Abstract: A surgical mask is provided with a vapor barrier for preventing clouding or fogging of optical aids or devices used by the wearer of the mask. The vapor barrier comprises a contoured strip of elongated soft closed cell foam material interposed between the upper edge of the mask and the wearer's face. The interposed material contours itself to and sufficiently extends over the wearer's face to form a seal and vapor barrier preventing fluid vapor exhausted from the wearer's nose and mouth from contacting spectacles, optical loupes or other optical instruments worn by the wearer and susceptible to clouding or fogging.

Abstract: A surgical mask is provided with means for preventing fogging of optical aids used by the wearer. The means comprises a strip of pliable material bonded to a layer of soft foam interposed between the upper edge of the mask and the wearer's face. An air impervious film sheathes the layer of foam and extends laterally therefrom a sufficient distance to cover an upper portion of the mask in the area below the wearer's eyes. The interposed material shapes itself and sufficiently extends over the wearer's face to form a seal and a moisture barrier preventing fluid vapor in the wearer's breath from contacting eye glasses or other optical instruments worn by the wearer and susceptible to fogging.

Abstract: Apparatus and method provide for automatically measuring the refractive error of the human eye and thus the prescription for lens or eye glasses for correcting this error. Test symbols are alternately presented at two different locations on a test screen under control of a programmed automatic data processing system. The symbols are viewed by a subject through a lens system whose power may be continuously varied also under control of the data processing system. The data processing system also varies the size of the symbols presented to compensate for the power of the lens system so that a given symbol will appear to the subject to be of constant size. In one illustrative embodiment of the present invention, the subject communicates with the data processing equipment via a subject response device to indicate his preference for one or the other of the symbols presented at the two locations.