Disorders of the Orbit & Nasolacrimal System Flashcards
Anopthalmus
- What is it
- Pathogenesis
- Absent globe
- Severe developmental deficiency in the primitive forebrain (non-viable fetus)
Microphthalmos
- What is it
- Pathogenesis
- Mini globe
- Any remnants of globe inside the orbit
- Early deficiency in the size of the globe, associated with a small palpebral fissure
Cyclopia & Synophthalmia
- Single median globe (C) or two incompletely separated or fused globes (S)
- Ingestion of Veratrum californicum weed on Day 14 of gestation
Converging Strabismus
- Eyes meeting at point of nose
- Bilateral convergent strabismus with exophthalmia (BCSE) –>inherited in Jersey, German Cattle breeds; Inherited in Siamese cats
Diverging Strabismus
- Eyes going in different directions
- Hydrocephalus -> “sunset eyes”
- “Normal” in brachycephalic breeds
How is orbital disease examined?
Neuro-ophthalmic evaluation, globe retropulsion, oral exam, ancillary dx tests (orbital u/s, CT, MRI, +/- biopsy)
Lesion within orbital cone can cause what?
Exophthalmos -> will always be opposite direction of where the mass is
Acquired Disorders
Orbital Cellulitis / Abscess
- Presentation
- Pathogenesis
- Diagnostic tests
- Treatment
Presentation:
- Acute, unilateral exophthalmos
- Pain upon globe retropulsion & opening of the mouth
- eyelid protrusion
- non-specific signs of ocular discomfort; mucopurulent discharge
Causes:
- penetrating wound thru mouth, foreign body
- tooth root abscess
- zygomatic and salivary gland infections
Treatment:
- drainage
- systemic broad-spectrum abx
Acquired Disorders
Sialoceles
- Presentation
- Pathogenesis
- Dx tests
- Tx
Presentation
- Cystic structures (glandular or epithelial tissues)
- Exophthalmos and protrusion of eyelids
- Minimal pain upon examination
Causes
- trauma, HBC
- leakage of saliva from zygomatic gland / duct –> inflammation in orbit
- ulceration of oral mucosa (e.g., post dental procedure)
Dx
- U/s, CT
- Aspiration of yellowish / tenacious fluid, +/- blood
Tx
- Surgical excisio of cyst and gland
Acquired Immune-Mediated, Inflammatory Myopathy
Masticatory Muscle Myositis (MMM)
- Etiology
- Presentation
- Dx
- Tx
Etiology:
- Immune-mediated, inflammatory disorder of the Temporalis, masseter and pterygoid muscles (2M myofibers!)
Presentation:
- Young, large-breed dogs
- Exophthalmos with 3rd eyelid elevation
- Severe pain upon palpation, restricted jaw mvmts -> anorexia
- Chronic : enophthalmos = atrophy of affected muscles
Dx
- CT scan, MRI, muscle biopsy
Tx
- Oral corticosteroids, but immunomodulatory therapy long term
Acquired Immune-Mediated Inflammatory Myopathy
Extraocular Muscle Myositis
- Etiology
- Presentation
- Dx tests
- Tx
Etiology
- immune-mediated inflammatory myopathy of the extraocular muscles
- *CD3+ lymphocytic infiltration
Presentation
- bilateral exophthalmos without 3rd eyelid elevation
- Non-painful on examination!
- retraction of upper eyelid
- Chronicity: enopthalmos, strabismus
Dx tests
- U/s, CT, MRI
- muscle biopsy
Tx
- oral corticosteroids with complete resolution within several months
Acquired Disorders
Orbital Neoplasia
- How is it treated?
- Difference b/w 1º and 2º?
- Presentation?
- Treatment = exenteration (remove all contents of orbit, including fat, 3rd eyelid and sometimes periosteum, vs. enucleation which is just the globe removal)
- 1º = arises from orbital tissue, 2º = invade orbit from adjacent structures
- slowly progressive exophthalmos
- unilateral and **non-painful
Acquired Disorders
Proptosis
- Pathogenesis
- Treatment
- Prognosis
Pathogenesis
- sudden, forward displacement of the globe with entrapment of the eyelids behind the equator of the globe
- trauma!
- brachycephalic breeds (due to shallow orbit)
Treatment
- globe replacement (tarsorrhaphy)
- enucleation (hyphema, If ≥2 exophthalmos are avulsed
Prognosis
- Vision = guarded-to-poor
- Stronger prognosis if Pt still has PLRs
Clinical signs, course of action, dx, tx?
Clinical Signs: Chemosis, conjunctive hyperemia, 3rd eyelid elevation, thick mucous discharge
Course of Action: Thorough history, try opening the mouth, globe retropulsion, culture
Dx: Orbital Cellulitis
Treatmet: Drainage + broad-spectrum systemic abx (then modify based on culture). Long-term tx~
Function of the Nasolacrimal System
thin-walled conduit that drains the tear film from the eye into the nasal passages
Functions of the pre-corneal tear film (PTF)
Composition of the PTF?
Most common cause of Quantitative tear film deficiency?
(KCS) –> immune-mediated
Causes of Qualitative tear film deficiency
Differences in diagnosing Qualitative vs. Quantitative Tear Film Deficiency
Qualitative: Rose Bengal stain, Tear film breakup test
Quantitative: Schirmer Tear Test (normal range = 15-25 mm/min)
Clinical manifestations of NLS disorders (3)
How can NLS disorders be diagnosed?
Schirmer tear test
Fluoresccein dye passge (Jones’ Test)
**Flushing of NL duct to determine if noromograde or retrograde)
