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Examination of the eye can be undertaken with routine equipment, including a standard ophthalmoscope; thorough examination requires special equipment and evaluation by an ophthalmologist. (See Fig. 1: Approach to the Ophthalmologic Patient: Cross-section of the eye. for a cross-section of the eye.)

Fig. 1
Cross-section of the eye. The zonules of Zinn keep the lens suspended, and the muscles of the ciliary body focus the lens. The ciliary body also secretes aqueous humor, which fills the anterior and posterior chambers, passes through the pupil into the anterior chamber, and drains primarily via Schlemm's canal (see Fig. 1: Glaucoma: Aqueous humor production and flow.). The iris regulates the amount of light entering the eye by adjusting the size of its central opening, the pupil. Visual images are focused on the retina. The fovea centralis is the area of sharpest visual acuity. The conjunctiva covers the eyeball and lines the upper and lower eyelids; it ends at the limbus. The cornea is covered with an epithelium that is more sensitive than and differs from the conjunctival epithelium.

History

History provides information on the location, speed of onset, and duration of current symptoms and history of previous ocular symptoms; the presence and nature of pain, discharge, or redness; and changes in visual acuity. Worrisome symptoms besides vision loss and eye pain include flashing lights, showers of floaters (both of which may be symptoms of retinal detachment), diplopia, and loss of peripheral vision.

Physical Examination

Visual acuity: The first step is to record visual acuity. Patients who require corrective lenses should wear them during testing. However, if patients do not have their required corrective lenses with them, distance visual acuity can be tested by having them look through a pinhole device (a paddle with multiple pinholes or an index card with an array of 18-gauge needle punctures); these holes focus light rays and compensate for refractive error.

Visual acuity in each eye is tested as the opposite eye is covered. Patients look at an eye chart 20 ft (6 m) away. Normal and abnormal vision is quantified by Snellen notation. A Snellen notation of 20/40 (6/12) indicates that the smallest letter that can be read by someone with normal vision at 40 ft (12 m) has to be brought to 20 ft (6 m) before it is recognized by the patient. Vision is recorded as the smallest letter patients read correctly, even if patients feel that the letter is blurry or they have to guess. Near vision is checked by asking the patients to read a standard near card or newsprint at 14 in (35 cm); patients > 40 yr who require corrective lenses (reading glasses) should wear them during near vision testing.

Refractive error can be estimated roughly with a handheld ophthalmoscope by noting the lens necessary for the examiner to focus on the retina; this procedure requires examiners to use their own corrective lenses and is never a substitute for a comprehensive assessment of refraction. More commonly, refractive error is measured with a standard phoropter or an automated refractor (a device that measures changes in light projected and reflected by the patient's eye). These devices also measure astigmatism (see Refractive Error: Introduction).

Eyelid and conjunctival examination: Eyelid margins and periocular cutaneous tissues are examined under a focal light and magnification (eg, provided by loupe, slit lamp, or ophthalmoscope focused at the examiner's working distance). In cases of suspected dacryocystitis or canaliculitis, the lacrimal sacs are palpated and an attempt is made to express any contents through the canaliculi and puncta. After eyelid eversion, the palpebral and bulbar conjunctivae and the fornices can be inspected for foreign bodies, signs of inflammation (eg, follicular hypertrophy, exudate, hyperemia, edema), or other abnormalities.

Corneal examination: Indistinct or blurred edges of the corneal light reflex (reflection of light from the cornea when illuminated) suggest the corneal surface is not intact or is roughened, as occurs with a corneal abrasion or keratitis. Fluorescein staining reveals abrasions and ulcers. Before staining, a drop of topical anesthetic (eg, proparacaine Some Trade Names
ALCAINE
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0.5% or tetracaine Some Trade Names
PONTOCAINE NIPHANOID
PONTOCAINE
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0.5%) may be added to facilitate examination if the patient is in pain or if it is necessary to touch the cornea or conjunctiva (eg, to remove a foreign body or measure intraocular pressure). A sterile, individually packaged fluorescein strip is moistened with 1 drop of sterile saline or topical anesthetic and, with the patient's eye turned upward, is touched momentarily to the inside of the lower eyelid. The patient blinks several times to spread the dye into the tear film, and then the eye is examined under magnification and cobalt blue illumination. Areas where corneal or conjunctival epithelium is absent (abraded or ulcerated) fluoresce green.

Pupil examination: The size and shape of the pupils are noted, and pupillary reaction to light is tested in each eye, one at a time, while the patient looks in the distance. Then the swinging flashlight test is done with a penlight to compare direct and consensual pupillary response. There are 3 steps:

1. One pupil is maximally constricted by being exposed to light from the penlight for 1 to 3 sec.
2. The penlight is rapidly moved to the other eye for 1 to 3 sec.
3. The light is moved back to the first eye.

Normally, a pupil constricts similarly when light is shone on it (direct response) and when light is shone on the other eye (consensual response). However, if one eye has less light perception than the other, such as from dysfunction of the afferent limb (from the optic nerve to the optic chiasm) or extensive retinal disease, then the consensual response in the affected eye is stronger than the direct response. Thus, on step 3 of the swinging light test, when the light is shone back on it, the pupil of the affected eye paradoxically appears to dilate. This finding indicates a relative afferent pupillary defect (RAPD or Marcus Gunn pupil).

Extraocular muscles: The examiner guides the patient to look in 8 directions (up, up and right, right, down and right, down, down and left, left, left and up) with a moving finger, penlight, or transillumination light, observing for gaze deviation, limitation of movement, disconjugate gaze, or a combination consistent with cranial nerve palsy, orbital disease, or other abnormalities that restrict movement.

Ophthalmoscopy: Ophthalmoscopy can be done directly by using a handheld ophthalmoscope or indirectly by using a head-mounted ophthalmoscope with a handheld lens. With handheld ophthalmoscopy, the examiner dials the ophthalmoscope to zero diopters, then increases or decreases the setting until the fundus comes into focus. The view of the retina is limited with a handheld ophthalmoscope, whereas indirect ophthalmoscopy gives a 3-dimensional view and is better for visualizing the peripheral retina, where retinal detachment most commonly occurs. The view of the fundus can be improved by dilating the pupils. Before dilation, the anterior chamber depth is estimated because mydriasis can precipitate an attack of acute angle-closure glaucoma if the anterior chamber is shallow. Depth can be estimated with a slit lamp (see Approach to the Ophthalmologic Patient: Slit-lamp examination) or less accurately with a penlight held at the temporal limbus parallel to the plane of the iris and pointed toward the nose. If the medial iris is in shadow, the chamber is shallow and dilation should be avoided. Other contraindications to dilation include head trauma, suspicion of a ruptured globe, a narrow angle, and angle-closure glaucoma.

Pupils can be dilated using 1 drop of tropicamide Some Trade Names
MYDRAL
MYDRIACYL
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1%, phenylephrine Some Trade Names
NEO-SYNEPHRINE
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2.5%, or both (repeated in 5 to 10 min if necessary); for longer action, a larger dilated pupil, or both, cyclopentolate Some Trade Names
AK-PENTOLATE
CYCLOGYL
CYLATE
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1% can be substituted for tropicamide Some Trade Names
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.

Ophthalmoscopy can detect lens or vitreous opacities, assess the optic cup-to-disk ratio, and identify retinal and vascular changes. The optic cup is the central depression, and the optic disk is the entire area of the optic nerve head. The normal ratio of the cup-to-nerve diameters is 0 to 0.4. A ratio of ≥ 0.5 may signify loss of ganglion cells and may be a sign of glaucoma. Retinal changes include hemorrhage, manifested as small or large areas of blood, and drusen (small subretinal yellow-white spots that may signify dry age-related macular degeneration). Vascular changes include arteriovenous nicking, a sign of chronic hypertension in which retinal veins are compressed by arteries where the two cross; copper wiring, a sign of arteriosclerosis in which thickened arteriolar walls increase the thickness of the light reflex; silver wiring, a sign of hypertension in which thin, fibrotic arteriolar walls decrease the thickness of the light reflex; and loss of venous pulsations, a sign of increased intracranial pressure in patients known to have had pulsations.

Slit-lamp examination: A slit lamp focuses the height and width of a beam of light for a precise stereoscopic view of the eyelids, conjunctiva, cornea, anterior chamber, iris, lens, and anterior vitreous. It is especially useful for the following:

• Identifying corneal foreign bodies and abrasions
• Measuring depth of the anterior chamber
• Detecting cells (RBCs or WBCs) and flare (evidence of protein) in the anterior chamber
• Identifying ciliary flush (dilation of blood vessels localized to the limbal region overlying the ciliary body), which occurs with uveitis
• Identifying scleral edema, which is seen as a bowing forward of the slit beam when it is focused beneath the conjunctiva and which is usually a sign of scleritis

Tonometry (see Approach to the Ophthalmologic Patient: Tonometry) and gonioscopy, which quantifies the iridocorneal angle and requires the use of a special lens, may be done.

Visual field testing: Visual fields may be impaired by lesions anywhere in the neural visual pathways from the optic nerves to the occipital lobes (see Table 1: Approach to the Ophthalmologic Patient: Types of Field Defects ; see Fig. 1: Approach to the Ophthalmologic Patient: Cross-section of the eye.). Glaucoma causes loss of peripheral vision. Fields can be assessed grossly by direct confrontation testing or by more precise methods, which involve more detailed testing.

In direct confrontation, patients maintain a fixed gaze at the examiner's eye or nose. The examiner brings a small target (eg, a match or a finger) from the patients' visual periphery into each of the 4 visual quadrants and asks the patients to indicate when they first see the object. Wiggling the small target helps patients separate and define it. Another method of direct confrontation visual field testing is to hold a number of fingers in each quadrant and ask patients how many they see. For both methods, each eye is tested separately. Abnormalities in target detection should prompt detailed testing with more precise instruments.

More detailed methods include use of a tangent screen, Goldmann perimeter, or computerized automated perimetry (in which the visual field is mapped out in detail based on patient response to a series of flashing lights in different locations controlled by a standardized computer program). The Amsler grid is used to test central vision. Distortion of the grid (metamorphopsia) or a missing area (central scotoma) may indicate disease of the macula (eg, choroidal neovascularization), as occurs in age-related macular degeneration.

Table 1
Types of Field Defects  Type Description Causes Altitudinal field defect Loss of all or part of the superior or inferior half of the visual field; does not cross the horizontal median More common: Ischemic optic neuropathy, hemibranch retinal artery occlusion, retinal detachment Less common: Glaucoma, optic nerve or chiasmal lesion, optic nerve coloboma Arcuate scotoma A small, bow-shaped (arcuate) visual field defect that follows the arcuate pattern of the retinal nerve fibers; does not cross the horizontal median Damage to ganglion cells that feed into a particular part of the optic nerve head More common: Glaucoma Less common: Ischemic optic neuropathy (especially nonarteritic), optic disk drusen, high myopia Binasal field defect (uncommon) Loss of all or part of the medial half of both visual fields; does not cross the vertical median More common: Glaucoma, bitemporal retinal disease (eg, retinitis pigmentosa) Rare: Bilateral occipital disease, tumor or aneurysm compressing both optic nerves Bitemporal hemianopia Loss of all or part of the lateral half of both visual fields; does not cross the vertical median More common: Chiasmal lesion (eg, pituitary adenoma, meningioma, craniopharyngioma, aneurysm, glioma) Less common: Tilted optic disks Rare: Nasal retinitis pigmentosa Blind-spot enlargement Enlargement of the normal blind spot at the optic nerve head Papilledema, optic nerve drusen, optic nerve coloboma, myelinated nerve fibers at the optic disk, drugs, myopic disk with a crescent Central scotoma A loss of visual function in the middle of the visual field Macular disease, optic neuropathy (eg, ischemic or Leber's hereditary neuropathy, optic neuritis-multiple sclerosis), optic atrophy (eg, due to tumor compressing the nerve or toxic/metabolic disease) Rare: Occipital cortex lesion Constriction of the peripheral fields, leaving only a small residual central field Loss of the outer part of the entire visual field in one or both eyes Glaucoma, retinitis pigmentosa or another peripheral retinal disorder, chronic papilledema after panretinal photocoagulation, central retinal artery occlusion with cilioretinal artery sparing, bilateral occipital lobe infarction with macular sparing, nonphysiologic vision loss, carcinoma-associated retinopathy Rare: Drugs Homonymous hemianopia Loss of part or all of the left half or right half of both visual fields; does not cross the vertical median Optic tract or lateral geniculate body lesion; lesion in temporal, parietal, or occipital lobe (more commonly, stroke or tumor; less commonly, aneurysm or trauma); migraine (which may cause transient homonymous hemianopia) Adapted from Rhee DJ, Pyfer MF: The Wills Eye Manual, ed. 3. Philadelphia, Lippincott Williams & Wilkins, 1999.

Color vision testing: Twelve to 24 Ishihara color plates, which have colored numbers or symbols hidden in a field of colored dots, are commonly used to test color vision. Color-blind patients or those with acquired color deficiency (eg, in optic nerve diseases) cannot see some or all of the hidden numbers. Most congenital color blindness is red-green; most acquired (eg, caused by glaucoma or optic nerve disease) is blue-yellow.

Testing

Tonometry: Tonometry measures intraocular pressure by determining the amount of force needed to indent the cornea. Handheld pen-type tonometers are used for screening. This test requires topical anesthesia (eg, proparacaine Some Trade Names
ALCAINE
OPHTHETIC
Click for Drug Monograph
0.5%). Office-based screening with noncontact air-puff tonometry also can be used; it requires less training because it makes no direct corneal contact. Goldmann applanation tonometry is the most accurate method but requires more training and typically is used only by ophthalmologists. Measurement of intraocular pressure alone is not adequate screening for glaucoma; the optic nerve also should be examined.

Fluorescein angiography: After IV injection of fluorescein solution, the retinal, choroidal, optic disk, or iris vasculature is photographed in rapid sequence. Fluorescein angiography is used to investigate underperfusion and neovascularization in conditions such as diabetes, age-related macular degeneration, retinal vascular occlusion, and ocular histoplasmosis. It is also useful in preoperative assessment for retinal laser procedures.

Electroretinography: Electrodes are placed on each cornea and on the surrounding skin, and electrical activity in the retina is recorded. This technique evaluates retinal function in patients with retinal degeneration. It does not evaluate vision.

Ultrasonography: B-mode ultrasonography provides 2-dimensional structural information even in the presence of opacities of the cornea and lens. Examples of ophthalmologic applications include assessment of retinal tumors, detachments, and vitreous hemorrhages; location of foreign bodies; detection of posterior scleral edema characteristic of posterior scleritis; and distinction of choroidal melanoma from metastatic carcinoma and subretinal hemorrhage.

A-mode ultrasonography is 1-dimensional ultrasound used to determine the axial length of the eye, a measurement needed to calculate the power of an intraocular lens for implantation as a part of cataract surgery.

Ultrasonic pachymetry is use of ultrasonography to measure the thickness of the cornea before refractive surgery (eg, LASIK) and in patients with corneal dystrophies.

CT and MRI: These imaging techniques most often are used for evaluation of ocular trauma, particularly if an intraocular foreign body is suspected, and in the evaluation of orbital tumors, optic neuritis, and optic nerve tumors. MRI should not be done when there is suspicion of a metallic intraocular foreign body.

Electronystagmography: See Approach to the Patient With Ear Problems: Testing.

Last full review/revision April 2009 by Kathryn Colby, MD, PhD

Content last modified April 2009