Laser Peripheral Iridotomy

Laser Peripheral Iridotomy

Anatomy of the drainage system inside the eye

The Cornea: The front transparent part of the eye ball is called the cornea – it represents the continuation of the white of the eye – the sclera. The sclera is the outer part of the eyeball that gives it a “ball” shape and protects the content of the eyeball.

The cornea plays important role in focusing the light rays onto the retina.

The Iris: This is the coloured part of the eye in the middle of which there a whole that forms the pupil. The pupil is the diaphragm that regulated the amount of light going inside the eye.

The Anterior chamber: This is the fluid space located between the cornea and the iris. At the angle, formed between the cornea and the iris, there is a structure called Trabecular Meshwork that helps draining fluid from inside the eye to the vein outside it.

The Lens: This is the structure located behind the iris and helps focusing the light rays onto the retina.

The Ciliary Body: This is the continuation of the iris backward inside the eyeball and it is formed by muscles that helps the lens to “zoom” for distance and near, and by special cells that produce intraocular fluids (intraocular means inside the eye), containing nutrients and oxygen to nourish some intraocular structures.

Intraocular Fluid is produced in the ciliary body then flows between the lens and the iris into the anterior chamber where it gets drained out through the trabecular meshwork

  • With age, the lens inside the eye grows in size. As it grows, it occupies more space and it sometimes starts pushing the iris forward. Eventually, the growing lens can push the iris forward enough that sometimes the pushed forward iris blocks the trabecular drainage meshwork.
  • This happens because the enlarged lens becomes in tight contact with the back part of the iris, making it difficult for the intraocular fluid to flow toward the anterior chamber. That leads to entrapment of fluid behind the iris. This entrapped fluid pushes the peripheral part of the iris forward gradually blocking the trabecular meshwork
  • If the trabecular meshwork suddenly becomes blocked completely, patients develop acute angle-closure glaucoma which is a painful, sight threatening sudden rise of the pressure inside the eye. If the intra-ocular pressure rises up gradually, patients can get painless but sight threatening in long term condition called chronic angle closure glaucoma.

 

Acute Angle Closure

  • The trabecular drainage meshwork of the eye becomes suddenly blocked by the pushed forward iris, and the fluid inside the eye suddenly becomes entrapped in the eye.
  • When this happens, the pressure inside the eye rises very quickly to very high levels.
  • This is a very painful and potentially a blinding condition.

 

Chronic Angle-Closure

  • This is a slow version of acute angle closure when the blockage of the trabecular drainage meshwork happens slowly over months or years. The patients are not aware of this and have no symptoms.
  • This is usually spotted by an optician or a doctor on routine eye examination

 

Subacute angle closure

  • These are short episodes of acute angle closure that resolve on their own. They give symptoms like headaches and eye pain for a short period of time especially in darkness, however they do not last to develop the full picture of acute angle closure and they resolve spontaneously.
  • Patient with subacute angle closure are at risk of having acute angle closure.

 

Laser Peripheral Iridotomy?

  • Laser peripheral iridotomy creates a hole in the peripheral part of the iris through which the entrapped behind the iris fluid flow to the anterior chamber bypassing the tight contact between the iris and the lens
  • The hole is very small, invisible without a microscope and located inside the eye, hence there is no risk of leakage outside the eye.

 

Indication for laser peripheral iridotomy

  • To prevent acute or chronic angle closure explained above. Sometimes, it helps lowering the intraocular pressure. It is not a guaranteed treatment, but it reduces dramatically the risk of developing acute angle-closure glaucoma and it is the first line treatment for acute angle closure as well

 

Alternatives to laser

  • Prior to the invention of YAG lasers and laser iridotomy, surgical iridectomy was the treatment of choice. This is an operation where we cut a full-thickness small piece of the peripheral iris to achieve the same effect as we get with laser iridotomy. Like any surgery, this has higher risks than the laser procedure.
  • Rarely, the laser procedure does not work or it is not technically possible to carry out the laser, so we may recommend that you have either surgical iridectomy or more commonly nowadays cataract surgery to remove the lens/cataract that is pushing the iris forward.

 

Peripheral laser iridotomy – the procedure

  • On arrival, you will get some eye drops instilled into the eyes to make the pupil smaller and the laser procedure safer and reduce the power of the laser needed to do the iridotomy (the hole in the iris). Occasionally these drops can give headaches and ordinary painkiller would help in these circumstances.
  • The laser machine looks similar to the machine you are usually examined with at your appointments.
  • Your doctor will numb your eye with anesthetic drops and put a contact lens on the eye. The contact lens focuses the laser, helps keeping the eye still and keeps the eyelids apart so you don’t have to worry about blinking; you continue to blink as normal.
  • Patients’ experiences vary: some say it feels like a pinprick, others say a tapping sensation. Some feel a sensation at the back of their head. The YAG laser is invisible but you might see a red light which is the focusing beam.
  • You generally have both eyes lasered on the same day, but you can ask for each eye to be done on separate occasions.
  • Rarely, if the iris is very thick, we may need to use two separate lasers to carry out the treatment.

 

What should I do about my medication?

All medication, including any regular eye drops, should be taken as usual.

 

The risks and complications of the procedure

Inflammation: The eyes can become red and sore following laser, so you will be prescribed a course of anti-inflammatory eye drops.

Bleeding: The laser makes a small hole in the iris which is a highly vascularised part of the eye, so there is a possibility of bleeding. The bleeding usually is minor (less than one drop in volume), stops almost immediately and does not interfere with the procedure or its chance of success.

High eye pressure: Occasionally, the eye pressure goes up after the laser procedure and later it settles down. If it does, then you will be given the appropriate treatment.

Further Laser: It is very rare for the laser iridotomy to close or to become smaller with time. If the hole shrinks and its size is not satisfactory, then you might need to have it enlarged but again, this is very rare.

 

What should I expect after laser?

  • After the laser procedure, you may feel that the sight is altered slightly for the rest of the day.
  • Most people do not experience discomfort after the laser, but if you do, then you can take some simple painkillers.
  • Some patients experience “floaters” for a few weeks.

 

Post-operative Instructions

I do not recommend driving on the day of the procedure. Otherwise, there are no restrictions following laser peripheral iridotomy. Carry on with all your normal daily activities.