- Eye disorders: A look at eye disorders
- Eye disorders: Anatomy and physiology
- Eye disorders: Assessment
- Eye disorders: Diagnostic tests
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Eye disorders: A look at eye disorders
Focus topic: Eye disorders
About 70% of all sensory information reaches the brain through the eyes. Disorders in vision can interfere with a patient’s ability to function independently, perceive the world, and enjoy beauty.
No matter where you practice nursing, you’re likely to encounter patients with eye problems. Some patients may report an eye problem as their chief complaint; others may tell you of a problem while you’re evaluating another complaint or performing routine care.
Eye disorders: Anatomy and physiology
Focus topic: Eye disorders
The eye is the sensory organ of sight. It’s a hollow ball filled with fluid (vitreous humor) and consists of three layers:
- fibrous outer layer — sclera, bulbar conjunctiva, and cornea
- vascular middle layer — iris, ciliary body, and choroid
- inner layer — retina.
Lens and liquids
Between the iris and retina lies the lens, suspended by ligaments from the ciliary body. The vitreous and aqueous humors are separated by the lens. The vitreous humor lies behind the lens, and the aqueous humor, in front of the lens.
Muscles for movement
Six extraocular muscles, innervated by the cranial nerves, control the movement of the eyes. The coordinated actions of those muscles allow the eyes to move in tandem, ensuring clear vision.
Lashes and lacrimals
Outside the eye, the bony orbits protect the eye from trauma. Eyelids (palpebrae), lashes, and the lacrimal apparatus protect it from injury, dust, and foreign bodies.
Sclera, bulbar conjunctiva, and cornea
The sclera is the white coating on the outside of the eyeball. Together with the vitreous humor on the inside, the sclera helps maintain the retina’s placement and the eyeball’s nearly spherical shape. The bulbar conjunctiva, a thin, transparent membrane that lines the eyelid, covers and protects the anterior portion of the white sclera. The cornea is a smooth, avascular, transparent tissue located in front of the iris that refracts (bends) light rays entering the eye. A film of tears coats the cornea, keeping it moist. The cornea merges with the sclera at the corneal limbus.
Here’s mud in your eye
The ophthal mic branch of cranial nerve V (trigeminal nerve) innervates the cornea. Stimulation of this nerve initiates a protective blink called the corneal reflex.
Iris and pupil
The iris is a circular, contractile diaphragm that contains smooth and radial muscles and is perforated in the center by the pupil. Varying amounts of pigment granules within the iris’s smooth muscle fibers give it color. Its posterior portion contains involuntary muscles that control pupil size to regulate the amount of light entering the eye.
The pupil, the iris’s central opening, is normally round and equal in size to the opposite pupil. The pupil permits light to enter the eyes. Depending on the patient’s age, pupil diameter can range from 3 to 5 mm.
Ciliary body and choroid
Suspensory ligaments attached to the ciliary body control the lens’s shape for close and distant vision. The pigmented, vascular choroid supplies the outer retina’s blood supply, then drains blood through its remaining vasculature.
Lens and vitreous chamber
Located behind the iris at the pupillary opening, the lens consists of avascular, transparent fibrils in an elastic membrane called the lens capsule. The lens refracts and focuses light onto the retina. The vitreous chamber, located behind the lens, makes up four fifths of the eyeball. This chamber is filled with vitreous humor, the gelatinous substance that, along with the sclera, maintains the shape of the eyeball.
Posterior and anterior chambers
The posterior chamber, which lies right in front of the lens, is filled with a watery fluid called aqueous humor. As it flows through the pupil into the anterior chamber, this fluid bathes the lens capsule. The amount of aqueous humor in the anterior chamber varies to maintain pressure in the eye. Fluid drains from the anterior chamber through collecting channels (trabecular meshwork) into Schlemm’s canal.
The retina is the innermost layer of the eyeball. It receives visual stimuli and transmits images to the brain for processing. Vision of any kind depends on the retina and its structures. The retina contains the retinal vessels, the optic disk, the physiologic cup, rods and cones, the macula, and the fovea centralis.
The retina has four sets of retinal vessels. Each of the four sets contains a transparent arteriole and vein that nourish the inner areas of the retina. As these vessels leave the optic disk, they become progressively thinner, intertwining as they extend to the periphery of the retina.
No light here
The optic disk is a well-defined, round or oval area measuring less than 1/8 (0.3 cm) within the retina’s nasal portion. The ganglion nerve fibers (axons) exit the retina through this area to form the optic nerve. This area is called the blind spot because it contains no light-sensitive cells (photoreceptors). The physiologic cup is a light- colored depression within the temporal side of the optic disk where blood vessels enter the retina. It covers a quarter to a third of the disk.
Now I see the light!
Photoreceptor neurons called rods and cones make vision possible. Rods respond to low-intensity light and shades of gray. Cones respond to bright light and are responsible for sharp, color vision.
Located near the center of the retina lateral to the optic disk, the macula is slightly darker than the rest of the retina. The macula provides the sharpest vision, allowing us to read and recognize faces, for example. The fovea centralis, a slight depression within the macula, contains the heaviest concentration of cones and provides the clearest vision and color perception.
Eye disorders: Assessment
Focus topic: Eye disorders
Now that you’re familiar with the anatomy and physiology of the eyes, you’re ready to assess them.
Focus topic: Eye disorders
To obtain an accurate and complete patient history, adjust your questions to the patient’s specific complaint and compare the answers with the results of the physical assessment.
Current health status
Begin by asking the patient some basic questions about his vision:
- Do you have any problems with your eyes?
- Do you wear or have you ever worn corrective lenses? If so, for how long? Are they glasses or hard or soft contact lenses?
- For what eye condition do you wear corrective lenses? Do you wear them all the time or just for certain activities, such as reading or driving?
Previous health status
To gather information about the patient’s past eye health, ask these questions:
- Have you ever had blurred vision or lost your vision in one eye temporarily? Have you ever seen spots, floaters, or halos around lights?
- Have you ever had eye surgery or an eye injury?
- Do you have a history of high blood pressure or diabetes?
- Are you taking prescription medications for your eyes or other conditions? If so, which medications and how much and how often do you take them?
Family health status
Next, ask the patient if anyone in his family has an eye disorder. Also ask if anyone in the patient’s family has ever been treated for myopia, cataracts, glaucoma, retinal detachment, or loss of vision.
To explore daily habits that might affect the patient’s eyes, ask these questions:
- Does your occupation require intensive use of your eyes, such as long-term reading or prolonged use of a video display terminal?
- Does the air where you work or live contain anything that causes you to have eye problems?
- Do you wear goggles when working with power tools, or when engaging in sports that might irritate or endanger the eye, such as swimming, fencing, or playing racquetball?
Focus topic: Eye disorders
An eye assessment involves inspecting the conjunctivae, assessing the pupils, assessing eye muscle function, and examining intraocular structures with an ophthalmoscope.
Inspecting the conjunctivae
To inspect the conjunctivae, ask the patient to look up. Gently pull the lower eyelid down to inspect the bulbar conjunctiva. It should be clear and shiny. Note excessive redness or exudate. Also observe the sclera’s color, which should be white to buff. In black patients, you may see flecks of tan.
In the pink
To examine the palpebral conjunctiva (the membrane that lines the eyelids), have the patient look down. Then lift the upper lid, holding the upper lashes against the eyebrow with your finger. The palpebral conjunctiva should be uniformly pink.
Assessing the pupils
The pupils should be equal in size, round, and reactive to light. In normal room light, the pupil will be about one-fourth the size of the iris. Unequal pupils generally indicate neurologic damage, iritis, glaucoma, or therapy with certain drugs.
The direct approach
Test the pupils for direct and consensual response. In a slightly darkened room, hold a penlight about 20 (51 cm) from the patient’s eyes, and direct the light at one eye from the side. Note the reaction of the pupil you’re testing (direct response) and the opposite pupil (consensual response). They should both react the same way. Also note sluggishness or inequality in the response. A pupil that doesn’t react to light (a “fixed” pupil) can be an ominous neurologic sign. Repeat the test with the other pupil.
To test the pupils for accommodation, place your finger approximately 4 (10 cm) from the bridge of the patient’s nose. Ask the patient to look at a fixed object in the distance and then to look at your finger. His pupils should constrict and his eyes converge as he focuses on your finger.
Assessing eye muscle function
Testing the six cardinal positions of gaze evaluates the function of each of the six extraocular muscles and the cranial nerves responsible for their movement.
To perform the test, ask the patient to remain still while you hold a pencil or other small object directly in front of his nose at a distance of about 18 (46 cm). Ask him to follow the object with his eyes without moving his head. Then move the object to each of the six cardinal positions, returning to the midpoint after each movement. The patient’s eyes should remain parallel as they move.
Examining intraocular structures
The ophthalmoscope allows you to directly observe internal structures of the eye. To see those structures properly, you should adjust the lens disc several times during your examination. Use the black, positive numbers on the disc to focus on near objects, such as the patient’s cornea and lens. Use the red, negative numbers to focus on distant objects such as the retina.
Looking at the lens
First, set the ophthalmoscope’s lens disc to zero and hold the ophthalmoscope about 4 (10 cm) from the patient’s eye. Direct the light through the pupil to elicit the red reflex, a reflection of light off the choroid.
Now, move the ophthalmoscope closer to the eye. Adjust the lens disc so you can focus on the eye’s anterior chamber and lens. If the lens is opaque, indicating cataracts, you may not be able to complete the examination.
Rotating to the retinal structures
To examine the retinal structures, start with the dial turned to zero. Rotate the lens-power disc to keep the retinal structures in focus. The first retinal structures you’ll see are the blood vessels. Rotating the dial into the negative numbers will bring the blood vessels into focus. The arteries will look thinner and brighter than the veins.
Follow one of the vessels along its path toward the nose until you reach the optic disk, where all vessels in the eye originate. Examine arteriovenous crossings for arteriovenous nicking (localized constrictions in the retinal vessels), which might be a sign of hypertension.
Diggin’ the disk
The optic disk is a creamy pink to yellow-orange structure with clear borders and a round-to-oval shape. The disk may fill or exceed your field of vision. If you don’t see it, follow a blood vessel toward the center until you do. The nasal border of the disk may look somewhat blurred.[sociallocker]
Riveted on the retina
Completely scan the retina by following four blood vessels from the optic disk to different peripheral areas. As you scan, note lesions or hemorrhages.
Movin’ in on the macula
Finally, move the light laterally from the optic disk to locate the macula, the part of the eye most sensitive to light. It appears as a darker structure, free from blood vessels. If you locate it, ask the patient to shift his gaze into the light.
Eye disorders: Diagnostic tests
Focus topic: Eye disorders
Tests to determine the presence of eye disorders include direct evaluation techniques as well as radiologic and imaging studies.
Focus topic: Eye disorders
Refraction, slit-lamp examination, and tonometry allow direct evaluation of various eye structures and functions.
Defined as the bending of light rays by the cornea, aqueous humor, lens, and vitreous humor in the eye, refraction enables images to focus on the retina and directly affects visual acuity. This test is done routinely during a complete eye examination or whenever a patient complains of a change in vision. It defines the degree of impairment (refractive error) and determines the degree of correction required to improve visual acuity with glasses or contact lenses.
- Explain to the patient the test is painless and safe and that it takes about 30 minutes.
- Tell the patient he shouldn’t use any eye drops, including prescription eye drops, for at least 24 hours before the test.
- Explain that eye drops may be instilled to dilate the pupils and inhibit accommodation by the lens. Ask the patient whether he has had a hypersensitivity reaction to eye drops, has angle-closure glaucoma, or has an intra ocular lens implant. Dilating eye drops shouldn’t be administered to anyone with those conditions.
The slit lamp is an instrument equipped with a special lighting system and a binocular microscope. This tool allows the practitioner to visualize in detail the anterior segment of the eye, which includes the eyelids, eyelashes, conjunctiva, sclera, cornea, tear film, anterior chamber, iris, lens, and anterior portion of the vitreous humor (vitreous face). If abnormalities are noted, special devices may be attached to the slit lamp to allow more detailed investigation.
- If the patient is wearing contact lenses, have him remove them before the test, unless the test is being performed to evaluate the fit of the contact lenses.
- When instilling dilating drops, tell the patient that his near vision will be blurred for 40 minutes to 2 hours. Advise him to wear dark glasses in bright sunlight until his pupils return to normal diameter.
- Don’t administer dilating eyedrops to the patient who has angleclosure
glaucoma, is hypersensitive to mydriatics, or has an intraocular
Tonometry allows noninvasive measurement of intraocular pressure (IOP) to detect glaucoma, a common cause of blindness, at an early stage in the disease. In the early stages of glaucoma, increased IOP causes the eyeball to harden and become more resistant to extraocular pressure. Pneumotonometry uses a puff of air to the eye to measure pressure; applanation tonometry provides the same information by measuring the amount of force required to flatten a known corneal area.
- Because an anesthetic is instilled before the test, tell the patient not to rub his eyes for at least 20 minutes after the test, to prevent corneal abrasion.
- If the patient wears contact lenses, tell him not to reinsert them for at least 30 minutes after the test.
- If the tonometer moved across the cornea during the test, tell the patient that he may feel a slight scratching sensation in the eye when the anesthetic wears off. Explain that this sensation could be the result of a corneal abrasion and should disappear within 24 hours; however, the practitioner may prescribe prophylactic antibiotic drops.
Radiologic and imaging studies
Radiologic and imaging studies include fluorescein angiography, ocular ultrasonography, and orbital computed tomography (CT).
Fluorescein angiography records the appearance of blood vessels inside the eye through rapid-sequence photographs of the fund us (posterior inner part of the eye).
The photographs, which are taken with a special camera, follow the I.V. injection of sodium fluorescein. This contrast medium enhances the visibility of micro vascular structures of the retina and choroid, allowing evaluation of the entire retinal vascular bed, including retinal circulation.
- Check the patient’s history for an intraocular lens implant, glaucoma, and hypersensitivity reactions, especially reactions to contrast media and dilating eye drops.
- If miotic eye drops are ordered, tell the patient with glaucoma not to use them on the day of the test.
- Explain to the patient that eye drops will be instilled to dilate his pupils and that a dye will be injected into his arm. Remind him to maintain his gaze position and fixation as the dye is injected. Tell him that he may briefly experience nausea and a feeling of warmth. Reassure him as necessary.
- Observe the patient for hypersensitivity reactions to the dye, such as vomiting, dry mouth, metallic taste, sudden increased salivation, sneezing, light-headedness, fainting, and hives. Rarely, anaphylactic shock may result.
- Remind the patient that his skin and urine will be a yellow color for 24 to 48 hours after the test and that his near vision will be blurred for up to 12 hours.
Ocular ultrasonography measures high-frequency sound waves that pass through the eye and reflect off ocular structures, providing an illustration of the eye’s structures. This method especially helps to evaluate a fundus clouded by an opaque medium such as a cataract. In such a patient, this test can identify pathologies that ophthalmoscopy can’t normally detect. The practitioner may also order this test before such surgery as cataract removal or intraocular lens implantation. Ocular ultrasonography may also be performed before such surgery as cataract removal or implantation of an intraocular lens.
- Tell the patient that a small transducer will be placed on his closed eyelid and that the transducer will transmit high-frequency sound waves that will reflect off the structures in the eye.
- Inform him that he may be asked to move his eyes or change his gaze during the procedure; explain that his cooperation will help to ensure accurate results.
- After the test, remove the water-soluble jelly that was placed on the patient’s eyelids.
Orbital computed tomography
Orbital CT allows visualization of abnormalities that standard X-rays don’t readily show. For instance, orbital CT can delineate the size, position, and relationship of an abnormality to adjoining structures. Contrast media may be used to define ocular tissues and help confirm a suspected circulatory disorder, hemangioma, or subdural hematoma. Orbital CT does more than just evaluate orbital and adjoining structures; it also permits precise diagnosis of many intracranial lesions that affect vision.
- If a contrast medium will be administered, withhold food and fluids from the patient for 4 hours before the test. Check his history for hypersensitivity reactions to iodine, shellfish, or radiographic dyes.
- Tell the patient that he’ll be positioned on an X-ray table and that the head of the table will move into the scanner, which will rotate around his head and make a whirring noise.
- If a contrast medium will be used for the procedure, tell the patient that he may feel flushed and warm and may experience a transient headache, a salty taste, and nausea or vomiting after injection of the medium. Reassure him that these reactions to the contrast medium are typical.