Ординатура / Офтальмология / Английские материалы / The Glaucomas Volume 1 Pediatric Glaucomas_Sampaolesi, Zarate_2009

See Fig. 17.28 and Table 17.16 for a comparison of megalopapillas with congenital glaucomas.

In Fig. 17.28, the ordinates show parameter values either in square millimeters or cubic millimeters, and the different optic nerve head parameters are represented in the abscissa: disc area, rim area, rim volume, cup area, cup volume, and cup shape measure. The statistical difference is highly significant as regards cup shape measure, poorly significant as regards rim area, and nonsignificant in terms of disc area, rim volume, cup area, and cup volume (Table 17.16). It should be kept in mind that the cup area has the same value in the megalopapillas as in reoperated congenital glaucomas and that the mean disc area is 3 mm2 in both groups. In congenital glaucomas, the axial length of the eye is large, thus enlarging the Elschnig ring and the disc in turn [19].

Table 17.16 Parameters between advanced glaucoma group with megalopapilla

NS not significant; * p<0.01; *** p<0.0001

Fig. 17.28 a Comparison between the advanced glaucoma group (with visual field defect in stages III and IV) with megalopapillas. Abscissas show area values in square millimeters. Ordinate: six groups represented to compare disc area, rim area, rim volume, cup area, cup volume, and cup shape mea-

sure. b Statistic shows highly significant difference in terms of disc area, rim area, and rim volume, while the difference is less significant in terms of cup area and cup volume and no significant difference as regards cup shape measurement

Figure 17.30 shows three different discs:

a.A normal disc with a very small cup;

b.A glaucomatous disc with a very big cup and a lower number of fibers because many of them have died and disappeared;

c.A megalopapilla without glaucoma. This is a disc with a very big surface compared with Fig. 17.30a, b, and a very big cup. The most remarkable thing is that the number of nerve fibers that we drew in the neuroretinal rim of the megalopapilla is the same as that drawn in the normal disc.

At the bottom of Fig. 17.30a–c there is a comparison between a normal optic disc with and a glaucomatous one (Fig. 17.30a, b). The area of the disc is the same, but the area of the cup is bigger in the glaucomatous disc, and the area of the neuroretinal rim is smaller. In the normal disc (Fig. 17.30a), the slope (the third moment of cup shape measure) is smooth, but in the glaucomatous disc (Fig. 17.30b), the slope is steeper, and in the megalopapilla disc (Fig. 17.30c) the slope is also steeper. The cup shape measure, which represents the slope of the fibers, is positive in glaucomatous discs and megalopapillas, while in normal discs it is negative.

Fig. 17.30a–c Three different discs: a a normal disc with a very small cup, b a glaucomatous disc with a very big cup and a lower number of fibers because many of them have died and disappeared. c Megalopapilla without glaucoma. This is a disc

with a very large surface compared with a and b, and a very big cup. The most remarkable thing is that the number of nerve fibers that we drew in the neuroretinal rim of the megalopapilla is the same as that drawn in the normal disc

Figure 17.31a shows the HRT of the right eye, with the following values: disc area, 3.037 mm2; cup volume, 1.011 mm3; rim volume, 0.227 mm3; cup shape measure, 0.020. The visual fields are also shown.

Figure 17.31b shows the HRT of the left eye, with the following values: disc area, 2.741; cup volume, 0.889 mm3; rim volume, 0.206 mm3; cup shape measure, 0.11. The visual fields are also shown.

The HRF of the right eye (Fig. 17.32a) shows that there is no localized perfusion defect but an increased intercapillary space and no ischemic localized zone.

In the megalopapilla case illustrated in Fig. 17.32b, there is no localized fiber layer defect at the inferior temporal area, as clearly seen both in the color and in the black and white photograph where it is signaled by two arrows, one coming from the top and the other one from the bottom. The absence of a notch in this local-

ized defect, as observed in this case, is typical of megalopapilla. However, had this been a glaucomatous localized defect with no megalopapilla, there would have been a notch. The examination with the HRF in these cases shows a clear localized nerve fiber layer defect with localized reduced perfusion, increased intercapillary space (black squares), and an ischemic localized zone (bright).

Conclusions

Megalopapillas may be confused with advanced glaucomatous optic nerve head damage and other neuropathies, but they are actually a different entity, characterized by a pseudoglaucomatous disc with normal visual field and normal daily pressure curve.

The characteristics shared with glaucoma are increased cup area, cup volume, and cup shape measure. However, disc area, rim volume, and rim area are completely different.

No significant differences were found upon comparing the megalopapilla group with the congenital

glaucoma group in all the optic nerve head parameters but one, cup shape measure, which is almost preserved in the congenital glaucoma group. The increase in the total area leads to an increase in the cup area, though with no decrease in the rim area, unlike what occurs in adult glaucoma.

The increase in the papillary border causes the fibers to enter almost vertically, which turns the cup shape measure values positive (pathological values). Megalopapilla is an entity that seems to have been ignored by the literature worldwide, and it is not even named in most well-known ophthalmology textbooks.

Congenital Anomalies of the Optic Nerve

Introduction

It often occurs that ophthalmologists or particularly pediatric ophthalmologists, have to examine newborns, mainly children with low vision due to congenital optic disc anomalies. There are three main references to consult: Orellana and Friedman [29], Apple and Rabb [30], and Brodsky [31].

In the last 10 years, central nervous system (CNS) defects of patients with congenital optic disc anomalies were studied by means of magnetic resonance. In this way, every type of malformation has been associated with malformation defects of the CNS.

Concepts for Diagnosis and Treatment

a.Unilaterality or bilaterality. When the anomalies are unilateral, the child generally presents esotropia during infancy, while bilateral anomalies appear earlier, as the loss of vision is accompanied by nystagmus.

b.In most cases, malformations of the CNS accompany congenital anomalies of the optic nerve. For this reason, magnetic resonance should be performed in all cases.

c.Color vision is usually maintained. This is useful for differential diagnosis because it is the opposite of what occurs in acquired optic neuropathies, where there is a marked dyschromatopsia.

d.Amblyopia usually accompanies these vision-re- ducing anomalies in the first years of life and during childhood. Therefore, it is important to keep this in mind, as it may be of help to the child with ocular occlusion.

CNS Malformations in Congenital

Optic Disc Anomalies

When congenital optic disc anomalies occur with small optic discs, they are accompanied by malformations of the brain hemispheres, pituitary infundibulum, septum pellucidum, and corpus callosum. Those accompanied by large optic nerves, and in morning glory syndrome, present a transsphenoidal basal encephalocele, and in cases of colobomas, they are associated with congenital colobomatous syndromes.

Classification

See Tables 17.17 and 17.18 for a classification of CNS malformations in congenital optic disc anomalies.

Table 17.17 Congenital anomalies of the optic nerve

IHypoplasia

of the optic nerve

Table 17.18 Central nervous system malformations in congenital anomalies

I. Hypoplasia of the Optic Nerve

Ophthalmoscopy reveals a small gray optic nerve. After studying normality, we have concluded that the mean surface of the optic nerve is 2.05 mm2; if the normal standard deviation is taken into account, micropapilla can be considered to be any optic disc with a surface under 1.59 mm2 and megalopapilla, any optic disc over 2.51 mm2. Regarding the micropapilla, the values we have found are quite consistent with the values obtained by Jonas: less than 1.40 mm2 (mean, 2.89 mm2 minus two standard deviations = 1.40 mm2) [30]. It is accompanied by a stained halo, tortuous vessels, and the double ring sign. Pathological anatomy accounts for this sign: the external ring corresponds to the place where the lamina cribrosa is continuous with the sclera and the internal ring is caused by the retina and the pigmentary epithelium abnormally extending over the lamina cribrosa [33, 34]. This double ring sign is exactly the opposite to what is observed in morning glory syndrome (see the following section).

Sometimes, hypoplasia of the optic nerve can be segmentary, superior, or inferior, with the correspond-

ing visual field damage. Otherwise, the visual field is characterized by a general fiber constriction and defects. Hypoplastic optic nerves are accompanied by endocrine alterations, which are also congenital anomalies, such as hypothyroidism and a deficiency of the growth hormone [35–37].

Visual acuity is varied, since it ranges from light perception to 20/20, which calls for refraction correction as soon as possible.

As regards etiology, the literature makes reference to alcohol and drugs during pregnancy, insulin-depen- dent mothers [38], and the anomalies of the CNS that accompany small optic discs or hypoplastic optic discs, located in the brain at the pituitary infundibulum and at the septum pellucidum [39].

As for pathogenesis, hypoplastic optic discs are gestational lesions in the structures of the middle line of the CNS altering axon migration [39–42] (Fig. 17.33).

Among cupped optic disc congenital anomalies can be mentioned morning glory syndrome, optic disc colobomas, and peripapillary staphylomas.

II. Cupped Anomalies

IIa. Morning Glory Syndrome

Morning glory syndrome (MGS) is a congenital alteration of the eyeball manifested as a posterior mushroomshaped cup incorporating the optic disc. It can be unilateral or bilateral. Visual acuity is almost always reduced, ranging from finger counting to 10/100, although cases with a visual acuity of 20/20 have been reported. It is more frequent in women. It was described for the first time by Graether in 1963 [43]; then Kindler [44] called it morning glory syndrome because of its resemblance to a violet bell-shaped flower that grows wild. Ophthalmoscopic examinations reveal a large orange or pink optic nerve with a mushroom-shaped cupping, surrounded in its anterior end by a thick pigmentary halo. Numerous radial vessels, more numerous than normal, where it is difficult to distinguish vessels from arteries, emerge from it. In the central part, there is a white, slightly prominent area that looks like a veil, which is glial tissue; sometimes this malformation involves the macula and in this case it is known as macular capture [45, 46]. In some cases, retinal detachment occurs, because of small holes near the optic nerve (in 26%–38% of cases, as reported by the literature [47, 48]). In other cases, there is a communication between the vitreous body and the subarachnoid space [49].

Ultrasonography shows this syndrome as a funnel in the posterior part of the eyeball that can sometimes be qualified, and in this case it is also visible with computerized tomography of the orbit.

In the retinograph of MGS, the posterior cup has the appearance of a mushroom with a white veil in the cen-

tral area corresponding to glial tissue. A dark adjacent area surrounded by choroidal depigmentation shows a macular sequestration with a small coloboma.

In a patient with unilateral MGS, the topographical image of confocal tomography shows protrusion of the ring as a very dark area (Fig. 17.34) and a pronounced depression in a horizontal section between the funnel area and the retina surrounding it.

Another patient had MGS in the right eye and a double optic nerve in the left eye, as described by Bonamour et al. [50], with a superior optic disc, a smaller one beneath this one, and below it, a choroidal coloboma.

In 1963, Graether [43] was the first to describe a transient amaurosis with venous dilatation in MGS and in 1994, Ebner et al. described a transient amaurosis with arteriolar contraction depending on the sight position [51].

In Brodsky’s 1994 article [31], the author refers to mid-facial anomalies (hypotelorism, depressed nose, palpebral alterations) as other manifestations of this syndrome. Figure 17.35 describes the main features of MGS.

MGS manifests in the CNS as a transsphenoidal form of basal encephalocele for which surgery is contraindicated, and rarely as absence of chiasma, agenesis of the corpus callosum, and dilatation of the lateral ventricles. It is sometimes also accompanied by a herniation of the hypothalamic structures (palate clefts, bone defects in the base of the skull). Brodsky also reports that sometimes there is a rhinorrhea attributable to basal obstruction caused by a polyp, the extraction of which could be lethal. An interesting paper by an Argentine author, Dr. Alezzandrini, describes RFG alterations in detail [52].