First let us try and explain the structure of the eye. The ciliary processes makes the fluid that occupies the front part of the eye. These ciliary processes are attached to the ciliary body. And this ciliary body is present behind the iris which is the brown part of your eye. Acute narrow angle glaucoma occurs in patients who have a shallow space between the cornea at the front of the eye and the colored iris that lies just behind the cornea. This space is known as the anterior chamber.
As the eye ages, the natural lens behind the pupil grows thicker. Also as the eye ages the pupil becomes smaller, restricting the flow of fluid to the drainage site. The drainage site is at a place between the back part of the cornea and front part of the iris. It’s also called the angle. The actual name of the structure that drains the fliud from the eye is called the trabecular meshwork.
If the pupil becomes smaller and the lens thicker there may arise a situtation where the round pupil presses against the lens which is just behind it. If this happens, fluid flow from behind the iris through the pupil to the front of the iris stops. The fluid can build up behind the iris, pushing the iris forward like a sail of a boat. This ballooning of the iris can block the channel (angle) that allows aqueous fluid to drain. Because of this closed angle the fluid outflow from the eye stops. A rapid rise in intraocular pressure can occur.
This rapid rise in pressure is known as acute angle closure glaucoma. If left untreated this acute rise of eye pressure can significantly damage the optic nerve. This would result in irreversible loss of vision. Symptoms of acute angle closure glaucoma are blurring of vision, redness and severe pain.
WHO UNDERGOES YAG PI LASER EYE SURGERY ?
We examine the eye pressure as a routine check up in all patients who come in for an eye examination at Eye Solutions, Mumbai, India. Of course we also do a detailed eye examination which includes vision check and glass power check. When we find raised eye pressure we first ascess the angle of the eye. If this angle is narrow or the glcuaoma specialist feels that the narrow angle may be blocking the path of eye fluid on its way out, he may consider the Yag PI laser.
Sometimes we see narow angle suspects where the angle appears narrow and pressure is borderline. There may also be positive family history of glaucoma eye disease. In these patients too, Yag laser treatment may be done. These patients are known as primary angle closure suspects. In other words having a narrow angle is a risk factor for developing acute angle closure glaucoma.
HOW DOES THIS LASER TREAT THIS TYPE OF GLAUCOMA ?
As mentioned previously Yag PI full form is Yag Peripheral Iridotomy. This laser makes a new opening or hole in the iris to allow the aqueous fluid to move more easily to the drainage site. The iris is the coloured part of the eye. Once the aqueous starts flowing more easily and the eye pressure decreases. One can read more about glaucoma here but you should know that once the pressure decreases the damage to the retinal nerve fibre layer reduces. In other words the optic nerve head stop getting damaged.
Since the opening is at the very edge of the iris we call it “Peripheral iridotomy”. This laser treatment for this eye disease is usually performed in the doctor’s office. It is generally performed on both eyes because the risk of developing the condition in both eyes is high.
HOW IS GLAUCOMA LASER SURGERY DONE ?
We call the patient 30 min before the Yag PI laser scheduled time. Once the patient arrives we start putting Pilocarpine eye drops in one or both eyes. These drops constrict the pupil or make it smaller. This stretches the peripheral iris so that the procedure is easier and more effective. These drops may cause a feeling of heaviness or eyestrain. Fortunately this is only temporary and subsides over the next few hours.
Once that is done, the patient sits in front of the laser machine and places his or her chin on the chin rest. Anaesthetic drops are put in the eye to numb the eye and then a contact lens is placed on the surface of the eye. This may sound scary but because of the numbing drops this step does not hurt.
Then the doctor looks for spot on the iris which is thin. Once the spot is found the lens is rotated to make sure it is in focus and the laser beam is fired. Usually 2-4 shots may be needed. The doctor knows that its done when he sees a burst of iris pigment flow into the Anterior chamber. Eye doctors and glaucoma specialists also call this as pigment dispersion into the anterior chamber.
The entire procedure takes 5 to 7min for each eye. It is an outpatient procedure and a stand-alone procedure. Nothing else is needed at that point in time.
WHAT ARE THE PRECAUTIONS AFTER THE YAG PI ?
Once the laser treatment is done the patient is prescribed certain eye drops. These eye drops are antiinflammatory and help in reducing the inflammation that occurs due to the laser. As explained earlier, your eye doctor has caused an injury to your eye with that laser and the body is going to react to it. The drops will help in reducing that reaction.
Sometimes, because of a small amount of bleeding the vision may become blurred. Even if this happens there is nothing to worry about as the blood clears up in a week and vision should return to normal.
CAN THE LASER PROCEDURE BE NEEDED AGAIN ?
Once the iris opening is made it is not necessary that it will remain open forever. The reason for this is that the body considers this as an injury. Like for any other injury the body tries and repairs this injury. The repairing may happen by healing of the iris tissue and attempt to close the yag laser created opening. There is 20-30 % chance of the opening closing. If that happens the laser may have to be repeated again.
WHAT HAPPENS IF THE PRESSURE IS NOT CONTROLLED AFTER THE LASER ?
It is not necessary that the pressure redcues to the level that your treating eye doctor wants after the laser. So even though the pressure has gone down it has not reached a level that your doctor wants. In this situation your glaucoma specialist may prescribe certain eye drops that would help in reducing the pressure further. This is medical management of glaucoma
or using eye drops to lower the pressure.
If the pressure does not reduce to the target level with glaucoma eye drops your doctor may suggest you to get a glaucoma filtering surgery. This is also known as trabedulectomy
and it is one type of glaucoma surgery.
There is also another option that your dotor may consider if the pressure does not drop to the desired levels. If you also have a cataract, even if the cataract is not very advanced, your doctor may consider performing a cataract surgery. Usually after cataract surgery the pressure reduces by a bit and this may help in reaching the eye pressure target. You can read more about cataract surgery