Yeap Li Ling
BPharm, PhD, RPh
When you have an eye condition such as dry eyes, glaucoma, allergies, infections, eye injuries or even after a surgery, your ophthalmologist may prescribe you one or more eye drops. You can even purchase some of these eye preparations over-the-counter at pharmacies. Applying medications directly into the eyes is a preferred route of administration for eye conditions as it gives good local effect to the eyes with minimal side effects to the other parts of the body.
Let’s say you have dry eyes and you have just purchased a bottle of artificial tears from the pharmacy. The instruction on the bottle is to use the eye drops four times a day. How many drops do you instil into your eyes each time?
Consider another situation: how will you use your eye drops if you were prescribed with two or more eye drops? Do you instil one drop after another into your eyes at the same time?
If you are instilling more than one drop into your eyes at the same time, you are doing it wrong.
This is because your eyeballs can only accommodate a small volume, approximately one drop at any time. After instilling one drop into your eye, usually only a fraction of the applied medication penetrates the cornea and reaches the inner eye tissues. The rest of it is emptied from the eye and can be absorbed via the nasal cavity into the bloodstream.
Therefore, if you use more than one drop at the same time, more of the medication will be drained and absorbed into the body and this may cause more noticeable side effects. This may be particularly prominent with beta-blocker eye drops used for the treatment of glaucoma. Occasionally additional drops may also end up on the skin around the eyes, which can lead to allergic reactions. In addition, instilling more than one drop at a time can also increase tear production, which ultimately reduces the contact time of the medication with the cornea.
If you want more medication to reach your cornea, it is advisable to apply it regularly. When two or more different types of eye drops need to be administered at the same time of day, make sure you leave an interval of at least 5 minutes between instillation of each different preparation.
Some other useful tips that can be followed are:
- Look down and close your eyes without blinking and squeezing your eyes after instilling a drop.
- Use the tip of your index finger and press gently on the inside corner of the closed eye to close the tear duct for two to three minutes. This manoeuvre can reduce drainage, increase the effectiveness and reduce the amount of the medication absorbed into the bloodstream.
- Always start with eye drops and end with eye ointments if you are using both eye ointments and eye drops, making sure to leave an interval of at least 5 minutes between each preparation.
Below is a video demonstration on how to use an eye drop properly
- Lesar, T. (1996). Proper Use of Ophthalmic Products: Method of administration affects the outcome, toxicity, and cost of ocular drug therapy. Journal of the American Pharmaceutical Association (1996), 36(12), 704-706.
- Edwards, S. (2011). Eye Drops-What to Look For. Australian Pharmacist, 30(2), 106.
- Video credit: https://www.youtube.com/watch?v=PRjfGpejkhU
- Image credit: http://i1.allaboutvision.com/i/buysmart-2017/which-eye-drops-1200×630.png