Human Diseases & Conditions Ch 5

Optic Nerve

The optic nerve is the second cranial nerve and is responsible for vision. Each nerve contains approx. one million fibres transmitting information from the rod and cone cells of the retina.

Papilla

The papilla is also known as the "blind spot" and is located at the position from which the optic nerve leaves the retina

Pupil

The pupil is the aperture through which light - and hence the images we "see" and "perceive" - enters the eye. This is formed by the iris. As the size of the iris increases (or decreases) the size of the pupil decreases (or increases) correspondingly

Retina

The retina may be described as the "screen" on which an image is formed by light that has passed into the eye via the cornea, aqueous humour, pupil, lens, then the hyaloid and finally the vitreous humour before reaching the retina. The retina contains photosensitive elements (called rods and cones) that convert the light they detect into nerve impulses that are then sent onto the brain along the optic nerve.

Sclera

The sclera is a tough white sheath around the outside of the eye-ball. This is the part of the eye that is referred to by the colloquial terms "white of the eye".

Vitreous Humour

The vitreous humour (also known as the "vitreous body") is a jelly-like substance.

Zonules

The zonules (or "zonule fibers") attach the lens to the ciliary muscles.

Visual Axis

A simple definition of the "visual axis" is "a straight line that passes through both the centre of the pupil and the centre of the fovea". However, there is also a stricter definition (in terms of nodal points) which is important for specialists in optics and related subjects.

Ruptured tympanic membrane (ruptured eardrum)

Any type of tear or injury to the eardrum causes a breach in the integrity of the may be the result of pressure, force, or insult from the exterior aspect, or it may be caused by increasing pressure within the middle ear.

How does the aging process affect the eyes and ears?

As you age, structures inside the ear start to change and their functions decline. Your ability to pick up sounds decreases. You may also have problems maintaining your balance as you sit, stand, and walk. Age-related hearing loss is called presbycusis. It affects both ears. Hearing, especially of high-frequency sounds, may decline. You may also have trouble telling the difference between certain sounds. Or, you may have problems hearing a conversation when there is background noise. If you are having trouble hearing, discuss your symptoms with your health care provider. One way to manage hearing loss is by getting fitted with hearing aids. All of the eye structures change with aging. The cornea becomes less sensitive, so you might not notice eye injuries. By the time you turn 60, your pupils may decrease to about one third of the size they were when you were 20. The pupils may react more slowly in response to darkness or bright light. The lens becomes yellowed, less flexible, and slightly cloudy. The fat pads supporting the eyes decrease and the eyes sink into their sockets. The eye muscles become less able to fully rotate the eye. As you age, the sharpness of your vision (visual acuity) gradually declines. The most common problem is difficulty focusing the eyes on close-up objects. This condition is called called presbyopia. Reading glasses, bifocal glasses, or contact lenses can help correct presbyopia. You may be less able to tolerate glare. For example, glare from a shiny floor in a sunlit room can make it difficult to get around indoors. You may have trouble adapting to darkness or bright light. Problems with glare, brightness, and darkness may make you give up driving at night. As you age, it gets harder to tell blues from greens than it is to tell reds from yellows. Using warm contrasting colors (yellow, orange, and red) in your home can improve your ability to see. Keeping a red light on in darkened rooms, such as the hallway or bathroom, makes it easier to see than using a regular night light.

Astigmatism

Astigmatism usually occurs when the front surface of the eye, the cornea, has an asymmetric curvature. Normally the cornea is smooth and equally curved in all directions, and light entering the cornea is focused equally on all planes, or in all directions. In astigmatism, the front surface of the cornea is curved more in one direction than in another. This abnormality may result in vision that is much like looking into a distorted, wavy mirror. Usually, astigmatism causes blurred vision at all distances.

How do neoplasms affect the eye?

Cancer the eye may involve the globe (ocular tumors), the orbit (the bone surrounding the orbital cavity and the soft tissues and muscles that lie between the globe and the bone), the optic nerve, or the eyelids. Neoplasms may be benign, malignant, or metastatic from another location (secondary tumors).

What are the common symptoms associated with ear disorders?

Common symptoms of ear diseases and conditions include: -Hearing loss -Ear pain or pressure -Tinnitus (ringing or buzzing noise) -Vertigo (dizziness) -Nausea and vomiting

What disorders affect the globe of the eye?

Corneal abrasion or ulcer: Corneal abrasion is the painful loss of surface epithelium or outer layer of the cornea. A corneal ulceration is an infection of the cornea. Episcleritis/Scleritis: inflammation of the episclera (the external surface of the sclera) is episclera ties; inflammation of the deeper sclera, the white outermost covering of the eyeball, is called scleritis. Episclera tie occurs far more commonly than scleritis. Cataract: Cataract is when the natural lens of the eye becomes opacified. Glaucoma: is damage to the optic nerve in the presence of elected intraocular pressure. Macular degeneration: is a progressive deterioration or breakdown of the macula of the retina. Diabetic Retinopathy: is a pathologic alterations of the retinal blood vessels and the pathologic proliferation of the retinal vessels. Retinal detachment: a retinal detachment is an elevation (separation) of the retina from the choroid. Uveitis: denotes inflammation of the uveal tract, including the iris, ciliary body, and choroid. Exophthalmos: is an abnormal protrusion of the eyeballs.

What disorders affect the normal function of the eyelid? How?

Hordeolum (Stye): Acute focal inflammatory infections of the sebaceous glands of the eyelids. Chalazion: small, firm, nonmobile, painless, subcutaneous nodule on the margin or body of the eyelid; It occurs with occlusion of the meibomian glands. Keratitis: is any inflammation or infection of the cornea. Blepharitis: is an inflammation of the margins of the eyelids involving hair follicles and glands. Entropion: in the case of entropion, the eyelid margins turn inward, (specifically the lower lid) causing the lashes to rub the conjunctiva. Ectropion: is a condition in which the lower eyelid everts from the eyeball, and the exposed surface of the eyeball and the lining of the eyelid become dry and irritated. Conjunctivitis: inflammation of the conjunctiva, the mucous membrane that covers the anterior portion of the eyeball and also lines the eyelids. Blepharoptosis: also called ptosis is a permanent drooping of the upper eyelid. Which can partially or completely cover the eye.

Hyperopia

Hyperopia (close objects are more blurry than distant objects) Also known as farsightedness, hyperopia can also be inherited. Children often have hyperopia, which may lessen in adulthood. In mild hyperopia, distance vision is clear while near vision is blurry. In more advanced hyperopia, vision can be blurred at all distances.

Identify the disorders of the ear associated with conduction.

Impacted Cerumen (ear wax): an atypical accumulation of the Cerumen in the canal f the outer ear. The "ear wax" that has accumulated hardens and has a tendency to prevent sound waves from reaching the tympanic membrane (eardrum) resulting in decreased hearing. Infective Otitis Externa: inflammation of the external ear canal is called otitis Externa. This condition is usually accompanied by an infectious process. Swimmers ear: inflammation and resulting infection of the outer ear canal after water has been entrapped during swimming is termed swimmer's ear. Otitis media: is inflammation of the normally air-filled middle ear with the accumulation of fluid behind the tympanic membrane (eardrum), occurring unilaterally or bilaterally. Osteosclrosis: an abnormal bone growth in in the middle ear, primarily affects the stapes, the third bone or ossicle of the middle ear, as the individual ages. Movement of the ossicles is impaired, which causes dismissed conduction of sound waves and resulting hearing loss.

Sensorineural hearing loss

In Sensorineural hearing loss (deafness) also often referred to as occupational hearing loss, sound waves reach the inner ear but are not perceived because the nerve impulses are not transmitted to the brain.

Menieres Disease

Is a chronic disease of the inner ear that affects the Labyrinth.

Cholesteatoma

Is a pocket of skin cells located in the middle ear, normally shred by the eardrum, that collects into a cystlike mass or ball and becomes infected. As the infected material accumulates the bone lining of the idle ear cavity erodes and the ossicles become damaged.

Labryrinthitis

Is an inflammation or infection of the labyrinth of the inner ear.

Benign Paroxysmal positional vertigo (BPPV)

Is usually a vestibular system disorder. The patient complains of his/her head spinning, becoming worse with movement of the head. Complaints of feeling that their surroundings are moving.

Cornea

Light is focused primarily by the cornea — the clear front surface of the eye, which acts like a camera lens. The cornea is a strong clear bulge located at the front of the eye (where it replaces the sclera - that forms the outside surface of the rest of the eye). The front surface of the adult cornea has a radius of approximately 8mm. The cornea contributes to the image-forming process by refracting light entering the eye.

Myopia

Myopia(close objects are clear, and distant objects are blurry) Also known as nearsightedness, myopia is usually inherited and often discovered in childhood. Myopia often progresses throughout the teenage years when the body is growing rapidly.

What parts of the ear are affected? How are conduction disorders different from ototoxicity?

Outer ear, inner ear, external ear. All parts of the ear are affected. Ototoxicity is the property of being toxic to the ear (oto-), specifically the cochlea or auditory nerve and sometimes the vestibular system, for example, as a side effect of a drug. Conduction and Ototoxicity are different because Ototoxicity are conditions caused due to drug medications and conduction is not.

Iris

The iris is a diaphragm of variable size whose function is to adjust the size of the pupil to regulate the amount of light admitted into the eye. The iris is the coloured part of the eye (illustrated in blue above but in nature may be any of many shades of blue, green, brown, hazel, or grey.

Lens

The lens of the eye is a flexible unit that consists of layers of tissue enclosed in a tough capsule. It is suspended from the ciliary muscles by the zonule fibers

Identify the types of Refractive errors?

The main types of refractive errors are myopia (nearsightedness), hyperopia (farsightedness), presbyopia (loss of near vision with age), and astigmatism.

Presbyopia

Presbyopia (aging of the lens in the eye) After age 40, the lens of the eye becomes more rigid and does not flex as easily. As a result, the eye loses its focusing ability and it becomes more difficult to read at close range. This normal aging process of the lens can also be combined with myopia, hyperopia or astigmatism.

Hyaloid

The hyaloid diaphragm divides the aqueous humour from the vitreous humour.

What are Refractive errors?

Refractive error means that the shape of your eye does not bend light correctly, resulting in a blurred image

Identify the normal anatomical structure of the ear.

The anatomy of the ear is composed of the following parts: External ear auricle(cartilage covered by skin placed on opposite sides of the head). auditory canal (also called the ear canal) eardrum outer layer (also called the tympanic membrane) Middle ear (tympanic): Malleus, incus, and stapes. Inner ear (labyrinthine): Semicircular canals, vestibule, cochlea. The ear is a multifaceted organ that connects the central nervous system to the external head and neck. This structure as a whole can be thought of as 3 separate organs that work in a collective to coordinate certain functions, such as hearing and balance. Any disharmony in this continuum may disrupt the ear's functionality. The outer part of the ear collects sound. Sound travels through the auricle and the auditory canal, a short tube that ends at the eardrum. THE MIDDLE EAR (TYMPANUM) The eardrum is a circle of thin skin about eight to nine millimetres (one-third of an inch) in diameter. The eardrum has three layers. The outer layer In contact with the deep ear canal, the outer layer is covered with a thin layer of skin. The inner layer The inner layer is in continuity with the lining of the middle ear, and consists of rather flat cells that have the ability to transform into the type of cells that line the nose and sinuses. Following infection, chemical irritation - such as tobacco smoke - or allergy, these cells alter and produce mucus which flows into the middle ear. The middle layer The middle layer of the eardrum is very important and consists of elastic fibres arranged both like the spokes of a wheel (radial fibres) and in circles (circumferential fibres), so that this layer is like a sprung trampoline net. THE INNER EAR (LABYRINTH) The inner ear is probably the most remarkably intricate piece of the body. It makes hearing possible by converting sound into electrical impulses that then travel along the hearing nerve (the acoustic nerve or auditory nerve) to the brain. The inner ear also plays a major role in balance.

Aqueous Humour

The aqueous humour is a jelly-like substance located in the anterior chamber of the eye

Choroid

The choroid layer is located behind the retina and absorbs unused radiation.

Ciliary Muscle

The ciliary muscle is a ring-shaped muscle attached to the iris. It is important because contraction and relaxation of the ciliary muscle controls the shape of the lens

What are the functions of the eyelid?

The eyelids serve to protect the eye from foreign matter, such as dust, dirt, and other debris, as well as bright light that might damage the eye. When you blink, the eyelids also help spread tears over the surface of your eye, keeping the eye moist and comfortable.

Fovea

The fovea is a small depression (approx. 1.5 mm in diameter) in the retina. This is the part of the retina in which high-resolution vision of fine detail is possible.

How do neoplasms affect the ear?

Tumors of the ear can occur in any part of the ear and may be benign or malignant. They include skin cancers of the external ear, ceruminal gland neoplasms, acoustic and facial neuromas, and glom us tumors. Many cancers from other locations in the body may metastasize to the ear, resulting in secondary ear cancer. Cancer of the ear is a rare cancer. Most of these cancers start in the skin of the outer ear. About 5 out of 100 skin cancers develop on the ear. Those that develop inside the ear are very rare. Less than 1 in every million people in the UK will develop cancer in the middle ear each year. Most cancers of the ear are squamous cell carcinomas. Other types include Basal cell cancer Melanoma Adenoid cystic Adenocarcinoma Back to top Causes of ear cancer: The cause of cancers in the middle ear is unknown. People with a history of chronic ear infections have a higher risk of developing cancer in the ear. Chronic means for 10 years or more. Symptoms of cancer of the ear The symptoms of cancer of the ear depend on where the tumour is within the ear. Some people may also have swollen lymph nodes in their neck. Middle ear - the most common symptom is a discharge from the ear which may be blood stained. Other symptoms include hearing loss and earache. Occasionally people cannot move their face on the side of the affected ear. Inner ear - pain including a headache, hearing loss, tinnitus and dizziness.

Mastoiditis

Whether acute or chronic is an inflammation of the mastoid bone, or mastoid process.