A Comparison of Higher Order Aberrations Following Implantation of Four Foldable Intraocular Lens Designs

Effect of Implantable Collamer Lens on Anterior Segment Measurement and Intraocular Lens Power Calculation Based on IOLMaster 700 and Sirius

Purpose

To investigate the possible effect of an implantable collamer lens (ICL) on ocular biometrics and intraocular lens (IOL) power calculation.

Methods

Ocular measurements were taken preoperatively and at the two-month follow-up using IOLMaster 700 and Sirius in 85 eyes (43 patients) who had previously undergone ICL surgery. IOL power was calculated using either IOLMaster 700 (Barrett Universal II formula) or Sirius (ray-tracing). All data were compared using the paired t-test.

Results

The difference between preoperative and postoperative anterior chamber depth (ACD), lens thickness (LT), and keratometry on the steep axis (K2) measured by IOLMaster 700 was statistically significant (p < 0.001). In 11 of 85 eyes, IOLMaster misjudged the anterior surface of the ICL as that of the lens, leading to an error in ACD and LT. There were no significant differences between preoperative and postoperative axial length (AL) (p = 0.223), white to white (WTW) (p = 0.100), keratometry on flat axis (K1) (p = 0.117), or central corneal thickness (CCT) (p = 0.648), measured using IOLMaster. The difference in IOL power calculated using the Barrett II formula was significant (p = 0.013). Regression analysis showed that AL and K had the greatest influence on IOL calculation (p < 0.001), and ACD and LT had less influence (p = 0.002, p = 0.218, respectively). K1 and K2 were modified to exclude the influence of K2, and modified IOLs showed no difference between pre and postoperation (p = 0.372). Preoperative and postoperative ACD measured using Sirius were significantly different (p < 0.001); however, the IOL power calculated using ray-tracing technology showed no significant differences (p > 0.05).

Conclusions

The ocular biometric apparatus may misjudge the anterior surface of the lens, resulting in measurement errors of ACD and LT, which has little effect on the calculation of IOL power when using IOLMaster 700 (Barrett Universal II formula) and Sirius (ray-tracing).

Visual and optical performance with hybrid multifocal intraocular lenses

During the past years, the wish to become independent of spectacles has been growing among cataract and presbyopic patients due to many factors, such as the increase in near visual demands, the aesthetic need for a spectacle-free image and ageing of refractive surgery patients, among others. This review assesses recently published studies that analyse visual and optical performance through different metrics of eyes implanted with multifocal intraocular lenses (IOLs), particularly hybrid IOL designs. The published evidence suggests that hybrid multifocal IOLs provide very good outcomes in a number of visual and optical performance parameters. Patients implanted with this type of IOL obtain a satisfactory full range of visual functions, including patients of particular characteristics such as highly ametropic or post-LASIK.

Mesopic contrast sensitivity and ocular higher-order aberrations in eyes with conventional spherical intraocular lenses

PURPOSE

To investigate relationship between mesopic contrast sensitivity (CS) function and ocular higher-order aberrations in eyes implanted with conventional spherical intraocular lenses (IOL).

DESIGN

Prospective, nonrandomized case series.

METHODS

Sixty-eight eyes of 48 patients who attained best spectacle-corrected visual acuity (BSCVA) of 20/20 or better after phacoemulsification and spherical IOL implantation were included in the study. At 2 months postoperatively, mesopic CS was measured with the Mesotest II (Oculus; Wetsler, Germany), and ocular higher-order aberrations for a 4-mm pupil were measured with the Hartmann-Shack aberrometer. CS and letter CS under photopic conditions were recorded with the CSV-1000 charts (Vector Vision Co, Greenville, Ohio, USA).

RESULTS

There was significant correlation between mesopic CS and ocular fourth-order root mean square (RMS) of wavefront aberration (Spearman r(s) = -0.293; P = .017), but no correlation was found between mesopic CS and ocular third-order RMS (r(s) = 0.196; P = .189). Ocular third- and fourth-order RMS did not correlate with other parameters, including BSCVA, and CS and letter CS under photopic conditions.

CONCLUSIONS

Mesopic CS is significantly associated with ocular fourth-order RMS of wavefront aberrations in eyes implanted with conventional spherical IOLs.

Optimizing higher-order aberrations with intraocular lens technology

PURPOSE OF REVIEW

Aspheric intraocular lens technology has been implemented during the past 5 years, and more and more intraocular lenses with different amounts of asphericity are becoming available. Despite the efficacy in the correction of spherical aberration and the good results on implanted eyes, the theoretical advantages of aspheric intraocular lenses are still controversial.

RECENT FINDINGS

All investigations showed the ability of the aspheric intraocular lenses to correct the positive spherical aberration of the cornea, with variable impact on the total eye wavefront but with constant advantages in the optical quality of the eyes as measured by the Modulation Transfer Function, the Point Spread Function, and the contrast sensitivity of implanted patients. Theoretical studies on model eyes underlined some possible limitations of aspheric intraocular lenses, especially sensitivity to decentration. In addition, the actual optical quality in implanted eyes is also affected by light scattering, a parameter missed by simple aberration analysis.

SUMMARY

Aspheric intraocular lenses effectively reduce spherical aberration in implanted eyes, with improvement in optical quality over the parent spherical intraocular lens. The advantages for implanted eyes could be limited by decentration, by small pupil diameter, and by reduced media transparency.