Abstract: An interchangeable filter facemask apparatus for providing a variety of different filtration options includes a mask body including a body perimeter portion, a sidewall extending from the body perimeter portion, a body left side, a body right side, a body nose side, a body chin side, a body outside, and a body inside. The sidewall has a filter aperture extending from the body outside through the body inside. A headband is coupled to the mask body. A body engagement member is coupled to the body outside adjacent an aperture perimeter of the filter aperture. Each of a plurality of filters has a filter outside, a filter inside, and a filter perimeter. Each filter has a filter engagement member coupled to the filter inside adjacent the filter perimeter. The filter engagement member is selectively engageable with the body engagement member to cover the filter aperture with the filter.

Abstract: A diagnostic tool for evaluating a patient's oculomotor system includes tests for measuring the amount of a patient's heterophoria and fixation disparity and determining whether these two measurements bear a normal or abnormal relationship. If the results of these tests do not bear a normal relationship, it is concluded that an oculomotor imbalance or dysfunction exists and further analysis should be performed to determine the precise nature of the dysfunction. The diagnostic tool may comprise a near-point card on which tests for heterophoria and fixation disparity are printed, as well as a graph indicating the expected or normal relationship between the results of these two tests. Additional diagnostic tests may be included on the card.