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Inside this issue: Issue 2 2018

 

Special Focus:  Optimal testing, technologies to detect glaucoma damage and progression

Authors: Linda Zangwill MD, Christopher Bowd, PhD
Hamilton Glaucoma Center and the Shiley Eye Institute, University of California San Diego, California USA

Core Concepts

  • There are 3 global indices of visual field sensitivity: mean deviation (MD), pattern standard deviation (PSD) and Visual Field Index (VFI). Once glaucoma has been diagnosed MD, PSD and VFI provide data on disease severity.
  • To be useful, tests must be reliable with few fixation losses and few false positive/false negative responses.
  • Data on disease severity with measured visual field deterioration, along with patient age and health status should be used to estimate likelihood of visual impairment.
  • Progression detection is facilitated using the Guided Progression Analysis (GPA) and Visual Field Index (VFI).
  • Frequency of follow-up testing should be dictated by the relative risk of progression. The higher the risk, the more frequently testing should take place.
  • The World Glaucoma Association Consensus Group on Glaucomatous Progression suggests at least 2 reliable fields in the first 6 months after diagnosis and at least 2 more fields within the next 18 months.
  • Increased testing from baseline up to 2 years identifies more rapidly progressing patients with a lower false positive rate.
  • It is important to evaluate the central visual field to obtain 10-2 visual fields that use a 2-degree spacing as it may be compromised even in early glaucoma.

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What’s New: Assessing function in Glaucoma                                                                                          

Author: Stuart Gardiner MD, PhD
Devers Eye Institute, Legacy Research Institute, Portland, Oregon, USA

Core Concepts

  • Standard automated perimetry has been the clinical standard of care in glaucoma for decades.
  • It is limited by excessively high variability, a limited dynamic range hampering both detection of early disease and the ability to monitor severe glaucoma, and poor patient acceptability.
  • Objective functional testing can outperform perimetry in certain cases, and is useful when other results are ambiguous. However no such techniques have yet been shown to consistently outperform perimetry, and so for now they remain supplementary rather than primary diagnostic tools.
  • New test stimuli are being developed that aim to improve the signal-to-noise ratio. In particular, flickering stimuli and alternative stimulus sizes show promise.
  • New testing algorithms aim to reduce test duration, and/or increase testing of the central region of the visual field where defects are commonly missed.
  • Portable visual field testing instruments are under development, in particular using tablet computers or using head-mounted screens. These would allow more frequent testing to be conducted, since they can be used outside clinical settings.

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Clinical Issues: Optimising Your Approach to Visual Field Testing

Author: Brennan Eadie MD, PhD, FRCSC, Marcelo Nicolela MD, PhD, FRCSC
Department of Ophthalmology & Visual Sciences, Dalhousie University


Core Concepts 

  • The gold standard visual field test for most patients with glaucoma, or suspected of having glaucoma,in most situations remains Standard Automated Perimetry (SAP) with, for example, the SITA Standard testing strategy using the 24-2 program on the Humphrey Field Analyzer (HFA).
  • The SITA FAST test strategy takes less time at the expense of greater variability making it acceptable for a first screening test, but suboptimal for routinely diagnosing and monitoring glaucoma.
  • Frequency Doubling Technology (FDT) and Short Wave-length Auto mated Perimetry (SWAP) should not be used routinely instead of SAP.
  • The 24-2 testing program remains preferable for most patients with glaucoma as it is faster than the 30-2 test pattern, and appears comparable for diagnosis and monitoring of glaucoma.
  • A 10-2 testing program should be considered even in early or suspected glaucoma because a 24-2 testing pattern may miss small paracentral visual field defects that can be detected with this test.
  • The 10-2 testing program is important for patients with visual field loss approaching fixation.
  • Consider switching to a size V stimulus in cases of severe visual field damage, particularly with decreased visual acuity.
  • In general, more frequent testing is recommended when patients are first diagnosed, in order to assess the rate of change within the first few years and to identify fast progressors (suggested six visual field tests in the first two years).
  • Cluster-based trend analysis may be more sensitive to focal visual field progression while maintaining a similar sensitivity to analysing global indices over time.
  • Choose thoughtfully the best visual field test, or combination of tests, and the frequency of testing, at every visit.

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Practical Tips: Minimising artifacts and avoiding pitfalls in visual field interpretation

Author: C. Gustavo De Moraes, MD, MPH
Columbia University Medical Center, New York, NY


Core Concepts

  • Make sure the correct date of birth has been entered.
  • Keep in mind the effects of pupil size and do not perform visual field tests under pharmacologic mydriasis.
  • Watch for ptosis and rim artifacts.
  • Ensure the optimal reliability indices for each individual patient and confirm consistency across their visual field sequences.
  • When assessing progression, reset the baseline tests based upon most recent changes in the treatment regimen.
  • Do not rely solely on summary statistics.
  • Perform 10-2 visual fields in patients with or suspected glaucoma.

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Our goal is to educate and update general ophthalmologists, glaucoma specialists and ophthalmology residents. Learn more about our publication, guidelines for authors and our editorial board.

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Ivan Goldberg MD, FRANZCO, FRACS, Sydney Eye Hospital, Sydney, NSW, Australia

Remo Susanna Jr MD, Department of Ophthalmology, University of São Paulo, São Paulo, Brazil


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