Mechanical testing of lid speculae and relationship to postoperative ptosis

Abstract

Aims Postoperative lid malpositions are known complications of routine intraocular surgery and were previously attributed to the use of a bridle suture or the myotoxic effect of retrobulbar or peribulbar anaesthetics. However, lid malpositions are still seen under topical anaesthesia. Recent studies have implicated the lid speculum as a factor. Patients with narrower vertical palpebral apertures have been shown to develop postoperative ptosis more frequently, but the reason is unknown. This is the first study to determine the forces exerted by lid speculae over a range of palpebral apertures. Methods Mechanical testing was undertaken using a Bose 3200 materials testing machine. Tests were undertaken on four disposable and four reusable speculae. The force used to compress each speculum was compared over a range of displacements. A two-sample t-test was used to compare the stiffness of the two types of speculum. Results The stiffness of the reusable speculum was significantly greater than the disposable speculum (P ¼ 0.002). The stiffness of each speculum was greatest at the range of displacement corresponding to the narrower palpebral apertures. Conclusions Different speculae exert significantly different forces on patients' eyelids during surgery. The patients who experience the greatest compression from the speculae are those with the smallest palpebral apertures. This may explain why these patients are more likely to develop postoperative lid malpositions.

Clinical efficacy of eyelid hygiene in blepharitis and meibomian gland dysfunction after cataract surgery: a randomized controlled pilot trial

“…Decreased corneal sensitivity causes decreased blinking rate 27 and incomplete blinking, which might contribute to MGD progression because meibum is delivered from meibomian glands by squeezing of the orbicularis oculi and Riolan muscles 28 – 31 . Third, the use of an eyelid speculum may induce eyelid dysfunction in early postoperative periods 32 , 33 to result in inappropriate blinking and squeezing force to deliver meibum from meibomian glands 9 , 12 . Fourth, increased ocular surface inflammation after cataract surgery may influence eyelid margins and meibomian gland function 10 , 12 .…”

Ptosis after glaucoma surgery

“…Ptosis and the type of lid speculum has been evaluated and believed to play a greater role in patients with smaller palpebral fissures. 12 Crosby et al 12 noted that a more rigid speculum can cause greater compression and greatest risk of eyelid malposition involving those with smallest palpebral apertures. Our study did not address the lid speculum secondary to lack of documentation regarding the type of speculum in close to two-thirds of the cases.…”

“…Crosby et al 12 had noted that, smaller palpebral fissures appear to play a role in ptosis and eyelid malposition. However, our study did not address whether patients had small or large palpebral fissures.…”

“… 11 Another theory is that the use of a lid speculum, stiffness of the lid speculum, and smaller palpebral fissures may play a greater role. 3 , 5 , 12 Crosby et al 12 have shown that the type of lid speculum can also affect the patients’ eyelids during surgery with the greatest compression forces on those with the smallest palpebral apertures.…”

Lower eyelid involutional entropion following cataract surgery

“…The eyelid speculum has been widely implicated by others as a potential contributor to post-operative ptosis [6,14,15]. As the speculum widens the palpebral aperture, in some patients it might actually place the levator complex and lower lid retractors under eccentric tension, particularly in narrower palpebral apertures [15] or if the vector forces are directed too anteriorly, too forcefully or for too long (Fig. 3a, b).…”