Glaucoma
Glaucoma is a term used to describe a group of ocular disorders with multi-factorial etiology united by a clinically characterized by intraocular pressure-associated optic neuropath. It is normally associated with increased fluid pressure in the eye (aqueous humour). High intraocular pressure (above 21 mmHg or 2.8 kPa) is the most important and only variable risk factor for glaucoma. However, some may have high eye pressure for years and never develop damage, while others can develop nerve damage at a relatively low pressure. Glaucoma if left untreated can lead to permanent damage of the optic nerve and resultant visual field loss, which over time can progress to blindness.
Types of glaucoma:
There are four main types of glaucoma:
Chronic open-angle glaucoma – This is the most common type of glaucoma and develops very slowly
Primary angle-closure glaucoma – This is rare and can occur slowly (chronic) or may develop rapidly (acute) with a sudden, painful build-up of pressure in the eye.
Secondary glaucoma – This occurs as a result of an eye injury or another eye condition, such as uveitis (inflammation of the middle layer of the eye).
Developmental glaucoma (congenital glaucoma) – This is rare but can be serious. It is usually present at birth or develops shortly after birth. It is caused by an abnormality of the eye.
Symptoms
Chronic glaucoma: In chronic glaucoma, generally no noticeable symptoms are seen as the condition develops very slowly. People often do not realize that their sight is being damaged because the first part of the eye to be affected is the outer field of vision (peripheral vision). Vision is lost from the outer rim of the eye, slowly working inwards towards the centre. Changes in vision are often linked with age. That is why it is advised to get your eyes checked regularly.
Angle closure glaucoma: Symptoms develops rapidly. They include:
Acute pain
Redness of the eye
Headache
Tenderness near the eye area
Seeing halos or 'rainbow-like' rings around lights
Blurred vision
Loss of vision in one or both eyes that progresses very quickly.
Secondary glaucoma: Secondary glaucoma is generally caused by other conditions or other eye injuries like uveitis (inflammation of the middle layer of the eye). Generally symptoms of glaucoma are confused with the symptoms of the other conditions. For example, uveitis often causes painful eyes and headaches.
Developmental glaucoma: Symptoms of developmental glaucoma (also known as congenital glaucoma) can be difficult due to the young age: However, symptoms include:
large eyes due to the pressure in the eyes causing them to expand
Being sensitive to light (photophobia)
Watery eyes
Jerky movements of the eyes
Squint, which is an eye condition that causes one of the eyes to turn inwards, outwards or upwards while the other eye looks forward
Causes
The cause of glaucoma is the blockage in part of the eye. Blockage prevents the fluid to drain out of the eye and therefore increases pressure in the eye, called intraocular pressure.
Risk factors associated with the condtions are:
Age: Older people are at high risk of developing glaucoma.
Ethnic race: People of African or Afro-Caribbean origin are at increased risk of developing chronic open-angle glaucoma. People of Asian origin are at high risk of developing acute angle-closure glaucoma Medical history – people with conditions like diabetics caused by too much glucose in the blood, may be at increased risk of developing glaucoma ocular hypertension (OHT – raised pressure in the eye). People with OHT are at increased risk of developing chronic open-angle glaucoma.
Family history: If a close relative, such as a parent, brother or sister who has glaucoma, risk of developing the condition also increases.
Diagnosis
Glaucoma can be screened by performing standard eye examination.
Tests for glaucoma include:
Measuring intraocular pressure via tonometry
To see the changes in size or shape of the eye
Anterior chamber angle examination and examination of the optic nerve to look for any visible damage
For further diagnosis please consult your GP.
Treatments
Intraocular pressure can be lowered with eye drops.
Prostaglandin analogs: Such as latanoprost (Xalatan), bimatoprost (Lumigan). These medications usually increase uveoscleral outflow of aqueous humor. Bimatoprost also increases trabecular outflow.
Topical beta-adrenergic receptor antagonists: Such as timolol, levobunolol (Betagan), and betaxolol, helps in decreasing aqueous humor production by the ciliary body.
Alpha2-adrenergic agonists: Drugs like brimonidine (Alphagan) and apraclonidine, work by a dual mechanism, as they decrease the aqueous humor production and increases the uveoscleral outflow.
Less-selective alpha agonists: Medications like epinephrine, also decrease aqueous humor production through vasoconstriction of ciliary body blood vessels, useful only in open-angle glaucoma. Epinephrine's mydriatic effect, however, renders it unsuitable for closed-angle glaucoma due to further narrowing of the uveoscleral outflow (i.e. further closure of trabecular meshwork, which is responsible for absorption of aqueous humor).
Miotic agents (parasympathomimetics): Drugs like pilocarpine, work by contracting the ciliary muscle, opening the trabecular meshwork and thus allowing increased outflow of the aqueous humour.
This is only an indicative information, for treatment purpose you should consult your physician.
Complications
Loss of vision is the main complication of glaucoma due to this reason early diagnosis and treatment is so important.
References:
CDC
NHS
U S National Library of Science
WHO
