What is the term given to constriction of the pupil?
What problems with the lens can cause vision disturbance?
- Loss of clarity
- Acute cataract - think diabetes
- Dislocation through trauma or Marfans
What is Fuch's dystrophy?
- Autosomal dominant condition
- Slowly progressing disease - glare and blurring
- Corneal oedema and vision loss
- Loss of endothelial cells
- Thickening of Descemet's membrane
- Can also be triggered by cataract surgery
Which gene has been linked to retinoblastoma and which chromosome is it found on?
Retinoblastoma gene on Chromosome 13
Describe closed angle glaucoma
- Angle is narrowed
- Iris obstructs trabecular network/ canal of Schlemm
What posterior chamber problems can cause vision distubance?
- Loss of clarity
- Vitreous detachment
- Retinal detachment
Describe the Acathomoeba infection of the eye
- Caused by protozoa
- It is normally found in soil and water
- Can cause keratitis if contact lens hygeine is suboptimal
How many layers (laminae) are present in the lateral geniculate nucleus, and what does each do?
- 1 & 2 - magnocellular; movement and temporal contrast
- 2-6 - parvocellular; colour, spatial contrast
- 1-6 - Koniocellular; blue-yellow contrast
What are the 3 proteins found in the membranous discs of rod and membrane folds in cones?
- Visual pigment (retinal plus opsin)
- Transducin (G protein)
- cGMP phosphodiesterase
What happens to the 11-cis retinal molecule when hit by a photon?
It isomerses to 11-trans retinal which is freely diffuses along the membrane to activate multple molecules of transducin
Which division of the nervous system dilates the pupil and what is the term for this?
Sympathetic nervous system
What are the symptoms of dorsal midbrain syndrome?
Light near dissociation:
- Light causes no reaction to the pupil
- Near response causes the pupils to constrict
Failure of upgaze
What is a condition can commonly cause a relative afferent pupillary defect?
Retrobulbar neuritis in multiple sclerosis
What are the symptoms of giant cell arteritis?
- Blurred vision or sudden blindness
- Tender, nodular, temporal artery
What is seen under the microscope in retinoblastoma?
What is the immediate treatment of giant cell arteritis if it presents in an A & E setting?
High dose steroids to preserve sight
What is the main pathology of the uveal tract?
Malignant melanoma of the uveal tract
What is the best treatment for wet AMD?
What is the efferent limb of the pupillary light reflex made up of?
- Edinger-Westphal nucleus
- Oculomotor nerve
- Ciliary ganglion
- Short ciliary nerves
- Sphincter pupillae
What structure keeps the lens under tension when focusing on objects in the far distance?
The zonule (lens ligament)
What are the main support cells found in the retina?
- Muller's cells
What conditions can cause secondary glaucoma?
- Inflammation/ uveitis
- Phacogenic (Cataract/ lens subluxation)
- Drugs such as steroids
- Diabetes/ neovascular
What structures constitute the afferent limb of the pupillary light reflex?
- Ocular media
- Optic nerve
- Optic chiasm
- Optic tract
- Pretectal nuclei
What are the main differences between dry and wet AMD?
- Drusen and abnormalities of RPE (Retinal Pigment Epithelium)
- Usually little impact on vision unless RPE atrophy develops
- New vessel growth from the choroidal layer
- Severe impact on vision
Describe herpes simplex keratitis
- Corneal ulceration due to HSV (re-activation)
- Dendritic ulcer
- Causes blurred vision and pain
What cells do the axons of the optic nerve synapse with inside the lateral geniculate nucleus?
What are the 4 main groups of glaucoma?
- Chronic open angle
- Closed angle
What muscle contracts to relax the lens, allowing focusing on near objects?
The ciliary muscle
What is the effect of a single photon hitting a rod, in terms of ion channels?
It inhibits about 300 ion channels, altering the cells excitability
What cells are involved in transmitting a change in photoreceptor potential to the ganglion cells, both directly and indirectly?
- Bipolar cells
- Amacrine cells
- Horizontal cells
What are the 2 main distributions of retinoblastoma and how are they different?
- 1st year of life presentation
- Bilateral tumours
- Present up to the age of 5
- Unilateral tumour
Why must a squamous cell carcinoma-in-situ of the conjunctiva monitored/addressed?
It can progress into invasive squamous cell carcinoma.
Where do the majority of ocular trauma occur in the elderly and children?
In the home
Which muscles are responsible for convergence and which nerve innervates them?
Left and right medial rectus muscle
Innervated by Oculomotor nerve (CNIII)
How is an relative afferent pupillary defect tested for, and what would you see in a positive test?
Swinging light test
The pupil appears to dilate when a bright light is swung from the unaffected eye to the affected eye.
Which type of AMD is the most common?
What are the causes of dorsal midbrain syndrome (Parinaud's syndrome)?
- Pineal tumour
- Multiple sclerosis
How does anti-VEGF therapy work?
It inhibits and reverses new blood vessel formation in the retina.
What are the symptoms of AMD?
- Central vision distortion or missing
- Loss of contrast sensitivity
- Usually bilateral
What is giant cell arteritis?
It is an inflammatory disease of large and medium sized arteries, usually of the head and neck
What problems with the anterior chamber can lead to visual disturbance?
- Loss of clarity/ volume
- Blood (hyphaemia)
What are the risk factors for glaucoma?
- Ethnicity; East Asian - closed angle, Afro Caribbean - open angle
- Family history
- Diabetes mellitus
What is the main cause of a squamous cell carcinoma-in-situ of the conjuctiva?
What are the 5 layers of the cornea?
- Corneal epithelium
- Bowman's membrane
- Corneal stroma
- Descement's membrane
- Corneal endothelium
What are the 3 components of the near repsonse?
- Constriction of the pupil
- Convergence of the eyes
Describe chronic open angle glaucoma
- Trabeculae leading to canal of Schlemm blocked
- Angle normal
What corneal problems can lead to sudden visual disturbance?
- Loss of clarity
- Acute pressure rise
- Corneal infection
Where do the axons of the ganglion cells leave the eye and what effect does this congregation have on vision?
It produces the blind spot
What are the 2 type of AMD (Age related Macular Degeneration)?
- Atrophic (DRY)
- Exudative (WET)
What is the usual presenting symptom of a retinoblastoma?
Leukocoria (white reflex of eye)
Describe a cataract and its causes
It is opacification of the lens due to denaturation of its proteins.
Leads to loss of visual acuity and contrast
- UV light
- Other types of radiation
- Old age
- Drugs such as steroids
What is the most common intraocular malignancy of children?
Which cell in the eye is the first to produce an action potential in response to light?
The ganglion cells
What is the main pathological process involved in exudative AMD?
What are the 10 layers of the sensory retina?
- Retinal pigment
- Photorecptor layer
- External limiting membrane
- Outer nuclear membrane
- Outer plexiform layer
- Inner nuclear layer
- Inner plexiform layer
- Ganglion cell layer
- Nerve fibre layer
- Internal limiting layer (most superficial, inside eye)
What is the main cause of a developmetal glaucoma?
Which part of the visual system do the nasal half of optic nerves decussate?
What nerve, and division of the nervous system are involved in contraction of the ciliary muscles?
The occulomotor nerve carrying parasympathetic nerve fibres
What are the signs of a squanmous cell carcinoma-in-situ- of the conjunctiva?
- Thickened conjunctiva
- Abnormal maturation with pleomorphism
- High mitoses
What arethe major sources of ocular trauma in young adults?
What pathologies of the retina can lead to vision loss?
- Vascular occlusions; arterial & venous
Which part of the visual system is affected to produce a positive swinging light test?
Anywhere anterior to the optic chiasm
What are the clinical findings seen in giant cell arteritis?
- Raised ESR (>60mm/hr)
- Raised CRP
- Giant cells and chronic inflammation
- Thickening of intimal layer with narrowing of lumen
Which brain structure is the lateral geniculate nucleus a part of?