When you visit your ophthalmologist, one of the key things he wants to know is the severity of the iritis. Talk of "cells", "flare", "KP's", and "synechiae" are simply ways of describing the level of inflammation. Here's a quick jargon-buster:
It is possible with the slit-lamp to see individual white blood cells in the anterior chamber of the eye. The anterior chamber ("AC") is the part of the eye between the cornea at the front and the iris. In iritis, as in most other kinds of inflammation, white blood cells rush to the scene. Some end up in a kind of limbo in the anterior chamber (they don't do very much when they are floating around there).
You may see or hear the notation "cells +" or "cells ++" or "cells +++". This shorthand for how dense the cells are. "Cells +" refers to more than five but less than fifteen cells in a 3 x 1 mm slit lamp beam and the more plus signs, the more cells the ophthalmologist can see. Generally speaking, the fewer cells the better; when there are few or no cells, the eye may be described as "quiet".
The anterior chamber is normally clear as crystal -- it has to be, in order to let light into the eye undistorted. In iritis, however, stray protein molecules leak from the bloodstream into the anterior chamber, fogging it up. This is "flare".
Again, flare can only be seen on a slit lamp, on the same settings as the ophthalmologist looks for cells. Instead of individual cells, when light cuts through flare it looks a bit like shining a torch (flashlight) on a misty night -- the flare scatters the light, making the normally invisible beam visible.
When there is a lot of protein in the anterior chamber, it may coalesce into "fibrin".
Keratic precipitakes are deposits on the back of the cornea found during and after iritis. They are thought to originate from clumps of white blood cells adhering to the cornea. Simplistically, the more KP's, the more severe the iritis. The character, shape and configuration of KP's can give important clues to the origin of the iritis.
The iris sits directly in front of, and touching, the crystalline lens, the structure inside the eye which allows you to focus on near and far objects. In iritis, the iris tends to stick to the lens. When this happens, the points of adhesion are called posterior synechiae. (Anterior synechiae, which are rare, are adhesions between the iris and the cornea.)
Posterior synechiae can lead to complications, and they can be avoided by using drops to dilate the iris. One possible complication is If the iris is permitted to stick to lens, "pupil block" may occur which may lead to a increase in the pressure in the eye, which may damage structures of the eye. When posterior synechiae occur, iris pigment may stick permanently on the lens. This may cause optical distortion.
The avoidance of posterior synechiae and pupil block is the principal reason for prescribing drops which dilate the pupil (mydriatrics). When the pupil is dilated, it is much less likely to stick to the lens. Mydriatric drops such as atropine and cyclopentolate also keep the eye comfortable by relaxing the ciliary muscle (cycloplegia).
This means that the eye is not inflamed. No, before you ask, there is no such thing as a "noisy" or "loud" eye. You may see written in your notes "deep and quiet" or "D + Q". This means that the anterior chamber is deep and quiet, the way it should be.