Utility of Heidelberg Retina Tomograph in Monitoring Glaucoma Progression
Condition: Glaucoma; Ocular Hypertension
MeSH terms: Glaucoma; Ocular Hypertension
Study type: Observational

Summary: 
      Glaucoma is a chronic disease defined by characteristic changes in the optic nerve associated
      initially with loss of peripheral vision and is treated by lowering intraocular (inside the
      eye) pressure. It has been reported that noticeable changes to the optic nerve caused by
      glaucoma may occur several years before changes in vision are noticed. Since changes to the
      optic nerve and other eye structures due to glaucoma are irreversible, it is important to
      develop tools for the earliest possible detection of changes due to glaucoma.

      The Heidelberg Retina Tomograph (HRT) is a device that is used to produce a three-dimensional
      map of the optic nerve and retina, and can be used to detect changes in the optic nerve and
      retina over time. In previous studies, it has been shown to be useful for the detection of
      changes due to glaucoma. However, the HRT when compared to other techniques to evaluate the
      optic nerve such as stereophotography, was found to only somewhat agree.

      The current study will compare HRT to stereophotography to determine how good each one is at
      looking and documenting changes in the optic nerve over time due to glaucoma. Using HRT to
      initiate early topical medication or to change management requires knowing how well HRT
      results predict the development of visual loss. Accordingly, the results of this study may
      affect the management of glaucoma patients by optimizing the follow-up of people with this
      condition and by initiating appropriate and more individualized treatments. Early treatment
      is crucial for preventing further visual loss in patients with glaucoma or ocular
      hypertension (high pressure inside the eye).
    

Detailed description: 
      In glaucoma, treatment decisions depend on the development of morphologic and functional
      damage. Therefore, damage serves as an indicator of management. Commonly, progression is
      determined by various perimetric techniques.

      However, it has been reported that clinically detectable glaucomatous structural alteration
      of the ONH may precede the development of reproducible white on white and blue on yellow
      visual field defects by up to several years.

      The HRT is a confocal scanning laser tomography device that creates a three-dimensional
      topographic analysis of the ONH and the peripapillary retina and includes a statistical
      analysis to evaluate structural change over time.

      This technique showed good sensitivity and high specificity in detecting glaucoma progression
      when tested using computer simulation. The same good results were obtained by the same
      authors, in another study, in a small subgroup of 16 patients who were monitored for
      glaucomatous progression by both HRT and ONH stereophotographs for approximately 5.5 years.

      However, in our recent retrospective study, our results demonstrated only fair agreement
      between HRT and clinical judgment of ONH stereophotographs for progression in glaucoma, for a
      mean follow-up time with HRT of 2.62 years. Although, the evaluation of the ONH
      stereophotographs is necessarily subjective, it is widely accepted and has been shown to be
      effective for evaluating change. Using the stereophotographs assessments as the "reference
      standard", the HRT sensitivity was 78% and the specificity to 70%. The positive predictive
      value of the HRT was 47.8%, while the negative predictive value was 90.3%.

      According to the results of this study if the frequency of true positives and false positives
      does not change with longer follow-up, treatment decisions would be based on a test that may
      be in error 52.2% of the time.

      Accordingly, our previous - and other studies - study demonstrated only fair agreement
      between HRT and clinical judgment of ONH stereophotographs for progression in glaucoma. At
      present, the available evidence does not appear to be sufficient to show that the addition of
      HRT improves the ability to predict the development of clinical optic disc change and/or
      visual field loss.

      Therefore the aim of the current study is to investigate the clinical significance of the HRT
      in monitoring glaucoma progression. In other words we will investigate how well HRT results
      for glaucomatous progression are able to predict the future development of optic disc and/or
      visual field changes in patients with OHT and glaucoma.
    

Observational model: Cohort
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        University glaucoma unit