The artificial intraocular lens imaging measuring instrument (IOL measuring instrument, such as the optical biometric instrument IOLMaster) is a professional equipment that accurately measures eye parameters such as axial length, corneal curvature, and anterior chamber depth through optical principles (such as low coherence interference and optical reflection), providing core data for calculating the degree of artificial intraocular lens in cataract surgery. The usage process must strictly follow the steps of "preoperative preparation patient cooperation parameter measurement data verification report output" to ensure measurement accuracy and surgical safety. The specific process is as follows:
1、 Preparation before use: equipment debugging and environment/patient preparation
1. Equipment and consumables preparation
Equipment startup and calibration:
Turn on the power of the IOL measuring instrument host, start the supporting software (such as the dedicated operating software of Zeiss IOLMaster), and wait for the device to self check (usually 1-3 minutes, check whether the optical system and sensors are normal);
Perform daily calibration using a standard calibration module (a calibration component that comes with the device and simulates standard axial length and corneal curvature): Align the calibration module with the measurement probe, click the "Calibrate" button in the software, and the device will automatically compare the measured value with the standard value. The error should be within the allowable range (such as axial length error ≤ 0.02mm, corneal curvature error ≤ 0.05D). If it exceeds the tolerance, contact the engineer for adjustment;
Check equipment accessories: Ensure that the measuring probe is clean (wipe the probe lens with a dust-free soft cloth to avoid fingerprints and dust affecting the optical path), and that the matching computer and printer are connected properly (for data storage and report printing).
Environment and patient preparation:
Environmental control: Turn off strong light in the measurement room (such as direct light from windows) to avoid interference from ambient light on optical measurements; Adjust the indoor temperature to 22-25 ℃ (excessive temperature fluctuations can affect the stability of optical components and lead to measurement errors);
Patient communication: Explain to the patient the purpose of the measurement ("selecting the appropriate intraocular lens power for surgery") and the key points of cooperation ("need to focus on the target point and keep the head still"), to alleviate the patient's nervousness;
Patient preparation: The patient takes a sitting position and adjusts the height of the measuring chair to make the patient's eyes roughly level with the center of the measuring probe (height difference ≤ 5cm, to avoid frequent adjustment of the probe position in the future); If the patient wears glasses/contact lenses, they should be removed in advance (contact lenses should be stopped for 1-2 hours to avoid changes in corneal morphology); Clean the oil and secretions around the patient's eyes with a physiological saline cotton swab (to avoid affecting corneal reflex signals).
2、 Patient positioning and parameter measurement: core steps to ensure patient cooperation and accurate data
Patient's head fixed and probe aligned
Guide the patient to place their chin on the chin rest of the device, with their forehead pressed against the forehead guard, and their hands naturally placed on their thighs (avoiding body shaking);
The operator adjusts the horizontal/vertical position of the measuring probe through the "observation window" of the device or real-time imaging software: aligning the center of the probe with the center of the patient's pupil ("pupil centered", which can be assisted by the "crosshair" in the software for positioning);
Adjust the chin rest height or probe lift button to keep the patient's eyes in a "comfortable gaze state" (avoiding deformation of the eye structure caused by the patient looking up or down, which affects the measurement of anterior chamber depth).
3、 Data validation and exception handling: eliminate errors to ensure data reliability
1. Data validity assessment
Check the "data quality indicators" of the software, such as the "signal intensity value" of the axial length of the eye (≥ 70%, below which indicates weak retinal reflex signal, possibly caused by cataract opacity or vitreous opacity), and the "integrity of the corneal curvature reflex ring" (≥ 8 complete rings are required, otherwise corneal data is unreliable);
Repeated measurement verification: Conduct 3 independent measurements of core parameters (such as axial length), take the average as the final result. If the difference between the 3 measurements is greater than 0.05mm (axial length) or greater than 0.1D (corneal curvature), investigate the cause (such as whether the patient is shaking or the probe is offset) and re measure;
Based on clinical experience, if the measured values are significantly abnormal (such as axial length<22mm or>26mm, corneal curvature>48D or<40D), the patient's medical history should be asked (such as whether they have high myopia or congenital glaucoma). If necessary, other devices (such as ultrasound biometric instruments) should be used for cross validation to avoid single device errors.
2. Common Exception Handling
Eye axis measurement failure (weak signal): If the patient has severe cataract opacity (lens nucleus hardness ≥ 4 levels) and near-infrared light cannot penetrate the lens to reach the retina, an "ultrasound biometric instrument" (contact or non-contact) should be used for measurement;
Large corneal curvature deviation: If the patient's cornea is irregular (such as in the early stage of keratoconus), the annular reflector ring will deform and need to switch to the "corneal topography mode" (supported by some IOL measuring instruments) to obtain more detailed corneal morphology data .....