Pathology of the eye Flashcards
State the inverse care law.
The availability of good medical care tends to vary inversely with the need for it in the population served.
Identify the leading causes of blindness/Severe Sight Impairment worldwide. What proportion of blindness is avoidable or treatable ?
- Cataract (number 1 cause)
- Uncorrected refractive error
- Age-related macular degeneration (main cause in developed countries)
- Diabetic retinopathy
- Glaucoma
- Corneal opacities
80% is avoidable or treatable
Identify the main pathologies of the anterior segment of the eye.
- Cataract (i.e. opacification of lens)
- Corneal ulcer
How are corneal ulcers treated ?
Antibiotic
Identify risk factors of cataracts.
- Age
- Diabetes
- Trauma (or anything that touches the lens)
- Inflammation (e.g. uviitis)
- Steroid use
- UV/Radiation
- Congenital
Identify corneal ulcer risk factors.
- CONTACT LENSES (hence don’t sleep, swim, shower with lenses)
- Varicella/Herpes (because reduces corneal sensitivity long term)
- Steroid drop use (immunosuppresant)
- Dry eyes/Exposure (surface more vulnerable to infection)
- Trauma/Burns (may expose eye)
Describe presentation of a corneal ulcer.
Sore eye Injected eye (red eye) Watering Hypopyon (Epithelial defect, can be stained to show)
What is the relation between corneal ulcer and keratitis ?
Keratitis (e.g. due to contact lens) can lead to corneal ulcer
Identify the main treatments for cataracts.
Surgery
1) MSICS- mot common form, in middle to low income countries
2) Phaecoemulsification (initial incision through cornea, no need for stitches)
3) Femtosecond laser
Why does abnormal red reflex occur (in general) ?
Anything obstructing the path of light from the front to the back of the eye
Identify different causes of abnormal red reflex.
- Retinoblastoma (leucocoria = white red reflex)
- Congenital cataract (black lines)
- Corneal scar
- Vitreous hemorrhage
Describe the genetics of retinoblastoma.
- Knudson ‘2-hit’ hypothesis
- RB1 - tumour suppressor gene
- Hereditary - earlier, bilateral (because only need to acquire one more mutation to get disease)
- Non-hereditary - later, unilateral
True or false: every newborn gets a red reflex check.
TRUE
Identify the main types of ophthalmoscopy.
DIRECT OPHTHALMOSCOPY
-Arclight
INDIRECT OPHTHALMOSCOPY
- Slit lamp
- Binocular indirect ophthalmoscope
Identify conditions of the posterior segment of the eye.
- Diabetic retinopathy
- Retinopathy of prematurity
- Age-related macular degeneration
- Swollen disc
- Cupped disc
- Glaucoma
How does diabetic retinopathy lead to blindness ?
Blindness due to:
• Growth of new vessels; they bleed (vitreous haemorrhage), and may cause tractional retinal
detachment (once they have fibrosed) and rubeotic glaucoma
• Diabetic maculopathy: Leakage of fluid from damaged vessels; macular oedema with loss of central visual acuity
Define rubeotic glaucoma.
“VEGF makes tiny blood vessels grow, which we call ‘new blood vessels’. As the drain of trabecular meshwork in the anterior chamber is blocked, the aqueous is trapped in the eye putting the eye pressure up. This may cause corneal oedema”
Blinding + Painful
Describe treatment of diabetic retinopathy.
- Lifestyle – smoking, weight, exercise
- Blood sugar/pressure/cholesterol
- Support renal function
- Laser, anti-VEGF, surgery
Identify an imaging technique to view the posterior segment of the eye.
OCT (Optical coherence tomography)
Describe pathogenesis of diabetic retinopathy.
In general, diabetes –> Biochemical mechanism –> Microvascular damage –> Mechanical processes –> Retinopathy
Increased glucose leads to:
- Non-enzymatic glycation
- Oxidative/reductive stress
- Aldose-reductase activation
- Diacylglycerol-proteinkinase C activation
All of these then result in microvascular endotheliopathy, which in turn leads to:
- Increased permeability
- Capillary occlusion
- Neovascularisation
All of which lead to retinopathy
How does retinopathy of prematurity arise ?
Similar pathological mechanism to diabetic retinopathy: when babies are born before retina is vascularised, hypoxic area of retina demands oxygen but nothing to supply with oxygen, so get VEGF creating new useless blood vessels that
can bleed and form ridge around the edge, causing retinal detachment which will cause blindness if untreated.
Which epidemic of premature retinopathy are we currently experiencing ?
Third epidemic in middle-income countries
Describe treatment for retinopathy of prematurity.
- Laser peripheral retina, obliterating it, to stop oxygen demand from occurring.
- Injections with anti VEGF
How can we prevent retinopathy of prematurity ?
Screening programme (exists in the UK)
