Diabetic Retinopathy Flashcards
Classification of diabetic retinopathy
- Non-proliferative diabetic retinopathy (NPDR)
- Mild NPDR
- Moderate to severe NPDR
- Proliferative diabetic retinopathy (PDR)
- Maculopathy
Types of lesions detected in NPDR on fundoscopy
Microvascular damage w/o neovascularization
Types of lesions detected in mild NPDR on fundoscopy
- microaneurysms
- dot and blot hemorrhages
- hard (intra-retinal) exudates
Types of lesions detected in moderate to severe NPDR on fundoscopy
- microaneurysms, dot and blot hemorrhages, hard (intra-retinal) exudates (exacerbated)
- cotton wool spots
- venous beading & loops
- intra-retinal microvascular abnormalities
- venous beading = sausage shaped dilatation of retinal veins
Types of lesions detected in PDR on fundoscopy
- neovascularization of retina, optic disc or iris
- fibrous tissue adherent to vitreous face of retina
- retinal detachment
- vitreous hemorrhage
- pre-retinal hemorrhage
Types of lesions detected in maculopathy on fundoscopy
- clinically significant macular edema
- ischemic maculopathy
Pathogenesis of diabetic microangiopathy
(Hyperglycemia)
- basement membrane thickening
- non-enzymatic glycosylation
- increased free radical activity
- increased flux through polyol pathway
- osmotic damage
Describe the hemostatic abnormalities of microcirculation
3 steps of platelet coagulation = initial adhesion, secretion & further aggregation
Platelets (DM ptn) stickier than platelets (non-DM) -> secrete prostaglandins -> other platelets adhere to them -> blockage of vessel & endothelial damage
Cotton wool spots
- white, fluffy lesions in nerve fiber layer
1. Concomitant swelling of local nerve fiber axons
2. Occludes retinal pre-capillary arterioles supplying nerve fiber layer
Fluorescein angiography finding for cotton wool spots
No capillary perfusion seen in the area of these soft exudates
Hard exudates (intra-retinal lipid exudates)
- accumulation of lipids (within sensory retina) leak from surrounding capillaries & microaneurysm -> circinate pattern
Intra-retinal microvascular abnormalities
- Abnormal, dilated retinal capillaries
- Represents intraretinal neovascularization
- indicates that severe NPDR is progressing to proliferative retinopathy
CSME
Intercellular fluid comes from leaking microaneurysm/from diffuse capillary leakage
Diagnosis of CSME
Stereoscopic assessment of retinal thickening by slit lamp biomicroscopy
(Modified Airlie House criteria)
CSME defined as presence of 1 or more of the following
- Retinal edema within 500 microns of centre fovea
- Hard exudates within 500 microns of fovea (associated with adjacent retinal thickening)
- Retinal edema (one disc or more diameter)
How to reduce risk for visual loss in CSME?
Laser grid photocoagulation reduces risk by 50% at 2 years
Ischemic maculopathy seen in
Type 1 DM
Ischemic maculopathy due to
Drop out of perifoveal capillaries with non-perfusion
Finding seen on fluorescein angiography
Enlargement of foveal avascular zone
2 types of diabetic retinal detachment seen in late disease
- Non-rhegmatogenous (caused by traction alone)
- Rhegmatogenous (caused by traction & retinal break formation)
Characteristics of non-rhegmatogenous detachment in PDR
- Detached retina confined to post fundus & extends > 2/3rd of distance to equator
- Taut & shiny surface
- Concave towards the pupil
- No shifting of subretinal fluid
Screening for diabetic eye problems (if there is a h/o any visual symptoms or changes in vision)
- Measurement of visual acuity
- Iris examination by slit lamp biomicroscopy prior to pupil mydriasis
- Pupil myrdiasis (tropicamide 0.5%) - risk of angle closure glaucoma
- Examination of crystalline lens by slit lamp biomicroscopy
- Fundus examination by slit lamp biomicroscopy using diagnostic contact lens/slit lamp indirect Ophthalmoscopy
Screening for Type 2 diabetic patients w/o retinopathy
Assessed at time of diagnosis and bi-annually thereafter
Screening for ptn with DM & mild NPDR
Assessed every 12 months
Particularly looking for onset of CSME
