15 Aplicacion en Neuro Oftalmologia

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CHAPTER 15

APPLICATION OF CONFOCAL LASER TOMOGRAPHY

IN NEURO-OPHTHALMOLOGY

Dr. Roberto Ebner

15.1 Introduction to confocal tomography (CLT) in neuro-ophthalmology

15.1.1 Acquisition and treatment of images

CLT enables the study of those diseases manifested at the level of the optic disc and

its surroundings. Although the image acquisition process is consistent with the general

rules for CLT (see chapter 2), some entities may require for their study wide capture an-

gles (15 or 20 degrees instead of 10 degrees used routinely), in order to cover all the

manifestations of the process in the same image. This is the case in edematous disc proc-

esses, where the disc diameter is larger than under normal conditions (figure 7.6).

15.1.2 Contour lineIn edematous optic disc processes, the scleral spur is difficult or impossible to iden-

tify, therefore, the contour line cannot be drawn as described according to the technique

(for example, in glaucomatous cases). The area to be studied should then be enclosed by

drawing a circle (obtained from the pertinent submenu). In the specific case of optic disc

edemas, the circle should be located at the level of Pattons line or beyond it (figure 15.1).

15.1.3 Selection of the area to be measured

The measurements (linear, area or volume parameters) are performed within the de-

fined contour line. There structure enclosed by the contour line can be measured in a

global or partial manner. The complete interior of the contour line (360 degrees) may be

of interest, or a selected sector may be indicated (in the Measure submenu) in order to

perform a partial measurement (figure 15.2).

15.2 Clinical cases and CLT in neuro-ophthalmology

15.2.1 Optic disc elevations

Edema: Optic disc edema produced by the hypertension of the cerebrospinal fluid,

either in the case of idiopathic intracranial hypertension, also known as pseudotumor

cerebri, or in the case of hypertension due to an occupying mass, yield CLT images with

a characteristic "volcanic" appearance (not chronic or atrophic chronic), when the edema

is well developed [1-3]. The central portion of the image obtained, the volcano crater,


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corresponds to the remaining disc cup. Its base (the base of the volcanic cone) has an area

much greater than the area of a normal disc. The value of the parameter volume abovesurface, provides the volume (in mm

3) of all of the structures elevated above the retinal

surface, thus providing the measurement of the volume of the edema for each case and

according to the evolution stage (figure 15.3).

Different three-dimensional images may be acquired at different time in a longitudi-

nal study in such a way, that the behavior of the causal process and its effect on the optic

nerve can be monitored. In the case of pseudotumor cerebri, the effectiveness of the

treatment (with the use of osmotic diuretics, steroids, etc.) may be evaluated by means of

CLT by comparing the volume of the papilledema at variable time intervals. If worsening

is observed, then treatment may be modified (medication dosage increase or indication of

decompressive surgery of the optic nerve sheath). Otherwise, a decrease in the volume of

the edema will be indicative of treatment effectiveness. Changes in volume of the papil-

ledema can be detected early enough so that clinical changes may not yet have appeared(worsening of visual acuity, visual field defects or color vision disorders). This monitor-

ing is also valid in the case of tumors in the CNS that cannot be subjected to surgery and

which are treated with radiotherapy and/or chemotherapy.

For longitudinal studies to evaluate the changes in the volume of a disc, we may just

stick to the value of said parameter (volume above surface) for each examination, or we

may use the comparison submenu (topographic difference image) in order to display the

observed height changes as graphs or numbers. The difference images presented show the

locations where a volume decrease is detected in red color, while the locations where

Fig. 15.1: The image at the top left-hand shows how the contour line should be drawn. It

should follow the scleral spur. The top right-hand image shows the complete drawing.

The planes enabling one to achieve a better image of the neuroretinal rim margin can be

chosen from the series of 32 images shown between the previously described images. The

images at the bottom are from a case with optic disc edema, where the contour line

should be drawn outside the over-elevated area.


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there is a volume increase appear in green color. If differences in volume only involve

fibers, the measure submenu numerically (in mm3) provides the volume differences

between the examinations (as well as the time elapsed between examinations). Values

indicating volume increase are positive and those indicating volume decrease are negative

(figure 15.4). When the disc edema has led to optic disc atrophy, the optic disc is flat. In

some cases, it is accompanied by radiated folds (which take a long time to disappear).

Pseudoedema of the optic disc (drusen): The presence of hyaline bodies (drusen)

buried into the optic disc, lead to an over-elevation of the optic nerve head. Classically,

the presence of these hyaline bodies has constituted one of the differential diagnoses be-

tween optic disc edema and optic disc pseudoedema. In computerized tomography and in

Fig. 15.2: Selection of a segment of the optic disc image (inferior nasal and temporal

octants) in order to measure volumes. Within this segment there is a tumorous formation.

Fig. 15.3


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ultrasonography, there are signs that are characteristic of this entity (hyaline bodies) at

the level of the optic head nerve, revealed as calcifications in the computerized tomogra-

phy [4] or evidencing the presence of Skalkas sign in echography [5, 6]. Just like the

papilledema had a volcanic appearance in CLT, the drusen has the appearance of a kid-

ney, with the characteristic orientation of its pelvis (renal) always towards the macular

sector. It should be considered that the classical descriptions of optic nerve head drusen

[7] indicate the absence of a physiological cup in these discs. Miller stated that the drusen

mainly produce a protrusion in the nasal sector of the optic disc [8]. The topography (in

CLT) shows that the slit revealed in the temporal sector (area corresponding to the pap-

illo-macular bundle entrance) completes the shape, here suggested, of a renal pelvis

which is a modified variant of the central cup (figure 15.5).

The differential diagnosis between edema and pseudoedema of the optic disc with

CLT is based on the topographic aspect that each entity has. The volcano image for the

Fig. 15.4

Fig. 15.5


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Unlike intraocular tumors (like cavernous angiomas) [12], optic nerve sheath me-

ningiomas, surround the nerve and strangulate it [13, 14]. The compression thus origi-

Fig. 15.7: Top: nuclear mushroom appearance of papillitis. A profile performed diago-

nally (menu interactive measurements, option distance) reveals the type of optic disc

elevation and the absence of a central cup. The macular area of the same patient (bottom)

also shows an elevation (see profile), in association with radiated folds.

Fig. 15.8: Disc elevations due to the presence of an orbital tumor. The image on the right

corresponds to an optic nerve sheath meningioma with the vascular anomalies at the level

of the optic disc. The image on the left shows the optic nerve head in a case of orbital

cavernous angioma, with circular folds beneath the elevated disc.


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nated may cause a disc elevation (before reaching the atrophic stage) and a vascular phe-

nomenon known as Hoyt-Spencers Sign may be observed [15].

15.2.2 Vascular processes: anterior ischemic optic neuropathy (AION)In the non arteritic form of AION, a regional acute infarction (rarely global) of the

optic disc occurs [16, 18]. During the acute picture, the CLT identifies the sectors under-

going the ischemic process (which affects the posterior ciliary artery system) and it re-

veals the elevated areas of the neuroretinal rim. Sometimes, the swollen areas correspond

with the resulting perimetric picture (altitudinal defect), although this is not always the

case. As for the fellow eye, the CLT allows one to obtain the cup/disc ratio objectively,

thus identifying the so-called risk discs [19, 22] (figure 15.9).

15.2.3 Optic disc atrophies

- Traumatic optic neuropathy (TON)

- Multiple sclerosis (MS)

- Lebers hereditary optic neuropathy (LHON)- Toxic optic neuropathy (TXON)

- Post-edema optic disc atrophy

In cases of post-traumatic optic atrophies (closed orbitofacial trauma or blunt

trauma), as well as in those caused by demyelivating neuropathies (DN) and in the toxic

ones (related to alcohol and tobacco consumption) or those studied in LHON case, neuro-

retinal rim defects at the level of the papillo-macular bundle develop (figure 15.10). This

finding is clinically related to the presence of central scotomas in the visual field of the

affected eyes.

Fig. 15.9: Reflectivity image (on the right) of an AION after a few hours of evolution.

The image on the left shows the optic disc of the right eye of the same patient which was

obtained in order to measure volumes (green: volume above surface; blue: volume above

reference; red: volume below reference) and which enables to obtain the cup/disc ratio

(c/d). It is outstanding how low the c/d ratio is (see text: risk disc).


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In no case the diseases listed resemble the atrophies observed in glaucoma or low

tension glaucoma since neither cup depth nor volume increase, nor does the cup shapemeasure vary in a positive sense (see chapter 8, sections 8.1 and 8.2).

Post-edema atrophy is not different from the previously described ones in its tomo-

topographic characteristics, but unlike the above mentioned atrophies it may be accom-

panied by retinal folds (right from the edematous stage) [23], generally radiated from the

disc and which take long to disappear.

15.2.4 Optic disc malformations with neuro-ophthalmologic manifestations

Tilted disc (situs inversus of the optic disc): The most frequent disc malformation

was found in discs implanted in an oblique position or tilted discs. They have a charac-

teristic oval shape and the amount of tilt is variable.

As CLT displays 32 consecutive (sufficiently thick) sections, it is easy to localize

the difference in height where the different portions of the neuroretinal rim are located inthese optic discs, thus enabling to determine the scleral spur limits accurately. Neverthe-

less, when a malformation is very marked, one of the rims lips may be hidden so that the

scleral spur is impossible to determine (with the contour line).

Morning Glory Syndrome: Another frequent malformation is the presence of a

large and deep disc in the shape of a truncated cone, known as Morning Glory. In two

out of the three examined cases, the contralateral eye was pathological (retinal detach-

ment in one case, increasing temporal myopia in the other, which in the third case was

associated with an optic disc pit) [24-25].

Fig. 15.10: Top left: Papillomacular bundle defect in a case of toxic neuropathy. Top

right: Atrophic disc with disparition of the neuroretinal rim temporally in a case of Le-

bers lenditary optic neuropathy. Bottom: Atrophic disc in MS. Note the collapse of neu-

roretinal rim at the papillomacular entrance.


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A patient came for consultation due to a brief-lasting amaurosis on the side of the

malformation. Examination with the HRT in this particular case was carried out in three

different eye positions (primary eye position [PPM], abduction [ABD] and aduction

[ADD]) since the patient reported darkening of vision when his eye was in abduction. A

striking change of volume in the disc, depending on the eye position, was observed. The

discs behavior (in its variations for each position) was similar to the behavior of a

plunger, not in its ability to produce a vacuum, but regarding the changes produced in the

soft portion of this element when (attached to a surface) it suffers the tension originated

in the hard portion (the handle) when it is shifted from side to side (figure 15.11). The

structural modifications of these malformed discs have already been reported by Wise

and Pollack [26-27].

These optic disc variations (symptomatic or not) were not observed in two other

cases with the same malformation.Megalopapilla: In a case of esotropia detected from birth in the right eye (RE) of a

four-year-old girl whose visual acuity was luminous perception at the temporal sector,

though her neurologic and pediatric examinations (including neuroimaging) were normal,

the CLT showed the presence of a flat atrophic disc with only remnant fibers only at the

nasal sector (accounting for the temporal light vision of the patient) and of a surface three

times its normal size (see figure 7.6), the characteristic signs of a megalopapilla [28-29]

(figure 15.12).

Fig. 15.11: Top row: topographical and reflectivity images of the left eye in a patient

with Morning Glory syndrome obtained in primary eye position. Middle row, from left to

right: images obtained in adduction, primary position and abduction of the left eye

showing the volume variations according to the eye position. Bottom row: pseudo-three-

dimensional images showing the volumetric changes of the cup according to the eye po-

sition; from left to right: adduction, primary position and abduction of the left eye.


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15.2.5 Chiasmatic syndrome

It was observed that in patients with tumors at the sellar region, the topographic im-

ages obtained when using the menu stereometric parameters, sub-menu measure (in

360 degrees), showed a characteristic green region (volume above surface) and part of the

blue region (volume above reference - volume below surface) had more volume in the

nasal sectors of each eye.The central cup had a strange truncated shape at the level of the nasal portion (figure

15.13). This topographic condition was repeated in cases of active sellar tumors (com-

pressing and shifting the chiasm), and the topographic condition worsened in a postop-

erative case, probably due to the manipulation of the area. Conversely, in operated cases

where the chiasm is not shifted (but where there are visual/perimetric sequelae), disc

atrophies without the above mentioned characteristics of a nasal optic disc protrusion are

found.

In one case the patient was a child on whom perimetry could not be performed due

to his low vision. Upon ophthalmoscopy he seemed to have a simple optic disc atrophy.

The CLT evidenced the disc condition described above (increase of the neuroretinal rim

at the nasal sector and a nasal deformation of the central cup). Magnetic resonance re-

vealed a craniopharyngioma.In another chiasmatic syndrome case due to the growth of an inactive adenoma, the

topographic images revealed the same pattern, whereas clinically one of the eyes showed

a temporal visual field defect and the other eye had light perception.

The topographic features of these patients are highly suggestive of an ongoing sellar

pathology. In patients with visual field damage, with or without disc atrophy upon CLT

but with a previous surgery for the process causing the chiasmatic syndrome, the signs

described above were not present.

Fig. 15.12: Note the value of disk area in this case of megalopapilla.


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We do not know the meaning of this finding, since the fibers coming into the optic

nerve, which are responsible for conveying information from the temporal hemifield (na-

sal fibers), are not exclusively bound to the nasal disc margin.

15.2.6 Homonymous Hemianopsias (HH)

In patients with either congenital HH or HH in its late evolution stage (enough to

present trans-synaptic atrophy), the neuroretinal rim had a different behavior in the optic

nerve head of each eye. This had already been observed by other authors through oph-

thalmoscopy [30-31].

The eye homolateral to the hemianopsia (contralateral to the lesion), with CLT

shows a defect in the area of the papillo-macular bundle caused by a reduction in the

volume of the incoming axons, with a resulting oval-shaped cup. In the eye contralateral

to the hemianopsia (eye on the side of the lesion) the axonal reduction (expressed by the

reduction in the volumes of the neuroretinal rim), is detected above and beneath the en-

trance area of the papillo-macular bundle and it results in a triangular appearance of the

cup (figures. 15.14, 15.15 and 15.16).The cup patterns - oval in the eye on the side of the hemianopsia and triangular in

the eye on the side of the lesion - make up the topographic pattern of congenital HH or of

those caused by old lesions (capable of producing trans-synaptic atrophy).

Fig. 15.13: CLT of the right eye (top) and left eye (bottom) of a patient with a sellar

mass. Note the volume distribution (green) of VAS with a vertical clear cut limit of nasal

crowding with an accompanying shift of the central cup temporally (see text).


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Fig. 15.14: Confocal tomography of the right eye in a patient with left homonymous

hemianopsia and optic disc manifestations of trans-synaptic atrophy. The topographic

(A), reflectivity (B) and volumetric identification (D) images, as well as the pseudo-3D

image (C) show the triangular shape of the cup caused by a reduction in the volumes of

the neuroretinal rim in its superior and inferior temporal portions.

Fig. 15.15: Confocal tomography of the left eye of the same patient shown in figure

15.14. The topographic (A), reflectivity (B) and volumetric identification (D) images, as

well as the pseudo-3D image (C) show the oval shape (horizontal major axis) of the cup

caused by a reduction in the volumes of the neuroretinal rim in its central temporal por-

tion.


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Bibliography

1. Jackson JH: On the rutine of the ophthalmoscopein cases of cerebral disease. Med

Times Gaz 1871;1:627-629.

2. Cogan DG, Kuwabara T: Papilledema Exp Eye Res 1977; 25(suppl):419-433.

3. Hoyt WF, Beetson D: The Ocular fundus in Neurologic Disease. St. Louis, CV

Mosby Co, 1966.

4. Frisen L, Scholdstrom G, Suedsen P: Drusen in the optic nerve head: verification

by computarized tomograph. Arch Opthalmol 1978;96:1611-1614.

5. Skalka H: Ultrasonography of the optic nerve. In: Neuro-ophtalmology Update, JL

Smith de., Masson, New York, 1977, pp 119-130.

6. Byrne SF: Evaluation of the optic nerve with standardized echography. In: Neuro-

ophtalmology Now, JL Smith de., Field Rich and Assoc. Inc., New York, 1986, pp

45-66.

7. Erkkila H: The central vascula pattern of the eyeground in children with drusen of

the optic disc. Graefes Arch Clin Exp Ophtalmol 1976;99:1-10.

8. Miller NR: Pseudo papilledema - optic disc elevation not caused by swelling, with

and without visible optic disc drusen. In Miller NR, Walsh and Hoyts Clinical

Neuro-ophthalmology, 4th ed., Volume 1, Baltimore, Willams & Wilkins, 1982, pp

355-373.

9. Maitland CG, Miller NR: Neuroretinitis. Arch Ophthalmol 1984;102:1145-50.

10. Parmley VC, Schiffman JS, Maitland CG et al: Does Neuroretinitis rule out mul-

tiple sclerosis? Arch Neurol 1987;44:1045-48.

11. Miller NR: Compresive optic neuropathies with optic disc swelling. In: Miller NR,

Walch and Hoyts Clinical Neuro ophthalmology , 4th ed., Volume 1, Baltimore,

Willams & Wilkins, 1982, pp 249-253.

12. Smith EG: Unilateral papilledema: Its significance and pathologic physiology. Arch

Ophthalmol 1939;21:856-873.

13. Spencer WH: Primary neoplasms of the optic nerve and its sheath: Clinical features

and current concepts of pathogenetic mechanisms. Trans Am Ophthalmol Soc 1972;

70:490-528.14. Wright JE: Primary optic nerve meningiomas: Clinical presentation and manage-

ment. Trans Am Acad Ophthalmol Otolaryngol 1977;83:617-625.

15. Hollenhorst RW jr, Hollenjorst RW sr, MacCarty CS: Visual prognosis of the

optic nerve sheath meningiomas producing shunt vessels of the optic disc: The

Hyot-Spencer syndrome. Trans Am Ophthalmol Soc 1977;75:141.

16. Hayreh SS: Anterior ischemic optic neuropathy: 1 Therminology and pathogenesis.

Br J Ophthalmol 1974;58:955-963.


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199

17. Hayreh SS: Anterior ischemic optic neuropathy. Berlin, Springer-Verlag, 1975.

18. Hayreh SS: Anterior ischemic optic neuropathy. Arch Neurol 1981;38:675-678.

19 Hyot WF: Rocky Mountain Neuro-ophthalmology Society Meeting, 1982.

20. Beck RW, Savino PJ, Repka MX, et al: Optic disc structure in anterior ischemic

optic neuropathy. Ophthalmology 1984;91:1334-1337.

21. Beck RW, Servais GE, Hayreh SS: Anterior ischemic optic neuropathy. IX. Cup-

to-disc ratio and its role in pathogenesis. Ophthalmology 1987;94:1503-1508.

22. Burde RM: Optic disk risk factors for nonarteritic anterior ischemic optic neuropa-

thy. Am J Ophthalmol 1993;116:759-764.

23. Dailey RA, Mills RP, Stimac GK, Shults WT, Kalina RE: The natural history andCT appearance of acquired hyperopia with choroidal folds. Ophthalmology

1986;93:1336-1342.

24. Kindler P: Morning glory Syndrome: Unusual congenital optic disk anomaly. Am J

Ophthalmol 1970;69:376-384.

25. Brodsky MC: Congenital optic disk anomalies. Surv Ophthalmol 1994;39:89-112.

26. Wise JB, Maclesa AL, Gass DM: Ccontractile peripapillary staphyloma. Arch

Ophthalmol 1966;75:626-630.

27. Pollock S: The morning glory disc anomaly: Contractile movement, classification

and embryogenesis. Doc Ophthalmol 1987;65:439-460.

28. Franceschetti A, Bock RH: Megalopapilla, a new congenital anomaly. Am J Oph-

thalmol 1950;33:227-235.

29. Malbran JL, Roveda JM: Megalopapila. Arch Oftal B Aires 1951;26:331-335.

30. Hoyt WF, Rios-Montenegro EN, Behrens MM, Eckelhoff RJ: Homonymus

hemiopic hypoplasia. Fundoscopic features in standard and red-free illumination in

three patients with congenital hemiplegia. Br J Ophthalmol 1972;56:537-545.

31. Novakovic P, Taylor DSI, Hoyt WF: Localising patterns of optic nerve hypopla-

sia-retina to occipital lobe. Br J Ophthalmol 1988;72:176-182.


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