Andy C. O. Cheng
Dr. Andy Cheng graduated from the Medical Faculty of the University of Hong Kong with honors and further attained the Master of Medical Science degree with distinction in HKU specializing in morphological science and neuroscience. He holds the Diploma in Practical Dermatology qualification from the Cardiff University. He is currently the Fellow of the Royal College of Surgeons of Edinburgh, College of Ophthalmologists of Hong Kong, and Hong Kong Academy of Medicine. Dr. Cheng is the Honorary Consultant Ophthalmologist of the Hong Kong Sanatorium & Hospital and the Honorary Clinical Assistant Professor of the Chinese University of Hong Kong. He has subspecialties interest in orbit & oculoplastic surgery and neuro-ophthalmology.
The orbit is a cone-shaped space confined by the four bony orbital walls posteriorly and bounded by the orbital septum and eyelid anteriorly. The eyelids are attached to the orbital rim by the medial and lateral canthal ligament, rendering it a fairly non-expansible boundary. An acute increase in volume within the orbit, for example, due to haemorrhage or swelling, may result in an acute rise in intra-orbital pressure.
The orbit is a complex anatomic region containing the globe, orbital fat, extraocular muscles, lacrimal gland, nerves and blood vessels . Orbital compartment syndrome (OCS), due to an acute rise in orbital pressure, may compromise the perfusion of these important structures, which may result in devastating complications. For instances, permanent visual loss may result if the orbital pressure is larger than the perfusion pressure of the optic nerve or retina, resulting in ischaemic optic neuropathy or retinal artery occlusion . Studies have suggested that 60–100 min of elevated orbital pressure may result in permanent visual loss . Other mechanisms that may result in visual loss include direct optic nerve compression or stretching.
OCS can occur in any disease processes that result in an acute rise in orbital volume. Common causes include orbital haemorrhage due to head trauma, orbital or eyelid surgery, orbital injections, pre-existing vascular malformations and medical diseases resulting in bleeding tendency, accounting for about 64 % of the cases . Other causes of OCS include fulminant orbital cellulitis, intra-orbital/subperiosteal abscess, orbital emphysema, inflammation, tumours, prolonged hypoxia with capillary leak, foreign material in the orbit, massive fluid resuscitation or position-dependent oedema .
OCS is mainly a clinical diagnosis based on history and physical examination . The patient may complain of acute onset of pain, blurring, diplopia, periorbital oedema and proptosis. The symptoms may develop rapidly over a minutes or hours. A history of recent orbital or eyelid surgery, head injury, chronic sinusitis, pre-existing orbital diseases including tumours or bleeding tendency may also be elicited.