The completed questionnaire was review by an alcon clinical analyst, who stated the following: ¿the customer reported that the diagnostic system was set to immersion mode instead of contact mode.The staff did not notice this and the wrong intraocular lens (iol) was implanted causing a refractive error.The contact mode is used within the department.Therefore the wrong power iol calculated and inserted during left cataract surgery.The surgeon completed a questionnaire and noted the female patient of (b)(6) years of age.The surgery was on the left eye (os).The a-scan was completed.The surgeon noted another ophthalmology consultant was reviewing the a-scan intraocular lens (iol) calculation for a different patient to be operated on the same day.The immersion setting was first identified.The patient was not hospitalized.No medications or therapies were in use at the time of the event.No unplanned medical intervention has been completed.In the surgeon¿s opinion the device caused/contributed to the event.The patient¿s pre-existing ocular and medical conditions include bilateral dermatochalasis with punctual eversion, asthma, hypertension, arthritis, hypercholesterolemia, and rhinitis.The outcome of the event is noted as continues/not resolved as the patient is still under review post-surgery.This error was not noted until 30 days after the initial cataract extraction with iol implant.An additional procedure of implanting a "piggyback" iol was performed to provide a refractive balance between eyes.The measurement of axial length measurement has the greatest potential for error in calculating iol power.Traditionally, contact a-scan ultrasonography is used.This measures the time taken for sound to traverse the eye and converts it to a linear value using a velocity formula.Part of the ultrasound beam reflects back from each surface in the eye ¿ cornea, anterior lens, posterior lens, and retina.The reflected beam is translated into an image showing lines (spikes) for each surface.The distance between the corneal and retinal spikes gives the axial length of the eye.The alignment of the a-scan is vitally important.If the alignment is incorrect, the length of the eye will be underestimated.Most systems rely on the patient fixing on a target ¿ usually a light in the probe.Patients with poor vision, whether from cataract or from some other pathology, are less likely to fixate accurately, and are more prone to biometry errors.Tips for accurate measurement of axial length (using applanation): ensure the machine is calibrated and set for the correct velocity setting (e.G.Cataract, aphakia, pseudophakia); the echoes from cornea, anterior lens, posterior lens, and retina should be present and of good amplitude; misalignment along the optic nerve is recognized by an absent scleral spike; the gain should be set at the lowest level at which a good reading is obtained; take care with axial alignment, especially with a hand-held probe and a moving patient (as described above); don't push too hard ¿ corneal compression commonly causes errors; errors may arise from an insufficient or greasy corneal meniscus due to ointment or methylcellulose used previously.Extremely dense cataracts create difficulties, as they absorb sound as it passes through the lens.A higher gain setting may be necessary to achieve adequate spikes.Posterior staphylomata in myopic eyes not only cause an elongated globe, but often tilt the macula as well so that the ultrasound beam is deflected.There are known reasons for biometry errors include: people in a hurry, lack of training or accessible guidelines, reliance on others, technical failure (rarely), and human error (often).Some common mistakes that may result in unexpected refractive outcome include: wrong a-constant selected, wrong formula used, wrong k-readings entered by hand (90 degrees out), biometry print-out stuck in wrong patient's notes, wrong patient in theatre, reversed iol optic, or wrong iol implanted.The operators manual includes the warning: ensure that the correct technique (contact or immersion) is selected for the technique being performed.Incorrect technique selection will impact the accuracy of the results.Contact - in the contact technique, readings are obtained by placing the biometry probe directly on the patient¿s cornea.Immersion - in the immersion technique, an immersion shell containing the probe is placed on the patient's eye and filled with solution between the probe and the cornea.Since the probe is not touching the cornea, there is an offset on the display between the peak from the probe tip and the peak from the cornea.¿ product evaluation the customer stated that the system was in the incorrect immersion mode instead of being in the correct contact mode.Based on qa assessment, the product met specifications at the time of release.The root cause of the reported event can be attributed to customer mis-use of system by using the incorrect immersion mode instead of the correct contact mode when performing the measurements.The manufacturer internal reference number is: (b)(4).
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