What are emulsion eye drops?

Emulsion eye drops are drops in which tiny droplets of oil are dispersed through a water-based liquid, held together by ingredients that help oil and water stay mixed. The suspended oil scatters light, so emulsions look milky or cloudy instead of clear. Quell combines oils with sterile water this way, and its label notes: Product appears as a milky brown solution. The oil is there because Quell is designed to reinforce the tear film’s oil layer to help reduce moisture loss.

Emulsion meaning, in plain terms

Oil and water don’t dissolve into each other. Pour them together and they separate into layers. An emulsion breaks the oil into droplets small enough to stay spread through the water, usually with help from an emulsifier, a kind of ingredient with one end that’s drawn to water and one end that’s drawn to oil. Milk, mayonnaise and many lotions are everyday emulsions. In eye drops, the idea is the same, made under the sterile conditions an eye product requires.

Not every eye drop is an emulsion. Many are clear solutions, in which every ingredient dissolves completely in water. Some others are gels or ointments, which are thicker. The type is about how the ingredients are combined, not about which brand made them.

Why would an eye drop contain oil?

Because the eye’s own tears contain it. The tear film has three layers: a mucus layer against the eye’s surface, a watery layer in the middle, and a thin oil layer on top. That oil layer slows evaporation from the watery layer underneath. The tear film’s oil layer, explained goes into more detail.

A drop that’s purely water-based adds moisture to the watery layer. A drop that includes oil is aimed at the top layer too. Quell is designed to reinforce the tear film’s oil layer to help reduce moisture loss, which is why it contains oils and comes out as an emulsion rather than a clear liquid.

What’s in Quell that makes it an emulsion

Quell’s active ingredients are Glycerol (1.0%), Polysorbate 80 (1.0%) and Light Mineral Oil (0.5%). Its inactive ingredients are Caprylyl Glycol, Dead Sea Salt (Sodium Chloride), Emu Oil, Glyceryl Laurate, Glyceryl Undecylenate, Manuka Honey, Polaxamer 188, Sterile Water, Terminalia Chubula and Tromethamine. A few of those play recognizable roles in an emulsion:

• Oils: Light Mineral Oil (0.5%) is an active ingredient listed as an emollient, and emu oil is among the inactive ingredients. These make up the oil phase.
• Water: sterile water is the base the oil droplets are spread through.
• Ingredients that help them mix: polysorbate 80, which the label lists as a lubricant, is also chemically an emulsifier. What does polysorbate 80 do in eye drops? explains its double role.

The label doesn’t use the word “emulsion.” It describes the result instead: Product appears as a milky brown solution. The site adds a reassurance written for the buy button: The eye drops have a naturally milky-brown appearance. This is normal and does not indicate a problem with the product.

Why are some eye drops milky instead of clear?

In a clear solution, everything is dissolved down to the molecular level, so light passes straight through. In an emulsion, the oil droplets are big enough to scatter light, and scattered light looks white or cloudy. That’s the same reason milk is opaque. Quell has a brown tint on top of that, from its natural ingredients, so it looks milky brown. Why is Quell milky brown? covers the color itself.

What matters for safety is consistency. The label says: If this product changes color. If a bottle looks noticeably different from how it looked when it arrived, don’t use it.

Do you shake emulsion eye drops?

Some emulsion products say to shake before use and some don’t; the instruction that counts is the one printed on that product’s label. Quell’s directions read: Apply 1 drop 3 times per day in each eye, with no mention of shaking. Do you need to shake eye drops? explains how to read that silence. If you’re unsure about a particular bottle, ask a pharmacist with the carton in hand.

Do emulsion drops blur your vision?

Milky drops can blur vision briefly after they go in, because a cloudy liquid sits on the eye’s surface until blinking spreads it out. That’s a reason to put a drop in when you don’t need sharp vision right away, not while driving or reading something important. If blurring or any change in vision doesn’t clear, the label is clear about what to do: Stop use and ask a doctor if you feel eye pain or changes in your vision, if irritation or redness continues, or if the condition worsens or persists for 72 hours. Is it normal for vision to blur after eye drops? has more.

Emulsions and storage

Heat and cold can stress any liquid product, and an oil-and-water mix is no exception. Quell’s label gives a range: Store between 15° to 30°C (59° to 86°F). Keep the bottle out of hot cars, away from heaters and out of the freezer. Handle it as the label says, too: Do not touch tip of bottle to any surface to avoid contamination.

Who emulsion drops may not suit

Ingredients vary by product, so read each label’s warnings. Quell’s says: Caution should be used in those with egg or bird allergies — For use in the eyes only. The caution relates to emu oil. Quell’s label doesn’t give directions for children, for use with contact lenses, or for use alongside other eye drops; for any of those, ask your eye doctor or pharmacist.