Watzke-Allen test (WAT) also known as Watzke-Allen slit beam test (WASBT) is a test used in the diagnosis of a macular hole, a condition affecting the

macula The macula (/ˈmakjʊlə/) or macula lutea is an oval-shaped pigmented area in the center of the retina of the human eye and in other animals. The macula in humans has a diameter of around and is subdivided into the umbo, foveola, foveal avas ...

r region in the

retina The retina (; or retinas) is the innermost, photosensitivity, light-sensitive layer of tissue (biology), tissue of the eye of most vertebrates and some Mollusca, molluscs. The optics of the eye create a focus (optics), focused two-dimensional ...

of the eye. The test is done by projecting a thin line of light over the macula with a

slit lamp In ophthalmology and optometry, a slit lamp is an instrument consisting of a high-intensity light source that can be focused to shine a thin sheet of light into the eye. It is used in conjunction with a biomicroscope. The lamp facilitates an ...

Theory

Watzke-Allen test is a test used in the diagnosis of a macular hole. It is a subjective test based on photoreceptor (

cone cell Cone cells or cones are photoreceptor cells in the retina of the vertebrate eye. Cones are active in daylight conditions and enable photopic vision, as opposed to rod cells, which are active in dim light and enable scotopic vision. Most v ...

) displacement. Test can be used to differentiate full thickness macular hole from other similar conditions and also to assess retinal function after surgical closure of the hole.

Procedure

Watzke-Allen test is done by projecting a thin line of light over the macula with a

. A fundus lens or macular lens is used to aim beam of light on the macula. It is best performed in a dilated eye, projecting a slit beam of approximately 100 μm. The slit is projected in both vertical and horizontal orientations. The patient is asked to describe whether the light line is straight or narrow or has a gap (break). A straight line indicates an intact fovea where as narrow or gapped line indicate macular holes. A narrowing indicates isolated, damaged but functional foveal receptors. Patient may be asked to draw what he sees.

Advantages and disadvantages

The advantages of WAT are its availability, affordability, easy to perform and ability to be used through relatively opaque media, which can help overcome the limitations of spectral-domain OCT, however, it is not known whether the measurements recorded by WAT reflect the true extent of photoreceptor displacement.

References

{{DEFAULTSORT:Watzke-Allen test Diagnostic ophthalmology Eye procedures Optometry