Photographic Imaging of the Retina and Optic Nerve Head of Glaucoma Patients and Normal Controls
Condition: Glaucoma
MeSH terms: Glaucoma
Study type: Observational

Summary: 
      Retinal structures are difficult to visualize because the retina is optically transparent. In
      glaucoma, the microglia in the retina becomes activated in eyes with glaucomatous damage. The
      microglia forms a dense meshwork which resembles gliosis-like alterations, which may increase
      light scattering. With appropriate technology, increased reflection and light scattering from
      the retina may be detected in eyes of glaucoma patients.

      In this study, we investigate whether clinically observable retinal gliosis-like alterations
      occur more often in patients with glaucoma than in non-glaucomatous controls, and whether
      gliosis-like alterations are associated with a vasospastic propensity.
    

Detailed description: 
      Glaucoma is an optic neuropathy characterized by a progressive loss of retinal ganglion cells
      and cupping of the optic nerve head associated with visual function defects. Increased
      intraocular pressure and vascular alterations such as unsteady blood flow have been
      implicated in the pathogenesis of glaucoma. While glaucoma changes occur in both the retina
      and the optic nerve head, clinical diagnosis normally focuses on optic nerve head. However,
      histomorphologic and immunohistochemistry studies have shown that glial cells in the retina
      (astrocytes and Müller cells) are also activated in glaucoma. In addition, some patients with
      glaucoma have clinically patchy alteration in the retina resembling epiretinal gliosis but
      without visual disturbance, thus the term "gliosis-like alterations" was used previously. At
      present however, it is unknown whether gliosis-like alterations are associated with a
      specific type of glaucoma (i.e. high- or normal-tension glaucoma) or with vascular
      dysregulation. Moreover, it remains unclear whether gliosis-like alterations may also occur
      in the elderly patients without glaucoma as an aging process of the retina. Retinal
      structures are difficult to visualize and details difficult to be imaged on a photograph
      because the retina is optically transparent. Blue light scatters more than red light. This is
      the reason why the retinal nerve fiber layer can to some extent be better visualized with
      red-free light. The extensions of the astrocytes in the retina form a fine meshwork, which
      becomes denser and irregular as these astrocytes are activated. The size and numbers of glial
      cells increase, as the neural cell damage advances. These changes, in turn, may increase the
      light scattering. With appropriate technology, increased reflection and light scattering from
      the retina may be detected in the retina of glaucoma patients. The purpose of the study is to
      evaluate whether gliosis-like alterations do occur more often in glaucoma.

      The retina of patients and healthy controls alike will be photographically documented with a
      digital fundus camera as well as with optical coherence tomography and automated
      microperimetry that enables to correlate objectively local morphologic aspects and changes of
      the retina with local functional measurements. Possible causes for secondary retinal gliosis
      will be excluded in a thorough clinical examination including slit-lamp examination and
      dilated direct fundoscopy. The examination techniques and interventions used in this study
      are routine clinical practice and do not expose patients or controls to undue risk.
    

Observational model: Case-Only
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        patients with vascular dysregulation
      
Keywords: glaucoma; retinal gliosis-like alterations; optical coherence tomography; automated microperimetry