patient information

 Glaucoma can be divided into the open and closed angle forms. The angle is the part of the eye through which fluid drains away. If if tis ‘narrow’ then the pressure in the eye can rise and cause damage to the optic nerve and then to the vision.

Angles can be examined clinically by looking directly at them using a gonioscope and/or by OCT scan. In each case, if deemed to be narrow then there are two ways to open the angles.
First, the YAG laser peripheral iridotomy (YAG PI) is something that has been performed for many years and bypasses the normal pathway of fluid flow around the eye by creating an ‘oberflow valve.’

Second, lens extraction/cataract surgery can also have the same effect and has been advocated in an important study published recently in the Lancet. This is usually reserved for patients over 55 years with a hight ocular pressure.

The advantage of the iridotomy is that it can be done easily in the outpatient clinic on both eyes at the same time and as it does not involve cutting into the eye, there is no risk of infection getting inside the eye. The laser uses the transparent properties of the ocular surfaces to penetrate the eye and make a small hole or ‘iridotomy’ in the iris. Fluid can drain from the back of the eye through to the from drainage angle unimpeded by obstruction between the iris and lens.

Lens extraction by contrast is an operation, effectively the same as cataract surgery. By removing the natural lens and implanting a silicone thin lens, it creates more space for fluid to get from the back to the front part of the eye without obstruction. It is effective and in selected cases may offer more long-lasting benefits to the narrow angle patient, particularly with raised ocular pressure. If there is a cataract present then this operation will also treat this and improve the vision. If not, as patients with narrow angles are often long-sighted or ‘hypermetropic,’ this surgery will also potentially reduce the need for wearing glasses or contact lenses.