What is glaucoma?
Normal Optic Nerve Glaucoma Optic Nerve
Normal Visual Field
Glaucoma Visual Field Loss
There is a fluid called ‘aqueous’ which is secreted by a structure called ‘ciliary body’ located behind the iris. Aqueous passes through the pupil to bring nutrients to the cornea. Aqueous is then drained out of the eye via the trabecular meshwork, situated in front of the iris. You can imagine the iris as a wall separating the ciliary body and trabecular meshwork. The pupil can be imagined as the door where aqueous passes through. Any impediment in the flow of aqueous can cause elevated pressure in the eye. This can damage the nerve and cause the field of vision to constrict. Glaucoma can be classified into open angle and narrow angle.
How is glaucoma detected and monitored?
There are many ways to measure the intraocular pressure (IOP). It can be non-contact such as an air puff or uses an instrument that touches the eye (applanation tonometry). The doctor will also use another instrument on the eye (gonioscopy) to check whether it is open angle or narrow angle. This helps to determine the treatment. An ultrasound probe is also used on the eye to measure the thickness of the cornea (pachymetry).
In addition to measuring the intraocular pressure (IOP), automated visual field and Optical Coherence Topography (OCT) are used to monitor glaucoma. Visual field monitors for field of vision. OCT measures the thickness of the nerve fiber layer.
Humphrey Visual Field
Optical Coherence Topography
How is glaucoma treated?
They lower the intraocular pressure by decreases aqueous production or drains aqueous out of the eye via a different pathway.
There are different types of lasers used in ophthalmology, two of which are used to treat glaucoma. They lower the intraocular pressure of the eye by different mechanisms depending on the causes of glaucoma.
Selective Laser Trabeculoplasty
This is a laser applied to the trabecular meshwork to help the aqueous to drain better via the trabecular meshwork. This is used in treatment of Open Angle Glaucoma.
Aqueous flow can be blocked at the pupil such as by a growing cataract. This will cause sudden or gradual rise in intraocular pressure. A small hole is created in the iris to release the pressure. You can imagine this as a valve in a pressure cooker that lets out steam to release the pressure. This is used in treatment of Narrow Angle Glaucoma
iStent This is a shunt inserted into the trabecular meshwork to bypass the resistance in the trabecular meshwork. Usually 2 shunts are needed and patients do not feel the shunt. It helps to decrease the number of eye drops required in the treatment.
Trabeculectomy This is a surgery that creates a fistula that drains aqueous outside the eye.
Seton Procedure This is a surgery that inserts a tube into the eye to drain the aqueous outside the eye.
Cyclophotocoagulation This procedure is performed when all of the above treatment fails. It uses laser to damage the ciliary body so that it produces less aqueous.
Dr. Chiu will tailor the treatment plan according to your condition and monitor you with different tests. Dr. Chiu will also work closely with your optometrist to ensure you get the best care.