Ophthalmoscopy

It tells about Ophthalmoscopy

1. U.P UNIVERSITY OF MEDICAL SCIENCE SALAL MOHAMMAD B.OPTOM 2 ND YEAR

2. OPHTHALMOSCOPY

3. CONTENTS Introduction History Principle Optics Types Distant Direct Ophthalmoscopy ( DDO ) Direct Ophthalmoscopy ( DO ) Indirect Ophthalmoscopy ( IDO ) Technique

4. INTRODUCTION Ophthalmoscopy is a clinical examination of the interior of eye by means of an ophthalmoscope. It is primarily done to assess the state of fundus and detect the opacities of ocular media. It is done as part of an eye examination and may be done as part of a routine physical examination.

5. HISTORY The ophthalmoscope was invented by Babbage ,1848. In 1850,Hermann von Helmholz reinvented the ophhalmoscope and revolutionized ophthalmoscopy . Helmholtz could place his eye in the path of the light rays entering and leaving the patient’s eye ,by looking through the source of light ,thus allowing the patient’s retina to be seen.

6. PRINCIPLE Helmholtz instrument operated by using a mirror to shine a beam of light into the eye. The observer would look through a tiny aperature (opening ) in the mirror. Helmholtz found that looking through the lens into the back of the eye only produced a red reflection. By attaching a condenser lens he obtained a clearer inverted image ,which was then magnified five times. He c/d this combination of a mirror and condenser lens an indirect ophthalmoscope.

7. OPTICS The image is erect ,virtual and about 15 times magnified in emmetropes . Technique – Should be performed in a semidark room with the patient seated and looking straight ahead ,while the observer standing or seated slightly over to the side of the eye to be examined by the observer with his/her right eye and left with the left eye. The observer should reflect beam of light from the ophthalmoscope into patient pupil .once the red reflex is seen the observer should move as close to the patient eye as possible.

8. Once the retina is focused the details should be examined systematically starting from disc blood vessels ,the four quadrant of the general background and the macula.

9. TYPES There are 3 types of ophthalmoscopy : Distant Direct Ophthalmoscopy Direct Ophthalmoscopy Indirect Ophthalmoscopy

10. Distant Direct Ophthalmoscopy ( DDO ) It should be performed routinely before the direct ophthalmoscope ,as it gives a lot of useful information . It can be performed with the help of a self illuminated ophthalmoscope or a simple plane mirror with a hole in the centre. PROCDURE – The light is thrown into the patient’s eye –with the patient sitting in semidark room –from a distance of 20-25 cm and the features of the red glow in the pupillary area are noted.

11. APPLICATION To diagnose opacities in the refractive media. To differentiate between a mole and hole of the iris. To recognize detached retina or a tumour arising from the fundus .

12. Direct Ophthalmoscopy ( DO ) It is the most commonly practised method for routine fundus examination. It is done as close to the patient as possible .

13. OPTICS The modern DO works on the basic optical principle of glass plate ophthalmoscope introduced by von Helmholtz . A convergent beam of light is reflected into the patient’s pupil .

14. The emergent rays from any point on the patient’s fundus reach the observer’s retina through the viewing hole in the ophthalmoscope. The emergent rays from the patient’s eye are parallel and brought to focus on the retina of the emmetropic observer when accommodation is relaxed. In hypermetropic patient ,the emergent ray from the retina will be divergent,and thus can be brought to focus on the obsever’s retina ,if latter accommodates or by the help of convex lens.

15. In myopic patient ,the emergent ray from the retina will be convergent,and thus can be brought to focus on the obsever’s retina by the help of concave lens.

16. Characterstics of Image – Erect ,virtual 14-15 times magnified in emmetropes ( more in myopes and less in hypermetropes ). 50-70 % fundus seen Field of vision : smaller the sight hole better the field of vision. Directly proportional to the size of pupil of observed eye and Axial length of the eyeball. Inversely proportional to distance between observed and observer’s eye.

17. TECHNIQUE In semidark room with the patient seated and looking straight ahead ,while the observer standing or seated slightly over to the side of the eye to be examined. The patient eye should be examined by the observer with his/her Rt. eye and left with the left. The observer should reflect beam of the light from the ophthalmoscope into patient’s pupil. Once the red reflex is seen ,the observer should move as close to the patient’s eye as possible.

18. DO should then be focused by twirling the dial for the Reskoss disc ,which has several plus and minus powered lasers. Once the retina is focused ,the details should be examined systematically starting from disc ,blood vessels ,the four quadrants of the general background and the macula by utilizing the various illumination option and aperatures provided in the DO.

19. Indirect Ophthalmoscopy ( IDO ) IDO introduced by Nagel ,1864, is now a very popular method for examination of the post. Segment. There are two types : Monocular Binocular

20. Monocular Indirect Ophthalmoscopy Structural features : Illumination rheostat at its base. Focussing lever for image refinement. Filter dial with red free and yellow filter. Forhead rest for steady proper observer head positioning . Iris diaphragm lever to adjust the illumination beam diameter.

21. OPTICS – An internal lens system re-inverts the initially inverted image to a real erect one,which is then magnified .this image is focusable using the focusing lever/eyepiece system. Extent of view- Vitreous base views also. Peripheral equatorial region.

22. Advantages : Increased field of view. Erect ,real image similar to DO> Disadvantages : Lack of stereopsis Limited illumination Fixed magnification Fair to good resolution

23. Binocular Indirect Ophthalmoscopy In this modern era ,IDO is of great general use in ophthalmology and requires much effort and practice by the ant. As well as the post. Segment surgeons. OPTICS – The principle IDO is to make the eye highly myopic by placing a strong convex lens in front of patient’s eye so that the emergent rays from an area of the fundus are brought to focus as a real inverted image b/w the lens and the observer’s eye. Field of Illumination : More in myopia and less in hypermetropia .

24. Image Formation Image formation in emmetropia

25. Image formation in hypermetropia

26. Image formation in myopia

27. Characterstics of the Image The image formed in IDO is real ,inverted and magnified. Magnification of image D/o the dioptric power of the convex lens , positon of the lens in relation to the eyeball and refractive state of the eyeball. The important characterstics of the image formed by an IDO are as follows: Relative position of images formed in emmetropic , myopic and hypermetropic eye. Size of the image vis -a vis refractive condition of the eye. Image magnification in IDO.

28. PREREQUISITES : Indirect Ophthalmoscope ( IDO ). Dark room Convex lens ( +14D/+20D/+28D/+30D.) Pupils of the patient’s should be dilated Couch

29. TECHNIQUE The procedure is explained to patient. He/she is made to lie in the supine position,with one pillow on a couch/bed. Instructed to both eyes open. The examiner throws the light into the patient’s eye from an arm’s distance.

30. Binocular ophthalmoscope with head band or that mounted on the spectacles frame is employed most frequently. Keeping the eyes on the reflex ,the examiner then interpose the condensing. lens (+20D routinely),in the path of beam of light close to patient’s eye ,and then slowly moves the lens away from the eye until the image of the retina is clearly seen.

31. He/she has to stand opposite the clock hour position to be examined .Exp-to examine inf. Quadrant (around 6’o clock meridian ),the examiner stands towards patient’s head (12’o clock meridian) and so on. By asking the patient’s to look in extreme gaze ,and using scleral indenter the whole peripheral retina upto ora serrata can be examined.

32. Difficulties The technique is difficult and can be mastered by hours of practice. Reflexes from the corneal surface can be decreased by holding the condensing lens at a distance equal to its focal length from the ant. Focus of the eye. Formation of reflexes by the two surfaces of convex lens can be eliminated by slightly tilting the lens and the use of aspheric lens.

33. Advantages Larger field of retina is visible. Lesser distortion of the image of the retina. Easier to examine,if the patient’s eye movement are present and with high spherical or astigmatic error. Easy visualization of the retina ant. to the equator. It gives a 3D stereoscopic view of the retina. It is helpful in hazy media bcz of its bright light and optical property.

34. Disadvantages Magnification in IDO is 5 times. IDO is impossible with small pupil. The patient is usually more uncomfortable with the intense light of IDO and with scleral indentation. The procedure is more cumbersome. Reflex sneezing can occur on exposure to bright light.

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