Morphological and Functional Retinal Changes Following Retinal Photocoagulation
Condition: Proliferative Diabetic Retinopathy; Macular Edema
MeSH terms: Macular Edema; Retinal Diseases; Diabetic Retinopathy
Study type: Interventional
Phase: Phase 4

Summary: 
      Imaging of retinal morphological changes with time secondary to laser treatment as assessed
      with high definition optical coherence tomography (OCT). Furthermore changes in retinal
      function as an effect of treatment will be documented by visual acuity testing using ETDRS
      charts and microperimetry. The change in vascular leakage will be assessed by performing
      fluorescein angiography, flare counts will be performed monthly.
    

Detailed description: 
      Hypertension and diabetes are widespread diseases in our modern society and due to the
      comfortable, but often unhealthy "western world" lifestyle, the population suffering from its
      consequences is constantly growing. Vascular pathologies affect the body's entire vascular
      system subsequently including the circulation and vessels in the eye. For these reasons,
      after diabetic retinopathy and vein occlusions rank among the most common vascular disorders
      of the retina, with the highest incidence in a population over the age of 60. As to prevent
      severe vision loss due to complications induced by these angiopathies, panretinal or
      segmental laser coagulation is recommended as standard treatment of proliferative
      retinopathy. So far patients who undergo panretinal coagulation typically receive between
      1200 and 1500 lasers spots in two to four sessions over the course of 2 to 4 weeks. Clinical
      guidelines recommend not exceeding the number of more than 900 applied laser spots per
      session, due to the development of possible reversible exudative reaction e.g. macular edema.
      However, the performance of a panretinal photocoagulation is so far a time consuming
      procedure which is generally painful for the patient. For these reasons new laser systems
      were developed aiming to solve these obvious drawbacks. Main improvement of these systems is
      the reduction of the laser burn durations per spot and to enable therefore the rapid
      application of a large number of spots in a preset pattern. Treatment with reduced pulse
      duration is associated with less pain for the patient and, compared to several sessions
      requiring about 30 minutes each when using a conventional laser system, treatment time for a
      complete panretinal treatment could be significantly reduced. The PASCAL® Laser (Pattern Scan
      Laser, OptiMedica® Corporation, Santa Clara, CA, USA) is a new commercially available laser
      system confirming all these requirements.

      As the first study part (group I and II) we propose a controlled randomized comparison of
      single session to conventional multisession panretinal laser treatment, using the Pascal
      laser system for the single-session protocol and the Pascal laser system or the conventional
      laser system for the multi-session protocol. Development and regression of a retinal
      exudative reaction and the eventual onset of transient macular edema will be observed and
      documented. The morphological changes within the retina induced by laser burns will be imaged
      mainly using optical coherence tomography techniques. In regard to determine the lowest laser
      intensity as possible to produce a visible morphologic effect within small retinal areas
      different laser intensities will be used for photocoagulation of retinal segments to show the
      effect of a "sub-threshold" and gentle laser burn.

      As a second study part (group III), grid pattern laser coagulation will be performed in a
      conventional way using the Pascal laser system. In a small area of the retinal perifoveal
      zone showing macular edema, morphologic effects of photocoagulation using titrated low, sub
      threshold or threshold laser energy will be analyzed using OCT.
    

Intervention name(s): laser treatment with PASCAL®; laser treatment with PASCAL®; laser treatment with PASCAL®; laser treatment with conventional laser system
Intervention type(s): Procedure; Procedure; Procedure; Procedure
Intervention description(s): panretinal laser treatment - single-session; panretinal laser treatment - multi-session; grid / focal laser treatment; panretinal laser treatment - multi-session according to the conventional protocol, using a conventional laser system
Other intervention name(s): PASCAL® (Pattern Scan Laser, OptiMedica ® Corporation); The PASCAL® (Pattern Scan Laser, OptiMedica ® Corporation); PASCAL® (Pattern Scan Laser, OptiMedica ® Corporation)
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: None (Open Label)
Keywords: retinal morphology; laser treatment; pascal laser; HD-OCT