What Causes Permanent Blindness?
The cause of permanent blindness in one eye is not known. There are several theories, but no conclusive evidence. Some doctors believe it could be due to a tumor or other disease affecting the retina. Others think it may be caused by some kind of trauma to the eye itself (like a car accident). Still others have suggested that permanent blindness in one eye might result from a genetic disorder, such as Leber’s congenital amaurosis.
There are many possible reasons why someone would lose their sight in one eye. Sometimes it happens suddenly, sometimes it happens gradually over time. It depends on how much damage was done to the retina and what kind of damage it had.
Some people experience complete loss of vision in both eyes at birth, while others develop partial blindness later in life. People who suffer from certain diseases like retinitis pigmentosa or macular degeneration often experience total blindness in one eye before they reach adulthood.
It is also possible that your condition will improve after treatment. If you have any questions about the cause of your blindness, please contact us today!
Vision Loss and Glaucoma
What is Glaucoma?
Glaucoma refers to a group of eye conditions which cause damage to the optic nerve, leading to gradual loss of vision. The main type of glaucoma is called “open angle glaucoma” and affects the peripheral vision (side vision) in both eyes. It is rarely painful or itchy. Glaucoma is the leading cause of blindness among African-Americans and Hispanics in the United States.
Vision loss due to glaucoma can occur suddenly (acute) or gradually (chronic). Acute vision loss is rare but can happen from a sudden increase in pressure inside the eye, which may occur in some surgical procedures.
What are the Symptoms of Glaucoma?
The National Eye Institute lists the following signs and symptoms of glaucoma:
1. Diminished peripheral (side) vision in both eyes.
One of the first signs of glaucoma is a diminishing or loss of peripheral vision. This often occurs slowly and may not even be noticed until 50% of peripheral vision is gone. Peripheral vision allows you to see objects at the edges of your field of vision.
It is important for driving, catching a ball and other actions.
2. Gradual clouding of the lens of the eye.
This is known as
“optic disk hypenopia.” In this stage, there are no symptoms. However, inside the eye there is gradual damage to the optic nerve due to ongoing increased pressure in the eye.
By the time a person notices visual field loss, approximately 90% of their peripheral vision may already be gone.
3. Pain.
Some types of glaucoma, including primary congenital glaucoma, may sometimes cause eye pain. This type of glaucoma is rare and is present at birth.
4. Severe visual field loss.
Open-angle glaucoma causes a slow, progressive loss of vision over many years. By the time a person notices a visual field loss, approximately 90% of their peripheral vision may already be gone.
What is the Treatment for Glaucoma?
Glaucoma is a chronic (ongoing), irreversible (no cure) disease. Because of this, appropriate treatment and follow-up care are essential. There is no specific treatment to cure glaucoma or to restore vision that has already been lost. However, it can usually be controlled to prevent further vision loss and other complications (such as permanent blindness).
The main goals of treatment are to:
Reduce the amount of fluid produced and eliminate drainage from the eye.
Lower the internal eye pressure. High pressure damages the optic nerve, leading to vision loss over time.
Vision can be saved in most cases of glaucoma if treatment is begun early. The longer you have glaucoma, the more vision you are likely to lose.
The following are the main types of treatment for glaucoma:
1. Medication.
Several types of eye drops or pills can help to control the internal pressure and reduce the production of aqueous humour. In most cases, more than one medication is used to control the eye pressure. Your doctor will determine which combination is right for you based on other health conditions you may have as well as other medications you may be taking.
The goal of medication is to control the eye pressure so that it is as close to normal as possible.
2. Laser surgery.
In this procedure, a small incision is made in the eye to allow a laser beam to be directed at the base of the optic nerve. This flattens the cornea and lowers eye pressure by reducing the production of aqueous humour. It can be performed on one or both eyes.
3. Microincision surgery.
In this procedure, a small incision (of about 0.5 millimetres) is made in the corner of the eye. A tiny tube (called a shunt) is inserted to redirect the fluid away from the eye.
This allows aqueous humour to drain into another area of the body where it can be naturally absorbed, thus lowering eye pressure.
4. Iridotomy.
In this procedure, a small cut (about 0.8 to 1.6 millimetres) is made in the iris (the colored part of the eye) to allow fluid to drain more easily from the eye.
This procedure does not always lower eye pressure. It is rarely used anymore, except in cases of traumatic glaucoma that develops quickly or in very young patients.
5. Glaucoma drainage implants.
In this rare procedure, a tube is implanted under the skin behind the ear. It is then routed through the skin behind the ear and implanted in the eyelid. The tube is attached to a small silicone “bumps” that sit on the eye and drains fluid into the tube, thus lowering internal eye pressure.
6. Shunts.
In this procedure, a surgeon creates a connection between an artery and a vein in the eye and implants a one-way valve in the connection. As blood flows through the eye toward the brain, fluid is directed to flow toward the eye surface where it can be absorbed, lowering internal eye pressure.
7. Trabeculectomy.
In this procedure, a surgeon makes a small hole in the natural “dike” inside the eye (called the trabecular meshwork). This allows aqueous humour to drain out of the eye, thus lowering internal eye pressure.
In some cases, glaucoma can occur as a side effect of a disease or disorder or due to medication. In these cases, treatment is based on the underlying cause or the medication that is causing the problem. For example, if glaucoma is caused by another condition, the underlying cause should be treated and the glaucoma will resolve itself when the condition causing it is treated successfully.
If medications are contributing to developing glaucoma, then the offending agent should be replaced by another drug or discontinued if no suitable replacement exists.
Some of the drugs that can contribute to glaucoma include:
1. Anti-diabetic medications (e.
g. chlorpropamide, tolazamide).
2. Some antidepressants (e.
g. amitriptyline, clomipramine, imipramine, trimipramine).
3. Anti-epileptic drugs (e.
g. diazepam, clonazepam).
4. Medications used to treat Parkinson’s disease (e.
g. levodopa).
5. Some blood pressure medications (e.
g. clonidine, methyldopa).
6. Some anti-ulcer drugs (cimetidine, ranitidine).
7. Some anti-cancer drugs (e.
g. vincristine, vinblastine).
8. Gold preparations (e.
g. aurothioglucose, aurothiomalate) used to treat rheumatoid arthritis.
9. Lithium, a mood stabilizer.
In addition, some people are more likely to develop glaucoma due to their family history, race or certain Pacific Islander heritage.
If you develop new onset eye pain or a sudden increase in eye pressure/headache, please see an eye doctor immediately. This may be the sign of a condition other than glaucoma that needs to be treated immediately. If you have any risk factors for glaucoma, it is essential that you undergo regular eye examinations by an eye care professional and get regular eye tests.
No treatment is necessary for normal tension glaucoma, however, in all other forms of glaucoma, treatment is necessary to lower the pressure in the eye. This allows the optic nerve and the rest of the structures in the eyes to be preserved.
Treatment for glaucoma depends on a variety of factors, including the type and degree of vision loss, underlying cause, your age and general health and other factors at your eye examination.
The goal of treatment for glaucoma is to lower the internal eye pressure. In most cases of glaucoma, medication is used to achieve this goal. In more severe or chronic cases of glaucoma where other treatments are less effective or not an option, surgery may be required to help lower the internal eye pressure.
Currently there are several different classes of medications that can be used to treat glaucoma:
1. Alpha agonists: These medications work by lowering the fluid production in the eyes.
Common brand names of these types of medications include:
a. Apraclonidine (IOPIDINE).
b. Brimonidine (ALPHAGAN).
c. Lotemax (loteprednol, a prednisolone derivative)
2. Beta-blockers: These medications work by blocking certain natural body chemicals that lead to the production of fluid within the eye.
They act on receptors located in different parts of the body. Common brand names include:
a. Timolol (BLOCADERM, TIMOPTIC, others).
b. Betimol (loteprednol, a prednisolone derivative)
3. Carbonic anhydrase inhibitors: These medications prevent the production of a chemical called carbonic anhydrase, which is involved in the formation of fluid within the eye.
They are available as eye drops and ointments. Common brand names include:
a. Diamox (acetazolamide).
b. Zerion (brinzolamide).
4. Corticosteroids: These medications are similar to the natural corticosteroids that our body makes and are used to reduce the production of inflammatory cells in the eye.
They have been available as eye drops and ointments for many years. Brand names include:
a. Pred Forte (prednisolone acetate).
b. Suspension Pred (prednisolone sodium phosphate).
5. Miotics: These medications work by contracting the muscles located in the iris (the coloured part of the eye) and cause the pupil to become smaller.
This allows less light to enter the eye and helps to reduce pressure within the eye. Common brand names include:
a. Apraclonidine (IOPIDINE).
b. Carbaglu (brimonidine, a alpha-agonist).
6. Parasympathomimetics: These medications mimic the effects of a chemical called acetylcholine that are produced naturally within the body.
Acetylcholine acts to reduce the production of fluid within the eyes, and these medications help to reduce the production of fluid in the eye. Common brand names include:
a. Isopto Carpine (pentolinium).
b. IOPamide (pilocarpine).
7. Vasodilators: These medications work by dilating blood vessels, which is thought to increase the outflow of fluid from within the eye.
They are also available as eyedrops or ointments. Common brand names include:
a. Travatan (travofotil).
b. Isopto Phosphate (pipratanol).
When is medication not an option?
If you have been started on or are already taking medication and your pressure continues to increase or if the medication is not controlling your pressure, your doctor may decide that you are a candidate for laser trabeculoplasty or trabeculectomy surgery.
What are my treatment options?
Surgery:
There are several different types of surgery for glaucoma. Some surgeries are more invasive than others. You and your doctor should discuss the risks and benefits of each procedure so you can make an informed decision about what is best for you.
A commonly performed type of surgery is called trabeculectomy. During this procedure, an incision is made within the white of your eye and a hole (trabecula) is cut within one of the channels (trabecular) that drain fluid from the eye. A tube is then placed within this new hole in an effort to increase outflow of fluid. Another common type of surgery is called laser trabeculoplasty. During this procedure, your surgeon uses a laser to create a small opening within one of the fluid channels of your eye.
Medical treatment with medication (including eyedrops or ointment) is another option for lowering intraocular pressure in those who are not good candidates for surgery.
What are the risks?
Risks of any surgery include: bleeding, infection and failure of the surgery to improve vision. Other possible risks of each procedure are discussed during your visit with your specialist.
Who can I contact if I have more questions?
Ophthalmologist
Radial Keratotomy (RK)
What is radial keratotomy (RK)?
RK is a surgical procedure designed to correct nearsightedness (myopia). It is a relatively new procedure and was developed as an alternative to other methods of correcting myopia such as glasses or contact lenses. In this procedure, a small knife-like instrument (called a keratome) is used to cut the cornea (the clear covering of the eye). The amount that the cornea is cut is equal to the amount that the eye needs to be corrected for near vision.
Sources & references used in this article:
Transient monocular blindness associated with hemiplegia by M Fisher – AMA archives of ophthalmology, 1952 – jamanetwork.com
The Temporary Use of Red Glass before the Fixing Eye in Squint Cases by OL McCulloch – Optometry and Vision Science, 1930 – journals.lww.com
Artificial vision for the blind by connecting a television camera to the visual cortex by WH Dobelle – ASAIO journal, 2000 – journals.lww.com
Factors affecting visually evoked cortical potentials such as impaired vision of varying etiology by RM Copenhaver, NW Perry – Investigative Ophthalmology & …, 1964 – iovs.arvojournals.org
Uncanny sight in the blind by B De Gelder – Scientific American, 2010 – JSTOR
Prevalence of blindness and cataract surgery in Nepal by GP Pokharel, G Regmi, SK Shrestha… – British Journal of …, 1998 – bjo.bmj.com
The period of susceptibility to the physiological effects of unilateral eye closure in kittens by DH Hubel, TN Wiesel – The Journal of physiology, 1970 – Wiley Online Library
Long-term follow-up of laser iridotomy by HA Quigley – Ophthalmology, 1981 – Elsevier
