Abstract: A rod laser having a ring cavity configuration, and including a polarization rotator to compensate for birefringence of the laser's rod. Preferably, the rotator is a 90.degree. crystal quartz rotator. In a preferred embodiment, the ring laser is a stable quasi-unidirectional, non-confocal solid state ring laser. A telescope, including at least two lenses with variable inter-lens spacing, is preferably positioned in the laser beam path as closely as possible to the laser rod. The spacing between the telescope lenses is preferably controlled by a servo mechanism. In a preferred embodiment, a power density detector is provided for producing a beam power signal, and a means (which may include a microprocessor) coupled to the power density detector generates a servo mechanism feedback control signal from the beam power signal.

Abstract: A tonometer with an improved objective unit containing a fluid discharge tube having a portion thereof extending into a plenum chamber enhances the consistency of repeated regulated air discharges. The consistency is further enhanced by texturizing the inner wall of the discharge tube. Since the discharge tube extends into the plenum chamber, the objective unit can have substantial interchangeability with other tonometers.

Abstract: An instrument for photographing the ocular fundus is aligned by using a physical aperture designed to permit illumination of only a small area of the optic disc for minimal patient awareness of incident light and corresponding pupil dilation without mydriatics. The increased field of view and obliquity of viewing afforded by pupil dilation permits flashing of the fundus for photographic recording without image obscuring corneal reflections. The light restricting aperture is removed immediately before photographic recording.

Abstract: A device for verifying instrument readings of transient force of a moving fluid column including a paddle depending from a taut wire torsion bar. The unit is adaptable to instruments utilizing fluid pulses in testing objects for resistance or vulnerability to fluid stream pressure, e.g. ophthalmic tonometers. With disposition of the paddle in an instrument fluid path and a known torsional force applied to the supporting wire, the force required of a fluid column to displace the paddle may be established for verification of instrument readings and/or indication of defective instruments.

Abstract: A mold for forming lens blanks to meniscus shapes under applied heat and a force created by partial vacuum. A cupped lens shaping surface in the mold is cushioned and covered with a synthetic fabric for effecting exceptional accuracy in lens blank conformance to shaping surface curvature, optimum surface smoothness and quick release upon completion of a forming cycle.