Ophthalomolgy Flashcards
Embryology of eye = when does optic fissure close
Closes in sixth week of gestation
What is aniridia
malformation of the whole eye
What is part of anterior segment of the eye
Conjuctiva
Episclera
Externally visible portion of sclera
Cornea
Anterior chamber
Iris
Lens
What is posterior segment of eye
Vitreous cavity
Retina
Retinal pigment epithelium
Choroid
Posterior sclera
What is the retina a continuation of?
Posteriorly - optic nerve
Anteriorlgy - fuses with the epithelium of the ciliary body
What does the outmost layer of the retina made up of
Photoreceptors
Rods
Cones
What does the macular retina provide?
Central and colour vision
Centre is called fovea
What are rods sensitive to ?
Low levels of high - peripheral and night vision
What is the fovea responsible for?
Visual acuity
What do the photoreceptors do?
Sensory receptors of the Retina
When does vascularisation of the retina begin
Begins at 14 weeks gestation
Not complete until term
What is vascularisation of the retina stimulated by
Stimulated by vascular endothelial growth factor (VEGF-A) and insulin-like growth factor (IGF-1)
What is retinopathy of prematurity ROP
Neovascular disorder affecting infants born at less than 32 weeks
What are other risk factors for ROP
Extremely low birth weight <1000g
Early supplemental oxygen requirement
Acidosis
Two phases of ROP
- Hyperoxic phase - premature delivery into high oxygen environment causes down regulation of VEGF
Hypoxic phase - unvascularized anterior retina becomes ischaemia as it matures - VEGF unregulated and leads to neovascularisation
Stages of ROP
- Demarcation line at anterior edge of vascularised retina
- Line becomes thickened ridge
- Ridge develops neovascularisation
- Localised tractional retinal detachment
- Funnel retinal detachment
Cataracts
Disorganised protein fibre structure or accumulation of abnormal metabolic produce within the lens causes opacification
Unilateral congenital cataracts
Most commonly result from abnormal regression of enbryological hyaloid vascular system
Childhood glaucoma is characterised by
Raised intra-ocular pressure and optic disc cupping
What does uncontrolled glaucoma lead to?
Loss of peripheral visual fields
What is normal intra-ocular pressure in children
6 and 18 mmHg
What causes increase in intra-ocular pressure
Result of impaired aqueous outflow through the trabecular meshwork rather than overproduction of aqueous by ciliary body
When does primary congenital glaucoma present
Presents within 1st year of life
Usually bilateral
Causes of secondary glaucoma
Anomalies of anterior segment
Sturge-Weber sydnrome
Following congenital cataract surgery
Topical, inhaled or oral steroid therapy
How does steroid therapy increase risk of glaucoma
Increases accumulation of glycosaminoglycans or trabecular meshwork-inducible glucocorticoid response protein
Retinal haemorrhage in NAI
Due to acceleration/ de-acceleration injury causes multiple multi-layer haemorrhages and retinoschisis (Splitting of layers of retina)
Characteristic of child glaucoma
eyes watering
photophobia
corneal hazing
What are first signs of diabetic retinopathy
Dot haemorrhages - weakened capillaries and therefore microanuerysm
What does the surface ectoderm form
Lens
Corneal epithelium
What does the neuroectoderm form
Retina
Iris
Cillary body
Optic nerve
What does the meschyme form?
Vasculature of the eye
Pathological nystagmus causes
Infantile sensory nystagmus
Infantile idopathic motor nystagmus
Acquired nystagmus secondary to neurological disease
Acquired vestibular nystagmus
Infantile nystagmus
Usually horizontal
Jerks
Conjugate and similar in both eyes
Ass. head oscillation
Worsens when one eye is covered
Need to be reviewed by ophthalmologist
Conjugacy
Both eyes demonstrate the same movement
Why does disconjugate nystagmus trigger concern
Potenital neurological disease
See-saw nystagmus
Pendular (phases of quell velocity)
One eye elevates and rotates inwards whilst other eye depressed and rotates out
Causes - supra-cellar and rostral midbrain lesion
Upbeat nystagmus
Jerk
Vertical with fast phase upwards
Causes - lesions of cerebellar vermis and brainstem
Downbeat nystagmus
Jerk
Vertical with fast phase downwards
Causes - Arnold chair malformation
What drug causes nystagmus
Carbmazepine
What is spasmus nutans
Triad of head turn, head nodding and nystagmus
Which direction is the slow phase in vestibular nystagmus directed in?
Slow phase directed to side of lesion
Which direction is fast phase in cerebellar nystagmus directed in?
fast component directed to side of lesion
Amblyopia
Causes reduced vision in one eye
‘lazy eye’
Unilateral and persists despite correction with glasses
What is anisocoria
Difference in size of pupils
Myopia
Short sighted - distance objects blurred
Features of diabetic retinopathy
Dot and blot heamorrhages
Cotton wool spots
Venous bleeding
micro aneurysm
Stage 1 sickle cell retinopathy
salmon patches and sunburst spots
Stage 2 sickle cell retinopathy
artierovenous anatomies
Stage 3 sickle cell retinopathy
sea-fan neovascularisation pattern
Stage 4 sickle cell retinopathy
retinal haemorrhage -> vitreous detachment
What does meschyme form
vasculature and vitreous
forms zonular fibres - affected in marfans sydndrome
Vascularisation complete ?
40 weeks
starts at 14 weeks
If you have an exotorpia where is the eye
Deviated outwards
Tropia
Always deviated
Phoria
sometimes deviated
When d you pick up a phoria
during cross cover test
