Patho chapter 15

Glaucoma

is a disease of increased intraocular pressure, over time the pressure builds up and compresses the retinal cells, which injures them and produces blindness.

Chronic Glaucoma

Insidious onset, peripheral fields are lost first and can be ignored and compensated for because it is usually mild and slow in progression, so they are able to do things like turn their head in different ways

Acute Glaucoma

More acute and sudden, people who are anatomically predisposed to getting this condition experience a sudden change in pupillary size and subsequently the angle between the lense and the iris. This can be from medicines that change the size of the pupil, spending prolonged time in a very dark room.

Cataract

occurs when the normally clear lens becomes cloudy and interferes with light transmission. The size, site, and density of the opacity/cloudiness vary among individuals and may differ between a single individual’s two eyes. The changes may be caused by degeneration related to aging or metabolic abnormalities such as diabetes. Excessive exposure to sunlight may be a factor. Congenital cataracts are usually a result of maternal infection attributed to rubella or toxoplasmosis. Traumatic cataracts are the result of blows to the eye, which imprint iris pigment on the lens. These injuries are often associated with sports activities in which eye protection is not used. Blurred vision that gradually darkens is the main sign of cataracts, and it may progress at different rates in each eye. When vision loss affects daily function, the cloudy lens can be removed and replaced with an artificial intraocular lens. Tests are done beforehand to check retinal function, eye pressure, and rule out other issues like tumors. Cataract surgery is typically an outpatient procedure using phacoemulsification to break up and remove the lens, followed by placement of the new lens. A peripheral iridectomy may be done to prevent glaucoma after surgery.

Macular Degeneration

Age-related macular degeneration (AMD) is a common cause of visual loss in older persons. It appears to arise from a combination of genetic factors and environmental exposure (e.g., ultraviolet rays and drugs). A similar condition found in younger persons has a stronger genetic basis. Degeneration occurs at the fovea centralis in the macula lutea, with its high density of cones, at the central point of the retina. There are two types of degeneration: The more common type is the dry or atrophic AMD, in which deposits form in retinal cells, gradually destroying them. In the wet or exudative form, neovascularization occurs, with the formation of abnormal, leaky blood vessels, rapidly destroying the retina. In both types, nutrients can no longer pass from the choroids to the retina. Central vision with high acuity first becomes blurred and then is lost. There is no treatment to reverse the effects. Depth perception is also affected. There is no pain. Peripheral vision is not affected. Visual field tests and angiography assist diagnosis.

Dethatched Retina:

An acute problem that occurs when the retina tears away from the underlying choroid because of marked myopia, degeneration with aging, or scar tissue that creates tension on the retina. The tear allows vitreous humor to flow behind the loose retinal portion. As increased vitreous humor continues to seep behind the retina, an increasing portion of the retina is lifted away from the choroid. The retinal cells cease to function as they are deprived of nutrients diffusing from the blood vessels of the choroid. This loss of function results in an area of blackness in the visual field. If separation continues, the retina is deprived of its source of nutrients in the choroid and dies.

There is no pain related to the tear, but initially the patient may see light or dark floating spots in the visual field, resulting from blood or exudate leaking from the tear. A darkened or blind area develops that increases in size with time. Typically, this event has been described as a “dark curtain” drawn across the visual field.

Surgical intervention such as scleral buckling or laser therapy is required as soon as possible to close any holes and reattach the retina in its proper position against the choroid to restore the source of nutrients to the retinal cells before irreversible damage occurs. Retinal detachment may recur and requires immediate attention to prevent vision loss.

Osteosclerosis

involves an imbalance in bone formation and resorption. With development of excess bone in the middle ear cavity, the stapes becomes fixed to the oval window, blocking conduction of sound into the cochlea. Otosclerosis appears to develop from a genetic factor, primarily in young adult females. Surgical removal of the stapes (stapedectomy) and replacement by a prosthesis restores hearing. If laser surgery is used in an early stage, the stapes may be freed, and no prosthesis is required.

Meniere’s Disease

is an inner ear or labyrinth disorder occurring in adults 30 to 50 years of age. It usually affects only one ear. Excessive endolymph develops intermittently, stretching the membranes and interfering with the function of the hair cells in the cochlea and vestibule. Rupture of the labyrinth membrane may allow perilymph to mix with endolymph, increasing volume and causing an attack. The increased fluid may also be of vascular origin. Each attack may last minutes or hours and causes the following conditions:

Severe vertigo: a sensation of whirling and weakness, is often accompanied by loss of balance and falls

Tinnitus (excess noise like a roaring motor or ringing)

Unilateral hearing loss

Nausea and sweating

Inability to focus

Nystagmus: an involuntary, rapid movement of the eyeball

A feeling of pressure in the ear.