22.2: Eyes
By the end of this section, you will be able to:
- Analyze the structure and function of the eyes
- Understand how to perform a nursing assessment of the eyes
- Recall common abnormalities of the eye
The nursing assessment of the eye plays a pivotal role in ensuring the overall health and well-being of individuals. The eyes are not only vital for vision but also serve as windows to the body’s general health. Through careful observation, evaluation, and documentation, nurses can uncover potential issues, monitor the progression of existing conditions, and contribute to timely interventions. Whether assessing visual acuity, examining the external and internal structures of the eye, or addressing specific concerns, the nursing assessment of the eye is a fundamental component of comprehensive patient care.
Structure and Function of the Eyes
Located within the orbit of the skill, the eye is a complex and intricate organ responsible for receiving visual information from the surrounding environment and transmitting it to the brain for interpretation. Its various structures work together to allow us to see and perceive the world around us (Figure 22.17).
External Structures
External structures of the eye consist of the following:
- Eyebrow: The eyebrow is the hair-covered ridge above the eye that helps protect the eye from sweat and direct sunlight.
- Eyelid: The eyelid is the movable fold of skin and muscle that covers and protects the front of the eye.
- Eyelashes: The eyelashes are short hairs along the eyelid edges that help prevent debris from entering the eye.
- Conjunctiva: The conjunctiva is a thin, transparent membrane covering the front surface of the eye (except the cornea) and the inner surface of the eyelids.
- Cornea: The cornea is the clear, dome-shaped front surface of the eye that focuses light onto the lens and retina.
- Sclera: The sclera is the white, tough outer covering of the eye that helps maintain its shape and protect its inner structures.
- Iris: The iris is the colored part of the eye that controls the size of the pupil and regulates the amount of light entering the eye.
- Pupil: The pupil is the black circular opening in the center of the iris that allows light to enter the eye.
- Lacrimal gland: The lacrimal gland produces tears that keep the eye moist and help with lubrication, nourishment, and protection against infections.
- Lacrimal ducts: The lacrimal duct drains tears from the eye’s surface to the nasal cavity.
Internal Structures
Internal structures of the eye consist of the following:
- Lens: The lens is a transparent, flexible structure located behind the iris. It changes shape to focus light onto the retina.
- Ciliary muscle: The ciliary muscle controls the shape of the lens to help with focusing on near and distant objects (accommodation).
- Vitreous humor: The vitreous humor is a gel-like substance that fills the larger space within the eye, helping maintain its shape and providing support to the retina.
- Retina: The retina is the innermost layer of the eye that contains specialized cells called photoreceptors (rods and cones) that detect light and transmit visual signals to the brain.
- Cones: A cone is a photoreceptor that is primarily responsible for color vision and visual acuity (sharpness).
- Rods: A rod is a photoreceptor that is responsible for vision in low-light conditions and for detecting movement.
- Macula: The macula is the small, central area of the retina responsible for central vision and color perception.
- Optic nerve: The optic nerve is a bundle of nerve fibers that carries visual information from the retina to the brain for processing.
- Optic disc: The optic disc is the area where the optic nerve exits the retina; it lacks photoreceptors, creating the “blind spot.”
Movement of the eye within the orbit occurs by the contraction of six extraocular muscles that originate from the bones of the orbit and insert into the surface of the eyeball. The extraocular muscles are innervated by the abducens nerve, trochlear nerve, and oculomotor nerve (cranial nerves III, IV, and V).
Vision
The process of vision is a complex and intricate interaction involving various structures within the eyes, brain, and neural pathways. From the visual fields that encompass our surroundings to the intricate neural pathways that relay information to the brain, and to the reflexes that adapt our visual experience to changing conditions, each facet of this process contributes to our profound sense of sight. Key elements of vision include visual fields, visual pathways , and visual reflexes.
Visual Fields and Visual Pathways
A visual field refers to the entire area that an individual can see when their gaze is fixed straight ahead. It includes all the objects and surroundings that can be perceived without moving the eyes. The visual field can be divided into two main parts for each eye: the central visual field and the peripheral visual field. The central visual field is the portion of the visual field that corresponds to the area around the point where you are directly looking. It provides the sharpest and most detailed vision and is critical for activities like reading, recognizing faces, and focusing on specific objects. The peripheral visual field encompasses the outer edges of the visual field. While it does not provide the same level of detail as the central visual field, it plays a crucial role in detecting motion, objects, and changes in the environment. It is especially important for spatial awareness and detecting potential threats from the sides.
A visual pathway is a complex network of neural connections that carries visual information from the eyes to the brain, where it is processed and interpreted to create visual perceptions. The visual pathway involves a series of structures and connections that work together to transmit visual signals and transform them into meaningful visual experiences. The process begins in the retina, where specialized cells called photoreceptors (rods and cones) detect light and convert it into electrical signals. The electrical signals generated by the photoreceptors travel along the optic nerves. These nerves carry the visual information toward the brain. Upon reaching the optic chiasm, which is located at the base of the brain, some of the nerve fibers from each optic nerve cross over to the opposite side, which allows information from both eyes to be combined and integrated. The nerve fibers that have crossed over at the optic chiasm continue as optic tracts, which carry the visual information further into the brain. The optic tracts connect to the lateral geniculate nucleus (LGN), a structure in the thalamus (a part of the brain) that processes and relays the visual signals to the visual cortex. The visual cortex, located in the occipital lobe at the back of the brain, receives and processes the visual information sent by the LGN. Different areas of the visual cortex specialize in analyzing different aspects of visual perception, such as color, shape, and motion. The visual cortex integrates and interprets the incoming visual signals to create the visual perceptions that are experienced.
Visual Reflexes
A visual reflex is an automatic and involuntary response of the eyes and the body to visual stimuli. These reflexes play a crucial role in maintaining visual stability, protecting the eyes, and optimizing visual perception. Important visual reflexes include the following:
- Pupillary reflex: Pupils constrict in bright light or dilate in dark spaces to regulate the amount of light entering the eye. This reflex is controlled by the interaction between the iris and the brain’s visual centers.
- Accommodation reflex: When looking at objects at varying distances, the eyes automatically adjust the shape of the lens to focus the image clearly on the retina to ensure objects at different distances remain in focus.
- Convergence reflex: When an object moves closer to the eyes, the eyes turn inward (converge) to keep the object in focus.
- Optokinetic reflex: When presented with a moving visual stimulus, such as a rotating drum with stripes, the eyes move in the direction of the stimulus and then reset to the initial position. This reflex helps stabilize vision during continuous movement.
- Vestibulo-ocular reflex: This reflex coordinates eye movements with head movements to maintain stable vision while the head is in motion. When the head moves, the eyes move in the opposite direction to counteract the movement and keep the visual scene steady.
- Blink reflex: When an object approaches the eyes suddenly, such as a foreign object or an unexpected movement, the eyelids automatically close (blink) to protect the eyes from potential harm.
- Gaze fixation reflex: When focusing on a stationary object, the eyes make small involuntary movements that prevent visual adaptation and help maintain a clear image on the retina.
- Optical righting reflex: When the body’s orientation changes, such as when tilting the head, the eyes automatically adjust their position to align with the new gravitational reference.
- Near response reflex: When looking at a nearby object, the eyes converge to bring the object into focus and the pupils constrict. This reflex is part of the accommodation-convergence reflex loop.
Visual reflexes ensure that the eyes continuously adapt to changes in the visual environment and maintain optimal visual function. These reflexes are mediated by complex neural pathways and involve interactions between the eyes, the brain’s visual centers, and other sensory systems like the vestibular system (which controls balance and spatial orientation).
Nursing Assessment: Inspecting the Eyes
Inspecting the eyes is a fundamental component of the nursing assessment, allowing healthcare providers to gather valuable information about a person’s ocular health and overall well-being. This assessment involves careful observation and examination of the eyes and their surrounding structures. Through this process, nurses can identify potential abnormalities, monitor changes in visual health, and contribute to timely interventions. Whether assessing the external appearance of the eyes, eyelids, or conjunctiva, or observing pupil reactions and eye movements, this comprehensive examination offers crucial insights into a patient’s visual status.
Assessing the Pupils
Inspecting the pupils is an important part of a nursing assessment, as it can provide valuable information about a person’s neurological and ophthalmic health. To assess the pupils, ensure proper lighting in the room (dim lighting can help with assessing pupil size). Wash your hands and don gloves. Explain the procedure to the patient to ensure their cooperation and comfort. Position the patient comfortably sitting or lying down, facing you.
Begin by assessing the patient’s overall level of alertness and consciousness. A patient who is not fully alert may have different pupil responses. Ask the patient to look straight ahead, keeping their gaze focused on a distant object. Hold the penlight or flashlight about 12 to 15 inches away from the patient’s face and shine the light directly into one eye. Observe both pupils for their initial size and equality. They should be of equal size and react similarly to light. On average, a normal adult pupil is approximately 2 to 4 millimeters in bright lights and 4 to 8 millimeters in dark spaces. Note any differences in size between the two pupils. Test the pupil’s reaction to light by shining the light directly into one pupil and observing the response. The illuminated pupil should constrict briskly, and the opposite pupil should also constrict when light is shone into the other eye. If one or both pupils do not constrict or if the response is sluggish, it may indicate an abnormality in the neurological or ophthalmic system.
To test pupil accommodation, ask the patient to focus on a near object (e.g., your finger) and then switch their focus to a distant object. Observe the pupils for changes in size. The pupils should constrict when focusing on a near object and dilate when focusing on a distant object. If the pupils do not react as expected during accommodation, it may indicate a dysfunction in the pupil’s response to changes in focus.
Visual Acuity
Assessing visual acuity is a crucial aspect of a comprehensive eye examination. The visual acuity measures a person’s ability to see details at a specific distance. Visual acuity includes both far and near vision assessments.
To assess far-distance vision, ensure the room is well lit and the patient is wearing any corrective lenses they normally use (glasses or contact lenses). Explain to the patient they will be asked to read letters or symbols on a chart to assess their ability to see details. Far-distance acuity is measured using the Snellen chart (Figure 22.18) at a distance of 20 feet (6 meters) in the United States. The Snellen chart consists of rows of letters or symbols, with the largest and most visible letters at the top and progressively smaller ones below. Instruct the patient to cover one eye and read the letters from the top row to the bottom until they can no longer correctly identify the letters or symbols. Visual acuity is recorded as a fraction. The top number represents the distance at which the chart is viewed (20 feet), and the bottom number indicates the distance at which a person with normal vision can read the line. For example, if the patient can read the line labeled “20/40,” it means they can see at 20 feet what a person with normal vision can see at 40 feet.
A technique for how to perform a visual acuity test with a Snellen eye chart is presented in this video.
See the competency checklist for Measuring Distance Visual Acuity. You can find the checklists on the Student resources tab of your book page on openstax.org.
To assess near vision, explain to the patient that you will be assessing their ability to read small print at a close distance. A near vision chart, such as a Jaeger card (Figure 22.19), consists of paragraphs of text with varying font sizes. Ask the patient to hold the Jaeger card 14 to 16 inches from their eyes and read aloud the text on the chart starting from the largest font size. Proceed to smaller font sizes until the patient can no longer comfortably read the text. Note the font size at which the patient is able to read comfortably. For example, if they can read text labeled “J5,” it means they can read text that is typically readable by a person with normal vision at a distance of 5 inches.
Extraocular Movements
Assessing extraocular movement is an essential part of a neurological and ophthalmic examination. These movements involve the coordinated actions of the six muscles that control each eye’s movement and alignment. Ensure proper lighting in the room and position the patient comfortably sitting or lying down, facing you. Explain to the patient that you will be assessing their eye movements to ensure their eyes can move smoothly in different directions. Test the six cardinal directions of gaze by asking the patient to keep their head still and follow a target (your fingertip or a pen) with their eyes only, without moving their head. Instruct the patient to focus on the target as you move it through the six cardinal directions of gaze: right (lateral), left (lateral), up (superior), down (inferior), upper-right diagonal, and upper-left diagonal. While the patient is tracking the target with their eyes, observe their eye movements for smooth and coordinated motions in each direction. An involuntary, rhythmic, back-and-forth movement of the eyes is termed nystagmus and is considered abnormal.
To test convergence, ask the patient to focus on an object (e.g., your fingertip) held about 2 inches in front of their nose. Slowly move the object toward the patient’s nose while instructing them to keep looking at the object. Observe their eyes for convergence, where both eyes move inward. Abnormal findings, such as limited eye movements, jerky motions, or nystagmus, may indicate issues with the extraocular muscles, issues with the cranial nerves (particularly cranial nerves III, IV, and VI), or neurological problems.
Peripheral Vision
Assessing peripheral vision , also known as visual field, is important for detecting any abnormalities or defects in a person’s ability to see objects in their side or peripheral vision. Ensure adequate lighting and seat the patient comfortably facing you, at eye level. Explain to the patient that you will be testing their ability to see objects in their side vision. To conduct the confrontation test , instruct the patient to cover one eye. Instruct the patient to keep their gaze fixed on your nose or another reference point in the center. Hold your hands or an object in each of the four quadrants of the patient’s visual field: superior, inferior, temporal (side), and nasal (side). Ask the patient to tell you as soon as they see your fingers or the object you are holding in their peripheral vision. They should not look directly at the objects but should maintain their gaze on the center. Compare the patient’s responses to the objects in each quadrant of the visual field to assess whether their peripheral vision is intact. If the patient consistently misses objects in certain quadrants, it could indicate peripheral vision deficits or defects, which may warrant further evaluation by an eye care professional or a more detailed visual field test. Assessing peripheral vision is crucial for detecting conditions like glaucoma, retinal disorders, and neurological issues that can affect peripheral vision.
Validating and Documenting Data
Data should be validated if discrepancies exist between subjective and objective data , significant changes occur between visits, or highly abnormal findings are noted. To validate the data, the nurse may need to repeat the physical assessment and clarify the subjective findings with the patient. Other times, the nurse may need another nurse or healthcare professional to verify the findings.
Accurate documentation is needed to promote effective communication among the interdisciplinary team. Documenting the results of an eye assessment begins with the chief complaint or reason for the assessment, whether it is routine, due to specific symptoms, or as part of a larger medical evaluation. Document the appearance of the eyes, eyelids, eyebrows, and surrounding skin. Note any swelling, redness, lesions, or abnormalities. Describe the color, texture, and any signs of inflammation, infection, or discoloration. Note the clarity of the cornea and any irregularities. Observe the color and shape of the iris. Measure and record the size of the pupils, documenting any irregularities, such as unequal sizes. Record observations of eye movements, smoothness, coordination, and the presence of nystagmus. Record the results of visual acuity tests (Snellen chart or other methods) for both near and far vision. Document the response of the pupils to light stimuli. Note if they constrict (miosis) in bright light and dilate (mydriasis) in dim light. Describe the patient’s ability to focus on a near object and how the pupils constrict during this process. Document any additional tests that were performed, such as color vision, depth perception, or visual field tests, and also document the results.
Abnormalities of the Eye
When conducting a health assessment, it is important to be able to recognize abnormalities of the eye that impact the eyes’ structures, functions, and visual perception. From common refractive errors that blur the clarity of vision, to more complex conditions affecting the external and internal structures of the eyes, these abnormalities demand attention and timely intervention. While there are many abnormalities that may be seen during the eye assessment, this section reviews the most common abnormalities.
Abnormalities of the External Eye
Abnormalities of the external eye refer to various visual, structural, or functional deviations from the normal appearance and function of the eye’s outer structures. These abnormalities can result from various eye conditions, injuries, infections, or systemic disorders. Common abnormalities of the external eye, including conjunctivitis (pink eye), hordeolum (stye), chalazion, ptosis, ectropion, and exophthalmos can be found in Table 22.3.
| Condition | Description | Visual Example |
|---|---|---|
| Conjunctivitis (also, pink eye) | Inflammation of the conjunctiva (thin membrane covering the sclera and inner eyelids) due to infections (bacterial, viral, or allergic), causing redness, itching, discharge, and tearing | |
| Hordeolum (also, stye) | A painful, localized infection or inflammation of an eyelid gland, resulting in a red, swollen lump along the eyelid’s edge | |
| Chalazion | A noninfectious bump on the eyelid caused by a blocked meibomian gland, leading to localized swelling, tenderness, and sometimes blurred vision | |
| Ptosis | Drooping of the upper eyelid due to weakened or paralyzed levator muscles, which can partially obstruct vision | |
| Ectropion | Outward turning of the lower eyelid, leading to exposure of the inner eyelid and increased risk of dryness and irritation | |
| Exophthalmos | One or both eyeballs bulge or protrude abnormally from the eye sockets (orbits) |
The nurse is performing an assessment on a child who is being seen in the primary care office for red, itchy eyes. The nurse asks a series of questions to determine if the patient felt like they had something in their eye, experience seasonal allergies, and if there had been any discharge from the eye. The patient denied foreign bodies in the eye and allergies; however, the patient did mention the eye was crusted over with a yellow crust that morning upon waking up. The nurse analyzed the cues to hypothesize the patient was most likely experiencing conjunctivitis (pink eye).
Abnormalities of the Internal Eye
Abnormalities of the internal eye refer to various disorders and conditions that affect the structures within the eye, including the retina, optic nerve, vitreous humor, and other components. These abnormalities can lead to changes in vision, visual disturbances, and potential vision loss. Common abnormalities of the internal eye include the following:
- Pterygium: A pterygium is a growth of tissue on the conjunctiva that can extend onto the cornea, often caused by excessive ultraviolet (UV) light exposure and leading to redness, irritation, and potential visual disturbances.
- Corneal abrasions or scars: A corneal abrasion is a scratch or injury to the cornea’s surface, while a corneal scar is tissue that forms after the healing of a deeper injury. Both can cause pain, discomfort, and changes in vision.
- Cataracts: A cataract is a clouding of the eye’s natural lens, leading to gradual vision loss, glare sensitivity, and decreased color perception (Figure 22.20).
- Irregularly shaped iris: An irregularly shaped iris is observed when the colored part of the eye that surrounds the pupil has irregular contours, which can be congenital or associated with certain eye conditions.
- Mydriasis: In mydriasis , there is abnormal dilation of the pupil, often due to medication, neurological issues, or eye trauma (Figure 22.21).
- Anisocoria: In anisocoria , there are unequal pupil sizes in both eyes, which can be normal or a sign of underlying neurological or eye problems.
- Miosis: In miosis , there is abnormal constriction of the pupil, often due to medication, bright light, or neurological conditions.
- Papilledema: In papilledema , there is swelling of the optic disc at the back of the eye due to increased intracranial pressure, which can be a sign of serious conditions like intracranial tumors or head injuries.
- Glaucoma: The term glaucoma is used for a group of eye disorders characterized by increased intraocular pressure that damages the optic nerve, causing gradual peripheral vision loss and potential blindness (Figure 22.22).
- Optic atrophy: In optic atrophy , there is degeneration of the optic nerve fibers, leading to vision loss and pale optic discs on examination.
- Macular degeneration: In macular degeneration , there is gradual and progressive damage to the macula, which can lead to significant vision loss and impairment of daily activities that require clear central vision, such as reading and recognizing faces (Figure 22.23).
Visual Abnormalities
Common visual abnormalities that individuals might experience include the following:
- Myopia (nearsightedness): In myopia (nearsightedness) , distant objects appear blurry, while close objects are clear. It occurs when light focuses in front of the retina instead of directly on it.
- Hyperopia (farsightedness): In hyperopia (farsightedness) , distant objects are clearer than close ones. Light focuses behind the retina instead of directly on it.
- Astigmatism: With an astigmatism , blurred or distorted vision is due to an irregularly shaped cornea or lens, causing light to focus on multiple points rather than a single point.
- Presbyopia: In the age-related condition presbyopia , an individual has difficulty focusing on close objects due to a gradual loss of the eye’s ability to change focus.
- Color blindness: Individuals with color blindness have difficulty distinguishing certain colors, often red and green or blue and yellow, due to a genetic deficiency in color-sensitive cone cells.
- Amblyopia (lazy eye): In amblyopia (also, lazy eye) , there is reduced vision in one eye due to improper development during childhood, often caused by unequal refractive errors or strabismus (misaligned eyes).
- Strabismus: Individuals with strabismus have misalignment of the eyes, causing one eye to turn inward, outward, upward, or downward while the other eye remains focused.
- Diplopia (double vision): When an individual has diplopia (double vision), they see two images of a single object. This is often caused by misalignment of the eyes, neurological issues, or eye muscle problems.
- Floater: A floater is a small, semitransparent spot or shape that appears to “float” in the field of vision due to debris in the vitreous humor.
- Flash: A flash is a brief, flickering light or sensation that occurs in the visual field, often caused by traction on the retina or vitreous humor.
- Photophobia: An individual who has photophobia has sensitivity to light, leading to discomfort and squinting in bright environments.
- Night blindness: An individual who has night blindness has difficulty seeing in low-light conditions due to reduced function of the rod cells in the retina.
- Halo: A halo is a glowing circle or ring around a light source, often seen by individuals with cataracts or after refractive surgery.