Tomographic Evaluation of Optic Nerve Head Pits by Spectral Domain OCT

FP 694/ E Poster No 243

Dr Unnikrishnan NairAIOS 10193

Aim & Methodology

• To analyse the various clinical and tomographic features like the position and nature of the pit, associated schisis , glial components over the disc , presence of SRF and PVD and extent of foveal involvement in a series of 13 patients with ONH pits

• 5 Line raster , Macular Cube 512 X 128 of the Carl Zeiss Cirus HD OCT were used to assess the tomographic features

Clinical appearance of ONH Pits

Pit with Schisis & RD

Asymptomatic Pit

Pit with resolved fluid and Extensive RPE atrophy

Tomographic features evaluated

• Pit communication with schisis• Pit communication with vitreous• Pit communication into substance of ONH• Schisis• SRF• Glial tissue over disc• Cloquets canal remnants• Presence or absence of PVD• IS OS loss at fovea

Pit communication with schisis

Communication of pit with schisis

Pit communication with Vitreous and Subarachnoid space

Communication of pit between VC & SAS

SchisisPit edge

Diaphanous membrane/glial tissue over pit Break in diaphanous membrane

Cloquet Canal Remnants originating from depth of cup

Schisis & SRFSchisis

SRF SRF

Traction on glial tissue supposedly keeping communication between schisis open

Communication of pit with schisis

Glial Tissue over pit

Glial Tissue in cup

Tomographic features

Communication of pit with schisis 8/10 with schisis

Communication between SAS and Vitreous cavity through Pit

11/13

Schisis 10/13

Subretinal Fluid 5/13

Glial remnants 9/ 13

Traction at Disc 7/9 with glial tissue on disc

Cloquets remnants 8/13

No PVD 11/13

No PVD in schisis 9/10

Pathogenesis • Congenital pits of the optic nerve head result from an

imperfect closure of the superior edge of the embryonic fissure. An unequal growth on both sides causes a delayed closure of the fissure at approximately 5 weeks of gestation.

• The outgrowth of axons from certain ganglion cells may be incomplete so that the primitive epithelial papilla is built up with aberrant nerve fibres.

• These anomalous papillomacular nerve fibre bundles may be less resistant, predisposing this sector to spontaneous schisis-like retinal detachments during later life

Mechanism causing optic disc pit maculopathy

• It has been considered to be vitreous traction on the optic disc pit

• A reservoir for the fluid from the subarachnoid space might be the vitreous cavity with an egress into it provided by some retinal fenestration near the optic nerve head

• Egress into the Schisis space is considered to be due to traction at the optic nerve edge redirecting fluid intraretinally.

Comparative studies• Postel et al described a hole or tear in the diaphanous

tissue overlying the optic pit in all of their seven cases• Akiba et al noted a residual Cloquet's canal moving in

concert with a pulsating translucent membrane over the optic disc pit to cause anterior-posterior vitreous traction. The glial tissue might have developed after continuous vitreous traction of the vitreous strand attached to the optic disc pit

• Bonnet et al reported that 25 eyes with a macular detachment associated with an optic disc pit did not have a PVD

1. Bonnet M. Serous macular detachment associated with optic nerve pits. Graefes Arch Clin Exp Ophthalmol 1991;229(6):526–532..

2. Akiba J, Kakehashi A, Hikichi T, Trempe CL. Vitreous findings in cases of optic nerve pits and serous macular detachment. Am J Ophthalmol. 1993 Jul 15;116(1):38–41

Conclusion

• The following features have been noted and may explain the reason for pits developing schisis and RD

• Communication between a schisis cavity or subretinal space and the optic nerve pit

• Cystic degeneration and schisis • A direct communication between the subretinal

space and vitreous cavity• Glial tissue with traction and absence of PVD