Choroidal Thickness in Myopes by SSOCT
Condition: ESRD
Study type: Observational

Summary: 
      Optical coherence tomography is a non-invasive and non-contact imaging modality that enables
      two-dimensional cross-sectional and three-dimensional volumetric imaging of tissue
      architecture.
    

Detailed description: 
      It has evolved over the past decade as one of the most important ancillary tests in
      ophthalmic practice. It is a noninvasive imaging technique and provides high resolution,
      cross-sectional images of the retina, the retinal nerve fiber layer and the optic nerve head.
      With axial resolution in the 5-7 μm range, it provides close to an in-vivo 'optical biopsy'
      of the retina. Optical coherence tomography employs light from a broadband light source,
      which is divided into a reference and a sample beam, to obtain a reflectivity versus depth
      profile of the retina. The light waves that are back scattered from the retina, interfere
      with the reference beam, and this interference pattern is used to measure the light echoes
      versus the depth profile of the tissue in vivo.

      Recently, a new type of optical coherence tomography instrument, called a swept source
      optical coherence tomography, was introduced. The Swept source optical coherence tomography
      uses a tunable laser (swept-source) as a light source with a longer wavelength that allows
      the light to penetrate deeper into tissues than the conventional spectral domain optical
      coherence tomography instruments. This, then, enabled the imaging of the choroid.

      Because choroidal abnormalities such as vascular hyperpermeability, vascular changes, loss
      and thinning are critical to the onset and progression of many ocular diseases,
      ophthalmologists and researchers are shifting their interest to the choroidal abnormalities.

      Being a major vascular layer of the eye , choroid plays an important role in ocular health,
      and is involved in the pathogenesis of many intraocular diseases such as age-related macular
      degeneration , polypoidal choroidal vasculopathy , central serous chorioretinopathy and
      myopic macular degeneration. Accurate measurement of choroidal thickness in vivo is an
      essential step in monitoring disease onset and progression that lead to choroidal thinning.
      Based on histologic study, choroidal thickness ranges from 170 to 220 um.

      These disorders show the need for understanding the choroidal structure in ocular diseases
      and the importance of having database of choroidal thickness.
    

Intervention name(s): Swept source optical coherence tomography
Intervention type(s): Device
Intervention description(s): Measurement of choroidal thickness in myopic patients
Observational model: Cohort
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        100 case of age from 18 to 40 years old of myopic refraction from zero to -8 diopter ,
        minimum corneal thickness from 500 to 540 micrometer , refractive power of cornea more than
        41 diopter and axial length from 22 to 26 millimeter