for early evidence of rise in intracranial pressure. Pale disc A normal optic disc is orange to pink in colour and may vary based on ethnicity. A pale disc is an optic disc which varies in colour from a pale pink or orange colour to white. A pale disc is an indication of a disease condition. Imaging Traditional colour-film camera images are the reference standard in imaging, requiring an expert ophthalmic photographer, ophthalmic technician, optometrist or an ophthalmologist for taking standardised pictures of the optic disc. Stereoscopic images offer an excellent investigative tool for serial follow-up of suspected changes in the hands of an expert optometrist or ophthalmologist. Automated techniques have also been developed to allow for more efficient and less expensive imaging. Heidelberg retinal tomography (HRT), scanning laser polarimetry and optical coherence tomography are computerised techniques for imaging various structures of the eyes, including the optic disc. They quantify the nerve fiber layer of disc and surrounding retina and statistically correlate the findings with a database of previously screened population of normals. They are useful for baseline and serial follow-up to monitor minute changes in optic disc morphology. Imaging will not provide conclusive evidence for clinical diagnosis however, and the evidence needs to be supplanted by serial physiological testing for functional changes. Such tests may include visual field charting and final clinical interpretation of the complete eye examination by an eye care physician. Ophthalmologists and optometrists are able to provide this service. Blood flow in the retina and choroid in the optic disc region can be revealed non invasively by near-infrared laser Doppler imaging. Laser Doppler imaging can enable mapping of the local arterial resistivity index, and the possibility to perform unambiguous identification of retinal arteries and veins on the basis of their systole-diastole variations, and reveal ocular hemodynamics in human eyes. Furthermore, the Doppler spectrum asymmetry reveals the local direction of blood flow with respect to the optical axis. This directional information is overlaid on standard grayscale blood flow images to depict flow in the central artery and vein. A systematic review of 106 studies and 16,260 eyes compared the performance of the imaging techniques, and found that all three imaging tests performed very similarly when detecting for glaucoma. The review found that in 1000 patients subjected to imaging tests, with 200 having manifest glaucoma, the best imaging tests would miss 60 cases out of the 200 patients