ds of eye and ears E3

anatomy of eye

tunica fibrosa

• cornea

• sclera

tunica vasculosa (uvea)

• iris

• ciliary body

• choroid

3 chambers of eye

• anterior chamber

• posterior chamber

• vitreous chamber

• Anterior chamber

• – In front of the cornea, the first chamber 

• Contains aqueous solution/ fluids 

• Together with the aqueous solution joints with the posterior chamber 

Posterior chamber

– also produces aqueous solution 

• Vitreous chamber/ body

• – biggest chamber, contains vitreous fluid 

• Used in necropsy procedure

other parts of the surrounding eyeball

• palpebra

• conjunctiva

• teargland

• nictating membrane

• extraocular mm

• superior and inferior obliques

• recti

• muscle

  • dorsal

  • ventralatteral

  • medial

  • retractobulbi

etiologies of eye disorder

• bacterial

  • moraxella, Neisseria catarrhalis, mycoplasma conjunctivae, B. canis

• chalmydia

  • (conjunctivitis in cat) and reckettsiae (ticks and mites vector)

• parasitic

  • (eyeworms: thelazia, oxyspirura, philopthalmus and toxoplasma)

• viral

  • herpesvirus

• mechanical and chemical irritations

• allergic

• mycotic infection

bacterial

• Moraxella bovis

• – Infections bovine keratoconjunctivitis 

  • Better known as pinkeye 

  • Transmitted by face flies 

  • While feeding on lacrimal secretions, they transmit Moraxella from one bovine to another 

bacterial

• Neisseria catarrhalis

• – normal flora of the oral and upper respiratory tract of companion animals (dogs & cats) 

  • Lx caused – coming from wound bites 

bacterial

• Mycoplasma conjunctivae

• – common causative agents of respiratory diseases 

  • Common Lx – specific to this, respiratory problems à eye Lx 

bacterial

• Brucella canis

• – brucellosis common in bovines, goats, livestock causing mastitis; 

  • In canines, causes Lx in the reproductive system 

  • Can also be seen in the eyes  

chlamydiae

Causes conjunctivitis in cats

Rickettsiae – transmitted by ticks and mites (vector)

parasitic 

• Caused by eyeworms such as: 

  • Thelazia

  • oxyspirura

  • Philophthalmus

  • toxoplasma

Nematodes ((Roundworms, whipworms, hookworms)

• Thelazia (roundworm) 

• Moves like a worm/serpent in the eyes of the dog 

• Zoonotic to humans; eyeworm in humans as well 

• Regular deworming renders this not a threat to the owner 

• In companion animals specifically: 

• In the US: Theilazia californiensis 

• In Asia: Theilazia callipaeda 

• Manually take off can be a solution – sedate first the dog for risks 

• Pyrantel – drug  

• T. guloSA, t. skrjabini, and T, rhodesii – livestock  

Nematodes ((Roundworms, whipworms, hookworms)

• Oxyspirura petrowi

• – found in quail 

trematodes (flukes) 

• Philopthalmus 

• found in wild birds 

• Genus Philopthalmidae 

protoza 

• Sheds oocyst in the feces 

• In the body will undergo reproduction (in the cat) 

• Dispersed in the different parts of the body 

• Cat continuously sheds the oocyst in their feces 

• This can transmit this disease to other animals – dogs, humans 

• Can stay in the dog/ humans; the oocyst can burrow in the tissues such as skeletal, alimentary in the form of cysts and remain dormant as such 

• When immunosuppressed, it can become lethal 

• Can burrow in the tissue of the brain as a cyst as well 

• Toxoplasma gondii – Uveitis, retinitis, choroiditis,  

• Specific host: only the CAT family can be hosts 

• Asymptomatic 

virus 

• Herpesvirus – is usually at the genital organs but can cause eye Lx 

• In dog – Herpesvirus 2 (FHV-1) 

• In cat – herpesvirus 1 

• Can cause secondary infections such as papillomavirus (papillomas) 

Mycoses

Superficial Lx of the skin, usually external. 

• If left untreated, commonly in stray dogs, the eyes and ears are also affected 

• Crusty, flaky skin; likely with Lx in the ear 

• Due to this, other causative agents can enter the skin of the eyes and ears causing disease 

• E.g. Dermatophycosis – can make the skin very dry 

• If the eye is infected, the ear will always be paired (mycoses specific) 

tear deficiency can happen because of the following causes: 

Most common and #1 cause: age 

• Tear production lowers as one ages 

  2^nd cause is medication that can cause reduced tear production 

• Antihistamines 

• Antidepressants 

• Decongestant 

  3^rd cause is medical condition causing reduction of tears 

• Distemper (practically closed eyes because of the lack of tear production)  

• Arthritis 

• lupus 

mechanical & chemical

irritations such as when one scratches their eyes 

• tear film together with corneal epithelium become damaged from excessive scratching 

lining of epithelium of the eye

is the eyelid 

• made of non-keratinized squamous epithelium 

• associated with columnar cells with goblet cells 

• secretes mucin/ mucous (muta/luha) 

exception include (in the dog)

• THIRD EYELID (with upper and lower eyelid) 

humans used to have a third eyelid and lost it from evolution; it is simply a remnant 

TEAR FILM –

In front of the eye, supposed to be clear, 

• hydrates and keeps on moisturizing the eyes – prevents infection 

• dryness of eyes = more prone to infection 

3 layers of tear film

• lipid layer

• aqueous layer

• mucin layer

• lipid layer (1st layer)

• Produced by Meibomian gland 

• aqueous layer (2nd layer)

• Contains: protein, water, electrolytes – those being produced by the lacrimal glands 

• mucin layer (3rd layer)

• Produced by the goblet cells of the columnar epithelium 

mucin

is the compensatory mechanism of the eye to compensate for the loss of tears 

• Is not enough to lubricate the eyes and thus becomes sticky 

entropion 

inversion of palpebral margin 

• Infection of this if left untreated will worsen 

• First harming the tear film, then the corneal epithelium, and eventually the corneal stroma 

• Can eventually cause ulcerations of the cornea 

• Tx: TACKING – surgical procedure 

• Typically a triangle-shaped incision due to the coverage of the ligament covering their nose 

• Common in short-nosed breed of dogs 

• Prone to cephalic breed of dogs  

ectropion 

eversion of palpebral margin (esp. lower eyelid) 

• Must be corrected surgically 

• Causes chronic irritation if left untreated – can eventually become a neoplasm  - squamous cell carcinoma  

 

• Less common than entropion 

• Ectropion – maybe due to the overcorrection of entropion 

• Common in large breed of dogs that has many eye folds 

• e.g. Bernard, hounds, chowchow (prone to entropion and ectropion) 

Trichiasis

condition where normally positioned hairs, often around the eyes, grow in a way that they rub against the cornea or conjunctiva, causing irritation 

• Common in brachycephalic breeds of dogs 

Distichiae 

are hairs that grow in an abnormal location on the eyelid margin (specifically emanating from gland ducts) 

• Grows outside the margin 

• e.g. in the hair glands – typically plucked but must be sterile to avoid infections in the oil glands 

Ectopic cilia 

growth of hair in the conjunctiva that grow specifically through the conjunctival surface 

• common again in brachycephalic dogs such as the Pekingese 

Coloboma 

absence of eyelids (may be partial or complete)/ portion of the eye tissue or iris is missing or underdeveloped 

Exopthalmos (propoptosis) 

protrusion of the eyeball 

• has many causes such as: 

• due to injury, bacterial, fungal, medical conditions such as hypo & hyperthyroidism 

enophthalmia/ enophthalmos 

bilateral retraction of eyeball 

• sunken eyes, displaced backward within the orbit 

• pairs with exophthalmos 

• happens because there is a loss of retrobulbar fat 

Hyopyon 

presence of pus cells in the anterior chamber of the eye 

• characterized by the accumulation of inflammatory cells in the anterior chamber of the eyes 

• if there is no other solution, it must be drained 

• the pus can come from Pseudomonas aeruginosa 

• Some anti-inflammatory cells will secrete myeloperoxidase – giving the pus green color 

Keratoglobus 

increased convexity of the cornea 

• Tx is via surgery 

Nystagmus 

abnormal oscillatory movement of the eyeball 

• Indicative of nervous problems – vestibular 

• Distemper – neuronal type 

 

The head is still & with no stimulus, the eyes move either: 

• Horizontally (side-to-side) 

• Vertical (up-down-up-down) 

• Rotary (round in circles) 

Uveitis 

inflammation of uvea (uvea/ tunica vasculosa): iris, ciliary body, and choroid 

 

• Must be differentiated from nuclear sclerosis 

• There is no cure for this ds but simple acceptance 

Keratitis 

inflammation of the cornea 

• E.g. IBK of bovine 

Blepharitis 

inflammation of the eyelids 

• In tagalog is kuliti 

Nyctalopia/ xerophthalmia 

night blindness; likely caused by deficiencies in Vit A/ retinol 

Anisocoria 

Refers to the mismatched constriction of pupils 

• Wherein one is dilated, and the other is constricted 

Mydriasis 

Both pupils are dilated 

• Difficult to treat 

• In surgery, when dilated indicates lack of optic nerve reaction – meaning likely non-responsive brain activity 

Miosis 

Constriction of pupils 

• Indicative in surgery because it can tell the stage of anesthesia; indicates that the animal is just asleep 

cataract 

clouding (opacity) of the lens, due to the clumping of protein in the lens 

• Not always white, can be blue 

Sclerosis 

has green margins 

• From age 

Hordeolum 

infection of the eyelids (oil producing glands of the eyelashes) 

• Reason for carefulness: plucking hair from distichiae 

Dacryocystitis 

inflammation of the lacrimal sac 

• Seen in distemper, parvo virus, could simply be blocked from canaliculi, from constricted duct 

• If the lacrimal ducts are destroyed, they have to be removed; maintenance with artificial tears 

pannus 

increased vascularization of the cornea 

• Pinkeye, overuse of cellphone, etc.  

Strabismus 

inability of one eye to attain binocular vision due to the imbalance of eyeball muscles 

synecchia 

adhesion (esp. of iris) to other parts of the eye 

normal ear anatomy

Like humans but have muscle tissues – allows for ear mobility 

• Continuously works for 24 hours – even in sleep, hearing does not stop 

 

How sounds are processed 

• Enters from the external ear, into the ear canal, moving inwards 

• Once sound touches the tympanic membrane, sounds are amplified 

• Amplified sounds are transferred into the ossicles 

• Smallest bones in the body which are components of the middle ear (there are 3: malleus, incus, stapes) 

• Malus à incus à stapes 

• Stapes will prepare the sounds to be transferred into the semicircular canal – organs of the vestibule; connects to the cochlea 

• Vestibule is the organ of balance 

• Transfers to the cochlea 

• Inside the cochlea, sounds will traverse with fluid (endolymph) 

• Once enters the Organ of Corti (which is inside the cochlea), it will travel with the hair cells of the organ of corti 

• Once the hair cells perceive the sound, they will interpret the sounds as electrical impulses to the vestibulocochlear nerve (acoustic nerve) 

• Which are then sent to the brain, which interprets the sounds 

Semicircular canals

are responsible for the sense of balance due to the displacement of perilymph (NOT endolymph) 

• Commonly dogs with distemper cannot balance properly because of this. 

Cochlea

is the organ with 3 turns, looking like a snail; containing endolymph, the Organ of Corti, and hair cells 

parasitic 

• Otodectes mites

• – with Lx looking like sand 

• Burrows under the skin of the ear 

parasitic 

• Sarcoptic mange (also known as scabies) 

• Zoonotic to people, and very common in stray animals 

• Highly contagious skin condition caused by the Sarcoptes scabiei mite 

• Causes rubbery skin that may cover the animal all over 

• Can also go to the ear 

bacterial 

• Pseudomonas otitis

• – in animals appear to always have pus 

• Wet, moist, and is filled with pus 

mites of livestock 

• Raillieta auris

• – would burrow in papilloma and warts of the ears 

mites of livestock 

• Raillieta auris

• – would burrow in papilloma and warts of the ears 

viral infections in ears 

• Distemper and parvo

• also emit Lx in the ears 

• Tx is to focus on the systematic infection and not the ear 

others include: 

• Viral & mycoplasmal pathogens 

• Mycotic such as Malassezia pachydermatis 

• Antibiotics such as: 

• Aminoglycosides (with ototoxic, hepatotoxic & nephrotoxic effects) 

deafness 

lacking/ deficient in the sense of hearing due to damage of cochlear parts; 

• cochlea has most of the components where vibrations are converted into impulses 

otitis 

general term for inflammation of ear structures 

• Otitis externa – affects the pinna and ear canal 

• Otitis media – affects the ear drum, stapes, malleus 

• Otitis interna – affects the cochlea 

Otosclerosis (hereditary) 

bone surrounding the middle and inner ear (stapes bone) grows excessively & therefore sounds are not transmitted properly à leads to deafness 

Perichondritis 

infection of cartilage of the outer ear 

Myringitis 

inflammation of eardrum 

tinnitus (symptom) 

noise originates in the eardrum rather than from the environment 

• Dogs hear tinnitus 

• Seen are: 

• Tendency to tilt head (compensatory mechanism) 

• Sudden stoppage of barking and looking at barking at an empty space