Quantification of Agreement and Variability of a Newly Developed Visual Field Algorithm With the Reference Standard
Condition: Glaucoma; Healthy
MeSH terms: Glaucoma
Study type: Observational

Summary: 
      This study aims to compare two types of visual field test; retinal sensitivity values
      obtained with the reference standard Swedish Interactive Thresholding Algorithm (SITA) of the
      standard visual field test and with a newly developed test algorithm. The new test is a
      visual field test presented on a flat-panel monitor and has two modes: differential light
      sensitivity (DLS; equivalent to the standard visual field test) and the Moorfields Motion
      Displacement Test (MMDT). DLS sensitivity and DLS measurement variability will be determined
      and compared between the SITA algorithm of the standard visual field test and the new visual
      field test on the flat-panel monitor. The measurement variability of the MMDT will be
      quantified.

      The long-term goal is to reduce test variability below that observed in SITA by 20%, whilst
      producing comparable measurements (contrast threshold values) for comparable test duration.
    

Detailed description: 
      Standard Automated Perimetry (SAP) is currently the standard test for screening and
      monitoring visual loss owing to glaucoma. This test requires the patient to sit at a machine,
      looking at a central light and pressing a button whenever small spots of light appear in the
      peripheral vision. Traditionally these spots of light are projected into a bowl (concave
      surface), but more recently, computer monitors have been used. Other techniques are also now
      available such as the Moorfields Motion Displacement Test, where patients are required to
      press a button each time they see a vertical line on the screen wiggle. This test has been
      shown to have advantages over SAP, namely, to be tolerant to the effects of cataract and
      refractive error.

      In clinical settings, the Humphrey Visual Field Analyzer (Zeiss Meditec) is the most used
      visual field test in the UK. It employs a SAP strategy coupled with the Swedish Interactive
      Thresholding Algorithm (SITA), which is used to derive retinal sensitivity. Visual field
      measurements are very variable, requiring many tests over a long period to determine the
      extent of vision loss. In addition to the inconvenience caused to patients, the contribution
      of these many tests to the financial burden on the NHS is increasing with the growing aging
      population. As glaucoma is a chronic disease, patients need lifelong monitoring, requiring
      multiple tests and clinic visits. To address these unmet needs, the investigators have
      developed a new algorithm that can be used to monitor glaucoma.

      The investigators wish to carry out a study, which will allow them to compare agreement
      between SITA and a newly developed test algorithm. Measurement variability will be determined
      and compared between strategies. The long-term goal is to reduce test variability and the
      test time observed in SITA, whilst producing comparable contrast threshold values.
    

Intervention name(s): New visual field algorithm with DLS; SITA algorithm; New visual field algorithm with MMDT
Intervention type(s): Device; Device; Device
Intervention description(s): Mathematical model (software based) to derive retinal sensitivity.; Mathematical model (software based) to derive retinal sensitivity. Commercially available.; Mathematical model (software based) to derive retinal sensitivity.
Observational model: Cohort
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        Participants will be recruited using three methods:

          1. The volunteer database of the Glaucoma Research Unit. Letters will be sent to
             patients/healthy controls, who in the past agreed to be contacted for research
             purposes. Written information about the project will be sent with the letters.

          2. Records screening. Patients' records will be screened in advance or during their
             clinical appointment. Persons identified as meeting the inclusion criteria will be
             invited to join the study, whereupon written information about the project will be
             given to the patient. Patients will be invited to join the study by letter, prior to
             their clinical appointment or in person on the day of the appointment.

          3. Invitation of accompanying persons and staff. It is anticipated that spouses and
             acquaintances of existing subjects, as well as staff at the research site, Moorfields
             Eye Hospital and UCL Institute of Ophthalmology, may offer their participation as
             healthy volunteers.