Is it a Virus or just Allergies? Differentiating Follicles from Papillae

Red eye? Time to see your eye doctor via

It's that time of year again -- red eye time of year.  For every red eye patient that comes through the door I have a differential list going of 3 most likely suspects.

1) Do they wear multiple wear contact lenses?  Corneal ulcer is my first thought until I see otherwise

2) Do they itch?  Allergies and itching are almost always hand in hand

3) Is there crusting?  Viral conjunctivitis or pink eye as it is commonly called is so prevalent this time of year because of the number of viral colds going around.  Plus with back to school time, being around children is a really common infection source.  That means parents and teachers are at higher risk of coming to my office with a viral infection.

The reason that it is so important to see an eye doctor for a red eye is that your primary care doctor does not have the equipment to differentiate any of the above.  And the treatments for each of the above issues are vastly different!  You need a high powered ocular microscope to find a corneal ulcer (unless it is visible just looking at the person, in which case we are in a very emergent situation where there will almost certainly be permanent vision loss).  But the most important thing that is necessary when determining is this virus, allergies, or bacteria is a close microscopic evaluation of the under eyelid (tarsal) conjunctiva. Viruses typically have a follicular reaction in the conjunctiva, and bacteria and allergies classically have papillary reactions. Without a microscope, seeing this subtle difference is impossible.

Differentiating Papillae from Follicles

Papillary Reaction

A great example of papillae via

Giant Papillary Conjunctivitis -- Due the the chronic nature of inflammation, the papillary reaction is larger as the areas of irritation expand into each other.

Bacterial infections are very rare by comparison, so the most likely culprit when I see papillae under the eyelid is allergies.  Papillae are signs of chronic irritation, where the conjunctival tissue has become elevated and swollen due to repeated exposure to an irritant.  There are two important distinctions that are hallmark signs of papillae:

1. Red Center =  Papillae are elevations of the vascular conjuncitval tissue so there will be a red central vascular core to the lesions
2. Distinct Elvations = The conjucntival tissue has fibrous connections that limit the size and expanse of swelling.  This means distinct, well separated bumps in the papillary reaction.  The only time this logic doesn't fully apply is when the inflammation has been around for so long that the bumps begin to coalesce, creating the large cobblestone appearance we associate with giant papillary conjunctivitis.

Follicular Reactions

Follicular reaction via

While papillae are consistent with a local irritation, follicles are a sign of an immune reaction in the area.  This finding is almost always an indication of a viral infection of the eye.  Follicles have a larger appearance than papillae, and have a white central core since they are really accumulations of cellular level inflammatory agents -- lymphocytes, lymphoblasts, and macrophages if you remember your microbiology.   The big tell-tale sign of follicles are:

1. White Center = look for that inflammatory matter filling the center of the bump

Take Home

Having a hard time seeing the difference?  That's understandable because it takes doctors that are trained in this numerous patient encounters to develop a quick sense of which is which, and there are still some reactions that have questionable appearances with characteristics of both.  My real take home for any non-OD readers of this post is that a red eye takes a specialist to properly diagnose. The tell-tale anatomy is so nuanced, it is impossible to see without the proper equipment.  So please, see your eye care provider for any eye care needs so that you get the proper treatment without delay.