16 DIABETES: Flashcards
Three structural changes in diabetic retinopathy
Microvascular circulation changes from prolonged hyperglycemia (compromise blood-retinal barrier) (e.g. venous dilation, increased retinal blood flow, tissue hypoxia, loss of pericites in retinal capillaries, thickening of basement membrane, damage and proliferation of endothelial cells → capillary non-perfusion and loss)
Microaneurysms (Etiology: mechanical weakness of capillary wall, vasoproliferation of endothelium), (Pathogenesis: breakdown of inner BRB, microaneurysms develop as physical weakening of capillary walls → localized saccular outpouchings of vessel walls)
Changes in haemodynamics (microvascular abnormality formation produces leakage of plasma, haemorrhage and vascular shunting)
Diabetic Retinopathy PATHOGENESIS and RESULTS
Vascular occlusion (Capillary occlusion: loss of pericytes, thickening of basement membrane, damage and proliferation of endothelial cells) (Haematological: decreased oxygen transport) → RESULTS in retinal ischaemia, arteriovenous shunts, neovascularization of retina, optic nerve, iris (rubeosis iridis)
Vascular leakage (breakdown of inner BRB leads to leakage of plasma constituents into the retina) → RESULTS in increased vascular permeability (development of intraretinal haemorrhages and oedema). [two types of retinal oedema: diffuse = due to capillary dilation and leakage, focal = chronic retinal oedema leads to deposition of hard exudates]
What is HbA1c
Glycated haemoglobin
Haemoglobin is a component of RBC and binds to oxygen and glucose (becoming ‘glycated’)
HbA1c measured as an index for long term blood glucose control
Risk factors of Diabetic retinopathy
Duration of diabetes (>10yrs = 50% present, >30yrs = 90% present)
Elevated HBA1C (>8% significant risk)
Hyperglycaemia (fasting glucose > 7.03mmol/L)
Systemic hypertension
Hyperlipidemia (obesity)
Pregnancy (rapid progression of retinopathy)
Nephropathy (renal disease)
Gender (male)
Smoking status, ethnicity, dependence on insulin
Symptoms
Fluctuating vision - related to fluctuating blood glucose
Symptoms more suggestive of urgent referral: vision blurriness not correctable with refraction, sudden eye pain/redness, acute onset flashes and/or floaters
Signs and symptoms LIDS and CONJUNCTIVA
Signs: infection, inflammation, ulcerative blepharitis, styes, chalazion, conjunctivitis
Symptoms: sticky lids in the morning, sting or burning, redness or irritation, tearing, mucus or pus, visible or sensation of lumps, punctate epithelial erosions (PEE), SPK, reduced TBUT
Signs and clues CORNEA
Signs: corneal keratopathy, decreased corneal sensitivity/nerve density, corneal ulcers, corneal edema, altered epithelium basement membrane
Clues: cotton bud test, CL related infections/inflammations, stinging/burning, prolonged eye irritations, dry eyes, no discomfort on instilling dilation eye drops, no symptoms with associated ocular finding
Signs and Clues LENS
Signs: fluctuating myopia,, cataracts, light sensitivity
Clues: vision & prescription changing, glare/haloes, sensitivity to light, blurred vision that doesn’t improve with lenses/PH, lens opacity/snowflake
Signs and Clues EXTRAOCULAR MUSCLES
Signs: cranial nerve palsy, 3rd nerve (affect eye lid closed/smaller aperture; eye movement cannot move adduct and upwards; pupil can be enlarged and abnormal light reactivity), 4th nerve (vertical diplopia, head tilt, ipsilateral hypertropia), 6th nerve (double vision, affected eye cannot abduct)
Clues: double vision, head tilt, closed eye/smaller aperture, vertical diplopia, shadow/overlap of images, restricted eye movements, any diagnosed diabetic neuropathy
Signs and Clues PUPIL and IRIS
Signs: autonomic neuropathy, rubeosis iridis, neovascular glaucoma
Clues: pupil does not dilate as expected/sluggish, reddish discolouration of the iris, increased eye pressure, blood vessels in angle
Signs and Clues OPTIC NERVE
Signs: optic neuritis, diabetic papillopathy
Clues: slow progressive vision loss, washed out colours, decreased contrast sensitivity, pain and around eyes especially on eye movements and ONH swelling
Visual functional changes and management
Dry eye syndrome (rx of artificial tears, lubricants and dry eye management. Monitor for corneal complications)
Corneal changes (monitor for keratitis, ulceration, delayed wound healing if CL wearer)
Rubeosis iridis (gonio rule out AC involvement and neovas. Tono rule out secondary glaucoma)
Cataracts (monitor lens opacification and status of associated retinopathy; extraction necessary if visualization of retina becomes inadequate)
Colour vision (tritan CV loss - DFE to screen for CSME)
Refractive Error and Acc Dysfunction (consult with GP regarding glucose control and update spx)
EOM palsies (neuro-ophthalmology consultation, prism rx, eye patching)
Afferent Pupillary defects (workup to rule out optic neuropathy)
Classification of Diabetic Retinopathy STAGE 1
Classification of Diabetic Retinopathy STAGE 2
Management of DR STAGE 1
Management of DR STAGE 2
NO abnormalities
Mild non-proliferative diabetic retinopathy. Microaneurysms only
Review 2 yrs. If high risk, review yearly
Review 6-12 months
Classification + Management of Diabetic Retinopathy STAGE 3
Moderate non-proliferative diabetic retinopathy
Retinal dot and blot haemorrhages, hard exudates or cotton wool spots, ± microaneurysms, no signs of severe non-poliferative diabetic retinopathy ANY OF THEM
Management: Review 3-6 months, communicate DR to GP + endocrinologist and mention possible benefits of fenofibrate in slowing DR progression
Classification + Management of Diabetic Retinopathy STAGE 4
Severe non-proliferative diabetic retinopathy
More than 20 intraretinal haemorrhages in each of the 4 quadrants, definite venous beading in 2 or more quadrants, prominent intra-retinal microvascular abnormality (IRMA) in 1 or more quadrants, no signs of proliferative retinopathy ANY OF THEM
Management: Ophthalmology referral
