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• Introduction
  
• Applications
  
• Retinal Pathology
  
• Pathology of the Vitreoretinal Interface
  
• Choroidal Pathology
  
• References
  
  
• Printable version (acrobat format)
  
• Standard Images
  

The optical reflectivity signal in optical coherence tomography (OCT) images exhibit high contrast between the non-reflective vitreous and the highly reflective internal limiting membrane. Similarly, there is high contrast at the interface between the minimally reflective photoreceptor layer and the highly reflective retinal pigment epithelium/choriocapillaris layer. These well-defined boundaries of the inner and outer neurosensory retina allow for retinal thickness measurement with OCT. In a study of central macular thickness using 20 eyes of 10 healthy volunteers (6 radial scans per eye) the mean foveal thickness (120 scans) was 147 ± 17 um (4). Central foveal thickness is considered abnormal (intraretinal edema present) when central foveal thickness measures greater than 185 um (greater than 3 standard deviations away from the mean for normal subjects) (4).

no evidence
questionable (<=185um)
definite (>185 um)
can't grade

center involvement

no evidence
questionable
definite

Round, minimally reflective (darker) spaces within the neurosensory retina represent intraretinal cysts. These intraretinal cysts often are not detectable on stereoscopic color fundus photography. These cysts are typically observed in the outer retinal layers and can vary in size. Small cysts are generally confined to the outer retinal layers while larger cysts may be observed to span nearly the entire thickness of the retina extending from the retinal pigment epithelium/choriocapillaris reflection to the highly reflective anterior boundary of the neurosensory retina. Cysts can range in number from one per scan to multiple. When intraretinal cysts are present in large numbers cystoid macular edema may be present on either/both stereoscopic fundus photography or fluorescein angiography.

no evidence
questionable
< standard case (std. case) 1A
< std. case 1B
>= std. case 1B
can't grade

center involvement

no evidence
questionable
definite

Subretinal fluid can be distinguished from intraretinal edema on OCT. Subretinal fluid appears as a non-reflective (dark) space between the posterior boundary of the neurosensory retina and the retinal pigment epithelium/choriocapillaris reflection. The retinal pigment epithelium/choriocapillaris reflection (red) is undisrupted and follows the contour of the globe. In distinction to intraretinal edema the non-reflective area is not present within the neurosensory retina. Additionally, the non-reflective space is not typically round. The non-reflective space corresponding the subretinal fluid is typically semicircular in shape with tapered lateral extensions (somewhat similar to the shape of a Bell curve). Numerous variations on this appearance may be present due to the presence of other abnormalities such as choroidal neovascularization and/or pigment epithelial detachments. The height of the neurosensory detachment can be quantified by measuring the distance between the posterior boundary of the neurosensory retina and the retinal pigment epithelium/choriocapillaris reflection. The neurosensory retina overlying the area of subretinal fluid is typically not thickened on OCT images except in cases where the subretinal fluid has been chronic.

no evidence
questionable
< std. case 2A
< std. case 2B
>= std. case 2B
can't grade

Center involvement

no evidence
questionable
definite

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