The influence of low signal-to-noise ratio of axial length measurement on prediction of target refraction, achieved using IOLMaster

Abstract

Purpose To evaluate the influence of low signal-to-noise ratio (SNR) of axial length measurement, achieved using IOLMaster, on prediction of target refraction. Methods A total of 131 eyes of 131 patients who underwent phacoemulsification with posterior chamber lens implantation were enrolled. Preoperative axial length measurements were performed with the IOLMaster 500 (Carl Zeiss Meditec, Germany); preoperative SNR values were used to divide the eyes into three groups (Group 1; SNR <10, Group 2; 10 ≤ SNR <50, Group 3; 50 ≤ SNR <100). One month and 6 months after cataract surgery, the manifest refraction spherical equivalents (MRSE) were measured. The mean numeric errors (MNE), the mean of the difference between postoperative MRSE, and preoperative target refraction, using the various intraocular lens (IOL) formulas, were calculated and compared among the three groups. Results One month after cataract surgery, postoperative MRSE was more hyperopic than preoperative target refraction, calculated by the Haigis formula in group 1, and by the SRK/T formula in group 2. After 6 months, for all formulas in group 1, there were significantly hyperopic results (approximately 0.35 diopter). Upon comparison of MNE among the three groups, group 1 was statistically significantly different from the other groups by Haigis formula. Conclusions When the SNR values in biometry, using IOLMaster, are <10, careful attention should be given to determining IOL power, as postoperative spherical equivalents are more hyperopic than preoperative target refraction by IOL formula.

Use baseline axial length measurements in myopic patients to predict the control of myopia with and without atropine 0.01%

“…Fundus examination and AL (IOLMaster, Carl Zeiss Meditec) was performed. A high signal to noise ratio (individual signal to noise ratio greater than 2) is an essential measure of accuracy in each measurement [25]. The signal to noise ratio was high, often 200 to 500, with the only variable being fixation as no lens opacity was present in the participants.…”

The Repeatability of Axial Length Measurements Using a Scheimpflug-based System

“…The significant decrease in repeatability in individuals with nuclear cataract may be due to their denser lens opacity. [ 28 , 29 ] Moreover in this study, the small number of PSC cases may not have revealed any significant relationship between PSC cataract and axial length measurement repeatability.…”

“…[26,27] Moreover, other factors such as crystalline lens status and even the size of the AL may influence AL measurement. [28,29] It should be noted that the repeatability of the Pentacam's axial length measurements has not been addressed according to these variables in previous studies. Therefore, the present report aimed to determine the repeatability of the Pentacam AXL in measuring axial length based on age, sex, type of lens, axial length, and type of cataract.…”

“…[ 26 , 27 ] Moreover, other factors such as crystalline lens status and even the size of the AL may influence AL measurement. [ 28 , 29 ]…”

Comparison of Post-Operative Outcomes Predicted By Ultrasonic and Optic Biometry after Phacoemulsification

“…19 Similarly if signal to noise ratio using IOL Master are < 10, postoperative spherical equivalents are more hyperopic than preoperative target refraction by IOL formula. 20 Limitation of the current study is that we did not take astigmatism into consideration and we did not evaluate each method's accuracy in particular situations such as cataract type (posterior subcapsular, nuclear, or cortical), density of cataract, and refraction before cataract surgery (myopia, hyperopia, and emmetropia). The studies with bigger sample size might help to establish the superiority of optical biometry reported in certain studies.…”