Monday, January 28, 2019

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-ANaphazoline 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*