Effect of pharmacological pupil dilation on measurements and iol power calculation made using the new swept-source optical coherence tomography-based optical biometer

Purpose: to determine whether pupil dilation affects biometric measurements and intraocular lens (IOL) power calculation made using the new swept-source optical coherence tomography-based optical biometer (IOLMaster 700©; Carl Zeiss Meditec, Jena, Germany). Procedures: eighty-one eyes of 81 patients evaluated for cataract surgery were prospectively examined using the IOLMaster 700© before and after pupil dilation with tropicamide 1%. The measurements made were: axial length (AL), central corneal thickness (CCT), aqueous chamber depth (ACD), lens thickness (LT), mean keratometry (MK), white-to-white distance (WTW) and pupil diameter (PD). Holladay II and SRK/T formulas were used to calculate IOL power. Agreement between measurement modes (with and without dilation) was assessed through intraclass correlation coefficients (ICC) and Bland-Altman plots. Results: mean patient age was 75.17 ± 7.54 years (range: 57–92). Of the variables determined, CCT, ACD, LT and WTW varied significantly according to pupil dilation. Excellent intraobserver correlation was observed between measurements made before and after pupil dilation. Mean IOL power calculation using the Holladay 2 and SRK/T formulas were unmodified by pupil dilation. Conclusions: the use of pupil dilation produces statistical yet not clinically significant differences in some IOLMaster 700© measurements. However, it does not affect mean IOL power calculation.

Agreement and clinical comparison between a new swept-source optical coherence tomography-based optical biometer and an optical low-coherence reflectometry biometer

Purpose To compare measurements taken using a swept-source optical coherence tomography-based optical biometer (IOLmaster 700) and an optical low-coherence reflectometry biometer (Lenstar 900), and to determine the clinical impacts of differences in their measurements on intraocular lens (IOL) power predictions. Methods Eighty eyes of 80 patients scheduled to undergo cataract surgery were examined with both biometers. The measurements made using each device were axial length (AL), central corneal thickness (CCT), aqueous depth (AQD), lens thickness (LT), mean keratometry (MK), white-to-white distance (WTW), and pupil diameter (PD). Holladay 2 and SRK/T formulas were used to calculate IOL power. Differences in measurement between the two biometers were determined using the paired t-test. Agreement was assessed through intraclass correlation coefficients (ICC) and Bland–Altman plots. Results Mean patient age was 76.3±6.8 years (range 59–89). Using the Lenstar, AL and PD could not be measured in 12.5 and 5.25% of eyes, respectively, while IOLMaster 700 took all measurements in all eyes. The variables CCT, AQD, LT, and MK varied significantly between the two biometers. According to ICCs, correlation between measurements made with both devices was excellent except for WTW and PD. Using the SRK/T formula, IOL power prediction based on the data from the two devices were statistically different, but differences were not clinically significant. Conclusions No clinically relevant differences were detected between the biometers in terms of their measurements and IOL power predictions. Using the IOLMaster 700, it was easier to obtain biometric measurements in eyes with less transparent ocular media or longer AL.

Visual outcomes after bilateral trifocal diffractive intraocular lens implantation

Background In recent years new models of intraocular lenses are appearing on the market to reduce requirements for additional optical correction. The purpose of this study is to assess visual outcomes following bilateral cataract surgery and the implant of a FineVision® trifocal intraocular lens (IOL). Methods Prospective, nonrandomized, observational study. Vision was assessed in 44 eyes of 22 patients (mean age 68.4 ± 5.5 years) before and 3 months after surgery. Aberrations were determined using the Topcon KR-1 W wave-front analyzer. LogMAR visual acuity was measured at distance (corrected distance visual acuity, CDVA 4 m), intermediate (distance corrected intermediate visual acuity, DCIVA 60 cm) and near (distance corrected near visual acuity, DCNVA 40 cm). The Pelli-Robson letter chart and the CSV-1000 test were used to estimate contrast sensitivity (CS). Defocus curve testing was performed in photopic and mesopic conditions. Adverse photic phenomena were assessed using the Halo v1.0 program. Results Mean aberration values for a mesopic pupil diameter were: total HOA RMS: 0.41 ± 0.30 μm, coma: 0.32 ± 0.22 μm and spherical aberration: 0.21 ± 0.20 μm. Binocular logMAR measurements were: CDVA −0.05 ± 0.05, DCIVA 0.15 ± 0.10, and DCNVA 0.06 ± 0.10. Mean Pelli-Robson CS was 1.40 ± 0.14 log units. Mean CSV100 CS for the 4 frequencies examined (A: 3 cycles/degree (cpd), B: 6 cpd, C: 12 cpd, D: 18 cpd) were 1.64 ± 0.14, 1.77 ± 0.18, 1.44 ± 0.24 and 0.98 ± 0.24 log units, respectively. Significant differences were observed in defocus curves for photopic and mesopic conditions (p < 0.0001). A mean disturbance index of 0.28 ± 0.22 was obtained. Conclusions Bilateral FineVision IOL implant achieved a full range of adequate vision, satisfactory contrast sensitivity, and a lack of significant adverse photic phenomena. Trial registration Eudract Clinical Trials Registry Number: 2014-003266-2.

Phenomenological model of visual acuity

We propose in this work a model for describing visual acuity (VV) as a function of defocus and pupil diameter. Although the model is mainly based on geometrical optics, it also incorporates nongeometrical effects phenomenologically. Compared to similar visual acuity models, the proposed one considers the effect of astigmatism and the variability of best corrected VV among individuals; it also takes into account the accommodation and the “tolerance to defocus,” the latter through a phenomenological parameter. We have fitted the model to the VV data provided in the works of Holladay et al. and Peters, showing the ability of this model to accurately describe the variation of VV against blur and pupil diameter. We have also performed a comparison between the proposed model and others previously published in the literature. The model is mainly intended for use in the design of ophthalmic compensations, but it can also be useful in other fields such as visual ergonomics, design of visual tests, and optical instrumentation.