336 Chapter 13: Posterior Segment Examination
Normal variations of the ora teeth include forked teeth, bridging teeth, giant teeth, and ring-shaped teeth. An enclosed ora bay must be distinguished from a retinal hole. A deep ora bay is sometimes seen nasally at the horizontal meridian. The temporal periphery is the most common site of lattice degeneration and pars plana cysts. The nasal periphery is the most common site of prominent ora teeth and meridional folds, particularly in the superonasal quadrant.
A pigmented zone (demonstrable by transillumination of the globe) is located along the ora serrata. This area of retinochoroidal adhesion is 3-4 mm wide in the temporal periphery and 1 mm wide in the nasal periphery and represents the normal fusion of the retina and the retinal pigment epithelium.
Several changes of the fundus periphery can be found (Figure 13.24). The most common finding of the peripheral fundus is one or more pearls at the ora serrata. These ora pearls are drusen that look like shiny white spherules near the ora serrata. They have no clinical importance despite their remarkable appearance.
Cystoid degeneration appears as an area of granular tissue. This belt of agglomerated cysts occurs at the extreme retinal border, especially temporally. Cystoid degeneration can coalesce to form senile retinoschisis. Pars plana cysts are transparent, elevated cysts measuring 1 or 2 disc diameters. Pars plana cysts are usually multiple, bilateral, and limited to the posterior half of the temporal pars plana.
White with pressure is a term used to describe a blanched color of a flat area of the peripheral retina during scleral depression. This condition is usually caused by preretinal vitreous opacification. White without pressure is a related phenomenon that is visible without scleral indentation.
Chorioretinal degeneration is a stippled pigmentary change that occurs adjacent to the ora serrata. Paving-stone degeneration, also known as peripheral chorioretinal degeneration and cobblestone degeneration, is a cluster of thinned, depigmented spots in the periphery. Because there is loss of the outer retina, the retinal pigment epithelium, and the choriocapillaris, a patch of white sclera is visible, with perhaps a few choroidal vessels crossing it. Clumps of pigment may border the margin of these circumscribed areas. Coalescent patches form an elongated zone with a scalloped margin parallel to the ora serrata. Lattice degeneration is an oblong, punched-out spot that may have overlying white, hyalinized blood vessels.
Light reflexes off the internal limiting membrane are more apparent in the young, and with reduced illumination a glimmering halo is seen encircling the macula.
The Normal Fundus and Its Common Variations |
337 |
B
Figure 13.24 Normal variations of the fundus equator and periphery. (A) Ora pearls. (B) Chorioretinal degeneration.
(C) Reticular pigmentary degeneration. (D) Equatorial drusen.
(E) Paving-stone degeneration. (F) White with/without pressure.
(G) Pars plana cysts. (Reproduced from Rutnin U, Schepens CL: Fundus appearance in normal eyes. Am J Ophthalmol 1967; 64:821 -852,1040-1078. Published with permission from The American Journal of Ophthalmology. Copyright by the Ophthalmic Publishing Company.)
Remnants or the fetal hyaloid artery include an epipapillary mem - brane or veil. The hyaloid canal passes from the optic nerve head to the lens, and a residual point of attachment can be seen as a dot on the posterior capsule.
Neither the anterior nor the posterior limit of the vitreous base can be seen in an eve with a normal vitreous humor. With a posterior vitreous detachment, a white line is sometimes seen on the retina just posterior to the ora serrata and is the posterior limit of the vitreous base. T h e anterior limit of the vitreous base is infrequentlv visible as a white line in the middle of the pars plana. The boundary of the vitreous base varies among' different individuals but normally extends about 2 mm either side or the ora serrata.
338 Chapter 13: Posterior Segment Examination
Age-related liquefaction, beginning in the central posterior vitreous, produces optically clear cavities. Liquid vitreous entering the space posterior to the vitreous cortex produces collapse (syneresis). A posterior vitreous detachment is a separation between the posterior vitreous cortex and the internal limiting membrane and can cause floaters.
Asteroid hyalopathy consists of small white spheres made of calcium- phosphate-phospholipid crystals that do not usually impair vision.
Pitfalls and Pointers
• One of the hardest problems encountered in learning indirect ophthalmoscopy is maintaining proper alignment. The inverted image further increases the problem, because everything seems to move the wrong way. To keep a focused image during indirect ophthalmoscopy, concentrate on keeping a rigid axis, extending from yourself to a point on the patient's retina. The pupil must be the center of rotation of this axis of observation. As the view changes from one part of the retina to another, the viewing axis must pivot at the pupil. For example, a 20° shift on the retina is
only about 5 disc diameters. Being farther from the pupil, the condensing lens must move a greater distance, and the observer a very large distance. When shifting the viewing angle, the examiner's head and lens always move in the same direction as the side of the visible image toward which the examiner wishes to go.
•Other imaging problems and their causes are summarized in Table 13.9. Model eyes are available for training and practice, and a teaching mirror shows the beginner exactly what is supposed to be seen. Skill in the art and interpretation of indirect ophthalmoscopy takes daily practice with patients.
•A bright light hurts the patient. A considerate examiner avoids dazzling the patient with an unnecessarily high voltage setting. Beginning the examination at the equator and periphery can give the patient a chance to adapt to the light before the posterior pole is examined. Proper lens position is usually possible with only a small edge of the light beam, thereby shortening the duration of bright flashes to the patient. As the examiner changes position, the light should not be shining uselessly into the eye. Allow brief rest periods to let the patient recuperate.
•Often a quick look at the posterior pole is all an examiner will be able to achieve in small children. Turning down the illumination
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brightness, keeping the child in the parent's lap, and avoiding any |
Pitfalls and Pointers |
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Table 13.9 Common Problems During Indirect Ophthalmoscopy
Problem
Large portion of the image is dark or distorted
Image is too small
Central reflections obscuring the image
Irregular reflections and haziness
Dull image
Peculiar meshwork of vessels
Image suddenly lost
Inability to go from one fundus area to another
Reason
Faulty lateral or vertical lens positioning
Condensing lens too near or too far from the eye No lens tilt
Dirty lens
Light not properly centered in the pupil Looking at conjunctiva
Patient moved eye
Moving the viewing axis in the wrong direction
touching of die child's face can enable indirect ophthalmoscopy. For children who continue to move their eyes, try using only a bright, handheld flashlight, such as a Finoff transiliuminator. While sighting down the light beam that is directed at the child's dilated pupil, interpose a condensing lens to view the posterior pole.
During scleral depression, inability to see the indented area is often wrongly interpreted as insufficient pressure. As the examiner pushes harder, the patient moves the eye, making it impossible to find the retinal periphery. If the area of scleral depression cannot be seen, the examiner should realign the axis of view or the depressor.
To avoid confusion in localizing a fundus lesion, recall that a fundus lesion is located in terms of meridians of the clock. Its placement along an anteroposterior meridian is estimated in disc diameters in relation to the ora serrata, equator, and fovea.
An easy way to find the correct meridian is to position the axis of observation directly upon the lesion, so it is seen in the center of the lens. The lens is withdrawn, and the examiner looks at the eyeball to estimate the clock hour.
Anteroposterior localization is estimated in a similar way. Keeping the axis of observation fixed with the lens withdrawn, the examiner guesses what portion of the far side of the inside of the eyeball would be illuminated by the light passing through the pupil. The anteroposterior location is then confirmed by placing
340 Chapter 13: Posterior Segment Examination
the scleral depressor on the lesion and looking to see how far back the depressor is from the limbus. The ora serrata is 8 mm behind the limbus, and the equator is usually 12-14 mm from the limbus.
•Although bradycardia from the oculocardiac reflex is uncommon during routine examination, vasovagal syncope may result from application of a fundus contact lens. The contact lens should be held, but not pushed, against the eye and removed if the patient begins to feel faint.
Suggested Resources
Retinal Conditions
Age-Related Macular Degeneration [Preferred Practice Pattern]. San Francisco: American Academy of Ophthalmology; 1994.
Diabetic Retinopathy [Preferred Practice Pattern]. San Francisco: American Academy of Ophthalmology; 1993.
Hilton GF, McLean EB, Chuang EL. Retinal Detachment. Ophthalmology Monograph 1, 2nd ed. San Francisco: American Academy of Ophthalmology; 1995.
Precursors of Rhegmatogenous Retinal Detachment [Preferred Practice
Pattern]. San Francisco: American Academy of Ophthalmology;
1994.
Indirect Ophthalmoscopy
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Benson WE. Retinal Detachment: Diagnosis and Management. |
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Philadelphia: JB Lippincott Co; 1988, pp 85-111. |
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Friberg TR. Examination of the retina: Ophthalmoscopy and fundus |
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biomicroscopy. In: Albert DM, Jakobiec FA, eds. Principles and |
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Practice of Ophthalmology. Philadelphia: WB Saunders Co; 1994. |
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Potter JW, Semes LP, Cavallerano A/\, et al. Binocular Indirect |
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Ophthalmoscopy. Newton, MA: Butterworth-Heinemann; 1988. |
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Rubin ML. The optics of indirect ophthalmoscopy. Surv Ophthalmol |
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1964;9:449-464. |
Hruby and Contact Lens Biomicroscopy
Tblentino FI, Schepens CL, Freeman HM. Vitreoretinal Disorders: Diagnosis and Management. Philadelphia: WB Saunders Co; 1976, pp 45-108.
Direct Ophthalmoscopy
Heilmann K. Ophthalmoscopy: Principles, Examination Technique, Applications, Findings. Stuttgart: Ferdinand Enke; 1980, pp 22-44.
SapiraJD. The Art and Science of Bedside Diagnosis. Baltimore: Urban & Schwartzenberg; 1990, pp 173-205.
Fluorescein Angiography
BerkowJW, Orth DH, KelleyJS. Fluorescein Angiography: Technique and Interpretation. Ophthalmology Monograph 5. San Francisco: American Academy of Ophthalmology; 1991.
Clinical Protocol 13.1
Obtaining a Fundus Image in
Indirect Ophthalmoscopy
1.Ask the reclining, fully dilated patient to gaze steadily at a distant target on the ceiling. Having the patient look just above and beyond your shoulder (your right shoulder when examining the patient's right eye) will help to align your view onto the posterior pole. Patients with poor vision are asked to extend an arm and to stare at their outstretched thumb.
2.While standing above the patient, direct the headset's light by tilting your head so that it illuminates the fundus when focused through the condensing lens.
3.Holding the condensing lens in the standard manner, position it just in front of the patient's eye and center the pupil in it.
continued
4. Pull the lens slowly away from the patient's eye by flexing your wrist and by bending the fingers holding the lens (Figure 1) until you see a stereoscopic, focused image of the fundus in midair in front of the condensing lens (Figure 2). For a +20 D condensing lens, the image is seen when the lens is positioned about 5 cm in front of the patient's eye.
Figure 1 (Redrawn from:The technique of binocular indirect ophthalmoscopy, courtesy of Benjamin F. Boyd, MD, Highlights of Ophthalmology, 1966; 9:179-257.)
Figure 2
5.Accommodate on this image with both eyes, and maintain it by keeping the headset's light in the patient's pupil.
6.If light reflections from the front and back surfaces of the condensing lens are centered (Figure 3 A), tilt the lens slightly to move them apart (Figure 3B).
(Modified from:The technique of binocular indirect ophthalmoscopy, courtesy of Benjamin F. Boyd, MD, Highlights of Ophthalmology, 1966; 9:179-257.)
7.Shift the field of view by moving your head and the condensing lens along a fixed axis. Use the extended finger of the hand holding the condensing lens as a pivot to keep your viewing axis centered on the patient's pupil (Figure 4).
8.Mentally note that the image of the patient's fundus is inverted and reversed.
Figure 4 (Redrawn from:The technique of binocular indirect ophthalmoscopy, courtesy of Benjamin F. Boyd, MD, Highlights of Ophthalmology, 1966; 9:179-257.)
Performing Scleral Depression
1.While standing opposite the area to be examined, instruct the reclining patient to look toward vou. It may also help in positioning to have the patient turn his or her head away from the direction of the zone of regard.
2.Increase the voltage setting on the ophthalmoscope transformer to the highest setting that the patient can tolerate, to compensate for the reduced light entering the eye obliquely through the pupil.
3.With your dominant hand, hold the thimble-style scleral depressor by either inserting your index finger, as with a thimble, or by grasping the outside of the "thimble" between your thumb and index finger, as you would a surgical instrument (Figure 1).
Figure 1
4.Rest the tip of the scleral depressor lightly at the skin crease of the eyelid (Figure 2). Align the shaft of the instrument with your visual axis and keep the depressor nearly parallel to the surface of the patient's eye (Figure 3A).
5.Instruct the patient to move the eyes toward the tip of the scleral depressor (Figure 3B). Often it is only necessary for the patient to resume a straight-ahead, primary position rather than to gaze
excessively far in the meridian being examined.
6.Press the depressor gently. This action creates a mound in the fundus (Figure 3C).
Figure 3A Figure 3B Figure 3C
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(Redrawn from: The technique of binocular indirect ophthalmoscopy courtesy of |
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Benjamin F Boyd, MD, Highlights of Ophthalmology, 1966;9:179-257.) |
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