The comprehensive eye examination involves a series of tests evaluating vision as well as the general health of the eyes and includes screening for ophthalmologic diseases or ocular manifestation of systemic diseases.
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Measure visual acuity, noting:
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Near vision
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Distant vision
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Peripheral vision
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- 2.
Inspect the eyebrows for
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Hair texture
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Size
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Extension to temporal canthus
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- 3.
Inspect the orbital area for
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Edema
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Redundant tissues or edema
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Lesions
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Inspect the eyelids for
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Ability to open wide and close completely
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Eyelash position
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Ptosis
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Fasciculations or tremors
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Flakiness
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Redness
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Swelling
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Palpate the eyelids for nodules.
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Inspect the orbits
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Pull down the lower lids and inspect palpebral conjunctivae, bulbar conjunctiva, and sclerae for
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Color
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Discharge
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Lacrimal gland punctum
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Pterygium
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- 8.
Inspect the external eyes for
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Corneal clarity
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Corneal sensitivity
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Corneal arcus
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Color of irides
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Pupillary size and shape
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Pupillary response to light and accommodation, afferent pupillary defect
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Nystagmus
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- 9.
Palpate the lacrimal gland in the superior temporal orbital rim
- 10.
Evaluate muscle balance and movement of eyes
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Corneal light reflex
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Cover-uncover test
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Six cardinal fields of gaze
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- 11.
Ophthalmoscopic examination:
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Lens clarity
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Retinal color and lesions
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Characteristics of blood vessels
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Disc characteristics
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Macula characteristics
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Depth of anterior chamber
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Anatomy and Physiology
The eye is the sensory organ that transmits visual stimuli to the brain for interpretation ( Fig. 12.1 ). It occupies the orbital cavity; only its anterior aspect is exposed. The eye itself is a direct embryologic extension of the brain.
There are four rectus and two oblique muscles attached to the eye ( Fig. 12.2 ). Cranial nerve (CN) II, the optic nerve, connects the eye to the brain.
External Eye
The external eye is composed of the eyelid, conjunctiva, lacrimal gland, eye muscles, and the bony orbit. The orbit also contains fat, blood vessels, nerves, and supporting connective tissue (see Fig. 12.1 ).
Eyelid
The eyelid is composed of skin, striated muscle, the tarsal plate, and conjunctivae. Meibomian glands in the eyelid provide oils to the tear film. The tarsus provides a skeleton for the eyelid. The eyelid distributes tears over the surface of the eye, limits the amount of light entering it, and protects the eye from foreign bodies. Eyelashes extend from the anterior border of each lid.
Conjunctiva
The conjunctiva is a clear, thin mucous membrane. The palpebral conjunctiva coats the inside of the eyelids. The bulbar (or ocular) conjunctiva covers the outer surface of the eye. The bulbar conjunctiva protects the anterior surface of the eye with the exception of the cornea and the surface of the eyelid in contact with the globe.
Lacrimal Gland
The lacrimal gland is located in the temporal region of the superior eyelid and produces tears that moisten the eye ( Fig. 12.3 ). Tears flow over the cornea and drain via the canaliculi to the lacrimal sac and duct and then into the nasal meatus.
Eye Muscles
Each eye is moved by six muscles—the superior, inferior, medial, and lateral rectus muscles and the superior and inferior oblique muscles (see Figs. 12.2 and 12.22 ). They are innervated by CNs III (oculomotor), IV (trochlear), and VI (abducens). The oculomotor nerve controls the levator palpebrae superioris (which elevates and retracts the upper eyelid) and all extraocular muscles except for the superior oblique muscle and the lateral rectus muscle. The superior oblique is the only muscle innervated by the trochlear nerve and the lateral rectus muscle is the only muscle innervated by the abducens nerve.
Internal Eye
The internal structures of the eye are composed of three separate layers. The outer wall of the eye is composed of the sclera posteriorly and the cornea anteriorly. The middle layer or uvea consists of the choroid posteriorly and the ciliary body and iris anteriorly. The inner layer of nerve fibers is the retina (see Fig. 12.1 ).
Sclera
The sclera is the dense, avascular structure that appears anteriorly as the white of the eye. It physically supports the internal structure of the eye.
Cornea
The cornea constitutes the anterior sixth of the globe and is continuous with the sclera. It is optically clear, has rich sensory innervation, and is avascular. It is a major part of the refractive power of the eye.
Uvea
The iris, ciliary body, and choroids comprise the uveal tract (see Fig. 12.1 ). The iris is a circular, contractile muscular disc containing pigment cells that produce the color of the eye. The central aperture of the iris is the pupil, through which light travels to the retina. By dilating and contracting, the iris controls the amount of light reaching the retina. The ciliary body produces the aqueous humor (fluid that circulates between the lens and cornea) and contains the muscles controlling accommodation. The choroid is a pigmented, richly vascular layer that supplies oxygen to the outer layer of the retina.
Lens
The lens is a biconvex, transparent structure located immediately behind the iris (see Fig. 12.1 ). It is supported circumferentially by fibers arising from the ciliary body. The lens is highly elastic, and contraction or relaxation of the ciliary body changes its thickness, thereby permitting images from varied distances to be focused on the retina.
Retina
The retina is the sensory network of the eye. Photoreceptors and neurons transform light impulses into electrical impulses, which are transmitted through the optic nerve, optic tract, and optic radiation to the visual cortex in the brain and then to interpretation in the cerebral cortex. The optic nerve passes through the optic foramen along with the ophthalmic artery and vein. The optic nerve communicates with the brain and the autonomic nervous system of the eye. Accurate binocular vision is achieved when an image is fused on the retina by the cornea and the lens. An object may be perceived in each visual cortex, even when one eye is covered, if the light impulse is cast on both the temporal and the nasal retina. Fibers located on the nasal retina decussate in the optic chiasm ( Fig. 12.4 ). Accurate binocular vision also requires the synchronous functioning of the extraocular muscles.
Major landmarks of the retina include the optic disc, from which the optic nerve originates, together with the central retinal artery and vein. The macula, or fovea, is the site of central vision (see Fig. 12.1 ).
Infants and Children
The eyes develop during the first 8 weeks of gestation and may become malformed due to maternal drug and alcohol use or infection during this time. The development of vision, which is dependent on maturation of the nervous system, occurs over a longer period ( Table 12.1 ). Term infants are hyperopic, with a visual acuity of less than 20/400 (see Visual Acuity Testing ). Although peripheral vision is fully developed at birth, central vision matures later. One of the earliest visual responses is the infant’s regard for the mother’s face. By 2 to 3 weeks of age, many infants will show an interest in large objects. Lacrimal drainage is complete at the time of term birth, and by 2 to 3 weeks of age the lacrimal gland begins producing a full volume of tears. By 3 to 4 months of age, binocular vision development is complete. By 6 months, vision has developed sufficiently so that the infant can differentiate colors.
| AGE | LEVELS OF DEVELOPMENT |
|---|---|
| Birth | Awareness of light and dark; infant closes eyelids in bright light Visual acuity 20/670 (6/200) |
| Neonatal | Rudimentary fixation on near objects, able to regard mother’s face |
| 2 weeks | Transitory fixation, usually monocular at a distance of roughly 3 feet Follows large, conspicuously moving objects |
| 4 weeks | Visual acuity 20/550 (6/160) Moving objects evoke binocular fixation briefly |
| 6 weeks | Follows moving objects with jerky eye movements |
| 8 weeks | Visual following now achieved by a combination of head and eye movements Visual acuity 20/150 (6/45) |
| 12 weeks | Visual acuity 20/230 (6/70) Enjoys light objects and bright colors Beginning of depth perception Fusion of images begins to appear |
| 16 weeks | Visual acuity 20/60 (6/18) Fixates immediately on moving target, visually pursues dropped toy |
| 20 weeks | Shows interest in stimuli more than 3 feet away Retrieves a dropped 1-inch cube Can maintain voluntary fixation of stationary object even in the presence of competing moving stimulus |
| 24 weeks | Visual acuity reaches healthy adult level 20/100 (6/6) (6/30) Can maintain voluntary fixation of stationary object even in the presence of competing moving stimulus Hand-eye coordination appearing Will fixate on a string Binocular fixation clearly established |
| 26 weeks | Marked interest in tiny objects |
| 28 weeks | Tilts head backward to gaze up |
| 40 weeks | Discriminates simple geometric forms (squares and circles) |
| Looks at pictures with interest | |
| 1 year | Visual acuity 20/60 (6/20) Convergence well established Localization in distance crude—runs into large objects |
| 3 years | Visual acuity 20/50 (6/15) |
Young children become less hyperopic with growth. The globe of the eye grows as the child’s head and brain grow, and adult visual acuity is achieved at about 4 years of age.
Pregnant Patients
The eyes undergo several changes during pregnancy because of physiologic and hormonal adaptations. These changes can result in hypersensitivity and can change the refractory power of the eye. Tears contain an increased level of lysozyme, resulting in a greasy sensation and perhaps blurred vision for contact lens wearers. Diabetic retinopathy may worsen significantly. Mild corneal edema and thickening associated with blurred vision may occur, especially in the third trimester. Intraocular pressure falls most notably during the latter half of pregnancy.
Older Adults
The major physiologic eye change that occurs with aging is a progressive weakening of accommodation (focusing power) known as presbyopia. In general, by 45 years of age, the lens becomes more rigid, and the ciliary muscle becomes weaker. The lens also continues to form fibers throughout life. Old fibers are compressed centrally, forming a denser central region that may cause loss of clarity of the lens and contribute to cataract formation (clouding of the lens that can become partially or totally opaque; see Fig. 12.41 ). See Risk Factors, “Cataract Formation .”
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Family history of cataracts
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Steroid medication use
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Exposure to ultraviolet light
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Cigarette smoking
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Diabetes mellitus
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Aging
Review of Related History
For each of the symptoms or conditions discussed in this section, targeted topics to include in the history of the present illness are listed. Responses to questions about these topics provide clues for focusing the physical examination and the development of an appropriate diagnostic evaluation. Questions regarding medication use (prescription and over the counter preparations) as well as complementary and alternative therapies are relevant for each.
History of Present Illness
Red Eye (Presence of Conjunctival Injection or Redness)
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Difficulty with vision: one or both eyes, corrected by lenses
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Recent injury or foreign bodies; sleeping in contact lenses
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Pain: with or without loss of vision, in or around the eye, superficial or deep, insidious or abrupt in onset; burning, itching, or nonspecific uncomfortable or gritty sensation
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History of swelling, infections, or eye surgery
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History of recent illness or similar symptoms in the household
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Allergies: type, seasonal, associated symptoms
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Eye secretions: color (clear or yellow), consistency (watery or purulent), duration, tears that run down the face, decreased tear formation (with sensation of gritty eyes)
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Medications: eye drops or ointments, antibiotics, artificial tears, mydriatics; glaucoma medications, antioxidant vitamins (to prevent macular degeneration), steroids (which promote cataract formation)
Vision Problem(s)
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Eyelids: recurrent hordeola (stye; acute infection of sebaceous glands of Zeis), chalazion (chronic blockage of meibomian gland), ptosis of the lids so that they interfere with vision (unilateral or bilateral), growths or masses, itching
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Double vision: oculomotor, trochlear, or abducens nerve deficit
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Involves one or both eyes, corrected by lenses, involving near or distant vision, primarily central or peripheral, transient or sustained
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Cataracts (bilateral or unilateral), types (e.g., infantile, senile, diabetic, traumatic, surgical treatment)
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Adequacy of color vision
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Presence of halos around lights, floaters, or diplopia (when one eye is covered or when both eyes are open)
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Sudden loss of vision or portion of visual field: transient ischemic attack, stroke, amaurosis fugax (painless temporary loss of vision in one or both eyes)
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Trauma: to the eye as a whole or a specific structure (e.g., cornea) or supporting structures (e.g., the floor of the orbit); events surrounding the trauma; efforts at correction and degree of success
Past Medical History
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Eye surgery: condition requiring surgery, cataract removal, laser vision correction, date of surgery, outcome
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Chronic illness that may affect eyes or vision: glaucoma, diabetes, atherosclerotic cardiovascular disease (ASCVD), hypertension, thyroid dysfunction, autoimmune diseases, human immunodeficiency virus (HIV), inflammatory bowel diseases
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Medications: steroids, hydroxychloroquine, antihistamines, antidepressants, antipsychotics, antiarrhythmics, immunosuppressants, glaucoma eye drops, beta-blockers
Family History
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Retinoblastoma (often an autosomal dominant disorder)
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Glaucoma, macular degeneration, diabetes, hypertension, or other diseases that may affect vision or eye health
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Cataracts
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Color blindness, retinal detachment, retinitis pigmentosa, or allergies affecting the eye
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Nearsightedness, farsightedness, strabismus, or amblyopia
Personal and Social History
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Employment: exposure to irritating gases, chemicals, foreign bodies, or high-speed machinery
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Activities: participation in sporting activities that might endanger the eye (e.g., boxing, lacrosse, hockey, basketball, football, paintball, martial arts, rifle shooting, racquetball, fencing, motorcycle riding)
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Use of protective devices during work or activities that might endanger the eye
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Corrective lenses: type (glasses or contact lenses), when last changed, how long worn, adequacy of corrected vision; methods of cleaning and storage or frequency of disposal, insertion and removal procedures of contact lenses; sleeping with contact lenses in
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Date of last eye examination, history of corrective surgery (e.g., Lasik)
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History of cigarette smoking (a risk factor for cataract formation, glaucoma, macular degeneration, thyroid eye disease)
Infants and Children
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Preterm: resuscitative efforts, mechanical ventilation or oxygen use, retinopathy of prematurity, birth weight, gestational age, sepsis, intracranial hemorrhage
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Maternal history of sexually transmitted infections, Zika virus, TORCH (toxoplasmosis, Other [syphilis, varicella-zoster, parvovirus B-19], rubella, cytomegalovirus, and herpes) infections
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Congenital abnormalities of the eye or surrounding structures (e.g., hemangioma)
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Symptoms of congenital abnormalities including failure of infant to gaze at mother’s face or other objects; failure of infant to blink when bright lights or threatening movements are directed at the face
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White area in the pupil on examination or on a photograph (leukocoria); inability of one eye to reflect light properly (may indicate retinoblastoma or other serious intraocular problem)
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Excessive tearing or discharge, erythema
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Strabismus some or all of the time; frequency; when first noted; occurring when fatigued, sick, or otherwise stressed; associated with frequent blinking or squinting, nystagmus
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Young children: excessive rubbing of the eyes, frequent hordeola, inability to reach for and pick up small objects, night vision difficulties
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School-age children: necessity of sitting near the front of the classroom to see the teacher’s work; poor school performance not explained by intellectual ability
Pregnant Patients
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Presence of disorders that can cause ocular complications such as pregnancy-induced hypertension (PIH) or gestational diabetes; symptoms indicative of PIH: diplopia, scotomata, blurred vision, or amaurosis fugax
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Use of topical eye medications (may cross the placental barrier)
Older Adults
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Visual acuity: decrease in central vision, distortion of central vision, use of dim or bright light to increase visual acuity, difficulty with glare; difficulty in performing near work without lenses
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Excess tearing
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Dry eyes
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Nocturnal eye pain (sign of subacute angle closure and a symptom of glaucoma)
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Difficulty with depth perception
Examination and Findings
Equipment
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Snellen chart or Lea Cards, Landolt C, or HOTV chart (see Chapter 3 and Fig. 3.17 A, B )
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Rosenbaum or Jaeger near vision card (see Chapter 3 )
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Penlight
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Cotton wisp
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Ophthalmoscope (see Chapter 3 and Figs. 3.13 and 3.15 )
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Eye cover, gauze, or opaque card
Visual Acuity Testing
Measurement of visual acuity—the discrimination of small visual details—tests CN II (optic nerve) and is essentially a measurement of central vision. This important assessment is often inappropriately neglected by examiners who are not ophthalmologists. Position the patient 20 feet (6 m) away from the Snellen chart (see Fig. 3.17 ). Make sure the chart is well lighted. Alternatively, special charts for use 10 feet (3 m) away from the patient are available. Test each eye individually by covering one eye with an opaque card or gauze, being careful to avoid applying pressure to the eye. If you test the patient with and without corrective lenses, record the readings separately. Always test vision without glasses first.
Ask the patient to identify all of the letters, beginning at any line. Determine the smallest line in which the patient can identify all of the letters and record the visual acuity designated by that line. (For more information, see Chapter 3 .) When testing the second eye, you may want to ask the patient to read the line from right to left to reduce the chance of recall influencing the response. Conduct the test rapidly enough to prevent the patient from memorizing the chart. However, avoid going too quickly when asking that the lines on the chart be read. It is wise to pace the assessment slowly for patient comfort and to allow time for the patient to reason out a response. Visual acuity is recorded as a fraction in which the numerator indicates the distance of the patient from the chart (e.g., 20 feet or 6 m), and the denominator indicates the distance at which the average eye can read the line. Thus 20/200 (6/60) means that the patient can read at 20 feet (6 m) what the average person can read at 200 feet (60 m). The smaller the fraction, the worse is the vision. Vision not correctable to better than 20/200 is considered legal blindness (see Clinical Pearl, “Is It Blurry or Is It Double? ”).
Perform a pinhole test if the visual acuity is recorded at a fraction less than 20/20 (or 6/6), to see if the observed decrease in acuity was caused by a refractive error. Ask the patient to hold a pinhole occluder (or a piece of paper with a small hole in it) over the uncovered eye. This maneuver permits light to enter only the central portion of the lens. Expect an improvement in visual acuity by at least one line on the chart if refractive error is responsible for the diminished acuity (see Clinical Pearl, “Factors That Affect Visual Acuity Testing ”).
Blurred vision and diplopia are sometimes confused by the patient. Blurred vision represents a problem with visual acuity, and there are many causes. Diplopia is the perception of two images and may be monocular or binocular. Monocular diplopia is an optical problem; binocular diplopia is an alignment problem.
Testing of visual acuity involves many complex factors not necessarily related to the ability to see the test object. Motivation and interest, as well as literacy, intelligence, and attention span, can modify the results of sensory testing.
Measurement of near vision should be tested in each eye separately with a handheld card such as the Rosenbaum Pocket Vision Screener. Have the patient hold the card at a comfortable distance (about 35 cm, or 14 inches) from the eyes and read the smallest line possible.
Peripheral vision can be accurately measured with sophisticated instruments, but is generally estimated by the confrontation test. Sit or stand opposite the patient at eye level at a distance of about 1 m (3 feet). Ask the patient to cover the right eye while you cover your left eye, so the open eyes are directly opposite each other ( Fig. 12.5 ). Both you and the patient should be looking at each other’s eye. Fully extend your arm midway between the patient and yourself and then wiggle your fingers as you move your arm slowly centrally. Have the patient tell you when the fingers are first seen. Compare the patient’s response to the time you first note the fingers. Test the nasal, temporal, superior, and inferior fields. Remember that the nose itself interferes with the nasal portion of the visual field. Unless you are aware of a problem with your vision, you can feel comfortable that the fields are full if they correspond with yours. The confrontation test is imprecise and can be considered significant only when it is abnormal. Lesions most likely to produce confrontation abnormalities include stroke, retinal detachment, optic neuropathy, pituitary tumor compression at the optic chiasm, and central retinal vascular occlusion.
Color vision is rarely tested in the routine physical examination. Color plates are available in which numerals are produced in primary colors and surrounded by confusing colors. The patient is asked to read the numbers. The tests vary in degree of difficulty. For routine testing, check the patient’s ability to appreciate primary colors. Red testing may be particularly helpful in determining subtle optic nerve disease, even when visual acuity remains nearly normal. An afferent pupillary defect (discussed later in the chapter) often coexists with a red defect.
External Examination
Carry out examination of the eyes in a systematic manner, beginning with the appendages (i.e., the eyebrows and surrounding tissues) and moving inward.
Surrounding Structures
Inspect the eyebrows for size, extension, and texture of the hair. Note whether the eyebrows extend beyond the eye itself or end short of it. If the patient’s eyebrows are coarse or do not extend beyond the temporal canthus, the patient may have hypothyroidism. If the brows appear unusually thin, ask if the patient waxes or plucks them.
Inspect the orbital and periorbital area for edema, puffiness, or redundant tissue below the orbit. Although puffiness may represent the loss of elastic tissue that occurs with aging, periorbital edema is always abnormal; the significance varies directly with the amount. It may represent the presence of thyroid eye disease, allergies, or the presence of renal disease (nephrotic syndrome) or heart disease (congestive heart failure). You may see flat to slightly raised, oval, irregularly shaped, yellow-tinted lesions on the periorbital tissues that represent depositions of lipids and may suggest that the patient has an abnormality of lipid metabolism. These lesions, xanthelasma ( Fig. 12.6 ), are an elevated plaque of cholesterol deposited in macrophages, most commonly in the nasal portion of the upper or lower lid.
Eyelids
Examine the patient’s lightly closed eyes for fasciculations or tremors of the lids, a sign of hyperthyroidism. Inspect the eyelids for their ability to close completely and open widely. Observe for flakiness, redness, or swelling on the eyelid margin. Eyelashes should be present on both lids and should curve away from the globe.
When the eye is open, the superior eyelid should cover a portion of the iris but not the pupil itself. If one superior eyelid covers more of the iris than the other or extends over the pupil, then ptosis of that lid is present. Ptosis indicates a congenital or acquired weakness of the levator muscle or a paresis of a branch of the third cranial nerve ( Fig. 12.7 ). Record the difference between the two lids in millimeters. The average upper lid position is 2 mm below the limbus (the border of the cornea and the sclera), and the average lower lid position is at the lower limbus.
You should also note whether the lids evert or invert. When the lower lid is turned away from the eye, it is called ectropion and may result in excessive tearing ( Fig. 12.8 ). The inferior punctum, which serves as the tear-collecting system, is pulled outward and the lower lid cannot collect the secretions of the lacrimal gland.
When the lid is turned inward toward the globe, a condition known as entropion ( Fig. 12.9 ), the lid’s eyelashes may cause corneal and conjunctival irritation, increasing the risk of a secondary infection. The patient often reports a foreign body sensation.
An acute suppurative inflammation of the follicle of an eyelash can cause an erythematous or yellow lump. This hordeolum or stye is generally caused by a staphylococcal infection ( Fig. 12.10 ).
Crusting along the eyelashes may represent blepharitis caused by bacterial infection, seborrhea, psoriasis, a manifestation of rosacea, or an allergic response ( Fig. 12.11 ).
Ask the patient to close the eyes, and note whether the eyelids meet completely. If the closed lids do not completely cover the globe (a condition called lagophthalmos ), the cornea may become dried and be at increased risk of infection. Thyroid eye disease, seventh nerve palsy (Bell palsy), and overaggressive ptosis or blepharoplasty surgical repair are common causes.
Palpation
Palpate the eyelids for nodules. Palpation of the orbit is one of the simplest methods for intraocular pressure assessment. Gentle palpation through closed lids (digital palpation tonometry) can confirm that the involved eye is much harder than the uninvolved eye. Determine whether the orbit can be gently pushed into the orbit without discomfort. Pain on palpation is consistent with scleritis, orbital cellulitis, and cavernous sinus thrombosis. An eye that feels very firm and resists palpation may indicate severe glaucoma or retrobulbar tumor.
Conjunctiva
The conjunctivae are usually translucent and free of erythema. Inspect the palpebral conjunctiva by having the patient look upward while you draw the lower lid downward noting translucency and vascular pattern ( Fig. 12.12 ).
Inspect the upper tarsal conjunctiva only when there is a suggestion that a foreign body may be present. Ask the patient to look down while you pull the eyelashes gently downward and forward to break the suction between the lid and globe. Next, evert the lid on a small cotton-covered applicator ( Fig. 12.13 ). After you inspect and remove any foreign body that may be present, return the eyelid to its regular position by asking the patient to look up while you apply downward pressure against the eyelid.
Observe the conjunctiva for erythema or exudate. An erythematous or cobblestone appearance, especially on the tarsal conjunctiva, may indicate an allergic ( Fig. 12.14 ) or infectious conjunctivitis ( Fig. 12.15 ). Bright red blood in a sharply defined area surrounded by healthy-appearing conjunctiva indicates subconjunctival hemorrhage ( Fig. 12.16 ). The blood stays red because of direct diffusion of oxygen through the conjunctiva. Subconjunctival hemorrhages may occur with violent coughing, powerful sneezing, straining as during a constipated bowel movement, intractable vomiting, and spontaneously in pregnancy or during labor. Other causes include trauma, foreign objects, and aggressive rubbing of the eye. The hemorrhages resolve spontaneously.
A pterygium is an abnormal growth of conjunctiva that extends over the cornea from the limbus. It occurs more commonly on the nasal side ( Fig. 12.17 ) but may arise temporally as well. A pterygium is more common in people heavily exposed to ultraviolet light. It can interfere with vision if it advances over the pupil.
Cornea
Examine the cornea for clarity by shining a light tangentially on it. Because the cornea is normally avascular, blood vessels should not be present. Corneal sensitivity, controlled by CN V (trigeminal nerve), is tested by touching a wisp of cotton to the cornea ( Fig. 12.18 ). The expected response is a blink, which indicates intact sensory fibers of CN V and motor fibers of CN VII (facial nerve). Decreased corneal sensation is often associated with diabetes, herpes simplex and herpes zoster viral infections or is a sequela of trigeminal neuralgia or ocular surgery.
You may note a corneal arcus (arcus senilis), which is composed of lipids deposited in the periphery of the cornea. It may in time form a complete circle (circus senilis) ( Fig. 12.19 . Note the subtle clear area between the limbus and the arcus. An arcus is seen in many individuals older than 60 years. If present before age 40, arcus senilis may indicate a lipid disorder. It is possible to have more than one process; Fig. 12.20 demonstrates both corneal circus senilis and a pterygium.
