Variational analysis of the mouse and rat eye optical parameters

Rodent models are increasingly used to study refractive eye development and development of refractive errors; however, there is still some uncertainty regarding the accuracy of the optical models of the rat and mouse eye primarily due to high variability in reported ocular parameters. In this work, we have systematically evaluated the contribution of various ocular parameters, such as radii of curvature of ocular surfaces, thicknesses of ocular components, and refractive indices of ocular refractive media, using variational analysis and a computational model of the rodent eye. Variational analysis revealed that not all variation in ocular parameters has critical impact on the refractive status of the eye. Variation in the depth of the vitreous chamber, thickness of the lens, radius of the anterior surface of the cornea, radius of the anterior surface of the lens, as well as refractive indices for the lens and vitreous, appears to have the largest impact on the refractive error. The radii of the posterior surfaces of the cornea and lens have much smaller contributions to the refractive state. These data provide the framework for further refinement of the optical models of the rat and mouse eye and suggest that extra efforts should be directed towards increasing the linear resolution of the rodent eye biometry and obtaining more accurate data for the refractive indices of the lens and vitreous.OCIS codes: (080.0080) Geometric optics, (170.0170) Medical optics and biotechnology, (330.0330) Vision, color, and visual optics, (000.1430) Biology and medicine, (080.1753) Computation methods, (170.3660) Light propagation in tissues, (170.4460) Ophthalmic optics and devices, (170.4470) Ophthalmology, (330.7326) Visual optics, modeling     

Periscope for noninvasive two-photon imaging of murine retina in vivo

Two-photon microscopy allows visualization of subcellular structures in the living animal retina. In previously reported experiments it was necessary to apply a contact lens to each subject. Extending this technology to larger animals would require fitting a custom contact lens to each animal and cumbersome placement of the living animal head on microscope stage. Here we demonstrate a new device, periscope, for coupling light energy into mouse eye and capturing emitted fluorescence. Using this periscope we obtained images of the RPE and their subcellular organelles, retinosomes, with larger field of view than previously reported. This periscope provides an interface with a commercial microscope, does not require contact lens and its design could be modified to image retina in larger animals.OCIS codes: (170.0110) Imaging systems, (170.4460) Ophthalmic optics and devices, (170.5755) Retina scanning, (180.4315) Nonlinear microscopy, (330.7327) Visual optics, ophthalmic instrumentation     

Calculation of crystalline lens power using a modification of the Bennett method

We present a method for measuring lens power from extended depth OCT biometry, corneal topography, and refraction using an improvement on the Bennett method. A reduced eye model was used to derive a formula for lens power in terms of ocular distances, corneal power, and objective spherical equivalent refraction. An error analysis shows that the formula predicts relaxed lens power with a theoretical accuracy of ± 0.5 D for refractive error ranging from −10 D to + 10 D. The formula was used to calculate lens power in 16 eyes of 8 human subjects. Mean lens power was 24.3 D ± 1.7 D.OCIS codes: (170.4500) Optical coherence tomography, (170.4580) Optical diagnostics for medicine, (330.7325) Visual optics, metrology, (330.7326) Visual optics, modeling     

Improving vision by pupil masking

We propose an alternative solution to improve visual quality by spatially modulating the amplitude of light passing into the eye (related to the eye''s transmittance), in contrast to traditional correction of the wavefront phase (related to the local refractive power). Numerical simulations show that masking the aberrated areas at the pupil plane should enhance visual function, especially in highly aberrated eyes. This correction could be implemented in practice using customized contact or intraocular lenses.OCIS codes: (330.0330) Vision, color, and visual optics; (330.1070) Vision - acuity; (330.4460) Ophthalmic optics and devices     

透气性硬性接触镜和框架眼镜矫正中高度散光视觉质量的比较

目的比较中高度散光患者配戴框架眼镜和透气性硬性接触镜(RGPCL)的主客观视觉质量。方法选取2008年6月-2011年5月中高度角膜散光20例共40只眼进行角膜地形图、综合验光仪验光等检查后,选择合适试戴片作配适评估并定制RGPCL。要求患者戴镜后1周、1个月、3个月和6个月复查,记录矫正视力、镜片配适、眼部情况,并在第4次复查时进行对比敏感度视力检查及主观问卷调查。结果 RGPCL矫正视力优于框架眼镜,但两者对比敏感度视力在各空间频率均无明显差异。主观评分时,远视力两者无明显差别;中距离视力框架眼镜评分(3.825±0.245)分,RGPCL评分(3.525±0.302)分,差异有统计学意义(t=5.339,P=0.000);近距离视力框架眼镜评分(3.795±0.233)分,RGPCL评分(3.690±0.194)分,差异有统计学意义(t=3.462,P=0.030)。有45%患者选择RGPCL为主要配戴方式;40%患者选择RGP CL和框架眼镜交替使用的方式;10%患者选择仅在有特殊社交需求时使用RGPCL;另5%患者放弃使用RGPCL。结论 RGPCL和框架眼镜矫正中高度角膜散光均能取得较满意效果,在中近距离精细作业时框架眼镜矫正视力更为稳定清晰。但由于RGPCL在成像质量和外观上的优势,多数患者仍愿意坚持配戴RGPCL。     

Optical side-effects of fs-laser treatment in refractive surgery investigated by means of a model eye

Optical side-effects of fs-laser treatment in refractive surgery are investigated by means of a model eye. We show that rainbow glare is the predominant perturbation, which can be avoided by randomly distributing laser spots within the lens. For corneal applications such as fs-LASIK, even a regular grid with spot-to-spot distances of ~3 µm is sufficient to minimize rainbow glare perception. Contrast sensitivity is affected, when the lens is treated with large 3D-patterns.OCIS codes: (320.2250) Femtosecond phenomena, (330.7335) Visual optics, refractive surgery, (330.1720) Color vision, (330.4460) Ophthalmic optics and devices     

Age-dependence of the average and equivalent refractive indices of the crystalline lens

Lens average and equivalent refractive indices are required for purposes such as lens thickness estimation and optical modeling. We modeled the refractive index gradient as a power function of the normalized distance from lens center. Average index along the lens axis was estimated by integration. Equivalent index was estimated by raytracing through a model eye to establish ocular refraction, and then backward raytracing to determine the constant refractive index yielding the same refraction. Assuming center and edge indices remained constant with age, at 1.415 and 1.37 respectively, average axial refractive index increased (1.408 to 1.411) and equivalent index decreased (1.425 to 1.420) with age increase from 20 to 70 years. These values agree well with experimental estimates based on different techniques, although the latter show considerable scatter. The simple model of index gradient gives reasonable estimates of average and equivalent lens indices, although refinements in modeling and measurements are required.OCIS codes: (330.4460) Ophthalmic optics and devices, (330.7326) Visual optics, modeling     

应用硬性透氧性隐形眼镜矫正不规则散光的疗效观察

目的评价硬性透氧性隐形眼镜（RGP）矫正不规则散光的疗效。方法对23例（34眼）做眼科检查,包括视力,裂隙灯检查及验光,角膜地形图检查,确诊为不规则散光,排除隐形眼镜佩戴禁忌证,进行硬性透氧性角膜接触镜验配,对其最佳框架矫正视力及RGP矫正视力进行统计学比较。结果硬性透氧性角膜接触镜矫正不规则散光的最佳矫正视力（0．73±0．31）,显著高于框架镜矫正值（0．48±0．30）（P〈0．01）,随访观察6个月视力稳定,无明显不良并发症。结论RGP是矫正不规则散光有效安全方法,能够提高矫正视力及视觉质量。     

Versatile optical coherence tomography for imaging the human eye

We demonstrated the feasibility of a CMOS-based spectral domain OCT (SD-OCT) for versatile ophthalmic applications of imaging the corneal epithelium, limbus, ocular surface, contact lens, crystalline lens, retina, and full eye in vivo. The system was based on a single spectrometer and an alternating reference arm with four mirrors. A galvanometer scanner was used to switch the reference beam among the four mirrors, depending on the imaging application. An axial resolution of 7.7 μm in air, a scan depth of up to 37.7 mm in air, and a scan speed of up to 70,000 A-lines per second were achieved. The approach has the capability to provide high-resolution imaging of the corneal epithelium, contact lens, ocular surface, and tear meniscus. Using two reference mirrors, the zero delay lines were alternatively placed on the front cornea or on the back lens. The entire ocular anterior segment was imaged by registering and overlapping the two images. The full eye through the pupil was measured when the reference arm was switched among the four reference mirrors. After mounting a 60 D lens in the sample arm, this SD-OCT was used to image the retina, including the macula and optical nerve head. This system demonstrates versatility and simplicity for multi-purpose ophthalmic applications.OCIS codes: (170.4500) Optical coherence tomography, (170.3880) Medical and biological imaging, (170.4580) Optical diagnostics for medicine, (330.4460) Ophthalmic optics and devices     

An analytical method for predicting the geometrical and optical properties of the human lens under accommodation

We present an analytical method to describe the accommodative changes in the human crystalline lens. The method is based on the geometry-invariant lens model, in which the gradient-index (GRIN) iso-indicial contours are coupled to the external shape. This feature ensures that any given number of iso-indicial contours does not change with accommodation, which preserves the optical integrity of the GRIN structure. The coupling also enables us to define the GRIN structure if the radii and asphericities of the external lens surfaces are known. As an example, the accommodative changes in lenticular radii and central thickness were taken from the literature, while the asphericities of the external surfaces were derived analytically by adhering to the basic physical conditions of constant lens volume and its axial position. The resulting changes in lens geometry are consistent with experimental data, and the optical properties are in line with expected values for optical power and spherical aberration. The aim of the paper is to provide an anatomically and optically accurate lens model that is valid for 3 mm pupils and can be used as a new tool for better understanding of accommodation.OCIS codes: (080.1010) Aberrations (global), (080.2468) First-order optics, (330.4460) Ophthalmic optics and devices, (330.5370) Physiological optics, (330.7322) Visual optics, accommodation, (330.7326) Visual optics, modeling     

Comparison of binocular through-focus visual acuity with monovision and a small aperture inlay

Corneal small aperture inlays provide extended depth of focus as a solution to presbyopia. As this procedure is becoming more popular, it is interesting to compare its performance with traditional approaches, such as monovision. Here, binocular visual acuity was measured as a function of object vergence in three subjects by using a binocular adaptive optics vision analyzer. Visual acuity was measured at two luminance levels (photopic and mesopic) under several optical conditions: 1) natural vision (4 mm pupils, best corrected distance vision), 2) pure-defocus monovision ( + 1.25 D add in the nondominant eye), 3) small aperture monovision (1.6 mm pupil in the nondominant eye), and 4) combined small aperture and defocus monovision (1.6 mm pupil and a + 0.75 D add in the nondominant eye). Visual simulations of a small aperture corneal inlay suggest that the device extends DOF as effectively as traditional monovision in photopic light, in both cases at the cost of binocular summation. However, individual factors, such as aperture centration or sensitivity to mesopic conditions should be considered to assure adequate visual outcomes.OCIS codes: (330.1400) Vision - binocular and stereopsis, (110.1080) Active or adaptive optics, (330.4460) Ophthalmic optics and devices     

氟硅酮丙烯酸脂材料制作角膜塑形镜控制近视效果及其安全性

背景:氟硅酮丙烯酸脂透气性材料成为制作角膜塑形镜的理想材料,其对眼屈光和眼生理的影响受到关注.目的:研究角膜塑形术控制近视发展的临床效果及安全性.方法:观察18例35眼佩戴1年角膜塑形镜的青少年中、低度近视裸眼视力、屈光度变化、眼轴长度、角膜内皮计数、眼压、角膜Q值等变化.结果与结论:1年后裸眼视力与佩戴前矫正视力比较差异无显著性意义(t=-0.27、P=0.78);佩戴前后1年屈光度、眼轴长度、角膜内皮计数、眼压比较差异无显著性意义(t=1.37、P=0.18;t=-0.94、P=0.35;t=-0.52、P=0.6;t=1.00、P=0.32);佩戴前后1年角膜Q值比较差异有显著性意义(t=-8.03、P=0.00).提示氟硅酮丙烯酸脂透气性材料角膜塑形镜控制近视安全、有效,对眼生理影响小.     

Lowered threshold energy for femtosecond laser induced optical breakdown in a water based eye model by aberration correction with adaptive optics

In femtosecond laser ophthalmic surgery tissue dissection is achieved by photodisruption based on laser induced optical breakdown. In order to minimize collateral damage to the eye laser surgery systems should be optimized towards the lowest possible energy threshold for photodisruption. However, optical aberrations of the eye and the laser system distort the irradiance distribution from an ideal profile which causes a rise in breakdown threshold energy even if great care is taken to minimize the aberrations of the system during design and alignment. In this study we used a water chamber with an achromatic focusing lens and a scattering sample as eye model and determined breakdown threshold in single pulse plasma transmission loss measurements. Due to aberrations, the precise lower limit for breakdown threshold irradiance in water is still unknown. Here we show that the threshold energy can be substantially reduced when using adaptive optics to improve the irradiance distribution by spatial beam shaping. We found that for initial aberrations with a root-mean-square wave front error of only one third of the wavelength the threshold energy can still be reduced by a factor of three if the aberrations are corrected to the diffraction limit by adaptive optics. The transmitted pulse energy is reduced by 17% at twice the threshold. Furthermore, the gas bubble motions after breakdown for pulse trains at 5 kilohertz repetition rate show a more transverse direction in the corrected case compared to the more spherical distribution without correction. Our results demonstrate how both applied and transmitted pulse energy could be reduced during ophthalmic surgery when correcting for aberrations. As a consequence, the risk of retinal damage by transmitted energy and the extent of collateral damage to the focal volume could be minimized accordingly when using adaptive optics in fs-laser surgery.OCIS codes: (110.1080) Active or adaptive optics, (140.3440) Laser-induced breakdown, (140.3300) Laser beam shaping, (330.4460) Ophthalmic optics and devices, (170.4470) Ophthalmology, (330.3350) Vision - laser damage     

Retinal image contrast obtained by a model eye with combined correction of chromatic and spherical aberrations

Correcting spherical and chromatic aberrations in vitro in human eyes provides substantial visual acuity and contrast sensitivity improvements. We found the same improvement in the retinal images using a model eye with/without correction of longitudinal chromatic aberrations (LCAs) and spherical aberrations (SAs). The model eye included an intraocular lens (IOL) and artificial cornea with human ocular LCAs and average human SAs. The optotypes were illuminated using a D65 light source, and the images were obtained using two-dimensional luminance colorimeter. The contrast improvement from the SA correction was higher than the LCA correction, indicating the benefit of an aspheric achromatic IOL.     

Drug-eluting contact lens containing cyclosporine-loaded cholesterol-hyaluronate micelles for dry eye syndrome

A contact lens is an attractive tool for the delivery of ophthalmic drugs, but it has several issues such as the burst release of drugs and the limited drug loading capacity. To overcome these limitations, we developed a cholesterol-hyaluronate (C-HA) micelle-embedded contact lens for efficient hydrophobic drug loading and long-term controlled drug delivery. The contact lens was fabricated via photopolymerization of hydroxyethyl methacrylate (HEMA) using ethylene glycol dimethacrylate (EGDMA) as a cross-linker. The C-HA micelle-loaded contact lens showed statistically significant improvement in wettability and mechanical strength, maintaining the optical transmittance. In vitro drug release tests revealed the controlled delivery of cyclosporine for more than 12 days. Furthermore, the Schirmer tear test, corneal fluorescein staining, and MMP9 fluorescein analysis confirmed its therapeutic effect on dry eye syndrome in disease model rabbits.

A cholesterol-hyaluronate (C-HA) micelle embedded contact lens was developed for efficient hydrophobic drug loading and long-term controlled drug delivery.     

Temporal multiplexing with adaptive optics for simultaneous vision

We present and test a methodology for generating simultaneous vision with a deformable mirror that changed shape at 50 Hz between two vergences: 0 D (far vision) and −2.5 D (near vision). Different bifocal designs, including toric and combinations of spherical aberration, were simulated and assessed objectively. We found that typical corneal aberrations of a 60-year-old subject changes the shape of objective through-focus curves of a perfect bifocal lens. This methodology can be used to investigate subjective visual performance for different multifocal contact or intraocular lens designs.OCIS codes: (330.7335) Visual optics, refractive surgery; (110.3000) Image quality assessment; (220.1010) Aberrations (global); (220.1080) Active or adaptive optics; (330.7327) Visual optics, ophthalmic instrumentation     

Sustained in vivo release from imprinted therapeutic contact lenses

In this paper, we demonstrate the successful in vivo extended release of a small molecular weight therapeutic, ketotifen fumarate (MW=425), from molecularly imprinted, therapeutic contact lenses. This is the first time that a steady, effective concentration of drug is maintained in the tear film from a contact lens for an extended period of time for the entire duration of lens wear. Poly(HEMA-co-AA-co-AM-co-NVP-co-PEG200DMA) soft contact lenses were prepared (100±5 μm thickness, diameter 11.8 mm, power zero), and a constant tear film concentration of 170±30 μg/mL was measured for up to 26 hrs in a New Zealand white rabbit model. The results showed a dramatic increase in ketotifen mean residence time (MRT) and bioavailability compared to topical drop therapy and drug soaked lenses. The MRT for imprinted lenses was 12.47±3.99 hrs, ~4 and 50 fold greater than non-imprinted lenses and 0.035% eye drops (Zaditor?), respectively. Furthermore, AUC(0-26 hrs) was 9 and 94 fold greater for imprinted lenses than non-imprinted lenses and eye drops, respectively. The results indicate that molecular imprinting provides an exciting rational engineering strategy for sustained release. It is clear that imprinted lenses are very promising combination devices and are much more effective and efficient delivery devices than eye drops.     

Use of a contact lens telescopic system in low vision patients.

This study was designed to evaluate the effectiveness of a contact lens telescopic system in patients diagnosed with low vision. Fifteen white patients (mean age 60.7 years) with visual acuity between 20/60 and 20/400 (mean 20/245) were evaluated using first a conventional telescope and subsequently a contact lens telescope (CLT). Evaluation parameters were visual acuity, amplitude of visual field, and patients' satisfaction with the systems. The mean final visual acuity attained with both systems was 20/105. No differences in visual acuity between the two systems were detected. However, the visual field was significantly different with each system. Mean visual field with the conventional telescope was 22 degrees, whereas with the CLT it was 52.1 degrees. This corresponds to a reduction of 78.2% in the field of view with the conventional telescope and of 49.5% with the CLT. Therefore, the CLT was found to provide a field of view that is 136% as great as the one provided by the conventional telescope. Younger patients are specially enthusiastic about the CLT because of its improved cosmetic appearance and visual field as compared to traditional telescopes. Aged patients tend to have more difficulty in accepting and using contact lenses daily.     

Nacken-Schulter-Beschwerden am Bildschirmarbeitsplatz

Purpose

In subjects at visual display unit (VDU) work places (>?4 h daily) with neck and shoulder complaints the eye-head movement and its influence through a multifocal lens design was examined.

Materials and methods

The eye-head movement (head-eye mover ratio horizontal) was determined in 100 presbyopic subjects with the Vision Print® (Essilor). The subjects were randomized and single-blind divided into three different interventions, group I head mover, group II eye mover design, group III near work design and a control group with no intervention.

Results

A work station in presbyopic subjects with neck-shoulder discomfort seems to contribute to the manifestation of a pathological stereotype (eye mover) in the horizontal gaze shift. By using multifocal spectacle lenses a significant reduction in complaints in the shoulder and neck area was found for the groups I, II and III. The change of the head-eye mover ratio (horizontal) in the direction of increased head movement was tendentially shown in the treatment groups but not for the control group. The influence of the eye-head movement in the vertical direction was not investigated.

Conclusions

If optometric treatment is required (single or multifocal glasses) for a patient with neck and shoulder complaints a modification of the work place and the spectacles used is necessary before a therapeutic intervention and not vice versa. Concomitant to this a consultation for movement stimulating working conditions must take place.