Category: Retina

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Retina Testing

Fluorescein Angiography

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There are several diagnostic tests used by a retina specialist which provide us with unique information about the health of the retina.  A fluorescein angiogram has long been the gold standard of the retina specialist to study;

  1. Patients with diabetic retinopathy
  2. Macular degeneration
  3. Abnormal swelling of the retina
  4. Retinal Vascular Occlusions

The study principally allows the retina specialist to study abnormalities in blood supply and blood flow of the retina.

The Fluorescein Angiogram

To perform the test, a small amount of fluorescein dye is usually injected into an arm vein.  The same vein used when drawing blood, located in the antecubital fossa of your forearm, is usually sufficient.

The dye then travels to the retina in 12-20 seconds.  A series of photographs are now taken as the dye circulates through the retina.

Thanks to digital photography, the results are reviewed instantaneously by your retina specialist.  Before digital photography, camera film needed to be processed before the results could be reviewed adding hours or days to the process.

Reactions to Fluorescein

As with any compound, certain patients can have a reaction to fluorescein.  Symptoms can range to itching, hives, nausea/vomiting or worse, severe anaphylaxis.

Death from anaphylaxis due to fluorescein is very unlikely and estimated to be about 1 chance in 220,000.

Fluorescein angiography is performed in the presence of a medical doctor.

Because fluorescein is unique to ophthalmology and is a plant based vegetable dye, there is no chemical similarity to the contrast dyes used in radiologic xrays and MRIs.

Results of the Fluorescein Angiogram

This test is very helpful in confirming the diagnosis of many disease or elucidating the cause of subtle changes in vision.

In cases of macular degeneration, an “FA” can:

  1. Confirm the diagnosis of ARMD
  2. Determine any evidence of the wet form of macular degeneration
  3. Provide evidence of progressive changes (when compared to previous studies)

In cases of diabetic retinopathy, a fluorescein angiography can be useful for:

  1. Demonstrating otherwise undetectable evidence of early disease
  2. Provide proof of macular edema, a common complication of diabetic retinopathy
  3. Demonstrate evidence of neovascularization of the retina, a potentially blinding complication

Overall, the fluorescein angiogram is regarded as a very safe and effective diagnostic tool for the retina specialist.  Other diagnostic testing for retinal diseases includes the OCT, or optical coherence tomography.

 

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Retina Retinal Vascular Occlusions (RVO) Uncategorized

Retinal Vascular Occlusions | RVO

Retinal Vascular Occlusions | BRVO, CRVO, CRAO, BRAO

Retinal Vascular Occlusions

Both arteries and veins of the retina can become blocked or occluded.  Each type has characteristic complications though they all can cause vision loss.  

There are four types of retinal vascular occlusions, also known as RVO, including:

  1. Branch Retinal Vein Occlusion (BRVO)
  2. Central Retinal Vein Occlusion (CRVO)
  3. Branch Retinal Artery Occlusion (BRAO)
  4. Central Retinal Artery Occlusion (CRAO)

All types of retinal vascular occlusions cause sudden and painless loss of vision.  Usually only one eye is affected over the lifetime of a patient. Vision can vary depending upon the exact RVO, but can range from asymptomatic to profound legal blindness.   Treatments exist, but results differ.

There are occlusions affecting veins and disorders affecting arteries of the retina.

Vein Occlusions

Central and branch retinal vein occlusions differ only by the amount of retina which is diseases.  CRVO involve the entire retina. BRVO affects 50% or less of the retina.

Occlusions of the venous system are usually thought to be due to local hardening of the blood vessels and NOT usually associated systemic cardiovascular disease (i.e. heart attack, stroke).  Diabetes and high blood pressure can increase the chance of a vein occlusion occurring, but they do NOT directly cause the veins to plug.

Artery Occlusions

The difference between the central and branch artery occlusion is the same as their venous cousins.  Central affects the entire retina. Branch artery occlusions affect less than 50% of the retina.

Artery occlusions occur when a piece of blood clot, cholesterol, fat or platelets physically block or plug the artery.  These are different types of “emboli” which can occlude the artery. Most “emboli” are cholesterol plaque from the carotid artery.  A tiny piece of cholesterol breaks off into the blood stream, travels to the retina and plugs a blood vessel.

Vision loss from a CRAO is usually profound and permanent.  Smaller branch artery occlusions are associated with blind spots, some elements of the vision may be normal – all depending upon the amount of retina involved.  

Both heart attacks and strokes occur by similar mechanisms.  The presence of a CRAO or BRAO may lead to further assessment of the patient’s chances of developing stroke or heart attack.

 

Though vision loss from artery occlusions tends to be permanent, follow up is necessary to look for signs of neovascularization which can lead to a very painful type of glaucoma.  

 

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Categories
Retina Retinal Vascular Occlusions (RVO)

Branch Retinal Vein Occlusion | BRVO

Central Retinal Vein Occlusions | Randall Wong MD Retina Specialist

BRVO

Central Retinal Vein Occlusions | Randall Wong MD Retina SpecialistThink of a branch retinal vein occlusion (BRVO) as a partial central retinal vein occlusion (CRVO).  Where a CRVO involves the entire retina, a BRVO involves 50% of the retina or less.  Hemi-retinal vein occlusion is synonymous with BRVO.

There are four types of retinal vascular occlusions (RVO) that can occur.  They differ by affecting either veins or arteries and then by the percentage of the retina involved.  The four types are:

  1. Branch retinal vein occlusion (BRVO)
  2. Central retinal vein occlusion (CRVO)
  3. Branch retinal artery occlusion (BRAO)
  4. Central retinal artery occlusion (CRAO)

In a BRVO, part of the retinal vein occludes (gets plugged) and blood flow ceases.  Blood and fluid leak into the surrounding retina. If the macula is involved, significant decrease in vision results.  If the macula is not involved, patients are sometimes asymptomatic.

Symptoms of BRVO

The symptoms of all retinal vascular occlusions are similar:  painless and sudden loss of vision. If swelling of the macula develops, called macular edema, central vision is lost.  If there is no macular edema, central vision is preserved and vision loss seems less severe.

By definition, branch retinal vein occlusions involve 50% or less of the retina and vision is usually not as dramatically decreased compared to a CRVO.

Treatment and Prognosis

Of all the retinal vascular occlusions, branch retinal vein occlusions usually have a good prognosis. Vision can often be improved by reducing the resulting macular edema.

Until intraocular injections gained a foothold, laser treatment was the gold standard,  Laser treatment often could reduce the macular edema resulting in some moderate improvement.

anti-VEGF injections, such as Eylea, Lucentis and Avastin chemically reduce macular edema and the results can be fantastic.  

Steroids are also very effective and include Kenalog, Triesence (preservative free Kenalog) and Ozurdex.  Ozurdex is a sustained release steroid implant lasting up to 6 months. There is a second sustained release device available called Iluvien.  

All anti-VEGF and steroids are given by injection into the eye.  

Treatments are often repeated.  

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“Other” Eye Conditions Retina Social Media and Health

How to Watch the Eclipse Safely | Avoid Blindness

Protect Your Eyes and Vision from Solar Eclipse | Randall Wong MD Retina Specialist

Are your prepared to watch the eclipse safely?

WARNING:  It’s never safe to stare directly at the sun or at an eclipse.

Here’s how you can safely view the upcoming eclipse without causing eye damage or blindness.

The Great American Eclipse 2017

A total eclipse of the sun will occur on August 21, 2017 in North America.  This may be a “once in a lifetime” opportunity to experience the “path of totality” – when the moon completely blocks the sun for about 3 minutes.

The “path of totality” is about 70 miles wide and will sweep eastward from Oregon to South Carolina.  For those viewing within this path, they will experience a total eclipse of the sun.  The sky will become a dark twilight.

The rest of the country will experience a partial eclipse – differing amounts of sunlight loss.

Next Total Solar Eclipse

Incidentally, the last total eclipse of the sun occurred on March, 2016 and could be experienced in Indonesia.  The next total eclipse of the sun will occur in South America, 2019.

For most of us, the Great American Eclipse 2017 will be the only practical opportunity to experience this unique astronomical event.

Solar Retinopathy Can Blind

Staring directly at the sun, including an eclipse, can blind you.  The light rays of the sun are strong enough to burn your macula.  The macula is the most sensitive portion of your retina.

Sun damage can permanently destroy your central vision.  This condition is called solar retinopathy.  There is no cure for solar retinopathy.

Never look or photograph the sun without use of special lenses which have been designed specifically for the sun.

Eclipse Glasses Safely Protect Retina

There is only one safe way to view the sun or eclipse.  The American Academy of Ophthalmology and the American Astronomical Society recommend the use of special lens filters, ISO 12312-2, which have been designed for sun viewing.

If your “eclipse glasses” or solar viewers are compliant with the ISO 12312-2 safety standard, you may view the sun or eclipse safely.

These filters are strong enough to block the harmful rays of the sun and are thousands of times stronger than the darkest sunglasses.

The filters are used in “eclipse glasses” and other solar viewers.  I have included a link to known telescope and solar-filter companies that manufacture eclipse glasses and handheld solar viewers.

It may be fun to construct a pinhole camera to indirectly, and safely, view the upcoming eclipse.  A pinhole camera uses simple materials found around the house and can be a fun and inexpensive way to enjoy the total eclipse of the sun.

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