Multiple diagnostic studies may be performed. Educate the patient about purpose, expectations, and any possible side effects related to the examinations prior to testing. Be aware of contraindications, complications, and trends in results (these provide information about disease progression and treatment response).
- Direct Ophthalmoscopy: the use of a handheld instrument with various plus and minus lenses that can be rotated into place, enabling the examiner to focus on different structures of the eye. The examiner should sketch the fundus and document and abnormalities.
- Examine the fundus: vasculature comes into focus first. The veins are larger in diameter than the arteries. Focus on a large vessel and follow it towards the midline of the body, and it should lead to the optic nerve.
- The optic disc is the central region of the eye where axons of the retinal ganglion cells pass. Document the disc margins as sharp or blurred. Silvery or coppery appearance suggests arteriolosclerosis.
- The center of the optic disc has a depression known as the cup, normally a third of the disc’s diameter. Note its physiologic size.
- Observe the periphery of the retina by having the patient shift their gaze.
- The macula, the area most sensitive to light, is examined last. It is responsible for central vision.
- The retina of a young person often has a glistening effect, sometimes referred to as a cellphone reflex.
- Lesions, if any, are abnormal and should be noted. Look for any intraretinal hemorrhages (red smudges, or flame-shaped if hypertensive).
- Lipids with a yellowish appearance may be present in patients with hypercholesterolemia or diabetes.
- Soft exudates with a white, fuzzy appearance (i.e. “cotton -wool spots”) should be noted.
- Microaneurysms should be noted. They appear as little red dots, and nevi.
- Drusen (small, hyaline, globular deposits) appear as yellowish areas with indistinct edges (small ones have distinct edges). They are commonly found in macular degeneration.
Ophthalmoscopy
The examiner uses the same hand and eye side as the side being examined i.e. right hand and eye to examine the right eye of the patient, and vice versa. Encourage stable breathing, and have the patient stare at a target and keep both eyes open and steady.
- Indirect Ophthalmoscopy: an instrument used to see larger areas of the retina, although in an unmagnified state. It produces a bright, intense light. The light source is affixed with a pair of binocular lenses mounted on the examiner’s head. The ophthalmoscope is used with a handheld, 20-diopter lens.
- Slit-Lamp Examination: a table-mounted binocular microscope is used to examine the eye with a magnification of 10 to 40 times. Illumination can be varied for different parts of the eye, e.g. the anterior chamber can be examined for signs of inflammation, a different angle can evaluate cataracts, and a combination with a handheld contact lens allows for evaluation of the angle of the anterior chamber and ocular fundus.
- Tonometry: a common procedure for the measurement of IOP, which is normally below 21 mmHg. The device used is an accurately calibrated applanation tonometer, which measures how much pressure is required to flatten the cornea. This is used to screen for and monitor IOP in glaucoma.
- Nursing Intervention: provide patient education prior to tonometry to help avoid possible errors in IOP measurement. Caution against squeezing the eyelids, holding their breath, or performing a Valsalva maneuver, as these may result in erroneously high IOP measurement.
- Color Vision Testing: color differentiation impacts ADL dramatically. Cones provide color vision (most concentrated in the macula). Basic tests such as asking the patient if an object looks redder in one eye than the other, can provide insight. Color vision deficits can be inherited (x-linked red-green color deficiency) or acquired (digitalis, cataracts).
- The most common color vision test uses Ishihara Polychromatic Plates. A booklet contains plates with dots of primary colors in simple patterns integrated into a background of secondary colors. The patient is then tasked to determine the hidden pattern or figure.
- Central vision conditions (e.g. macular degeneration) results in more difficult color identification compared to peripheral vision conditions (e.g. glaucoma)
- Amsler Grid: often used for macular problems, this consists of a geometric grid of identical squares with a central fixation point. The patient views the grid while wearing normal reading glasses. Each eye is tested separately. The patient is instructed to stare at the central fixation spot on the grid and report and distortion in the squares of the grid itself. For patients with macular problems, some squares may look faded, or some lines may appear wavy. Patients with age-related macular degeneration (AMD) can take home Amsler grids, and are encouraged to check the grids frequently to monitor macular function for early detection of changes requiring immediate attention.
- Ultrasonography: lesions in the globe or orbit may not be directly visible, or may be hidden by opaque media such as cataracts or hemorrhage. Brightness scan (B-scan) ultrasonography (USG) can identify pathologies such as orbital tumors, retinal detachment, and vitreous hemorrhage. Amplitude scan (A-scan) USG can measure the axial length for implants prior to cataract surgery.
- Optical Coherence Tomography: tomography involving low-coherence interferometry, where light is used to evaluate retinal and macular diseases as well as anterior segment conditions. This method is noninvasive and involves no physical contact with the eye.
- Fundus Photography: used to detect and document retinal lesions. The pupils are widely dilated before the procedure. Stereoscopic viewing of the photographs can show elevations such as macular edema.
- Laser Scanning: various techniques use laser light in evaluating eye disorders. Confocal laser scanning ophthalmoscopy provide a three-dimensional image of the optic nerve topography, and may be used along with fundus photography to provide comparative data for suspected optic nerve disease such as glaucoma and papilledema. Laser scanning polarimetry measures nerve fiber layer thickness and is an important indicator of glaucoma progression.
- Angiography: visualization and imaging of the retinal vessels.
- Fluorescein angiography: used to evaluate clinically significant macular edema, document macular capillary nonperfusion, and identify retinal and choroidal neovascularization in AMD. The dye is injected often through the antecubital vein. Dye should appear in the retinal vessels within 10 to 15 seconds. Black and white photographs of the retinal vasculature are then taken over a 10-minute period.
- Indocyanine green (IV) angiography: used to evaluate abnormalities in the choroidal vasculature, which are often seen in macular degeneration. Digital video angiography is used to capture multiple images.
- Perimetry Testing: evaluation of the field of vision. This helps identify which parts of the patient’s central and peripheral visual fields have useful vision. These are most helpful in detecting central scotomas (blind areas of vision) in macular degeneration, the peripheral field defects in glaucoma, and retinitis pigmentosa (night blindness). This is an especially useful monitoring tool for glaucoma progression.