Patent Publication Number: US-2021186325-A1

Title: System and method for a portable eye examination camera

Description:
CROSS-REFERENCE 
     The present application is a continuation of U.S. application Ser. No. 16/152,294, filed on Oct. 4, 2018, which is a continuation of U.S. application Ser. No. 15/076,824, filed on Mar. 22, 2016, now issued U.S. Pat. No. 10,105,051, which claims benefit of U.S. Provisional Application Ser. No. 62/136,609, entitled “PORTABLE INDIRECT OPHTHALMOSCOPY BASED FUNDUS CAMERA for ROP SCREENING”, filed on Mar. 22, 2015, which are hereby incorporated by reference in their entirety. 
    
    
     DESCRIPTION WITH REFERENCE TO DRAWINGS 
     For a more complete understanding of the present invention, including its features and advantages, reference is now made to the detailed description of the invention taken in conjunction with the accompanying drawing in which: 
       FIG. 1  shows the various components of the present invention; and 
       FIG. 2  shows another illustrations of the optical system of the present invention. 
    
    
     DETAILED DESCRIPTION 
     While the making and using of various embodiments of the present invention are discussed in detail below, it should be appreciated that the present invention provides many applicable inventive concepts that may be embodied in a wide variety of specific contexts. The specific embodiments discussed herein are merely illustrative of specific ways to make and use the invention and do not delimit the scope of the invention. 
     There are many diseases that 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. With a direct ophthalmoscope, the images are erect, magnified and virtual. In Indirect 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 which get a wide field of view, 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 an Ultra Violet 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. 
     Another method currently used in the field includes a retinal camera having an illumination source and an optical system for projecting the light onto a retina under examination. The camera further includes a filter means disposed substantially conjugate to the retina of the eye so as to illuminate the eye. The filter means includes at least one filter member with a disc shaped transmitting base plates, a first and second circular semi-transmitting surface. However, this system&#39;s a camera has a complicated illumination optical means. 
     In contrast, the present invention improves several aspects of the current systems and method used in field. One embodiment of the present invention relates to a retinal or fundus camera. Specifically, the retinal or fundus camera of the present embodiment is adapted to provide a photo documentation of the retina of the eye. 
     One aspect of this invention includes a retinal or fundus camera that is portable. 
     Another aspect of this invention includes a retinal or fundus camera, which has a wide field. 
     Another aspect of this invention includes a retinal or fundus camera, which does not contact the eye. 
     Another aspect of the invention includes a retinal camera, which can take pictures of retina in un-dilated pupil (4 to 5 mm size). 
     Another aspect of this invention includes a retinal or fundus camera, which has a simple optical system. 
     Another aspect of this invention includes a retinal or fundus camera, which is efficient. 
     One embodiment of the present invention includes a retinal or fundus camera which includes: a light source (e.g. Light Emitting Diode (LED)) within the camera and placed close to the camera lens and away from the eye of a patient to illuminate the retina of the patient&#39;s eye. The embodiment also includes: an Infra-Red LED within the camera and placed close to the camera lens and away from the eye of a patient to illuminate the retina of the patient&#39;s eye, without initiating the light reflex—thus keeping the pupil dilated for photographing the retina when a white LED flashes. In addition, the embodiment also includes: a 60 to 90 Diopter lens for receiving the reflection light from the retina and forming a real and magnified image of the retina. Moreover, the embodiment also includes: a 20 Diopter lens in front of the camera lens to provide further magnification of the retinal image. The embodiment further includes a portable computing device for recording the image. 
     In accordance with this invention, the first lens could have a high power of (e.g. such as 60 to 90) diopters—the greater the power of the lens translates to a larger the field of view. Further, such a lens comprises a biconvex aspherical lens. In this embodiment, the second lens has a power less than that of the first lens (e.g. such as 20 to 30 diopters), 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 is usually a biconvex achromatic lens. 
     Thus, according to the present embodiment, the lens system has a varying power of (e.g. such as 20 to 90) Diopters. As the power of the lens increases, the field becomes wider but with less magnification. Thus, in this embodiment, the first lens has a higher power (e.g. such as 60 to 90 D), so that the field of view increases. However, the power of the first lens in this embodiment is not higher than 90 diopters, as the lens would then be too close to the eyeball under examination. Conversely, a magnification of the image is achieved by the second lens in this embodiment. Accordingly, the distance between the first and second lens is the sum of the focal length of the first and second lens. 
     Now referring to  FIGS. 1 and 2 , Housing  100  includes of a re-tractable metallic tubular extension  104  that holds a 60 Diopter Lens  122  and 20 Diopter Lens  120  and a plastic casing  108 . A light source  106 , an Infra-Red light source  118  and Selector switch  114  and a power source battery  110  is disposed within the plastic casing  108 . 
     In addition, the embodiment also includes three polarizing filters  300 . A first filter is placed in front of the white light LED  106  and a second one is placed in front of 20 D magnifying lens  120 . A third filter is also placed in front of the IR LED light source  118  similarly to the one placed in front of the white light LED source  106 . Moreover, the second filter is placed at 90 degree polarity in respect to the first and third filters. 
     In addition, Housing  102 , in this embodiment, is a digital camera combined in a cell phone  116 . Moreover, the fundus camera has an optical system including of LED light source  106  and Infra-Red light source  118  connected to the power source battery  110 . Furthermore, the Selector Switch  114  allows switching between LED light source  106  and Infra-Red LED  118 . The light from either light source  106 ,  118  is focused onto a retina  222  of a patient through lens  122 . As described herein above, this lens  122  has a high power such as 60 to 90 diopters, so as to provide a wide field of view for example, up to 110o. Further, lens  122  receives the image of the retina  222  at its focal point F 1 , which is then transmitted to a second lens  120  having a power less than that of lens  122 . Thus, lens  120  acts as a magnifying lens and a close up lens for the camera. Accordingly, the image is at the focal length of lens  120 , which is greater than the focal length of lens  122 . 
     Moreover, the light from light source  106  or  118  is disposed such that it is almost coaxial with the receiving optics. 
     The above embodiments show using an alternative light source other than using the light source (e.g. normal flash light used in most digital cameras) within, or adjacent to, the cell phone. These unique aspect allows near alignment of projected light with the optical axis off the lenses. In addition, the present invention contemplates using any other portable computing device as a controller for the optical system, and not restricted to just a digital camera or cell phone. Further, although this embodiment shows a somewhat singular tube, the present invention is not restricted to a particular version of a tube and includes any type of retracting metallic tube. 
     Although this invention has been described with reference to an illustrative embodiment, this description is not intended to limit the scope of the invention. Various modifications and combinations of the illustrative embodiments as well as other embodiments of the invention will be apparent to persons skilled in the art upon reference to the description. It is therefore intended that the appended claims accomplish any such modifications or embodiments.