Ophthalmology Flashcards
Emmetropia
Eye with no visual defects
Ametropia
Refractive error present/light rays not directly focused on retina
Myopia
Short sighted
- light rays brought to focus in front of retina
- eye is too long = axial myopia
- lens is too strong = index myopia
Hypermetropia
Long sighted
- light rays brought to focus behind retina –> eye is too short
OR converging power of cornea or lens is too weak
Astigmatism
Cornea is not spherical
Rugby ball NOT football
What is accommodation?
Physiological mechanism that allows close objects to be focused on the retina
- In non accommodative state - ciliary muscle relaxed allowing suspensory ligaments of lens to remain taut
- During accommodation - ciliary muscle contracts + suspensory ligaments become lax allowing lens to assume a convex shape
Entropion
In-turning of the lid, usually lower
- Causes = ageing, bacterial
- Tx = topical abx to prevent infection, tape down lower lid (temp), surgery
Ectropion
Eversion of lower lid
Causes = ageing, VII CN palsy
Tx = lubrication + surgery
Ptosis
Drooping of the eyelid
Blepharitis
Chronic inflammation of eyelid margins
Characteristics of Glaucoma
Optic disc cupping
Visual field loss
IOP is increased to impair normal optic nerve function
Types of Glaucoma
Primary open angle (POAG)
Primary acute angle closure
Secondary
Congenital
POAG syndrome
- Raised IOP >21
- Open aqueous draining angle e.g. no macroscopic blockage of aqueous outflow
- Pathologically cupped optic disc
- Glaucomatous visual field loss
Normal IOP
10-21mmHg
What is ocular HTN
Raised IOP >21 but normal optic disc + field
Causes of POAG
Ageing
Steroids (topical + systemic)
Inherited
Associations of POAG
Fam hx
Ocular (high myopia, retinal vein occlusion)
Systemic e.g. DM
Sx of POAG
Usually none but visual loss is noticed when condition advanced
Diagnosis of POAG
Reduced visual acuity (advanced) Pathologically cupped optic discs - C:D ratio >0.5, pallor - Nasal shift of vessels - Haemorrhages - Asymmetry of C:D Glaucomatous visual field loss Raised IOP >21 Open drainage angle on gonioscopy
What is glaucomatous visual field loss?
Initially nasal step progressing to arcuate Scotoma then later tunnel vision
Rx of POAG
Topical ocular hypotensive - 1st line = latanoprost - 2nd line = timolol Systemic hypotensives e.g. acetazolamide Drainage surgery
Cataracts
Any opacity in the normally transparent lens of the eye
Causes of cataracts
Ageing = commonest 2nd to ocular disease 2nd to systemic disease 2nd to drugs e.g. steroids Congenital
Sx of cataracts
Gradual blurred/cloudy/misty vision, glare
Tx of cataracts
Surgery - phakoemulsification + posterior chamber intraocular lens (IOL) implant
Central retinal artery occlusion
- Sudden profound loss of vision
- Caused by emboli obstructing the retinal artery e.g. stroke
- Occasionally caused by vasculitis e.g. GCA
- Cherry red spot –> due to intact reflex of fovea standing out against ischaemic retina
Cherry red spot
Central retinal artery occlusion - intact reflex of the fovea stands out against ischaemic retina
Central retinal vein occlusion
- Secondary to atherosclerotic thickening of central retinal artery compressing the central retinal vein at a common crossing point
- Occlusion of vein results in retinal hypoxia + resultant endothelial cell damage leads to extravasation of blood
Fundoscopy = severe tortuosity, engorgement of retinal veins, deep haemorrhages, cotton wool spots + optic disc swelling
Optic atrophy
Death of nerve fibres in optic nerve
- Pale optic disc
- Primary caused by inflammation (optic neuritis), glaucoma or general retinal ischaemic
- Secondary caused by longstanding papilloedema
Papilloedema
Optic disc swelling secondary to raised ICP
“optic disc swelling” is term used for any cause e.g. space occupying lesion, optic neuritis, malignant HTN, uveitis (TB, sarcoidosis)
- Optic disc appears blurred + small haemorrhages
Hypertensive retinopathy - grade 1
Arteriolar narrowing
Hypertensive retinopathy - grade 2
Areas of focal narrowing + compression of venules at sites of arteriovenous crossing (AV nipping)
Hypertensive retinopathy - grade 3
Features similar to those of DM retinopathy e.g. retinal haemorrhages, hard exudates + cotton wool spots
Hypertensive retinopathy - grade 4
Optic disc swelling
What are the stages of diabetic retinopathy
Background diabetic retinopathy
Pre-proliferative retinopathy
Proliferative retinopathy
Advanced retinopathy
Background diabetic retinopathy
- Microaneurysms (outpouchings of capillaries that leak plasma constituents into the retina)
- Dot + blot haemorrhages (from bleeding capillaries in the middle layers of retina)
Pre-proliferative diabetic retinopathy
Presence of retinal ischaemia represents progression from background to pre-proliferative
- Cotton wool spots
Proliferative diabetic retinopathy
Insufficient retinal perfusion results in production of VEGF –> development of new vessels on retina (neovascularisation)
- New vessels at the disc NVD
- New vessels elsewhere NVE
Advanced diabetic retinopathy
- Recurrent vitreous haemorrhage from bleeding areas of NV
- Tractional retinal detachments as areas of NV grow into vitreous + form fibrous bands suspending the retina
- Rubeosis as NV occurs at iris + drainage angle result in increased intraocular pressure + progression to glaucoma
Pan-retinal photocoagulation (PRP)
Primary tx for proliferative diabetic retinopathy
- Reduces VEGF
