Flashcards in Opthalmology Deck (87)
Which walls of the orbit are most likely to fracture as a result of blows and direct trauma?
Medial and inferior.
They are particularly thin.
Name the 2 muscles that allow movement of the eyelid and their respective innervation.
1. Orbicularis oculi - facial
2. Levator palpebrae superioris - oculomotor
What is a chalazion?
Obstruction to the tarsal glands leading to a painless swelling of the eyelid
What is a hordeolum?
A ‘stye’ or hordeolum can results from acute infection of a gland of Moll, Zeiss or the eyelash follicle.
NOTE: Modified sweat glands (glands of Moll) and sebaceous glands (glands of Zeiss)
Name the 3 components of the lacrimal apparatus.
1. Lacrimal glands
2. Lacrimal ducts
3. Lacrimal canaliculi
Describe the passage of The lacrimal fluid entering the conjunctival sac through the lacrimal ducts until it is swallowed.
The lacrimal fluid entering the conjunctival sac through the lacrimal ducts passes into the lacrimal lake at the medial angle of the eye from which it drains to the lacrimal sac.
The fluid passes to the nasal cavity through the nasolacrimalduct, which opens into the nasal cavity (into the inferior meatus) from which it passes into the nasopharynx and swallowed.
Name the 3 components of the tear film.
1. Surface lipid layer: secreted by the meibomian (tarsal) glands
2. Middle aqueous layer: secreted by the lacrimal gland and accessory lacrimal glands
3. Inner mucus layer: secreted by goblet cells of the conjunctiva and the epithelial cell surface
Name some causes of dry eyes.
- Deficiency of the tarsal glands e.g. obstruction to their openings
- Reduced production of tears e.g. autoimmune disease such as Sjogren’s syndrome, rheumatoid arthritis
- Medications e.g. antihistamines
Describe the components of the 3 layers of the eyeball.
1. Outer protective layer: sclera and the cornea
2. Middle layer: choroid, ciliary body and iris
3. Inner layer: retina consisting of optic and non-visual parts
Describe the 2 chambers of the eyeball.
1. Anterior chamber: the space between the cornea and the iris
2. Posterior chamber: the space between the iris and the ciliary body and the lens
What does the Hillary body secrete?
Name the 2 muscles that control the size of the pupil.
Sphincter and dilator pupillae
What is the cavity behind the lens filled with?
What are the photoreceptor cells found at the macula lutea specialised for?
What is the fovea centralis?
A depression in the centre of the macula, the area of most acute vision.
Describe the blood supply to the retina.
The retina is supplied by the central artery of the retina and drained by the corresponding vein.
Describe the 3 main roles of the cornea.
1. Maintaining transparency (so that we have a clear window through which to see)
2. Ocular protection (including the corneal reflex)
3. Refraction of incoming light (along with the overlying tear film)
Name the 5 layers of the cornea.
2. Bowman’s membrane,
4. Descemet’s membrane
Why do central corneal wounds heal slower than more peripherally located defects?
Corneal stem cells are also located at the periphery of
the cornea at the ‘limbus’
How long does it take for the corneal epithelium to regenerate.
The total time for regeneration of the corneal epithelium is quoted as between 3 to 14 days, being longer for central epithelial defects.
What is the significance of recognising Bowman's layer of the cornea?
This is an acellular layer and separates the overlying epithelium from the underlying stroma. It is important to recognise as any trauma extending below this level will result in
corneal scarring as only the epithelium is regenerated.
Why is the cornea transparent?
It consists of an arrangment of regularly orientated collagen fibres (type 1 predominantly). The regularity with which these are arranged helps to explain the transparency of the cornea.
Describe the innervation of the cornea.
The cornea has a rich nerve supply derived mainly from the ophthalmic branch of the trigeminal nerve (via long ciliary nerves). In some case there is innervation via the maxillary branch which supplies the inferior cornea.
Describe how a patient with infective keratitis would present and why.
- A loss of epithelium exposes free nerve endings causing severe pain.
- The inflammation also leads to increased peri-corneal vascularity and a red eye.
- There is an associated watery discharge with epiphora.
- As the corneal surface and tear film is disrupted along with possible corneal oedema there is a resultant drop in visual acuity.
- There may also be photophobia and a mucus or mucopurulent discharge.
What is a hypopyon?
A collection of pus behind the cornea in the anterior chamber
What are ‘cells’ and ‘flare’ in relation to infective keratitis?
‘Cells’ and ‘flare’ are leucocytes and protein respectively derived from the leaky iris blood vessels responding to the infection.
What is responsible for maintaining an adequate pressure in the eye?
IOP is a balance between the rate of production of aqueous and the rate of drainage.
Describe the passage of the aqueous humour from the ciliary process of the ciliary body to the system venous circulation.
Aqueous humour is produced by the ciliary processes of the ciliary body. It then flows up
between the iris and anterior surface of the lens and through the pupil.
After passing through the drainage angle of the eye which consists of the trabecular meshwork followed by the Canal of Schlemm.
Aqueous then drains into the episcleral vessels and finally into the systemic venous circulation.
How is IOP measured?
IOP is measured by measuring the force needed to flatten the corneal surface using a tonometer.