Conjunctiva & Eyelids Flashcards
Describe the anatomy of the eyelids
Orbicularis Oculi - muscle controls closing of the eyelid
Levator Palpebrae Superioris & Muller Muscle (smooth) control opening of the eyelid
Palpebral Conjunctiva (lines the inner surface)
Tarsal Plate
Cilia (eyelashes)
Lacrimal Puncta (tear ducts)
Meibomian Gland Orifices
Meibomian Glands (white/yellow sebaceous columnar glands at right angles to eyelid margin
Describe the function of the eyelids
Closure:
Protects eye from trauma (NB Menace - learned response)
Blinking:
Distributes tear film (nutrition & hydration to ocular surface)
Drains tear film (pumps tears into nasolacrimal canaliculi) Physical removal of debris from ocular surface
Contributes to tear film:
Mucin (goblet cells of palpebral conjunctiva)
Lipid (Meibomian glands)
Describe the anatomy of the third eyelid
Central T-shaped cartilage
Conjunctiva covering bulbar & anterior faces
Stromal connective tissue
Lymphoid follicles on posterior surface
Nictations gland at base
Dog: lacks musculature
Cat: smooth muscle to retract
Describe the function of the third eyelid
Protects ocular surface
Leading edge distributes tear film & physically removes debris from corneal surface
Third eyelid gland contributes to tear film: approx 1/3rd of aqueous production
Contains immunoglobin (IgA) secreting plasma cells - role in defence of ocular surface
Describe the anatomy of the conjunctiva
Mucous mebrane lining the surface of the cornea & the inside of the eyelids sensory innervation by ophthalmic branch of trigeminal nerve
Bulbar Conjunctiva
- Covers sclera white wall of the eye)
- Finer, branching conjunctival vessels overlie larger, straighter
episcleral vessels
Palpebral
- Lines the inner aspects of the upper & lower eyelids
Describe the function of the conjunctiva
Protects ocular surface whilst allowing free movement of ocular structures
Contributes to tear film
Goblet cells produce mucin
Most exposed mucous membrane so must respond rapidly to noxious stimuli
‘Everted Lymph Node’ : Stroma contains C.A.L.T (Conjunctival Associated Lymphoid Tissue - regulates immune response)
Many lymphocytes which form active follicles when stimulated by antigens
Describe the anatomy of the nasolacrimal system
Lacrimal puncta small slits located near the nasal angle of the eye
These lead to the lacrimal canaliculi which then opens into the lacrimal sac
The lacrimal sac is the beginning of the nasolacrimal duct occupies a funnel shaped fossa within lacrimal bone
Excess fluid may then travel down and out of the nasal punctum
Describe the function of the nasolacrimal system
To drain tears from the ocular surface
How would you examine the eyelid?
Good light source, hands-off & hands-on
Blinking
Menace response, palpebral reflex
Blepharospasm
Ocular pain
Tear staining
Excess lacrimation (pain), epiphora (non-painful overflow)
Assess conformation/eyelid position
Breed-related problems e.g. entropion
Skin disease
Dermatitis, crusting, ulceration, alopecia
Look for extra hairs, masses, swellings
How would you examine the third eyelid?
Retropulse globe to protrude third eyelid
Pushing the globe back into the orbit through closed lids
Look underneath third eyelid
NB variation in normal pigmentation
How would you examine the conjunctiva?
Identify nasolacrimal puncta
Flush nasolacrimal ducts
Jones Test
How would you examine the nasolacrimal system?
Examine palpebral conjunctival surface compare to bulbar conjunctiva
Assess colour
Semi-transparent, variable pigment.
Abnormal colour - jaundice, cyanosis, toxaemia
Inflammation
Swelling (chemosis), ocular discharge
Petechiae/subconjunctival haemorrhage
List the common conditions that affect the eyelid. Describe their pathologies
Entropion - inversion of part or all parts of the eyelid
Ectropion - eversion of the eyelid ‘diamond eye’
Macropalpebral Fissure - refers to excessively large palpebral fissures
List the common conditions that affect the cilia. Describe their pathologies
Distichiasis - Extra eyelashes emerging from meibomian gland orifices
Ectopic Cilia - Arise from follicle inside or near meibomian gland (through conjunctival surface
Trichiasis - Located normally but abnormally directed hair whihc contacts the ocular surface
List the common conditions that affect the third eyelid
Prolapsed Nictitans Gland
Scrolled Cartilage
Third Eyelid Protrusion
