• A new occluder to perform the cover test allows visualization of the covered eye through the occluder and direct observation of heterophorias. The occluder is composed of an aluminum-polyester filter mounted on a support in front of a 2.2-V light bulb.
Vila-Coro AA, Vila-Coro AA. Direct Visualization of Heterophorias Through a Unidirectional Occluder. Arch Ophthalmol. 1987;105(10):1436-1437. doi:10.1001/archopht.1987.01060100138045