Intraocular pressure (eye pressure) is one of the most significant clinical factors in ophthalmology. For the correct function of the eye and its structures and as a matter of fact to preserve sharp and undamaged vision, it is very important to keep intraocular pressure in normal, physiological values.
Intraocular pressure (eye pressure) is a term which probably everyone of us heard before either when visiting a doctor, optometrist, human eye optics or somewhere else. However, many people do not know what this term includes, what its function is and why it is important. The importance of intraocular pressure could be compared to nowadays very much „promoted" blood pressure which people are familiar with and they know that its increase or decrease can have unpleasant consequences. We could talk about intraocular pressure in a very similar way.
Intraocular pressure is one of the most significant clinical factors in ophthalmology. For the correct function of the human eye and its structures and as a matter of fact to preserve sharp and undamaged vision, it is very important to keep eye pressure in normal, physiological values.
Intraocular pressure maintains a permanent shape of the human eye and protects it from deformation which could be caused by the weight of eyelids and the strength of the ocular muscles. It is also essential because it prevents the formation of swellings by releasing a fluid which contains waste metabolites and returns to the blood circulation.
Because the eyeball can expand only marginally, intraocular pressure is a result of the balance between production and drainage of the intraocular fluid. Intraocular pressure decreases when the production of the fluid is lower or the drainage is excessive. On the other hand, high intraocular pressure is caused by excessive production of the intraocular fluid or by insufficient permeability of the drainage ducts which are situated in the ventricular angle.
The range of physiological values of intraocular pressure is relatively wide; for healthy eyes values differ from 10 to 21 mmHg. We need to take into account that values of intraocular pressure are individual and thus we cannot regard boundary values as a higher or lower limit for a normal condition. In other words, values "above" these limits are considered to be suspicious. Even though we know that intraocular pressure is far from being the only symptom in diagnosing glaucoma related disorders, it is still one of the most important ones. Therefore the distinction between physiological, suspicious and pathological values of intraocular pressure is vital.
Diurnal deviation of intraocular pressure is also individual but for healthy normal eyes it should range between 2 to 6 mmHg. The deviations are higher in the cases of ocular hypertension or glaucoma.
The values of eye pressure are the highest in the morning, particularly right after waking up and as the day progresses they tend to decrease. However, this holds true only for 80% of people and others can have maximal values in the evening or reach 2 maximums per day. When trying to find real values of eye pressure for a particular patient, it would be ideal if they were measured at different times during the day. Because substantial majority of patients reaches maximal values in morning hours it is sufficient for clinical practice to measure values just during that time.
Intraocular pressure is an important indicator of the seriousness of the disorder. The examination must be always accompanied by monitoring the visual field and the state of the papilla of the optic nerve. In the case of normotensive glaucoma, the values of intraocular pressure do not have to be pathological, not even in the advanced phase. On the contrary, in the case of ocular hypertension, intraocular pressure is higher but other symptoms of glaucoma are not present. Patients suffering from this disorder have often low blood pressure.
Intraocular pressure significantly increases as a result of mental stress and smoking. Drinking large quantities of liquids in a short period of time can lead to deviations of intraocular pressure. Sport activities, consumption of alcohol in small quantities and smoking marihuana can increase intraocular pressure. The values of intraocular pressure are also influenced by body positioning, use of corticosteroids and state of the eyelids. Body positioning can influence deviations of intraocular pressure. In lying position eye pressure increases approximately by 2mmHg and when a person is standing on his head eye pressure increases extremely. On the contrary, eye pressure decreases during physical activities.