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H A Knoll

Publications and source records attributed to H A Knoll.

6 recordsLinked to original sources
PubMed1987

Analysis of blink-induced vertical motion of contact lenses.

This report discusses blink-induced vertical motion of contact lenses as measured with a slit lamp. The motion seen this way represents the displacement of the lens from its position just before a blink to its position immediately after the blink. Motion amplitudes reported in the literature will be discussed in the context of a hypothesis which seeks to account for lens motion by taking into consideration the post-lens tear film characteristics, the diameter of the lens, and the geometry of the anterior segment of the eye.

Blinking↗
PubMed1986

Further studies of contact lens motion during blinking.

Contact lens motion is felt to be of increasing importance in connection with debris elimination, particularly in extended wear lenses. Thus an improved analysis is made of a simple model for investigating the initial motion of a hard contact lens over the eye during blinking. It is shown that the assumption of constant tear film thickness is a reasonable one. This greatly simplifies the analysis. Various vertical force vs. time variations are considered and lens velocity/time graphs and maximum lens displacement calculated. These are in good agreement with the results of experiment.

Blinking↗
PubMed1976

Recent developments in automatic refraction.

A detailed description of the Ophthalmetron is given. This is an automatic refractometer using the principle of infra-red retinoscopy and having a sensitivity range from -18.00 D to +17.00 D with a resolution of 0.25 D. By means of a rapid light scan across the patient's pupil the instrument determines the direction of motion of the retinal reflex in all meridians and a movement null-point is determined electronically. Results are then plotted automatically on a chart drum. Some early validation studies have shown the Ophthalmetron to provide a refraction end-point in good agreement with conventional retinoscopic findings. The paper concludes with an appendix in which the features of three commercially available automatic refractometers are compared.

Humans↗