Aqueous flare is a pathognomonic sign of uveitis and is due to breakdown of the blood-ocular barrier with subsequent leakage of proteins into the anterior chamber. Aqueous flare is best detected using a very focal, intense light source in a totally darkened room. The passage taken by the beam of light is viewed from an angle. In the normal eye, a focal reflection is seen where the light strikes the cornea. The beam is then invisible as it traverses the almost protein- and cell-free aqueous humor in the anterior chamber. The light beam is visible again as a focal reflection on the anterior lens capsule and then as a diffuse beam through the body of the normal lens due to presence of lens proteins. If uveitis has allowed leakage of serum proteins into the anterior chamber then these will cause a scattering of the light as it passes through the aqueous. Aqueous flare is therefore detected when a beam of light joining the focal reflections on the corneal surface and the anterior lens capsule is visible traversing the anterior chamber. A slit lamp provides ideal conditions for detecting flare, however the beam produced by the smallest circular aperture on the direct ophthalmoscope held as closely as possible to the cornea in a completely darkened room and viewed transversely will also provide excellent results. The slit beam on the direct ophthalmoscope is not as intense and does not provide as many "edges" of light where flare can be appreciated most easily. Assessment of flare may be easier after complete pupil dilation due to the apparent dark space created by the pupil. Combined assessment of IOP and aqueous flare should be performed whenever glaucoma or uveitis is suspected because of the frequency with which these conditions co-exist.