Congenital colobomatous malformations of the optic nerve - papillary coloboma, morning glory anomaly (MGA), and peripapillary staphyloma - are entities with clearly differing clinical and anatomic-pathologic characteristics, although intermediate forms do exist. Nevertheless, these malformations are not always stable throughout time.
Ocular and systemic disturbances associated with these malformations have been described, as have acquired complications (retinal detachment [RD] and subretinal hemorrhages).
The objective of this study is to describe the variations in the Ophthalmoscopic aspect of some clinically wellestablished papillary colobomatous anomalies that, during their evolution, have acquired characteristics that are completely different from the original ones.
Before discussing the evolution and possible complications associated with colobomatous malformations of the optic nerve, we will briefly describe their clinical characteristics.
Morning Glory Anomaly
The Ophthalmoscopic characteristics of MGA were originally described by Kindler.1 They consist of an enlargement of the optic disc that is found in the posterior zone of a deep, funnel-shaped excavation with an orangish-pink color. Surrounding this excavation there is an irregularly raised area of the peripapillary retina that shows pigment alterations of a dark blue color, which is the most distinguishing characteristic of this anomaly. In general, it is difficult to define the junction of the disc and the peripapillary retina. In the center and ahead of this "papillae," there is always an ill-defined, grayish-white fibrous tissue, glial in origin, that probably is composed of the remains of Bergmeister's papillae. The retinal vessels appear to emerge from the periphery of the disc and to be present in a greater number than is normal, extending radially above the peripapillary ring toward the peripheral retina. They are narrowed and follow an abnormally rectilinear course. Vascular sheaths can be seen near the papillae. It is frequently difficult to distinguish between arteries and veins. The macula and its xanthophyll pigment may be partially or totally contained within the defect, which is known as "macular capture."
This is generally a unilateral process.
Ocular ultrasonography and computerized axial tomography (CAT) usually reveal a thickening of the optic nerve at the level of the ocular insertion and an elevation of the edges of the papillae with respect to the retinal plane.2
In the Ophthalmoscopic picture described as a typical papillary coloboma, the papillae generally appears irregularly enlarged with a well-defined, brilliant whitish excavation that varies in size. In most cases, the malformation is greater in the lower nasal zone of the papillae, and the upper edge is less altered. In others, the disc may be totally excavated with its lower portion deeper than the upper portion. Associated pigment alterations hyperpigmentation or hypopigmentation) may be found in the peripapillary zone in the immediate vicinity of the defect. There are no surrounding retinal alterations. A grayish-white tissue is observed occasionally in the depth of the lesion, which may give the appearance of MGA. Thus, it is sometimes difficult to classify a papillary colobomatous defect as a papillary coloboma or as a variant of MGA. In cases where the excavation is wide and deep, ectasia of the optic nerve are formed that lead to retrobulbar formations of a cystic aspect that are very obvious by computed axial tomography (CAT) or ultrasonography.
FIGURE 1: Nonrhegmatogenous detached retina associated with a coloboma.
FIGURE 2: Spontaneous reattachment. Retinochoroid coloboma that covers the papillae in Figure 1.
This affectation may be bilateral or unilateral. Most cases are sporadic, but there are dominant autosomal hereditary forms with varying phenotypical expression that are preferentially bilateral.3·4
In this anomaly, which is also known as scierai ectasia, ophthalmoscopic examination reveals a deep depression or ectasia of the posterior pole of the eyeball with a normal or very slightly altered papulae in the fundus, unlike typical papillary colobomas and MGA. There is no accumulation of prepapillary glial tissue. The walls and edge of the staphyloma show alterations in the choroid and in the pigment epithelium. The margin is more abrupt and irregular, which makes the retinal vessels, which have a normal pattern, curve inward when passing through it.
This defect is generally unilateral.
Thus, peripapillary staphyloma shares with MGA the fact that an unusually large opening of the sclera contains the optic nerve, while in papillary coloboma it is the optic nerve that contains the excavation. Peripapillary staphyloma is distinguished from MGA by a greater depth of the lesion, a relatively normal and well-differentiated disc and the absence of prepapillary and peripapillary vascular and glial alterations.
In addition to these typical clinical forms, intermediate forms have also been observed of simultaneously combined clinical characteristics of more than one of these anomalies (papillary coloboma-MGA, MGAperipapillary staphyloma, and retinochoroid coloboma-papillary coloboma combinations).5
The papillary malformations described have three additional common characteristics:
An Association With Other OcuJar and Systemic Anomalies. Colobomatous anomalies of the optic nerve, along with other congenital ocular anomalies, may appear alone, associated with other ocular malformations or as a part of chromosomopathies or multisystemic pediatrie syndromes.
MGA has been described in association with many other alterations6:
* Ocular anomalies in the same eye. Notable ocular anomalies in the same eye are: retinochoroid coloboma, PHPV, anterior chamber cleavage syndrome,7 remains of the hyaloid artery, remains of the pupillary membrane, microphthalmia, aniridia, and remains of Bergmeister's papillae,3 among others.
* Anomalies of the other eye. The following have been observed: microphthalmia, anterior chamber cleavage syndrome, microcornea, and remains of the pupillary membrane.
* Associated systemic anomalies. These include: basal encephalocele, cleft palate and lip, renal anomalies,8 and the absence of the corpus callosum.
Coloboma of the optic nerve may occur in combination with a retinochoroid coloboma or in association with other ocular anomalies such as iris or lens coloboma, microphthalmia,9 papillary fossae, or remains of the hyaloid artery3 that may occur in either the same or the other eye. It also has been described as forming part of malformation syndromes such as Seckel syndrome, Cornelia de Lange syndrome, Hallennan-Sfrreiff syndrome, and Krause syndrome.9
Notable among the systemic anomalies associated with MGA and papillary coloboma is transsphenoidal or basal encephalocele.
Peripapillary staphyloma usually is not associated with other ocular or systemic anomalies.
* Nonrhegmatogenous detachment of the retina. This is associated with approximately 25% to 35% of the cases of papillary coloboma or MGA. These cases are generally more serious and precocious than those with associated papillary fossae. They may be localized in papillary macular or lower papillary areas, although they may also be extended peripherally (Figs 1-2). Despite spontaneous résorption, 25% of these cases have a very bad prognosis, ending in blindness.5
FIGURE 3: Case 1. Morning glory anomaly with falciform fold and retinochoroid coloboma in the left eye lower nasal sector. Nine months old.
FIGURE 4: Cose 1. Ophthalmoscopic aspect at 9 years old.
Subretinal hemorrhages. These originate from peripapillary subretinal neovessels or from secondary subretinal membranes. They may cause a hemorrhagic detachment of the retina.2
Variations of the Ophthalmoscopic Aspect. Several authors have described contractile or pulsating movements associated above all with peripapillary staphyloma.10"12 These movements also have been seen in MGA and papillary colobomas,13"15 leading to periodic variations in the size of the papillary defect without changing the lesion's aspect definitively.
Progressive and irreversible variations of the Ophthalmoscopic appearance have been observed in some patients, although it has not been possible to attribute them to associated concurrent complications.2'5 This latter aspect has been the least studied and described, and is the object of this study.
Case 1. The patient was a 9-month-old boy with no relevant pathologic or family history who was examined in 1984 for microphthalmia in the left eye. Corneal diameters were 10 mm in the right eye and 8 mm in the left eye. Ophthalmoscopic exploration of the left eye revealed MGA next to a falciform fold in the lower nasal sector that ended with a retinochoroid coloboma at the preequatorial level (Fig 3). At 3 years of age, the fundus of the eye remained unchanged and visual acuity was 1 in the right eye and 0.05 in the left eye. At 9 years of age, important changes were found in the ophthalmoscopic aspect, especially at the papillary level, which gave the lesion a very different appearance from the original one. The colobomatous excavation was reduced and the edges of the papillae were well defined and not raised, surrounded with areas of peripapillary hypopigmentation and hyperpigmentation (previous peripapillary retinal detachments?). There were pigmented deposits around the retinochoroid coloboma and decreased evidence of the falciform fold (Fig 4).
FIGURE 5: Case 2. Papillary coloboma in the right eye with a deep central excavation. Seven months old.
Case 2. This patient was a 7-month-old girl with no relevant pathologic or family history. In 1980, she was diagnosed as having congenital microphthalmia in the right eye. At exploration, she had corneal diameters of 8.5 mm in the right eye and 11 mm in the left eye, with no other alterations in the anterior segment. There was a large, well-defined and deeply excavated papillae in the fundus of the right eye. Abnormal rectilineous vessels were emerging from the deep bottom and through the rim of the excavation. There were alterations of retinal pigmentary epithelium in the peripapillary zone. The ophthalmoscopic appearance of the right eye was of a papillary coloboma (Fig 5). The left eye was normal. Ultrasonography and CAT revealed a retro-ocular image at the papillary level of the right eye with characteristics compatible with those of a large ectasia of the optic nerve of cystic structure. The cyst was open into the ocular cavity through the papillary coloboma (Figs 6-7). After a lengthy ophthalmoscopic followup period with no changes, a peripapillary subretinal hemorrhage appeared (Fig 8). When the hemorrhage reabsorbed, the earlier aspect of the coloboma was changing slowly through the time. Currently, there is a closing of the colobomatous excavation, elevation and pigmentation of the papillary edges, and incurvation of the retinal vessels. The ophthalmoscopic characteristics of this structure are compatible with those of an MGA (Figs 9-10).
FIGURE 6: Case 2. Ultrasonography from the first exploration.
There has been speculation that the embryogenesis of these excavated lesions of the posterior pole of the eyeball may be due to a dysgenesis or alteration in the normal development of the distal portion of the vesicle and optic stalk at some point in the period when the embryonic fissure is closed.
Anatomic-pathologic descriptions of malformations of the optic nerve are rare and generally have been in eyes with MGA that have been enucleated because of the suspicion of a neoplasm or for an RD of unknown etiology. All coincide in that the origin of this malformation is a mesectodermic dysgenesis that affects the optic nerve. This hypothesis is based on the association of histologie findings presented by various authors7'16"20: the absence of or a defect in the famina cribrosa; a peripapillary scierai defect; the presence of anomalous mesodermic tissue formed by the accumulation of smooth muscle and adipose tissue, in areas of the optic nerve lacking meninges and among the scierai lamina that surround the peripapillary defect; anomalous blood vessels at the level of the optic nerve; a recess formed by an axial displacement of the optic nerve and retinal tissue that shows signs of fibrosis and glial degeneration; a covering of the inside of the sclera! defect by a continuous layer of pigment epithelium, generally hyperplastic or with pseudofibrotic metaplastic degeneration18; and persistence of the primitive hyaloid system, consisting of fibroglial tissue, as a principal characteristic of this anomaly.
The isolated papillary coloboma is believed to be the result of a failure in the closing of the backmost portion of the embryonic fissure. Therefore, this defect only affects the head of the optic nerve, causing an excavation of varying size, owing to the localization of the primitive embryonic fissure. Although some papillary colobomas affect the entire disc, a constant asymmetry may be observed in their morphology, which confirms the asymmetrical structure of their origin, that is, once the structures of the optic nerve are formed at the proximal level and this is differentiated from the other ocular structures, the remaining fissure fails to close completely.
FIGURE 7: Case 2. Computed axial tomography for Figure 6. A large retrobulbar cystic formation is seen at the level of the papillae.
FIGURE 8: Case 2. Peripapillary subretinal hemorrhage seen at follow up.
Along with papillary colobomas, retinochoroid or iridian colobomas can be found; even simple hypopigmented areas in the fundus of the eye can be found that run the length of the supposed closure line of the fissure, forming an extensive set of ophthalmoscopic variants. These variants represent a failure in the closing of the embryonic fissure in previous stages.
FIGURE 9: Case 2. Several months later. Excavation is closing with elevation and pigmentation of the edges and incurvation of the papillary vessels. Twelve years old.
FIGURE 10: Case 2. Aspect at last follow up.
Peripapillary staphyloma has its origin in an anomaly in the development of the sclera.21 This development begins in the anterior zone of the eyeball and progresses to the posterior zone, starting from the paraxial mesoderm.22
A failure in the formation of the sclera in the posterior pole of the eye would lead to secondary alterations in the retinal and choroid tissues in the defect. Theoretically, these tissues, as well as the papillae and its vessels, should have a histologie structure without dysgenic alterations, because they should have been formed in phases prior to that of the scierai anomaly; however, there are no documented histopathologic data to verify this hypothesis. An error at some point in the embryonic development would explain the origin of the primordial colobomatous lesion. Nevertheless, the variations and complications incurred by these malformations throughout an individual's lifetime have been the subject of multiple conjectures and theories, especially insofar as contractile colobomas are concerned.
Contractile movements have been described in cases of MGA and peripapillary staphyloma. 10-12,14,23.24 These movements follow two different patterns, depending on whether they are associated with MGA or peripapillary staphyloma. In MGA, the type of movement is associated with a detachment of the retina in the inside of the excavated portion of the lesion, which varies in the size or degree of retinal elevation in an intermittent form. These variations in size would reflect a passive response to changes in the pressure grathents among the intraocular, intraorbital, and intracranial compartments. Contrarily, the type of movement associated with peripapillary staphyloma would be the result of intermittent activity of a contractile tissue located in the walls of the lesion in response to a stimulation from the autonomie nervous system.
Progressive variations in the ophthalmoscopic aspect of these malformations are usually nearly imperceptible over time and could occur simply with the growth of the eye, as described in the first case. More obvious changes are less frequently observed, as in the second case. In any event, there are no clear clinical signs to indicate conclusively the cause of these changes. Nevertheless, our last case could be explained, in part, by the theory that attributes the clinical variations of these malformations to an accumulation of subretinal fluid. The fact that the lesion takes on an aspect that is definitively and not intermittently different from its original one leads to the thought of an additional cicatricial factor. This cicatrization would respond to two physiopathologic mechanisms: One mechanism is the subretinal hematic collection that would lead to the appearance of a subretinal fibrous proliferation and would later maintain the elevated peripapillary retina, also distorting the papillary vessels. Another mechanism could be the retraction of a preexisting prepapillary fibroglial tissue or membrane that, in turn, would create traction in the disc, in its vessels, in the vitreum, and in the peripapillary retina, leading to serous detachment of the retina and subretinal hemorrhage, from anomalous papillary vessels. Without histologie confirmation, it is only possible to speculate, although we think that the latter would be the physiopathologic mechanism that would explain our second case.
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