Diabetic retinopathy screening NSF-based training

1. Diabetic retinopathy screening NSF-based training Anatomy and physiology Tunde Peto Head of Reading Centre

2. Anatomy and physiology of the normal human eye Key issues for discussion • Review the gross anatomical structures within and related to the eyeball and discuss their basic function • Review the basic physiology of refraction and vision Learning outcome • Identify the different structures of the eye and discuss their basic function • Identify different anatomical structures on teaching slides

3. Basic Science in relation to eye disease: the normal retina and vision Key issues for discussion • The normal anatomy of the retina • Photoreceptors and their biochemistry • Physiology of vision including colour vision Learning outcome • Identify normal retinal structure on teaching slides

4. Vision • Reflected light translated into mental image • Pupil limits light, lens focuses light • Retinal rods and cones are photoreceptors Figure 10-36: Photoreceptors in the fovea

5. Photoreceptors • Rods – monochromatic, provide night vision: most numerous in periphery, sees all shades of grey and white; see in dark and around us • Peripheral changes might not affect the vision at all • Laser treatment and retinal detachment might result in visual field loss • Cones – red, green, & blue; color & details, most numerous in macula; you need very few for good vision!

6. Photoreception and Local Integration Figure 10-35: ANATOMY SUMMARY: The Retina

7. Retina: More Detail Figure 10-38: Photoreceptors: rods and cones

8. Vision: Integration of Signals to Perception • Bipolar • Ganglion • Movement • Color • Optic nerve • Optic chiasm • Optic tract • Thalamus • Visual cortex Figure 10-29b, c: Neural pathways for vision and the papillary reflex

9. The aging retina: Age Related Maculopathy (ARM) and Macula Degeneration (AMD) Key issues for discussion • Normal changes in the aging retina • Abnormal changes in the aging retina • The constituents of drusen • Geographic atrophy • Neovascular AMD Learning outcome • Identify age related changes in the retina • Identify and discuss different types of drusen • Identify geographic atrophy • Identify and discuss the main features of neovascular AMD

10. Hard drusen (<63 mikron)

11. Normal SLO image

12. Hard and intermediate soft drusen (63-125 mikron)

13. Large soft Drusen on the posterior pole Watch it developing over the years

14. 2 years later

15. 5 years later

16. 7 years later

17. 10 years later: some areas atrophied

18. Geographic Atrophy

19. Neovascular membrane at the fovea

20. Neovascular membrane at the fovea

21. FFA of the neovascular membranes: R eye: occult, L eye classic membrane

22. Right eye: occult membrane

23. Left eye: classic membrane

24. Fibrovascular scar and secondary atrophy

25. Neovascular membrane on SLO imaging

26. Pigment epithelial detachment: colour image

27. Pigment epithelial detachment on FFA

28. Pigment epithelial detachment: SLO image

29. Vascular occlusion Key issues for discussion • Learn normal vasculature of the eye • Discuss most common systemic causes of vascular problems in the eye • Discuss vein occlusion • Discuss arterial occlusion • Discuss clinical implications of these diseases Learning outcome • Identify normal and abnormal vascular structures in the eye on teaching slides • Identify strategies to deal with these diseases

30. Central retinal vein occlusion: Introduction • dilated, tortuous veins & haems in all 4 quadrants • ischaemic (iCRVO) vs. non ischaemic (niCRVO) • ischaemic = non perfused, haemorrhagic • non-ischaemic = perfused, venous stasis retinopathy

31. Epidemiology (EDCCS) • 2 per 1000 > 40 years, 5.5 per 1000 > 64 years • 33% ischaemic, 67% non ischaemic • 13% < 45 years, 11% 45-54 years, 76% > 55 years

32. Clinical features • reduced visual acuity • RAPD • retinal predictors of ischaemia • degree of intraretinal haemorrhage • venous dilatation • venous tortuosity • as chronicity develops • IRMA, microaneurysms, collateral vessels

34. Complications • macular oedema, ischaemia • NVE / NVD (6-7%) • iris neovascularisation (NVI), neovascular glaucoma (NVG) (21%) • cilioretinal artery occlusion • combined with CRAO

35. Large areas of ischaemia on FFA

36. Iris neovascularisation

37. Comined with CRAO: cherry red spot with white macula

38. Classification • ischaemic vs non-ischaemic • two ends of a spectrum • elderly: if severe, retinal capillaries decompensate, iCRVO • young: if mild or moderate, retinal capillaries withstand increased venous pressure, niCRVO • young vs old •  40 yrs, 64% final VA  6/9 • > 40 yrs, 40% iCRVO

39. Good perfusion on FFA

40. Poor peripheral perfusion on FFA

41. Differential diagnosis • Anterior ischaemic optic neuropathy / optic neuritis / optic nerve invasion • asymmetrical diabetic retinopathy • ocular ischaemic syndrome • severe anaemia, leukaemia • Waldenstroms macroglobulinaemia • carotico-cavernous fistula

42. Branch retinal vein occlusion • A cause should be found for it! • Most common caused: diabetes mellitus, hypertension and lipid abnormalities • Investigations need to be done by the referring physician, not in screening setting, however, you need to notify the physician • You will find asymptomatic old BRVO-s in screening setting

45. Embolic disease: local protocol, but requires GP notification so risk factors for stroke and sight threatening disease can be addressed

46. The normal optic nerve and its pathological changes Key issues for discussion • Learn the normal anatomy of the optic nerve • Discuss the function of the optic nerve and its connection to the brain • Discuss major illnesses affecting the optic nerve • Discuss the main features of the glaucomatous changes of the optic nerve Learning outcome • Identify the main features of the optic nerve and discuss the function • Identify normal optic nerve on teaching slides • Identify the main features of the diseases optic nerve

47. The Normal Optic Nerve Head • The optic nerve head can be imagined as a ‘plug-hole’ down which over 1 million nerve fibres descend through a sieve-like sheet known as the lamina cribrosa. These fibres are then bundled together behind the eye as the optic nerve which continues towards the brain. •  The retinal nerve fibres are spread unevenly across the surface of the retina in a thin layer. As the nerve fibres converge on the edge of the disc they pour over the scleral ring and then down its inner surface. This dense packing of nerve fibres just inside the scleral ring is visualized as the neuroretinal rim. • The inner (with respect to the centre of the optic nerve head) edge of this neuroretinal rim marks the most central of the nerve fibres. This edge is usually sloped, yet may be range from an overhang to vertical to a gentle slope towards the centre of the disc. This inner edge marks the cup edge.

48. Scleral Ring Outer edge Inner edge (outer edge of disc or neuroretinal rim Neuro-retinal rim Cup Edge Change in direction of blood vessel

49. The Scleral Ring • This ring is usually pale allowing it to be distinguished from the neuroretinal rim tissue which is pink. The ring may not be visible in a given disc image, or the visibility may vary in different areas of the circumference of the disc. It is often easier to see on the temporal side of the disc than on the nasal side.

50. Scleral ring As vessels bridge the scleral ring, they often make a slight change in direction (black arrow) which may be a clue to its inner edge, The change in colour is also evident in this case (arrows mark inner and outer edges) Blurring of the image may occur due to media opacity or resolution of the image- this can make appreciation of the anatomy difficult. Inner Outer