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Arch Ophthalmol. 2004;122:409-411.

Excavated defects of the optic disc have been associated with retinal detachment in the macula and beyond.¹ Such optic disc anomalies encompass a large clinical spectrum ranging from single, usually temporally located, optic pits, to multiple pits, to the so-called morning glory syndrome. These anomalies have been attributed to abnormal closure of the fetal fissure.¹ In most of the associated retinal detachments, a retinal break has not been found, and various hypotheses have been brought forward as to the origin of the subretinal fluid, including the vitreous and fluid from the subarachnoid space.² In most reported cases, retinal detachment is confined to the macular area; however, extensive and even complete retinal detachment may occur. We report a case with delayed sequential occurrence of perfluorodecalin (PFD) and then silicone oil in the subretinal space following retinal detachment repair in a patient with long-standing retinal detachment and proliferative vitreoretinopathy in the presence of unilateral optic pits.

Report of a Case
A 20-year-old woman had complex retinal detachment and proliferative vitreoretinopathy in her right eye. She noted a deterioration in the vision of her right eye 1 day prior to hospital admission. Her ocular history was remarkable for a progressive impairment in the peripheral visual field during the past 18 months, but she had had no dilated eye examinations in the meantime. The function of the right eye had always been worse compared with the left eye, and it was thought to be amblyopic. On examination, visual acuity was hand movements OD and 20/20 OS. Slitlamp examination was unremarkable except for anterior vitreous opacities in the right eye. Funduscopy disclosed a subtotal retinal detachment with macular involvement in the right eye. There were subretinal fibrous strands in the inferior 2 quadrants and epiretinal membrane formation with star folds peripheral to the major vascular arcades consistent with a long-standing detachment and advanced proliferative vitreoretinopathy. While the optic disc in the left eye appeared healthy, there were 2 pits noted in the disc of the right eye. A small, rather subtle depression was located at the 8-o'clock position. A larger, well-developed, obvious declivity, the bottom of which was not visible, was at the nasal disc margin (Figure 1). No diaphanous tissue was identified overlying any of the pits.

View larger version (85K): [in this window] [in a new window] Figure 1. Optic disc of the right eye in a 20-year-old patient. A small subtle depression is located at the 8-o'clock position (arrowheads), and a larger defect of the optic nerve head is present nasally (arrows).

Subsequently, pars plana vitrectomy, removal of subretinal and epiretinal membranes, inferior retinotomy, peripheral retinectomy, endolaserphotocoagulation, and silicone oil tamponade were performed. Perfluorodecalin was used intraoperatively, and all visible PFD was removed prior to air-fluid exchange and silicone oil filling. Postoperatively, the retina was completely attached and visual acuity improved to 20/60 OD. Two days postoperatively, several small droplets of PFD were noted in the subretinal space inferior to the optic disc margin. The number of droplets increased during the next 2 days, and some were advancing toward the macula (Figure 2). Therefore, another surgical procedure was performed 7 days after the initial surgery to remove all visible subretinal PFD. This was accomplished in the presence of the silicone oil tamponade by gently advancing the subretinal PFD droplets toward the inferior retinotomy margin with a blunt retina spatula (DORC International, Zuidland, the Netherlands). Once released from the subretinal space, the droplets were removed via a fluid needle and concurrent pressure increase generated by a conventional oil pump (Geuder, Heidelberg, Germany). At the end of this procedure, no more PFD droplets were visible in the subneurosensory space. However, 1 day later, new subretinal PFD droplets appeared again at the inferior disc margin. The amount of droplets increased during the subsequent days, however, at a slower rate than before. Thirteen days later, in addition to the PFD droplets, silicone oil appeared in the same subretinal area with progressive enlargement of the retinal detachment toward the fovea.

View larger version (79K): [in this window] [in a new window] Figure 2. Two days after surgery for retinal detachment, which included an inferior retinotomy, peripheral retinectomy, endolaser coagulation, and silicone oil tamponade, subretinal perfluorodecalin droplets appeared in the subretinal space at the inferior margin of the optic disc. The whitish spots represent diode laser spots.

Silicone oil was then removed, and the subretinal PFD and silicone oil was released via the inferior retinotomy (Figure 3). The vitreous cavity was now filled with air and 16% C₂F₆ gas. A subsequent redetachment associated with proliferative vitreoretinopathy, including epiretinal membrane formation and traction, necessitated another surgical procedure. This time, no PFD was used intraoperatively and prior to silicone oil tamponade, diode laser endophotocoagulation was applied around the inferior of the optic disc to generate chorioretinal scars that would prevent silicone oil from passing into the subretinal space. Three months later, the retina remained attached, no new subretinal PFD or silicone oil occurred, and best-corrected visual acuity was 20/100 OD.

View larger version (57K): [in this window] [in a new window] Figure 3. Intraoperative photograph showing subretinal silicone oil inferior and temporal to the optic disc.

Comment
Congenital pits of the optic nerve head represent a rare abnormality, occurring in approximately 1 in 11 000 patients.² Their pathogenesis is not completely understood but is thought to be related to anomalies of closure of the fetal fissure. Pits of the disc are usually unilateral but may occur in both eyes. Most often, they are present on the temporal edge of the disc, but they may be multiple and have been observed in other meridians. Clinically, the pits may vary considerably in size, ranging from subtle, barely visible depressions to well-developed, obvious declivities.

Serous macular detachment develops in 25% to 75% of eyes with optic nerve pits.³ The pathophysiologic explanation of this complication is controversial. Several theories have been brought forward including leakage from the vessels at the base of the pit,⁴ leakage from the parapapillary choroidal circulation, leakage from the cerebrospinal fluid,^5-6 and leakage from the vitreous cavity.^{3, 7}

The case reported here clearly demonstrates that there may be a communication between the vitreous cavity and the subretinal space via the optic pit and that this may be the cause for retinal detachment. The most likely explanation for the appearance of subretinal PFD and silicone oil bubbles several days postoperatively is a reservoir posterior to the optic disc plane not visible by biomicroscopy and a communication between the optic disc pit and the subretinal space. Various possibilities may be considered for such a reservoir including the subarachnoid space around the optic nerve or posterior herniation of abnormal tissue composing the true "floor" of the pit. While instant leakage of PFD under the retina was noted intraoperatively in the presence of a morning glory disc anomaly by Bartz-Schmidt and Heimann,⁸ this is, to the best of our knowledge, the first description of a delayed occurrence of PFD and silicone oil in the presence of optic pits.

It has been demonstrated in an animal study⁷ that india ink placed in the vitreous cavity flowed into the pit and subretinal space, supporting the hypothesis that the subretinal fluid originates from the vitreous cavity. Bonnet³ as well as Postel et al⁹ reported eyes with optic pits and associated retinal detachment managed with intravitreal gas injection, in which gas bubbles migrated through a small break in tissue overlying the optic pits into the subretinal space postoperatively. Coll et al¹⁰ reported a communication between the subretinal space and the vitreous cavity in the morning glory syndrome.

Our case suggests that PFD should be avoided in retinal detachment surgery in eyes with optic pits. Furthermore, intraocular air/gas tamponade may be preferable to silicone oil tamponade if feasible to prevent the complications previously mentioned. The lower interfacial tension of silicone oil was not adequate to prevent bubbles of silicone oil from passing through the small retinal opening within the optic disc. Endolaser photocoagulation for formation of a barrier to fluid movement was effective here to prevent silicone oil from passing into the subretinal space. Such laser treatment appears prudent in similar cases when air/gas tamponade is insufficient to secure retinal attachment and when silicone oil must be used. The volume of both subretinal PFD and silicone oil increased during a short period of time. It is currently unknown which unidirectional forces are operative to efficiently move fluid from the vitreous cavity through the optic pit under the neurosensory retina. A pressure gradient must be assumed whereby gravity forces are unlikely because PFD and silicone oil owing to their specific weights would be expected to behave differently. It may be speculated that the pressure gradient is the difference between the intraocular pressure at the moment of migration and the pressure within the reservoir (ie, either the extraocular tissue pressure or the pressure within the subarachnoid space).

AUTHOR INFORMATION

Stefan Dithmar, MD; Florian Schuett, MD; Hans E. Voelcker, MD; Frank G. Holz, MD
Heidelberg, Germany

Corresponding author: Stefan Dithmar, MD, Department of Ophthalmology, University of Heidelberg, Im Neuenheimer Feld 400, 69120 Heidelberg, Germany (e-mail: stefan_dithmar{at}med.uni-heidelberg.de).

REFERENCES
1. Sugar HS. Congenital pits of the optic disc and their equivalents (congenital coloboma and colobomalike excavations) associated with submacular fluid. Am J Ophthalmol. 1967;63:298-307. PUBMED 2. Kranenburg EW. Crater-like holes in the optic disk and central serous retinopathy. Arch Ophthalmol. 1960;64:912-924. 3. Bonnet M. Serous macular detachment associated with optic nerve pits. Graefes Arch Clin Exp Ophthalmol. 1991;229:526-532. PUBMED 4. Gordon R, Chatfield RK. Pits in the optic disk associated with macular degeneration. Br J Ophthalmol. 1969;53:481-489. FREE FULL TEXT 5. Gass JDM. Serous detachment of the macula secondary to optic disk pits. Am J Ophthalmol. 1969;67:821-841. PUBMED 6. Krivoy D, Gentile R, Liebman JM, et al. Imaging congenital optic disk pits and associated maculopathy using optical coherence tomography. Arch Ophthalmol. 1996;114:165-170. ABSTRACT 7. Brown GC, Shields JA, Goldberg RE. Congenital pits of the optic nerve head, I: experimental studies in collie dogs. Arch Ophthalmol. 1979;97:1341-1344. ABSTRACT 8. Bartz-Schmidt KU, Heimann K. Pathogenesis of retinal detachment associated with morning glory disc. Int Ophthalmol. 1995;19:35-38. PUBMED 9. Postel EA, Pulido JS, McNamara JA, Johnson MW. The etiology and treatment of macular detachment associated with optic nerve pits and related anomalies. Trans Am Ophthalmol Soc. 1998;96:73-88. PUBMED 10. Coll GE, Chang S, Flynn TE, Brown GC. Communication between the subretinal space and the vitreous cavity in the morning glory syndrome. Graefes Arch Clin Exp Ophthalmol. 1995;233:441-443. PUBMED

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