Determination of absolute size of fundus objects.

Background: Creating multiple beam interference fringes on the retina using the "retina fringe projector" (RFP) provides us with a scale which can be used to determine the absolute size of objects at the fundus.

Methods: The procedure is tested on an model eye, the optical parameters of which are varied in order to simulate different refraction conditions. The RFP was used to determine the size of a known object at the model fundus; the result was then checked against the real value of the object.

Laryngeal morphometry with a new laser 'clip on' device.

Background And Objectives: Qualitative laryngoscopic investigations belong to diagnostic routine in laryngology. Nevertheless, quantitative morphometric measurements of intralaryngeal structures have been difficult by now.

Study Design/material And Methods: The development of a two-point-light projection method for endolaryngeal measurements that works with a double reflecting mirror and green laser light is shown.

Study of the effect of involuntary user movement on the potential light hazards from some ophthalmic instruments.

A study was undertaken to determine whether involuntary user movement provides a basis for relaxing the measurement conditions for evaluating the potential optical radiation hazards to the eye from slit lamps and indirect ophthalmoscopes. This was accomplished by assessment of the extent to which light from these devices can be maintained in focus on a 1-mm-diameter fiber-optic cable for 45 s. The results suggest that, although involuntary user movements can be significant, they do not provide a basis for relaxing the measurement conditions for evaluating the potential optical radiation hazards to the cornea and lens from slit lamps and indirect ophthalmoscopes.