Laboratory Study
Eye (2007) 21, 402–407. doi:10.1038/sj.eye.6702253; published online 27 January 2006
Do scleral flap dimensions influence reliability of intraocular pressure control in experimental trabeculectomy?
Financial Support: This work was supported by the Capital Vision Research Trust
Proprietary interests: None
W Birchall1, A Bedggood1 and A P Wells2
- 1Wellington Hospital, Wellington, New Zealand
- 2Wellington School of Medicine, Wellington, New Zealand
Correspondence: W Birchall, Eye Department, Wellington Hospital, Riddiford Street, Wellington, New Zealand. Tel: +63 4 385 5999; Fax: +63 4 385 5470. E-mail: w.birchall@xtra.co.nz
Received 11 April 2005; Revised 1 November 2005; Accepted 6 December 2005; Published online 27 January 2006.
Abstract
Aim
To compare the effect on intraocular pressure (IOP) of large vssmall scleral flap size during trabeculectomy using adjustable sutures
Methods
Trabeculectomy operations were performed on nine donor human eyes connected to a constant flow infusion with real-time IOP monitoring. Large scleral flaps (4 
4 mm, 16 mm2, n=12) or small scleral flaps (3 2 mm, 6 mm2, n=9) were constructed over 0.76 mm2 sclerostomies. For each procedure, equilibrium IOP was measured following tight closure with two four-throw adjustable 10-0 nylon sutures.
Results
Five scleral flaps were thin or poorly constructed; four of these were in the initial seven procedures, implying learning effect. These had a mean absolute IOP of 7.6 mmHg (range 2.7–12.4 mmHg) and mean relative IOP of 28.3% of baseline (range 10–45.8%) after closure. In the remaining 16 good quality procedures, mean IOP was 1.3 mmHg (range 0–3.4 mmHg) after sclerostomy, confirming minimal outflow resistance before closure. Following flap closure mean IOP was 20 mmHg (SD 4.4, range 15.5–29.3 mmHg) for large (n=8), and 18.7 mmHg (SD 3.6, 15.9–25.8 mmHg) for small (n=8) flaps (unpaired t-test, P=0.26). Mean IOP (% baseline) was 71.6% (SD 8.4, range 60.6–86.6%) and 66% (SD=12.7, 46.8–86.6%) for large and small flap groups, respectively (unpaired t-test, P=0.2).
Conclusions
Well-constructed scleral flaps of both sizes were able to support an average IOP at least two-thirds of baseline, and both had similar absolute IOP levels. Errors in flap construction resulted in loss of IOP control. Smaller flap size does not appear to compromise control of early postoperative IOP using adjustable sutures.
Keywords:
glaucoma, trabeculectomy, surgical technique, adjustable sutures, experimental, intraocular pressure
