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

Cup Profiles

Chamber Angle Type I

In addition to these parameters, we computed the mean profile of the optic nerve head in each group with Turbocad software (version 2.0). In order to compare the profiles to the mean profile of a normal disc, we studied a control group of 101 norma1 individuals between 5 and 25 years of age.

Figure 17.16 shows the mean profile of group 1 as compared to a normal mean profile. They are almost

Fig. 17.16 Group 1 in blue, normal profile in yellow, profile of optic disc belonging to type I congenital glaucoma

identical, because as surgery succeeded in regulating the intraocular pressure quickly, the optic nerve did not suffer.

Comparing their surfaces, it can be observed that the increase in the cup area is due to an increase in the total disc area and not to a reduction of the neuroretinal rim area. Upon its distension, the Elschnig ring becomes larger and therefore the total disc area becomes larger than in normal eyes.

Figure 17.17 shows the image of an optic disc belonging to group 1, as obtained with the HRT.

Figure 17.18 shows the mean profile of group 2, which differs significantly from the normal mean profile. It also shows a great reduction in the volume of the neuroretinal rim and a great increase in the cup volume.

With regard to the surface, there is a great increase in the cup area and a reduction in the neuroretinal rim area. The total disc area is greatly enlarged by the disten-

sion of the Elschnig ring. It should be kept in mind that this cup increase occurs at the expense of a reduction of the tilted neuroretinal rim (in blue), while the flat neuroretinal rim (in green) remains almost unchanged.

Figure 17.19 shows the image of an optic disc belonging to group 2, obtained with the HRT.

Figure 17.20 shows the mean profile of group 3, which is almost the same as the normal profile. Unlike in groups 1 and 2, the total disc area is the same as in the normal group. This correlates with the fact that there is no distension of the Elschnig ring because ocular hypertension affects the eye only after 5 years of age. This behavior is the same as in adult glaucomas, where the cup area enlargement is proportional to the neuroretinal rim area reduction.

Figure 17.21 shows an optic disc belonging to group 3, obtained with the HRT. The red point of each profile graph indicates the end of the cup and the beginning of the hyaloid duct (according to histopathologic determinations, it starts when the cup surface is less or equal to 62 µm2) In group 3, unlike in groups 1 and 2, the end of the cup remains almost at the same depth as in the normal disc, since in this group the eye is no longer elastic. In the other groups, the end of the cup is considerably displaced posteriorly.

Megalopapilla: Large Optic

Nerve Heads, or Megalodiscs

One of the most common diagnostic mistakes in daily practice is caused by megalopapilla. Direct ophthalmoscopy or biomicroscopy of a megalopapilla reveals marked pallor and great cupping. We have examined children between 4 and 14 years of age who were ready to undergo surgery for congenital glaucoma. Upon thorough study, these cases had normal axial length and corneal diameter and if perimetry was possible, there was normal visual field and no signs of congenital glaucoma.

Franceschetti and Bock [14] originally coined the term “megalopapilla” for enlarged optic discs not associated with any other morphological anomalies. Megalopapilla may present with either of two phenotypic features:

1.Normal configuration with an abnormally large optic disc, high cup/disc ratio, disc surface pallor, neuroretinal rim pallor due to the presence of axons spread over a large surface, usually round or horizontally oval-shaped optic disc cup and absence of nasalization of vessels at their point of origin (usually bilateral and congenital).

2.The cup is displaced toward the top and thus obliterates the adjacent neuroretinal rim [15]. This is less common.

The appearance of the megalopapilla thus resembles that of glaucomatous neuropathy. It is indeed a pseudoglaucomatous disc. Most cases of megalopapilla may be merely a statistical variant of normality.

Megalopapilla may occasionally result from altered optic axonal migration early in embryogenesis in children with basal encephalocele [16]. Basal encephalocele is often associated with other midline anomalies such as hypertelorism, broad nasal root, cleft lip, and cleft palate. Optic disc anomalies, such as pallor, dysplasia, optic disc pits, coloboma, and megalopapilla have been reported [17]. Caprioli has described an association between basal encephalocele and morning glory syndrome [18].

Our experience has shown that megalopapilla may be divided into congenital and acquired forms. Acquired megalopapilla is associated with type II congenital glaucomas (refractory congenital glaucomas, reoperated congenital glaucomas) [19]. Grimson and Perry [20] described an orbital glioma case that in children can lead to progressive enlargement of a previously normal-sized optic disc.

Collier [21] described four cases of megalopapilla associated with pulverulent cataract and suggested that this finding may be explained by the development of the epithelial primitive disc during the 2nd month of gestation and of the pulverulent cataract in the 3rd month of gestation.

Hirokane et al. [22] described megalopapilla in eight eyes of four children. The disc with glaucomatous-like cupping was so large that the macular diameter (DM) (measured from the center of the disc to the macular edge) to disc diameter ratio (DD) (DM/DD) was lower than 2.2. Although the cup/disc ratio and the appearance of the disc margin and the disc vessels in these cases were the same as those of glaucomatous eyes, the population they reported showed absence of rim pallor notch and nerve fiber layer defects typically present in glaucomatous eyes. These findings demonstrate the importance of determining the DM/DD ratio to differentiate megalopapilla from glaucoma in children with large optic cups.

Jonas [23] published an interesting paper on pseudoglautomatous physiologic large cups in megalopapilla using planimetric analysis of stereoscopic optic disc photographs. Upon studying 21 cases of megalopapilla, he concluded that “here are individuals with abnormally high cup/disc ratio but no pathologic findings.” It was possible to identify intrapapillary and juxtapapillary characteristics that may be helpful in the differentiation of glaucomatous eyes and normal eyes with high cup/disc ratios.

Maisel et al. [24] studied 141 native adults from the Marshall Islands. In this genetically isolated population, he found 22 eyes of 15 subjects with megalopapilla and normal IOP. Three large discs with an 18-year photographic follow-up showed no change.

Purpose

The purpose of this study is to evaluate megalopapillas in order to determine whether they constitute a different population, by showing their specific features, to find the differences between this entity and other optic nerve head neuropathies with enlarged disc area, such as congenital glaucomas, goniodysgenesis with megalopapilla, and advanced optic nerve head glaucomatous damage, and to establish the differential diagnosis between megalopapilla and pure congenital glaucomas in children.

Material

The population studied was divided into four groups: Group 1 33 cases of congenital megalopapilla, 13 of

which were not associated with any other disease, 11 were associated with goniodysgenesis, six with open-angle glaucoma, two with hypophysis nonfunctional tumors, and one with exfoliation syndrome.

Group 2 30 optic neuropathies in pure congenital glaucoma diagnosed within the 1st year of life and operated two to seven times, which became acquired megalopapilla.

Group 3 168 open-angle cases of glaucoma in the perimetric stage (with visual field defects characteristic of phase 3 or 4).

Group 4 172 normal subjects as controls.

Method

The optic nerve was evaluated with the HRT, software version 2.12 (wavelength: 680 nm). All the stereometric parameters were measured. The visual fields were examined with Octopus perimetry. Slit-lamp examination of the posterior segment, as well as daily pressure curves to obtain the mean and standard deviation were also performed.

Classification

By definition, a megalopapilla is an optic nerve head disc with a surface greater than 2.5 mm2.

Type 1 Normal configuration, bilateral, high cup/disc ratio, pale disc surface, round or oval cup and congenital. This group belongs to a previous series divided into three groups:

Group 1 Primary or pure congenital glaucomas diagnosed within the first year of age successfully operated once.

Group 2 with more than one surgery required and which is the group we have further studied here.

Group 3 Late congenital glaucomas or goniodysgenesis.

Groups 1 and 2 have a significantly enlarged axial length according to echometry, while in group 3 since diagnosis was made after 5 years of age, when the eye was no longer elastic, the axial length is normal [12]

Type 2 Cup decentered to the top, unilateral, higher frequency of cilioretinal arteries, neuroretinal rim reduced in top, round cup, and congenital.

Figure 17.22 shows different measurements made by Jonas et al. [23]. Saruhan et al. [25], Maisel et al. [24], Burk et al. [26] and Sampaolesi and Sampaolesi [27].

Figure 17.23 demonstrates that normal disc areas may be present in the glaucomas as well as in the most frequent acquired neuropathies, etc.

We will now compare the optic nerve head parameters of the megalopapilla with those of normal discs, first in terms of area, then in terms of volume, and lastly in terms of the third moment.

Fig. 17.23 Normal disc areas may be present in the glaucomas, as well as in the most frequent acquired neuropathies, neurophthalmologic disorders, and low-tension glaucomas, while reduced disc areas may be found in optic nerve hypoplasias,

children with drusen and hyperopic cases. Increased disc areas may be found in goniodysgenesis, congenital glaucomas, optic disc colobomas, optic disc pits, morning glory syndrome, myelinated nerve fibers, myopias, and megalopapillas

Parameters of the HRT

in Normal Optic Disc and Megalopapilla

The ordinates of Fig. 17.24 show the area in square millimeters, while in the abscissas, the first group compares the disc area, the second group, the rim area, and the third one, the cup area. Table 17.12 shows the static values of these comparisons, with a highly significant difference for disc area and cup area. The difference is poorly significant for rim area.

Table 17.12 Normal optic disc and megalopapilla parameters

NS not significant; * p<0.01; *** p<0.0001. The difference is poorly significant for rim area

Figure 17.25 compares volumes. The abscissa shows volume values in cubic millimeters and there are two groups represented in the ordinated, the first one showing cup volume and the second one, rim volume. The statistical analysis of Table 17.13 shows a significant difference in rim volume.

Table 17.13 Normal optic nerve head parameters

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

The ordinates in Fig. 17.26 show the values for cup shape measure and the abscissa represents the comparison between the groups studied. There is a statistically high difference which makes the image of megalopapillas always seem very pathological (Table 17.14).

The following figures compare the advanced glaucoma group (with visual field defects in phase 3 or 4) with megalopapillas.

Table 17.14 Normal optic nerve head parameters

Parameter/group Normal Megalopapilla

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

The abscissa in Fig. 17.27 shows area values in square millimeters and in the ordinate there are six groups represented in order to make a comparison in terms of disc area, rim area, rim volume, cup area, cup volume, and cup shape measure.

When comparing the megalopapillas with advanced glaucomas, there is a statistically 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 there is no significant difference as regards cup shape measure (Table 17.15).

Table 17.15 Comparison between megalopapilla and normality

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