The Effect of Laser Treatment on Macular Pigment of Eye in Cases With Diabetes
Condition: Diabetic Retinopathy; Retinal Degeneration; Macula Abnormality; Laser Burn of Retina
MeSH terms: Retinal Diseases; Diabetic Retinopathy; Retinal Degeneration
Study type: Interventional

Summary: 
      It has been hypothesized that thermal damage of laser pan-retinal photocoagulation may affect
      macular pigment as well as inner layer cells in the retina, so it was aimed to investigate
      possible effect of conventional laser pan-retinal photocoagulation on macular pigment optical
      density in diabetic retinopathy patients without macular edema and pathology in this study.
    

Detailed description: 
      The local authorized clinical trials ethics committee approved the study and this study was
      performed following the principles of the Declaration of Helsinki (2008). Detailed
      information was given to patients about clinical applications and tests, and signed informed
      consent forms were also obtained from all patients. The 36 eyes of 36 patients, scheduled for
      laser pan-retinal photocoagulation treatment, with newly diagnosed proliferative diabetic
      retinopathy without macular edema or scarring between October 2015 - June 2016 were included
      in this sequential self-controlled clinical trial. Proliferative diabetic retinopathy was
      diagnosed with determination of neovascular proliferations is either on the disc (NVD) or
      elsewhere (NVE) except macular area in fundus examination with 90-diopter lens and fundus
      fluorescein angiography (FFA) (Heidelberg Spectralis, Heidelberg Engineering,
      Baden-Württemberg, Germany). Patients, detected macular fluid or edema by optical coherence
      tomography (OCT) (Cirrus HD 4000, Carl Zeis Meditec, CA, USA) in study eye, were excluded in
      the study. After providing information to patients about the disease and treatment; patients,
      predicted to show adherence to treatment, were enrolled in the study.

      Ophthalmological examinations were performed in all cases. Firstly, visual acuity was
      recorded, and best-corrected visual acuity (BCVA) assessed using Snellen's chart and was
      converted to logarithm of the minimum angle of resolution (logMAR) for statistical analysis.
      After maximal pupil dilatation was achieved using 1% tropicamide and 10% phenylephrine eye
      drops, put once or twice, at ten minute intervals, slit-lamp examination was performed, and
      fundus was examined with 90-diopter indirect non-contact fundus lens, and ocular finds were
      recorded.

      Prior to measurements the pupil was dilated to at least 7 mm diameter using a topical
      mydriatic agent. Macular pigment optical density (MPOD) levels were measured in the study eye
      using luminance differential thresholds test (MonPack System®, Metrovision, Perenchies,
      France), color perimetry technique at baseline before first PRP laser treatment and every
      month before laser treatment until the end of this study. The macular pigment absorbs blue
      light, and luminance differential thresholds test evaluates the density of the macular
      pigment by comparing the thresholds of perception of blue light and red light with a
      staircase technique similar to the technique used in automated perimetry. Luminance
      differential thresholds were measured for 2 stimuli: a blue stimulus (450-480 nm) absorbed by
      the MP, and a red one (615 nm) not absorbed. The stimuli were presented at the fovea and at 6
      peripheral locations with an eccentricity of 3 to 10 degrees (0°, 0.8°, 1.8°, 2.8° and 3.8°,
      and the average of two measurements at 6.8° and 7.8° retinal eccentricity serves as the
      peripheral reference point). Tests parameters were Goldmann size III over a white background
      of 10 cd.m-2. The average values of the tested (decibel=dB) were converted to logarithm units
      (log unit) for statistical analysis (dB = 10log10 (Reference1/Reference2)). Because, decibel
      is always the comparison between two values. As a result, the decibel number is the same,
      although the measured power value is often different. Therefore, arithmetic operations with
      the numbers expressed in decibels would be inconvenient.

      Conventional laser PRP treatments were performed under topical anesthesia by using green
      laser photocoagulator (GYC-500 Vixi® Nidek, Gamagori, Japan) and Volk® quadraspheric lens.
      PRP laser were applied in 300mW power, 200-400-500 μm spot size and 0.1-0.2 second pulse
      options, based upon preferences and comfort levels. When a pattern array was used, the spot
      separation was set at 0.5 times the burn width.

      Laser parameters were evaluated based on a) area (A) (= πr2 × number of shots) r being the
      spot radius, which is half of the spot size (100-200-250 μm), and it was converted to square
      millimeters (mm2) for statistical analyses, b) treatment duration (t) (= 0.1 - 0.2 second ×
      number of shots) and c) total energy (E) (= P × t) milijoules (mJ) P being the power, which
      is 300mW.

      All examinations, MPOD and laser PRP parameters were repeated and recorded at 1st, 2nd, 3rd
      month before laser treatments and 6th month. Changes in the eating habits of patients were
      questioned at all study visits. All subjects were told to continue their normal diet, as no
      subjects were consuming supplements containing lutein or zeaxanthin.
    

Intervention name(s): Laser pan-retinal photocoagulation
Intervention type(s): Device
Intervention description(s): Green laser photocoagulator
Other intervention name(s): GYC-500 Vixi
Intervention model: Sequential Assignment
Intervention model description: sequential self-controlled clinical trial
Masking: None (Open Label)
Primary purpose: Treatment
Keywords: macular pigment; macular pigment optical density; diabetic retinopathy; laser pan-retinal photocoagulation