The Elusive Foreign Body Sensation

By Karla Zadnik, O.D., Ph. D.

JULY 1997

It's a routine occurrence in any optometric practice to have a rigid gas permeable contact lens patient call or show up at the office complaining of a foreign body sensation. The patient may not use that term, but he or she will describe a persistent irritation, like an eyelash in the eye, or a burning or stinging sensation. Sometimes the sensation goes away when the contact lens is removed; sometimes it doesn't. Differential diagnosis of foreign body sensation in a contact lens-wearing patient requires a bit of detective work.

WHAT HAPPENS WITH LENS REMOVAL?

If the foreign body sensation subsides when the lens is removed, look for something on the lens. First, inspect the lens with white light using the slit lamp. Many surface abnormalities or deposits seem to disappear after fluorescein is instilled. A surface that looks smooth and protein-free during fluorescein examination may look disrupted and deposited in white light.

Inspection under white light is also the easiest way to look for a chip in the edge of a lens. Sometimes a chip looks like a triangular piece of the lens has been removed. Other times, it's as if a piece of plastic has been shaved off the edge.

Make-up can deposit on a lens. Eye shadow with metallic particles looks shiny and glittery. Mascara looks dark brown or black and clumpy. Hand or face creams look greasy or slick.

Routine polishing will remove many surface deposits. You may even be able to polish an edge chip smooth if it is small and parallel to the edge of the lens.

FIG. 1: CORNEAL STAINING FROM CONTACT LENS WEAR.

DISCOUNTING INITIAL LENS SENSATION

Recently, we saw a patient in The Ohio State University College of Optometry Contact Lens Clinic who complained at the dispensing visit of an irritation in the right eye that wasn't present in the left. When we inspected the lens at the slit lamp, we observed a bit of unidentifiable debris that had embedded itself just adjacent to the dot denoting the right lens. We polished the debris off, and the sensation stopped.

If we had attributed the irritation to initial lens sensation, we would not have solved the problem. And, if we had instilled topical anesthetic at the dispensing visit, the problem would have presented at the patient's home that evening.

WHEN THE ONLY EVIDENCE IS CORNEAL DISRUPTION

Sometimes there is evidence of corneal insult without obvious lens abnormality. Just this week, we saw a patient who had a two-month history of her right lens "pinching" after about six hours of wear. The symptoms subsided after she removed and cleaned the lens but returned within an hour of reinsertion. The symptoms did not occur when she wore an old right lens. Although we saw nothing on the surface of the lens and the fit was acceptable, we observed a large central area of nearly confluent punctate staining in the right eye (Fig. 1). We polished the lens and will replace it if the problem does not
resolve.

THE ANSWER MAY BE A FOREIGN BODY

Discomfort that persists after lens removal should be suspect as non-contact lens related. Whether or not the patient reports a history of a foreign body striking the eye, you should inspect the corneal and conjunctival surfaces. Evert the upper lid, then double-evert. Remove any foreign body you find. Irrigate the eye even if you don't see a foreign body.

THE SENSATION IS REAL

When a patient reports a foreign body sensation, you must assume that it has an attributable cause and look for that cause until you find it. From lens defect or deposit to actual foreign body on the cornea or the conjunctiva, the symptom is real and its cause must be eliminated. CLS