Optical Quality Metrics Research Articles

基于人眼光学质量的球差和离焦补偿关系研究

Based on optical quality metrics of human eyes,the counterbalanced relationship between defocus and spherical aberration for wave-front aberration data of preoperative and postoperative myopic eyes is studied.The results show that defocus can not obviously compensate spherical aberration for preoperative patients.But the counterbalanced relationship can be distinctly observed for the postoperative patients, which reveals that the remained defocus can partially ameliorate the influence of the increased higher-order aberrations after corneal refractive surgery on visual performance.For postoperative patients,more than 20%improvement of optical quality can be achieved when the remained defocus ranges from 0.27D to 0. 74D.More than 80%of eyes can achieve better visual performance when the remained defocus ranges from 0.3D to 0.75 for a design of vision correction.

Predicting visual performance from optical quality metrics in keratoconus

Purpose: The aim was to identify optical quality metrics predictive of visual performance in eyes with keratoconus and penetrating keratoplasty (PK) for keratoconus.Methods: Fifty‐four participants were recruited for this prospective, cross‐sectional study. Data were collected from one eye of each participant: 26 keratoconus, 10 PK and 18 normal eyes: average age (mean ± standard deviation) 45.2 ± 10.6-years and 56 per cent female. Visual performance was tested by 10 methods including visual acuity (VA), both high and low contrast (HC‐ and LC‐) and high and low luminance (LL‐), and Pelli‐Robson contrast sensitivity, all tested with and without glare. Corneal first surface wavefront aberrations were calculated from Orbscan corneal topographic data using VOLPro software v7.08 (Sarver and Associates) as a tenth‐order Zernike expansion across three, 4.0-mm and 5.0-mm pupils and converted into 31 optical quality metrics. Pearson correlation coefficients and linear regression were used to relate wavefront aberration metrics to visual performance.Results: Visual performance was highly predictable from optical quality with the average correlation of the order of 0.5. Pupil fraction metrics (for example, PFWc) were responsible for all of the highest correlations at large pupils for example, with HCVA (r = 0.80), LCVA (r = 0.80) and LLLCVA (r = 0.75). Image plane metrics, derived from the optical transfer function (OTF) were responsible for most of the highest correlations at smaller pupils for example, volume under the OTF (VOTF) with HCVA (r = 0.76) and LCVA (r = 0.73).Conclusions: As in normal eyes, visual performance in keratoconus was predicable from optical quality; albeit by different metrics. Optical quality metrics predictive of visual performance in normal eyes, for example, visual Strehl, lack the dynamic range to represent visual performance in highly aberrated eyes with keratoconus. Optical quality outcomes for keratoconus could be reported using many different metrics, but pupil fraction metrics, for example PFWc, perform best for highly aberrated eyes.

Evaluation of optical quality in white light from wavefront aberrations for a myopic population of human eyes

Purpose: To evaluate optical quality in white light for a myopic population by means of some metrics, such as AreaMTF, VSMTF and EE.Methods: One hundred and thirteen myopic eyes of 113 subjects were enrolled in this study. The optical quality metrics in white light were computed from the polychromatic PSF, which was calculated as the super‐position of the monochromatic PSFs for each wavelength.Results: The relationship between optical quality and the root mean square (RMS) of higher‐order aberrations shows that the values of AreaMTF, VSMTF and EE in white light tend to decrease gradually with the increase of RMS. When RMS maintains a constant value, the optical quality varies greatly among eyes. By partial correlation analysis and controlling the impact of total RMS of higher‐order aberrations, the association between the percentage of third‐order aberrations (in total higher‐order aberration) and optical quality can be made. This shows a positive correlation (p < 0.05), which indicates that the greater the percentage of the third‐order aberrations, the better the optical quality, with RMS remaining a constant value. On the contrary, the percentage of fourth‐order aberrations and spherical aberrations shows a negative correlation with optical quality.Conclusions: The fourth‐order and spherical aberrations have a greater effect on vision than other order aberrations. The impact of monochromatic aberrations on optical quality is greater than that of chromatic aberrations.

Comparison of optical quality metrics to predict subjective quality of vision after laser in situ keratomileusis

To compare wavefront-derived metrics to predict subjective quality of vision after laser in situ keratomileusis (LASIK) for myopia. Department of Ophthalmology, Goethe University, Frankfurt am Main, Germany. One month postoperatively, wavefront sensing was performed and overall subjective quality of vision assessed under 3 lighting conditions (photopic, high mesopic, low mesopic) with a questionnaire. Four wavefront-error representations were computed for a pupil diameter of 6.0 mm and individual physiological pupil diameters at 0.4 lux: (1) the visual Strehl ratio based on optical transfer function (VSOTF), (2) the root-mean-square (RMS) value of Zernike orders 2 to 5 (total RMS), (3) higher-order aberration (HOA) RMS, and (4) a wavefront-error breakdown into the RMS of lower-order aberrations, coma, spherical aberration, and remaining HOA. The impact of the postoperative wavefront error on subjective quality of vision was calculated using linear regression analysis. Fifty-six eyes (29 patients) were included. The ability of wavefront error-derived metrics to predict subjective quality of vision was limited. The VSOTF, calculated for the best-corrected eye, showed the highest predictability. Calculation of wavefront error for individual physiological pupil diameters did not improve predictive ability of the metrics. Eyes with a high theoretical retinal-image quality had a high subjective quality of vision, and eyes with a low subjective quality of vision had a low theoretical image quality. Postoperative wavefront error had limited influence on the subjective quality of vision. Postoperative retinal image quality should be kept as high as possible to provide good subjective quality of vision.

Objective Amplitude of Accommodation Computed from Optical Quality Metrics Applied to Wavefront Outcomes

Purpose We studied the accuracy and precision of 32 objective wavefront methods for finding the amplitude of accommodation obtained in 180 eyes. Methods Ocular accommodation was stimulated with 0.5 D steps in target vergence spanning the full range of accommodation for each subject. Subjective monocular amplitude of accommodation was measured using two clinical methods, using negative lenses and with a custom Badal optometer. Results Both subjective methods gave similar results. Results obtained from the Badal optometer where used to test the accuracy of the objective methods. All objective methods showed lower amplitude of accommodation that the subjective ones by an amount that varied from 0.2 to 1.1 D depending on the method. The precision in this prediction also varied between subjects, with an average standard error of the mean of 0.1 D that decreased with age. Conclusions Depth of field increases subjective of amplitude of accommodation overestimating the objective amplitude obtained with all the metrics used. The change in the negative direction of spherical aberration during accommodation increases the amplitude of accommodation by an amount that varies with age.

Optical signal quality metric based on statistical moments and Laguerre expansion

A new and straightforward optical signal quality metric, which is based on the approximation of the analytical probability density function by its Laguerre expansion, is proposed. This expansion uses statistical moments to approximate the true statistics, but, unlike the well-known Gaussian approximation, higher order moments can be used as well. The quality of the proposed metric is discussed and the metric is compared with the Gaussian approximation. It is shown that the new metric provides not only a good estimation of the bit error rate in the range of practical interest but, contrary to the Gaussian approximation, correctly estimates optimum decision threshold and accurately pictures the shape of the noise distribution.

Longitudinal changes of optical aberrations in normal and form-deprived myopic chick eyes

We performed measurements of refraction (with retinoscopy), axial length (with ultrasound biometry) and ocular aberrations (with a custom-built Hartmann–Shack aberrometer) on seven awake White-Leghorn chicks occluded monolaterally with diffusers for two weeks. Treatment started on the first day after hatching (day 0) and measurements were conducted on several days between day 0 and 13. Non-occluded eyes experienced normal emmetropization (decreasing hyperopia at 0.2 ± 0.09 D/day and increasing axial length at 0.05 ± 0.03 mm/day), while occluded eyes developed axial myopia (1.50 ± 0.2 D/day and 0.12 ± 0.02 mm/day). Interocular differences in refraction and axial length by day 13 were on average 17.43 D and 0.86 mm, respectively. Monochromatic high order aberrations decreased with age in both eyes. Average RMS (for 1.5 mm pupil diameter) decreased from 0.11 ± 0.03 at day 0 to 0.06 ± 0.03 μm (day 13) in occluded eyes, and from 0.12 ± 0.05 to 0.03 ± 0.01 μm in non-occluded eyes. MTF-based optical quality metrics also show an improvement with age. However, while this improvement occurs in both eyes, after day 8 myopic eyes tend to show significantly higher amounts of aberrations (and consequently worse best-corrected optical quality) than normal eyes. The degradation imposed by aberrations is small compared to that imposed by defocus and the diffuser. These results suggest a decrease of aberrations during development which does not seem to be visually guided. Myopic eyes showed slightly worse optical quality than normal eyes, suggesting that the geometrical changes resulting from excessive ocular axial growth also affect the optical quality of the ocular components.

Evaluation of optical transfer error as an optical quality metric for post-LASIK eyes

Evaluation of optical transfer error as an optical quality metric for post-LASIK eyes