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Purpose To explore the correlation between longitudinal changes of peripapillary retinal nerve fiber layer (RNFL) thickness and the presence of parapapillary choroidal microvasculature dropout (MvD). Methods This is a longitudinal cohort study. All patients with normal-tension glaucoma (NTG) were recruited from the Wenzhou Glaucoma Progression Study. The presence of MvD was determined using optical coherence tomography (OCT) angiography and the RNFL thickness was evaluated by spectral-domain OCT. All assessments were performed both at baseline and at every 3-month follow-up for at least 18 months. Results Seventy-one eyes were included. The presence of MvD was observed in 23 NTG eyes (32.4%). Eyes with MvD had a thinner RNFL (68.8 ± 9.6 vs. 76.2 ± 16.7 μm, P = 0.016) and a faster rate of RNFL loss (-1.2 ± 1.5 vs. -0.4 ± 1.4 μm/y, P = 0.036) compared with those without MvD. In a univariate analysis of rates of RNFL loss, the presence of MvD at baseline (β = -0.83 ± 0.38, P = 0.033) was significantly associated with progressive RNFL loss. After adjusting for age, female sex, mean follow-up IOP, axial length, central corneal thickness, and mean deviation, the presence of MvD at baseline (β = -0.85 ± 0.41, P = 0.041) was significantly associated with faster rates of RNFL loss in the multivariate analysis. Conclusions There is a significant correlation between the presence of MvD and decrease in RNFL thickness in NTG patients. Our study further supported that the presence of MvD is a predictor of longitudinal RNFL damage in glaucoma.

To investigate regional alterations of macular microvasculature in primary open-angle glaucoma (POAG), and to determine the structure-function correlation between localized visual field defects and macular microvascular damage in matching sectors.Fifty-eight patients with POAG and 27 normal controls were recruited for this study. Optical coherence tomography angiography (OCTA) was used to measure retinal vascular microcirculation of the macula in superior, inferior, temporal, and nasal sectors. Visual field (VF) was tested using automated perimeter. Sensitivities of 16 central points of the VF were selected and divided into the 4 previously mentioned sectors. Structure-function correlation analysis was performed between localized visual field defects and the matching macular microvasculature damage. The relationship was also assessed using a previously described model.The temporal vascular density was thinner than those of the superior and inferior positions of parafovea in the control group (P 0.05). Vascular densities in all sectors were decreased in the POAG group compared with the normal control group (P 0.05). The structure-function correlation coefficients between sectors of VF sensitivity and the matched vascular densities ranged from 0.295 to 0.433 (P 0.01). The coefficient of determination between OCT derived vascular density measurements and the estimates using the previous model ranged from 0.08 to 0.19. The best fit was in the inferior sector.Compared with age-matched control subjects, vascular density of the parafoveal retina decreased in the POAG subjects. There is a moderate structure-function correlation between visual field sensitivity thresholds measured with automated perimeter and macular vascular density assessed by OCT.

Background Spectral domain optical coherence tomography (SD-OCT) was a useful tool to study accommodation in human eye, but the maximum image depth is limited due to the decreased signal-to-noise ratio (SNR). In this study, improving optical resolutions, speeds and the SNR were achieved by custom built SD-OCT, and the evaluation of the impact of the improvement during accommodation was investigated. Methods Three systems with different spectrometer designs, including two Charge Coupled Device (CCD) cameras and one Complementary Metal-Oxide-Semiconductor Transistor (CMOS) camera, were tested. We measured the point spread functions of a mirror at different positions to obtain the axial resolution and the SNR of three OCT systems powered with a light source with a 50 nm bandwidth, centered at a wavelength of 840 nm. Two normal subjects, aged 26 and 47, respectively, and one 75-year-old patient with an intraocular lens implanted were imaged. Results The results indicated that spectrometers using cameras with 4096 camera pixels optimized the axial resolutions, due to the use of the full spectrum provided by the light source. The CCD camera system with 4096 pixels had the highest SNR and the best image quality. The system with the CMOS camera with 4096 pixels had the highest speed but had a compromised SNR compared to the CCD camera with 4096 pixels. Conclusions Using these three OCT systems, we imaged the anterior segment of the human eye before and after accommodation, which showed similar results among the different systems. The system using the CMOS camera with an ultra-long scan depth, high resolution and high scan speed exhibited the best overall performance and therefore was recommended for imaging real-time accommodation.

Background To investigate thickness changes in the corneal epithelium and Bowman’s layer after overnight silicone hydrogel contact lens (CL) wear by using ultra-high resolution optical coherence tomography (UHROCT). Methods Eleven subjects without CL wearing history were recruited for this study. An UHROCT was used to measure the thickness of the epithelium (ET), Bowman’s layer (BT), stroma (ST), and total cornea (CCT) at the center of both eyes. A silicone hydrogel CL was inserted in the right eye of each subject, and the fellow non-CL wearing left eye served as the control. The lens was inserted at 9:30 pm and removed at 8:00 am the next morning. The subjects were evaluated at 9:00 pm (baseline), 9:30 pm (lens insertion), 10:00 pm (before sleep), 7:00 am (waking), 7:30 am, and 8:00 am (lens removal). Results Compared to the lens insertion level, the ET of the lens-wearing eye increased by 5.73% at eye opening (P = 0.001). The ET of the non-CL wearing eye and the BT in both eyes did not change after overnight CL wear. Compared to baseline, the CCT of the lens-wearing eye increased by 2.87% upon waking (P = 0.003) and recovered 30 min later (P = 0.555). In contrast, compared to baseline, the CCT of the non-CL wearing eye did not increase upon waking (P = 0.105). Conclusions By using UHROCT, we found that overnight CL wear induced different swelling responses in the various sublayers of the cornea. Trial registration Retrospectively registered. Registration number: ChiCTR1800015115. Registered 07 March 2018.

The goal was to determine the variability of the quantitative measurement of the bulbar conjunctival microvascular morphology and hemodynamics by testing the repeatability and variation during office hours. Functional slit-lamp biomicroscopy (FSLB) was used to image the bulbar conjunctival microvasculature, including the vessel diameter, blood flow velocity/rate and fractal dimensions of the microvascular network. The temporal side of the bulbar conjunctiva in 20 healthy subjects was imaged. The subject was imaged at 9 AM to test the measurement repeatability by two independent graders. The intraclass correlation coefficient (ICC) and coefficient of repeatability (CoR) were calculated. These same subjects were then imaged every two hours from 9 AM to 5 PM to test the variation during office hours. Custom software was used to semi-automatically process all measurements. The CoR% and ICC values between two graders for measuring the vessel diameter were 4.87% and 0.989, respectively. For the axial blood flow velocity, the CoR% and ICC were 11.49% and 0.997, respectively. From 9 AM to 5 PM, there were no significant variations in the vessel diameter and hemodynamics (P>0.05), whereas the fractal dimensions of the non-invasive microvascular perfusion maps (nMPMs) were significantly increased at 3 PM and 5 PM compared with the baseline obtained at 9 AM (P

Contemporary and classic theories for the accommodative mechanism are based on the concept that the contraction of the ciliary muscle is the initial event that leads to the reshaping of the crystalline lens, an idea initially developed by von Helmholtz.1 The key elements of accommodation, such as the elasticity of the crystalline lens and the activity of the ciliary muscle, decline with age, which degenerates the capacity of accommodation.2–7 Restoring the accommodative ability has been a substantial challenge. The implantation of accommodating intraocular lenses (AIOL) has been shown to restore less than 2 diopters (D) of objective accommodation,8,9 partly due to the difficulty in predicting the dynamic response of the accommodative apparatus during accommodation. The dynamic relationship between ciliary muscle contraction and its ability to reshape the crystalline lens during the real-time processes of the human eye has not been fully studied in vivo, which may further limit the improvements in the restoration of accommodation. Hess10 and Gullstrand11 developed a lenticular theory, which stated that presbyopia was caused by a decrease in the lens reshaping capacity. The ciliary muscle normally contracts in the region where the lens still is capable of a response, but it cannot produce an accommodative response above this level due to the lens hardness, even though muscle still is capable of contracting. In contrast, the extralenticular theory of Duane12,13 showed that a slight weakening of the ciliary muscle decreased the accommodative amplitude. Fincham14,15 proposed a reconciliation of these two extremes, suggesting that the lens is responsible primarily for the loss of accommodation and that the contraction of the ciliary muscle required for lens reshaping increases with age. Although these early theories all predict the age-related changes in muscle-lens relationship, none of them is fully supported. The in vivo assessment of the dynamic response of the crystalline lens to ciliary muscle contraction is critical to understand the mechanism of accommodation and the age-related decline of accommodation. The difficulty in simultaneously imaging the entire anterior segment, including the crystalline lens and ciliary muscle, has limited in vivo studies of accommodation. In nonhuman primate models with iridectomies, the movement of ciliary processes and the lens equator during accommodation has been visualized using goniovideography under the stimulation of the Edinger-Westphal nucleus.16,17 This method may not be applicable to human subjects. Others have used magnetic resonance imaging (MRI), which allows the entire eye (including the ciliary muscle and entire lens) to be imaged, to visualize accommodation.18,19 The low scanning speed limits the application of dynamic measurements in accommodation research. To date, to our knowledge no study has simultaneously assessed the biometric changes in the ciliary muscle and crystalline lens as the function of age in real time in a cohort of human subjects. Optical coherence tomography (OCT) allows the noninvasive and rapid imaging of the ocular anterior segment in the static and dynamic states.20–28 Previously, we developed a system that combined two spectral-domain OCT (SD-OCT) devices.27 One has extended the scan depth to approximately 12 mm in air for the imaging of the entire anterior segment through the pupil, while the other was equipped with a light source that was centered at a wavelength of 1310 nm to image the ciliary muscle in real time. The objective of this study was to investigate the age-related changes in the dynamic responses of human accommodative elements, and the relationship between lens reshaping and muscle contraction during accommodation using the synchronized SD-OCT system.