In this study, the biometric parameters measured by Revo NX biometer, Lenstar LS 900, and IOL Master 700, were compared in candidates presenting for cataract surgery. A good to a high agreement was found between devices, especially in the measurement of AL and CCT. The agreement of the IOL Master 700 and Lenstar LS 900 devices has also been previously investigated, and a high agreement between devices and no clinically relevant differences were found. 7,8
In the present study, the failure rate of IOL Master 700, Lenstar LS 900, and Revo NX OCT in measuring AL was 3%, 9%, and 18%, respectively. This is in keeping with previous studies showing that SS-OCT-based biometers, demonstrate greater penetration of the cataractous lens.13 Sikorski et al. also reported a higher failure rate of the SD-OCT Revo NX in measuring AL compared to the SS-OCT IOL Master 700 and proposed this to be due to the difference in OCT technology used by the Revo NX. 12
In the present study, AL measurements obtained by IOL Master 700 were marginally higher than the other devices, but the differences were not clinically and statistically significant. This is similar to the results reported by Kanclerz et al., comparing the same devices in healthy eyes.3 The authors found a high level of agreement (r value > 0.95) between Revo NX and IOL Master 700, and Lenstar LS 900 when measuring AL. Mean difference between − 0.001mm and 0.01 mm for AL measurement has been reported between Revo NX and IOL master 700. 3,12 In our study, the mean paired difference between AL measured by Revo NX and IOL Master 700 was − 0.02 mm. Moreover, mean difference of -0.02 mm was also found between Revo NX and lenstar LS 900 which is similar to the results of the study by Kanclerz at al,3,5 who found a mean difference of -0.002 to 0.11 mm when measuring AL in healthy eyes using Revo NX and Lenstar LS 900. Previous investigators have proposed a difference of 0.1 mm to be acceptable between AL measurements (almost equivalent to an error of about 0.27 D in intraocular lens power).14
In terms of CCT, a mean difference between Revo NX and IOL Master 700 of -2.29 µm (p < 0.05) was found. This is similar to previous studies reporting a mean difference between the two devices of -0.80 to -4.40 µm.3,12 The mean difference between Revo NX and Lenstar LS 900 was 0.73 µm which is consistent with other studies reporting a mean difference of between − 0.83 and 3.80 µm. 3,5 Although, differences in CCT measurements between these devices are not clinically significant, more difference in the measured CCT using Revo NX and IOL Master 700 has been justified with the several-fold smaller pixel size in Revo NX.12 The Optopol OCT Revo NX offers a resolution of 5 micrometers, which is more than four times better than the IOL Master 700 and enables it to define the boundaries of the layers of eye tissue more accurately. 12 Due to these capabilities, more accurate measurements can be made in the eyes with structural abnormalities or pathology. In this respect, the Revo NX surpasses the IOL Master 700 in measuring AL in irregularly structured eyes.12 More studies on the limitations and benefits of this device in comparison to other biometry systems are needed in patients with different cataract types and severities.
With respect to ACD, the mean difference of ACD measured with Revo NX and IOL Master 700 was 0.01 mm, and 0.10 mm as measured by the Revo NX and Lenstar LS 900. Other studies have reported a mean difference between 0.003 and 0.005 mm between Revo NX and IOL Master 700, and 0.01 to 0.05 mm between Revo NX and Lenstar LS 900.3,5,12 Depending on AL of the eye, a 0.25 mm error in ACD measurement results in a difference in IOL power between 0.50 to 1.0 D.15 Based on these findings, the differences in CCT measurements between the above platfroms are likely clinically insignificant.
Mean difference of LT between Revo NX and IOL Master 700 was − 0.15mm (p < 0.05), which is significantly more that previously reported (0.001–0.002 mm).3,5,12 The mean difference of LT measured with Revo NX and Lenstar LS 900 was 0.001 mm, and significanly less than similar studies which report a mean difference of between 0.008 and 0.03.3,5,12 The differences between our results and previous studies is likely related ot the fact that our study was performed on a cataractous group of patients. Dense lens and poor fixation may contribute to the ACD and LT measurment differences found in this study compared to previous studies. However, in the clinical practice, in IOL calculation formula which use LT parameter, a difference of 0.20 mm may change the IOL power by 0.20 dioper. 15 Based on these findings, statistically significant differences between Revo NX and IOL Master 700 may not considered clinically significant.
Previous studies show that Revo NX SD-OCT offers high repeatability and reproducibility in measuring ACDand LT in healthy eyes.5 It has been also reported to have a very strong correlation with the Lenstar LS 900 biometric measurements. However, AL and ACD measured with these devices were not considered interchangeable. 5 Similarly, we found a statistically and clinically significant difference between ACD measured with Revo NX and Lenstar LS 900 (0.10mm), but the AL measurement was in very good agreement. A newer version of Revo NX OCT was used in this study and there was a very good correlation between this device and IOL Master 700 in all measured biometric parameters (according to ICC). Also, narrower LoA was found between parameters measured using Revo NX and IOL Master 700 compared to the Revo NX and Lenstar LS 900. Strengths of the study include its prospective nature, the large number of eyes included and the inclusion of only eye per patient. However our study had a number of limitations including a lack of a healthy control group.
In conclusion, in eyes with cataract, despite the higher measurement failure rate, the Revo NX biometer showed very good agreement with the IOL Master 700 and Lenstar LS 900 validated optical biometers in measuring AL, ACD, LT, and CCT. However, ACD and LT measurements can not be considered interchangeable between these devices.