SLT – an effective choice for glaucoma treatment

Glaucoma is a failure of the eyes to maintain appropriate balance between the amount of intraocular fluid produced and the amount that drains away. It continually takes away a person’s vision without giving any warning. In the early stages of the illness, symptoms may not appear, therefore, people affected by the disease may not know they have glaucoma.

“Up till now, there is no cure for glaucoma. However, early diagnosis and continuing treatment can slow down or prevent further vision loss. Today, Bangkok Hospital has a new technology called Selective Laser Trabeculoplasty (SLT) as an option for treating patients with glaucoma. SLT equipment allows low-frequency lasers to treat specific cells selectively, leaving untreated portions of the trabecular meshwork intact,” explained Dr.Yupin Leelachaikul, Glaucoma Specialist, Bangkok Eye Center, Bangkok Hospital.

Unlike the former Argon Laser Trabeculoplasty (ALT) which involves using a laser to open up the drainage angle of the eye and is harmful to surrounding cells and becomes less effective with repeated treatments, SLT can be performed frequently, takes only about five minutes each time and yet potentially offers immediate and long-lasting results.

“Before using the SLT equipment, we have to prepare glaucoma patients by applying topical anaesthetic drops and placing contact lenses on the eyes. The preparation process takes 20-30 minutes. After the laser process is done, patients may feel slight irritation in their eyes and their vision may be slightly blurry. The irritation and blurriness will fade in hours. Patients don’t have to be admitted to hospital and it is not necessary to cover the eyes. After leaving the hospital, they can resume normal daily activities but need to use anti-inflammatory drops for a few days,” continued Dr.Yupin.

SLT is helpful for treating people who cannot tolerate medications, especially eye drops, which usually generate some side-effects, irritation and sometimes conjunctivitis. It also benefits older adults who are not able to use medicines by themselves because just physically getting a drop in the eyes can be very difficult for them.

When laser surgery does not successfully lower eye pressure, or the pressure begins to rise again, doctors may recommend conventional surgery to open a tiny drainage hole in the sclera. The new drainage hole allows fluid to flow out of the eyes and helps lower eye pressure to reduce damage to the optic nerve.

“Glaucoma is a disease that comes along with increasing age. As such, an annual eye check-up is recommended after the age of 40. With early diagnosis, blindness and extensive sight loss can be prevented in most people with glaucoma,” advised Dr.Yupin.

Types of glaucoma

There are five types of glaucoma, including primary open angle glaucoma, primary angle closure glaucoma, secondary glaucoma, normal tension glaucoma and paediatric glaucoma.

Primary open angle glaucoma

Primary open angle glaucoma is the most common form of glaucoma. It is a slowlydeveloping condition in which pressure within the eye rises because the drainage channels cannot drain fluid. The eye pressure rises very slowly and there is no pain to warn of a problem, even though the optic nerve is being damaged. The damage does not necessarily occur in the same part of the field of vision in both eyes. It is important to diagnose and start treating early on, before it has advanced to extensive sight loss.

Primary angle closure glaucoma (sometimes called ‘acute glaucoma’)

Primary angle closure glaucoma is often found in Asian people. It may either begin suddenly or develop slowly.

This kind of glaucoma develops when aqueous humour access to the trabecular meshwork is blocked because the iris has come forward, causing the drainage angle to ‘close’. The fluid cannot escape from the eye and the pressure rises. It must be treated immediately. If treatment is delayed, there is often permanent damage to the eye and sight is irretrievably lost.

Patients sometimes experience a series of mild attacks of angle closure. Called subacute attacks, they often occur in the evening. Vision may seem misty, with coloured rings around white lights and there may be some discomfort and redness in the eye. The patients may also feel sick.

Secondary glaucoma

This kind of glaucoma can either be of primary open angle or primary angle closure in nature. In other words, eye pressure may rise in different ways. It has an identifiable cause that is ‘secondary’ to another condition. Besides treating the actual glaucoma, the condition that has caused the glaucoma must also be addressed. The eye may then return to a normal state and not require further treatment. If the eye has been damaged, ongoing glaucoma treatment will be required.

Normal tension glaucoma

Normal tension glaucoma is also known as lowtension glaucoma or normal pressure glaucoma. In this type of glaucoma, the optic nerve is damaged even though intraocular pressure (IOP) is not very high. Doctors do not know why some people’s optic nerves suffer damage even though pressure levels are in the “normal” range (between 12-22 mm Hg).

Those at higher risk with this form of glaucoma are people with a family history of normal tension glaucoma, people of Japanese ancestry, and people with a history of systemic heart disease such as irregular heart rhythm.

Pediatric glaucoma

Pediatric glaucomas consist of congenital glaucoma (present at birth), infantile glaucoma (appears during the first three years), juvenile glaucoma (age three through the teenage or young adult years), and all the secondary glaucomas occurring in the pediatric age group.

Congenital glaucoma is present at birth and most cases are diagnosed during the first year of life. Sometimes symptoms are not recognised until later in infancy or early childhood.

The range of treatment is very different from that for adult glaucoma. It is very important to catch pediatric glaucoma early in order to prevent blindness.

Are you at risk of glaucoma?

Everyone is at risk of glaucoma. However, certain groups are at higher risk than others. Risk factors for developing glaucoma include aging (over 40 years of age), high intraocular (eye) pressure, family history of glaucoma in a first degree relative, race (Blacks), high myopia (near sightedness), diabetes, heart disease, hypertension, eye injury or surgery, history of steroid use, sleep-related breathing disorder and gender (male)..