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Glaucoma Detecting Visual Field Progression in Glaucoma – Using the Right Tools for the Job Luke J Saunders, 1 Richard A Russell 2 and David P Crabb 3 1. PhD Student, Department of Optometry and Visual Science, City University London; 2. Post-doctoral Research Fellow, Department of Optometry and Visual Science, City University London and NIHR Biomedical Research Centre for Ophthalmology, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London; 3. Professor of Statistics and Vision Research, Department of Optometry and Visual Science, City University London Abstract Monitoring disease progression is at the centre of managing a patient with glaucoma. This article focuses specifically on how visual field measurements from standard automated perimetry (SAP) can be monitored over time. Various options for analysis on the Humphrey and Octopus perimeters are discussed, from summary indices to event and trend-based analyses; their respective merits and flaws evaluated. It is strongly recommended that quantitative analysis methods and software are used in assessing progression, as variability in threshold measurements makes detecting true deterioration non-trivial. Recommendations on the frequency of visual fields that should be taken per year are also discussed. The article concludes by putting the spotlight on new research being undertaken to improve the methods of measuring and predicting progression, as well as relating visual fields to patient visual disability and quality of life. Keywords Glaucoma, visual field, progression analysis, standard automated perimetry Disclosure: The authors have no conflicts of interest to declare. Received: 6 January 2012 Accepted: 23 March 2012 Citation: European Ophthalmic Review, 2013;7(1):20–6 Correspondence: David P Crabb, City University London, Northampton Square, London, EC1V 0HB. E: Glaucoma is a set of eye conditions in which the optic nerve head (ONH) and retinal ganglion cells are damaged, resulting in the visual field (VF) of the sufferer being reduced. Part of what makes glaucoma so dangerous is that the rate of VF impairment is typically slow and that it usually begins by affecting the peripheral vision of a sufferer. Consequently, many patients do not report the condition until very late when the amount of VF lost can seriously undermine their quality of life (e.g. by having their driving license revoked or being at increased risk of a fall). Naturally, most methods of glaucoma treatment involve reducing the intraocular pressure and this will require adapting based on the rate of disease progression, which makes monitoring VF progression very important. Information on VF progression is also used to assess whether a patient requires further intervention or not dependent on whether the condition is progressing quickly enough to have a tangible effect in their expected lifetime. 1 Furthermore, VF measurements (and intraocular pressure) are by and large the only accepted endpoints in evaluations of new therapies for glaucoma; the Advanced glaucoma intervention study (AGIS), Collaborative initial glaucoma treatment study (CIGTS) and Early manifest glaucoma trial (EMGT) being examples of major trials in which VF progression was the chief endpoint. This article will describe the most important current methods of assessing glaucomatous VF progression, comparing their strengths and weaknesses. In addition, practical advice concerning monitoring functional loss will be discussed and current research topics will be discussed. Measuring the Functional Progression of Glaucoma One of the most important methods of diagnosing glaucoma and monitoring its progression is through measuring the functional progression of the disease. Structural methods, looking at the health 20 of the ONH, can also be used but these are not the focus of this article. Perimetry is the means by which the VF of a patient is mapped and the only means of measuring functional progression. The Humphrey ® Field Analyzer (HFA; Carl Zeiss Meditec, Dublin, CA) and the Octopus (Haag- Streit, Köniz, Switzerland) are commonly used perimeters, especially in a tertiary or referral setting where the goal is to monitor VFs in patients with glaucoma or at risk of developing glaucoma, so this article will focus on using these instruments. Standard automated perimetry (SAP) has been the gold-standard to measure the VF since its introduction in the 1980s, but there are a number of other automated perimetry methods that have been developed to try and displace it, including short wavelength automated perimetry (SWAP), pulsar (or flicker perimetry) and frequency doubling perimetry (FDP or FDT). 2,3 However, research is still ongoing and, for now, SAP remains the primary method for detecting VF progression and is hence the subject of this article. As with structural methods, alternative functional methods are helpful to be used alongside rather than instead of SAP. 4 The full-threshold method to measure thresholds in SAP employs a ‘staircase’ technique. This method provides measurement of defect severity at each location in the VF but can take quite a long time (about 15 minutes per eye), during which it can be difficult to keep a patient’s attention. Thus, faster methods have been devised in order to reduce test time. One such technique for the HFA is the Swedish interactive threshold algorithm (SITA) Standard method. This strategy seeks to reduce test time by incorporating the knowledge that the threshold at each point is unlikely to be independent of neighbouring locations. 5 The large advantage of SITA Standard is that it can halve the duration of testing for many patients. An equivalent, though different, © Touch ME dical ME dia 2013