GB357931A - Improvements in methods and instruments for measuring the curvature of the cornea - Google Patents
Improvements in methods and instruments for measuring the curvature of the corneaInfo
- Publication number
- GB357931A GB357931A GB7208/31A GB720831A GB357931A GB 357931 A GB357931 A GB 357931A GB 7208/31 A GB7208/31 A GB 7208/31A GB 720831 A GB720831 A GB 720831A GB 357931 A GB357931 A GB 357931A
- Authority
- GB
- United Kingdom
- Prior art keywords
- microscope
- plane
- marks
- planes
- collimators
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B3/00—Apparatus for testing the eyes; Instruments for examining the eyes
- A61B3/10—Objective types, i.e. instruments for examining the eyes independent of the patients' perceptions or reactions
- A61B3/107—Objective types, i.e. instruments for examining the eyes independent of the patients' perceptions or reactions for determining the shape or measuring the curvature of the cornea
Landscapes
- Life Sciences & Earth Sciences (AREA)
- Health & Medical Sciences (AREA)
- Medical Informatics (AREA)
- Biophysics (AREA)
- Ophthalmology & Optometry (AREA)
- Engineering & Computer Science (AREA)
- Biomedical Technology (AREA)
- Heart & Thoracic Surgery (AREA)
- Physics & Mathematics (AREA)
- Molecular Biology (AREA)
- Surgery (AREA)
- Animal Behavior & Ethology (AREA)
- General Health & Medical Sciences (AREA)
- Public Health (AREA)
- Veterinary Medicine (AREA)
- Eye Examination Apparatus (AREA)
Abstract
357,931. Sight testing apparatus. ZEISS, C., [Firm of], Carl-Zeiss-Strasse, Jena, Germany. March 9, 1931, No. 7208. Convention date, March 13, 1930. [Class 97 (i).] In an instrument for determining corneal curvature by measuring the distance between the reflected images produced by the cornea of two test objects arranged in a plane containing the axis of the eye, these images being imaged by an optical observing device, the view of the two test objects is presented to the eye under a constant angle and optical means are provided to separate from the pencil of imaging rays of the observing device two partial ray pencils. The curvature of the cornea is determined from the relative positions of the images of the test objects. The marks are rotatable around the axis of the observation device so that their plane can be made to coincide with a principal section plane of an astigmatic eye. Preferably a second pair of marks is provided on the same observing device, the plane of these marks being at right-angles to that of the first-mentioned marks so that the curvatures of the two principal section planes can be determined at one observation. The instrument shown comprises four collimators 3 mounted on a microscope 14 so that their axes lie in two planes at right-angles to each other and each containing the axis of the microscope. The axes of the collimators intersect that of the microscope at the same point 10. Each collimator contains a lamp 4 and a condenser consisting of two plano-convex lenses 6, 7, the test objects being marked on the plane lens surfaces 8 .. 8<111> furthest from the lamp, which surfaces are in the focal planes of lenses 9. The test marks in the collimators lying in a horizontal plane consist of a cross 29, Fig. 6, having its horizontal line elongated and two spaced horizontal lines 30, 30<1>, Fig. 5, marked with scales 31, 31<1> of radii of curvature and refractive powers respectively. The marks in the other two collimators are similar, Figs. 7 and 8, but arranged vertically. The observing microscope 14 comprises an objective 15 in the focal plane of which is a plate 35 bearing a luminous spot 36 to be observed by the eye 12 under examination. The ocular 16 of the microscope is mounted in a sleeve 17 carrying a plate 18 on which are four radial marks 19, Fig. 11, spaced at 90‹ from each other. The microscope contains a reversing system comprising two plano-convex lenses 20, 21, the plane surface of the lens 20 being formed as a diaphragm having four rectangular apertures 23 .. 23<111>, Fig. 3, behind which are disposed refracting prisms 24 .. 24<111>. The whole assembly of microscope and collimators can be rotated in a bearing 1 about the axis of the microscope, a graduated dial 25 being provided for measuring the angle of rotation. In using the instrument the sleeve 17 is adjusted until the images of the test objects are seen in focus with the lines 19. Then, supposing the eye to be astigmatic and its principal section planes not horizontal and vertical, the whole instrument is turned in the bearing 1 until, as shown in Fig. 11, the longer lines of the crosses 29, 32 bisect the spaces between the lines 30, 301 and 33, 331 respectively. The meridians of the principal planes are then obtained from the graduations 27 on the dial 25, and the radii of curvature and refractive powers in these planes from the positions of the shorter lines of the crosses in relation to the scales 31, 31<1> and 34, 34<1>.
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE357931X | 1930-03-13 |
Publications (1)
Publication Number | Publication Date |
---|---|
GB357931A true GB357931A (en) | 1931-10-01 |
Family
ID=6290699
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB7208/31A Expired GB357931A (en) | 1930-03-13 | 1931-03-09 | Improvements in methods and instruments for measuring the curvature of the cornea |
Country Status (1)
Country | Link |
---|---|
GB (1) | GB357931A (en) |
-
1931
- 1931-03-09 GB GB7208/31A patent/GB357931A/en not_active Expired
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