CHAPTER 029. DISORDERS OF THE EYE (PART 12) PPT

Chapter 029. Disorders of the Eye (Part 12) Papilledema This connotes bilateral optic disc swelling from raised intracranial pressure (Fig. 29-12). Headache is a frequent, but not invariable, accompaniment. All other forms of optic disc swelling, e.g., from optic neuritis or is[r]

Chapter 029. Disorders of the Eye (Part 1) Harrison's Internal Medicine > Chapter 29. Disorders of the Eye The Human Visual System The visual system provides a supremely efficient means for the rapid assimilation of information from the environment to aid in the guidance of behavior.[r]

Chapter 029. Disorders of the Eye (Part 14) Stroke This occurs when interruption of blood supply from the posterior cerebral artery to the visual cortex is prolonged. The only finding on examination is a homonymous visual field defect that stops abruptly at the vertical meridian. Occipital l[r]

Chapter 029. Disorders of the Eye (Part 10) Central retinal artery occlusion combined with ischemic optic neuropathy in a 19-year-old woman with an elevated titer of anticardiolipin antibodies. Note the orange dot (rather than cherry red) corresponding to the fovea and the spared patch of re[r]

Chapter 029. Disorders of the Eye (Part 19) Myogenic Ptosis The causes of myogenic ptosis include myasthenia gravis (Chap. 381) and a number of rare myopathies that manifest with ptosis. The term chronic progressive external ophthalmoplegia refers to a spectrum of systemic diseases caused by[r]

Chapter 029. Disorders of the Eye (Part 18) Orbital Cellulitis This causes pain, lid erythema, proptosis, conjunctival chemosis, restricted motility, decreased acuity, afferent pupillary defect, fever, and leukocytosis. It often arises from the paranasal sinuses, especially by contiguous spr[r]

Chapter 029. Disorders of the Eye (Part 17) Melanoma and Other Tumors Melanoma is the most common primary tumor of the eye (Fig. 29-18). It causes photopsia, an enlarging scotoma, and loss of vision. A small melanoma is often difficult to differentiate from a benign choroidal nevus. Serial e[r]

Chapter 029. Disorders of the Eye (Part 16) Central Serous Chorioretinopathy This primarily affects males between the ages of 20 and 50. Leakage of serous fluid from the choroid causes small, localized detachment of the retinal pigment epithelium and the neurosensory retina. These detachment[r]

Chapter 029. Disorders of the Eye (Part 22) Horizontal Gaze Descending cortical inputs mediating horizontal gaze ultimately converge at the level of the pons. Neurons in the paramedian pontine reticular formation are responsible for controlling conjugate gaze toward the same side. They proje[r]

Chapter 029. Disorders of the Eye (Part 23) Parinaud's Syndrome Also known as dorsal midbrain syndrome, this is a distinct supranuclear vertical gaze disorder from damage to the posterior commissure. It is a classic sign of hydrocephalus from aqueductal stenosis. Pineal region tumors, cystic[r]

Chapter 029. Disorders of the Eye (Part 8) Episcleritis This is an inflammation of the episclera, a thin layer of connective tissue between the conjunctiva and sclera. Episcleritis resembles conjunctivitis but is a more localized process and discharge is absent. Most cases of episcleritis ar[r]

Chapter 029. Disorders of the Eye (Part 9) Endophthalmitis This occurs from bacterial, viral, fungal, or parasitic infection of the internal structures of the eye. It is usually acquired by hematogenous seeding from a remote site. Chronically ill, diabetic, or immunosuppressed patients, espe[r]

Chapter 029. Disorders of the Eye (Part 21) Abducens Nerve The sixth cranial nerve innervates the lateral rectus muscle. A palsy produces horizontal diplopia, worse on gaze to the side of the lesion. A nuclear lesion has different consequences, because the abducens nucleus contains interneur[r]

Chapter 029. Disorders of the Eye (Part 20) Oculomotor Nerve The third cranial nerve innervates the medial, inferior, and superior recti; inferior oblique; levator palpebrae superioris; and the iris sphincter. Total palsy of the oculomotor nerve causes ptosis, a dilated pupil, and leaves the[r]

Chapter 029. Disorders of the Eye (Part 11) Posterior Ischemic Optic Neuropathy This is an infrequent cause of acute visual loss, induced by the combination of severe anemia and hypotension. Cases have been reported after major blood loss during surgery, exsanguinating trauma, gastrointestin[r]

Chapter 029. Disorders of the Eye (Part 3) Demonstration of a relative afferent pupil defect (Marcus Gunn pupil) in the left eye, done with the patient fixating upon a distant target. A. With dim background lighting, the pupils are equal and relatively large. B. Shining a flashlight into the[r]

Chapter 029. Disorders of the Eye (Part 4) Stereopsis Stereoacuity is determined by presenting targets with retinal disparity separately to each eye using polarized images. The most popular office tests measure a range of thresholds from 800–40 seconds of arc. Normal stereoacuity is 40 secon[r]

Chapter 029. Disorders of the Eye (Part 5) Ventral view of the brain, correlating patterns of visual field loss with the sites of lesions in the visual pathway. The visual fields overlap partially, creating 120° of central binocular field flanked by a 40° monocular crescent on either side. T[r]

Chapter 029. Disorders of the Eye (Part 6) Red or Painful Eye Corneal Abrasions These are seen best by placing a drop of fluorescein in the eye and looking with the slit lamp using a cobalt-blue light. A penlight with a blue filter will suffice if no slit lamp is available. Damage to the cor[r]

Chapter 029. Disorders of the Eye (Part 7) Allergic Conjunctivitis This condition is extremely common and often mistaken for infectious conjunctivitis. Itching, redness, and epiphora are typical. The palpebral conjunctiva may become hypertropic with giant excrescences called cobblestone papi[r]