macular hole

A cupcake rendition of an OCT showing a macular hole

What is a macular hole?
To describe a macular hole and how it forms, we need to first discuss the anatomy of the eye. Check out this video for a concise overview of the structures of the eye (it's less than a minute long).

The anatomy of the eye

Image: ASRS

The inside of the eye is basically a gel sack. That gel sack is called the vitreous, and it is attached to the retina (the tissue that lines the back of the eye). The vitreous attaches strongly at a few key points, one of which is the macula (the part of the retina responsible for your central, sharpest vision). As we age, the vitreous changes and becomes more liquid. When it becomes more liquid, it shrinks away from the retina and detaches from it [more on that in a previous post]. The vitreous may pull on the retina as it is detaching, and it can take some of the retina with it. That results in a retinal tear or hole. If the hole occurs in the macula, it's a macular hole.

Other than the vitreous traction described above, there are some additional causes of macular holes including trauma, high amounts of nearsightedness, diabetic eye disease, and epiretinal membranes (aka macular pucker).

Since they are most often related to aging processes, macular holes are more common in people over 60 years of age. They are also more common in females than males (1).

A visual of the vitreous detaching from the retina (posterior vitreous detachment, or PVD)
Image: Eye

What are the symptoms of a macular hole?
The macula is the part of the retina that is responsible for your central, sharpest vision. So a macular hole can cause blurred or distorted central vision. You may also notice a dark spot in your central vision.


How is a macular hole diagnosed?
A macular hole is found by your optometrist or ophthalmologist during a dilated eye exam. Fundus photography, as seen below, can be used to document the appearance of the hole, using filters to make the hole more apparent.

Fundus photo of a patient with a macular hole

Optical coherence tomography (OCT) is very helpful in diagnosing and monitoring resolution of macular holes. A macula OCT is a noninvasive imaging test that produces a cross-sectional view of the macula (see below). This allows your eye doctor to see what stage the hole is, how large it is, and if there is traction on the macula.

OCT scan of the above photographed macular hole

How do you treat macular holes?
Though some small macular holes are left to resolve and seal on their own, many require treatment. The most common way to treat a macular hole is with a procedure called a vitrectomy. That's when a retinal surgeon removes the gel sack in the eye and replaces it with a gas/air bubble. Removing the vitreous relieves the pulling (traction) on the retina, and the bubble puts pressure on the edges of the hole, helping to bridge and seal the hole. In some cases, the inner limiting membrane of the retina is also peeled (jury is still out on whether this is required to achieve the best results in small holes). Most surgeons will advise patients to maintain a face-down position for a few days after surgery, sometimes even as long as 2 weeks (jury is still out on whether this is necessary for small and medium holes). The success rate for this procedure is very high, with estimates ranging between 85 and 100% (2). Cataracts are common following vitrectomy, so some surgeons may opt to remove the lens at the same time as doing the vitrectomy.

Another potential treatment in cases of small or medium holes with traction is injection of ocriplasmin (Jetrea®) into the eye. This drug degrades the adhesion molecules (specifically fibronectin and laminin) at the interface of the vitreous and retina, helping to relieve traction on the retina. With a success rate of 35-40%, ocriplasmin is significantly less successful in achieving closure of macular holes when compared to vitrectomy, especially for medium sized holes (3). It is also less cost-effective in many health systems.

If you've had a macular hole in one eye, you have an increased risk of getting one in the other eye. Estimates vary, but you are looking at a 5-15% chance over 5 years (4, 5). So keep seeing your optometrist for routine eye exams!


CliffsNotes: A macular hole is a hole in the part of the retina called the macula, and it most often occurs as a result of aging processes within the eye. Most cases are treated with a surgical procedure called vitrectomy. 


Additional recommended resources:

• NEI: Facts About Macular Holes
• All About Vision: Macular Holes

eye floaters

Ever wonder what those squiggly things are that float around in your field of vision?  They may look like bugs, strands, or cobwebs, and they are especially noticeable when you're looking at a plain, bright background (like a clear sky). When you move your eye to get a closer look, those sly boogers drift away! Wonder no more: they are vitreous floaters.

Let's do a quick anatomy review before we continue: The vitreous (sometimes called vitreous humor or vitreous body) is the transparent, gel-like substance that fills the area between the lens and the light-sensitive tissue that lines the back of the eye (retina).  The vitreous accounts for about 80% of the eye's volume.  It is made up of water (~99% of its volume is water) and a network of proteins (collagen fibrils) and sugars (hyaluronan).  As we age, the vitreous becomes less gel-like and more liquid.  The vitreous is attached to the retina at a few key points.

From Mayo Clinic

What is a floater?
What we see as floaters are actually the shadows cast on the retina by substances in the vitreous.  Those substances can be clumps of protein, blood cells, or pieces of tissue.  Check out this great video for an illustration.

Below are a couple of Optomap images that show floaters (both photos are from the same patient- we decided she just has very photogenic floaters).  Depth doesn't translate well in these photos, so here's an explanation of what we are looking at: if you cut the eyeball in half, the red tissue you see in the photos is the inside lining of the back of the eye (retina), and the strands/blobs that the arrows are pointing to are the floaters in the vitreous, which is in front of the retina.

What causes floaters?
Sometimes, floaters are no big deal.  The floaters that we see from time to time are usually just that; they're clumps of fibers that cast shadows on the retina.  Other times, floaters are a symptom of an eye condition.

• Posterior vitreous detachment (PVD): A PVD can occur as a result of trauma, though it's most often a result of age-related changes in the vitreous. As the vitreous shrinks and becomes more liquid, it may collapse and pull away from the retina.  The point where the vitreous was attached to the optic nerve is what most people complain of- a large floater that appears somewhat suddenly.  A PVD typically occurs earlier in people who are near-sighted and those who have had cataract surgery or eye trauma (1).  Another symptom that may be experienced during a PVD is flashes of light. The mechanical pulling of the vitreous on the retina as it detaches can cause stimulation of the retinal photoreceptors, resulting in the perception of flashes of light.  The concern with a PVD is that the pulling of the vitreous from the retina may result in a retinal break. Between 8% and 26% of acute, symptomatic PVDs are associated with a retinal tear upon initial examination.  Even if no break is found upon initial examination, there is still a 2-5% chance of a retinal break being found a few weeks later (2, 3, 4). Take home point: it's impossible to know if there is cause for concern based on symptoms alone; a thorough examination is necessary. 
• Retinal break: A retinal break can occur as a result of a PVD or trauma.  Most retinal breaks are treated, as a break can allow fluid under the retina and cause a retinal detachment, which results in permanent vision loss if untreated. 
• Vitreous hemorrhage: The vitreous contains no blood vessels, so blood in the vitreous comes from the leakage of vessels into/near the vitreous. This finding is usually associated with trauma, a PVD (with or without retinal tear, but more often with), or vascular disease. The source of the blood can be breakage of a normal retinal blood vessel, as a result of a tear or trauma, or it can be breakage of an abnormal blood vessel (neovascular membrane).  For example, I had a young patient with insulin-dependent diabetes come in complaining of a cobweb in her vision.  The cause of her symptoms was a large hemorrhage in the vitreous stemming from diabetic retinopathy. She had a neovascular membrane form in the back of the eye; these vessels are inherently fragile and bleed easily.   
• Vitritis: A vitritis is an inflammation of the vitreous body.  The inflammatory cells in the vitreous can cause floater-like symptoms. Blurred vision is also a common accompanying symptom. A vitritis can occur as a result of an infection, autoimmune disorder, or trauma, or it can be idiopathic (no known cause). This entity requires treatment.

I have floaters! What should I do?
As mentioned earlier, a few floaters every now and then is not unusual.  However, you should see your eye doctor right away if you experience:

• sudden floaters and/or flashes of light
• an increase in the frequency and/or number of your floaters 
• a loss of peripheral vision

How are floaters treated?
Really, they're not.  The underlying cause of the floaters may need treatment, as in the case of a retinal tear, a vitreous hemorrhage, and a vitritis.  PVDs, in the absence of a retinal tear, are just monitored.  Floaters often become less noticeable as they break apart and settle towards the bottom of the eye, and as the brain learns to ignore them. Rarely, there are instances where laser treatment or vitrectomy (a surgery where the vitreous is removed) may be pursued to remove large, very symptomatic floaters. However, risks-vs-benefits must be carefully considered, as floaters are harmless and there are risks associated with any surgical procedures.


CliffsNotes: Occasional floaters are normal and increase with age.  However, if you have sudden floaters and/or flashes of light, a loss of peripheral vision, or an increase in the frequency and/or number of your floaters, it's a good idea to go see your optometrist ASAP.


Additional recommended resources:

• All About Vision: Floaters
• NEI: Floaters
• Mayo Clinic: Eye Floaters