Normal pressure glaucoma (or normal tension glaucoma) is an optic neuropathy associated with low intraocular pressure (ie less than 22 mmHg).
The following are known associations of normal pressure glaucoma: • steroid use (eg nasal sprays, inhaled or oral steroids, or steroid creams) - in this case steroids may infact elevate IOP but this may not be detected and be falsely diagnosed as normal pressure glaucoma • vasospasm – migraine / Raynauds • coagulopathies – previous blood loss or shock like epsiode • systemic nocturnal hypotension • autoimmune disease • thyroid disease (increased risk) • sleep apnoea (especially in overweight men) • Alzheimer's disease
Other problems to be considered • intermittent IOP elevation - can be excluded with diurnal IOP measurements • burnt out glaucoma • congenital anomaly • myopia with peri-papillary atrophy • optic nerve coloboma • vascular etiology • carotid occlusion • previous blood loss • hereditary optic neuropathy • Lebers optic neuropathy • tonometric error (thin cornea)
Investigations • FBC – rule out anaemia • CRP / ESR – rule out a condition called "anterior ischaemic optic neuropathy" • VDRL/FTA – syphilis is a very rare association • ANA – autoimmune diseases, also Ro, La, Sm • paraproteinaemia – rule out lymphoproliferative disease • Lebers – mitochondrial testing where indicated
Imaging • HRT / OCT / GDx • MRI if asymmetry, unusual VF, progressive fields, dyschromatopsia, APD with mild cupping • carotid dopplers • CXR to rule out sarcoidosis
Other tests • 24 hour ambulatory blood pressure monitoring
Treatment • ALT not recommended • Trabeculectomy with Mitomycin C, if IOP in single digits is required • In some cases, your physician might recommend Ginkgo Biloba (40mg three times a day). There is some evidence that points to a benefit here, but this medication is not suitable for everyone and it's use is advised on a case-by-case basis, after discussion with your glaucoma specialist. • Future medication, for selected subgroups of patients with glaucoma, may include memantine, a tablet medication that may have beneficial protective effects on the optic nerve (randomised controlled trials are awaited).
Optic disc showing cupping - a sign of glaucoma
Ginkgo Biloba
Ginkgo Biloba is extracted from a plant
Blood pressure monitoring is important
Mitomycin C is an agent used in glaucoma surgery to reduce scarring
The information on our website is for educational purposes only and is not to replace a consultation with an eye care professional. The condition of each patient is unique and needs to be evaluated properly before any decision can be taken. For appointments with Mr P Galloway contact: BUPA Hospital Leeds, Jackson Avenue, Roundhay, Leeds, West Yorkshire, LS8 1NT, UK. T:0113 269 3939; for Mr Burnett please click here.
