Additional information is provided in d.10., h.3., h.6.And h.10.Ocular synechia is an eye condition, where the iris adheres to either the cornea (i.E.Anterior synechia), or lens (i.E.Posterior synechia).Synechiae can be caused by ocular trauma, iritis, or iridocyclitis.It can also lead to certain types of glaucoma.It is sometimes visible on careful examination but usually more easily through an ophthalmoscope or slit-lamp.Anterior synechia causes closed angle glaucoma, which means that the iris closes the drainage way of aqueous humour, which in turn raises the intraocular pressure.Posterior synechia also cause glaucoma, but with a different mechanism.In posterior synechia, the iris adheres to the lens, blocking the flow of aqueous humor from the posterior chamber to the anterior chamber.This blocked drainage raises the intraocular pressure.Corneal thermal injuries are typically related to excessive heat generated by the phaco tip due to insufficient aspiration flow, extended energy application, or combination of both.The system is designed to cool the phaco tip during use as aspirated fluid flows through the tip lumen.Overheating of the phaco tip, however, may occur due to extended application of ultrasonic energy or compromised aspiration flow through the phaco tip.Reduced fluid flow through the phaco tip may be caused by phaco tip re-use, tip clogging by nuclear material, kinked tubing, inadequate flow and vacuum settings, or obstruction by ophthalmic viscoelastic device (ovd).When the phaco tip is occluded, infusion will cease, reducing the cooling effect of the tip.Occlusion tones (intermittent beeping tones during occlusion) alert the user, indicating that the vacuum is near or at its preset limit, and aspiration flow is reduced or stopped.The surgeon must recognize the occlusion tones and manually stop the ultrasound mode in order to prevent a rapid temperature increase.Corneal burn is an issue that is occasionally reported with cataract surgery.According to the pennsylvania patient safety advisory abstract: preventing corneal burns during phacoemulsification, march 2010, vol.7, no.1: 23-25, most corneal burns can be traced to issues related to surgical technique and not to malfunctioning equipment.A variety of intraoperative factors may lead to corneal edema following intraocular surgery.Patients who have preexisting endothelial pathological conditions (not limited to but including; fuch¿s corneal dystrophy, prior eye surgery, etc.) may be more likely to present with corneal edema.Acute corneal edema following cataract surgery usually fully resolves in the setting of a normally functioning endothelium, aided by an appropriate post-operative regimen.However, in some cases, corneal endothelial cells are damaged irreversibly, resulting in aphakic or pseudophakic bullous keratopathy.Corneal edema, from inadequate endothelial pump function, is one of the most common complications of cataract surgery.The possible contributions to a post-operative edematous cornea may include lack of sufficient ophthalmic viscoelastic device (ovd) used to protect the endothelium, excessive prolonged use of ultrasonic energy delivered by the phaco handpiece, inappropriate infusion sleeve orientation directing irrigation fluid directly against the corneal dome, aggressive iol insertion, instrument contact, or retained lens fragments.Several factors interact to ensure corneal transparency in the normal eye.The corneal stroma naturally imbibes water because of two forces: (1) the hydrophilic proteoglycans that exert an osmotic pressure to pull water into the stroma and (2) the intraocular pressure that drives water through the endothelial barrier.The corneal endothelium counteracts this response actively by dehydrating the stroma by acting as a pump, as well as passively through the integrity of the cellular membrane barrier.The epithelial cellular membrane also acts as a barrier.The endothelial barrier is leaky, but the leak rate normally equals the metabolic pump rate so that the endothelium maintains stromal water content to 78%.Corneal edema post-operatively is often times transient and resolves itself over time provided there is enough functional endothelium left.Other postoperative factors include elevated intraocular pressure (iop) or inflammation, which should be separately addressed if persistent.The main reason for persistent corneal edema is inadequate endothelial pump function keeping the corneal stroma in its relatively dehydrated and clear state.It is believed that at least 600 cells/mm2 are needed to provide adequate corneal dehydration, and clarity.Corneal edema after cataract surgery can be caused by various factors as mentioned above.There is insufficient information regarding the patient¿s ocular history and detailed events surrounding the occurrence.Ultrasonic power is a setting controlled and modified by the surgeon, therefore contributor to the event may be surgical technique as well as patient corneal pathology.The company service representative examined the system and no problems related to this event were found.The ultrasound (u/s) diathermy module was replaced as preventive measure.The system was then tested and met all product specifications.The system manufacturing device history record (dhr) was reviewed.Based on qa assessment, the product met specifications at the time of release.The root cause of the reported events cannot be determined conclusively.The manufacturer internal reference number is: (b)(4).
|