Effect of Higher-order Wavefront Aberrations on Binocular Summation

Visual Outcomes, Patient Satisfaction, and Light Distortion Analysis After Blended Implantation of Rotationally Asymmetric Multifocal Intraocular Lenses

PURPOSE

To evaluate the visual outcomes and patient satisfaction after blended implantation of rotationally asymmetric multifocal intraocular lenses (IOLs) (LENTIS Mplus LS-313 +3.00 and +1.50 diopters [D], Oculentis GmbH).

METHODS

This was an interventional prospective study that included 40 eyes of 20 patients who underwent uneventful refractive lens exchange. Patients were implanted with the LENTIS Mplus LS-313 +3.00 D IOL in the non-dominant eye and the +1.50 D IOL in the dominant eye. Twelve months after surgery, binocular and monocular uncorrected and corrected near, intermediate, and distance visual acuity, defocus curve, contrast sensitivity, and light distortion analysis (LDA) were evaluated. Monocular total ocular aberrometry with a pyramidal wavefront sensor (Osiris; CSO) and patient satisfaction was evaluated with the 10-item Near Activity Vision Questionnaire (NAVQ-10).

RESULTS

There was a statistically significant improvement in the uncorrected distance visual acuity in both eyes after surgery (P < .001), with good uncorrected near and intermediate distance visual acuity (0.18 and 0.38 logMAR, respectively). The binocular defocus curve showed good levels of visual acuity for the most important ranges of vision. Contrast sensitivity and LDA had significantly better results when measured binocularly than monocularly. Higher order aberrations were significantly higher in the +3.00 D eye (P < .001). The mean Rasch score for the NAVQ-10 questionnaire was 26.9 ± 27.66.

CONCLUSIONS

Visual outcomes, defocus curve, LDA, and contrast sensitivity were significantly better binocularly than monocularly. The implantation of a blended IOL combination with different near addition complements the advantages of each IOL, improving binocular visual outcomes and providing good patient satisfaction. [J Refract Surg. 2020;36(12):796-803.].

Bilateral symmetry in vision and influence of ocular surgical procedures on binocular vision: A topical review

We analyze the role of bilateral symmetry in enhancing binocular visual ability in human eyes, and further explore how efficiently bilateral symmetry is preserved in different ocular surgical procedures. The inclusion criterion for this review was strict relevance to the clinical questions under research. Enantiomorphism has been reported in lower order aberrations, higher order aberrations and cone directionality. When contrast differs in the two eyes, binocular acuity is better than monocular acuity of the eye that receives higher contrast. Anisometropia has an uncommon occurrence in large populations. Anisometropia seen in infancy and childhood is transitory and of little consequence for the visual acuity. Binocular summation of contrast signals declines with age, independent of inter-ocular differences. The symmetric associations between the right and left eye could be explained by the symmetry in pupil offset and visual axis which is always nasal in both eyes. Binocular summation mitigates poor visual performance under low luminance conditions and strong inter-ocular disparity detrimentally affects binocular summation. Considerable symmetry of response exists in fellow eyes of patients undergoing myopic PRK and LASIK, however the method to determine whether or not symmetry is maintained consist of comparing individual terms in a variety of ad hoc ways both before and after the refractive surgery, ignoring the fact that retinal image quality for any individual is based on the sum of all terms. The analysis of bilateral symmetry should be related to the patients' binocular vision status. The role of aberrations in monocular and binocular vision needs further investigation.

Ocular aberrations in amblyopic children

PURPOSE

To study the pattern of ocular aberrations in amblyopic children, and evaluate a possible relation to etiology and treatment outcomes of amblyopia.

METHODS

The WaveScan Wavefront System (AMO, Santa Ana, CA, USA) aberrometer was used to assess 75 eyes (60 children) after instillation of 1% cyclopentolate eyedrops. There were 29 males and 31 females with a mean age of 9.23 ± 2.55 years (range, 5-14 years). The study sample was subdivided into four groups; 16 emmetropic non-amblyopic eyes (control group); 24 pre-treatment newly diagnosed amblyopic eyes; 16 eyes of treated amblyopes and; 19 eyes with refractory amblyopia.

RESULTS

Amblyopes had statistically significant greater root mean square (RMS) values for whole eye aberrations, 2nd order aberrations, defocus ([Formula: see text]) and astigmatism ([Formula: see text]) compared to emmetropes (P < 0.0001). The refractory amblyopic group showed statistically significant differences in whole eye RMS, 2nd order- aberrations, defocus ([Formula: see text]) and astigmatism ([Formula: see text]) when compared to treated amblyopic groups (P < 0.0001). Apart from a statistically significant difference in 5th order RMS of pre-treated amblyopes versus the control group, no other significant differences were found in higher order aberrations (HOAs: coma, spherical, higher-order astigmatism, trefoil, or 3rd, 4th, 5th or 6th order terms) between emmetropes and any of the amblyopic groups.

CONCLUSION

Lower order aberrations remain the major factor that affect retinal image quality and hence amblyopia development especially in ametropic eyes. This can be corrected optically. Studying HOA profile in amblyopic eyes failed to explain why refractory amblyopia does not respond to orthoptic treatments. This outcome indicates that theories of central problems in image processing and binocular interaction are likely the main cause of refractory amblyopia.

Ethnic differences in higher-order aberrations: Spherical aberration in the South East Asian Chinese eye

PURPOSE

To determine the distribution of higher-order corneal and ocular aberrations in a healthy refractive surgery population.

SETTING

Island Hospital, Penang, Malaysia.

METHODS

In this prospective observational study, 1 eye of ethnic Chinese refractive surgery patients was evaluated with an Orbscan II corneal topographer and a Zywave Hartmann-Shack aberrometer with a 6.0 mm pupil. Height data were analyzed to derive the higher-order aberrations (HOAs) from the 3rd to 5th Zernike order.

RESULTS

The mean spherical equivalent in the 70 eyes evaluated was -6.46 diopters +/- 3.10 (SD). The mean total corneal HOA was 0.574 +/- 0.218 microm (range 0.269 to 1.249 microm) and the mean total ocular HOA, 0.525 +/- 0.354 microm (range 0.138 to 2.145 microm). There was no statistically significant correlation with age. The mean 3rd-order ocular aberration was 0.399 +/- 0.287 microm; the mean 4th-order, 0.297 +/- 0.223 microm; and the mean 5th-order, 0.108 +/- 0.101 microm. Corneal spherical aberration was greater than ocular spherical aberration (mean 0.312 +/- 0.114 microm versus 0.200 +/- 0.170 microm). Multilinear regression showed that the only dependent that predicted ocular spherical aberration was anterior corneal asphericity (r(2) = 0.227, F = 17.95, P<.001).

CONCLUSION

Corneal and ocular aberrations in South East Asian Chinese eyes were significantly greater than that reported in other populations. Population differences in wavefront errors were significant, and this should be noted in patient management.

Decision Assistant Wizard to standardize optimal outcomes in excimer laser refractive corneal surgery

PURPOSE

To assess a decision tree analysis system to further optimize refractive surgery outcomes.

METHODS

A 5-step decision tree, the Decision Assistant Wizard, based on previous experience with the SCHWIND AMARIS laser, was applied for selecting a customized refractive surgery treatment mode (aspheric aberration neutral, corneal wavefront-guided, or ocular wavefront-guided) to eliminate or reduce total aberration.

RESULTS

Using the Decision Assistant Wizard, 6467 LASIK treatments were performed over a 30-month period; 5262 and 112 for myopic and hyperopic astigmatism, respectively, using aspheric aberration neutral (AF) profiles, 560 using corneal wavefront-guided profiles, and 533 using ocular wavefront-guided profiles. Twenty-two (0.3%) retreatments were performed overall; 18 (0.3%) and 0 (0%) after myopic and hyperopic astigmatism, respectively, using AF, 3 (0.5%) after corneal wavefront-guided profiles, and 1 (0.2%) after ocular wavefront-guided profiles.

CONCLUSIONS

Decision Assistant Wizards may further optimize refractive surgical outcomes by providing the most appropriate ablation pattern based on an eye's anamnesis, diagnosis, and visual demands. The general principles may be applied to other laser systems; however, specifics will depend on manufacturers' specifications.

Association between amblyopia and higher-order aberrations

We report a case with asymmetric higher-order aberrations and wavefront profiles possibly leading to unilateral amblyopia. Stimulus deprivation, strabismus, substantially unequal refractive error, microtropia, and organic causes were ruled out. Keratographic assessment was similar bilaterally, but there was a between-eye difference by wavefront analysis. The predominant aberration in the left eye was defocus and in the right eye, x-axis trefoil. This resulted in different wavefront profiles and point-spread functions, which could have caused amblyopia during the critical age period. The case shows a previously unreported but logically probable cause of amblyopia. Since a single case can suggest the biological plausibility of a hypothesis but cannot prove the strength of the association, further research is required in patients with no cause or an insufficient explanation for amblyopia, especially patients with a mild refractive error difference.

NeuroVision Treatment for Low Myopia Following LASIK Regression

PURPOSE

To evaluate a novel non-surgical method for improving vision in a refractive surgery patient.

METHODS

A 45-year-old man who had undergone LASIK 5 years previously presented with blurred distance vision. Unaided vision in the right eye was 20/329-2) and 20/20 in the left eye. He enrolled for NeuroVision treatment (NeuroVision Pte Ltd, Singapore), a computer-based interface in which a repetitive set of visual excerises is performed for 10 to 12 weeks.

RESULTS

After 35 sessions, unaided visual acuity in the right eye was 20/16(-3) and 20/20(-1) in the left eye, representing 2.8 lines of improvement in the right eye and 1.6 lines in the left eye.

CONCLUSIONS

NeuroVision, a noninvasive treatment based on the concept of perceptual learning, is a benefit in cases in which surgical enhancement is not recommended.

Interocular high-order corneal wavefront aberration symmetry

The interocular symmetry of the high-order corneal wavefront aberration (WA) in a population of myopic eyes was analyzed before and after photorefractive keratectomy (PRK). The preoperative and one-year postoperative corneal aberration data (from third to seventh Zernike orders) for 4- and 7-mm pupils from right and left eyes were averaged after correcting for the effects of enantiomorphism to test for mirror symmetry. Also, the mean corneal point-spread function (PSF) for right and left eyes was calculated. Preoperatively, a moderate and high degree of correlation in the high-order corneal WA between eyes was found for 4- and 7-mm pupils, respectively. Myopic PRK did not significantly change the interocular symmetry of corneal high-order aberrations. No discernible differences in the orientation PSF between eyes were observed one year after surgery in comparison with the preoperative state over the two analyzed pupils.