Calculation of ocular single-pass modulation transfer function and retinal image simulation from measurements of the polarized double-pass ocular point spread function

Comparison of visual quality in cataract patients with low astigmatism after ART2 or ReSTOR intraocular lens implantation

AIM

To compare visual quality in cataract patients with low corneal astigmatism who underwent intraocular lens (IOL) implantation, and evaluate effects of low levels of astigmatism on visual outcomes in multifocal pseudophakic eyes.

METHODS

This retrospective review of clinical records comprised patients with preoperative regular corneal astigmatism of 0.75-1.0 diopters (D) with-the-rule or 0.5-0.75 D against-the-rule who had uneventful cataract surgery and AcrySof IQ ReSTOR Toric-2 IOL (ART2) or AcrySof IQ ReSTOR IOL (ReSTOR) implantation. Retrospective data collection included postoperative ART2 axis rotation, uncorrected astigmatism, uncorrected entire visual acuities, distance corrected entire visual acuities, average modulation transfer function (aMTF), Strehl ratio (SR), spectacle independence, and patient satisfaction between groups.

RESULTS

Mean ART2 axis rotation was 3.12°±0.70°. No secondary surgery was required to realign IOL axis. Residual astigmatism values were -0.18±0.07 D and -0.91±0.25 D in groups ART2 and ReSTOR (P<0.05). Three months postoperatively, the mean uncorrected distant, intermediate, and near visual acuities of group A were 0.01±0.05, 0.05±0.07, 0.02±0.07 logMAR, respectively; these were better than those of group R, which were 0.08±0.06, 0.15±0.12, and 0.09±0.08 logMAR, respectively (P<0.05). aMTF, SR, and spectacle independence rates were not significantly different. All patients were satisfied with postoperative results.

CONCLUSION

ART2 is more suitable than ReSTOR for cataract patients with regular corneal astigmatism 0.75-1.0 D with-the-rule or 0.5-0.75 D against-the-rule.

Optical quality of toric intraocular lens implantation in cataract surgery

AIM

To analyze the optical quality after implantation of toric intraocular lens with optical quality analysis system.

METHODS

Fifty-two eyes of forty-four patients with regular corneal astigmatism of at least 1.00 D underwent implantation of AcrySof toric intraocular lens, including T3 group 19 eyes, T4 group 18 eyes, T5 group 10 eyes, T6 group 5 eyes. Main outcomes evaluated at 3mo of follow-up, included uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), residual refractive cylinder and intraocular lens (IOL) axis rotation. Objective optical quality were measured using optical quality analysis system (OQAS II(®), Visiometrics, Spain), included the cutoff frequency of modulation transfer function (MTFcutoff), objective scattering index (OSI), Strehl ratio, optical quality analysis system value (OV) 100%, OV 20% and OV 9% [the optical quality analysis system (OQAS) values at contrasts of 100%, 20%, and 9%].

RESULTS

At 3mo postoperative, the mean UDVA and CDVA was 0.18±0.11 and 0.07±0.08 logMAR; the mean residual refractive cylinder was 0.50±0.29 D; the mean toric IOL axis rotation was 3.62±1.76 degrees, the mean MTFcutoff, OSI, Strehl ratio, OV 100%, OV 20% and OV 9% were 22.862±5.584, 1.80±0.84, 0.155±0.038, 0.76±0.18, 0.77±0.19 and 0.78±0.21. The values of UDVA, CDVA, IOL axis rotation, MTFcutoff, OSI, Strehl ratio, OV100%, OV20% and OV9% depending on the power of the cylinder of the implantation were not significantly different (P>0.05), except the residual refractive cylinder (P<0.05).

CONCLUSION

The optical quality analysis system was useful for characterizing the optical quality of AcrySof toric IOL implantation. Implantation of an AcrySof toric IOL is an effective and safe method to correct corneal astigmatism during cataract surgery.

Peripheral optical quality and myopia progression in children

BACKGROUND

To investigate the peripheral optical quality and its relationship with axial elongation, myopic progression in Japanese children.

METHODS

Twenty-nine Japanese children, ages 10 to 12 years old, with baseline refraction from +0.75 D to -5.5 D, were included and followed for 9 months. The central and peripheral point spread functions (PSFs; 0°, 10°, 20°, 30° nasally) were obtained at 0.25 D steps around ±2.5 D of best-focus PSF (BF-PSF) using double-pass PSF system. Modulation transfer function (MTF) area of the BF-PSF was calculated from BF-PSF to represent the peripheral optical quality. Relative peripheral defocus (RPD), the refraction of anterior/posterior focal lines, MTF area, and their correlations with myopia progression were analyzed.

RESULTS

The average refractive change in 9 months was -0.5 ± 0.8 D. The change in axial length was significantly positively correlated with the amount of myopic progression (P = 0.0058) and RPD (P = 0.0007, 0.0036 and 0.0040, at 10°, 20°, 30° respectively) at the initial visit, but did not correlate with the peripheral MTF area. Myopic progression of more than 0.5 D with axial elongation was observed in seven children (MP group). The RPDs at 20° and 30° in the MP group were significantly more hyperopic than in the non-MP group (P = 0.002 and 0.007), whereas there was no significant difference in axial length, and central and peripheral MTF area between the MP and non-MP groups. MP group had more hyperopic focal lines compared with non-MP group at 20° and 30°.

CONCLUSION

These results suggest that the progression of axial myopia in children is associated with hyperopic RPD and refraction of focal lines, not with peripheral optical quality.

Evaluation of Optical Function Using a New Point Spread Function Analysis System in Cataractous and Pseudophakic Eyes: Preliminary Results

PURPOSE

To evaluate optical function in cataractous and pseudophakic eyes using the new point spread function (PSF) analysis system in a clinical setting.

METHODS

We applied this new analysis system in the study of two cataractous eyes and one pseudophakic eye of two patients. Using a PSF analyzer, double-pass PSF was measured directly for each subject, and the single-pass modulation transfer function (MTF) and single-pass PSF were calculated. The simulated retinal images of various sizes of Landolt's rings and their contrast characteristics were also calculated by the PSF analyzer.

RESULTS

The MTF and the contrast of the simulated retinal images degraded in cataractous eyes were compared with data for normal eyes; the degradation pattern depended on the opacification pattern. The MTF and the contrast of the simulated retinal images in the pseudophakic eye improved significantly compared with the cataractous eyes, although both values were lower in the pseudophakic eye than in young normal eyes.

CONCLUSIONS

Our data showed degradation of optical function in cataractous and pseudophakic eyes in comparison with optical function in young normal eyes. If further accumulations of PSF data are made, it may be possible to establish an objective standard by which to measure the progression of cataract, as well as an objective indication for treatment in the future.