Evaluation of posturing in macular hole surgery.

AIM: To objectively evaluate the postoperative face down posturing in macular hole surgery. MATERIALS AND METHODS: An electronic device called 'Maculog' was developed consisting of three basic components, a mercury switch triggered by the angle of tilt placed inside an earpiece, a data-recording device connected to the earpiece with cables and a windows based software program, specially written to analyse the recorded data in the form of tables and graphs. Ten patients undergoing macular hole surgery were fitted with the device on the first postoperative day before discharge. They were also asked for a subjective record of their posturing times. Four patients were given a posturing chair to take home. The device was retrieved after the first week and the data were downloaded to a PC for analysis. The actual posturing times recorded on the device were compared to the patients' own recollections. Results In all ten patients the actual posturing time was less than the time they had recorded themselves. The average actual posturing time was 48% of the perceived posturing time. The worst time for posturing, as expected, was between midnight and early morning. The compliance was better in patients who used the posturing chair. CONCLUSIONS: It is feasible to quantify the time of posturing using an electronic device and computer analysis. The study has shown that the actual posturing time is significantly less than the perceived posturing time. A further large study using 'Maculog' is now planned to correlate actual posturing time to the results of macular hole surgery.

Mechanical properties of metallic stents: how do these properties influence the choice of stent for specific lesions?

PURPOSE: To assess selected balloon-expandable and self-expanding stents for radial force, flexibility, radio-opacity, and trackability, and to relate these physical characteristics to potential indications for placement. METHODS: Force-strain curves were plotted for each stent and the force required to produce 50% luminal narrowing was recorded. The ability of the stent to show elastic recoil following deformation was also noted. Flexibility was measured by bending the stents against a force transducer and recording the force required per degree of flexion. Radio-opacity was measured by comparing each stent against a standard aluminum step wedge. Trackability was measured by testing the ability of the stent on its delivery system to track over angles of 90 degrees and 60 degrees. RESULTS: The balloon-expandable stents showed greater radial strength and radio-opacity but, apart from the AVE Iliac Bridge stent, showed poorer flexibility and trackability. The self-expanding stents showed less radial force but were able to re-expand following deformity. They were generally more flexible and had better trackability but lower radio-opacity. CONCLUSION: There is no stent which exhibits all the ideal properties required and therefore the interventionist will need to keep a range of stents available if all lesions are to be addressed.