Diabetes PRP and OCT
Condition: Proliferative Diabetic Retinopathy
MeSH terms: Retinal Diseases; Diabetic Retinopathy
Study type: Observational

Summary: 
      The purpose of this study is to evaluate the effectiveness of investigational Doppler Optical
      Coherence Tomography (OCT) and OCT angiography in the management of proliferative diabetic
      retinopathy (PDR - a leading cause of blindness in diabetic patients) before and after
      treatment. Angiography is the mapping of the blood vessels, and Doppler detects blood flow.
      PDR is due to poor oxygen circulation in smaller blood vessels in the back of the eye
      (retina), and is observed in 80% of people who have had diabetes for more than 10 years. This
      study will look at how blood flow to the eye is affected before and after treatment.
    

Detailed description: 
      Diabetic retinopathy (DR) refers to changes in the blood vessels of the retina associated
      with long-term diabetes mellitus. These changes can be found in patients both with Type I and
      II diabetes. DR is a leading cause of blindness in the United States. It is categorized as
      either non-proliferative (NPDR) or proliferative (PDR). In the PDR progress, the lack of
      oxygen in the retina causes fragile, new blood vessels to grow along the retina and in the
      clear, gel-like vitreous humour. Without timely treatment, the new vessels can bleed, cloud
      vision, and destroy the retina. So, the PDR is classified as either the existence of retinal
      neovascularization or vitreous or pre-retinal hemorrhage. PDR is typically treated with a
      laser, known as panretinal photocoagulation (PRP), which will create 1,600-2,000 burns in the
      retina to reduce the retinal oxygen demand, and then reduce the possibility of ischemia, or
      with an injection of an anti-vascular endothelial growth factor (anti-VEGF) drug into the
      vitreous, which always needs multiple injections. In cases of severe bleeding, a vitrectomy
      may be performed under local anesthesia. However, an eye patch and medicated eye drops are
      always needed after the operation to protect against infection and the outcomes are not
      always as good as expected.

      PDR is currently diagnosed by a comprehensive eye exam including a visual acuity test,
      ophthalmoscopy or fundus photography, fluorescein angiography (FA) and optical coherence
      tomography (OCT). If the PDR is thought to require treatment, the subsequent assessment of
      disease severity and treatment planning utilizes FA. FA requires the injection of sodium
      fluorescein into the systemic circulation. However, 1 in 3 people have adverse reactions to
      sodium fluorescein, which can include nausea, vomiting, hives, and acute hypotension. Severe
      reactions such as anaphylaxis and related anaphylactoid reactions, causing cardiac arrest and
      sudden death due to anaphylactic shock, have also been reported. Finally, because the risks
      of sodium fluorescein to a developing fetus are unknown, its use in pregnant women is
      contraindicated. Replacing FA with a less invasive and better tolerated method would reduce
      the risk in the patient population. One option is OCT angiography.

      Optical coherence tomography is an imaging technology that can perform non-contact
      cross-sectional imaging of tissue structure in real time. It has a number of features that
      make it attractive as a diagnostic imaging modality: 1) It has micron-level resolution, which
      is not possible with any other non-contact technique; 2) No potentially allergenic dyes or
      contrast agents are required; 3) OCT images are generated in electronic form, which
      facilitates the use of digital image processing techniques to extract quantitative parameters
      regarding the imaged tissue anatomy. For these reasons, structural OCT is already routinely
      used to assess the early stage of DR (NPDR) by imaging the areas of macular edema and
      response to treatment. Novel functional OCT including Doppler OCT and OCT angiography may
      allow an assessment of retinal blood flow and alleviate the need for the more invasive FA
      test. Thus, if the diagnostic data provided by functional OCT are at least equivalent or
      superior to those achieved by FA, patients and healthcare providers could realize a
      substantial benefit in utilizing this technology in the management of PDR and the evaluation
      of PRP.

      Therefore, we propose a pilot study to evaluate the feasibility of Doppler OCT to measure
      total retinal blood flow to assess global retinal ischemia after PRP treatment and OCT
      angiography of the retina to assess proliferative changes in the management of PDR subjects
      in comparison to standard FA. Functional OCT data (Doppler OCT and OCT angiography) are
      acquired using the Swept Source-OCT (SS-OCT) with a depth resolution of 5 microns and an
      ultrafast scan rate of 100 kHz which allows us to obtain detailed 3D OCT images. OCT
      angiography performs noninvasive microcirculation measurement and visualization which are not
      options on commercially available OCT systems. Though not FDA-approved, the SS-OCT prototype
      satisfies the American national standards for laser safety (ANSI) safety requirement. The
      power level is low enough to be classified as a non-significant risk device.
    

Observational model: Case-Only
Time perspective: Prospective
Sampling method: Probability Sample
Study population: 
        Individuals 18 years of age and older presenting to the Retina Service within the
        Department of Ophthalmology at the Casey Eye Institute of Oregon Health & Science
        University with signs and symptoms of PDR will be considered and evaluated for enrollment
        into this study. This pilot study has a planned enrollment target sample size of 28
        subjects needing PRP. However, up to 40 subjects will be recruited as it is possible that
        after subjects sign the consent form they may not meet all eligibility criteria.
      
Keywords: Diabetes; OCT; PDR