03 Dec How Eye Drops For Cataracts Work
Eye Drops Must Pass Through the Corneal Epithelium and the Stroma to Enter the Eye
Eye Drops for Cataracts are the preferred method of delivering medicine to the eye for conditions like glaucoma and to protect the eye after cataract surgery.
To treat conditions inside the eye, the medication has to diffuse through the cornea. This is much harder than it might initially appear. The cornea has a number of defenses to keep things from getting into the eye.
You probably remember the phrase, “oil and water don’t mix.” Oil and things chemically like oil (lipids) dissolve in oil. Water and things chemically like water dissolve in water.
The Corneal Epithelium
The outermost layer of the cornea is the epithelium. It is contains a lot of lipids. For an eye drop to pass through the epithelium, it has be a bit like oil (lipophilic).
The Corneal Stroma
The middle layer of the cornea is more water based. For an eye drop to pass through this layer it has to be a bit more like water (hydrophilic).
Now you can understand how difficult it is to get the liquid to where it needs to go. It has to have both the ability to dissolve in oil (lipophilic) and water (hydrophilic).
Few naturally occurring substances can pass through both the “oil like” epithelium and the “water like” stroma in appreciable amounts. Fortunately, some clever scientists have created medication that can do just that. We live in an age of wonder and miracle!
Eye Drops For a Cataract
Preservatives and LASIK Surgery
There are a couple of other tricks that chemists have developed to get the liquid medication to where you need it. Preservatives keep bacteria from contaminating the eye drops, but they can also serve another function. Preservative can be rough on the epithelium. If they break down some of the defenses of the epithelium, a hydrophilic drug could bypass the broken down epithelium and gain access to the deeper corneal stroma where it can dissolve in and easily pass the rest of the way.
Prodrug Method
Another way to get the liquid to where it can help your eyes is to have is to have a lipophilic attachment on the drug molecule that lets it pass through the epithelium. The attachment is removed by naturally occurring enzymes so that remaining hydrophilic molecule can pass freely through the stroma into the eye. Ilevro (anti-inflammatory) is among the commonly used eye drops for cataracts and Latanoprost is a commonly used eye drop for glaucoma that use a pro drug strategy to properly deliver the medication.
Drug Vehicles
A drug vehicle holds and carries the drug. If the drug is in a liquid vehicle, it can be easily washed away by the tears before very much drug can diffuse into the eye. If the drug is carried by a thicker eye drop or even an ointment, it can stay in the eye longer before the tears wash it away so more of the drug can enter the eye.
Eye Drops After Cataracts
Ilevro Uses Prodrug and Vehicle Strategies to Get More Drug into the Eye
Antibiotic Eye Drops for Cataracts
Vigmox is a common antibiotic used for cataract treamtment. It does not have any preservative. The antibiotic itself wards off bacteria. The molecule enters your eyes very readily so high concentrations are reached. Compare this to Besevance, another antibiotic. It also is a very strong antibiotic, but the scientists have used twice the normal amount of preservative. This helps the molecule get enter the eyes but also increase the kill time for bacteria on the surface. This means that if bacteria are on the surface of your eyes, the Besevance kills them twice as fast as most other antibiotics specifically because of the extra preservative.
Which is better, less irritation with a molecule that readily enters your eyes or more preservative irritation that kill bacteria twice as fast and needs the preservatives to get some of the drug where it needs to go? The good news is that we have choice provided to us by the brilliant scientists that have dedicated their lives to making our lives better.
Anti-Inflammatory Eye Drops for Cataracts
I usually prescribe two types of anti-inflammatory medications to help the healing process after surgery. The first of the anti-inflammatory medications is the steroid. Durazol and Predforte are common steroid drops. The non-steroidal drops (NASIDs) are the second category. Both of these decrease inflammation. Their effects are additive, so it is worth being on both drops. Ilevro and Prolensa are common NSAIDs.
If you have any further questions about eye drops you are using for your cataract surgery, LASIK surgery, or for you glaucoma, please leave a comment or schedule a time to meet with me at one of my offices.
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