Eye

Illustration of the eye. (Gray's Anatomy/WC)

Micrograph showing the optic nerve head and retina. H&E stain. (WC)

The eye is rarely seen by pathologists. Typically, they go to neuropathologists, as the eye is really part of the brain. The article also covers many of the lesions found around the eye. The lacrimal gland is covered in the lacrimal gland article. Eyelid lesions are covered in the eyelid article.

An introduction to neuropathology is in the neuropathology article.

Procedures

• Evisceration - eye muscles left intact.
• Enucleation.
• Exenteration - extensive resection.

Anatomy

Anterior to posterior

1. Cornea.
2. Iris.
3. Lens.
4. Conjunctiva - edge of cornea.
5. Sclera.
   • Similar to cornea - normally has blood vessels.

Optic nerve

• Surrounded by CSF.
• Covered by dura.

Inside to outside

1. Retina.
2. Retinal pigment epithelium (RPE).
3. Choroid.
4. Sclera.

Image

• 

  Optic nerve head and retina - low mag. (WC)

Anterior angle

• Angle between cornea and iris.

Histology

Eye muscles

• The muscles that move the eye have a high nerve:muscle ratio = ~1:4.
  • Other muscles in the body ~1:250.

Conjunctiva

Features:

• Stratified squamous.
  • May be stratified columnar
• Goblet cells.

Cornea

Layers:

1. Epithelium layer.
   • Squamoid cells.
2. Bowman's layer.
   • Indistinct.
3. Stroma.
   • Fibrous tissue.
   • No blood vessels.
4. Descemet’s layer.
   • Indistinct.
   • PAS -ve.
5. Endothelium.
   • Single layer.

Retina

Simplified structure - eosinophilic material separating:

1. Intermediate size, round, pale-staining nuclei (ganglion cells).
2. Two layers of small round nuclei (inner and outer nuclear layer).
3. Eosinophilic ellipsoid structures - rods/cones (photoreceptors).
4. Single layer of cuboidal cells (retinal pigment epithelium.

Detailed structure - in direction light travels:

1. Inner limiting membrane.
2. Nerve fibre layer.
3. Ganglion layer.
4. Inner plexiform layer.
5. Inner nuclear layer.
6. Outer plexiform layer.
7. Outer nuclear layer.
8. Layer of rods and cones.
9. External limiting membrane.
10. Retinal pigment epithelium.

Images

• 

  Retina - schematic. (WC/Gray's)

www:

• Retina - histology (surgical-pathology.com).
• Histology of the eye (clc.uc.edu).

Eye structures with melanocytes

Melanoma may arise from these sites:

• Iris.
• Conjunctiva.
• Ciliary bodies.
• Choroid.

Benign entities

Conjunctivitis

General

• Benign.
• Never biopsied.
  • It is an incidental finding in a biopsy for something else.

Gross

• Red eye.

Microscopic

Features:

• Conjunctival epithelium - stratified squamous epithelium with goblet cells.
• Inflammatory cells.

Conjunctival cyst

Conjunctival cyst
External resources
EHVSC	10173

General

• Rare.
• May be due to surgery, trauma, or congenital (very rare).

Microscopic

Features:

• Conjunctival mucosa with atypia.
  • Stratified squamous epithelium with goblet cells.

DDx:

• Ocular surface squamous neoplasia.
  • Cystic squamous cell carcinoma.

Image:

• Conjunctival cyst (nih.gov).

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CONJUNCTIVA, RIGHT SUPERIOR, BIOPSY:
- BENIGN CONJUNCTIVAL MUCOSA -- COMPATIBLE WITH CYST LINIG.

Pinguecula

• Plural Pingueculae.

General

• Raizada et al. suggest it is an early pterygium; however, this is disputed.
• Due to ultraviolet light exposure, e.g. sunlight.
• Tend to be older than individuals afflicted with a pterygium.

Gross

• Yellow spot.

Microscopic

Features:

• Similar to pterygium.

Pterygium

• AKA surfer eye.

Main article: Pterygium

Eccrine hidrocystoma

• Occasionally spelled eccrine hydrocystoma.

General

• Benign.
• Eyelid lesion.

Clinical DDx:

• Cystic BCC.

Microsopic

Features:

• Cyst lined by a bland bilayer.
  • Inner lining cells have:
    • Small, round nuclei - usu. basal.
    • Moderate pale/greyish cytoplasm.
    • No apocrine snouts - flat surface.
  • Outer lining cells - spindled.
    • May be difficult to see.

Note:

• According to the CMAJ, it has the histology of an epidermal inclusion cyst.

DDx:

• Apocrine hidrocystoma - have apocrine snouts; surface is not flat.
• Cystadenoma - has epithelial proliferation.

Image

• 

  Apocrine hidrocystoma (AH). AH looks similar to eccrine hidrocystoma. (WC)

www:

• Eccrine hidrocystoma (nature.com).
• Apocrine hidrocystoma (dermnet.org).
• Apocrine hidrocystoma (flickr.com).

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SKIN LESION, ADJACENT TO RIGHT EYELID, EXCISION:
- ECCRINE HIDROCYSTOMA.

Micro

The sections show hair bearing skin with a cyst lined by a bland bilayered epithelium. The predominant lining cell has moderate pale grey cytoplasm and a small round nucleus.

The lesion is excised in the plane of section.

Chalazion

Main article: Chalazion

Retinal hemorrhage

See Traumatic brain injury in infants.

Image:

• Retinal haemorrhage (med.utah.edu).

Glaucoma

General

• Leading cause of irreversible blindness.

Classification:

• Open angle - more common.
• Closed angle.

Microscopic

Features (closed angle):

• Cornea and iris opposed to one another.

Retinal detachment

General

• Blindness.

Causes:

• Trauma (classic) - pathologist doesn't usually see.
• Tumours - common in pathology specimens.

Microscopic

Features:

• Retina separated from retinal pigment epithelium.
• Eosinophilic exudate containing macrophages.

Blepharochalasis

General

• Rare, benign eyelid disorder.
• Upper eyelids +/-lower eyelids (severe cases).

Clinical:

• Swelling of eyelids - recurrent.
• Onset in childhood.
• Leads to ptosis.

Clinical DDx:

• Recurrent angioedema.
• Hereditary angioedema.
• Contact dermatitis.
• Melkersson-Rosenthal syndrome.
• Dermatochalasis.
• Floppy-eyelid syndrome.
• Lax eyelid syndrome.
• Cutis laxa.

Note:

• The term may be abused; it may be used when an eyelid tuck is done for other reasons.^{[citation needed]}

Microscopic

Features:

• Edema.

DDx:

• Angioedema.

Stains

• Elastin stain - shows loss of elastin.

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EYELID, LEFT UPPER, PTOSIS REPAIR:
- SQUAMOUS EPITHELIUM WITHIN NORMAL LIMITS.
- SUBEPITHELIAL TISSUE WITH MILD EDEMA.
- SOLAR ELASTOSIS.
- NEGATIVE FOR MALIGNANCY.

Lower eyelids in an older individual labelled blepharochalasis

A. EYELID, LEFT LOWER, BLEPHAROPLASTY:
- BENIGN SKIN WITH MILD SOLAR ELASTOSIS.
- BENIGN SKELETAL MUSCLE AND ADIPOSE TISSUE.
- NEGATIVE FOR MALIGNANCY.

B. EYELID, RIGHT LOWER, BLEPHAROPLASTY:
- BENIGN SKIN WITH MILD SOLAR ELASTOSIS.
- BENIGN SKELETAL MUSCLE AND ADIPOSE TISSUE.
- NEGATIVE FOR MALIGNANCY.

Papilloma of the caruncle

• AKA caruncle papilloma.

General

• Benign.
• Second most common caruncle tumour ~ 15% of caruncle tumours.
  • Most common is nevus ~ 50% of caruncle tumours.

Gross

• Frond-like lesion.

Image:

• Papilloma of caruncle (atlasophthalmology.com).

Microscopic

Features:

• Fibrovascular fronds in a cauliflower-like arrangement.
• No nuclear atypia.

Image:

• Papilloma of caruncle - crappy image (atlasophthalmology.com).

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LESION, RIGHT CARUNCLE, EXCISION:
- PAPILLOMA.
- NEGATIVE FOR MALIGNANCY.

Micro

The sections show benign conjunctival mucosa and a lesion consisting of fibrovascular cores covered by a conjunctival epithelium with a cauliflower-like appearance at low power. Parakeratosis is present. No significant nuclear atypia is identified. No koilocytic change is seen. No mitotic activity is appreciated.

External links

• Conjunctival papilloma (eyewiki.aao.org).

Malignant entities

Retinoblastoma

General

• Rare.
• Malignant.
• May be familial.

Gross

• White, solid.
• Patterns:
  • Endophytic - grow into the vitreous cavity.
  • Exophytic - grow toward choroid.
  • Mixed - components of endophytic and exophytic.

Image:

• Retinoblastoma (radiopaedia.org/AFIP).

Note:

• Tumour is extremely friable.

Microscopic

Features:

• Small round cell tumour:
  • Scant cytoplasm.
• Flexner-Wintersteiner rosette - key feature.
  • Rosette with empty centre (donut hole).
• +/-Homer-Wright rosette.
  • Circular rosette with neuropil at the centre.
• Mitoses - common.
• +/-Necrosis.
• +/-Calcification.

DDx:

• Retinocytoma (retinoma) - benign counterpart of retinoblastoma.

Notes:

• DDx of Flexner-Wintersteiner rosette includes:
  • Pineoblastoma.
  • Medulloepithelioma.

Image:

• Retinoblastoma (ouhsc.edu).
• Retinoblastoma (pathpedia.com).

Malignant melanoma

Main article: Malignant melanoma

Common malignancy in the eye in adults.

See also

• CNS tumours.
• Hypertension.
• Lacrimal gland.
• Neuropathology.
• Descemet's membrane.