Fincham\'s test differentiates cataract from –

The coloured halos in primary angle closure glaucoma must be differentiated from those found in acute purulent conjunctivitis and early cataractous changes :- In conjunctivitis, the halos can be eliminated by irrigating the discharge. The halos of glaucoma and immature cataract may be differentiated by Fincham's test in which a stenopaeic slit is passed across the pupil. During this test glaucomatous halo remains intact, while a halo due to cataract is broken up into segments.