Presentation on theme: "Diabetic retinopathy screening NSF-based training"— Presentation transcript:
1 Diabetic retinopathy screening NSF-based training Anatomy and physiologyTunde PetoHead of Reading Centre
2 Anatomy and physiology of the normal human eye Key issues for discussionReview the gross anatomical structures within and related to the eyeball and discuss their basic functionReview the basic physiology of refraction and visionLearning outcomeIdentify the different structures of the eye and discuss their basic functionIdentify different anatomical structures on teaching slides
3 Basic Science in relation to eye disease: the normal retina and vision Key issues for discussionThe normal anatomy of the retinaPhotoreceptors and their biochemistryPhysiology of vision including colour visionLearning outcomeIdentify normal retinal structure on teaching slides
4 Vision Reflected light translated into mental image Pupil limits light, lens focuses lightRetinal rods and cones are photoreceptorsFigure 10-36: Photoreceptors in the fovea
5 PhotoreceptorsRods – monochromatic, provide night vision: most numerous in periphery, sees all shades of grey and white; see in dark and around usPeripheral changes might not affect the vision at allLaser treatment and retinal detachment might result in visual field lossCones – 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 DetailFigure 10-38: Photoreceptors: rods and cones
8 Vision: Integration of Signals to Perception BipolarGanglionMovementColorOptic nerveOptic chiasmOptic tractThalamusVisual cortexFigure 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 discussionNormal changes in the aging retinaAbnormal changes in the aging retinaThe constituents of drusenGeographic atrophyNeovascular AMDLearning outcomeIdentify age related changes in the retinaIdentify and discuss different types of drusenIdentify geographic atrophyIdentify and discuss the main features of neovascular AMD
29 Vascular occlusion Key issues for discussion Learn normal vasculature of the eyeDiscuss most common systemic causes of vascular problems in the eyeDiscuss vein occlusionDiscuss arterial occlusionDiscuss clinical implications of these diseasesLearning outcomeIdentify normal and abnormal vascular structures in the eye on teaching slidesIdentify strategies to deal with these diseases
30 Central retinal vein occlusion: Introduction dilated, tortuous veins & haems in all 4 quadrantsischaemic (iCRVO) vs. non ischaemic (niCRVO)ischaemic = non perfused, haemorrhagicnon-ischaemic = perfused, venous stasis retinopathy
31 Epidemiology (EDCCS)2 per 1000 > 40 years, per 1000 > 64 years33% ischaemic, 67% non ischaemic13% < 45 years, 11% years, 76% > 55 years
32 Clinical features reduced visual acuity RAPD retinal predictors of ischaemiadegree of intraretinal haemorrhagevenous dilatationvenous tortuosityas chronicity developsIRMA, microaneurysms, collateral vessels
37 Comined with CRAO: cherry red spot with white macula
38 Classification ischaemic vs non-ischaemic young vs old two ends of a spectrumelderly: if severe, retinal capillaries decompensate, iCRVOyoung: if mild or moderate, retinal capillaries withstand increased venous pressure, niCRVOyoung vs old 40 yrs, 64% final VA 6/9> 40 yrs, 40% iCRVO
42 Branch retinal vein occlusion A cause should be found for it!Most common caused: diabetes mellitus, hypertension and lipid abnormalitiesInvestigations need to be done by the referring physician, not in screening setting, however, you need to notify the physicianYou 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 discussionLearn the normal anatomy of the optic nerveDiscuss the function of the optic nerve and its connection to the brainDiscuss major illnesses affecting the optic nerveDiscuss the main features of the glaucomatous changes of the optic nerveLearning outcomeIdentify the main features of the optic nerve and discuss the functionIdentify normal optic nerve on teaching slidesIdentify 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 Cup Edge Neuro-retinal rim Outer edge Inner edge (outer edge of disc or neuroretinal rimNeuro-retinal rimCup EdgeChange in direction of blood vessel
49 The Scleral RingThis 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 Inner Outer 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.InnerOuter
51 The Cup edgeThis is undoubtedly the most difficult contour to identify, and is subject to more variability than the disc edge.The inner edge of the neuroretinal rim (=cup edge) may be sloped (especially on the temporal side of the disc) or vertical. In some cases the edge may be an overhang.The most effective way of drawing this ring is to identify certain points on the cup edge where you are sure of its location, and then using a dot-to-dot procedure link up these points into a ring. First look for a blood vessel, preferably a small to medium-sized one (large vessels do not hug the surface and may not be tethered to the surface and therefore are unhelpful). Trace its path across the scleral ring and then over the rim tissue- at some point it will change direction as it bends inward towards the centre of the disc. If the slope is shallow this will be a gradual change in direction, however if vertical it will be an obvious bend, and in the case of an overhang it will suddenly disappear from view. It is the point of maximum change of direction of the vessel that marks the cup edge. When viewing the disc in stereo, the edge of the cup can often be clearly seen in areas where there are no vessels as a guide.There can be a temptation to mark the cup edge where the colour changes from the pink of the rim to the pallor of the cup. In many situations this would be correct, yet in some situations the edge of pallor is not necessarily the edge of the cup, and hence it is better to rely on vessels and stereo cues as described above.The following images illustrate these points.
52 The cup edge The Cup Edge: 3 blood vessels here show the edge of the cup:The points of maximum inflection (bend) are marked by arrows.
53 The cup edgeCup Edge:In this very clear image, the arrows mark the cup edge. This illustrates that occasionally large vessels may obscure the edge from view, and in this case one should mark points of certainty either side of the vessel and link these up.
54 Optic nerve head assessment Dr. Patricio SchlottmannResearch FellowGlaucoma Research Unit
56 DefinitionGlaucoma is a chronic, progressive optic neuropathy that manifests by a characteristic Visual Field loss and distinctive structural changes recognizable at the level of the Optic nerve head or the Retinal Nerve Fibre Layer (RNFL)
57 Definition Chronic: having a progressive course of indefinite duration Progressive: tending to become more severeOptic neuropathy: disease of the of the optic nerve
58 Definition Optic neuropathy The ganglion cells and their axons are the damaged structuresOther cells within the retina are also affected
63 Risk factors African derived individuals Glaucoma is 4 times more prevalentIs usually more severeStarts at earlier ageProgresses more rapidly
64 Risk Factors Family history of glaucoma A first degree relative affected by glaucoma increases the risk of developing the disease in the futurePatients should be questioned about the severity of glaucoma in the affected relative
65 Risk Factors Increased age Prevalence increases with age It is 10% of subjects over 80 years
66 Cup/disc Definition Relationship between cup area and disc area Disc