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

[2][3] Watzke-Allen test is done by projecting a thin line of light over the macula with a slit lamp.

[5] It is best performed in a dilated eye, projecting a slit beam of approximately 100 μm.

[6] The patient is asked to describe whether the light line is straight or narrow or has a gap (break).

[6] 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.