Eyeworld

JANUARY/FEBRUARY 2020 | EYEWORLD | 45 C Contact Castro-Alonso: franciscojcastroalonso@gmail.com correlated with anterior chamber and anterior segment depths, though less so than ICIP. Dr. Castro- Alonso noted that this work was per- formed in mostly medium eyes and added that the de- scription of this new variable opens the door to new studies that assess its use- fulness in short and long eyes. He said he hopes other research teams will validate ICIP with future studies. He envisioned that ICIP could be incorporated into multiple regression analysis-based formu- las to estimate final lens position, which could subsequently be used in a vergence formula for calculating IOL power. The report by Castro-Alonso et al. is not the first in recent years to put forth a new pa- rameter to potentially improve ELP estimates. In 2018, Yoo et al. described the lens equato- rial plane (LEP)—the distance from the front surface of the corneal to the crystalline lens equatorial plane—as a "promising measure" that could "serve as a new parameter to im- prove refractive outcomes in cataract surgery." 2 Castro-Alonso et al., comparing the mean value of ICIP (3.63 ± 0.35 mm) in their study group to the LEP described by Yoo et al., wrote that it was lower than the value obtained for LEP. "Therefore, the point corresponding to the intracrystalline lens interphase is located anteri- or to the LEP," Castro-Alonso et al. wrote. Another study published in 2018 described how information from the 3-D shape of the crystalline lens (obtained via OCT) was incor- porated into IOL power calculation formulas as a mode of improving effective lens position estimates as well. 3 (ICIP) served as a reference to increase or decrease the pow- er of the IOL as it was greater or lower than the average of the observed pop- ulation. With this modification of the power, I obtained a better postoperative refractive result than strictly applying the SRK/T formula." Dr. Castro- Alonso and coinves- tigators used optical low-coherence re- flectometry (LENSTAR LS 900, Haag-Streit) to determine the ICIP preoperatively. IOL powers were calculated with the LENSTAR system's EyeSuite, and implant power was selected ac- cording to SRK/T formula guidelines. 1 Patients received an AcrySof IQ aspheric SN60WF IOL (Alcon), enVista MX60 IOL (Bausch + Lomb), or CT Asphina 409M IOL (Carl Zeiss Meditec). Postoperatively, final lens position, IOL position error, postoperative anterior chamber depth, and thickness of the IOL were calculated. In total, 192 eyes from 174 patients were included in the study. Most eyes (88.5%) were 0.5 D or less from target. Final lens position was significantly correlated with preoperative measurements of axial length, anterior chamber depth, anterior segment depth, and ICIP. "In the current study, the potential predic- tive value to estimate the final position of the IOL in eyes undergoing cataract surgery was investigated for a new variable, the preoperative intracrystalline interphase point (ICIP) mea- sured with OCLR," Castro-Alonso et al. wrote. The ICIP was significantly correlated with final lens position (FLP, the distance between the corneal epithelium and anterior IOL surface) and FLP2 (the distance between the corneal epithelium and IOL's central plane) in the three groups. FLP and FLP2 were also References 1. Castro-Alonso FJ, et al. Predictive value of intracrystal- line interphase point measured by optical low-coherence reflectometry for the estimation of the anatomical position of an intraocular lens after cataract surgery. J Cataract Refract Surg. 2019;45:1294–1304. 2. Yoo YS, et al. Use of the crystalline lens equatorial plane as a new parameter for predicting postoperative intraocular lens position. Am J Ophthalmol. 2019;198:17–24. 3. Martinez-Enriquez E, et al. Esti- mation of intraocular lens position from full crystalline lens geome- try: towards a new generation of intraocular lens power calculation formulas. Sci Rep. 2018;8:9829. Relevant disclosures Castro-Alonso: None "Finding ocular parameters that help us estimate the final position of the intraocular lens after phaco refractive surgery is fundamental in the IOL power calculation." —Francisco Castro-Alonso, MD

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