2. DO.pptx opthalmic diagnostic instruments

Do it's diagnostic procedure used in clinical practice

1. Direct ophthalmoscope 1 1 12/29/2024

2. 12/29/2024 2 Definition Ophthalmoscope is an instrument that enables us to examine the posterior segment of the eye and fundus, as well as allowing a view of the anterior segment in general diffuse illumination. Direct ophthalmoscope is monocular & hand held

3. Parts of DO Head Handle 12/29/2024 3

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5. Optics: – Illumination system Magnifier Hyperopes myopes Observation system Lens wheel Apertures 6 5 12/29/2024

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7. 12/29/2024 7 Principle of direct ophthalmoscope Light rays emerging from an illuminated point of the patient’s retina leave the eye as a parallel pencil of light if the eye is emmetropic. The parallel pencil of light enters the emmetropic observer’s eye and is brought to a point focus on the retina.

8. Hold the instrument closer to the examiner’s and to the patient's eye If the patient has spectacles, it needs to be removed 12/29/2024 8

9. If the light source & the observer aren't aligned optically, the observer views a part of the fundus that is not illuminated. 12/29/2024 9 The design of the modern ophthalmoscope has solved this problem by incorporating a pre- centred bulb which projects a bright homogenous patch of light onto the patient’s fundus.

10. 12/29/2024 10 The design of the ophthalmoscope varies between models & manufacturers, but modern ophthalmoscopes usually consists of small low- voltage bulb whose filament is imaged on an inclined mirror or reflecting prism

11. 12/29/2024 11 Operation procedures Selection of Viewing Lenses Turn the diopter disc counter clockwise for convex (plus) lenses, which are printed in black: 0, +1, +2, +3, +4, +5, +6, +8, +10, +12, +16, +20D. Turn the diopters disc clockwise for concave (minus) lenses, which are printed in red: 0, - 1, - 2, - 3, - 4, - 5, - 6, - 8, - 10, - 16, - 20, - 25, - 35D. The power display is illuminated for ease of reading in a dim room.

12. 12/29/2024 12 If either the patient or the observer has an ametropia, it can be corrected by interposing a lens in the ophthalmoscope of a power which is the algebraic sum of the two. For example, if the patient is -3.00Ds myopic a –3.00D lens will need be needed in the ophthalmoscope. If both the subject and observer are 2Ds hypermetropic each a +4.00D lens is required. In the case of astigmatisim we need to consider the BVS

13. 12/29/2024 13 Selection of Aperture T yp e & filters Large Spot: used for checking the fundus with opaque media, such as cataracts; in dilated examination. Small Spot: used for general undilated fundus examination Slit: used for examining retinal elevations & depressions Red- free Filter: used to examine blood vessels & bleeding Fixation star: a cross for detection of eccentric fixation Polaroid filter: reduces unwanted reflection

14. 12/29/2024 14 Field of View The FOV(how much you see the fundus) depends upon: the size of the subject’s pupil diameter the size of the sight hole aperture or observers pupil the distance of the patient from the observer the Rx (refractive error) of the patient

15. The field of view of the patient’s retina is increased by: an enlargement of the patient’s and observer’s pupils by decreasing the distance between the observer and the patient. Limited FOV in the direct method. Peripheral pencils of light do not reach the observer's pupil 12/29/2024 15

16. 12/29/2024 16 Magnification The magnification M under which the image is seen through the ophthalmoscope is given by: M = K 4 Where K is the refractive power of the eye. Thus, for the standard reduced eye, K = 60, M = 15 Generally, examination of a myopic patient increases the magnification & reduces the FOV whereas examination of a hypermetropic patient decreases the magnification & enlarges the field of view.

17. Cont’d… Myopic patients have extra plus power - ophthalmoscope must carry a negative lens Galilean telescope effect - fundus details are seen larger Reduce field of vision In hyperopic or aphakic patients - ophthalmoscope must carry positive lens Reverse Galilean telescope effect – fundus details appear smaller Larger field of vision 12/29/2024 17

18. 12/29/2024 18 Clinical Procedure It is a routine procedure that can be done for every patient No contra- indication Monocular (no 3D view) Used to Evaluate media opacities To detect posterior segment problems Grossly detect anterior segment defects

19. 12/29/2024 19 How to do ophthalmoscopy Set up Remove spectacles (yours and the patient’s) Explain what you are doing Raise the examination chair so you are bending slightly Dim the room lighting Hold the ophthalmoscope in your right hand in front of your RE for patient’s RE, swap all to the left side for LE Hold as close to your eye as possible Tilt ophthalmoscope to about 20deg to avoid bumping into the patient’s nose

20. How to do ophthalmoscopy Performed with the eye that corresponds to the eye being examined Focused by twirling the dial for the With a dilated pupil patient is instructed to stare into the distance The focusing lens is set at (or the examiner's refractive error) The patient's red reflex is checked from a distance of 2 feet Check opacity in the optical media –dark shadow The light beam must remain centered within the pupil –to avoid 21 12/29/2024 20

21. Cont’d… Viewing ocular media Set the ophthalmoscope lens to +10D The patient’s eye will be in focus at 10cm away if you are emmetropic Observe red reflex Look for media opacities Cataracts Corneal scars Large floaters Anterior segment at all 12/29/2024 21 21

22. Cont’d… Proper position for central fundus viewing Right eye to right eye Left eye to left eye Come closer and don’t rub noses… 12/29/2024 22 22

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24. Cont’d… Proper position for peripheral fundus viewing – Move sideways and up down 25 12/29/2024 24

25. 12/29/2024 25 In short… Examination in dark room. Patient in sitting position. Examine with both eyes open. Start a little bit far away with + 10D lens- examine red reflex for opacities. Move from side to side to locate the position of opacities Slowly get closer and reduce plus lens. Locate the disc and examine it. Follow all major blood vessels. Ask patient to look into 8 cardinal position to examine periphery.

26. 12/29/2024 26 Recording Be systematic Start at optic disc & work radially Observe: Optic disc: C/D ratio Vessels: course & caliber, AV ratio, light reflex, crossings/banking Macula Peripheral fundus

27. 12/29/2024 27 Recording The retinal drawing is made inside a circle centered on the fovea – Shows the relative positions of the optic disc, major retinal blood vessels, and ora serrate – Record of the examination is kept by Standard preprinted fundus charts , or vitreoretinalcharts

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29. 12/29/2024 29 Viewing the Optic Nerve Head Observe: Size Shape Color Margins Cup to disc ratio (C/D) horiz & Vert Blood Vessel Evaluation Observe: Vessel diameter Shape/tortuosity Color Crossings Light reflex Artery/Vein (A/V) ratio

30. Macula 12/29/2024 30

31. Vitreoretinal drawing chart 12/29/2024 31

32. Optic disc drawing chart 12/29/2024 32

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34. 12/29/2024 34 Care and maintenance Do not use this instrument around heat or open flame. Keep away from dust and moisture. Use only the fuse specified in the manual. Use only the power cable supplied with the instrument. Turn off the main power before changing the and bulb. In case of trouble with the instrument, first consult the trouble shooting guide.

35. 12/29/2024 35 Ensure that the ophthalmoscope is off when not in use. To prolong the life of the bulb, do not use at full intensity on a freshly charged battery. The ophthalmoscope should remain in a clean environment. If not to be used for a prolonged period of time, it is recommended to be stored in the protective case. The handle bottom should remain clean at all times to ensure normal charging.