Age-Related Macular Degeneration (AMD)

• Vision is a major quality-of-life issue, with blindness being the second most feared disease among Americans, after cancer and before AIDS and Alzheimer's awareness.
• Diseases causing vision loss may not receive as much attention as life-threatening conditions.
• Age-related macular degeneration (AMD) is the most common cause of irreversible visual loss in the U.S.
• AMD does not usually cause total vision loss (immersion into darkness).
• AMD involves small scars in the macula, leading to loss of central vision.
• AMD can significantly impact a person's independence and quality of life, affecting abilities like reading and driving.
• Ocular pathology allows direct visualization of microcirculatory disturbances like arteriosclerosis and angiogenesis.
• The eye is unique in that it facilitates the direct visualization of a variety of microcirculatory disturbances.
• Many ocular conditions share similarities with disease processes elsewhere in the body, modified by the eye's structure and function.
• Molecular pathogenesis elucidation has rapidly led to therapeutic applications in the eye.
• Pathologic angiogenesis contributes to corneal neovascularization, diabetic retinopathy, and some forms of age-related neovascularization.
• VEGF antagonists have been successful in saving vision in patients with these conditions.
• The chapter is organized by ocular anatomy, beginning with anatomic and functional considerations and their impact on disease understanding.

Orbit

• The orbit is a closed compartment, so diseases increasing orbital contents cause proptosis (forward displacement of the eye).
• Proptosis can lead to cosmetic concerns and corneal exposure, causing pain, ulceration, and infection.
• Proptosis can be axial (directly forward) or positional.
• Enlargement of the lacrimal gland displaces the eye inferiorly and medially.
• Masses within the cone of horizontal rectus muscles cause axial proptosis.
• Glioma and meningioma of the optic nerve produce axial proptosis.

Thyroid Ophthalmopathy (Graves Disease)

• Axial proptosis is a clinical manifestation of Graves disease.
• Proptosis in Graves disease is caused by extracellular matrix protein accumulation and fibrosis in the rectus muscles.
• Thyroid ophthalmopathy development can be independent of thyroid function status in some cases.

Other Orbital Inflammatory Conditions

• Uncontrolled sinus infection can spread to the orbit, especially in immunosuppressed individuals or those with diabetic ketoacidosis.
• Systemic conditions like granulomatosis with polyangiitis can present in the orbit.
• Idiopathic orbital inflammation (orbital inflammatory pseudotumor) can be unilateral or bilateral.
• Idiopathic orbital inflammation can affect all orbital tissue or be confined to certain areas like the lacrimal gland (sclerosing dacryoadenitis), extraocular muscles (orbital myositis), or Tenon capsule (posterior scleritis).
• IgG4-related disease should be excluded before diagnosing idiopathic orbital inflammation.

Morphology

• Idiopathic orbital inflammation is characterized by chronic inflammation and variable fibrosis.
• The inflammatory infiltrate includes lymphocytes, plasma cells, and sometimes eosinophils.
• Germinal centers suggest reactive lymphoid hyperplasia.
• Vasculitis may be present, indicating an underlying systemic condition.
• Necrosis, degenerating collagen, and vasculitis raise suspicion of granulomatosis with polyangiitis.
• Idiopathic orbital inflammation is usually confined to the orbit but may occur with sclerosing inflammation in other areas, especially as a manifestation of IgG4-related disease.