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- 10.1
- 10.2
- 10.3
- 10.4
- 10.5
- 10.6
- 10.7
- 10.8
- 10.9
- 10.10
Historical and General Considerations
The eyes are the windows to the world. Most of the sensory input to the brain comes from the eyes. For centuries, the eye has been considered the essence of the person, representing the “I.” In mythology and the writings of ancient times, the eye is an organ associated with mystical powers.
The eye has long been associated with mythical gods. In ancient Egypt, the eye was the symbol of the Great Mother Goddess Maat, goddess of law, morality, and justice. The Egyptians believed that Maat held the universe together. The Eye of Maat later became known as the Eye of Horus. The Eye of Horus was believed to protect against all evil and to ensure success. The “evil eye” from the myth of Medusa was an expression of envy and greed. To this day, people wear talismans to ward off the “evil eye.”
Another interesting association is the subconscious linking of “eyeball” with male genitalia. Blindness can symbolize castration because testicles and eyeballs have the same shape and are important in the development of the sense of identity. This linking goes back to the legend of Oedipus, who pierced his eyeballs when he discovered that he had been married to his mother and had killed his father. This can be thought of as an act of self-castration, as well as a means of cutting oneself off from all worldly relationships. Throughout literature, the blinding of an individual was frequently a form of punishment for lust. The age-old notion that masturbation causes blindness further reinforces this close association of these organs.
Tumors in the eye are uncommon and are usually metastatic from breast, lung, bowel, or prostate cancer. Two types of primary tumors arise within the eye itself: retinoblastoma in children and melanoma in adults. Retinoblastoma is a cancer of the retina. This most common childhood eye cancer usually strikes children under the age of 5 years, affecting 500 to 600 children in the United States annually. In nearly a third of the cases, retinoblastoma occurs in both eyes. While symptoms are not evident early in the disease, increasing pain and vision loss eventually signal the problem. Malignant melanoma occurs most frequently in adults 60 to 65 years of age, arising from uncontrolled growth of melanocytes. There are 1500 to 2000 new cases diagnosed annually in the United States.
Structure and Physiology
The external landmarks of the eye are shown in Fig. 10.1 , and the cross-sectional anatomy of the eye is shown in Fig. 10.2 .
The eyelids and eyelashes protect the eyes. The eyelids cover the globe and lubricate its surface. The meibomian glands, which are modified sebaceous glands in the eyelids, secrete meibum , an oily lubricating substance that retards evaporation. The openings of these glands are at the eyelid margins. This is illustrated in Fig. 10.28B and seen in Fig. 10.28C .
The orbicularis oculi muscle encircles the lids and is responsible for their closure. This muscle group is the reason we have such expressive eyes. This muscle is supplied by the facial, or seventh cranial, nerve. The levator palpebrae muscle elevates the lids and is innervated by the oculomotor, or third cranial, nerve. Müller's muscle is a small part of the levator muscle that has sympathetic innervation.
The globe has six extraocular muscles that control its motion. There are four rectus and two oblique muscles: the medial rectus, the lateral rectus, the superior rectus, the inferior rectus, the superior oblique, and the inferior oblique muscles. These six extraocular muscles are shown in Fig. 10.3 .
The extraocular muscles work in a parallel, conjugate manner to maintain single, binocular vision. When the head is turned to look left, for example, the left lateral rectus and the right medial rectus contract to turn the eyes to the left. The actions and innervations of the extraocular muscles are listed in Table 10.1 , and the extraocular movements are illustrated in Fig. 10.4 .
TABLE 10.1
Actions and Innervations of the Extraocular Muscles
| Muscle | Action | Cranial Nerve Innervation |
|---|---|---|
| Medial rectus | Adduction (eye moves nasally) | Oculomotor (III) |
| Lateral rectus | Abduction (eye moves temporally [away from the nose]) | Abducens (VI) |
| Inferior rectus | Depression (eye moves down) Extorsion (the 12 o'clock position on the cornea rotates temporally) Adduction |
Oculomotor (III) |
| Superior rectus | Elevation (eye moves up) Intorsion (the 12 o'clock position on the cornea rotates nasally) Adduction |
Oculomotor (III) |
| Superior oblique | Intorsion Depression Abduction |
Trochlear (IV) |
| Inferior oblique | Extorsion Elevation Abduction |
Oculomotor (III) |
Remember “LR 6 SO 4 .” This mnemonic means that the lateral rectus (LR) muscle is innervated by the sixth cranial nerve, and the superior oblique (SO) muscle is innervated by the fourth cranial nerve. All the other muscles are innervated by the third cranial nerve.
The lateral rectus muscle, which is innervated by the abducens nerve, turns the eye laterally ( abducts the eye), as do both oblique muscles. As easy way to remember the innervations is the formula LR 6 SO 4 , meaning that the lateral rectus is innervated by cranial nerve VI (abducens) and the superior oblique is innervated by cranial nerve IV (trochlear); all the other muscles are innervated by cranial nerve III (oculomotor).
The conjunctiva is a thin, vascular, transparent mucous membrane that lines the lids of the anterior portion of the globe. The palpebral portion covers the inner surface of the lids, whereas the bulbar portion covers the sclera up to the limbus, which is the corneal-scleral junction. The conjunctiva contains many small blood vessels, which, when dilated, produce the appearance of a “red” eye. There is little nervous innervation to the conjunctiva.
The lacrimal apparatus consists of the lacrimal gland, accessory tear glands, canaliculi, tear sac, and nasolacrimal duct. These are shown in Fig. 10.5 .
The lacrimal gland produces watery tears and is located above and slightly lateral to the globe. Secretion occurs mostly as reflex tearing or crying. Tears drain through the puncta on the lids and into the superior and inferior canaliculi. These canaliculi join and enter the tear sac, located at the medial canthus of the eye. The nasolacrimal duct drains tears from the sac to the nose. Of the lacrimal apparatus, only the puncta are visible on routine examination.
The sclera is the white, fibrous, outer coat of the globe visible just beneath the conjunctiva. The extraocular muscles insert onto the sclera.
The cornea is a smooth, transparent, avascular tissue that covers the iris and joins with the sclera and conjunctival reflection at the limbus. The cornea functions as a protective window, allowing light to pass into the eye. The cornea is richly innervated by the trigeminal, or fifth cranial, nerve and is therefore exquisitely sensitive to touch and pain.
The anterior chamber, or space between the cornea anteriorly and the iris posteriorly, is filled with clear aqueous humor. Aqueous humor is produced by the ciliary body in the posterior chamber, the area behind the iris and in front of the lens. Aqueous humor circulates from the posterior chamber through the pupil into the anterior chamber and is filtered out through the canal of Schlemm, from where it eventually enters the venous system. Pressure within the eye is regulated by this filtration. The angle is formed by the juncture of the cornea and the iris at the limbus. A section through the eye at this level is shown in Fig. 10.6 .
The iris is the circular, colored portion of the eye. The small, round aperture in the middle of the iris is the pupil. Because it is optically empty in the healthy eye, it appears black. The pupil functions much like the aperture of a camera, controlling the amount of light that enters the eye.
When a light is shined on one eye, both pupils constrict consensually. This constriction is the pupillary light reflex. To understand this reflex, a brief review of the neuroanatomy is in order. Fig. 10.7 illustrates the pathways of the pupillary light reflex.
The optic, or second cranial, nerves are composed of 80% visual and 20% afferent pupillary fibers. The optic nerves leave both retinas and travel a short course to where they join each other. This joining is the optic chiasm. At the optic chiasm, the nasal fibers cross and join the uncrossed fibers of the other side, forming the optic tract. The visual fibers continue in the optic tract to the lateral geniculate body, where synapses occur, the axons of which terminate in the primary visual cortex of the occipital lobe. The afferent pupillary fibers bypass the geniculate body and end in the superior colliculus and pretectal area of the midbrain.
Light impulses to the eye cause the retina to transmit nerve impulses to the optic nerve, the optic tract, the midbrain, and the visual cortex of the occipital lobes. This is the afferent limb of the light reflex. In the midbrain, the pupillary fibers diverge and are relayed by crossed fibers to the opposite Edinger-Westphal nucleus of the oculomotor, or third cranial, nerve. Some fibers remain on the same side. The third cranial nerve is the efferent limb, which goes via the ciliary body to the sphincter muscle of the iris to cause it to contract. The direct effect is the constriction of the pupil of the eye on which the light is shined (the ipsilateral eye ). The consensual effect is the simultaneous constriction of the opposite pupil (the contralateral eye ).
The near reflex occurs when the subject looks at a nearby target. The three parts of the near reflex are accommodation, convergence, and pupillary constriction. Accommodation is defined as the near focusing of the eye, which is effected by increasing the power of the lens by contraction of the ciliary muscle, innervated by the third cranial nerve.
There is also autonomic innervation of the eyes. The iris is supplied by sympathetic and parasympathetic fibers. When the sympathetic fibers are stimulated, the pupil dilates, and the eyelid elevates. Think of the cat stalking its prey, pupils dilated, ready to pounce in the dark. The cat needs all the light it can get. The reflex is purely sympathetic. When the parasympathetic fibers in the oculomotor nerve are stimulated, pupillary constriction occurs. When we sleep, our bodies are in a parasympathetic mode and our pupils are constricted.
The lens sits directly behind the iris. It is a biconvex, avascular, colorless structure that changes its shape to focus the image on the retina. The shape is changed by the ciliary body muscles contracting. They in turn are connected to the zonules of the lens, thereby changing its shape.
The vitreous humor is the transparent, avascular gel that is located behind the lens and in front of the retina. It occupies 80% of the volume of the eye. This clear matrix is made up of collagen, hyaluronic acid, and water. It is bounded by the posterior lens capsule anteriorly and the retina posteriorly.
Eye floaters are spots in one's vision that may occur as a person ages. They may look like black or gray specks, strings, flies, or cobwebs that drift about when one moves the eyes, and they appear to dart away when one tries to look at them directly. Most eye floaters are caused by age-related changes that occur as the jelly-like vitreous becomes more liquid. Microscopic fibers within the vitreous tend to clump and can cast tiny shadows on the retina. These shadows are called floaters.
The choroid is the middle, vascular layer of the globe between the sclera and the retina. It acts as a source of nourishment, as well as a heat sink, serving to remove the extreme heat produced by the light energy entering the eye. Bruch's membrane separates the choroid from the retina. Superficial to Bruch's membrane (closer to the retina) is the retinal pigment epithelium (RPE). The RPE is a monolayer of cells between Bruch's membrane and the retina. Some of the important functions of the RPE are to absorb light passing through the retina and to regenerate the visual pigments.
The retina is the innermost layer, or “camera film,” of the eye. The retina is attached firmly to the underlying choroid at the optic nerve posteriorly and at the ora serrata anteriorly. Between these two points, the retina is in contact with the choroid, but it is not attached to it. The ora serrata is the junction of the retina and ciliary body. The retina is only 0.4 mm in thickness and is thinnest in the region of the macula. Histologically, the retina is made up of 10 distinct layers. Basically, the retina senses light through the rods and cones in its outer layer (closest to the RPE); performs initial signal processing in its middle layer; and encodes and transmits the data in its inner layer, the nerve fiber layer. The nerve fiber layer is the layer closest to the vitreous. These axons are unmyelinated until they penetrate the sclera at the optic disc to form the optic nerve.
Within the retina are several important structures: the optic disc, the retinal vessels, and the macula. Fig. 10.8 illustrates the retina of the left eye.
The optic disc is located at the nasal aspect of the posterior pole of the retina. This is the head of the optic nerve, from where the nerve fibers of the retina exit the eye. The optic disc is 1.5 mm in diameter and is ovoid. It is lighter than the surrounding retina and appears yellowish-pink due to myelination of the optic nerve. The disc margins are sharp with some normal blurring of the nasal portion. African-American patients may have pigmentation at the margins. The physiologic cup is the center of the disc, where the retinal vessels penetrate. This small depression normally occupies approximately 30% of the disc diameter.
The retinal vessels emerge from the disc and arborize on the retinal surface. The arteries are brighter red and thinner than the veins. An artery-to-vein ratio of 2 : 3 is normal.
The macula is a small, round area, approximately the size of the disc, located 3.5 mm temporal to and 0.5 mm inferior to the disc. The macula is easily seen because it is devoid of retinal vessels. In the center of the macula is the fovea, a depressed area composed only of cones. Cones provide detailed vision and color perception.
The remaining areas of the retina contain mostly rods, which compose the other neurosensory element of the retina. The rods are responsible for motion detection and night vision. It should be remembered that the image on the retina is upside down and reversed left to right: The right world is projected onto the left half of the retina, and the left world is projected onto the right half of the retina. An image in the superior world strikes the inferior part of the retina, and an inferiorly positioned image strikes the superior part. This concept is illustrated in Fig. 10.9 . The image is ultimately reversed up and down and left to right by the time the image has reached the visual cortex.
At birth, there is little pigment in the iris, which is why many infants are born with blue eyes. By 6 months of age, the pigmentation is complete. The lens is more spherical at birth than in later life. Most infants are born hyperopic (farsighted) due to the fact that the eye is small, and the image falls posterior to the retina (see Fig. 10.89 ). By 3 months after birth, the medullation process of the optic nerve is completed. As the child grows, hyperopia increases until the age of 8 years and then gradually decreases. After age 8, myopia (nearsightedness) appears to increase.
There are many changes that occur with advancing age. There is the gradual loss of elasticity of the skin around the eyes, which may lead to droopy eyelids, known as ptosis . The cornea may show an infiltration of cholesterol deposits around the limbus, which is known as an arcus senilis. The lens consistency changes from plastic to rigid, making it progressively more difficult to change its shape to focus on near objects. This condition is called presbyopia. The lens may undergo changes resulting from metabolic disorders that cause its opacification; this condition is called a cataract. The vitreous humor may develop condensations, called floaters. The retinal arteries may develop atherosclerosis, with resultant retinal ischemia or infarction.
Review of Specific Symptoms
The major symptoms of eye disease are the following:
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Loss of vision
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Eye pain
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Diplopia (double vision)
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Tearing and dryness
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Discharge
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Redness
Loss of Vision
When a patient complains of loss of vision, the following two questions must be asked:
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“Did the loss of vision occur suddenly?”
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“Is the eye painful?”
It is extremely important to ascertain the acuteness of the loss of vision and the presence or absence of pain. Sudden, painless loss of vision may result from a retinal vascular occlusion or a retinal detachment. Sudden, painful loss of vision occurs in attacks of acute narrow-angle glaucoma. Gradual, painless loss of vision commonly occurs in chronic simple glaucoma and cataracts.
Eye Pain
Eye pain may result from a variety of causes. Ask the patient the following questions:
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“Can you describe the pain?”
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“Did the pain come on suddenly?”
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“Does the light bother your eye?”
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“Do you have pain when you blink?”
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“Do you have the sensation of something in the eye?”
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“Do you have headaches?”
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“Do you have pain on movement of the eye?”
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“Do you have pain over the brow on the same side?”
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“Do you wear contact lenses?”
Pain may be experienced as “burning,” “aching,” “throbbing,” “tenderness,” or pain behind the eye. Each of these descriptions may have a range of causes. It is important to determine whether the patient has the sensation of a foreign body in the eye. Pain in the eye while blinking occurs in corneal abrasions and with foreign bodies in the eye. Photophobia is eye pain associated with light, as seen in inflammations of the uveal tract (i.e., iris, ciliary body, or choroid). Inflammations of the conjunctiva, conjunctivitis, produce a gritty sensation. Diseases of the cornea are associated with significant pain because the cornea is so richly innervated. Headaches and eye pain are common in acute narrow-angle glaucoma. Pain on motion of the eye occurs in optic neuritis. Eye pain associated with brow or temporal pain may be an indication of temporal arteritis (see Chapter 25 , The Geriatric Patient). Contact lens wearers may have corneal irritation and may complain of eye pain.
Diplopia
Diplopia, or double vision, is a common complaint. Diplopia results from a faulty alignment of the eyes. Normally, when the eyes fixate on an object, the object is seen clearly, despite the fact that the two retinal images are not exactly superimposed. These slightly different images, however, are fused by the brain; it is this fusion that produces binocular vision, or the perception of depth. When the eyes are misaligned, the two images fall on different parts of the retinas, with only one falling normally on the fovea. The field of vision of the deviated eye is different, so that its image is not projected on its fovea; therefore, this second image is different and not superimposable. The patient may close one eye to relieve this distressing situation. A compensatory head posture may be used by the patient to relieve the double vision (see Fig. 10.152 ). Elevation or depression of the patient's chin is used to overcome a vertical deviation. Tilting of the head is often used to counteract the torsional and vertical deviation. Suggested questions for the patient with diplopia are listed in Chapter 21 , The Nervous System.
Tearing and Dryness
Excessive tearing of the eyes is a common complaint. Abnormal tearing may be caused either by overproduction of tears or by an obstruction of outflow. The eye depends on the flow of tears to provide constant moisture and lubrication to maintain vision and comfort. Tears are a combination of water, for moisture; oils, for lubrication; mucus, for even spreading of the tears; and antibodies and special proteins, for resistance to infection. These components are secreted by special glands located around the eye. Thus tears provide lubrication, reduce the risk of eye infection, wash away foreign matter in the eye, and keep the surface of the eyes smooth and clear.
When there is an imbalance in this tear system, a person may experience dry eyes. Nearly 55 million Americans 50 years of age and older are estimated to have dry eye, with only 17% having been diagnosed with the condition. The prevalence of dry eyes has been estimated to be up to 30% in persons equal or older than 50 years, and it is expected to increase as the population continues to age. Based on data from the National Health and Wellness Survey, 6.8% of the United States adult population (approximately 16.4 million people) has been diagnosed with dry eye disease. The prevalence increases with age (2.7% in those 18 to 34 years old vs. 18.6% in those equal or older than 75 years) and is higher in women than men (8.8% vs. 4.5%). It is not affected by race, education, or location of residence.
The most common form of dry eyes is due to an inadequate amount of the water layer of tears. This condition, called keratoconjunctivitis sicca, is also referred to as the dry eye syndrome.
Patients suffering from the dry eye syndrome often experience:
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Dryness
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Eye pain
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Stinging or burning sensation
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Stringy discharge from the eye
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Light sensitivity
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Heavy eyelids
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Foreign body sensation
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Sand in the eye; a gritty feeling
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Itching
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Redness
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Blurring of vision
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Decreased tolerance of reading, working on the computer, or any activity that requires sustained visual attention
There are many causes of the dry eye syndrome. These include:
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Age: Dry eye is a part of the natural aging process. The majority of people older than age 50 experience some symptoms of dry eyes.
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Gender: Women are more likely to develop dry eyes because of hormonal changes and menopause.
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Medications: Certain medicines, including antihistamines, decongestants, statins, beta-blockers, diuretics, analgesics, and antidepressants can cause dry eyes.
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Medical conditions: Persons with rheumatoid arthritis, systemic lupus erythematosus, progressive systemic sclerosis, diabetes, and thyroid problems may develop dry eyes. Patients who have suffered with Stevens-Johnson syndrome (also known as erythema multiforme) may develop severe dry eyes. Also, problems with inflammation of the eyelids (blepharitis), inflammation of the surfaces of the eye, or the inward or outward turning of eyelids (entropion or ectropion, respectively) can cause dry eyes.
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Environmental conditions: Exposure to pollutants such as smoke, exhaust, and smog, and arid and windy conditions, can increase tear evaporation, resulting in dry eye symptoms. Failure to blink regularly, such as when staring at a computer screen for long periods, can also contribute to the dry eye syndrome. Excessive alcohol consumption is also associated with the dry eye syndrome.
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Other factors: Long-term use of contact lenses can be a factor in the development of dry eyes. Refractive eye surgeries, such as laser-assisted in situ keratomileusis (LASIK), 1
1 LASIK, commonly referred to as laser eye surgery, is a procedure for the correction of refractive errors such as myopia, hyperopia, and astigmatism (see Fig. 10.89 ). LASIK surgery requires the use of an excimer laser, or microkeratome, to reshape the eye's cornea to improve visual acuity. In most patients, LASIK surgery provides a permanent alternative to wearing eyeglasses or contact lenses.
can cause decreased tear production and dry eyes.
Sometimes, a person with a dry eye will have excess tears running down the cheeks, which may seem confusing. This happens when the eye isn't getting enough lubrication. The eye sends a distress signal through the nervous system for more lubrication. In response, the eye is flooded with tears to try to compensate for the underlying dryness. However, these tears are mostly watery and do not have the lubricating qualities or the rich composition of normal tears. They wash debris away, but they do not coat the eye surface properly.
Discharge
Discharge from the eye can be watery, mucoid, or purulent. A watery or mucoid discharge is often associated with allergic or viral conditions, whereas a purulent discharge occurs in association with bacterial infections. Most of the time, eye discharge is harmless. However, sometimes it can be an indication of a more serious condition. Pollen, gusty winds, dry eyes, or an eyelash can cause an irritation that will lead to the discharge as well. Other causes of eye discharge can be associated with medical conditions such as conjunctivitis, or more serious, corneal ulcers.
Redness
The symptom of the red eye is very common. The interviewer should ask the following questions:
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“Have you had any injury to the eye?”
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“Does anyone else in the family have a red eye?”
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“Have you had any recent coughing spells? Vomiting?”
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“Have you had any associated eye pain?”
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“Does light bother your eyes?”
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“Is there any associated discharge?”
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“Do you wear contact lenses?”
The eye may appear bloodshot. Redness may result from trauma, infection, allergy, or sudden increased pressure in the eye. Severe coughing spells, Valsalva maneuver for any reason, or recurrent vomiting may cause a patient to have a subconjunctival hemorrhage. A family member or friend with viral conjunctivitis may be the source of a patient's red eye. The combination of eye pain and red eye may indicate acute narrow-angle glaucoma, or an inflammatory condition known as scleritis or episcleritis. Table 10.2 summarizes the differential diagnosis for the red eye. Uveitis, inflammation of the uveal tract, which is associated with a red eye, can manifest with light sensitivity. Patients wearing contact lenses may suffer from corneal irritation and may have eye redness.
TABLE 10.2
Differential Diagnosis for Red Eye
| Manifestation | Acute Conjunctivitis a | Acute Iritis b | Narrow-Angle Glaucoma | Corneal Abrasion |
|---|---|---|---|---|
| History | Sudden onset Exposure to conjunctivitis |
Fairly sudden onset Often recurrent |
Rapid onset Sometimes history of attack Highest incidence among Jews, Swedes, and the Inuit |
Trauma Pain |
| Vision | Normal | Impaired if untreated | Rapidly lost if untreated c | Can be affected if central |
| Pain | Gritty feeling | Photophobia | Severe | Exquisite |
| Bilaterality | Frequent | Occasional | Occasional | Usually unilateral |
| Vomiting | Absent | Absent | Common | Absent |
| Cornea | Clear (epidemic keratoconjunctivitis has corneal deposits) | Variable | “Steamy” (like looking through a steamy window) | Irregular light reflex |
| Pupil | Normal, reactive | Sluggishly reactive Sometimes irregular in shape |
Partially dilated, oval, nonreactive | Normal, reactive |
| Iris | Normal | Normal d | Difficult to see, owing to corneal edema | Shadow of corneal defect may be projected on the iris with penlight |
| Ocular discharge | Mucopurulent or watery | Watery | Watery | Watery or mucopurulent |
| Systemic effect | None | Few | Many | None |
| Prognosis | Self-limited | Poor if untreated | Poor if untreated | Good if not infected |
See Fig. 10.92 .
a Can be viral, bacterial, or allergic.
b See Fig. 10.67 .
c Seeing “rainbow” can be an early symptom during an acute attack.
d Slit-lamp examination revealing cells in anterior chamber is diagnostic.
General Suggestions
It is important to determine the medications that a patient is taking because many drugs have deleterious effects on the eye. Some antimalarial, antituberculous, antiglaucoma, and anti-inflammatory drugs can cause eye disorders. A thorough family history reveals familial disease tendencies such as glaucoma, cataracts, retinal degeneration, strabismus, or corneal dystrophies.
There are many specific symptoms related to eye disease. Table 10.3 lists some common visual eye symptoms and their associated disease states. Table 10.4 lists some common nonvisual but painful conditions and their associated disease states. Table 10.5 lists some common nonvisual, painless eye symptoms and their disease states.
TABLE 10.3
Common Visual Eye Symptoms and Disease States
| Visual Symptom | Possible Causes |
|---|---|
| Loss of vision | Optic neuritis |
| Detached retina | |
| Retinal hemorrhage | |
| Central retinal vascular occlusion | |
| Central nervous system disease | |
| Spots | No pathologic significance a |
| Flashes | Migraine |
| Retinal detachment | |
| Posterior vitreous detachment | |
| Loss of visual field or presence of shadows or curtains | Retinal detachment |
| Retinal hemorrhage | |
| Glare, photophobia | Iritis (inflammation of the iris) |
| Meningitis (inflammation of the meninges) | |
| Distortion of vision | Retinal detachment |
| Macular edema | |
| Difficulty seeing in dim light | Myopia |
| Vitamin A deficiency | |
| Retinal degeneration | |
| Colored halos around lights | Acute narrow-angle glaucoma |
| Opacities in lens or cornea | |
| Colored vision changes | Cataracts |
| Drugs (digitalis increases yellow vision) | |
| Double vision | Extraocular muscle paresis or paralysis |
a May precede a retinal detachment or may be associated with ingestion of fertility drugs.
TABLE 10.4
Common Nonvisual, Painful Eye Symptoms and Disease States
| Nonvisual, Painful Symptom | Possible Causes |
|---|---|
| Foreign body sensation | Foreign body |
| Corneal abrasion | |
| Burning sensation | Uncorrected refractive error |
| Conjunctivitis | |
| Sjögren's syndrome | |
| Throbbing, aching | Acute iritis (inflammation of the iris) |
| Sinusitis (inflammation of the sinuses) | |
| Tenderness | Eyelid inflammation |
| Conjunctivitis | |
| Iritis | |
| Headache | Refractive errors |
| Migraine | |
| Sinusitis | |
| Drawing sensation | Uncorrected refractive errors |
TABLE 10.5
Common Nonvisual, Painless Eye Symptoms and Disease States
| Nonvisual, Painless Symptom | Possible Causes |
|---|---|
| Itching | Dry eyes |
| Eye fatigue | |
| Allergies | |
| Tearing | Emotional states |
| Hypersecretion of tears | |
| Blockage of drainage | |
| Dryness | Sjögren's syndrome |
| Decreased secretion as a result of aging | |
| Sandiness, grittiness | Conjunctivitis |
| Fullness of eyes | Proptosis (bulging of the eyeball) |
| Aging-related changes in the lids | |
| Twitching | Fibrillation of orbicularis oculi |
| Eyelid heaviness | Fatigue |
| Eyelid edema | |
| Dizziness | Refractive error |
| Cerebellar disease | |
| Vestibular disease | |
| Excessive blinking | Local irritation |
| Facial tic | |
| Eyelids sticking together | Inflammatory disease of eyelids or conjunctivae |
Effect of Blindness on the Patient
The loss of sight is a terrifying experience. The sighted person lives mostly in a visual and auditory world illuminated by lights and colors. When blindness occurs, the person loses not only the ability to see but also the perceptual center of their world. This center must now be replaced by hearing and touch. Because light is often equated with life, the inability to see light is associated with death. The newly blinded patient must take a new place in society. He or she can no longer read ordinary books, can no longer receive visual stimuli, and is unable to appreciate the world of visual communication. This can result in a reactive depression. The healthcare provider must show genuine concern for blind patients and try to understand their feelings of discouragement and despair.
The person who is blind from birth or early childhood has little or no conception of the visual world. Having never been able to see, this patient has no visual frame of reference.
On occasion, a blind individual recovers sight as a result of a surgical procedure later in life. Many difficulties may arise owing to the reorganization of the patient's perception. His or her frame of reference has been shifted from touch to sight. Surprisingly, many of these patients become depressed after attaining vision. Facial expressions mean nothing because only with experience can people understand them. The following quote from a case history by Gregory and Wallace illustrates the response of such an individual: “He suffered one of the greatest hardships (blindness) and yet he lived with energy and enthusiasm. When his handicap was apparently swept away, as by a miracle, he lost his peace and self-respect.”
Similarly, the patient with normal vision may develop psychosomatic eye problems as a result of anxiety. Loss of vision also can accompany panic disorders. Such individuals can have either partial or complete vision loss in one or both eyes. Supportive care of the primary problem usually results in the return of vision.
In multiple sclerosis, one of the presenting symptoms may be the sudden onset of blindness caused by optic neuritis. This blindness in most cases reverses completely, in approximately 6 weeks. This is a very frightening experience for a typically young patient.
Physical Examination
The equipment necessary for the examination of the eye is as follows: an ophthalmoscope, a penlight, a pocket visual acuity card, and a 3 × 5 inches (7.6 × 12.7 cm) card.
The physical examination of the eye includes the following:
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Visual acuity
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Visual fields
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Ocular movements
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External and internal eye structures
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Ophthalmoscopic examination
Visual Acuity
See .
Visual acuity is expressed as a ratio, such as 20/20. The first number is the distance in feet from which the patient reads the chart. The second number is the distance in feet at which a person with normal vision can read the same line of the chart. Another way of describing visual acuity is as follows: if a person has 20/20 vision, that person has 20/20 or 100% vision because 20 divided by 20 equals 1, or 100% of normal vision. The abbreviation OD refers to the right eye (oculus dexter); OS refers to the left eye (oculus sinister); OU refers to both eyes (oculus uterque). 2
2 Abbreviations are Latin: OD, oculus dexter; OS, oculus sinister; OU, oculus uterque.
Using the Standard Snellen Eye Chart
The most commonly used eye chart is known as the Snellen eye chart. It usually shows 11 rows of capital letters. The first line has one very large letter. Each row after that has increasing numbers of letters that are smaller in size.
The patient is positioned 20 feet away from the chart. If the patient wears glasses for distance, he or she should wear them for the examination. The patient is asked to cover one eye with the palm 3
3 Always ask a patient to cover the eye with the palm. When fingers are used to cover the eye, a patient may peek between the fingers to see the chart.
or an index card and read the smallest line possible. If the best he or she can see is the 20/200 line, the patient's vision in that eye is 20/200; this means that at 20 feet, the patient can see what a person with normal vision can see at 200 feet. This can also be explained as 10% of normal vision in that eye. If a patient at 20 feet cannot see the 20/200 line, he or she is moved closer until the letters are recognizable. If the patient can read these letters at 5 feet, the patient's visual acuity in that eye is 5/200.
Using a Pocket Visual Acuity Card
If the standard Snellen eye chart is not available, a pocket visual acuity card is helpful. This is viewed at 14 inches (35.6 cm). The patient is again asked to read the smallest line possible. If neither eye chart is available, any printed material may be used. The examiner should remember that most patients older than 40 years require reading glasses. Although visual acuity cannot be quantified, the examiner can certainly determine whether the patient has any vision. In such a case, the patient is asked to cover an eye and read the smallest line possible on a given printed page.
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