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AIM: To observe the changes in the Chang-Warning chord(CW chord)before and after cataract surgery using the IOL Master 700 and predict the CW chord using an artificial intelligence prediction model and preoperative measurement data.METHODS: The analysis was conducted on the preoperative and postoperative IOL Master 700 measurements of 304 cataract patients. This included astigmatism vector value, average keratometry, axial length, anterior chamber depth, lens thickness, corneal central thickness, white-to-white, the position of the Purkinje reflex I image relative to the corneal center and pupil center, and the CW chord. A prediction model based on the SVR algorithm and the BP neural network algorithm was established to predict the postoperative CW chord using the preoperative CW chord and ocular biological parameters.RESULTS: The X component of the CW chord showed a slight shift in the temporal direction in both the left and right eyes after cataract surgery, while the Y component changed little. The SVR model, using the preoperative CW chord and other preoperative biometric parameters as input data, was able to predict the X and Y components of the CW chord more accurately than the BP neural network.CONCLUSION: The CW chord can be directly measured with a coaxial fixation light using various biometers, corneal topographers, or tomographers. The use of the SVR algorithm can accurately predict the postoperative CW chord before cataract surgery.
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@#AIM: To explore the dynamic distribution of pupil size and center, the eccentricity distribution of corneal light reflection, and its correlation analysis about suitable for femtosecond laser combined with excimer laser <i>in situ</i> keratomileusis.<p>METHODS: Randomly selected 225 patients(407 eyes)who underwent femtosecond laser combined with excimer laser <i>in situ</i> keratomileusis at Yanbian University Hospital in 2019 from January to May, preoperative use of Wavelight Allegro Topolyzer Corneal Topography to measure the pupil size and center position, the German Wavelight EX500 excimer Laser(500Hz)records the deviation between the pupil center and the coaxially sighted corneal light reflex when the patient is supine. <p>RESULTS:The average displacement distribution between the center of the cornea and the center of the pupil is 0.322±0.194mm, and 64% of the eyes are ≤0.40mm. The average displacement distribution of P-Dist(the eccentricity between the pupil center and the coaxially sighted corneal light reflex point)is 0.225±0.102mm, and 80% of the eyes are ≤0.30mm. The coaxially sighted corneal light reflex point is mainly deviated to the superior temporal side of the corneal center(34%). The X-axis of the left eye in low light conditions: -0.061±0.084mm, and the X-axis of the right eye: -0.016±0.059mm(<i>P</i>=0.002)(the left eye shifted to the temporal side in the dark light). The corneal transverse diameter(WTW)was positively correlated with changes in pupil diameter(dark pupil diameter-bright pupil diameter)(<i>r</i>=0.270, <i>P</i><0.001).<p>CONCLUSION: The left eye should be adjusted to a position of the machining center within 0.061mm. If the cornea is too large, try to maintain a dark light environment during the operation to improve the efficiency of pupil matching. This study further confirms the necessity of rationally positioning the cutting center under different angle kappa states.
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@#AIM: To investigate the repeatability and agreement of Pentacam Front Section Analyzer and Keratron Scout Corneal Topographer in measuring Kappa angle.<p>METHODS: Totally 69 patients were randomly selected from Ophthalmology Department of Leshan People's Hospital. Three readings were taken by the same examiner. Results were recorded in(<i>X</i>, <i>Y</i>)coordinates format and assessed by intraclass correlation coefficient(ICC), Cronbach's Alpha Coefficient, <i>t-</i>test, Pearson correlation analysis and bland-altman analysis.<p>RESULTS: Both instruments showed excellent repeatability in Kappa angle assessment. The results significantly correlated(<i>X</i> value: <i>r</i>=0.90,<i> P</i><0.01; <i>Y</i> value: <i>r</i>=0.91, <i>P</i><0.01), however, no significant difference were found between the two instruments. The widest 95% LoA was -0.11-0.14mm for <i>X</i> coordinate and -0.10-0.11mm for <i>Y</i>.<p>CONCLUSION: Pentacam and Keratron Scout showed excellent repeatability and agreement in Kappa angle assessment. The two instruments could aid and verify each other.