[Macular hole surgery with air tamponade. Does air suffice for short-term tamponade?]. / Makulalochchirurgie mit Lufttamponade: Ist Luft als kurzzeitige Tamponade ausreichend?

BACKGROUND AND PURPOSE: We used a specially designed optical coherence tomography (OCT) device to investigate the dynamics of early macular hole closure after vitrectomy with air tamponade and to determine the closure rate and the briefest possible prone positioning. METHODS: A total of 112 patients with macular holes were examined using a modified spectral-domain OCT on days 1, 2 and 3 after vitrectomy with air tamponade. As soon as closure was complete (group one) or partial (hole closed at inner retinal layers but outer retinal layers still detached from pigment epithelial layer, group two), prone positioning was ended. If neither partial nor complete closure was observed by the third day, renewed vitrectomy was performed on postoperative days 4-8. RESULTS: Macular hole closure was achieved in 88 of the 112 eyes (79%). In 35 of the 88 eyes partial closure was noted on the first postoperative day. In 20 of the 24 eyes requiring renewed surgery the hole was finally closed. After a median follow-up of 144 days the macular hole was completely closed in all layers in 108 patients (96%). Mean visual acuity at final follow-up was 0.37 logMAR in group one, 0.29 logMAR in group two and 0.51 logMAR in patients whose holes closed after renewed surgery. Once closed, none of the macular holes reopened. CONCLUSIONS: The 79% initial closure rate in the present study is about 10% lower than that reported in other studies employing long-acting gas tamponades. However, renewed surgery with air tamponade achieved a closure rate of 96%. Early partial closure is sufficient for subsequent complete closure, requires no further tamponade or prolonged prone positioning, and has no negative effect on the functional results. Short-term prone positioning is sufficient for most patients.

In vitro genotoxicity and cytotoxicity of benzalkonium chloride.

Benzalkonium chloride (BAC) acts as a preservative in numerous nasal preparations. Possible genotoxic and cytotoxic effects of BAC in human respiratory epithelial BEAS-2B cells should be investigated in vitro. Cell cultures were exposed for 2h to BAC in concentrations ranging from 0.002% to 0.05%. Methyl methanesulfonate served as positive control, PBS as negative control. The tail moment of single-cell gel-electrophoresis (SCGE) was used to assess BAC-induced DNA damage. Cell viability was measured by trypan blue dye exclusion staining. Additionally, the critical micellar concentration (CMC) of BAC in PBS was detected. The tail moment increased dose dependently with the maximum value at 0.02%, and declined for higher concentrations. Nearly all cells died at low BAC concentrations up to 0.01%. Above this concentration cell viability increased. The CMC of BAC in PBS was estimated to be 0.02%. BAC caused relevant DNA changes in respiratory epithelial cells in vitro at concentrations commonly employed in commercially available nasal preparations. Some of the exposed cells survived. In further studies it could be considered to look whether these cells would still be able to proliferate and possibly fix the damage that they have possibly accumulated into an actual mutation using for example the induction of micronuclei.