The Optical Cross Cylinder 0.50D is a handheld refraction tool used by eye care professionals during subjective vision testing. Also known as a Jackson Cross Cylinder (JCC), it assists with refining astigmatic cylinder power and axis by allowing the practitioner to compare alternative lens positions during refraction.

The optical cross cylinder features a clear circular lens with marked principal meridians and a knurled metal handle for controlled positioning. The lens diameter is approximately 38 mm and the overall length is approximately 100 mm.