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

Fig. 17.8 HRT Phase V

Phase V optic discs (Table 17.8) are characterized by a final decrease in retinal thickness, where the contour line is parallel to the reference plane and, in the places where there is no neuroretinal rim left, the contour line height variation diagram is below the reference plane. This correlates with the appearance of white areas in the analysis of the surfaces and with the presence of absolute visual field defects (Fig. 17.8).

All six phases are summarized in Figs. 17.9 and 17.10. In normal optic discs, as well as in the phase I disc, the Elschnig ring can only be seen in the temporal sector, whereas in all other phases, it can be seen almost to its full extent, due to fiber atrophy. The bottom of the cup can be more clearly seen from phase III onward. When the brightness of the retina is observed in each section, it can be seen that this decreases steadily from normal to phase V. Cup shape measure changes rapidly. In phase III, the cup slope is almost perpendicular, while in phases IV and V bayonet-shaped vessels are revealed. The small vessels become more and more evident and their contours are more clearly visible as they become more definite (because of atrophy of the retinal nerve fibers). Nevertheless, at first sight, the condition of the optic disc in phase V may seem better than in phase IV. Also, the time elapsed between the normal and the phase I optic disc, or between phase I

and phase II optic discs may seem the same. This is easily solved with stereometric analysis of the surfaces.

Figures 17.9 and 17.10 show the six phases together in the “Measure” menu of the HRT software, with the color-coded analysis of the surfaces. In normal optic discs, the cup is surrounded by a large neuroretinal rim and not centered in the optic disc. This occurs in normal conditions because of the substantial infiltration of fibers at the superior and inferior poles. In phase I optic discs, it is possible to see how the surface of the cup increases to the detriment of a decrease of the rim area. Simultaneously, the cup becomes central and its area invades the tilted neuroretinal rim area, thus reducing its separation from the flat neuroretinal rim. In phase II optic discs, the cup continues to increase and gets closer to the flat neuroretinal rim, leaving a thin separation covered by the tilted neuroretinal rim. The total surface of the neuroretinal rim decreases mark-

edly. In phase III optic discs, the cup increases considerably and starts to become slightly excentric, and the tilted rim disappears completely in these regions. Consequently, the cup surface borders the flat rim surface. This can sometimes cause localized defects and, together with the diffuse atrophy of the rest of the retina, it correlates with the onset of the visual field defects in this phase. In phase IV optic discs, the cup surface almost covers the complete optic disc region. The tilted rim has almost completely disappeared. Only a thin flat rim margin separates the cup from the external optic disc margin. This small volume of neuroretinal rim keeps the visual function unchanged; this is correlated with the rapid visual field loss produced when the remaining neuroretinal rim is damaged. In phase V optic discs, the cup occupies almost the entire optic disc surface and, in some sectors, where the neuroretinal rim has been completely destroyed, the cup touches the

external optic disc margin, making the total absence of the neuroretinal rim evident in that sector. White regions can occur in phase V, which are caused by the retinal surface being below the level of the reference plane in the most severely damaged sectors. These lesions produce absolute optic disc defects with a poor prognosis. In Fig. 17.11shows a chart of the five phases described above. In the left part and in the center is the rim volume corresponding to each phase, so that the phase diagnosis can be quickly made. On the right are the values that Burk obtained for these phases, which agree fully with our own. In the lower part are all the parameters of each phase so that, observing the values in computed tomography, the phase diagnosis can be made.

In order to study the optic nerve in congenital glaucoma we have developed the protocol described in the following sections.

Material

We have studied three different populations with pediatric glaucomas during childhood [6–9]. The first group (19 eyes) consisted of primary congenital glaucomas operated only once. The IOP was regulated and the axial length of the eyes stopped its enlargement after surgery. Surgery was successful.

The second group (12 eyes) consisted of children with primary glaucomas in which the IOP was regulated and the axial length of the eyes stopped its enlargement after 2–6 reoperations.

The third group (29 eyes) consisted of late congenital glaucoma, goniodysgenesis, or juvenile open angle glaucoma. As these diseases manifested later, generally between 4 and 6 years of age, the axial length of the eyes did not grow despite ocular hypertension because the sclera was no longer elastic. The intraocular pressure was regulated with medical therapy or surgery (Table 17.9).

We studied the optic discs in three groups with the Heidelberg Retina Tomograph (HRT). Three images were acquired for each eye and the mean topography was obtained. The standard deviation of the mean topography must always be lower than 30 µm.

In addition to the study of the optic disc parameters, the profiles of the optic discs of each group were studied to scale.

Parameters

We will now explain the alterations found in each parameter for each group, compared to the parameters of a group of 110 normal subjects, ranging from 5 to 25 years of age [3].

One-way analysis of variance (ANOVA) was used for overall comparison among the four groups and post hoc comparisons were done with the Tukey test. Data was considered as statistically significant if p<0.05. All tests were performed with the Graph Pad InStat software (version 2.5). Table 17.10 shows the differences between groups 1, 2, and 3, while Table 17.11 shows the differences of each group with the control (normal group).

Figure 17.12 shows the analysis of the parameters disc area and cup/disc area ratio. Figure 17.13 shows the analysis of the parameters related to the mean cup depth, maximum cup depth, cup area, and cup volume. Figure 17.14 analyzes the parameters rim volume and rim area. Figure 17.15 shows the cup shape measure and contour line height variation. In each parameter, the difference between the three groups (Table 17.10) and the difference between each group and the normal group (Table 17.11) were analyzed.

Table 17.10 Differences between the groups

P represents the results obtained with the ANOVA, including normals. * p<0.05, ** p<0.01; *** p<0.001

NS not significant

Table 17. 11 Differences with normal group

P represents the results obtained with the ANOVA, including normals. * p<0.05, ** p<0.01; *** p<0.001

NS not significant

In the three groups, statistically significant differences were found between groups 1 and 2 (p<0.05) and between groups 2 and 3 (p<0.01). No significant difference was found between groups 1 and 3. Compared to the normal group, significant differences were found only for group 2 (p<0.001) (Fig. 17.12a).

In the three groups, statistically significant differences were found between groups l and 2 (p<0.001) and between groups 1 and 3 (p<0.01). No significant differences were found between groups 2 and 3. Compared to the normal group, significant differences were found for groups 2 and 3 (p<0.0001) (Fig. 17.12b).

The difference between the three groups was statistically significant only between groups 1 and 2 and between groups 2 and 3 (p<0.001). Compared to the normal group, all three groups were significantly different (p<0.001) (Fig. 17.13a).

As with the previous parameter, the differences were statistically significant only between groups 1 and 2 and between groups 2 and 3 (p<0.001). All three groups were significantly different from the normal group (p<0.001) (Fig. 17.13b).

In the three groups, statistically significant differences were found between groups 1 and 2 (p<0.001), between groups 1 and 3 (p<0.05), and between groups 2 and 3 (p<0.01). No significant difference was found between groups 2 and 3. Compared to the normal group, significant differences were found for groups 2 and 3 (p<0.001) (Fig. 17.13c).

In the three groups, statistically significant differences were found only between groups 1 and 2 (p<0.05) and between groups 1 and 3 (p<0.001). Compared to the normal group, a significant difference was found only for group 1 (p<0.01) (Fig. 17.14a). The rim volume was larger in group 1 (glaucomas operated only once) than in group 2 (reoperated congenital glaucomas).

In the three groups, statistically significant differences were found only between groups 1 and 2 and between groups 2 and 3 (p<0.001). Compared to the normal group, significant differences were found only for groups 2 and 3 (p<0.01) (Fig. 17.13d). In group 2, the cup volume was larger than in group 1, group 3, and in normal eyes.

In the three groups, a statistically significance difference was found only between groups 1 and 3 (p<0.01). Compared to the normal group, a significant difference was found only for group 3 (p<0.05) (Fig. 17.14b). The smallest rim areas were found in eyes belonging to group 3.

In the three groups, statistically significant differences were found only between groups 1 and 2 and between groups 2 and 3 (p<0.05). Compared to the normal group, a significant difference was found only for group 2 (p<0.01) (Fig. 17.15a).

The differences between the three groups were statistically significant. Compared to the normal group, a significant difference existed only for group 2 (p<0.05) (Fig. 17.15b). This indicates that even though in congenital glaucomas there is a reduction in the number of nerve fibers, there is no localized depression in any quadrant or octant, as it occurs in adults. Therefore, in children there are no disc notches or scotomatous defects.