What is Glaucoma?
Glaucoma is a serious eye condition in which the optic nerve gets damaged. The optic nerve connects the retina with the brain and carries visual signals. Once damaged the regeneration of the nerve is not possible. Glaucoma leads to irreversible vision loss and even blindness if not treated in time.
There are 4 major types of Glaucoma (see below for more details on different types of Glaucoma)
Primary Angle closure Glaucoma (also called Closed angle Glaucoma)
Primary Open angle Glaucoma
What are the symptoms of Glaucoma?
The symptoms of Glaucoma vary depending on the type - while Angle-Closure Glaucoma presents some symptoms (see below for more details), Open-angle Glaucoma does not present many symptoms, especially in the early stages, and for this reason Glaucoma is called the " Sneak Thief of Sight".
It is very important to get your eyes examined regularly for Glaucoma by a qualified Glaucoma specialist to detect Glaucoma early - Vision loss due to Glaucoma cannot be reversed so early diagnosis is crucial.
What causes Glaucoma?
In a normal eye, fluid known as ‘Aqueous Humor’ is continually produced inside and drains out through what is called the ‘Angle’ of the eye. Aqueous Humor is unrelated to the tears which are on the outside. The Angle of the eye is the anatomical portion of the eye between the peripheral cornea and the iris and contains trabecular mesh work for draining the Aqueous Humor. If the drainage channels of the eye do not work properly it leads to more fluid in the eye and thereby more pressure also known as Intraocular Pressure (IOP). The exact mechanism varies by type of Glaucoma e.g. in Open Angle Glaucoma the trabecular mesh work is faulty and doesn't allow for drainage thereby building an increased IOP whereas in Angle Closure Glaucoma the Iris (coloured part of the eye) is pushed or pulled up against the trabecular mesh work, thus causing a mechanical block and raising the IOP.
Glaucoma has several risk factors
IOP: The most important and most common of all the risk factors is the Intraocular Pressure (IOP). It is the pressure exerted by the eye fluid called aqueous humor inside the eye. IOP is a range, not a fixed number, and varies throughout the day. The normal IOP is in the range of 10-21 mm of Hg. The higher the pressure the higher are the chances of developing Glaucoma. IOP is the only risk factor that can be controlled and is used for treatment.
Family history: Most Glaucoma's are hereditary. If members of the immediate family have Glaucoma the risk increases many fold.
Age: The incidence of Glaucoma increases with age. Older age is not only a risk factor for diagnosis, but also for its progression. Aging likely contributes to the vulnerability of the optic nerve over time. So an aged optic nerve is less able to withstand a higher IOP. With age the space inside the eye available for the circulation of the fluid may get smaller and hence pressure can increase.
Race: Asians are more likely to develop Angle Closure Glaucoma. Africans have more of the Open angle type of Glaucoma. Japanese have normal tension glaucoma.
High myopia or hypermetropia: If the power of the eye is too high whether it is minus or plus it poses a risk for glaucoma.
Physical injury to the eye: Severe trauma such as being hit in the eye, can result in immediate increase in eye pressure. Internal damage with injuries can also cause a future increase in pressure. Injury can also displace the lens and damage the angle thereby leading to glaucoma.
Eye diseases: Other eye diseases like inflammation in the eye, thin cornea, retinal detachment, tumors can lead to Glaucoma.
Steroid use: Steroid use both in the form of eye drops and oral use can lead to glaucoma. Steroids should be used under proper guidance from an Ophthalmologist.
Systemic diseases: Diabetes , hypertension, hypotension, migraine and thyroid disease are known risk factors for glaucoma
How is Glaucoma diagnosed?
Process of Glaucoma detection starts with a routine eye examination which includes
Visual Acuity Test: Vision is tested with eye charts
Non-Contact Tonometry: The intraocular pressure is checked with a Non-Contact Tonometer
Slit lamp examination: Eyes are examined under magnification. This helps in optic nerve evaluation. If required, eyes are dilated to get a detailed view of retina.
Based on the findings from the routine examination, if the doctor feels that you may be a glaucoma suspect, next set of tests are conducted
Applanation Tonometry: This is the gold standard for measuring intraocular pressure.
Pachymetry / Central Corneal Thickness Test: In this the Corneal thickness is measured. Corneal thickness is important because it can mask an accurate reading of Intraocular Pressure - actual IOP may be underestimated in patients with thinner CCT, and overestimated in patients with thicker CCT. IOP reading is corrected based on the findings from this test.
Gonioscopy: This enables the doctor to check if the drainage of the aqueous humour (intraocular fluid) is hampered by angle structures.
Perimetry / Visual Fields Test: This test provides a measure of the peripheral vision which is typically the first casualty of Glaucoma
In addition to the above, certain tests may be required to confirm the diagnosis of Glaucoma and establish a baseline for future follow-ups, these may include one or more of the following
Optic Disc Photograph: This helps in picking up structural changes and determining change over a period.
OCT (Retinal Nerve Fibre Layer Analysis) OR Heidelberg Retina Tomograph (HRT): These pick up early structural changes in the optic nerve via fast and reproducible scans. These are helpful in picking up Glaucoma early and are also used to monitor progression.
How is Glaucoma treated?
As stated earlier, vision loss due to Glaucoma cannot be reversed. Glaucoma treatment is aimed at slowing down or stopping the progression of the disease and this is achieved by lowering the Intraocular Pressure. In the early stages, most Glaucoma responds well to eye drops - some decrease the fluid production, others increase the filtration to lower the intraocular pressure. Sometimes oral medicines may also be prescribed. In some cases, Laser treatments (Laser peripheral Iridectomy and Laser Trabeculoplasty) are required. For cases that do not respond to medical or laser therapy, Trabeculectomy surgery is an option which creates a new opening for the fluid to leave the eye.
For complex/complicated cases of Glaucoma, Shunts/Valves are the treatment options. Some of the recent surgical advances are in minimally invasive glaucoma surgery (MIGS) using implantable devices that can be combined with cataract surgery to control IOP. The most used is the ‘i-stent’ inject which is being used in clinical trials, the results so far seem to be promising.
What is Open angle Glaucoma?
Open angle Glaucoma type has a wide and open angle between the Cornea and the Iris, as it normally should be. It is caused by the clogging of the trabecular mesh work which acts like a sieve, and results in increased pressure. Open angle Glaucoma develops slowly over a period of years and is a lifelong condition. Open-angle Glaucoma is the most common form of Glaucoma and it does not present many symptoms in the early stages. Most people with this type of Glaucoma may feel fine and may not notice any change in their vision at first as the initial loss happens on the periphery. The vision may stay sharp and full 6/6 until late in the disease. By the time a patient is aware of the vision loss, the disease is usually quite advanced. Without treatment, it can lead to blindness.
What is Angle-closure Glaucoma?
Angle-closure or Closed-angle Glaucoma type has a narrow angle between the Cornea and the Iris. The entire drainage canal gets blocked, with sudden increase in pressure. Angle-closure Glaucoma develops quickly over a short period of time with a sharp rise in pressure. Angle-closure Glaucoma is more prevalent among Indians and it has symptoms which are usually noticeable. It demands immediate medical attention.
There are 3 sub-types of Angle-closure Glaucoma
Acute angle closure Glaucoma: If the angle of the eye closes suddenly, symptoms are severe and dramatic. One can experience pain, headache, vomiting, colored halos, blurred vision. This form is known as Acute angle closure Glaucoma. Acute angle closure Glaucoma is a medical emergency and immediate treatment is warranted as IOP is very high and can lead to optic nerve damage and vision loss.
Intermittent/ Subacute angle closure Glaucoma: The angle may also close intermittently and may be confused with open angle glaucoma, due to lack of symptoms. People with subacute angle closure glaucoma may have mild pain , blurring of vision and colored halos. These may resolve on its own as the angle reopens. IOP may be normal in these patients.
Chronic angle closure Glaucoma: May present with very few symptoms and only headaches may be there. The angle progressively closes and the IOP becomes high leading to optic nerve damage.
Laser Iridotomy is the definitive treatment modality for angle closure glaucoma - there is no medical treatment which can treat angle closure Glaucoma. In people with subacute/ intermittent and chronic angle closure glaucoma Laser Iridotomy is done as the first step to allow the closed angle to open up. Medications are used to get the IOP under control clearing the way for the Laser procedure. A laser beam is used to make a hole in the Iris to open up the narrow or closed angle and re-establish a normal drainage. It is also used as prophylactic treatment in angle closure where the glaucoma is not set in so as to prevent the risk of having an acute angle closure glaucoma. Often angle closure presents in one eye only, but both eyes are treated as they are similar anatomically and have a threat of angle closure. The procedure has a good safety profile and is painless. No special precautions are necessary after the laser, however some eye drops are advised for a period of 7-10 days.
Laser Iridotomy may cause a rise in IOP temporarily, so a follow up visit is essential to make sure IOP has settled and more importantly to see if the hole created is working properly. Additional pressure lowering medication may be added or removed from the prescription. Very rarely a second sitting for the laser may be required if the Iridotomy is not full thickness after the first sitting.
Laser Gonioplasty may be required in a few cases where Iridotomy is not possible. It is used as a temporary measure to open the angle and then proceed with Iridotomy.
In cases where the acute attack has been going on for a long period of time without adequate treatment or there are repeated attacks and more scarring is present leading to permanent closure of angle, surgery may be required. The surgery creates a window for the fluid of the eye to drain out of the eye thereby decreasing IOP. Most commonly done surgery is Trabeculectomy. In few patients lens extraction may be necessary to open the angle.
Regular eye exams help in identifying the people more prone for angle closure glaucoma. High risk individuals can be treated with a laser Iridotomy to prevent an acute angle closure glaucoma. Other eye of the patient who has had an attack can be treated. With early detection and treatment angle closure glaucoma has a favorable outcome. Many times after the laser no medications are needed. However, vision loss can occur without immediate treatment.
What is Normal tension Glaucoma?
It is a common form of primary open angle glaucoma in which the IOP elevation is not seen. The damage to the optic nerve takes place in spite of normal pressure in the eye. The causes of Normal Tension Glaucoma are not known for some reason the optic nerve is susceptible to damage due to vascular reasons.
Have more questions about Glaucoma? Schedule a consultation with our Glaucoma Specialist Dr. Aditi Agarwal
Advanced Glaucoma Care at Krishna Netralaya includes Complete Diagnostics (Applanation Tonometry, Gonioscopy, Perimetry/Visual Field Test, Pachymetry/Central Corneal Thickness Test, OCT/Retinal Nerve Fibre Layer Analysis etc.), Medical and Laser Treatments, as well as Surgical Treatments (Trabeculectomy, Ahmed Glaucoma Valve Implantation etc.)
Disclaimer: All information, provided above is for informational purposes only and is not intended to serve as a substitute for the consultation, diagnosis, and/or medical treatment of a qualified physician or healthcare provider. Read our full disclaimer here.