The macular hole formation takes place in the centre of the retina. A closure of the macular hole is believed to take place if the central retinal area is kept dry in the postoperative period. Therefore the eye is filled with a gas mix and the patients are urged to avoid the supine position in the first postoperative days. The investigators use the "tennis ball technique" where a tennis ball is fastened in the back of the night shirt in order to help patients compliance in avoiding the supine sleeping position. The investigators have developed a positioning measuring device which can measure the extent of supine positioning time. Patients are to sleep two nights with the positioning measuring device, one night with a tennis ball in the back of the night shirt and one night without. Hereby the investigators search new knowledge concerning patients compliance and verification of the "tennis ball technique".

Inclusion Criteria:

• Pars plana vitrectomy for macular hole, vitreomacular traction or epiretinal membrane where intra ocular gas tamponade is used.
• Informed consent

Exclusion Criteria:

• Age less than 18 years

Patients undergoing pars plana vitrectomy for macular hole formation, or conditions as epiretinal menbrane or vitreomacular traction where a macular hole formation is likely.