Article Text

Download PDFPDF
Original article
Do shapes and dimensions of scleral flap and sclerostomy influence aqueous outflow in trabeculectomy? A finite element simulation approach
  1. Kwong Ming Tse1,
  2. Heow Pueh Lee1,
  3. Noor Shabana2,
  4. Seng-Chee Loon2,
  5. Peter G Watson3,4,
  6. See Yin Lennard Harold Thean2
  1. 1Department of Mechanical Engineering, National University of Singapore, Singapore
  2. 2Department of Ophthalmology, National University Health System, Singapore
  3. 3Addenbrooke's University Hospital, Cambridge, UK
  4. 4Moorfields Eye Hospital, London, UK
  1. Correspondence to Kwong Ming Tse, Department of Mechanical Engineering, National University of Singapore, Applied Mechanics Lab, Department of Mechanical Engineering, National University of Singapore, Faculty of Engineering, 1 Engineering Drive 2, Singapore 117576, Singapore; tsekm.research{at}


Background/aim This study aimed to provide an objective assessment of the effects on the aqueous outflow rate of various geometries of the scleral flap and sclerostomy created in trabeculectomy.

Method Computer-based models and simulations of this surgical procedure were used to investigate the relative effects of various shapes and dimensions of scleral flap and sclerostomy on the aqueous outflow.

Result In these computer simulations, increasing scleral flap size was found to be associated with an increase of 48.55% in aqueous egress. In addition, a square scleral flap increased the aqueous drainage by 36.26% compared with a triangular flap of equivalent flap area. Surprisingly, our simulation results showed that a smaller semicircular sclerostomy improved aqueous drainage by up to 33.00%, while a semicircular sclerostomy, compared with a circular sclerostomy, led to a further 6.16% increase in aqueous outflow. Decreasing flap thickness beyond half-thickness caused an additional increase in aqueous outflow. However, clinically the flap should not be thinner than half the thickness of the sclera as this may result in hypotony.

Conclusion These simulations indicate that the optimal flow rate through operation site will be achieved in trabeculectomy using a square scleral flap with a large flap-to-sclerostomy ratio.

  • Trabeculectomy
  • scleral flap
  • sclerostomy
  • aqueous outflow
  • computer or finite element simulation
  • aqueous humour
  • glaucoma
  • sclera and episclera

Statistics from

Request Permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.


  • Competing interests None.

  • Provenance and peer review Not commissioned; externally peer reviewed.