The Effect of the Position Determination Error for Flexible Linear Array Elements on the Tomogram Focusing.

In the article, the study of the quality of tomogram focusing during the inspection of objects with curved surfaces by flexible acoustic array was described. The main goal of the study was theoretically and experimentally define the acceptable deviation limits of the elements' coordinates values. The tomogram reconstruction was performed by the total focusing method. The Strehl ratio was chosen as a criterion for assessing the quality of tomogram focusing. The ultrasonic inspection procedure were simulated and validated experimentally by means of convex and concave curved arrays. In the study, it was proven that the elements coordinates of the flexible acoustic array were determined with an error of no more than 0.18λ and the tomogram image was obtained in sharp focus.

Effect of postoperative residual astigmatism on visual outcomes after trifocal intraocular lens implantation.

Purpose: The aim of this study was to evaluate the effect of residual astigmatism on postoperative visual outcomes after trifocal intraocular lens implantation. Methods: In this prospective observational study, we divided 156 eyes into two groups according to postoperative astigmatism measured by subjective optometry and followed them up for 3 months. Visual acuity, modulation transfer function (MTF) curves, Strehl ratio (SR), Visual Function Index-14 scores, and photic phenomena were compared. Results: Linear regression analysis revealed a weak correlation between residual astigmatism and uncorrected distance visual acuity (UDVA) (r = 0.190, P = 0.016) at 3 months and a significant between-group difference at 1- and 3-month postoperative UDVA (P = 0.038, P = 0.018, respectively). MTF curve values and SR (MTF-10 total, MTF-10 cornea, MTF-30 total, MTF-30 cornea, SR Total, and SR cornea) were significantly worse (P < 0.001), and the Visual Function Index-14 scores were lower in the 0.5 < astigmatism ≤ 1.25 D group (P < 0.05) than in the astigmatism ≤ 0.5 D group. No significant differences were found in the frequency, severity, and bothersomeness of photic phenomena (P > 0.05). Conclusion: Postoperative residual astigmatism affects the UDVA of the trifocal intraocular lens-implanted eyes. Although we found no significant differences in uncorrected intermediate and near visual acuity, both objective and subjective visual quality were affected, suggesting the need for surgical planning when the anticipated postoperative astigmatism is >0.5 D.

Towards a wavefront-preservation X-ray crystal monochromator for high-repetition-rate FELs.

The wavefront preservation of coherent X-ray free-electron laser beams is pushing the requirement on the quality and performance of X-ray optics to an unprecedented level. The Strehl ratio can be used to quantify this requirement. In this paper, the criteria for thermal deformation of the X-ray optics are formulated, especially for crystal monochromators. To preserve the X-ray wavefront, the standard deviation of the height error should be sub-nm for mirrors and less than 25 pm for crystal monochromators. Cryocooled silicon crystals combined with two techniques can be used to achieve this level of performance for monochromator crystals: (1) using a focusing element to compensate the second-order component of the thermal deformation; (2) introducing a cooling pad between the cooling block and silicon crystal and optimizing the effective cooling temperature. Each of these techniques allows the thermal deformation in standard deviation of the height error to be reduced by an order of magnitude. As an example, for the LCLS-II-HE Dynamic X-ray Scattering instrument, the criteria on thermal deformation of a high-heat-load monochromator crystal can be achieved for a 100 W SASE FEL beam. Wavefront propagation simulations confirm that the reflected beam intensity profile is satisfactory on both the peak power density and focused beam size.

Comparison of postoperative visual performance between trifocal intraocular lens and monofocal intraocular lens.

OBJECTIVES: To compare the subjective and objective visual quality more comprehensively after surgery of the commonly used multifocal intraocular lenses (IOL) and monolocal IOL implants through long-term systematic clinical observation, providing reference and basis for clinical application. METHODS: Non-randomized controlled trial. A total of 91 (138 eyes) patients between June 2020 and December 2020 were implanted trifocal IOL or monofocal IOL after phacoemulsification in a tertiary class hospital in Wuhan. Monocular testing 3 months after surgery included best-spectacles corrected and uncorrected visual at distant, intermediate, and near vision; spherical equivalent (SE); defocus curve; modulation transfer function (MTF); dysfunctional lens index (DLI); Strehl ratio (SR); mesopic contrast sensitivity function; quality-of-life, spectacles independence, visual disturbance, and surgical satisfaction surveys 3 months post-surgery. RESULTS: There was statistically better uncorrected vision acuity with trifocal IOLs in all range, while monofocal IOL had statistically better mesopic contrast sensitivity at specific spatial frequencies and statistically worse defocus curves, spectacles independence, and surgical satisfaction. The trifocal IOL performed better in subjective quality of vision and life and spectacles independence questionnaires, and the objective quality of vision had no statistical significance. CONCLUSION: Compared to monofocal IOL, trifocal IOL could provide a full range of clear vision for the majority of patients with simple cataracts, improve the rate of spectacles independence and patient satisfaction. And the objective quality of vision did not show any difference.

Clinical efficacy of femtosecond laser-assisted cataract surgery combined with PanOptix trifocal intraocular lens implantation / 国际眼科杂志(Guoji Yanke Zazhi)

AIM: To evaluate the clinical efficacy of femtosecond laser-assisted cataract surgery combined with PanOptix trifocal intraocular lens implantation.METHODS:The retrospective study enrolled 22 cases(26 eyes)of cataract patients who underwent femtosecond laser-assisted cataract surgery combined with PanOptix trifocal intraocular lens implantation from August 2020 to August 2021. Follow-up to 3mo after surgery, the changes of far, intermediate and near visual acuity, aberration, Strehl ratio(SR)and modulation transfer function cutoff(MTF-cutoff)frequency were compared. Defocus curve at 1mo postoperatively was made, and the visual quality and satisfaction were evaluated after 3mo of surgery.RESULTS: The visual acuity of all patients was better than 0.1(LogMAR)at the far, intermediate and near distance at 1d, 1wk, 1 and 3mo postoperatively, and it was significantly improved compared with those before surgery(all P&#x0026;#x003C;0.01). The defocus curve transitioned smoothly between +0.5 and -3.0D at 1mo after surgery, and visual acuity was better than 0.63. The total aberration and spherical aberration in the whole eye were significantly lower after surgery than before, and the SR and MTF-cutoff were significantly improved at 1d and 1wk after surgery(all P&#x0026;#x003C;0.05). With high satisfaction and good visual quality, patients could watch at far, intermediate and near distance without wearing glasses at 3mo after surgery.CONCLUSION: Femtosecond laser-assisted cataract surgery combined with PanOptix trifocal intraocular lens implantation gave patients a comfortable and satisfactory full-course vision.

Comparison of Corneal Optical Quality After SMILE, Wavefront-Optimized LASIK and Topography-Guided LASIK for Myopia and Myopic Astigmatism.

Purpose: To compare visual outcomes and corneal optical quality after small incision lenticule extraction (SMILE), wavefront-optimized (WFO) FS-LASIK, and topography-guided customized ablation treatment (TCAT) FS-LASIK for myopia. Methods: This prospective case-series study included 283 eyes of 283 myopic patients who underwent SMILE or FS-LASIK. There were 102, 100, and 81 eyes in the SMILE group, WFO group and TCAT group, respectively. The tomography system (Sirius) was used to measure corneal aberrations and optical quality. Results: At postoperative 1 and 6 months, there were no significant differences in uncorrected distance visual acuity and corrected distance visual acuity among the three groups (P > 0.05). Postoperative manifest refractive spherical equivalent was similar among the groups (P > 0.05). There was statistically significant difference in cylinder at 1 month among the three groups, with the highest mean value in TCAT group (P < 0.05). The corneal optical path difference, root mean square of corneal astigmatism and strehl ratio were the most superior in the TCAT group at postoperative 1 and 6 months (P < 0.05). Conclusion: SMILE, WFO FS-LASIK, and TCAT FS-LASIK provided similar visual results. The corneal visual quality after TCAT FS-LASIK was the best.

Sensitivity of remote focusing microscopes to magnification mismatch.

Remote focusing (RF) is a technique that greatly extends the aberration-free axial scan range of an optical microscope. To maximise the diffraction limited depth range in an RF system, the magnification of the relay lenses should be such that the pupil planes of the objectives are accurately mapped on to each other. In this paper we study the tolerance of the RF system to magnification mismatch and quantify the amount of residual spherical aberration present at different focusing depths. We observe that small deviations from ideal magnification results in increased amounts of residual spherical aberration terms leading to a reduction in the diffracted limited range. For high-numerical aperture objectives, the simulation predicts a 50% decrease in the diffracted limited range for 1% magnification mismatch. The simulation has been verified against an experimental RF system with ideal and nonideal magnifications. Experimentally confirmed predictions also provide a valuable empirical method of determining when a system is close to the ideal phase matching condition, based on the sign of the spherical aberration on either side of focus.

Visual interaction of 2nd to 5th order Zernike aberration terms with vertical coma.

PURPOSE: In order to better understand the optical consequence of residual aberrations during conventional rigid contact lens wear in keratoconus, this study aimed to quantify the visual interaction between positive vertical coma (C(3, -1)) and other individual 2nd to 5th radial order Zernike aberration terms. METHODS: The experiment proceeded in two parts. First, two levels of C(3, -1) (target term) were simulated. Individual Zernike aberration terms from the 2nd to 5th radial orders (test terms) were combined in 0.05-µm steps a) from -2.00 µm to +2.00 µm with +1.00 µm of C(3, -1) and b) from -1.00 µm to +1.00 µm with +0.50 µm of C(3, -1). The resulting combinations were used to calculate the logarithm of the visual Strehl ratio (logVSX) and predict the relative beneficial or deleterious impact of the interaction. Second, for test terms where an interaction was predicted to provide more than a 0.25 logVSX benefit compared to C(3, -1) alone, high contrast logMAR acuity charts were constructed (simulating the manner in which the test + target term combinations would impact the retinal image of the chart), and randomly read by three well-corrected, typically-sighted individuals through a 3.0-mm diameter artificial pupil. RESULTS: When combined with positive C(3, -1), C(3, -3), C(4, -4), C(5, -5), C(5, -3), and C(5, -1) exhibited better visual image quality compared with C(3, -1) alone. Ratios of the test terms to target term providing maximal benefit remained constant for both +0.50 µm and +1.00 µm of C(3, -1). C(3, -3) and C(5, -1) had the largest predicted beneficial effect, with the maximal effect for +1.00 µm of C(3, -1) occurring with +0.35 µm of C(5, -1) and -1.00 µm of C(3, -3). When individuals read letter charts convolved with the point spread function derived from C(3, -1) combined with C(3, -3) and C(3, -1) combined with C(5, -1), the maximal beneficial effect was 0.27 logMAR (13.5 letters) for C(3, -3) and 0.36 logMAR (18 letters) for C(5, -1). CONCLUSIONS: While most interactions reduced visual image quality, combinations of C(3, -3) (vertical trefoil) and C(5, -1) (vertical secondary coma) provided a clinically relevant beneficial effect in the presence of C(3, -1) (vertical coma) which was demonstrated in both through-focus simulation and chart reading tests. Future work will examine whether these effects persist in the presence of the entire spectrum of residual aberrations seen in the eyes of individuals with keratoconus.

Optimal STEM Convergence Angle Selection Using a Convolutional Neural Network and the Strehl Ratio.

The selection of the correct convergence angle is essential for achieving the highest resolution imaging in scanning transmission electron microscopy (STEM). The use of poor heuristics, such as Rayleigh's quarter-phase rule, to assess probe quality and uncertainties in the measurement of the aberration function results in the incorrect selection of convergence angles and lower resolution. Here, we show that the Strehl ratio provides an accurate and efficient way to calculate criteria for evaluating the probe size for STEM. A convolutional neural network trained on the Strehl ratio is shown to outperform experienced microscopists at selecting a convergence angle from a single electron Ronchigram using simulated datasets. Generating tens of thousands of simulated Ronchigram examples, the network is trained to select convergence angles yielding probes on average 85% nearer to optimal size at millisecond speeds (0.02% of human assessment time). Qualitative assessment on experimental Ronchigrams with intentionally introduced aberrations suggests that trends in the optimal convergence angle size are well modeled but high accuracy requires a high number of training datasets. This near-immediate assessment of Ronchigrams using the Strehl ratio and machine learning highlights a viable path toward the rapid, automated alignment of aberration-corrected electron microscopes.

A comparative evaluation of visual, refractive, and patient-reported outcomes of three diffractive trifocal intraocular lenses

@#OBJECTIVE: To compare the visual, refractive, and patient-reported outcomes of eyes implanted with one of 3 trifocal intraocular lenses (IOLs). METHODS: This is a cross-sectional, comparative, non-interventional study wherein subjects implanted with FineVision Micro F, AT LISA tri 839MP or AcrySof IQ PanOptix trifocal IOL after phacoemulsification were recruited. Manifest refraction, uncorrected and corrected visual acuity (VA) at distance, intermediate and near vision, contrast sensitivity, modulated transfer function (MTF) values and questionnaire answers were compared among the 3 groups using analysis of variance (ANOVA). RESULTS: Fifty-seven (57) eyes were included in the study: 21 eyes with FineVision (group A), 21 eyes with LISA tri (group B), and 15 eyes with PanOptix IOL (group C). The post-operative mean manifest spherical equivalent was -0.01D, -0.07D, and 0.05D, respectively (p=0.083). Uncorrected distance VA and best-corrected distance VA were similar among the groups. Groups A and C had better uncorrected and corrected intermediate VA at 80 cm and at 60 cm compared to group B. Group A had significantly better uncorrected near visual acuity than groups B and C (p=0.032). Mesopic contrast sensitivity testing showed group C had higher contrast sensitivities without glare in at the spatial frequency of 6 CPD (p=0.038) and with glare at 3 CPD (p=0.039) and at 12 CPD (p=0.009). MTF average height analysis showed that the group A had significantly superior resolution in far targets compared to groups B and C (p=0.001). At near targets, groups A and C had better resolutions compared to group B (p=0.017). There was no significant difference in patient satisfaction for far, intermediate and near VA among the groups. CONCLUSION: Eyes implanted with any of the 3 trifocal IOL designs achieved excellent uncorrected and bestcorrected distance, intermediate and near vision. FineVision and PanOptix provided significantly better intermediate vision than LISA tri at both 80 cm and 60 cm testing distance. FineVision had better near visual outcomes than PanOptix and LISA tri. Patient satisfaction was high in all 3 trifocal IOLS

One-year effect of wearing orthokeratology lenses on the visual quality of juvenile myopia: a retrospective study.

OBJECTIVE: To study the one-year effect of wearing orthokeratology (OK) lenses on the visual quality of juvenile myopia. METHODS: The right eyes of 36 juvenile myopias were retrospectively studied in this work. Q-value, e-value, corneal curvature, strehl ratio (SR), modulation transfer function (MTF) and wavefront aberration (WA) were compared before and at 1, 3 and 12 months after wearing OK lenses. The SR, MTF and WA of cornea, internal optic and ocular were analyzed separately. The spherical and cylinder diopter, vision acuity, compensating factor (CF) and compensative rate (CF%) were compared before and at 12 months after wearing OK lenses. RESULTS: (1) The vision of LogMAR increased and the corneal curvature decreased significantly after wearing OK lenses. There was no significant difference for the e-value before and after wearing OK lenses. The Q-value increased at 1 month but decreased at 3 and 12 months remarkably. (2) The ocular and internal optic SR and MTF increased significantly at 1 month and then remained stable. The MTF in different spacial frequencies increased after wearing OK lenses. There was no significant difference for the corneal SR before and after wearing OK lenses, and the corneal MTF decreased significantly after wearing OK lenses. (3) For the ocular, the total higher order aberration (HOA), spherical, coma and trefoil aberrations increased, and the total aberration, total lower order aberration (LOA) and defocus aberration decreased obviously except astigmatism. The corneal aberrations increased significantly after wearing OK lenses except astigmatism. For the internal optic, the total aberration, total LOA and defocus aberration decreased, and the total HOA, coma and trefoil aberration increased significantly except the astigmatism and spherical aberrations. (4) The CF and CF% of total aberration, total LOA, total HOA and coma aberrations increased, and those of astigmatism and spherical decreased at 12 months. CONCLUSIONS: Orthokeratology is effective in correcting the refractive error and improving the vision quality of juvenile myopia over the one-year follow-up period.

Utility of the optical quality analysis system for decision-making in cataract surgery.

BACKGROUND: A cataract is a common cause of vision impairment that requires surgery in older subjects. The Optical Quality Analysis System (OQAS, Visiometrics SL, Terrassa, Spain) assesses the optical quality of the eye in cataract patients. This study shows the role of the optical quality evaluation system for decision-making in cataract surgery. We investigated the clinical utility of the OQAS for decision-making in cataract surgery. METHODS: Sixty-seven eyes from 67 patients undergoing cataract surgery and 109 eyes from 109 control subjects were compared. The best corrected visual acuity (BCVA) was measured. The objective scatter index (OSI), modulation transfer function (MTF), Strehl ratio, predicted visual acuity (PVA) 100%, PVA 20%, and PVA 10% were measured using the OQAS. The sensitivity and specificity of the different parameters were analyzed using the receiver operating characteristic (ROC) curve. The main parameters measured were sensitivity and specificity. RESULTS: The BCVA, OSI, PVA 100%, PVA 20%, and PVA 10% were higher in the cataract group compared to those in the control group, while the MTF and Strehl ratios were lower (p <  0.001 for all). ROC analysis showed that the OSI had the largest area under the curve and that the sensitivity and specificity of the OSI were 83.9 and 84.6%, respectively, at the optimal cut-off point of 2.35. CONCLUSION: The MTF, OSI, Strehl ratio, PVA 100%, PVA 20% and PVA 10% may be useful parameters for preoperative decision-making in cataract surgery. The OSI appears to be the most effective parameter for this purpose.

Optimal orientation for angularly segmented multifocal corrections.

PURPOSE: Evaluate the importance of orientation of multifocal lens designs with angular increments of addition. METHODS: Optical properties of one monofocal and three multifocal designs were analysed with the visual Strehl ratio (VSOTF) metric through-focus (-1 to 5 D). Designs were tested in combination with the higher-order aberrations (HOAs) of 782 subjects (1564 eyes). Simulations included one monofocal, one bifocal (eight orientations), one trifocal (four orientations), and a 4-foci design (four orientations). Monocular and binocular performances of all designs were assessed by computing the area under the through-focus VSOTF plots, the through-focus range of acceptable optical performance, and, for binocular combinations, optical disparity between left and right eyes. RESULTS: Under monocular conditions, bifocal designs generated larger areas under the through focus VSOTF than trifocal designs and 4-foci designs. Specifically, bifocal designs divided vertically were optimal for 48% of eyes. Trifocal designs and 4-foci designs offered longer intervals of acceptable through-focus vision. Coma and spherical aberration values were correlated with the optimal orientation of multifocal corrections. The best binocular combination was achieved with a monofocal and a trifocal lens. The orientation of a multifocal design with angular areas affected the final optical properties of the combination (lens plus eye). CONCLUSIONS: The optical aberration distributions for our population of physiologically normal eyes demonstrated improved performance for some lens design orientations (i.e., left-right segments for 2-zone bifocals). Taking into account the HOAs of healthy patients, with special attention to coma and spherical aberration, will increase the optical quality of angularly divided multifocal solutions.

In vitro comparative optical bench analysis of a spherical and aspheric optic design of the same IOL model.

BACKGROUND: To analyse objective optical properties of the spherical and aspheric design of the same intraocular lens (IOL) model using optical bench analysis. METHODS: This study entailed a comparative analysis of 10 spherical C-flex 570 C and 10 aspheric C-flex 970 C IOLs (Rayner Intraocular Lenses Ltd., Hove, UK) of 26 diopters [D] using an optical bench (OptiSpheric, Trioptics, Germany). In all lenses, we evaluated the modulation transfer function (MTF) at 50 lp/mm and 100 lp/mm and the Strehl Ratio using a 3-mm (photopic) and 4.5-mm (mesopic) aperture. RESULTS: At 50 lp/mm, the MTF values were 0.713/0.805 (C-flex 570 C/C-flex 970 C) for a 3-mm aperture and 0.294/0.591 for a 4.5-mm aperture. At 100 lp/mm, the MTF values were 0.524/0.634 for a 3-mm aperture and 0.198/0.344 for a 4.5-mm aperture. The Strehl Ratio was 0.806/0.925 and 0.237/0.479 for a 3-mm and 4.5-mm aperture respectively. A Mann-Whitney U test revealed all intergroup differences to be statistically significant (p < 0.01). CONCLUSION: The aspheric IOL design achieved higher MTF values than the spherical design of the same IOL for both apertures. Moreover, the differences between the two designs of the IOL were more prominent for larger apertures. This suggests that the evaluated IOL provides enhanced optical quality to patients with larger pupils or working under mesopic conditions.

Effects of Corneal Surface Shape and Optical Quality on the Results of Trial Fitting in Orthokeratology / 中国医科大学学报

Objective To determine the parameters of corneal surface shape and optical quality that affect the results of trial fitting in overnight orthokeratology (OK lenses) in adolescents with myopia.Methods Thirty-eight subjects (67 eyes) who met the inclusion criteria were enrolled in this study.The parameters of corneal surface shape including surface regularity index (SRI),surface asymmetry index (SAI),and Q value were assessed with a corneal topographer before beginning orthokemtology.The Strehl ratio (SR) and the root-mean-square (RMS) of the total higherorder aberrations in a 4-mm pupil were measured before the trial fitting.Participants who had tried orthokeratology were divided into two groups according to the success or failure of trial fitting.Then,we compared the differences in the comeal surface shape and optical quality between the two groups.Results There were 45 eyes in the success group,and 22 eyes in the failure group.There were no statistically significant differences for SRI (P =0.188),SAI (P =0.338),Q value (P =0.657),RMS (P =0.456),and SR (P =0.479) in the two groups.Conclusion The result of trial fitting in orthokemtology is not correlated with the parameters of comeal status and optical quality (SRI,SAI,Q value,RMS,SR).

Assessment of corneal optical quality following small incision lenticule extraction for myopia / 中华实验眼科杂志

Background The current evaluation of corneal optical quality after small incision lenticule extraction (SMILE) is based on the single factor,such as scattering,diffraction or aberration,and all of them are not comprehensive and objective methods.Modulation transfer function (MTF) and Strehl ratio (ST) are novel parameters of corneal optical quality,which can be used to assess the optical quality comprehensively.Objective This study was to evaluate the change of MTF and SR under the photopic and scotopic environment (3 mm and 6 mm pupil size,respectively) after SMILE procedure.Methods The study protocol was approved by Ethic Committee of Tianjin Eye Hospital,and written informed consent was obtained from each patient before any medical procedure.A series cases-observational study with self-control design was carried out.Sixty-three eyes of 32 myopia or myopic astigmatism patients who underwent SMILE surgery in Tianjin Eye Hospital were included from December 2013 to March 2014.The uncorrected visual acuity (UCVA),best corrected visual acuity (BCVA) (LogMAR),the effective index (postoperative UCVA/preoperative BCVA) and refractive diopter were examined,and the MTF,SR and root mean square (RMS) on the anterior corneal surface were measured under the 3 mm and 6 mm pupil size at different spatial frequencies (10,20,30,40,50 and 60 c/d) by Sirius anterior analyzer before surgery and 1 week,1 month and 3 months after surgery,respectively.Results UCVA was ≥0.8 in 59,62 and 63 eyes in 1 week,1 month and 3 months after SMILE,with the percentage of 93.65％,98.41％ and 100％,and the effective index was 1.104± 0.128,1.126±0.145 and 1.158±0.208,respectively.The refractive diopter was normal in the eyes at postoperative 3 months.The MTFs of various spatial frequencies on the vertical and horizontal meridian under the 3 mm pupil size after SMILE were significantly higher than those before SMILE,while under the 6 mm pupil size,the MTFs were higher only on vertical meridian and 10,20,30 and 40 e/d,and there were not significant differences on the horizontal meridian (all at P＜0.05).The SRs under the 3 mm and 6 mm pupil size showed increasing softly after surgery in comparison with before surgery,and the SRs were higher under the 3 mm pupil size than those under the 6 mm pupil size at various time points (all at P＜0.05).There were not significant differences in RMS among different time points under both 3 mm pupil size and 6 mm pupil size (3 mm pupil size:F =1.348,P =0.184;6 mm pupil size:F=1.990,P=0.137).Conclusions SMILE provides a great improvement in corneal optical quality for myopia or myopic astigmatism patients,which is more distinct in photopic condition than that in scotopic condition.

Analysis of the point spread function in total corneal of normal population / 国际眼科杂志(Guoji Yanke Zazhi)

AIM:To explore relationship between the normal strehl ratio ( SR ) values of total aberrations/SR values of total higher-order aberrations and modulation transfer function ( MTF ) at total corneal at different pupil diameters in normal population. METHODS: To exam the SR values of total aberrations and SR values of total higher-order aberrations of total corneals in 200 people ( 400 eyes ) using SIRIUS 3D topography system and analysis the corresponding root-mean-square ( RMS) . RESULTS: The subjects with different pupil diameters (3. 0, 5. 0, 6. 0, 7. 0mm)'s exam results of total corneal were as following:SR value of total aberrations 100’(0. 45±0. 12), (0. 25±0. 06), (0. 17±0. 05), (0. 13±0. 04); SR value of total higher order ab cerrations 100’(0. 69±0. 14), (0. 34±0. 07), (0. 24±0. 05), (0. 16±0. 04);SR value of total aberrations 200’(0. 45±0. 12), (0. 24±0. 06), (0. 20±0. 04), (0. 16±0. 03); SR value of total higher order aberrations 200’(0.70±0. 13), (0. 35±0. 07), (0. 27±0. 06), (0. 20±0.04 ) . The SR values of each group decreases with the increases of pupil diameters. The SR values of total aberrations and SR values of total higher - order aberrations at total corneals are negatively correlated with corresponding RMS value. When the pupil diameter is small, the SR value of total aberrations is more related to higher frequency region of MTF. When the pupil diameter is big, the SR value of total aberrations is more related to lower frequency region of MTF. CONCLUSION: The visual performance of normal people can be well reflected by SR values of total aberrations and SR values of total higher - order aberrations at total corneal.

Critical band masking reveals the effects of optical distortions on the channel mediating letter identification.

There is evidence that letter identification is mediated by only a narrow band of spatial frequencies and that the center frequency of the neural channel thought to underlie this selectivity is related to the size of the letters. When letters are spatially filtered (at a fixed size) the channel tuning characteristics change according to the properties of the spatial filter (Majaj et al., 2002). Optical aberrations in the eye act to spatially filter the image formed on the retina-their effect is generally to attenuate high frequencies more than low frequencies but often in a non-monotonic way. We might expect the change in the spatial frequency spectrum caused by the aberration to predict the shift in channel tuning observed for aberrated letters. We show that this is not the case. We used critical-band masking to estimate channel-tuning in the presence of three types of aberration-defocus, coma and secondary astigmatism. We found that the maximum masking was shifted to lower frequencies in the presence of an aberration and that this result was not simply predicted by the spatial-frequency-dependent degradation in image quality, assessed via metrics that have previously been shown to correlate well with performance loss in the presence of an aberration. We show that if image quality effects are taken into account (using visual Strehl metrics), the neural channel required to model the data is shifted to lower frequencies compared to the control (no-aberration) condition. Additionally, we show that when spurious resolution (caused by π phase shifts in the optical transfer function) in the image is masked, the channel tuning properties for aberrated letters are affected, suggesting that there may be interference between visual channels. Even in the presence of simulated aberrations, whose properties change from trial-to-trial, observers exhibit flexibility in selecting the spatial frequencies that support letter identification.

Accounting for the phase, spatial frequency and orientation demands of the task improves metrics based on the visual Strehl ratio.

Advances in ophthalmic instrumentation have allowed high order aberrations to be measured in vivo. These measurements describe the distortions to a plane wavefront entering the eye, but not the effect they have on visual performance. One metric for predicting visual performance from a wavefront measurement uses the visual Strehl ratio, calculated in the optical transfer function (OTF) domain (VSOTF) (Thibos et al., 2004). We considered how well such a metric captures empirical measurements of the effects of defocus, coma and secondary astigmatism on letter identification and on reading. We show that predictions using the visual Strehl ratio can be significantly improved by weighting the OTF by the spatial frequency band that mediates letter identification and further improved by considering the orientation of phase and contrast changes imposed by the aberration. We additionally showed that these altered metrics compare well to a cross-correlation-based metric. We suggest a version of the visual Strehl ratio, VScombined, that incorporates primarily those phase disruptions and contrast changes that have been shown independently to affect object recognition processes. This metric compared well to VSOTF for letter identification and was the best predictor of reading performance, having a higher correlation with the data than either the VSOTF or cross-correlation-based metric.