NHMRC Glaucoma Guidelines - ANZGIG

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NHMRC GUIDELINES FOR THE SCREENING, PROGNOSIS, DIAGNOSIS, MANAGEMENT AND PREVENTION OF GLAUCOMA Chapter 7 – Diagnosis of glaucoma Symptoms described by the patient Open angle glaucoma is generally symptomless in its early stages. It is not until significant neuronal damage has occurred that characteristic visual loss is observed. Acute angle closure (AAC) is associated with significant and distressing symptoms. These may present as either an acute scenario, or as patient descriptions of past attacks. Chronic angle closure symptoms are often absent. The symptoms that should alert health care providers to the presence of AC are detailed in Table 7.1, extracted from the European Glaucoma Society [EGS] (2003). Table 7.1: Symptoms of angle closure SYMPTOMS Acute angle closure Intermittent angle closure Chronic angle closure Blurred vision √ At time of attack presents as AAC Between attacks may be symptomless Variable – chronic angle closure mimics primary open angle glaucoma It is asymptomatic until visual field loss interferes with quality of life Coloured rings around lights √ Transient if present Pain √ Not usually Frontal headache √ Discomfort rather than pain Palpitations and abdominal pain Nausea and vomiting √ √ X X Examination of eye structure Glaucoma describes a group of eye diseases in which there is progressive damage to the optic nerve. This is characterised by specific structural abnormalities of optic nerve head and associated patterns of VF loss (Burr, Azuara-Blanco & Avenell 2004). Changes that occur in glaucoma include excavation of the optic nerve head (often termed cupping), loss of neuroretinal rim, and frequently, optic disc haemorrhages. It is essential to use the best possible approach to eye examination to identify these changes. Optic disc Ophthalmoscopy: Direct ophthalmoscopy is best performed with the pupils dilated and the room darkened. This provides a magnified view of the optic disc. The main disadvantage is the absence of a stereoscopic view. Indirect ophthalmoscopy performed with a slit lamp yields a magnified stereoscopic view of the optic disc and retinal nerve fibre layer. It is the examination method of choice. National Health and Medical Research Council 69
NHMRC GUIDELINES FOR THE SCREENING, PROGNOSIS, DIAGNOSIS, MANAGEMENT AND PREVENTION OF GLAUCOMA Chapter 7 – Diagnosis of glaucoma Optic disc photography: A wide variety of digital and non-digital cameras are available to provide colour images of the optic disc. Photography has an advantage over ophthalmoscopy of a permanent recording of the optic disc. However for optimal results, it requires a dilated pupil and relatively clear media. Monoscopic photographs can be obtained with a standard fundus camera; however, the tridimensional structure of the optic disc can only be assessed by stereo photography. Stereoscopic pictures can be obtained with sequential photographs using a standard fundus camera by horizontal realignment of the camera base when photographing the same retinal image. Alternatively, simultaneous stereoscopic fundus photographs can be obtained. Retinal nerve fibre layer Nerve fibre photography: Assessment of the nerve fibre layer is similar to optic nerve assessment and is enhanced with red-free illumination. The appearance of the retinal nerve fibre layer may be documented using high-resolution images. The fibre bundles are seen as silver striations, most visibly radiating from the superior and inferior poles of the optic disc. The time taken for this procedure is similar to that required for optic disc photography. In the early stages of glaucoma, estimation of structural abnormalities from serial nerve fibre layer photographs may be more sensitive than assessment of the optic nerve head itself (American Optometric Association [AOA] 2002). Scanning laser ophthalmoscopy: i.e. Heidelberg Retinal Tomography provides objective, quantitative measures of the optic disc topography and shows promise for discriminating between glaucomatous and normal eyes (Miglior, Guareschi, Albe et al 2003). Optical coherence tomography: Optical coherence tomography is an optical imaging technique used to measure the thickness of the retinal nerve fibre layer. It is most useful to detect early glaucoma. It provides high-resolution, cross-sectional, in vivo imaging of the human retina in a fashion analogous to B-scan ultrasonography, using near infrared (840nm) light instead of sound (Johnson, Siddiqui, Azuara-Blanco et al 2007). Using the principles of low coherence interferometry with light echoes from the scanned structure, optical coherence tomography determines the thickness of tissues. In most commercially available optical coherence tomographies, successive longitudinal scanning in a transverse direction creates two-dimensional images. They can scan the optic nerve head, macular region as well as the peripapillary retinal nerve fibre layer. There is scant information about its diagnostic accuracy. Scanning laser polarimetry Equipment such as GDx provide an objective, quantitative measure of the retinal nerve fibre layer thickness by using the retardation of a reflected 780nm polarized laser light source. No single test (or group of tests) appears to be more accurate than any other for diagnosing glaucoma, regardless of the type (Burr, Mowatt, Hernandez et al 2007). Table 7.2 outlines the relative merits of eye structure examinations. The sensitivity and specificity measures are synthesised from Burr et al (2007). 70 National Health and Medical Research Council
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