<prompt> This instrument can be used in all except-Finchams testIridectomyCorneal tattooingAxis of cylindrical lens in refractive errors  <response>: Stenopaeic slit The rectangular apeure is 1mm in width and 15mm in length. Uses of the stenopaeic slit - Determination of Meridian Of Optical Iridectomy- in patients with a corneal scar or lenticular opacity. To diagnose cases of cataract, differentiate between colored halos caused in Angle-closure glaucoma and cataract by Finchamstest. Determine power and axis of the cylinderical lens- The slit apeure acts as an elongated pin-hole, only allowing light in the axis of the slit to enter the eye. Hence, when the slit lies in one principal axis of the astigmatism eye, the second line focus is eliminated and the blur of sturms conoid reduced thus allowing a clearer image to be formed. 