Closed angle glaucoma
El glaucoma is a serious eye disorder that can lead to blindness and usually has no symptoms. The angle-closure glaucoma o narrow is a type of glaucoma consisting of a sudden increase in intraocular pressure that in a matter of some hours can go from one normal eye pressure (up to 21 mm Hg) at a pressure of up to 80 mm Hg.
One of the most serious emergencies in ophthalmology is angle-closure glaucoma, a process that comes on suddenly, having a elevation of eye pressure so strong that it can cause irreversible vision loss.
Closed angle glaucoma
El glaucoma is a serious eye disorder that can lead to blindness and usually has no symptoms. The angle-closure glaucoma o narrow is a type of glaucoma consisting of a sudden increase in intraocular pressure that in a matter of some hours can go from one normal eye pressure (up to 21 mm Hg) at a pressure of up to 80 mm Hg.
One of the most serious emergencies in ophthalmology is angle-closure glaucoma, a process that comes on suddenly, having a elevation of eye pressure so strong that it can cause irreversible vision loss.
What is angle-closure glaucoma?
We know that Glaucoma is the second leading cause of blindness in the Western world and that Closed angle glaucoma (GAC) represents almost 30% of glaucomas although if we look at the incidence of acute crises, narrow angle glaucoma represents almost 90% of cases. Angle-closure glaucoma is more frequent in women and in ages over 60. There is no clear relationship with genetic factors but frequently associated with small eyes, as it happens in many people with farsightedness, a situation that does have a genetic componentTherefore, in these cases it is necessary to take it into account.
Angle-closure glaucoma courses with strong ocular pain, Red eye, halos perception around the lights, pupil dilation, nausea y vomiting. It is due to a strong increase in intraocular pressure (CHEEP).
Diagram where the position of the iris with respect to the cornea is simultaneously shown, forming angles of 45º and closed angle of 20º.
When we talk about angle in the context of glaucoma, we are doing reference to the degree of separation between the iris root and the cornea (the trabecular meshwork), that if we represented in an idealized way by two lines, we could describe them as if it were an angle.
How to identify angle-closure glaucoma
Under normal conditions we consider the angle with value of 20º as normality limit. Values above 20º are considered normal and below 20º they are pathological, it is what we know as angle-closure glaucoma.
A narrow angle, by itself, is a risky situation for an increase in IOP to occur, the real problem is when the angle is so closed that it may hinder the normal evacuation of the aqueous humor (liquid that is inside the eye), or when the angle is closed completely, blocking the outflow of aqueous humor and causing its accumulation inside the eye with the consequent increased intraocular pressure, as if we inflated a ball, is what is known as "acute glaucoma by angle closure".
Anatomic image of the anterior segment (left) and schematic of the aqueous humor flow (blue) from the posterior chamber to the anterior chamber, through the pupil, reaching the trabecular meshwork at the camerular angle (right).
Causes of angle-closure glaucoma
There is usually a prior predisposition. Usually usually occurs in hyperopic eyes, which in themselves are smaller, where the angle between the cornea and the iris is less than normal.
In this situation, a pupil dilation (dark environment, fear or stress situation, certain use of drugs) produces a sudden blockage of the aqueous humor outflow towards the anterior chamber.
Symptom
Main symptoms to identify glaucoma closed angle are:
- Appearance a Intense pain acutely, which can radiate to the nape, forehead and jaw.
- They often suffer frequently vomiting and nausea.
- People with acute glaucoma notice colored halos around the lights in the affected eye and blurred vision.
- May appear Red eye y dilated pupil.
Diagnosis
The symptoms that the patient presents is the first thing that makes the diagnosis suspect.
- In the exploration we will find very high intraocular pressure.
- Cloudy cornea, edematous y narrow anterior chamber or collapsed.
The pupil
El classic trigger factor is mydriasis media, both physiological, caused by dimly lit environments, like cinemas, etc., like the pharmacological, the most common is that produced by the instillation of eye drops with mydriatic action, like parasympatholytics or alpha sympathomimetics, commonly used in fundus examinations, to dilate the pupil and see the inside of the eye.
Likewise, the administration of any systemic medication with a parasympatholytic effect, such as atropine, antidepressant drugs, against dizziness, etc., can have the same effect, dilate the pupil causing the iris to retract at the periphery by closing the chamber angle.
Due to this effect, people who must take drugs of the type: muscle relaxants, antidepressants, tranquilizers, etc., should previously perform an ophthalmological review to value the ampcamerular angle and prevent possible angle-closure glaucoma.
Measure angle
Until now, the assessment of the chamber angle was very subjective, depended on the ophthalmologist, on how he visualized this anatomical structure with a special lens (gonioscopy), with the intersubjective variations that this implies. Nowadays We have new analysis systems of images that allow to objectify in a very precise way the anatomical structures, where the root of the iris and the trabecular meshwork are identified, incorporating markers that calculate the angle that they delimit.
With the OCT we can analyze the situation of each patient and to monitor how the angle varies with age (with the years it tends to decrease) or, with the prescription of drugs that can alter it, as we have previously indicated, we can also see the effect of the treatment applied to open the chamber angle, such as YAG laser iridotomy, to prevent pressure increases or acute crisis.
Image of the camerular angle taken with OCT where the anatomical structures can be identified and the angle measured, as in this case, 19º in the upper image and 43º after opening the iris with a YAG laser (asterisk).
Angle-closure glaucoma: pathophysiology
The pathogenic mechanisms of primary angle closure glaucoma are multiple but, in most cases starts with a pupil block, especially in the white population. It happens that the aqueous humor that occurs in the posterior chamber it has to go to the previous chamber to leave the eye. On this path you must pierce the pupil, for which you must "lift upDiscreetly The iris on the anterior face of the lens, on which it rests to a greater or lesser degree. This makes the iris, subjected to this difference in pressure between its posterior face and its anterior face, presents a bulged aspect forward, which brings its most peripheral part closer to the trabecular meshwork, reducing the chamber angle.
If the pupil is semi-dilated, iris peripheral is relaxed and flabbyTherefore hardly resists being pushed forward by the pressure exerted by the aqueous humor from the posterior chamber, bulging forward and getting closer and closer to the trabecular meshwork, until at some point completely contacting and closing the chamber angle, as we see in Figure 3.
We know that there are a series of triggers that, together with the anatomical predisposition of the small anterior chamber or a flaccid iris, will be responsible for closing the chamber angle and initiating acute glaucoma by angle closure.
Pathogenetic mechanism of the angular closure by pressure of the aqueous humor from the posterior chamber, lifting the iris and bringing it closer to the cornea.
Treatment of angle-closure glaucoma
An attack by angle-closure glaucoma is a very serious ophthalmological emergency and requires immediate attention. The objective of treatment is to decrease intraocular pressure, allowing the cornea to regain its transparency and relieve pain. We will reduce the intraocular pressure using osmotic diuretics, like mannitol and carbonic anhydrase inhibitors, to reduce the production of aqueous humor.
Later are administered topical corticosteroids to reduce inflammation and miotics like pilocarpine to break the pupil block. Topical hypotensive drugs such as beta-blockers can also be used.
Once the hypertensive condition is resolved, as the risk factors persist, a communication between the anterior and posterior chamber of the eye so that the frame does not replay. This communication normally it is done by YAG laser, is known as iridotomy, which will also be done prophylactically in the other eye.
Prevention
Since this condition is very severe, it is important to carry out the prevention through eye exams.
Narrow angle or predisposition to acute glaucoma could be detected by routine eye examination. Also, today we have the OCT that can make measurements and angle visualization to have more accurate diagnoses.
If a risk angle is detected in a review prophylactic iridotomy is advised in both eyes.
When there is history of angle-closure glaucoma or hyperopic in the family, it is necessary to carry out a detailed study full anatomical structure of the eyeDe of anterior chamber and iris arrangement, and follow-up visits to take intraocular pressure and monitor that the chamber angle is not reduced with the passage of time or for other circumstances, in these cases the indication of a YAG iridotomy It can save us from acute crisis and possible loss of vision.
