The anterior chamber is the space at the front of the eye, positioned between the transparent cornea and the iris. This chamber is filled with the aqueous humor, a unique, clear fluid. In a healthy eye, this fluid is transparent, which is necessary for unobstructed vision. The detection of “cells” within this chamber is a significant medical finding that signals inflammation or other pathology. The presence of cells is never considered normal and indicates that a barrier inside the eye has been compromised, prompting immediate investigation by an eye care specialist.
The Anterior Chamber and Aqueous Humor
The anterior chamber is filled with the aqueous humor, a clear, watery substance that is constantly produced and drained within the eye. This fluid is secreted by the ciliary body, a ring of tissue located behind the iris, and flows through the pupil into the anterior chamber. It is composed mostly of water, but also contains essential nutrients such as glucose and amino acids, though it is very low in protein compared to blood plasma.
The primary functions of the aqueous humor include nourishing the avascular structures of the eye, specifically the lens and the posterior cornea, which lack a direct blood supply. The constant circulation of this fluid also removes metabolic waste products from these tissues. Furthermore, the aqueous humor is responsible for maintaining the intraocular pressure (IOP), which keeps the eyeball properly inflated and in its spherical shape.
The fluid is normally optically clear and acellular, meaning it contains no suspended particles or inflammatory cells. This clarity is maintained by the blood-aqueous barrier, a protective layer that tightly regulates what substances can pass from the blood vessels into the aqueous humor. When this barrier is functioning correctly, the fluid remains pristine, allowing light to pass through unimpeded to the retina.
Identifying and Grading AC Cells
The “cells” seen in the anterior chamber are primarily inflammatory cells, usually white blood cells (leukocytes) that have leaked from blood vessels due to inflammation. These cells are visualized by an ophthalmologist using a specialized microscope known as a slit lamp. The room must be darkened, and a narrow, high-intensity beam of light is passed through the anterior chamber fluid.
The detection method relies on a physical principle called the Tyndall effect, which causes the inflammatory cells and leaked proteins to scatter the light beam. This phenomenon is similar to how dust motes become visible when a sunbeam shines through a dark room, making the normally invisible aqueous fluid appear hazy or “foggy.” The haziness caused by leaked proteins is referred to as “flare,” while the individual floating particles are the “cells.”
To quantify the severity of the inflammation, eye care professionals use a standardized clinical grading system. The clinician focuses the slit lamp beam to a specific size, typically a 1-millimeter by 1-millimeter area, and counts the number of cells seen in that beam. This cell count is then assigned a grade from 0 to 4+ using the Standardisation of Uveitis Nomenclature (SUN) criteria. This reproducible grading system allows doctors to monitor the patient’s response to treatment and track the progression of inflammation.
The grades are defined by the number of cells counted in a 1mm x 1mm slit lamp beam:
- Trace: 5 to 10 cells.
- 1+: 10 to 25 cells.
- 2+: 25 to 50 cells.
- 3+: 50 to 100 cells.
- 4+: More than 100 cells, often accompanied by fibrin or a hypopyon (layered white blood cells).
Conditions That Cause AC Cells
The appearance of inflammatory cells in the aqueous humor is a direct symptom of inflammation, which causes the blood-aqueous barrier to become permeable. This breakdown allows plasma proteins and immune cells, such as lymphocytes and macrophages, to exit the blood vessels of the iris and ciliary body and enter the anterior chamber. The most common cause of anterior chamber cells is uveitis, the general term for inflammation of the uvea, the middle layer of the eye.
Specifically, anterior uveitis, also known as iritis, involves inflammation primarily of the iris, leading to the leakage of cells. Uveitis can be triggered by infectious agents like herpes simplex, varicella zoster, or tuberculosis. It can also be associated with systemic autoimmune diseases such as juvenile idiopathic arthritis or ankylosing spondylitis.
Non-infectious causes include blunt trauma to the eye, which physically disrupts blood vessels and causes inflammatory cells to leak into the chamber. Cells may also be present following intraocular surgery, representing a temporary and expected inflammatory response. In rare cases, a high concentration of red blood cells, known as hyphema, can be seen following trauma or surgery, though these are distinct from the white blood cells that signal infectious or autoimmune inflammation.
A severe inflammatory response is commonly seen in certain forms of uveitis or in endophthalmitis, a serious intraocular infection. The presence of cells is not a diagnosis in itself, but a clear sign that a disease process is actively occurring within the eye.
Management and Treatment
The management of anterior chamber cells is focused on two goals: rapidly suppressing the inflammation and identifying and treating the root cause. Because the cells themselves are a sign of uncontrolled inflammation, the immediate step is typically to reduce the immune response within the eye. The mainstay of treatment for anterior uveitis is the use of topical corticosteroid eye drops.
These steroid drops, such as prednisolone acetate, are often administered frequently, sometimes every hour initially, to achieve high concentrations within the anterior chamber and block the inflammatory cascade. Corticosteroids work by downregulating the production of inflammatory mediators, which ultimately reduces the permeability of the blood-aqueous barrier and stops the leakage of cells and proteins. The dosage is carefully tapered over weeks or months as the cell count decreases.
Another important component of treatment involves the use of cycloplegic agents, such as atropine or cyclopentolate. These drops help relax the iris and ciliary body muscles, which are often in spasm due to the inflammation, thereby relieving associated pain and light sensitivity. Cycloplegics also serve a preventive role by dilating the pupil, which helps to prevent the iris from sticking to the lens, a complication known as posterior synechiae.
The efficacy of the treatment is monitored by regular slit lamp examinations to track the reduction in the cell grade. Once the inflammation is controlled, the cells should clear from the aqueous humor, returning the fluid to its normal, optically clear state. Long-term management often involves a workup to rule out underlying systemic or infectious diseases to prevent recurrence, as untreated or chronic inflammation can lead to complications like glaucoma or cataracts.