Preparation before measurement
　　1. Clean the prism lens with a disinfectant that does not damage acrylic, rinse the end with distilled water, and then wipe it dry with a disinfected cotton swab.
　　2. Adjust the tonometer’s dial to the “1” mark.
　　3. Adjust the slit illumination to its maximum intensity, and set the filter to the cobalt‑blue filter.
　　4. The slit lamp and the microscope are positioned at an angle of 40° to 60° relative to each other.
　　5. Use 10× magnification for the microscope;
　　6. Apply 1% dicaine for topical ocular anesthesia, anesthetizing both eyes simultaneously to minimize blinking.
　　7. Place fluorescein paper or fluorescein solution in the conjunctival sac of the eye to be examined for ocular staining.
　　8. Place the patient’s mandible on the mandibular support and press the forehead firmly against the forehead support strap.
　　9. Ask the patient to open their eyes wide and look straight ahead; if necessary, gently pull the eyelids apart with your hand, but do not apply pressure to the eyeball.

　　Operation

　　1. When no target eye is present, if the slit lamp illuminates the Goldmann tonometer’s prismatic flattening head and the reflected light enters the slit lamp’s eyepiece, two concentric reflection rings—one above and one below—can be observed. During measurement, these rings remain constant; for convenience, they are referred to as the fixed reflection rings.

　　2. When the slit lamp is positioned at a distance and directed toward the target, two small reflected halos can be observed—one on each side horizontally. These are caused by the slit lamp’s illumination of the corneal surface, with the reflected light being refracted into the eyepiece; for now, they may be referred to as “moving reflected halos.”
　　                            
　　3. Then, slowly advance the slit lamp; through the slit lamp’s eyepiece, the corneal surface‑reflected slit‑lamp halo will gradually converge toward the center. The upper small halo moves toward the fixed halo above the horizontal line, while the lower small halo moves toward the fixed halo below the horizontal line.

　　4. When the small counter‑ring above is nearly aligned with the fixed counter‑ring above the horizontal line, and the small counter‑ring below is simultaneously approaching the fixed counter‑ring below the horizontal line, it indicates that the corneal surface is about to come into contact with the flattening head of the Goldmann applanation tonometer prism.
　　      
　　5. At this point, gently push the handle of the slit lamp, which is perpendicular to the operating table surface (note: apply gentle pressure to the top of the handle; do not push horizontally to avoid excessive displacement), and you will see two green semicircular rings appear.

　　6. At this point, keep the slit lamp stationary and slowly turn the pressure‑adjusting knob until the inner edges of the two semicircular rings just touch; then read the value from the scale drum.
　　                    
　　7. Repeat the above procedure three times; if the readings are essentially consistent each time, the measurement is considered accurate, and the average of the three readings is taken as the measured intraocular pressure.

　　8. After completing the measurement, use the slit-lamp control handle to promptly retract the tonometer from the patient’s cornea.
　　 
　　 
　　Guide to the Calibration of the Flat-Tip Tonometer

　　1. Remove the tonometer weights; both the weights and the base each weigh 2 grams.
　　 
　　2. Place the tonometer horizontally and position the weight holder within the prism’s lens mount.
　　 
　　3. Place a mirror on the side of the pressurized knob marked with graduations; the tonometer scale can be observed through the mirror.
　　 
　　4. Rotate the pressure knob to bring the balance lever into the balanced position.
　　 
　　5. Observe through the mirror to see whether the scale mark remains at “2”; an error of within one division is considered normal.
　　 
　　6. Add one weight, then continue adjusting the tonometer until it reaches equilibrium, and observe whether the scale mark remains at the “4” position. Sequentially add additional weights; if all measured readings are accurate, the tonometer is deemed to be precise.
　　 
　　7. If the tonometer scale is off and the deviation remains constant with each addition of weights, this indicates that the tonometer’s zero point is inaccurate. Unscrew the screw at the top of the pressure‑adjustment knob, loosen the scale knob, and adjust the instrument to a horizontal position. Once the balance lever has reached equilibrium, align the scale knob with the corresponding scale mark, secure it with adhesive tape, and then tighten the screw.
　　  
　　8. If the tonometer’s zero point is correct but the scale reading deviates when weights are added, this indicates a problem with the internal spring mechanism, and the tension must be adjusted by turning the screw at the base.