Anatomy and Physiology Flashcards
Name the 7 features of the optic system:
- High Resolution
- Wide Field
- Ocular Movement
- Stereopsis
- Colour representation
- Integration of the above
- Interpretation
What are the 3 external layers of the globe?
- Sclera and cornea
- Uvea
- Retina
What is the sclera continuous with anteriorly and posteriorly?
Anterior: with the cornea at the limbus
Posteriorly: Dural sheath of the optoc nerve
What is the Uvea made of?
- The iris,ciliary body and the choroid
What is the optic disk and why is it important?
It is the blind spot of the eye-the retina and choroid are absent in this area
What does the anterior segment of the globe consist of?
- cornea
- anterior and posterior chambers
- iris and ciliary body
- lens and zonules
What is the posterior segment of the globe of the eye?
- Sclera
- choroid
- retina
- optic disc
Name the general anatomy of the eye
What are the 3 types of refractive error?
- Myopia
- Hypermetropia
- Astigmatism
What is another name for the lateral geniculate body?
Thalamus
What is the place called where the two optic nerves join together?
The optic chiasm
Where is the visual field located?
In the occipital lobe
What is cranial nerve 3?
Oculomotor nerve
What does parasympathetic stimulation do to the pupil?
It constricts the pupil(relaxed state)
How many types of photoreceptors are there? Name them:
Theres 5
Bipolar cell and Ganglion cel- NB for providing transmission from the retina to the brain
Horrizotal and Amacrine cells
Rods and cones cells-Rods are for monochromatic sight and cones are for colour
What is presbyopia?
This is when the lens loses its refractive power as people get older >40 yrs
Define refraction:
The bending of light as it crosses through the interface between two media of two optical densities
What is physiological myopia?
- Low grade myopia
- Slowly progresses to adult and then become static
Define Pathological myopia:
What are the symptoms of myopes?
They have got bad distance vision but good near vision
What sort of treatment do myopes need?
They need a concave spectacle or contact lens
What is the definition of hypermetropia?
Hypermetropia is defined as long-sightedness. It is when the axial lengthn of the eye is too short for the normal refractive power of the anterior segment
Describe what refractive error that is
Myopia
What are the 2 symptoms of eye strain?
Headache and eye discomfort
Hypermetropia is commonly associated with?
Strabismus
Define astigmatism?
Astigmatism is defined as when the corneal curvature is not the same and thus does not have the same refractive power in all directions(shaped more like a rugby ball than a soccer ball)
Patients with Astigmatism have lurry vision at____
At all distances
If the patients Visual Acuity imroves with the use of a pinhole then:
It points to the patient possibly having a refractive error
What are the 5 different types of refractive surgery?
- Refractive Lens Exchange
- Radial keratotomy
- Astigmatic keratotomy
- Photorefractive keratotomy
- Lasik
What is the principle that repairs myopia?
We try to flatten the cornea because it is too wide and thus the refractive power is too strong that it ends up in front of the retina
What is the principle that governs the surgical repair of hypermytropia?
This involves making the cornea more wide by putting in circular gutter in the mid-periphery
What is cranial nerve II?
The optic nerve
What is cranial nerve V?
Trigeminal Nerve
Another name for External Hordeolum?
Stye
What do external hordeolum’s present with?
- Tender
- Inflamation at the eyelid margin
- Spontaneus resolution with/without drainage
What is the treatment for External Hordeolum?
- Remove the affected eyelash
- local antibiotic
- warm compress
What does this picture depict?
External Hordeolum
What does this picture depict?
Internal Hordeolum
What is depicted in the image below?
Chalazion(Meibomian Cyst)
What is this?
Blepharitis
What are the aetiological factors associated with chronic blepharitis?
- Staphylococcocal infection fo the eyelash follicles
- Abnormal secretions from the tarsal glands
What other medical conditions is chronic blephoratis associated ?
- Seborrheic dermatitis
- acne
- atopic exzema
- dry eyes
*
What are the complications of chronic blepharitis?
- recurrent conjunctivitis
- internal/external hordeola
- chalazia
How long does it take to treat chronic blepharitis
1-3 months
Regarding the treatment of blepharitis of the eyes/eyelid, what AB could we use?
Fucidic acid cream or systemic tetracyclines
What is this?
Molluscum Contagiosum in AIDS patient
Describe Molluscum Contagiosum:
Rased pink/white nodules on the eyelid of the skin with central umbilication
What is described in the picture below?
Entropion
What are the complications of entropion?
The eyelash hairs are inverted into the conjunctiva and scratches the cornea and causes irritation and epithelial damage
Describe what is happening in this image:
- Ectropion
Because the lower lid no longer guides tear flow to the _______-, it is often associated with epiphora.
Inferior punctum
What does epiphora mean?
The excessive watering of the eye
What is this condition called?
Ptosis
What are the aetiological classes of ptosis?
- mechanical-odema or tumour in eyelid
- involution-as a result of aging
- myogenic-myasthenia gravis and congenital dystrophy
- neurogenic-cranial nerve III paralysis and Horners syndrome
When must we take ptosis seriosly?
- When it’s a recent onset especially due oculomotor paralysis
- When it involves a child under the age of 8-can lead amblyopia(lazy eye)
Describe this condition
Dermatochalasis- This happens as people age and the eyelid skin gets loose. Surgical removal of the skin is NB
What is xanthelasma associated with?
Hyperlipidaemia and usually occurs on the medial canthus
Basal cell carcinoma?
The most common primary malignancy of the eyelid mainly in older patients.
Squamous Cell carcinoma?
The second most common type of tumour of the eyelid-more common in patents with HIV/AIDS
Describe Kaposi’s sarcoma:
Red, elevated tumour of the conjunctiva and eyelids in AIDS patients
What is the most importnant function of the endothelium in the cornea?
It allows drainage of water from the stroma to the aqueous humour to prevent corneal odeoma
How many layers is the cornea comprised of?
5 layers
- Epithelium
- Basement Layer
- Stroma
- Descemet’s layer
- Endothelium
The corneal epithelium is supplied with a rich network of sensory nerve fibres from the_________________
Ophthalmic branch of the trigeminal nerve
What can we use to stain epithelial ulcers?
Florescein stains
What are some of the signs and symptoms of corneal ulceration and infiltration?
- redness
- blephoraspasm
- tearing
- pain
- photophobia
- reduced vision
- halos around ligts
What is an important principle from this picture we must remeber?
Testing of corneal sensation and comparison with healthy eye is NB.
Make sure we do not take from the sick eye and place in the healthy eye
The lesion in the central corneas mean:
That it is infected by bacteria, fungi and viruses
The peripheral zone of the cornea means that it leads to:
Immune complexes and is much safer
When must you refer a patient with corneal ulceration to an opthalmologist?
- The presence of a hyppyon regardless of the cause
- Any discrete lesion that does stain with fluorescein
- Any corneal lesion that leads to a decrease in visual acuity
What are the organisms of baceterial keratitis that can penetrate the corneal epithelium without any trauma?
Neisseria gonorrhoea
Neisseria meningitidis
Coynebacterium diptheriae
What are the 3 most commonest organsims that cause bacterial ulceration?
- streptococcus pneumoniae
- preudomonas
- staphylococcus aureus and epidermis
corneal opacification happens when_____
corneal ulceration is not detected and picked up early enough
What is the management of bacterial keratits?
- washing eyes off with saline drops
- Cycloplegic drops to stop the ciliary spasm pain
- Local antibiotic drops
4.
What are the AB drops we use to treat bacterial keratitis?
4th generation fluoroquinolones-moxifloxacin
or 2nd/3rd generation fluoroquinolones-ciprofloxacin
What are the complications bacterial keratitis?
- permanent corneal thinning
- permanent corneal opacification
- corneal perforation
- anterior uveitis with hyppyon
What causes fungal keratitis?
After interaction with animals or plants
What are the clinical features of fungal keratits?
The eye is red and inflamed
satellite lesions
A hypopyon with funas is usually inside
What is the treatment for fungal keratitis?
Amphotericin B topically for 3 months
Systemic fluconazole for 3 months
What is primary herpes simplex keratoconjunctivitis?
It is a virus that affects mostly young adults and children
They present with low malaise, typical vesicular skin rash on the eyelids and pdendritic keratitis
How does recurrent herpes simplex virus present?
With irritation, tearing and moderate photophobia
The signs include a dendritic ulcer becoming a geographic ulcer
And the loss of corneal sensation
What is the treatment of viral keratitis?
Acyclovir ointment 5 times a day
Cyclopegia
Explain the disciform keratitis manifestation?
It is a complication fo herpes simplex keratoconjuncitivits
It presents with a round,dull area of corneal oedema due to an immune response-the patients vision is dramatically reduced
What is this picture assocaited with?
Herpes zoster opthalmicus associated with involvement with the opthalmic branch of the trigeminal nerve
The appearance of Hutchinsons sign means that:
There is ocular involvement because of the nasociliary nerve
Peripheral corneal ulceration andthinning is caused by:
Antigen-antiibody reaction
What collagen vascular disease is associated with peripheral ulceration and corneal thinning?
Rheuatoid arthritis
What are phlyctenulosis caused by?
They are caused by delayed hypersensitivity to bacterial antigens. In SA, TB is the most common reason in other areas it is staphylococcus
Neurotropic corneal ulceration is when:
due to the opthalmic division, there is loss of corneal sensation
What is tarsorrhaphy?
Early temporary or permanent closure of the eyelid
Which pt’s doe exposure keratopathy happen to?
- unconscious
- under anaesthesia
- exophthalmos
- severe ectropion
- bells palsy with lagophthalmos
What is keratoconus?
Weakening of the corneal stroma which causes thinning and bulging of the central and inferior paracentral cornea
