· Plate 2.IA
Paton's lines. The lines appear as several concentric reflexes seen on the temporal side of the disc and extending considerably above and below it
· Plate 2.IB
Macular star. This sign denotes longstanding increased intracranial pressure from any cause. (Courtesy of Lee Jampol.)
· Plate 2.IC
Roth's spots. The hemorrhage is flame-shaped owing to its location in the nerve fiber layer, and it has a small white center of malignant of inflammatory cells. (Courtesy of Lee Jampol.)
· Plate 2.ID
Drusen. These excrescences can be seen as isolated refractile bodies in the substance of the disc.
This folding, in turn, causes a variation of the reflection from the internal limiting membrane, which is seen as Paton's lines. As the edema increases, this area becomes edematous and Paton's lines are no longer seen. Any cause of edema can produce Paton's lines, so their presence signifies only edema. They are not seen with such entities as drusen of the nerve head. The appearance of horizontal lines in the macula, on the other hand, signifies tumors of the muscle cone, thyroid disease, or brawny scleritis.
Edema may also spread from the disc along the arcuate fibers, making them more prominent. This appearance is not a clear-cut sign of edema; it may be seen also in cases of mild myelination of the fibers, which is difficult to differentiate from edema.
Spontaneous Venous Pulse
Many people do not have a spontaneous venous pulse at times, an absence that is frequently normal. It has been shown experimentally, however, that when the spinal fluid pressure reaches 200 mm of spinal fluid or water, the venous pulse disappears. It has been my experience that this is a reliable sign. Other investigators, such as Williamson-Noble, Hayreh, and Levin, have evaluated this concept and found it to be not only experimentally but clinically valid. The most recent clinical review of the subject was by Levin, who reviewed 33 patients with increased intracranial pressure. Van Uitert and Eisenstadt in commenting on Levin's experience disagree that the presence of a venous pulse rules out significantly increased intracranial pressure. In their comments they cite four cases of their own in which there was a spontaneous venous pulse at the same lime as they measured a significantly increased intracranial pressure. All previous reports of such an occurrence have been anecdotal and not supported by simultaneous fundus observation and spinal fluid pressure measurements. No test in medicine is perfect or without exceptions; however, given the surrounding clinical facts, the presence of venous pulse is one more piece of evidence to support the clinical diagnosis of no significantly increased intracranial pressure above 200 mm of spinal fluid. It is a clinical sign that has been valuable to me over the years and I will continue to use it in my evaluation of a swollen disc.
Although some observers consider a light touch to bring out the pulse valid, I do not think it advisable since it might introduce a significant error. Since the lightness of the touch is an unknown quantity and since intraocular pressure is measured in millimeters of mercury and not of water, the touch introduces an error of 13.5 to 1 for each millimeter of digital increase in ocular pressure. A collapsing of the vein, even if incomplete, is the sign to be observed (rather than a moving of the vessel caused by adjacent arterial pulsations). Collapsing of the vein is best seen deep in the disc or as the vein crosses the disc margin.
Deflection of Vessels
The location of vessels coming off the disc into the vitreous and then back to the level of the retina is not an unusual anomaly. It does not represent papilledema because the disc can be seen at a different level from that of the elevated vessels. The presence of vessels elevated by a swollen disc, however, suggests papilledema,
Hemorrhages and Exudates
The presence or absence of hethorrhages does not indicate either the cause or the severity of the edema, If the hemorrhages are caused by increased intracranial pressure, their quantity does not change the gravity of the condition, A small number of hemorrhages should not provide a sense of security.
Certain types or locations of hemorrhages and exudates, however, may be of diagnositic help. Disc edema associated with hemorrhages and exudates that are not only located at the posterior pole but also found all the way out to the equator suggest hypertension rather than papilledema. Exudate in the macular, such as a macular star, has no etiologic significance but denotes chronicity (Plate 2.IB). If hemorrhage is an overwhelming feature and the veins are engorged, central retinal vein obstruction is more likely. Hemorrhage located in the subhyaloid area, particularly over the disc or macula, suggests a subarachnoid hemorrhage such as results from a ruptured cerebral aneurysm (fig. 2.2).
Hemorrhages with white centers are called Roth's spots (Plate 2.IC). They suggest septic embolization, leukemia, lupus erythematosus, or pernicious anemia.
The rule is that disc edema with a loss of vision signifies optic neuritis and that papilledema with normal vision signifies increased intracranial pressure, but this rule does not always hold. Occasionally, optic neuritis occurs with good visual acuity. One of the signs of optic neuritis is the afferent pupillary defect (Marcus Gunn pupillary escape phenomenon), which indicates damage to the conduction system. Axial optic neuritis with a central scotoma and full peripheral field is the common defect, but field defects with good visual acuity can also occur.
Preretinal hemorrhage. The hemorrhage is preretinal, accounting for the disappearance of the superficial retinal vessels as they approach it.
Loss of acuity can occur with papilledema or disc edema from any cause when hemorrhages occur in the macula, as in hypertension, or in the subhyaloid area, with subarachnoid hemorrhages. Longstanding Increased intracranial pressure may cause clecompensation of the optic nerve, with resulting loss of acuity. This decompensation is one complication of prolonged pseudotumor cerebri and one of the principal reasons for surgical intervention when medical therapy fails.
Cells in the Vitreous Humor
In cases of papillitis or of retrobulbar optic neuritis in close proximity to the globe, cells can occasionally be seen in front of the disc. This phenomenon is detected only with the fundus contact lens and is rarely seen even when expected. Cells can appear in the vitreous humor as a result of other inflammatory conditions, but they are not as discrete or as localized as in papillitis or retrobulbar optic neuritis.
Height of the Disc Edema
The referring physician frequently requests information about the height of the disc edema. Unfortunately, the information causes more problems than it solves, because of the misplaced emphasis that some people put, for example, on 1 diopter of elevation as opposed to 5 diopters, as if the urgency regarding hospitalization and diagnostic tests varied with the height of the edema. Once the diagnosis of papilledema is made, prompt evaluation is mandatory, because of the increased intracranial pressure.
When measuring the degree of disc edema, the observer measures from the highest part of the edematous disc down to the normal nonedematous retina. The differ-ence in dioptic power is read on the oph-thalmoscope. If one is to record disc edema in millimeters of elevation, 2 diopters of disc elevation denote 1 mm of elevation in the phakic person, and 3 diopters of disc elevation denote 1 mm of elevation in an aphakic person (Fig. 2.3).
Figure 2.3 Advanced papilledema with multiple hemorrhages, filling in of the optic cup, and total blurring of disc structures.
Optociliary Shunt Vessels
Optociliary shunt vessels in association with poor vision or blindness and pale disc edema are highly suggestive of the diagnosis of anterior optic nerve sheath meningioma. They have also been reported in association with optic disc drusen, central retinal vein obstruction, arachnoid cysts, gliomas, and coloboma of the optic nerve.
The reason for the development of venous shunt vessels may be increased pressure in the optic nerve sheath. The relationship of pressure in the sheath to disc edema was shown by Hayreh in his exper-imental work on monkeys. When he incised one optic nerve sheath in monkeys with increased intracranial pressure, the disc edema resolved only on that side. The other side maintained the papilledema when the intracranial pressure was maintained at preoperative levels. A clinical report on two patients by Perlmutter et al. seems to support this finding. These two patients had pseudotumor cerebri and developed optociliary shunt vessels. In one of the patients, one optic nerve was decompressed; within 3 days, the disc edema disappeared, and the shunt vessels were markedly reduced. This is in keeping with the results in the monkey experiments by Hayreh (Fig. 2.4).
Figure 2.4 Shunt vessels of the optic disc.