WO2006013579A1

WO2006013579A1 - A retinal or fundus camera

Info

Publication number: WO2006013579A1
Application number: PCT/IN2005/000224
Authority: WO
Inventors: Satish Chander Gupta
Original assignee: Satish Chander Gupta
Priority date: 2004-08-02
Filing date: 2005-06-30
Publication date: 2006-02-09
Also published as: WO2006013579A8

Abstract

A retinal or fundus camera comprising: (i) a light source (1) disposed within the camera (1) and away from the eye of a patient. (ii) a first lens (L1) within the camera for focusing the light from said light source onto the retina and providing a wide field retinal image. (iii) a second lens (L2) for receiving said image and causing a magnification of the retinal image; (iv) a digital camera for recording the image.

Description

"A RETINAL OR FUNDUS CAMERA"

FIELD OF INVENTION

This invention relates to a retinal or fundus camera. The retinal or fundus camera of the present invention is adapted to provide a photo documentation of the retina of the eye.

BACKGROUND OF INVENTION

There are many diseases which affect the retina. Normally, an examination of the retina is effected by an ophthalmoscope. The basic requirement of an ophthalmoscope, whether it be direct or indirect, is to illuminate the retina, which can then be focused onto the eye of an examining doctor. The focusing of the illuminated retina is effected by a system of lenses provided in the ophthalmoscope. An ophthalmoscope may be a direct or indirect ophthalmoscope. With a direct ophthalmoscope, the images are erect, magnified and virtual. In direct ophthalmoscope, the images formed are inverted, small or less magnified and real. A disadvantage associated with direct ophthalmoscope is that it does not have a wide field.

Fundus or retinal cameras presently known in the art have a circular source of light besides the lens system. A disadvantage associated with such a camera is that the source of light touches the periphery of the cornea. In another known camera, the source of light comprises a u.v. source which touches the globe of the eye. Both of such known cameras are contact cameras having the distinct advantage of a wide field of view of the retina. However, a disadvantage associated with such known cameras is that of the contact between the eye and the light source. Such a contact could result in transmission of infection and chances of causing injury to the eye. Yet another disadvantage is that the magnification is small. In order to obviate the aforesaid disadvantage, it is known to provide a direct ophthalmoscope fundus or retinal camera. In such a known camera, and in order to improve the quality of the images and to avoid reflexes, the optical system incorporated in the camera is complex and bulky. Such cameras are heavy equipment and cannot be easily moved after installation, hence cannot be used for field work. Further such non contact fundus cameras have a field of view ranging from 15° to 60°. This is inadequate for photographing the periphery of retina, which is essential for recording the changes of retinopathy of prematurity.

U.S. Patent No. 4,810,084 describes a retinal camera having an illumination source and an optical system for projecting the light onto a retina under examination. The camera further comprises a filter means disposed substantially conjugate to the retina of the eye so as to illuminate the eye. The filter means comprise at least one filter member with a disc shaped transmitting base plates, a first and second circular semi-transmitting surface. Such a camera had a complicated illumination optical means.

OBJECT OF THE INVENTION

An object of this invention is to propose a retinal or fundus camera which is portable and no longer bulky.

Another object of this invention is to propose a retinal or fundus camera, which has a wide field.

Still another objection of this invention is to propose a retinal or fundus camera, which no longer contacts the eye.

Yet another object of this invention is to propose a retinal or fundus camera, which has a simple optical system. A further object of this invention is to propose a retinal or fundus camera, which is efficient.

DESCRIPTION OF INVENTION

According to this invention there is provided a retinal or fundus camera comprising:

(i) a light source disposed within the camera and away from the eye of a patient.

(ii) a first lens within the camera for focusing the light from said light source onto the

retina and providing a wide field retinal image,

(iii) a second lens for receiving said image and causing a magnification of the retinal image;

(iv) a digital camera for recording the image.

In accordance with this invention the first lens could have a power of 60 to 90 dioptres, as greater the power of the lens, larger is the field of view. Further, such a lens comprises a biconvex aspherical lens. The second lens has a power less than that of said first lens, such as 20 to 30 dioptres, so as to provide a greater magnification of the retinal image and to act as a close up lens for the camera. Such a lens comprises also a biconvex aspherical lens.

Thus, according to this invention, the lens system has a varying power of 20 to 90 D. As the power of the lens increases, the filed becomes a wider but magnification less. Thus, the first lens should have a higher power such as 60 to 90D, so that the field of view increases. However, the power of said first lens should not be higher than that 90 dioptres, as the lens would then be too close to the eye ball under examination. A magnification of the image is achieved by the second lens. The distance between said first and second lens is the sum of the focal length of the first and second lens.

DESCRIPTION WITH REFERENCE TO DRAWINGS

Further objects and advantages of this invention will be more apparent from the ensuing description when read in conjunction with the accompanying drawings and wherein ;

Fig 1. shows the camera of the present invention; and Fig 2. shows the optical system.

Referring to the drawings, the camera 1 comprises a housing 2 extending into a tubular extension 3. A power source since a battery 4 is disposed within housing 1. Housing 2 has a digital camera back plate 5 with a card 6 disposed therein.

Reference is made in particular to fig. 2. The camera has an optical system to comprise a source light S₁ adapted to be connected to the power source 4. A condensing lens which is a piano convex lens L₃ is provided in the proximity of light source S₁ so as to transmit the light onto a mirror M₁. Light from mirror M₁ is focused onto the retina of a patient through lens L₁. As described hereinabove, lens L₁ has a high power such as 60 to 90 dioptres, so as to provide a wide field of view for example, upto 110° Lens L₁ receives the image of the retina at its focal point F₁, which is then transmitted to a second lens L₂ having a power less than that of lens L₁. Thus, lens L₂ acts as a magnifying lens and a close up lens for the camera. The image is at the focal length of lens L₂, which is greater than the focal length of lens L₁. The light from mirror M1 is diposed such that it is almost coaxial with the receiving optics.

Claims

WE CLAIM:

1. A retinal or fundus camera comprising :

(i) a light source disposed within me camera and away from me eye of a patient, (ii) a first lens within the camera for focusing the light from said light source onto the retina end providing a wide field retinal image.

(iii) a second lens for receiving said image and causing a magnification of the retinal image; (iv) a digital camera for recording the image.

2. A retinal or fundus camera as claimed in claim 1 wherein the first lens has a power greater than said second lens,

3. A retinal or fundus camera as claimed in claim 1 wherein a condensing lens in the proximity of said light source.

4. A retinal or fundus camera as claimed in claim 3 wherein said first lens is a biconvex aspherical lens.

5. A retinal or fundus camera as claimed in claim 1 which said second lens is a biconvex aspherical lens.

6. A retinal or fundus camera as claimed in claim 1 wherein the focal length of said lens is greater than that of said first lens.

7. A retinal or fundus camera as claimed in claim 1 wherein the distance between said first and second lens is the sum of the focal length of said first and second lens.

8. A retinal or fundus camera as claimed in claim 1 wherein the light source includes a condensing lens and a mirror the light reflected from said mirror being substantially coaxial with that of the optics.