Sight Stealer

Millions of people go blind from glaucoma every year. It is a leading cause of irreversible blindness worldwide. In 2013, the number of people with glaucoma in Asia was 51.32 million; this number is estimated to increase to 80.87 million in 2040. The prevalence of glaucoma among the Singapore population in adults aged 40 years and older is 3.2%. This percentage increases with age, and reaches almost 10% for those older than 70 years. Thus, glaucoma awareness is essential in our ageing population. Asymptomatic in the early stages, this condition is often undetected until there is extensive visual field loss; hence, its nickname: the silent thief of sight.

WHAT IS GLAUCOMA?
Glaucoma is an eye disease that is often associated with increased eye pressure that causes damage to the opticnerve. The optic nerve is responsible for transmitting visual information from the eye to the brain. Our eye produces a clear fluid, known as aqueous humour, which provides nutrients to the eye and maintains its shape. Aqueous humour is continuously produced and flows out of the eye from the drainage angle. There is a delicate balance between fluid production and fluid drainage. Glaucoma is caused by a build-up of fluid within the eye when the drainage system is not functioning properly, resulting in increased eye pressure and damage to the optic nerve.

TYPES OF GLAUCOMA
There are four major types of glaucoma. They include:

1. Primary Open Angle Glaucoma
Primary open angle glaucoma (POAG) is the most common type of glaucoma. In POAG, the drainage angles are open, but the drainage system is not  working well. This causes the fluid to not drain well from the eye, resulting in high eye pressure.
2. Primary Angle Closure Glaucoma
In primary angle closure glaucoma, the drainage angles are narrow or closed. The fluid is unable to reach the drainage system, which brings about high eye pressure.
3. Secondary Glaucoma
Secondary glaucoma refers to high eye pressure that is caused by an identifiable cause, such as an eye injury, infection, inflammation, very mature cataract, subluxed cataract, or following an eye surgery. As with primary glaucoma, secondary glaucoma can be open-angle or closed-angle.
4. Congenital Glaucoma
Congenital glaucoma is a type of glaucoma that occurs in babies due to the drainage system not developing properly.

RISK FACTORS
Glaucoma can affect anyone. However, even though everyone is at risk of getting glaucoma, there are certain risk factors which can further increase the chances of a person developing the condition. They include the following:

  •  Old age
  • High eye pressure
  • Family history of glaucoma
  • Myopia (short-sightedness)
  • Hypertension
  • Diabetes mellitus
  •  Long-term steroid use
  •  Eye injury
  • Obstructive sleep apnea
  • Migraine

SYMPTOMS
Most forms of glaucoma develop gradually as the build-up of fluid pressure in the eye happens slowly. Patients lose their peripheral vision slowly, and central vision is usually maintained until late in the disease. Most patients do not have any symptoms during the early stages of the disease as the process is usually painless. Also, the gradual loss of peripheral vision is not usually noticed as central vision is generally used for most tasks. As a result, the disease is undiagnosed in up to 70% of glaucoma cases. As the disease progresses, patients may develop tunnel vision or loss of central vision. It may even result in blindness at end-stage disease. Vision loss from glaucoma cannot be restored.

On the other hand, acute glaucoma is less common and occurs when there is a sudden severe rise in eye pressure. The symptoms include eye pain and redness, blurred vision, and seeing haloes around light. This condition may also be associated with headache, nausea and vomiting.

It should be noted that glaucoma can occur in one or both eyes.

CAN GLAUCOMA BE PREVENTED?
Glaucoma cannot be prevented. However, early detection will allow for timely treatment to prevent further damage to the optic nerve and preserve the remaining vision. Since early glaucoma is often asymptomatic, it is important to go for regular eye examinations from the age of 40, and earlier if there are risk factors involved.

DIAGNOSIS
Glaucoma can be diagnosed with a comprehensive eye examination. This includes a slit lamp examination, eye pressure measurement, gonioscopy to check the drainage angles, optic nerve head examination, visual field testing, optic nerve head imaging and corneal thickness measurement.

MANAGEMENT
Unfortunately, glaucoma cannot be cured. It is a chronic condition that requires regular life-long monitoring and treatment. The aim of treatment is to reduce the eye pressure to a safe level for the eye and preserve the remaining vision. Treatment plans are individualised, and will differ depending on the type of glaucoma and the individual patient’s condition. Your Ophthalmologist will advise you on which treatment option is best for you.

TREATMENT OPTIONS
Eye pressure can be lowered with a number of treatment  options, including medications, laser treatment, surgery, or a combination of these.

  • Glaucoma Medications
    There are different types of medications in glaucoma treatment. They lower the eye pressure by reducing fluid production in the eye, or increasing fluid drainage. Eye drops are commonly used, and they must be instilled daily. They can be used long-term. Oral or intravenous medications are sometimes used to lower the eye pressure quickly. These can be associated with serious side effects and are used for a short period of time while awaiting surgery or a more definitive treatment.

  • Selective Laser Trabeculoplasty
    Selective laser trabeculoplasty (SLT) is a glaucoma laser treatment that causes changes in the drainage pathway to increase fluid drainage and reduce the eye pressure. It is used in patients with mild to moderate open angle glaucoma. After SLT treatment, up to 70% of patients with early to moderate open angle glaucoma remain medication-free for 6 years, with a reduced risk of disease progression. SLT is generally quite safe, and can be repeated if the initial treatment was effective. However, it should be noted that this laser treatment alone is unlikely to be adequate for patients with severe glaucoma.
  • Laser Peripheral Iridotomy
    Laser peripheral iridotomy (LPI) is a glaucoma laser treatment that creates a small hole in the iris, which allows fluid to flow to the anterior chamber and widen the angle, facilitating fluid drainage. This procedure is done for eyes with narrow or closed angles. It reduces the risk of glaucoma progression and acute glaucoma in the eye.
  • Trans-scleral Cyclophotocoagulation
    Trans-scleral cyclophotocoagulation (TCP) is a laser procedure that destroys the cells which produce fluid in the eye. This reduces fluid production in the eye. This procedure is very effective in reducing eye pressure. However, it may be associated with potentially serious complications, and is usually performed in eyes with poor visual potential.
  • Micropulse Trans-scleral Cyclophotocoagulation
    Micropulse trans-scleral cyclophotocoagulation (MPTCP) is a newer type of laser procedure, where the laser energy is delivered to the eye in short bursts in an onand-off cyclical fashion. The overall laser energy used is lower than conventional TCP. It decreases eye pressure by increasing fluid drainage from the eye. MPTCP has a good safety profile, but its eye pressure lowering is less than conventional TCP.
  • Trabeculectomy
    Trabeculectomy is the most commonly performed glaucoma surgery worldwide. This surgery creates a new drainage channel in the white wall (sclera) of the eye, which provides an alternative route for the fluid to drain out. The fluid is collected in an area called a bleb underneath the conjunctival covering of the eye, and is absorbed into the tissue around the eye. The bleb is covered by the eyelid and is usually not visible. Trabeculectomy is associated with potentially serious complications, and intensive post-operative care is often required in the first few months. Most patients achieve good pressure lowering over many years. However, in some cases, the surgery may work less well after a period of time, depending on the type and severity of glaucoma and the scarring response of the patient.
  • Tube Surgery
    Tube surgery is another conventional form of glaucoma surgery. It involves implanting a drainage device to lower the eye pressure. The device consists of a tube that is inserted into the eye to drain fluid out, and a plate that is sutured onto the white wall of the eye that acts like a reservoir for the drained fluid. This surgery is associated with potentially serious complications. It is done when medications, laser or other forms of surgery have failed, or if there is a high risk of failure with other procedures.
  • Minimally Invasive Glaucoma Surgery
    In recent years, a new group of surgical procedures known as Minimally Invasive Glaucoma Surgery (MIGS) has emerged. These procedures include inserting a microstent or drainage shunt to increase fluid drainage from the eye and lower the eye pressure. Compared with conventional glaucoma surgery, MIGS is less invasive, have a higher safety profile, and allows faster recovery. They can be performed together with cataract surgery or as a stand-alone procedure. They can also be performed in patients who are intolerant to glaucoma eye drops.

GETTING YOUR EYES CHECKED FOR GLAUCOMA
If you experience symptoms of acute glaucoma, see an Ophthalmologist immediately as you need treatment as soon as possible. If you are experiencing loss of peripheral vision or blurring of vision, do also see an Ophthalmologist early for further evaluation.

For people without any symptoms or risk factors, the  American Academy of Ophthalmology recommends a baseline comprehensive eye examination at age 40. If you have risk factors for glaucoma, you should go for regular eye examinations earlier. Please check with your Ophthalmologist on how often you need your eye examinations.

Although we cannot prevent or cure glaucoma, early detection and treatment of glaucoma are important to prevent further irreversible damage to the optic nerve and resultant blindness. With appropriate treatment, the majority of glaucoma patients will be able to retain good  vision in their lifetime.

 

@PRIME

 

 

Author

  • Dr Annabel Chew

    Senior Consultant Ophthalmologist,
    Lang Eye Centre

    Dr Annabel Chew is the Senior Consultant Ophthalmologist at Lang Eye Centre at Mount Elizabeth Novena Specialist Centre, Singapore. She was formerly a Senior Consultant Ophthalmologist at the Singapore National Eye Centre, Clinical Director of the Primary Eyecare Clinic and Community Eyecare Clinic, Clinical Assistant Professor at Duke-NUS Graduate School of Medicine, Clinical Lecturer at NUS, and Adjunct Clinician Investigator at the Singapore Eye Research Institute.

    Dr Chew specialises in Cataract Surgery, and the treatment of general ophthalmology conditions. She sub-specialises in Glaucoma, and has experience in managing patients with Complex Glaucoma. Her clinical interests include Glaucoma Lasers, Trabeculectomy, Tube Shunt Surgery, Minimally Invasive Glaucoma Surgery, Cataract Surgery, and Implantation of Toric and Multifocal Lenses for the Correction of Myopia, Astigmatism and Presbyopia.

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