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Ocular Hypotony Secondary to Spontaneously Ruptured Sclera in Choroidal Coloboma
Arch Ophthalmol. 2004;122:1549-1551.
We describe a patient who developed unilateral optic disc edema due to ocular hypotony secondary to spontaneous rupture of the thin sclera forming the floor of a chorioretinal coloboma. B-scan ultrasonography was useful in confirming the diagnosis of a posterior filtering site. The scleral defect was successfully treated with implantation of a meridional silicone buckle.
Report of a Case
A 63-year-old white woman complained of a 3-month history of painless blurred vision in her left eye. Her medical and ocular history was unremarkable. Her best-corrected visual acuity was 20/20 OD and 20/50 OS, with intraocular pressure of 15 mm Hg OD and 4 mm Hg OS. Biomicroscopic fundus examination of the patient's left eye was remarkable for fully developed optic disc edema with gross elevation of the optic nerve head, blurred disc margins, and choroidal folds consistent with hypotony (Figure 1, A). The peripheral fundus examination showed a chorioretinal coloboma in the inferonasal equatorial retina, with an oval retinal break and a subclinical retinal detachment restricted to the colobomatous area. The size of the coloboma was about 6 disc diameters, while the size of the break was 1.5 disc diameters. The disc and the macula were not involved in the coloboma. Results of examination of the right eye were normal.
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A, Infrared image of the left fundus with a swollen disc and choroidal folds consistent with ocular hypotony. B, Wide-field fluorescein angiogram showing leakage from the optic nerve in the left eye, staining at the edge of the coloboma, and a dark area caused by the absence of the choroid and of the retinal pigment epithelium. C, Wide-field indocyanine green angiogram showing the absence of choroid as a dark area. D, B-scan ultrasound scan showing a diffuse swollen choroidal layer and a full-thickness passage between the posterior chamber and the retrobulbar tissue (arrow).
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Fluorescein angiography showed dye leakage from the optic nerve in the left eye, staining at the edge of the coloboma, and a dark area caused by the absence of the choroid and of the retinal pigment epithelium (Figure 1, B). Indocyanine green angiography confirmed the absence of choroid (Figure 1, C). B-scan ultrasound examination showed a diffuse swollen choroid and a hypoechoic region posterior to the sclerochoroidal defect in the markedly thin and deformed sclera that formed the floor of the coloboma, consistent with fluid (Figure 1, D).
On the basis of findings from the clinical examination and supporting imaging studies, a diagnosis of ocular hypotony secondary to spontaneous posterior rupture of the thin sclera, forming the floor of the coloboma, was made.
Treatment options were evaluated; the day before surgery, the retinal break was treated with laser photocoagulation along the border of the coloboma as a prophylactic procedure. During the surgery, limited prolapsed vitreous was excised, 2 vertical mattress sutures were placed between the scleral coloboma to create a deep buckle, and a meridional solid silicone buckle was fitted to cover the scleral defect, with the goal of sealing the posterior filtering site.
One year postoperatively, examination of the left eye was remarkable for a visual acuity of 20/25 and intraocular pressure of 13 mm Hg; fundus view showed the retina attached with a mildly swollen optic nerve head and some choroidal folds still present.
Comment
Typical coloboma is a congenital defect caused by the improper closure of the embryonal fissure. The reported incidence of retinochoroidal coloboma is 0.14%, and in 40% of these patients rhegmatogenous retinal detachment may develop sometime during their lifetime.1
Unilateral optic disc edema secondary to ocular hypotony after a spontaneous rupture of the thin sclera, forming the floor of the posterior chorioretinal coloboma, has not yet been described, to our knowledge. We preoperatively identified an oval retinal break that occurred within the intercalary membrane of the coloboma, with a subclinical retinal detachment restricted to the colobomatous area (type IIA according to the classification by Gopal et al1). No vitreal traction or operculum could be identified in front of the break, suggesting the atrophic origin of the break within the atavistic retinal tissue. This type of break, occurring in the retinal tissue within the coloboma, corresponds to the second type of breaks identified by Gopal et al.1
Most likely the asymptomatic retinal detachment, restricted to the colobomatous area, was caused by the break in the diaphanous tissue that is continuous anatomically with the neurosensory retina. The posterior bulging of the sclera in the affected area, forming a staphyloma, has been reported in the literature.2-3 The retinal break and the asymptomatic retinal detachment could have been present for a long time, and the spontaneous rupture of the thin sclera could have occurred afterward. A similar case of ocular hypotony secondary to spontaneous ruptured posterior staphyloma in high myopia has been described recently.4
In the present case, we believe the healing of the posterior filtering site was caused by mechanical action and by the formation of a fibrotic scar secondary to the external silicone buckle that was fitted to cover the scleral defect.
Although ocular hypotony caused by spontaneous rupture of thin sclera forming the floor of a chorioretinal coloboma is an uncommon event, an external scleral buckling technique was beneficial in this case and provides a therapeutic option.
AUTHOR INFORMATION
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Francesco Viola, MD;
Francesco Morescalchi, MD;
Enrico Gandolfo, MD;
Giovanni Staurenghi, MD
Correspondence: Dr Staurenghi, Department of Ophthalmology, University of Brescia, Via Tiraboschi 8, 20135 Milan, Italy (giovanni.staurenghi{at}unimi.it).
REFERENCES
1. Gopal L, Badrinath SS, Sharma T, Parikh SN, Biswas J. Pattern of retinal breaks and retinal detachments in eyes with choroidal coloboma. Ophthalmology. 1995;102:1212-1217.
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2. Jesberg DO, Schepens CL. Retinal detachment associated with coloboma of the choroid. Arch Ophthalmol. 1961;65:163-173.
3. Bard LA. Congenital contractural arachnodactyly and intraocular colobomas. Birth Defects Orig Artic Ser. 1979;15(5B):189-205.
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4. Mahr MA, Garrity JA, Robertson DM, Herman DC. Ocular hypotony secondary to spontaneously ruptured posterior staphyloma. Arch Ophthalmol. 2003;121:122-124.
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