contribute to many conditions. A balanced diet is recommended. Saturated fat comes from full-fat diary products such as milk, cheese, many cakes and biscuits, and red meat. Statins help (surely a benefit of a low cholesterol).
  • Salt will increase blood pressure.
  • binge drinking, eg 4 pints of beer in one day, or more that 3 glasses of wine/day, will cause a rise in blood pressure, again contributing to all these conditions. Coffee increases PXF glaucoma.
  • Obesity results in high blood pressure, lack of exercise, and indirectly will cause problems. Many obese patients suffer from sleep apnoea....
  • Sleep problems. New research links sleep apnoea with glaucoma. Sleep problems are very common in obesity...these are likely if you snore a lot. Logically if you are overweight, it is important to lose weight to help your glaucoma. So if you do snore a lot, do lose weight, and ask your doctor if you need to be tested for sleep apnoea. 2012 2014  Eye14
  • Steroid medication puts eye pressure up. Even inhaled nasal steroids can increase the pressure 2.5mmHg. If you use nasal steroids (eg for allergic rhinitis), ask your doctor if you can reduce or stop them. Steroid tablets certainly may put eye pressure up; ask your doctor if you can reduce the dose (Do not reduce steroid tablets without seeking advice.).
  • Retinal vein occlusions: patients with glaucoma are much more prone to retinal vein occlusion. The risk of a vein occlusion is reduced by control of the glaucoma, blood pressure, and all the other general health risk factors immediately above.

 

Small print for professionals

See the evidence: eyes with a central corneal thickness of 555µ or less have a 3 times increase in risk of progressing compared to eye with a thickness of 588µ or more.  TTreatment in low risk cases can be safely delayed (Arch 2010). POAG can be predicted.

 

leaflet...low tension glaucoma

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Microsoft Publisher document