Mechanical testing of lid speculae and relationship to postoperative ptosis.

AbstractAims Postoperative lid malpositions areknown complications of routine intraocularsurgery and were previously attributed to theuse of a bridle suture or the myotoxic effect ofretrobulbarorperibulbar anaesthetics. However,lid malpositions are still seen under topicalanaesthesia. Recent studies have implicated thelid speculum as a factor. Patients with narrowervertical palpebral apertures have been shown todevelop postoperative ptosis more frequently,but the reason is unknown. This is the firststudy to determine the forces exerted by lidspeculae over a range of palpebral apertures.Methods Mechanical testing wasundertaken using a Bose 3200 materialstesting machine. Tests were undertaken onfour disposable and four reusable speculae.The force used to compress each speculumwas compared over a range of displacements.A two-sample t-test was used to compare thestiffness of the two types of speculum.Results The stiffness of the reusablespeculum was significantly greater than thedisposable speculum (P¼0.002). Thestiffness of each speculum was greatest at therange of displacement corresponding to thenarrower palpebral apertures.Conclusions Different speculae exertsignificantly different forces on patients’eyelids during surgery. The patients whoexperience the greatest compression from thespeculae are those with the smallestpalpebral apertures. This may explain whythese patients are more likely to developpostoperative lid malpositions.Eye (2013) 27, 1098–1101; doi:10.1038/eye.2013.133;published online 21 June 2013Keywords: blepharoptosis; ectropion; epiphora;postoperative complications; cataractextraction; speculumIntroductionPostoperative ptosis, ectropion, and epiphoraare frequently overlooked complications ofroutine intraocular surgery. Estimates of theincidence of postoperative ptosis vary from7.3% to 21% after cataract surgery,