Eye

General

Anatomy & histology-other



Topic Completed: 1 February 2014

Minor changes: 18 December 2020

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PubMed Search: Anatomy [title] eye

Nat Pernick, M.D.
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Cite this page: Pernick N. Anatomy & histology-other. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/eyeanatomyother.html. Accessed December 6th, 2021.
Globe
  • Defined as eyeball itself plus intraocular tissues, or eye proper without its appendages
  • Dimensions: anterior-posterior 24 mm, vertical and horizontal dimensions are both 23 to 23.5 mm
  • Six extraocular muscles:
    • 4 rectus and 2 oblique muscles
    • Arise in posterior orbit from fibrous ring called annulus of Zinn, and insert into sclera
    • Muscles are surrounded by fascia
    • Inferior oblique inserts on sclera, other muscles insert on tendons
  • Equator: midway between anterior and posterior poles
  • Specimen is the result of enucleation, performed because eye is nonfunctional, painful, unsightly, infectious, contains neoplasm, post-trauma (may be removed to prevent sympathetic uveitis) or has chronic glaucoma
  • Globe usually intact but free of extraocular muscles and orbital fat
  • Globe may be eviscerated, with only fragments available for microscopic study
  • Initial pathologic processes may be obscured by subsequent pathologic processes
  • Enucleation: due to tumor (48%, usually melanoma), glaucoma (13%), phthisis bulbi (12%), recent trauma (11%)
  • Specimens also received after evisceration (10%) or exenteration (9%) to manage malignant orbital tumors (Am J Clin Pathol 2003;119:594)
  • During 1990 to 2000, decrease in percentages due to neoplasms, increase due to glaucoma and phthisis bulbi
Lacrimal duct & gland
  • Lacrimal gland located in superiotemporal aspect of orbit, not palpable
  • Contributes secretions to tear film including IgA
  • Accessory lacrimal glands are embedded above fibrous tarsus of eyelid and in conjunctival fornix
  • Serous with minor mucinous component
  • Larger ducts have myoepithelial layer
  • Normally may have lymphocytes and plasma cells
  • Drainage apparatus is composed of puncta, canaliculi, lacrimal sac and nasolacrimal duct
  • Tears drain toward medial canthus, then through lacrimal punctum into lacrimal canaliculi, then nasolacrimal sac, then nasolacrimal duct, then nose
  • Puncta:
    • Opening in medial aspect of eyelid where tear fluid drains
  • Canaliculi (lacrimal duct):
    • Tubular structures 0.5 mm in diameter where puncta drains
    • Nonkeratinizing squamous epithelium surrounded by fibrous tissue
  • Lacrimal sac:
    • Merging of canaliculi, encased by bones of orbit
    • Stratified columnar epithelium with goblet cells
  • Nasolacrimal duct:
    • Drains lacrimal sac, 1 cm long, connects to inferior meatus of nose
    • Stratified columnar epithelium with goblet cells
  • Lacrimal duct disorders often cause epiphora (tears flow over lid margin onto cheek), induration, inflammation of lower eyelid
  • Tumors tend to displace eye downward because adjacent orbit restricts growth
  • Tumors are difficult to resect completely leading to high recurrence rate
  • Lacrimal gland is considered a minor salivary gland for tumor reporting
  • Regional lymph nodes are preauricular (parotid), submandibular and cervical
Lens
  • Most surgical specimens are cataracts or prosthetic intraocular lens
  • Normal lens is biconvex, behind pupil / iris, in front of vitreous, in posterior chamber
  • 10 mm in diameter by 4 - 5 mm in width
  • Usually Gross Examination Only (report as transparent - Yes or No), don't section
  • Anterior lens capsule is eosinophilic acellular band overlying single layer of epithelial cells
  • Lens capsule is strongly PAS+, holds lens in place
  • Lens has thinner capsule posteriorly, without epithelial cells
  • Lens in held in place by zonules that connect to pars plicata of ciliary body
  • Lens normally opacifies with age due to globules of degenerate lens fibers
  • Is a closed epithelial system with lens capsule (epithelium) that totally envelops the lens
  • Vitreous humor:
    • Avascular
    • Extends from lens to sensory retina
    • Contains gel-like material composed of water, protein, hyaluronic acid and "hyalocytes"
    • Gel consistency is due to randomly oriented collagen fibrils
    • May appear as amorphous material on H&E
Orbit & optic nerve
  • Orbit contains globe and its fibrous covering (Tenon capsule), lacrimal gland, optic nerve and its meningeal covering, extraocular muscles, cartilaginous trochlea, blood vessels and delicate fibroadipose connective tissue
  • Floor of orbit is roof of maxillary sinus
  • Medial wall of orbit (lamina papyracea) separates orbit from ethmoidal sinuses
  • Proptosis: forward displacement of eyeball (or other organs), due to any disease that increases orbital contents, since orbit is closed medially, laterally and posteriorly
  • Exophthalmos: abnormal protrusion of eyeball
    • Common symptom of orbital disease, although often due to thyroid disease and not biopsied
    • Other common causes of exophthalmos are mucocele from paranasal sinus, hemangioma, inflammatory pseudotumor
  • Optic nerve:
    • Surrounded by meninges; part of central nervous system
    • Not usually biopsied
    • Often has psammoma bodies or drusen (calcified acellular globular concretions of nerve fibers)
    • Site of convergence of one million axons from retinal nerve fiber layer
    • Nerve head accounts for physiologic blind spot in normal visual field
    • Receives blood supply from branches of ophthalmic artery
    • Surrounded on both sides by short posterior ciliary arteries
  • Lamina cribrosa:
    • Site of myelination of optic nerve axons
    • Highlighted with Luxol fast blue or other myelin stains
  • Trochlea:
    • Arc shaped structure through which tendon of superior oblique muscle passes before insertion upon eyeball
    • The only cartilaginous structure in normal orbit
  • Tumors should be reported using formats published for their counterparts elsewhere in body
  • Drainage through submandibular, parotid and cervical lymph nodes through vascular anastomosis
Radiology images

AFIP images

Normal eye and orbital contents
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MR #1 (T1 weighted)

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MR #2 (T2 weighted)

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MR #3 (T1 weighted) shows coronal section
of orbital contents posterior to globe

Drawings

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Lacrimal apparatus

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Lens

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Optic nerve

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Orbit


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Extraocular muscles in orbit

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Cross section

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Globe

Microscopic (histologic) description
  • Anterior but not posterior lens has single epithelial layer
Microscopic (histologic) images

AFIP images
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Glandular lobule next to ducts
lined by pseudostratified
epithelium with goblet cells

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Lobule of acinic and mucinous cells

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Intraocular and orbital portions of optic nerve

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Cross section of optic nerve parenchyma and meninges



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Lens

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Optic nerve and fovea centralis

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