Eye Disorders

It is important to understand the anatomy of the eye prior to doing an examination.

Loss of vision is usually considered acute if it develops within a few minutes to a couple of days. It may affect one or both eyes and all or part of a visual field. Patients with small visual field defects (eg, caused by a small retinal detachment) may describe their symptoms as blurred vision.

A cataract is a congenital or degenerative opacity of the lens. The main symptom is gradual, painless vision blurring. Diagnosis is by ophthalmoscopy and slit-lamp examination. Treatment is surgical removal and placement of an intraocular lens.

Blepharitis is inflammation of the eyelid margins that may be acute or chronic. Symptoms and signs include itching and burning of the eyelid margins with redness and edema. Diagnosis is by history and examination. Acute ulcerative blepharitis is usually treated with topical antibiotics or systemic antivirals. Acute nonulcerative blepharitis is occasionally treated with topical corticosteroids. Chronic disease is treated with tear supplements, warm compresses, and occasionally oral antibiotics (eg, a tetracycline) for meibomian gland dysfunction or with eyelid hygiene and tear supplements for seborrheic blepharitis.

The conjunctiva lines the back of the eyelids (palpebral or tarsal conjunctiva), crosses the space between the lid and the globe (forniceal conjunctiva), then folds back on itself as it spreads over the sclera to the cornea (bulbar conjunctiva). The conjunctiva contributes to the tear film and protects the eye from foreign objects and infection.

Symptoms that suggest corneal involvement (eg, rather than simple conjunctivitis) include unilateral involvement, pain (foreign body sensation and ache—not just a gritty sensation), particularly with exposure to light (photophobia), and decreased visual acuity.

Glaucomas are a group of eye disorders characterized by progressive optic nerve damage in which an important part is a relative increase in intraocular pressure (IOP) that can lead to irreversible loss of vision.

Eye irrigation is used to flush particles and harmful chemicals from the conjunctiva and cornea. Eyelid eversion is used to expose the superior palpebral conjunctiva and fornix, so that foreign matter can be identified in these areas.

The optic pathway includes the retina, optic nerve, optic chiasm, optic radiations, and occipital cortex (see figure Higher visual pathways). Damage along the optic pathway causes a variety of visual field defects. The type of field defect can help localize the lesion (see table Types of Field Defects).

Cavernous sinus thrombosis is a very rare, typically septic thrombosis of the cavernous sinus, usually caused by nasal furuncles or bacterial sinusitis. Symptoms and signs include pain, proptosis, ophthalmoplegia, vision loss, papilledema, and fever. Diagnosis is confirmed by CT or MRI. Treatment is with IV antibiotics. Complications are common, and prognosis is guarded.

In the emmetropic (normally refracted) eye, entering light rays are focused on the retina by the cornea and the lens, creating a sharp image that is transmitted to the brain. The lens is elastic, more so in younger people. During accommodation, the ciliary muscles adjust lens shape to properly focus images. Refractive errors are failure of the eye to focus images sharply on the retina, causing blurred vision (see figure Errors of refraction).

Age-related macular degeneration (AMD) is the most common cause of irreversible central vision loss in older patients. Dilated funduscopic findings are diagnostic; color photographs, fluorescein angiography, and optical coherence tomography assist in confirming the diagnosis and in directing treatment. Treatment is with dietary supplements, intravitreal injection of antivascular endothelial growth factor drugs, laser photocoagulation, photodynamic therapy, and low-vision devices.

Uveitis is defined as inflammation of the uveal tract—the iris, ciliary body, and choroid. However, the retina and fluid within the anterior chamber and vitreous are often involved as well. About half of cases are idiopathic; identifiable causes include trauma, infection, and systemic diseases, many of which are autoimmune. Symptoms include decreased vision, ocular ache, redness, photophobia, and floaters. Although uveitis is identified clinically, identifying the cause typically requires testing. Treatment depends on cause, but typically includes topical, locally injected, or systemic corticosteroids with a topical cycloplegic-mydriatic drug. Noncorticosteroid immunosuppressive drugs may be used in severe and refractory cases.