When less is better – Using Eye Drops!

When less is better – Using Eye Drops!

Dr G.P Mohanta,Professor, Annamalai University

Eyes are the most sensitive organs of our body and the eye drops are most common form of medications used for the treatment of eye disorders. Eye drops directly deliver the desired medication to the eye. Most of the time we believe more is better. Use more than one drop at a time for better therapy. But is not true! Here less is better. Smaller drops are more effective.

The capacity of the eye to retain fluid (eye drop) is limited. A blinking eye can accommodate or retain a volume of maximum 30 µL including the normal tear volume of 7-8 µL. Unblinking eye, on the other hand, can retain only about 10 µL. A single drop of eye drop (solution) delivers around 50 µL which is much higher than the retention capacity eye. Ideally a volume for instilling into eye should be 5-10 µL.  The sizable portion of the instilled dose either spills on to the cheek (may cause contact allergy) or is very quickly drained away. Similarly, if multiple drops are applied at time, most of the instilled solution would be lost due to spillage or drainage.  

The eye drops are applied to the pocket formed by gently pulling the lower eye lid downward. Upon instillation the lower lid should be released and the eye is kept closed at least for a minute without blinking, rubbing or wiping. The closed eye allows the medication to spread over the eye.

A single drop at a time is advised not only for better therapy but also to minimize waste. This also prevents undesired absorption or contact skin allergy from washed out drops. 

In addition to general guidelines for maintaining hygienic practices to maintain sterility of the products, the patients should be educated on the following aspects:·         Only one drop should be used at a time. If second drop is recommended, then allow few minutes before applying next drop.·         If more than one type eye drop is to be applied (different medications), patient should wait at least for three minutes before applying the next drop.·         Wait of at least 15 minutes before putting back the contact lenses.·         Do not use after the expiry date and do not use after 28 days (four weeks) of opening the container.Report back to your physicians if the product produces irritation