Comparison of Local Made and Imported Porous Polyethylene Orbital Implant for Enucleation in Thailand

• Exposure rate [ Time Frame: From date of surgery until the date of first exposure, assessed up to 12 months ]
  Exposure was defined as the separation of tissue over the anterior surface of an implant.
  
  

• Infection rate [ Time Frame: From date of surgery until the date of first infection, assessed up to 12 months ]
  Infection was defined as the presence of pus or abscess at or around an implant. It can be diagnosed clinically or confirmed by the histopathology report after explantation.
  
  
• Motility [ Time Frame: 2,3,6,9,12 months post surgery ]
  Motility was defined as the distance in millimeters the patients can move their eyes in abduction, adduction, supraduction and infraduction. The rulers will be attached to the slit lamp in horizontal and vertical axis.The observer then take a photo of patients in 4 directions, with and without prosthesis. Two independent observers will measure motilities from the photographs. If the difference from two independent observers is more than 2 standard deviation, the measurement process will be started again.
  
  
• Gadolinium enhancement [ Time Frame: 6, 12 months post surgery ]
  Gadolinium uptake from MRI orbit represents implant vascularization. They will be taken in axial, coronal and sagittal plane with standard protocol MRI study. In T1-weighted post contrast image, an equatorial image will be identified. The equatorial image was defined as the image at the level of implant size divided by two, measured from the anterior surface. Two independent observer will mark between contrast and non-contrast area. Then area of enhancement was calculated by subtracting non-enhancement area from total equatorial surface area.
  
  

Sample size assessment

• The sample size was calculated by using an equivalence formula. From a literature and our own experiences, the success rate for Medpor and 3DP were 92% and 94% respectively, the difference (D) of the success rate between two groups was 10% and assuming a 15% of drop out rate.
• Then allocation sequence was generated by a computerized program, using block of six with varying block size.

Data management

• All definition of data, recruiting techniques, data collection techniques and data management flow were mentioned in the SOP.
• After double entry technique, each case record form from each site will be sent via DataFax system to the data center at Center of Excellence for Biomedical and Public Health Informatics (BIOPHICS), Thailand.
• Then data will be validated, analyzed and reported by staff at BIOPHICS.

Plan for missing data

• by adding a drop out rate to the sample size calculation.
• by choosing the right patients. Actually, Thai patients have good co-operation especially in surgical research.

Statistical analysis

- Intention to treat and per protocol model would be used to see the difference between two types of implants in this project.