Variability in Perimetry Study
Condition: Glaucoma
MeSH terms: Glaucoma
Study type: Observational

Summary: 
      Improved Assessment of Visual Field Change is a trial aimed at investigating mechanisms of
      visual field testing variability. The investigators have found using larger stimulus size
      substantially lowers short-term variability. In this study, the investigators will determine
      if larger stimuli detect visual field change at an earlier time. The investigators are also
      developing a statistical model that accounts for correlations of neighboring test locations.
    

Detailed description: 
      Disease of the optic nerve, including glaucoma, is the leading cause of blindness in the
      United States. Treatment decisions for optic nerve diseases are based largely on the changes
      in visual function that occur mostly as a consequence of disease progression. Unfortunately,
      the decision as to whether change of visual function has occurred is often difficult because
      of the high retest variability of conventional visual field testing (perimetry). This
      variability is so high that with moderate visual loss, a minimum of six tests are often
      needed in patients with optic nerve damage to reliably distinguish visual field deterioration
      from random variation. The preliminary data show that a substantial portion of the
      variability of perimetry lies in the type of stimulus used and the testing strategy applied.

      OBJECTIVES: The investigators propose to test the hypothesis that a large portion of total
      perimetric variability in patients with visual loss is due to a poor signal-to-noise ratio
      associated with using a small fixed-size stimulus.

      RESEARCH PLAN AND METHODS: To test this hypothesis, the investigators are examining patients
      with optic nerve diseases with conventional automated perimetry (size III) and tests having
      large-sized and scaled stimuli (size V, size VI (custom perimeter) and luminance size
      threshold perimetry - a test where threshold is found by changing stimulus size rather than
      stimulus intensity). Over four years the investigators will test 100 patients with and
      glaucoma and 60 normals each eight times. In addition, the investigators are retesting 50
      subjects once a week for 5 weeks. The investigators are also studying the associated
      structural-functional correlations using OCT and developing a statistical model that accounts
      for correlations of neighboring test locations.

      Perimetric variability and the reliable identification of visual field change is the single
      most difficult problem in visual testing today. The investigators anticipate identifying a
      method that allows efficient and accurate determination of visual field change.
      Identification of a superior method would (1) reduce the number of examinations needed,
      thereby reducing the costs of medical care; (2) minimize misdiagnosis, unnecessary testing
      and even unnecessary surgery that results from mistakenly interpreting fluctuation of the
      visual field as progression or improvement; (3) allow earlier disease intervention and (4)
      reduce the costs of clinical trials.
    

Intervention name(s): Comparison of four visual field testing strategies
Intervention type(s): Procedure
Intervention description(s): We compared the ability of four perimetric strategies to detect visual field change in the glaucoma arm.
Observational model: Case-Control
Time perspective: Prospective
Sampling method: Probability Sample
Study population: 
        glaucoma patient with 0 to -25 dB mean deviation and normal subjects
      
Keywords: vision testing; perimetry; glaucoma; test variability