itchy allergy eyes

Photo by Jeremy Gilchrist, capturing the yellowish-green cloud of pine pollen in Durham, NC

Spring has sprung here in North Carolina, and, as you can see in the photo, we're in the thick of Pollenpocalypse. This is around the time of year that I start to see a large influx of patients with red, watery, itchy eyes. The tree and grass pollen that come with spring can often cause allergies to flare, and the eyes are a common site for such allergic reactions.


What is allergic conjunctivitis?
Allergic conjunctivitis is inflammation (-itis) of the eye (specifically, the conjunctiva) caused by an allergic reaction. Probably didn't need me to figure that one out, right? The sequence of events that occur, in a nutshell (1):

1. The surface of the eye is exposed to an allergen (pollen, animal dander, ragweed, etc).
2. The immune system responds by producing immunoglobulin E (IgE), which binds to mast cells. Mast cells are found on the conjunctiva, which is the transparent tissue covering the white part of the eye as well as the inner eyelids.
3. This causes the mast cell to degranulate and release chemical mediators, one of which is histamine.
4. Histamine binds to receptors on cells in the conjunctiva, which causes itching, redness, tearing, and swelling.
5. Allergy eyedrops work by stabilizing the mast cells and/or binding to the histamine receptors (thus blocking histamine from binding), which interrupts the cycle and reduces the allergic response. 

Are there different forms of allergic conjunctivitis?
Yes, though it may be more of a spectrum of inflammation rather than distinct entities. The most common forms of allergic conjunctivitis (seasonal or perennial allergic conjunctivitis) are type 1 hypersensitivity reactions, and generally only exhibit what's referred to as the early phase response. This involves the acute symptoms of itching, redness, tearing, swelling, etc. The more chronic types of inflammation (vernal or atopic keratoconjunctivitis) are thought to have both type 1 and type IV hypersensitivity reactions, exhibiting the late phase response that often comes with tissue damage (2).


What should I use to get rid of my allergic conjunctivitis?
First, I would discourage the use of any "redness relief" drops; more on why in this previous blog post. You want to treat the cause, not just mask a symptom.

My go-to over-the-counter recommendation would be ketotifen fumerate (available generic and branded as Alaway, Zaditor, etc). Ketotifen is an H1-receptor antagonist (aka antihistamine) and a mast cell stabilizer, meaning it prevents the release of histamine and other mediators from mast cells. Translation: less itching and redness and swelling! This drug is dosed 1 drop in each eye twice a day as needed. You should instill the drop without contact lenses, and wait about 10 minutes before putting the contacts in. Ketotifen is approved for children age 3 and up.

It's not a bad idea to keep allergy eyedrops in the refrigerator; the cooling effect upon use can help sooth the inflamed ocular surface.

This may be all you need in mild cases of acute allergic conjunctivitis. But if your symptoms continue or worsen, make an appointment to see your eye doctor ASAP! There are numerous prescription options to pursue, from anti-histamines to steroids, depending on the level of inflammation present. There are a handful of prescription medications that are approved for children as young as 2, as well as options for convenient once-a-day dosing.

There's also the chance that what you suspect are allergies could be something else, or a combination of multiple things (dry eye, uveitis, infection, contact lens complications- the list goes on). For instance, oral antihistamines frequently taken for allergies can dry the eye, which can cause further inflammation of the ocular surface. Our tears are helpful for flushing away allergens, so dry eyes can make allergic conjunctivitis symptoms worse. It's a bit of a catch 22, but your eye doctor can devise an effective treatment strategy. Something as simple as switching to daily disposable contact lenses can help alleviate your symptoms considerably. When in doubt, see an optometrist!


--> CliffsNotes: If your eyes are itchy, watery, and red, you may have allergic conjunctivitis. There are effective over-the-counter options (like Alaway or Zaditor) as well as many prescription options. See your optometrist to make sure what you're experiencing is in fact allergic conjunctivitis, and discuss what treatment option is best for you.

get the red out

How do "redness relief" eye drops work?

Short answer: "Redness relief" drops contain an ingredient that causes the superficial blood vessels of the eye to constrict, or narrow. 

Long answer: Brace yourself- it's about to get real nerdy up in here. Our blood vessel walls are made up of smooth muscle tissue. There are receptors in that smooth muscle tissue called alpha-adrenergic receptors. These receptors are activated by alpha-adrenergic agonists, which are agents that essentially stimulate the sympathetic (ie: fight or flight) response in the blood vessels. So when an alpha-adrenergic agonist binds to these receptors, it causes the muscle to contract, which constricts the blood vessels. 

Vascular smooth muscle has two types of alpha-adrenergic receptors: alpha 1 and alpha 2. The active ingredients in many of the redness relief drops on the market work by affecting only alpha 1 receptors, or both alpha 1 and alpha 2 receptors. File that away in your mind; we'll return to that shortly. Some common examples of drugs that behave this way: phenylephrine and tetrahydrozoline (alpha 1 only), and naphazoline and oxymetazoline (alpha 1 and alpha 2) (1). These are the ingredients commonly found in over-the-counter "redness relief" eye drops.

What is the active "redness-relieving" ingredient in some common eyedrops?

• Naphcon-A (Alcon): Naphazoline hydrochloride 0.025%
• Visine
• Visine Original Redness Relief: Tetrahydrozoline hydrochloride 0.05%
• Visine Advanced Redness and Irritation Relief: Tetrahydrozoline hydrochloride 0.05%
• Visine Maximum Strength Redness Relief: Tetrahydrozoline hydrochloride 0.05%
• Visine Totality: Tetrahydrozoline hydrochloride 0.05%
• Visine AC Ultra Itchy Eye Relief: Tetrahydrozoline hydrochloride 0.05%
• Visine A Multi-Action Eye Allergy Relief: Naphazoline hydrochloride 0.025%
• Rohto
• Rohto Digi Eye: Tetrahydrozoline hydrochloride 0.05%
• Rohto Ice: Tetrahydrozoline hydrochloride 0.05%
• Rohto Cool: Naphazoline hydrochloride 0.012% 
• Rohto Cool Max: Naphazoline hydrochloride 0.03%
• Clear Eyes
• Clear Eyes Redness Relief: Naphazoline hydrochloride 0.012%
• Clear Eyes Maximum Itchy Eye Relief: Naphazoline hydrochloride 0.012% 
• Clear Eyes Cooling Comfort Itchy Eye: Naphazoline hydrochloride 0.012%
• Clear Eyes Complete 7 Symptom Relief: Naphazoline hydrochloride 0.025%
• Clear Eyes Maximum Redness Relief: Naphazoline hydrochloride 0.03% 
• Clear Eyes Cooling Comfort Redness Relief: Naphazoline hydrochloride 0.03%
• Clear Eyes Triple Action: Tetrahydrozoline hydrochloride 0.05%
• Clear Eyes Traveler's Eye Relief: Tetrahydrozoline hydrochloride 0.05% 
• Clear Eyes Pure Relief Multi-Symptom: Phenylephrine hydrochloride 0.10%
• Bausch and Lomb
• Opcon-A: Naphazoline hydrochloride 0.02675%
• B&L Advanced Eye Relief Redness Reliever: Naphazoline hydrochloride 0.012%
• B&L Advanced Eye Relief Maximum Redness Reliever: Naphazoline hydrochloride 0.03%
• Lumify Redness Reliever: Brimonidine tartrate 0.025%

I personally do not recommend the majority of these redness relief drops. Why not?

Drops that affect alpha 1 receptors can lead to rebound hyperemia (translation: eyes become more red when you stop using the drop), and tachyphylaxis (translation: loss of effectiveness over time). 

Arteries carry oxygenated blood away from the heart to the body's tissues. Since alpha 1 receptors are predominantly in arteries, the drugs that act on these receptors cause constriction of the arteries, which decreases blood flow and thus oxygen flow to the tissue. Over time, the body adjusts to this lack of oxygen by down-regulating, or producing less of, the alpha 1 receptors. So this lessens the body's response to the drop (tachyphylaxis). With loss of effectiveness comes more frequent use, and more frequent use can possibly lead to toxicity from the preservatives in the drop (2). Overusing these drops can even cause your pupils to dilate!

When the drop is discontinued after a long period of use, the body's attempt to deliver more oxygen to the oxygen-deprived eye tissue is to dilate the blood vessels, which makes the eyes appear redder (rebound hyperemia). This can then cause a person to return to using the eye drop, and the vicious cycle goes on. 

What is Lumify?

Lumify is an over-the-counter eye drop that has been FDA approved for the relief of ocular redness due to minor eye irritations. It is approved for age 5 and older, begins working within 1 minute of instillation, and provides up to 8 hours of redness relief. 

The active ingredient in Lumify is brimonidine tartrate (0.025%). Brimonidine tartrate (in higher concentrations) has long been used as a medication to lower eye pressure. It is also used in ocular surgery to control bleeding. In gel form, it is used to treat facial redness due to rosacae in adults. 

How is Lumify different than all of the other redness relief drops out there?

Brimonidine tartrate is a selective alpha-2 adrenergic receptor agonist. Recall that all of the other drops mentioned above work on either alpha 1 only or both alpha 1 and alpha 2. Because of Lumify's selectivity, its effect is primarily on the veins and not the arteries. Thus, Lumify does not have as significant of an effect on oxygen flow, which reduces the oxygen-deprivation that triggers those negative side effects. In Phase 3 clinical trials, Lumify showed no evidence of tachyphylaxis and minimal rebound hyperemia (3). 

But WHY are your eyes red?

There are numerous conditions/factors that can make eyes red: dryness, allergies, contact lens overwear, uveitis, infection, foreign body, exposure to smoke or other irritants, fatigue, etc. Don't just buy a drop to mask the symptom; see an optometrist to determine and address the source.



--> CliffsNotes: Redness relief drops can have unwanted side effects, so I don't recommend frequent use of drops like Visine, Clear Eyes, Rohto, etc. Lumify's unique mechanism of action avoids these unwanted side effects. If your eyes are red, it's best to start by seeing your optometrist to figure out why they're red.

*Dr. H has no financial interests in any of the products mentioned*

eye makeup safety tips

As an optometrist, I get up close and personal with a lot of eyes. I see a fair amount of complications related to not-so-great eye makeup habits, so I wanted to share my top 10 eye makeup tips (from an eye health standpoint). 

1. Don't apply makeup inside the lash line.

This tops my list of eye makeup no-nos. "Waterlining" is the practice of applying eyeliner directly on the waterline. The waterline is the thin area between the eyelash line and the eye. Within that area are the openings of your meibomian glands. Meibomian glands secrete oil onto the front surface of the eye to help keep your tear film stable and your eyes moist and comfortable. Applying makeup inside the lash line can block these important glands, which can cause meibomian gland dysfunction (MGD). If the oil is not being secreted onto your tear film properly, your tears evaporate more quickly and your eyes are more dry. Dryness can manifest as a burning sensation, a sandy/gritty feeling, redness, tearing, and discomfort. Meibomian glands can also get infected (this infection is called a hordeolum, commonly referred to as a stye), so keep makeup away from the waterline!

Image via All About Vision

Makeup applied inside the lashline is also more likely to migrate into the eye and contaminate the tear film when compared to application outside the lash line (1). This presence in the tear film can cause irritation (especially for contact lens wearers) and tear film instability, which is a factor in dry eye disease.

Avoid applying eyeliner on the waterline, as demonstrated on the left
Image via Beauty Insiders

Beyond affecting your tear film stability and potentially causing infection, applying makeup inside the lash line can cause the makeup to build up in the eye over time and cause irritation. Below is an example of this. One of my patients came in reporting red and irritated eyes for several weeks. After examining her eyes, it appeared that she was applying a nude eyeliner to the water line, and that same nude eyeliner was found deposited in her lower eyelid tissue (the palpebral conjunctiva). When we discussed the findings, she realized that her symptoms began shortly after she adopted a new makeup technique she found on a YouTube tutorial. 

The arrow is pointing to some of the nude eyeliner particles that have become
embedded in the conjunctival tissue of the lower lid

Something else you shouldn't put on your waterline? Bling. That's right. Apparently, it needs to be said.

Don't do this. Just don't.
Image via Allure

2. Replace mascara and eyeliner every 3 months.

Liquid and cream makeup can be a breeding ground for bacteria. Get in the habit of cleaning out your makeup bag every quarter and replacing your mascara, eyeliner, etc. If you develop an eye infection, throw out your old makeup and start fresh. 

3. Don't sleep in your makeup.

You know this. But it happens. This is a report on a 50 year old woman who admitted to heavy mascara use with inadequate removal for 25+ years. The below photo shows mascara particles embedded in the tissue that lines the upper eyelid. Thoroughly clean your lids and lashes every night! After removing makeup, gently scrub along the lid margin with a premoistened wipe or a q-tip dabbed with a lash/lid cleanser. I recommend using a product that contains diluted tea tree oil, but avoid getting it IN the eye. Tea tree oil is effective against eradicating a mite that lives amongst your lashes (more on that in a previous post). Some of the products I frequently recommend to patients: Blephadex, Cliradex, We Love Eyes. *I have no financial interests in any of these companies- just sharing my recommendations!*

Mascara particles embedded in the conjunctival tissue
Image via Ophthalmology

4. Don't apply mascara in a moving vehicle, or use a sharp object to separate your lashes.

This may seem obvious, but it needs to be said. Mascara wands are a common cause of corneal scratches or abrasions. Keep sharp things away from your eyes!

Corneal abrasion from a mascara wand
Image via Clinical Optometry

5. Avoid using makeup that flakes. 

Glittery eyeliner is an example- the glitter particles can enter your eye and swim around in your tearfilm, irritating the eyes and adhering to contact lenses. 

Fiber mascara is another no-no in my book. The fiber particles often flake off and enter the eye, causing irritation and inflammation. 

This image shows glittery makeup particles within the tear film

6. Stop using a product if your skin/eyes become irritated, red, and swollen. 

It could be an allergic reaction to a new product. It's a good idea to patch test new makeup on your hand or arm before using it on/around your eyes. 

If you experience symptoms of redness, irritation, pain, itching, and/or dryness, discontinue makeup use and see your optometrist. This also applies to eyelash enhancers; there are many out there that cause inflammation and irritation of the eyelid margins. 

7. If you wear contact lenses, opt for daily disposable contacts. 

If there are any makeup particles adhering to your contact lenses, daily disposable contacts allow you to just throw them away at the end of the day. So you're not worrying about makeup deposits accumulating on your lenses day after day. 

8. Keep makeup brushes clean.

Bacteria and dust collect over time, so keep your makeup applicators clean.

9. Avoid eyelash extensions.

Blasphemy, I know. But just hear me out, and do with it what you will. 

Many of the complications I see relating to eyelash extensions stem from neglecting to clean the lash line well. With how expensive eyelash extensions are, I can understand being super cautious about bringing anything near them! Bacteria and dirt can collect and get trapped around the base of the lashes, causing irritation and infection. If you have eyelash extensions, avoid wearing mascara and oil-based makeup on or around the extensions. Use an oil-free cleanser on your lash line daily, gently cleaning the lash line using a bristle brush or spoolie (cotton can snag, so avoid that). Oil-based makeup removers weaken the adhesive and can cause the extensions to fall out prematurely, so use oil-free cleansers (thus, the tea tree oil cleansers I recommended earlier would not be a good option for those with extensions). 

The glue used to adhere eyelash extensions may contain formaldehyde, which can cause an allergic reaction. Ask your aesthetician what ingredients are in the glue he/she uses.

Dislodged or loose extensions, or flakes of glue, can rub against the eyelid and/or the cornea, which causes extreme irritation. If that happens, see an optometrist to remove the offending lash/particle. 

Eyelash extensions can also damage your natural eyelashes and even damage the hair follicle, which can slow down or halt hair growth. 

The best way to avoid these complications is obviously to avoid eyelash extensions. However, if you choose to go that route, here are some tips:

• Make sure you look into the certifications and experience of your aesthetician
• Choose a reputable salon that is safe and hygienic
• Ask about adhesive ingredients beforehand
• Avoid wearing mascara and oil-based makeup with eyelash extensions
• Clean lashes daily with an oil-free cleanser
• See an eye doctor if you develop redness, irritation, etc. 

10. Don't borrow or share makeup.

Sharing makeup introduces more bacteria and increases the likelihood of infection. Sampling makeup at a beauty counter is not a great idea, especially if multiple people sample the same bottle of product. 

CliffsNotes: 1) Don't apply makeup to the waterline, 2) Replace mascara and eyeliner every 3 months, 3) Don't sleep in your makeup, 4) Don't apply mascara in a moving vehicle or use sharp objects to separate lashes, 5) Avoid using makeup that flakes, 6) Stop using a product if your skin/eyes become irritated, red, and swollen, 7) If you wear contact lenses, opt for daily disposable contacts, 8) Keep makeup brushes clean, 9) Avoid eyelash extensions (if you must use them, be safe and keep them clean!), and 10) Don't borrow or share makeup.

Additional Recommended Resources:

• American Optometric Association: Cosmetics and the Eye

blue light

According to the Vision Council, over 80 percent of Americans report using digital devices for more than two hours per day, and more than 70 percent of American adults report their children receive more than two hours of screen time per day (1). With the increasing prevalence of LED-backlit digital devices and the increasing time spent on such devices (especially among children), we are exposed to more blue light today than ever before. Thus, we have an emerging interest in the long-term effects of blue light. Here's a rundown of what we know- and don't yet know- about blue light.

As wavelength (measured in nm) decreases, energy increases.
Blue light is on the high-energy end of the visible light spectrum. image source

What is blue light?
Blue light, often referred to as high energy visible (HEV) light, refers to light with wavelengths ranging from 380 to 500 nm (some may define it as wavelengths 400 to 500 nm). Unlike UV light, which is part of the non-visible spectrum, blue light is found at the high-energy end of the visible light spectrum.

Blue light can be divided into two bands: blue-violet light (roughly 415-455 nm) and blue-turquoise light (roughly 465-495 nm). Studies have shown that the segment of blue light that is most potentially harmful to the eye is at 415 nm to 455 nm (2, 3). Short story: blue turquoise is the good stuff, blue violet is the bad stuff. For the long story, continue reading!


Where does blue light come from?

• The sun. The majority of our HEV light exposure comes from the sun. Twenty-five to thirty percent of its spectral emissions fall within the HEV range.
• Artificial light sources. We are seeing a shift from incandescent light bulbs to LED (light-emitting diode) and CFL (compact fluorescent lamp) bulbs because they are more energy-efficient. But they also emit more blue light.
• Nearly 35% of cool LED emissions are in the HEV range, 25% of CFL emissions. Experts estimate that by the year 2020, 90% of all of our light sources will be LED (4, 5).

image source

• Digital devices with LED displays. This includes laptops, tablets, smart phones, some e-readers, etc.

Is blue light all bad?
No! Blue-turquoise light is vital for regulating our circadian rhythms, which in turn can effect mood, memory, hormonal balance and overall health (6).

In the eye, there are photosensitive retinal ganglion cells (pRGC) that have a peak sensitivity in the blue light range. When these cells detect blue light, they send signals to the suprachiasmatic nucleus (SCN) in the hypothalamus of the brain, as well as other brain centers. The SCN is considered the body's master clock and these blue-light sensitive cells help set the clock (6, 7).  When the pRGCs detect blue light, they are depolarized, which inhibits the release of melatonin, a hormone that plays a role in sleep regulation. Exposure to HEV before bed appears to reduce/delay the secretion of melatonin and thus affect our ability to fall asleep (8).

This disruption has effects that reach beyond just sleep; it has effects on mood, alertness, memory, and hormonal balance (6, 9, 10). Melatonin suppression and lack of adequate sleep has been associated with a greater risk of obesity, elevated blood pressure, diabetes, heart disease and stroke (11, 12). Exposure to high levels of blue light while sleeping may potentially be associated with an increased risk for certain hormone-related cancers (ie: breast, ovarian) (13, 14, 15).

Is blue light harmful to the eye?
We know that UV radiation causes harm to the eye, as it is absorbed by the structures in the front of the eye (the cornea and lens). HEV light is different because it mostly passes through the front part of eye, so its greatest threat to eye health lies primarily in the back of the eye (the retina). Blue light can potentially damage the light sensitive cells in the retina.

The lens is the transparent structure located behind the colored part of your eye. It absorbs more blue light with age, so young children are the ones at the greatest risk. As we age, the yellowing of the lens reduces the amount of blue light that is transmitted. The risk increases again after cataract surgery, when the natural, yellowed lens is removed and a clear implant is put in its place.

More blue light is absorbed by the lens with age, meaning less of it is transmitted to the retina.
image source

In vitro and animal studies have shown that visible light can cause damage to the layers of the back of the eye that include the photoreceptors (rods and cones) and the retinal pigment epithelium (RPE). When we discuss the dangers of blue light specifically, we're talking primarily about photochemical damage to the back of the eye (the retina). What does that mean exactly?

Light is a form of electromagnetic radiation, which is a form of energy. It is either absorbed or transmitted when it hits the eye. When light in the blue spectrum is absorbed, formation of excited molecules occurs. These excited molecules can induce chemical transformations within them, and they can also cause molecules around them to become chemically reactive as well. This leads to the development of toxic reactive oxygen species (ROS), which can cause oxidative damage to the outer retinal cells (2, 5). Studies have shown that accumulation of a retinal waste product called lipofuscin was found to make cells even more vulnerable to damage from blue light, leading to cell death (16). There's a lot we don't know about age-related macular degeneration (AMD), but oxidative damage is thought to have a significant influence on its development (17).

There is pigment in the part of the retina called the macula that absorbs blue light and also neutralizes ROS, which reduces the risk of damage. This macular pigment is made up of lutein, zeaxanthin, and meso-zeaxanthin. This pigment acts as a protective filter, and it is known to decrease with age. Studies have found low macular pigment levels to be associated with higher risk of age-related macular degeneration (AMD). We definitely need more studies to see if blue light exposure contributes to this pigment decrease (18). 


Can filtering blue light make it more comfortable when on digital devices?

Chromatic aberration is the defocused color fringe around text/images. It occurs when the eye is not able to bring all wavelengths of light into focus in the same place. Blue light scatters more, so it is less easily focused. This "visual noise" is believed to contribute to computer vision syndrome, or CVS. Filtering some blue light may enhance vision by decreasing glare and increasing contrast sensitivity, leading to increased visual comfort and improved visual performance (5, 7, 19).


So what does all this mean practically? 
To date, there is no long-term data on the effects of excessive exposure to HEV light on the eye. The studies done on blue light and retinal cell damage have been done in vitro or in animals models; more research is needed to see if long-term blue light exposure does indeed damage the human retina and lead to increased risk of macular degeneration. However, the potential connection between hazardous blue light and retinal damage suggests it is wise to try to limit our exposure over time. We know that the higher the energy, the more likely it is to result in oxidative stress and damage to biological tissue. Is there enough HEV light given off by digital devices to damage our health over time? How much is too much? We don't know. 

Some practical steps we can take to reduce our risk of experiencing the harmful effects of blue light:

1. Wear sunglasses. As we discussed, the majority of our blue light exposure comes from the sun.
2. Monitor screen time. This is especially important for young children, since their eyes allow more blue light transmission. Turn off digital devices a couple of hours before bed to avoid the harmful effects on melatonin secretion and circadian rhythms. The American Academy of Pediatrics offers some helpful tips for parents here.
3. Utilize blue light filters. There are settings on digital devices, filters to place on computer screens, and spectacle lens options to help filter harmful blue light. Discuss lens options with your/your child's eye doctor. We'll break down some lens options in a future blog post. 
4. Eat leafy green vegetables. Increasing your intake of the macular pigments we discussed (lutein and zeaxanthin) could potentially increase the level of these protective pigments in the retina. Check out my previous post on essential eye nutrients for more info.

CliffsNotes: Blue light is good and bad. We want to reduce our risk for cumulative harm over time by selectively filtering the portion that is potentially hazardous. There's a lot we don't yet know, but we should be prudent with what we do know. Practical tips: wear sunglasses, turn off digital devices 1-2 hours before bedtime, and talk to your eye doctor about possible dietary changes and blue light filtering lens options for your glasses (especially for young children). 


Additional Recommended Resources:

• All About Vision: Blue Light

epiretinal membrane

Epicupcake membrane

What is an epiretinal membrane?
An epiretinal membrane (ERM), also known as a macular pucker or cellophane maculopathy, is a thin layer of tissue that forms on the inner surface of the retina (the tissue that lines the back of the eye). **Look out, jargon ahead.** Specifically, an ERM forms when glial cells proliferate in a sheet between the internal limiting membrane (ILM) of the retina and the posterior hyaloid membrane of the vitreous. **You survived. No more jargon.** When ERMs contract, they pull on the retinal tissue and vessels beneath them. This causes wrinkling and distortion of the retina.

ERMs occur most often in those over 50 years of age, and their prevalence increases with age. ERMs effect males and females almost equally. Most are idiopathic (meaning unknown cause), but they can also occur secondary to posterior vitreous detachments (PVDs), eye surgery, diabetic retinopathy, eye inflammation, and trauma. ERMs can occur in both eyes in up to 20-35% of cases (1).


What are the symptoms?
Most ERMs have no symptoms and are found incidentally on routine eye exams. In those cases where symptoms are noticed, distorted vision (metamorphopsia) is the most common symptom. Decreased vision can occur as well, especially if the ERM is located at the macula (the part of the retina that is responsible for your central, sharpest vision).


How is it diagnosed?
ERMs are diagnosed by looking into the back of the eye during a dilated eye examination. An ERM appears as a shimmery reflectance over the retina, almost like fine gold glitter. If the ERM contracts, puckering or wrinkling of the retina and vessels beneath it may be noted. ERMs can be seen on retinal photos and OCT scans.

Infrared SLO of an ERM: you can see the wrinkling of the retina

Optical Coherence Tomography (OCT) is helpful for imaging and monitoring ERMs. An OCT scan provides a cross-sectional view of the retina, so you can easily see the membrane and how it is distorting the retina beneath it. Sometimes, OCTs can uncover ERMs before they are noticeable in the microscope.

OCT scan of an ERM: the white (hyper-reflective) line above the retina is the ERM

How is it treated?
In the majority of cases, ERMs are just monitored. However, ERMs can cause pseudo-holes and cysts in the retina. If vision is affected significantly, or if the ERM is threatening to cause significant vision loss, surgical intervention may be advised. If surgery is pursued, the gel part of the eye (the vitreous) is first removed in a procedure called a pars plana vitrectomy. Then, the ERM is peeled, and the internal limiting membrane (ILM) of the retina is sometimes peeled as well. Here is a neat video of the procedure (note: you will see that a dye is used to make the membrane more visible). In most cases, visual symptoms of distortion decrease after the membrane is peeled. Visual acuity may improve as well, but it often will not return to normal. ERMs may recur after removal.

Retinal photo of an ERM (note the gold shimmery appearance of the retina in the center of the image) with a pseudohole (the darker red circle in the middle of the gold shimmer)

CliffsNotes: An ERM is a sheet of cells that forms on the innermost layer of the retina. They are often symptomless and discovered on routine eye exam (so it's important to get those). Most of the time, ERMs are monitored but there are some occasions where they need to be peeled. 

Additional recommended resources:

• NEI: Macular pucker
• All About Vision: Vitreoretinal procedures
• ASRS: Epiretinal membranes

enchroma lenses and color vision deficiency

You may have seen the videos floating around the internet of colorblind people trying on EnChroma sunglasses for the first time. This month's blog post is about how it all works!

Ishihara cupcakes

How do we see color?
The retina (the tissue that lines the back of the eye) contains specialized cells called photoreceptors that respond to light. There are two types of photoreceptors: rods and cones.  Rods are responsible for vision in dim light, and cones are responsible for vision in bright light as well as color vision. There are three types of cones; each type is sensitive to different wavelengths of light, and thus different colors. "S" cones are most sensitive to short wavelengths (blues), "L" cones are most sensitive to long wavelengths (reds), and "M" cones are most sensitive to medium wavelengths (greens). The information gathered from these cones is used by the brain to create our perception of color.  Normal trichromatic color vision involves the presence and proper functioning of all three cones.  Color vision defects arise when one of these cones is missing or altered.

In English? Objects reflect light. That light acts as a wave as it enters the eye, activating the cones. The wavelength of that reflected light determines which cones are most activated. This cone response is translated to a neural signal and sent to the brain. Color perception is based on the relative levels of activity in the different cones.

A graph showing the spectral sensitivity of each of the 3 cones in someone with normal color vision
Image source: Eye, Brain, and Vision

What is a color vision deficiency?

The term "color blind" is misleading, as most people use the term to describe someone with a color vision deficiency. They can see colors, but have trouble distinguishing between certain colors and shades.  Color vision defects can be inherited or acquired. The most common are inherited, meaning they are present at birth, affect both eyes equally, and are stable over a person's lifetime. They occur in about 8% of males and 0.5% of females.  It is more common in males because the genes causing this type of color vision deficiency are located on the X chromosome. 

My previous post on color vision deficiency outlines all of the color vision disorders. For this post, we will only look into anomalous trichromats, meaning people who have all 3 cones, but the sensitivity spectrum of one is shifted. This shift causes a greater overlap in the sensitivities of two cones. There are various degrees of severity, based on on how much the spectrums are shifted.

The bottom 2 visuals show red-green color vision deficiency (CVD).
Protanomaly occurs when the L cone is shifted closer to the M cone, reducing sensitivity to reds. 
Deuteranomaly, the most common type of CVD, occurs when the M cone is shifted closer to the L cone, 
reducing sensitivity to greens.
Note the separation in the peaks of the L and M cone sensitivities is much smaller in red-green CVD compared to normal.

The ratio of light entering the eye tells the brain what color to perceive. The greater overlap of red and green in color deficient individuals skews the ratio. For example, when you see a red apple, the cones that should have the greatest response are the red, or long, cones. When there is excessive overlap between the red and green cones, more green cones are responding than normal, which essentially dilutes the red cone response and causes confusion and color muddling. So the apple may be perceived as more brown than red.


What are EnChroma lenses and how do they work?
EnChroma is a company that makes glasses designed to enhance the vibrancy and saturation of colors for those with color deficiencies. They are available in indoor and outdoor lenses, and can be made with or without a prescription.

The lenses actually began as protective eyewear for doctors to use during laser surgery, and their application for color vision deficiencies was discovered somewhat serendipitously. Check out the full story here.

As we noted in the graphs above, the overlapping responses to light by the red and green cones are the issue in those with red-green color vision deficiency. Rather than each cone responding separately, their responses are similar, causing colors to be muddled. EnChroma lenses are designed with "multi-notch filters" that cut out the wavelengths of light that cause the overlapping responses to light. This allows the ratio of cone responses to more closely resemble that of a person with normal color vision. As a result, the EnChroma lenses enhance colors and may make reds and greens more vivid and distinguishable.

Donald McPherson, PhD, a glass scientist and EnChroma's cofounder, explains it this way:

"EnChroma’s glasses work by reestablishing the correct balance between signals from the three photopigments in the eye of the color deficient. The eyewear does this by removing small slices of light from the visible spectra. At the cortical level, the neural machinery is intact and perfectly functioning in the color blind, so once the correct ratios entering the eye are reestablished, the neural mechanisms excite and the correct color can be seen and perceived." via Forbes

Images taken from the Enchroma website

Will it work for me?
It depends! There are certainly no guarantees, but EnChroma suggests that their glasses can address the issue for 4 out of 5 individuals with anomalous trichromacy (which is what we described above- all 3 types of cones are present, but the sensitivity of one is shifted). These glasses would NOT work if you have a color deficiency where you are missing one of the three types of cones (dichromacy). The company offers a test that will give you an idea of how likely the glasses are to work for your type of color deficiency.

You can also visit an office that carries EnChroma lenses to try them out and ask an eye care professional for more information. Find an office near you via the website.


*EnChroma lenses do not cure color vision deficiencies, and they are not recommended for the color vision tests required for certain jobs.*


CliffsNotes: The most common color vision deficiencies occur as a result of a shift in the sensitivity of one of the cones, which causes a larger area of overlap between the red and green cones. EnChroma lenses use filters to remove the wavelengths of light in this overlap, which helps restore the proper ratio of cone responses, enhancing color vibrance and saturation. 


Additional recommended resources:

• Childish Wonder: Color Blindness (really great visuals and explanations!)
• From Kansas to Oz: How new glasses could change the way the colorblind see the world

amblyopia (lazy eye)

That darn lazy eye...

What is a "lazy eye?"
The term "lazy eye" is most often used to refer to a condition called amblyopia. Amblyopia is reduced vision in one eye, or less frequently both eyes, due to abnormal vision development in childhood (1). 

What causes amblyopia?

In simple terms, functional amblyopia occurs when something prevents the eye from focusing clearly. Any of the below factors can disrupt the normal development of the visual pathway and visual cortex: 

• Deprivation: This type of amblyopia is a result of an obstruction in the line of sight, like a cataract or a lid droop. The first step in treating this type of amblyopia is to remove the obstruction as early as possible. 
• Strabismus: This is the fancy name for an eye turn. When one eye is constantly misaligned, the brain is receiving two dissimilar images. So in order to prevent double vision, the brain ignores the visual input from the misaligned eye, which causes amblyopia. Some cases of strabismic amblyopia require surgery as a part of the treatment plan. Amblyopia can also occur when the eye turn is intermittent or alternating, but that is less frequent and less severe. 
• Refractive error: Refractive amblyopia occurs when there is unequal (anisometropic) refractive error or, less often, high equal (isoametropic) refractive error between the two eyes that goes uncorrected. If one eye is seeing significantly more clearly than the other, the brain will disregard the blurrier eye, causing amblyopia. This is especially difficult to detect because the eyes look normal and the child often won't complain about blur because he/she can see out of one eye. That's why eye exams are crucial!! Optometrists and ophthalmologists are trained to know what kind of prescriptions can cause amblyopia. 

The visual pathway is developing from birth to age 6-8, so amblyopia occurs during this time.

Many of the studies we'll discuss refer to amblyopia in terms of severity. This classification is based on the best correct distance visual acuity, which is how far down the eye chart a patient can read THROUGH their best prescription.

• Mild amblyopia: best corrected distance vision better than 20/40
• Moderate amblyopia: best corrected distance vision 20/40-20/80
• Severe amblyopia: best corrected distance vision worse than 20/80

How is amblyopia treated?
There are many valid answers to this question, and many theories that are currently being studied. We will focus on the evidence-based methods for treating amblyopia. Much of what we know about treating amblyopia is thanks to a group of optometrists and ophthalmologists known as the Pediatric Eye Disease Investigator Group, or PEDIG. This group has conducted numerous Amblyopia Treatment Studies, or ATS. 

Amblyopia treatment is dependent on many factors, such as the severity and type of amblyopia as well as the age and compliance of the patient, so treatment needs to be patient-specific. That being said, here's a general guideline for treating most cases of amblyopia. 

1. OPTICAL CORRECTION: The first line of treatment in most cases of amblyopia is correction of refractive error. Translation: glasses or contact lenses that correct vision to provide equally clear images to the retinas. Your eye doctor will likely use a dilating drop called cyclopentolate to assess the refractive error of the eye. Cyclopentolate relaxes the focusing system and gives the eye doctor a better idea of a patient's true prescription. Because of this, vision up close remains blurry for around 24 hours after the appointment.

Once the eye doctor determines the appropriate prescription, the prescription is written for full-time wear (that can be tricky with young children, but it is imperative). The eye doctor will follow-up every 4 to 6 weeks to check how vision is improving. 

Just having the optical correction in place makes a big difference, so don't underestimate the power of glasses! Glasses can improve vision even if the child still has a crossed eye with the glasses on.

In some cases, optical correction is all your need. But often, more therapy is involved.

2. DEPRIVATION: If further vision improvement is needed after full-time wear of glasses/contacts, deprivation of the better-seeing eye is added to the treatment regimen to encourage the use of the amblyopic eye. This deprivation is often achieved via patching, atropine, or Bangerter filters.      

• Patching
• Patching therapy involves using a patch (over the prescribed glasses/contacts) to cover the non-amblyopic or "good" eye, forcing use of the amblyopic eye. This can be done using an adhesive patch that goes on around the eye, or a soft patch that slides over the glasses.

Slide-on patches by OKeye on Etsy

A couple of adorable kids showcasing their adhesive patches.
@patchwithgus on the left, @chipperspiratedays on the right

• Patching has been used as amblyopia treatment for decades, but the way it is used has changed thanks to PEDIG's Amblyopia Treatment Studies (ATS). The ATS 2 study found the effectiveness of 6 hours of patching/day for severe amblyopia to be similar to full-time occlusion (2). Secondly, they found the effectiveness of 2 hours of patching/day for moderate amblyopia to be similar to 6 hours of patching (3). 
• That is where we get our recommendation of 2 hours of patching a day for moderate amblyopia and 6 hours of patching a day for severe amblyopia. Some children with severe amblyopia respond to as little as 2 hours of patching, so any amount is better than nothing!
• Both of the above studies involved at least an hour of near work during the patching hours, because that was thought to stimulate the visual system. Interestingly, the ATS 6 study found similar results in those that were assigned near tasks vs those that were assigned distance tasks.  There was a greater improvement in visual acuity in the near-task group among those with severe amblyopia, but it did not reach statistical significance. Worth noting: the study looked at "common" near tasks like reading or using the computer (4). There is reason to believe that specific near tasks designed to enhance focusing, improve tracking, fixation, etc. can improve outcomes other than visual acuity, though that was not studied.
• Another PEDIG study (ATS 15) showed that if visual acuity stops improving after 12 weeks of 2 hours/day patching therapy, increasing to 6 hours/day was more effective than continuing at 2 hours/day for another 10 weeks (5).

• Atropine
• Atropine therapy involves instilling a drop of atropine to the non-amblyopic or "good" eye to make vision blurry, forcing use of the amblyopic eye.  
• The ATS 1 study found patching and atropine therapy to be similarly effective initial treatments for moderate amblyopia in children age 3 to 7 years old (6). Another study found similar findings in children age 7 to 12 years old (7).
• Any parent of a child that is patching can attest to some difficulty with compliance, so atropine may be a less fussy option for kids (and parents). 
• The ATS 4 study found similar effectivity between daily use of 1% atropine and use only on the weekends in children age 3 to 7 with moderate amblyopia (8). Weekend atropine may also be effective for severe amblyopia, though improvements may be greater in younger children (9). 
• That is where we get our recommendation of 1 drop of 1% atropine instilled in the AM twice per week. It has been shown to be effective for moderate and severe amblyopia. 
• Atropine does have some systemic side effects, including dryness, flushing of skin, fever, confusion, unusual behavior, and irritability. Those rarely occurred in the studies.

• Bangerter filter
• Bangerter filters are translucent filters that are applied full time to the lens in front of the good eye, and they are available in different densities to degrade the image to different levels. Since this doesn't occlude vision entirely, it may help reduce suppression (10). 

Bangerter filter on a pair of glasses via Fresnel Prism and Lens Co

• The ATS 10 study compared the improvements in visual acuity between those treated with Bangerter filters and those with 2 hours of patching in moderate amblyopes age 3 to 10. The average difference between the two groups was less than half a line on the eye chart, but the study concluded that the filters were "not non-inferior" to patching. What does that mean in laymen's terms? The study did not conclude that the filter treatment effect was similar to that of patching, but it also didn't conclude that patching was definitely superior to filters. The study did show that the filters had less of a "negative impact" on patients and parents in terms of social stigma, compliance, etc (11). 

As you can see, there are multiple ways to go about occluding or depriving the "good eye." There are even other forms of occlusion that we did not mention here, including flicker glasses and occluder contact lenses. What works for one child may not be the best treatment for another, so it's great to have options that have been proven effective. Also, if one of these treatments isn't producing the expected results, we have the option of switching to another.

3) COMPUTER PROGRAMS AND ACTIVE VISION THERAPY: The most recent buzz around amblyopia treatment is reducing suppression by taking a binocular approach. Research is being done on the efficacy of dichoptic games, which involve simultaneous and separate stimulation of both eyes (unlike occlusion of one eye). High-contrast images are presented to the amblyopic eye and low-contrast images to the "good" eye. This type of therapy was found to be effective in adults (12). However, in a study (ATS 18) comparing 1 hour of binocular iPad game to 2 hours of patching a day in children 5 to 13 year old with amblyopia, the improvement after 16 weeks was better in the patching group (13). Participants lost interest in the game, and compliance wasn't great, so that may have contributed to the poor results. More studies need to be done to determine what types of anti-suppression therapy may produce better results. 

Adding vision therapy to amblyopia treatment is helpful in improving visual skills and binocularity. Vision therapy involves activities designed to reduce suppression and improve deficiencies in accommodation, form discrimination, and fixation, all of which are skills that are often poor in patients with amblyopia (14). 


Can you treat amblyopia in older kids? 
YES! In the ATS 3 study, PEDIG found that using either 2 hours of daily patching or weekend atropine as the initial treatment can be effective in improving vision for amblyopes age 7 to 12 years old, even if they've had prior treatment (15). That being said, amblyopia is MORE responsive to treatment in younger children, so this is one of the key reasons to have children see an optometrist EARLY!


Can amblyopia recur after treatment?
YES! According to ATS 2C, nearly 25% of amblyopic children under 8 years old experienced regression within a year of discontinuing treatment. The recurrence rate was similar in patients who stopped patching vs those that stopped atropine, and most cases occurred within 3 months of discontinuing treatment (16). The ATS 3 study showed that only 7% of 7 to 12 year olds studied experienced recurrence (17). The risk is much greater when those patching 6-8 hrs were stopped abruptly, so tapering off (ie: going from 6 hrs to 2 hrs) is advised, especially with younger children.  Because recurrence is possible, following up with your eye doctor is critical!


CliffsNotes: The first step in treating most cases of amblyopia is to correct vision, either with glasses or contacts. Surgical intervention may be needed in some cases. Occlusion therapy may be needed to improve vision beyond what is achieved by optical correction alone, and it's never a bad idea to enroll in vision therapy to improve eye teaming and visual skills. Amblyopia treatment may vary depending on the type and severity of the amblyopia as well as the age and compliance of the patient. Early intervention is key, so get your kids in to see their optometrist ASAP!


Additional Recommended Resources:

• All About Vision: Amblyopia
• AOA: Amblyopia

Helpful resources for ODs and OMDs: 

• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5396957/
• https://www.aoa.org/documents/optometrists/CPG-4.pdf