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Abstract #8171 Published in IGR 4-3
Optic disc movement with variations in intraocular and cerebrospinal fluid pressure
Morgan WH; Chauhan BC; Yu DY; Cringle SJ; Alder VA; House PHInvestigative Ophthalmology and Visual Science 2002; 43: 3236-3242
PURPOSE: To determine the effect of intraocular pressure (IOP) and cerebrospinal fluid pressure (CSFP) on optic disc movement and lamina cribrosa displacement using confocal scanning laser tomography (CSLT). METHODS: The anterior chamber and lateral ventricles were cannulated in mixed-breed dogs (n = 8) to allow modulation and control of IOP and CSFP, respectively. Optic disc topography was determined after baseline (set at IOP 15 mmHg and CSFP of 0 mmHg) and with each step-wise increase in IOP (steps of 3-5 mmHg up to an average of 32 mmHg) with CSFP fixed at 0 mmHg. After the pressure returned to baseline, images were obtained after each step-wise increase in CSFP (steps of 2-4 mmHg up to an average of 12 mmHg) with IOP fixed at 15 mmHg. Data were analyzed by a new probabilistic method for CSLT and global parameters generated by the instrument software. The global parameter changes from baseline were analyzed as a function of the translaminar pressure difference (IOP minus CSFP). RESULTS: Elevation in IOP resulted in significant posterior displacement of the disc surface, whereas elevation in CSFP resulted in significant anterior displacement. For a given degree of pressure change, an increase in CSFP resulted in larger changes than a corresponding increase in IOP. The deepest 5% of locations within the disc surface were displaced nonlinearly (with an inverse exponential function, r = 0.92) as a function of the difference in translaminar pressure. Most displacement occurred at low translaminar pressure differences, with little extra movement at differences higher than 15 mmHg. The change in the volume subtended by the anterior lamina cribrosa showed a nonlinear relationship similar to the translaminar pressure difference (r = 0.98), with negligible volume change at high difference in pressures. CONCLUSIONS: Most optic disc movement occurs with pressure changes in the low range of translaminar pressure differences. This is consistent with the mechanical properties of collagen.
W.H. Morgan, MD, Lions Eye Institute, University of Western Australia, Perth, Australia. whmorgan@cyllen.uwa.edu.au
Classification:
2.14 Optic disc (Part of: 2 Anatomical structures in glaucoma)
5 Experimental glaucoma; animal models
