If the peripheral iris and the cornea come into contact, the Aqueous fluid is unable to reach Schlemm’s drainage canal, causing the IOP to rise rapidly and painfully. The eye will usually look red, and the cornea can become hazy. The pupil is often oval, mid-dilated and unreactive to light. The pain may be felt in the abdomen instead of the eye, and along with the common symptom of nausea or even vomiting, can make the sufferer suspect food poisoning or something similar.
This type of Glaucoma is classically said to be more likely in middle aged or elderly ladies, who are significantly hyperopic (longsighted). The text books also mention that they are generally “highly strung”, but then who wouldn’t come across like this when consulting an eye specialist in an emergency situation!
Urgent medical treatment is required as an eye could be blinded within 24 hours. Once the pressure has been normalised with medicine, a surgical procedure usually an iridectomy is performed to ensure it doesn’t recur. This ensures aqueous will always be able to reach Schlemm’s canal to drain. A similar, but usually simpler procedure, often performed by laser is recommended to prevent an attack in the other eye.
Angle closure is often preceded by less severe sub-acute attacks where access to the drainage becomes only partially blocked. Symptoms may include frontal headache, a feeling of pressure in the eye, and hazy rainbows seen around lights. These symptoms are most likely to occur when the pupil is mid-dilated (the iris is thicker) perhaps when watching TV in the evening in a dimly lit room. The sub-acute attack may be halted by deciding to go to another room, which could be brighter, or deciding to sleep off the headache, both of which tend to cause the pupil to constrict, pulling the iris out of the angle it is blocking.
It is possible to pick up those who may be at risk of this Glaucoma by examining the front of the eye- those at risk often have a shallow anterior chamber- the lens in the eye is closer than normal to the back of the cornea, and this causes the angle between the iris and cornea to be narrowed.
If an individual is felt to have a significant risk of angle closure, preventative treatment can be performed, again often using a laser to ensure the Aqueous fluid can always reach Schlemm’s drainage canal.