Biometry of eyes in type 1 diabetes

This is a comprehensive study of a large range of biometric and optical parameters in people with type 1 diabetes. The parameters of 74 people with type 1 diabetes and an age matched control group were assessed. Most of the people with diabetes had low levels of neuropathy, retinopathy and nephropathy. Marginal or no significant differences were found between groups for corneal shape, corneal thickness, pupil size, and pupil decentrations. Relative to the control group, the diabetes group demonstrated smaller anterior chamber depths, more curved lenses, greater lens thickness and lower lens equivalent refractive index. While the optics of diabetic eyes make them appear as older eyes than those of people of the same age without diabetes, the differences did not increase significantly with age. Age-related changes in the optics of the eyes of people with diabetes need not be accelerated if the diabetes is well controlled.OCIS codes: (330.4875) Optics of physiological systems, (330.7329) Visual optics, pathology     

Measurement of ocular aberrations in downward gaze using a modified clinical aberrometer

Changes in corneal optics have been measured after downward gaze. However, ocular aberrations during downward gaze have not been previously measured. A commercial Shack-Hartmann aberrometer (COAS-HD) was modified by adding a relay lens system and a rotatable beam splitter to allow on-axis aberration measurements in primary gaze and downward gaze with binocular fixation. Measurements with the modified aberrometer (COAS-HD relay system) in primary and downward gaze were validated against a conventional aberrometer. In human eyes, there were significant changes (p<0.05) in defocus C(2,0), primary astigmatism C(2,2) and vertical coma C(3,-1) in downward gaze (25 degrees) compared to primary gaze, indicating the potential influence of biomechanical forces on the optics of the eye in downward gaze. To demonstrate a further clinical application of this modified aberrometer, we measured ocular aberrations when wearing a progressive addition lens (PAL) in primary gaze (0 degree), 15 degrees downward gaze and 25 degrees downward gaze.     

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     

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     

Secoisolariciresinol diglucoside from flaxseed delays the development of type 2 diabetes in Zucker rat.

Previous research has suggested that type 1 diabetes mellitus may be due to oxidative stress. The role of oxidative stress in type 2 diabetes is not known. Secoisolariciresinol diglucoside (SDG) antioxidant, obtained from flaxseed, has been reported to prevent type 1 diabetes in a rat model. However, its effectiveness in type 2 diabetes is not known. An investigation was made of the effects of SDG isolated from flaxseed (40 mg/kg body wt, orally in drinking water) on the development of diabetes in Zucker diabetic fatty (ZDF)/Gmi-fa/fa female rats, a model of human type 2 diabetes, to determine whether this type of diabetes is due to oxidative stress and whether SDG could prevent the development of diabetes. A total of 10 Zucker lean control and 26 ZDF rats were used in this study. Incidence of diabetes was 100% in untreated and 20% in SDG-treated ZDF rats by the age of 72 days (P <.01). The rats that did not develop diabetes by 72 days of age in the SDG-treated group developed diabetes later on (age 72 to 99 days) except for 10% of the rats that did not develop diabetes for the duration of the study (101 days of age), suggesting that SDG retarded the development of diabetes. Diabetes was associated with an increase in oxidative stress as suggested by an increase in serum malondialdehyde (P <.01). Also, diabetes was associated with an increase in serum total cholesterol and triglycerides (P <.05) and glycated hemoglobin A(1C) (P <.05). ZDF rats treated with SDG that did not develop diabetes by 70 days of age had no increase in oxidative stress, serum total cholesterol, and glycated hemoglobin. These results suggest that type 2 diabetes is associated with an increase in oxidative stress and that SDG is effective in retarding the development of diabetes.     

截平稳定型散光角膜接触镜对顺规散光青少年眼表的影响

目的研究截平稳定型散光角膜接触镜对顺规散光青少年眼表的影响。方法对临床确定为顺规散光的青少年患者(除外其他任何眼病)进行检影及电脑验光,按结果分为低、中、高度散光组,再将各组分为实验组和对照组两组,实验组佩戴截平稳定型散光角膜接触镜,对照组佩戴框架眼镜。分别对其进行0个月、1个月、3个月、6个月时的泪膜破裂时间(BUT)、基础泪液分泌实验(Sit)、角膜荧光染色、下睑中央泪河高度测量、角膜曲率检查。对比观察各组结果。结果①实验组较对照组患者眼表泪膜稳定性明显下降,尤以高度散光组为著(P<0.05)。②随着时间的推移,实验组患者眼表泪膜稳定性下降明显(P<0.05)。结论随著散光度的增加和佩戴时间的延长,截平稳定型散光角膜接触镜可明显影响青少年佩戴者眼表结构和功能。     

Adaptive optics with pupil tracking for high resolution retinal imaging

Adaptive optics, when integrated into retinal imaging systems, compensates for rapidly changing ocular aberrations in real time and results in improved high resolution images that reveal the photoreceptor mosaic. Imaging the retina at high resolution has numerous potential medical applications, and yet for the development of commercial products that can be used in the clinic, the complexity and high cost of the present research systems have to be addressed. We present a new method to control the deformable mirror in real time based on pupil tracking measurements which uses the default camera for the alignment of the eye in the retinal imaging system and requires no extra cost or hardware. We also present the first experiments done with a compact adaptive optics flood illumination fundus camera where it was possible to compensate for the higher order aberrations of a moving model eye and in vivo in real time based on pupil tracking measurements, without the real time contribution of a wavefront sensor. As an outcome of this research, we showed that pupil tracking can be effectively used as a low cost and practical adaptive optics tool for high resolution retinal imaging because eye movements constitute an important part of the ocular wavefront dynamics.OCIS codes: (110.1080) Active or adaptive optics, (100.4999) Pattern recognition, target tracking, (170.4460) Ophthalmic optics and devices, (170.3890) Medical optics instrumentation     

Binocular visual performance and summation after correcting higher order aberrations

Although the ocular higher order aberrations degrade the retinal image substantially, most studies have investigated their effect on vision only under monocular conditions. Here, we have investigated the impact of binocular higher order aberration correction on visual performance and binocular summation by constructing a binocular adaptive optics (AO) vision simulator. Binocular monochromatic aberration correction using AO improved visual acuity and contrast sensitivity significantly. The improvement however, differed from that achieved under monocular viewing. At high spatial frequency (24 c/deg), the monocular benefit in contrast sensitivity was significantly larger than the benefit achieved binocularly. In addition, binocular summation for higher spatial frequencies was the largest in the presence of subject’s native higher order aberrations and was reduced when these aberrations were corrected. This study thus demonstrates the vast potential of binocular AO vision testing in understanding the impact of ocular optics on habitual binocular vision.OCIS codes: (330.0330) Vision, color, and visual optics; (330.1400) Vision - binocular and stereopsis; (330.4300) Vision system - noninvasive assessment; (330.4595) Optical effects on vision; (330.4460) Ophthalmic optics and devices; (330.7327) Visual optics, ophthalmic instrumentation     

Vascular compliance is reduced in the early stages of type 1 diabetes.

OBJECTIVE: To determine whether arterial compliance of patients with type 1 diabetes is reduced before the development of clinically apparent diabetes complications. RESEARCH DESIGN AND METHODS: Pulse-wave analysis was used to compare vascular compliance between patients with type 1 diabetes and nondiabetic control subjects. Analysis of covariance was used to determine differences between the two groups with adjustment for age if needed. RESULTS: A total of 59 patients with type 1 diabetes were studied; age ranged from 17-61 years. Of the 59 patients, 32 had no evidence of diabetes complications and 27 had microvascular complications. The control group consisted of 57 healthy subjects ranging in age from 23-79 years. In the control group, large artery compliance (C1) and small artery compliance (C2) were inversely proportional to age (r = -0.55 for C1 and -0.50 for C2; P < 0.01). When the control subjects were compared with type 1 diabetic patients without microvascular complications, C1 was 1.51 +/- 0.04 (SEM) for the control group and 1.33 +/- 0.06 (SE) ml/mmHg for the diabetic group, whereas C2 was 0.080 +/- 0.005 (SE) and 0.065 +/- 0.005 (SE) ml/mmHg for the control and diabetic subjects, respectively, when adjusted for age (P = 0.03 for both C1 and C2). CONCLUSIONS: Vascular compliance of both the large and small arteries is reduced in type 1 diabetic patients before any clinical complications from the diabetes are evident. This study serves to emphasize that vascular changes occur at an early point in the disease and may increase risk of cardiovascular events in patients with diabetes. Larger prospective studies are required to confirm this finding and to investigate the efficacy of medical intervention.     

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     

Non-common path aberration correction in an adaptive optics scanning ophthalmoscope

The correction of non-common path aberrations (NCPAs) between the imaging and wavefront sensing channel in a confocal scanning adaptive optics ophthalmoscope is demonstrated. NCPA correction is achieved by maximizing an image sharpness metric while the confocal detection aperture is temporarily removed, effectively minimizing the monochromatic aberrations in the illumination path of the imaging channel. Comparison of NCPA estimated using zonal and modal orthogonal wavefront corrector bases provided wavefronts that differ by ~λ/20 in root-mean-squared (~λ/30 standard deviation). Sequential insertion of a cylindrical lens in the illumination and light collection paths of the imaging channel was used to compare image resolution after changing the wavefront correction to maximize image sharpness and intensity metrics. Finally, the NCPA correction was incorporated into the closed-loop adaptive optics control by biasing the wavefront sensor signals without reducing its bandwidth.OCIS codes: (110.1080) Active or adaptive optics, (170.4460) Ophthalmic optics and devices     

Association of CTLA-4 gene A/G polymorphism in Japanese type 1 diabetic patients with younger age of onset and autoimmune thyroid disease

OBJECTIVE: We studied the association between type 1 diabetes with autoimmune thyroid disease (AITD) and A/G allele polymorphism in exon 1 of the CTLA-4 gene in a Japanese population. RESEARCH DESIGN AND METHODS: We studied 74 Japanese type 1 diabetic patients with or without AITD and 107 normal subjects to identify the association between CTLA-4 polymorphism and type 1 diabetes using polymerase chain reaction-restriction fragment length polymorphism analysis. RESULTS: The frequency of the CTLA-4 G allele differed significantly between the type 1 diabetic patients (61%) and the normal control subjects (48%) (P = 0.016). The difference in the CTLA-4 G allele became greater between patients with a younger age of onset of type 1 diabetes (age at onset <30 years) and the normal control subjects (64% and 48%, respectively). However, the frequency of the CTLA-4 G allele did not differ between type 1 diabetic patients with younger and older age of onset (64% vs. 57%). The G allele frequencies in the patients with younger-onset type 1 diabetes and AITD increased more than in the control patients (P = 0.025). These differences reflected a significant increase in the frequency of G/G genotype--that is, 54% in those with younger-onset type 1 diabetes and AITD, 39% in those without AITD, and 28% in control subjects. CONCLUSIONS: An association was detected between the CTLA-4 gene polymorphism and younger-onset type 1 diabetes with AITD. The G variant was suggested to be genetically linked to AITD-associated type 1 diabetes of younger onset in this apanese population. The defect in these patients presumably lies in a T-cell-mediated autoimmune mechanism.     

Alteration in refractive index profile during accommodation based on mechanical modelling

The lens of the eye has a gradient refractive index (GRIN). Ocular accommodation, which alters the shape of the lens in response to visual demand, causes a redistribution of the internal structure of the lens leading to a change in the GRIN profile. The nature of this redistribution and the consequence of change in the GRIN profile are not understood. A modelling approach that considers how the GRIN profile may change with accommodation needs to take into account optical and mechanical parameters and be cognisant of individual variability in the shape and size of lenses. This study models the normalised axial GRIN profile during accommodation using reduced modelling and incorporating finite element analysis to connect inhomogenous mechanical characteristics of the lens to optical performance. The results show that simulated stretching changes the length of the plateau but does not alter the cortical gradient, which supports clinical findings. There is a very small change to the accommodated and non-accommodated profiles when normalised, yet this yields measurable changes in aberrations with around 11% and almost 13% difference in spherical aberration and astigmatism respectively. The results can be used in reconstruction of the refractive index and for investigating gradual changes with age.OCIS codes: (110.2760) Gradient-index lenses, (330.7322) Visual optics, accommodation, (330.7326) Visual optics, modeling     

Short- and long-term effects of real-time continuous glucose monitoring in patients with type 2 diabetes

OBJECTIVE

To determine whether short-time, real-time continuous glucose monitoring (RT-CGM) has long-term salutary glycemic effects in patients with type 2 diabetes who are not on prandial insulin.

RESEARCH DESIGN AND METHODS

This was a randomized controlled trial of 100 adults with type 2 diabetes who were not on prandial insulin. This study compared the effects of 12 weeks of intermittent RT-CGM with self-monitoring of blood glucose (SMBG) on glycemic control over a 40-week follow-up period. Subjects received diabetes care from their regular provider without therapeutic intervention from the study team.

RESULTS

There was a significant difference in A1C at the end of the 3-month active intervention that was sustained during the follow-up period. The mean, unadjusted A1C decreased by 1.0, 1.2, 0.8, and 0.8% in the RT-CGM group vs. 0.5, 0.5, 0.5, and 0.2% in the SMBG group at 12, 24, 38, and 52 weeks, respectively (P = 0.04). There was a significantly greater decline in A1C over the course of the study for the RT-CGM group than for the SMBG group, after adjusting for covariates (P < 0.0001). The subjects who used RT-CGM per protocol (≥48 days) improved the most (P < 0.0001). The improvement in the RT-CGM group occurred without a greater intensification of medication compared with those in the SMBG group.

CONCLUSIONS

Subjects with type 2 diabetes not on prandial insulin who used RT-CGM intermittently for 12 weeks significantly improved glycemic control at 12 weeks and sustained the improvement without RT-CGM during the 40-week follow-up period, compared with those who used only SMBG.The prevalence of diabetes is projected to rise from the current 11% of the U.S. population aged ≥20 years (1) to as much as 33% by 2050 (2). Those with type 2 diabetes represent ~90% of all people with diabetes. Poor glycemic control remains a problem for many people. Forty-four percent of people with type 2 diabetes have a hemoglobin A1C higher than the generally accepted target for most patients of 7% (3). Despite the emergence of several new classes of pharmacologic agents, the introduction of medication-use guidelines and algorithms by major professional organizations (4–6), the improvement in the quality and user-friendliness of devices for self-monitoring of blood glucose (SMBG), and the development of numerous care- and self-management tools for providers and patients that provide some decision support and facilitate the sharing of information, a significant number of type 2 diabetic subjects remain suboptimally controlled. This state of affairs suggests the need for additional approaches to glycemic management for people with type 2 diabetes. Such an approach might be real-time continuous glucose monitoring (RT-CGM).RT-CGM provides patients with a glucose reading every 5 min, typically on a visual display that shows the glucose trend and whether it is above, below, or within preset ranges. RT-CGM has been shown to improve glycemic control and/or reduce the frequency of hypoglycemic episodes in pediatric and adult patients with type 1 diabetes and in adult patients with type 2 diabetes taking prandial insulin (7–14), although age and frequency of sensor use affect the magnitude of the A1C reduction (15). RT-CGM has not been used as a tool for diabetes management in patients with type 2 diabetes who are not taking prandial insulin, by far the largest subgroup of people with type 2 diabetes. Their glycemic monitoring relies on SMBG at a frequency and time of day commensurate with their treatment regimen.We sought to determine whether RT-CGM could play an adjunctive role in the management of patients with type 2 diabetes who are not on prandial insulin. The rationale for this investigation was that the volume of information from RT-CGM and the visual display of that information as a trend could provide important feedback to participants on their glucose status. We recently reported that RT-CGM over 12 weeks was associated with a clinically significant reduction in A1C (1.0%) over the same period of time compared with SMBG before meals and before bedtime (0.5%) (16). We now report the legacy effects of this 12-week intervention on glycemic control and other diabetes-related outcomes in the same cohort over a total of 52 weeks.     

The aging eye. A family physician discusses some inevitable changes and suggests methods for dealing with them

The aging eye undergoes a variety of structural and physiologic changes that can impair vision and cause functional disability. Among the changes are backward displacement of the eye into the orbit, thickening and yellowing of the lens, decrease in pupil size, increase in laxity of the lids, and accumulation of waste products in the retina. The specific diseases of the eye that occur with aging include macular degeneration, cataracts, glaucoma, diabetic retinopathy, and sudden vision loss. Preventive care both in old age and earlier in life may help forestall ocular changes and the subsequent morbidity and mortality they cause. Environmental changes to accommodate visual change can be important in accident prevention and in improved functioning and quality of life.     

Diabetes knowledge and glycemic control among Chinese people with type 2 diabetes

BACKGROUND: Diabetes self-management education (DSME) is a key component of effective glycemic control and an important part of clinical diabetes management. The effects of DSME in China have not been investigated. OBJECTIVES: To identify factors that could enhance the quality of Chinese DSME programmes. The relationship between patients' diabetes knowledge and their glycemic control was explored. METHODS: A non-experimental cross-sectional study was undertaken in a large Shanghai hospital in China. Forty inpatients and 60 outpatients with type 2 diabetes mellitus were recruited. A Chinese version of the Diabetes Knowledge Scale was used to assess subjects' diabetes knowledge and collect demographic data and HbA1c levels. RESULTS: The mean diabetes knowledge scores among Chinese with type 2 diabetes was 22.1 +/- 3.76 out of a possible 30 marks. There was no difference in overall diabetes knowledge in people with HbA1c <7%, indicating good control and those with HbA1c >or=7%, indicating suboptimal glycemic control (t = -0.811, P = 0.419). However, there were differences in scores between the two groups for some specific questions on sick day management and food substitution. Moreover, sociodemographic characteristics such as age and occupation were significantly correlated with diabetes knowledge; age was negatively correlated with diabetes knowledge and white-collar workers had the highest mean knowledge score and housewives the lowest. CONCLUSION: Sociodemographic characteristics need to be considered when developing diabetes self-management programmes for Chinese people with type 2 diabetes.     

2型糖尿病患者糖原合成酶激酶3β的表达及活性

目的 探讨糖原合成酶激酶3β(GSK-3β)在2型糖尿病患者和健康者外周血单个核细胞中的蛋白表达及活性水平。方法 运用酶联免疫吸附法(ELISA)检测30例2型糖尿病血糖未控制患者(实验1组)、30例2型糖尿病血糖控制患者(实验2组)和30例健康者(健康对照组)外周血单个有核细胞GSK-3β蛋白表达及活性水平,并分析其结果。结果2型糖尿病患者GSK-3β蛋白水平比健康对照组升高(P0.05),实验1组GSK-3β活性水平比健康对照组和实验2组升高(P0.05);实验2组GSK-3β蛋白水平比健康对照组升高(P0.05)。实验1组男性GSK-3β活性水平比健康对照组男性升高(P0.05)。结论 2型糖尿病患者GSK-3β蛋白高表达。经药物治疗后血糖控制者GSK-3β蛋白仍高表达,但活性水平明显下降。2型糖尿病血糖未控制男性患者GSK-3β活性水平明显增高。     

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     

Temporal integration property of stereopsis after higher-order aberration correction

Based on a binocular adaptive optics visual simulator, we investigated the effect of higher-order aberration correction on the temporal integration property of stereopsis. Stereo threshold for line stimuli, viewed in 550nm monochromatic light, was measured as a function of exposure duration, with higher-order aberrations uncorrected, binocularly corrected or monocularly corrected. Under all optical conditions, stereo threshold decreased with increasing exposure duration until a steady-state threshold was reached. The critical duration was determined by a quadratic summation model and the high goodness of fit suggested this model was reasonable. For normal subjects, the slope for stereo threshold versus exposure duration was about −0.5 on logarithmic coordinates, and the critical duration was about 200 ms. Both the slope and the critical duration were independent of the optical condition of the eye, showing no significant effect of higher-order aberration correction on the temporal integration property of stereopsis.OCIS codes: (330.0330) Vision, color, and visual optics; (330.4595) Optical effects on vision; (330.1400) Vision - binocular and stereopsis     

Woofer-tweeter adaptive optics scanning laser ophthalmoscopic imaging based on Lagrange-multiplier damped least-squares algorithm

We implemented a Lagrange-multiplier (LM)-based damped least-squares (DLS) control algorithm in a woofer-tweeter dual deformable-mirror (DM) adaptive optics scanning laser ophthalmoscope (AOSLO). The algorithm uses data from a single Shack-Hartmann wavefront sensor to simultaneously correct large-amplitude low-order aberrations by a woofer DM and small-amplitude higher-order aberrations by a tweeter DM. We measured the in vivo performance of high resolution retinal imaging with the dual DM AOSLO. We compared the simultaneous LM-based DLS dual DM controller with both single DM controller, and a successive dual DM controller. We evaluated performance using both wavefront (RMS) and image quality metrics including brightness and power spectrum. The simultaneous LM-based dual DM AO can consistently provide near diffraction-limited in vivo routine imaging of human retina.