ISSN 2398-2942      

Eye: ocular manifestations of systemic disease

icanis

Synonym(s): Systemic disease and the eye


Introduction

  • A wide range of systemic diseases can affect the eye. Many infectious agents are more common in certain geographical locations, therefore knowledge of local diseases and a travel history are important.
  • Different areas of the eye are targets for different classes of diseases:
  • Eyelidsmay be affected by generalized skin disease, in particular that due to infectious, parasitic, neoplastic and autoimmune causes.
  • The conjunctivais rich in lymphatics and in local immune cells (plasma cells, mast cells, dendritic cells and macrophages) and therefore environmental irritants and allergens commonly cause conjunctivitis. In addition, its rich vascular network makes it a target for blood-borne disease. As a mucous membrane it is also a target for upper respiratory tract disease.
  • Third eyelidprotrusion may be a non-specific sign of generalized ill-health, occur secondary to chronic muscle wasting or dehydration, or appear as part of Horners syndrome Horner's syndrome , tetanus Tetanus , dysautonomia Dysautonomia , or Haws syndrome in cats.
  • The lacrimal glandis a target for autoimmune disease, so that immune-mediated keratoconjunctivitis sicca (KCS Keratoconjunctivitis sicca , dry eye) is seen commonly in conjunction with systemic diseases that may have an immune-mediated basis, such as hypothyroidism Hypothyroidism and diabetes mellitus Diabetes mellitus.
  • The corneamay develop corneal lipidosis secondary to diseases associated with hyperlipidemia Hyperlipidemia (eg hypothyroidism, pancreatitis, diabetes mellitus, primary hyperlipoproteinaemia). The cornea may also be affected by a number of the inherited lysosomal storage diseases, in which abnormal lysosomes accumulate within the corneal stroma to cause diffuse corneal clouding.
  • The anterior uvea(iris and ciliary body), with its rich vascular network, is a target for blood-borne disease (in particular infectious and neoplastic causes) and vascular disease (eg systemic hypertension).
  • The lensis affected by cataract Cataract , of which the most common systemic cause is diabetes mellitus. Cataract can also be caused by hypocalcemia Hypocalcemia (eg due to hypoparathyroidism).
  • The choroid and retinaare anatomically closely apposed, so that systemic disease affecting one will usually involve the other too. Examples include blood-borne infectious disease (bacterial, fungal, protozoal or viral infection causing chorioretinitis Chorioretinitis ), metastatic infiltration, immune-mediated disease, vascular disease (eg systemic hypertension Hypertension ), and nutritional disease (eg taurine deficiency in cats).
  • The optic nerveis not a true nerve but is really an extension of the brain, and as such is surrounded by cerebrospinal fluid (CSF) and meninges. It may become involved in diseases such as hydrocephalus Hydrocephalus , meningitis Meningitis , and brain tumors Brain: neoplasia. Specific infectious and inflammatory diseases may also target the optic nerve, causing optic neuritis Optic neuritis. Examples of this include canine distemper virus Canine distemper diseaseToxoplasma gondii Toxoplasma gondii , and granulomatous meningoencephalitis (GME) Granulomatous meningoencephalomyelitis.
  • Systemic neuropathiesmay involve the nerves of the eye and adnexa:
    • Cranial nerves that are involved in ocular function are II (optic; vision), III (oculomotor; pupil constriction, extraocular muscle function, upper eyelid elevation), IV (trochlear; extraocular muscle function), V (trigeminal; eyelid and corneal sensation), VI (abducens; globe retraction, extraocular muscle function), VII (facial; eyelid blink, parasympathetic supply to the lacrimal gland), and VIII (vestibulocochlear; vestibulo-ocular reflex).
    • Autonomic nerves also innervate the eye and may be affected in systemic disease:
      • Dysfunction of the sympathetic nerve supply to the eye will lead to Horners syndrome. This may be secondary to systemic neuropathy or due to a local defect of the sympathetic nerve supply as it travels from the hypothalamus to the eye via the spinal cord, brachial plexus, vagosympathetic trunk, middle ear and orbit.
      • The parasympathetic nerve supplies the lacrimal gland and the iris constrictor muscle. Dysfunction may lead to keratoconjunctivitis sicca or dilated and non-responsive pupils (internal ophthalmoplegia).

Specific systemic diseases causing ocular disease

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Further Reading

Publications

Refereed papers

Other sources of information

  • Cullen C L, Webb A A (2007) Ocular manifestations of systemic disease. Part 1: The dog. In: Veterinary Ophthalmology. 4th Edition. Ed KN Gelatt, Lippincott Williams and Wilkins, Philadelphia, 1470-1537.

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