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Biomedical subjects

O Pomerantzeff

Publications and source records attributed to O Pomerantzeff.

8 recordsLinked to original sources
PubMed1991

A new set of variable-contrast visual acuity charts.

Using a computer plotting technique, we designed four variable-contrast visual acuity charts. The contrast of the first 3 is 90, 15, and 2.5%, respectively. The fourth is 90%, but the luminance of the optotypes and background are the reverse of the first chart. The main features of these charts are as follows. Both contrast sensitivity and spatial frequency are in geometric gradation, which observes the laws of Weber and Fechner. The mean average luminance, (Lmax + Lmin)/2, is constant for all four charts, which follows the concept of contrast sensitivity function (CSF). Charts 1 and 4, which have the same contrasts but different glare backgrounds, measure the glare that is related to the transparency of the refractive media of the eye. Because the charts are rotatable, patient memorization and guessing are minimized. Results compared with those of the conventional visual acuity test and are understandable by patients and eye care practitioners. The charts, which are simple, easy, and require little time, are inexpensive and portable.

Adult↗
PubMed1979

Image formation in fundus cameras.

Imaging in a fundus camera depends more on design of the system than on correction of the first fundus image as formed by the ophthalmoscopic lens. We show here that the designer may use the free parameters of the ophthalmoscopic lens (contact or noncontact) to correct the latter for observation and illumination of the fundus. In both contact and noncontact systems the fundus is illuminated by forming a ring of light on the patient's cornea around a central area (the corneal window) reserved for observation. On the first surface of the crystalline lens, the light also forms a ring which must accomodate the total entrance pupil (TEP) of the observation system in its middle and which is limited on the outside by the patient's iris. The restrictions that result from this situation define the entrance pupil of the bundle of rays that image the marginal point of the retina. The limits of this bundle are imposed by the choice of the angular field of view and by the size of the patient's pupil.

Fundus Oculi↗
PubMed1977

Clinical trials with the Equator-Plus camera.

The Equator-Plus camera can photograph a 148-degree view of the fundus, measured from the nodal point of the eye. We tested this instrument clinically more than 800 times on over 700 eyes. The large field, which is three to four times that of any conventional fundus camera, is achieved by using a special contact lens as the front element in the camera optics. Photographs taken with the Equator-Plus camera can resolve a lesion as small as one-eighth of a disk diameter, if the contrast is good. Protruding tumors, choroidal or retinal detachment, and extensive disease of the choroid and fundus show up well with this technique. We obtained good pictures in 87% of the clinical tests. We have not observed complications of any kind after photography with the Equator-Plus camera.

Adolescent↗
PubMed1976

Effect of the ocular media on the main wavelengths of argon laser emission.

(1) In owl monkeys, where no yellow staining of the media is present, there are clear-cut ophthalmoscopic and histologic differences in the lesions produced by equal amounts of argon green and blue light. (2) The yellow staining of the macula causes differences in lesion intensity and depth when different wavelengths are used for photocoagulation. (3) In humans the influence of age on this difference is apparent.

Adult↗
PubMed1975

Variation of energy density in argon laser photocoagulation.

The power density at the retina provided by presently available laser photocoagulators is subject to variation. Three factors contribute to making the retinal image of the laser beam substantially different from the spot size indicated on the selector of the photocoagulator. These are the operator's variable accommodation, the astigmatism introduced by the contact lens, and the depth of focus of the observation system. The assumption that the same setting on the instrument regularly produces the same power density at the retina will lead to errors in comparing lesions. The safest procedure is to start from the threshold in every location.

Argon↗
PubMed1975

Equator-plus camera.

A new fundus camera can photograph a field extending anterior to the equator (148 degrees from the nodal point). The problems of reflection from the surfaces of the crystalline lens are minimized by fiber optic illumination from carefully chosen locations on the cornea. The camera may be used with monochromatic light of various wavelengths and is equipped with interference filters.

Fiber Optic Technology↗
PubMedDate not supplied

A diagnostic ruler for strabismus and amblyopia.

We designed a diagnostic slide ruler for easier detection of strabismus and amblyopia, both of which begin in childhood. This new instrument makes the Parks three-step test easier to use and faster than other methods in diagnosing isolated cyclovertical muscle paralysis. Furthermore, the slide ruler tests visual acuity with both series letters and single letters. Incorporated into the instrument are Laurence's strabismometer, Haab's pupillometer, occluder, pinhole, and millimeter ruler. A laboratory model is now available, and this slide ruler can assist the ophthalmological practitioner in analyzing three-step test data more rapidly than graphs and computer programs can. This instrument can also diagnose pediatric patients in the early stages of microstrabismus and amblyopia to obtain the best therapeutic results.

Amblyopia↗