# US 5,347,328 A · Apparatus for measuring an intraocular length between anterior and posterior portions of an eye > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,347,328 A - Document ID: US5347328A - Status: Granted - Kind: A - Application number: 07/872,266 - Filed: 1992-04-21 - Granted: 1994-09-13 - Earliest claimed: 1991-04-22 - Assignees: Topcon Corporation - Inventors: Akihiko Sekine; Funio Ohtomo - Web page: https://patentgrep.com/patent/US5347328A ## CPC - A61B 3/1005: {for measuring distances inside the eye, e.g. thickness of the cornea (A61B3/11 takes precedence)} - G01B 9/02004: using frequency scans - G01B 9/0207: {Error reduction by correction of the measurement signal based on independently determined error sources, e.g. using a reference interferometer} - G01B 2290/60: Reference interferometer, i.e. additional interferometer not interacting with object - A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D) - G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS ## Abstract An apparatus for measuring an eye axial length includes a measuring optical system for projecting laser beam onto an eye and making interference between light reflected by the cornea of the eye and light reflected by the retina of the eye. The measuring optical system includes beam splitting means for splitting the beams of light reflected by the cornea and the retina each into two each for different optical systems, a cornea reflected light receiving optical system for receiving the light reflected by the cornea, a retina reflected light receiving optical system for receiving the light reflected by the retina, and an interference light receiving optical system for reuniting each reflected light at the substantially identical wave front and receiving interference light. ## Claims ### Claim 1 An apparatus for measuring an intraocular length between anterior and posterior positions of a living eye, comprising: a laser source to emit a laser beam of light, having variable wavelengths, onto said eye; and means for measuring interference between light reflected by the anterior portion of said eye and light reflected by the posterior portion of said eye, the intraocular length of said eye being measured according to said interference, said measuring interference means comprising: light splitting means for separating said light reflected by the anterior portion and said light reflected by the posterior portion; an anterior portion reflected light optical system for receiving said light reflected by the anterior portion from said light splitting means; a posterior portion reflected light optical system for receiving said light reflected by the posterior portion from said light splitting means; and interference light receiving optical system for combining an output from said anterior portion reflected light optical system with an output from said posterior portion reflected light optical system at a substantially identical wave front to produce and receive interference light for measurement. ### Claim 2 (depends on 1) An apparatus for measuring an intraocular length between anterior and posterior portions of a living eye according to claim 1, wherein said anterior portion is a cornea and said posterior portion is a retina. ### Claim 3 (depends on 2) An apparatus for measuring an intraocular length between anterior and posterior portions of a living eye according to claim 2, further comprising optical path length correcting means for equalizing an optical path length of said anterior portion reflected light optical system with an optical path length of said posterior portion reflected light optical system, said optical path length correcting means disposed in at least one of said anterior portion reflected light optical system and said posterior portion reflected light optical system. ### Claim 4 (depends on 3) An apparatus for measuring an intraocular length between anterior and posterior portions of a living eye according to claim 3, wherein said optical path length correcting means comprises an optical path length compensating plate. ### Claim 5 (depends on 3) An apparatus for measuring an intraocular length between anterior and posterior portions of a living eye according to claim 3, wherein said optical path length correcting means comprises a movable reflecting mirror. ### Claim 6 (depends on 2) An apparatus for measuring an intraocular length between anterior and posterior portions of living eye according to claim 2, wherein said anterior portion reflected light optical system includes anterior portion reflected light selecting means for selecting only light reflected by the anterior portion and said posterior portion reflected light optical system includes posterior portion reflected light selecting means for selecting only light reflected by the posterior portion. ### Claim 7 An apparatus for measuring an intraocular length between anterior and posterior portions of living eye, comprising: a laser source to emit a laser beam of light, having variable wavelengths, onto said eye; and means for measuring interference between light reflected by said anterior portion of said eye and light reflected by said posterior portion of said eye, the intraocular length being measured according to said interference, said measuring interference means comprising: a light receiving optical system for receiving interference light; an anterior portion illuminating optical system for projecting said laser beam of light onto the anterior portion and guiding light reflected by the anterior portion to said light receiving optical system; and a posterior portion illuminating optical system for projecting said laser beam of light onto the posterior portion and guiding light reflected by the posterior portion to said light receiving optical system; said anterior portion illuminating optical system and said posterior portion illuminating optical system being arranged so that the reflected light from the anterior and posterior portions interferes with each other at a substantially identical wave front and is guided to said light receiving optical system. ### Claim 8 (depends on 7) An apparatus for measuring an intraocular length between anterior and posterior portions of a living eye according to claim 7, wherein said anterior portion is a cornea and said posterior portion is a retina. ### Claim 9 (depends on 8) An apparatus for measuring an intraocular length between anterior and posterior portions of a living eye according to claim 8, further comprising optical path length correcting means for equalizing an optical path length of said anterior portion illuminating optical system with an optical path length of said posterior portion illuminating optical system, said optical path length correcting means disposed in at least one of said anterior portion illuminating optical system and said posterior portion illuminating optical system. ### Claim 10 (depends on 9) An apparatus for measuring an intraocular length between anterior and posterior portions of a living eye according to claim 9, wherein said optical path length correcting means comprises an optical path length compensating plate. ### Claim 11 (depends on 9) An apparatus for measuring an intraocular length between anterior and posterior portions of a living eye according to claim 9, wherein said optical path length correcting means comprises a movable reflecting mirror. ### Claim 12 (depends on 8) An apparatus for measuring an intraocular length between anterior and posterior portions of a living eye according to claim 8, wherein said anterior portion illuminating optical system includes anterior portion reflected light selecting means for selecting only light reflected by the anterior portion and said posterior portion illuminating optical system includes posterior portion reflected light selecting means for selecting only light reflected by the posterior portion.