Using Ultra-high Resolution Optical Coherence Tomography Research Articles

Effects of Medium-Term Soft Contact Lens Fitting on Dry Eye: Analyses Using Ultra-High Resolution Optical Coherence Tomography and Digital Slit-Lamp Biomicroscopy.

Purpose This study aimed to evaluate the medium-term fit of soft contact lenses (SCLs) and its effects on dry eye by using ultra-high-resolution optical coherence tomography (UHR-OCT) and digital slit-lamp biomicroscopy (DSLB) and identify factors indicating a better contact lens fit. Methods A total of 14 participants (7 men, 7 women; mean age, 23.1 years) were recruited. Temporal lag and conjunctival coverage were imaged by UHR-OCT. DSLB was used to assess lens decentration and blink-induced movement. In addition, dry eye indices, including ocular surface disease index (OSDI), tear break-up time (TBUT), and Schirmer I test scores, were measured at baseline and 1 day, 1 week, 1 month, 3 months, and 6 months after wearing. Results Good repeatability was found in the assessments of lens fit characteristics by two researchers and in the assessments by one researcher at different follow-up times. There were no significant differences in lens fit characteristics, TBUT and Schirmer I test scores at each checkpoint (P >0.05). However, the OSDI was significantly higher than baseline after wearing (P <0.05). Changes in the temporal lag were positively correlated with changes in TBUT (r =0.544, P =0.044) and negatively correlated with changes in OSDI (r = -0.629, P =0.016). Changes in blink-induced movement were positively correlated with changes in OSDI, Schirmer I test scores, and TBUT (P <0.05). Conclusions UHR-OCT and DSLB can be used to comprehensively and quantitatively evaluate SCL fit. Both the contact lenses and ocular surface conditions are almost stable within 6 months of SCL wear. Temporal lag and blink-induced movement have a strong correlation with dry eye parameters in SCL wearers.

Thickness changes in the corneal epithelium and Bowman\u2019s layer after overnight wear of silicone hydrogel contact lenses

BackgroundTo 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).MethodsEleven 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).ResultsCompared 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).ConclusionsBy using UHROCT, we found that overnight CL wear induced different swelling responses in the various sublayers of the cornea.Trial registrationRetrospectively registered. Registration number: ChiCTR1800015115. Registered 07 March 2018.

Characterization of Soft Contact Lens Edge Fitting during Daily Wear Using Ultrahigh-Resolution Optical Coherence Tomography.

Purpose To determine conjunctival overlap over the edge of soft contact lens and to visualize the peripheral postlens tear film (PoLTF) underneath soft contact lenses using ultrahigh-resolution optical coherence tomography (UHR-OCT). Methods Twenty participants (4 males and 16 females, 23.0 ± 3.7 years) were fitted with two different types of soft contact lenses randomly. The limbus with lens was imaged with the UHR-OCT at the horizontal meridian every two hours up to 6 hours during lens wear. The conjunctival overlap was ranked as the percentage of the edge covered by the conjunctiva. The frequency of occurrence for visualized peripheral PoLTF was determined. Results The average conjunctival overlaps at insertion were 49% and 73% for galyfilcon A and balafilcon A lenses and increased significantly to 84% and 90% by 6 hours of lens wear (P < 0.001). Lenses with rounded edges had more conjunctival overlap than the lenses with angled edges (P=0.014). There were significant decreases for PoLTF on the conjunctiva (P=0.014) and peripheral cornea (P=0.004) over the study period compared to insertion. The percentage of subjects with PoLTF on the conjunctiva (32.5%) and peripheral cornea (36%) were greater in subjects wearing balafilcon A lenses (P=0.017). Conclusions Increased conjunctival overlap over the lens edges and reduced PoLTF underneath the peripheral region of soft contact lenses were shown during lens daily wear. The lens edge configuration may play a role in conjunctival response and peripheral PoLTF.

Relationship between vessel diameter and depth measurements within the limbus using ultra-high resolution optical coherence tomography

PurposeTo establish a relationship between the diameter and depth position of vessels in the superior and inferior corneo-scleral limbus using ultra-high resolution optical coherence tomography (UHR-OCT). MethodsVolumetric OCT images of the superior and inferior limbus were acquired from 14 healthy subjects with a research-grade UHR-OCT system. Differences in vessel diameter and depth between superior and inferior limbus were analyzed using repeated measured ANOVA in SPSS and R. ResultsThe mean (± SD) superior and inferior diameters were 29±18μm and 24±18μm respectively, and the mean (± SD) superior and inferior depths were 177±109μm and 207±132μm respectively. The superior limbal vessels were larger than the inferior ones (RM-ANOVA, p=0.004), and the inferior limbal vessels were deeper than the superior vessels (RM-ANOVA, p=0.041). There was a positive linear association between limbal vessel depth and size within the superior and inferior limbus with Pearson correlation coefficients of 0.803 and 0.754, respectively. ConclusionThis study demonstrated that the UHR-OCT was capable of imaging morphometric characteristics such as the size and depth of vessels in the limbus. The results of this study suggest a difference in the size and depth of vessels across different positions of the limbus, which may be indicative of adaptations to chronic hypoxia caused by the covering of the superior limbus by the upper eyelid. UHR-OCT may be a useful tool to evaluate the effect of contact lenses on the microvascular properties within the limbus.

In Vivo Imaging and Morphometry of the Human Pre-Descemet's Layer and Endothelium With Ultrahigh-Resolution Optical Coherence Tomography.

To visualize in vivo and quantify the thickness of the posterior corneal layers: the acellular pre-Descemet's layer (PDL), Descemet's membrane (DM), and endothelium (END) in healthy subjects, using ultrahigh-resolution optical coherence tomography (UHR-OCT). A research-grade, 800-nm UHR-OCT system with 0.95-μm axial resolution in corneal tissue was used to image in vivo the posterior cornea in healthy subjects. The system offers approximately 98 dB sensitivity for 680 μW optical power incident on the cornea and 34,000 A-scans/s image acquisition rate. This study comprised 20 healthy subjects, aged 20 to 60 years. The thickness of the PDL, DM, and END layers was measured both with a custom, automatic segmentation algorithm and manually. The boundaries and structure of the posterior corneal layers were clearly visible in the UHR-OCT images. The average thickness was measured to be 6.6 ± 1.4 μm (PDL), 10.4 ± 2.9 μm (DM), and 4.8 ± 0.4 μm (END), which agrees well with published data from ex vivo studies. Both the END and DM thickness showed minor spatial variations, whereas the PDL showed up to 2× thickness change for different locations on the same cross-sectional corneal image or over the entire imaged region of the cornea. Our data indicate that all three layers of the posterior cornea can be clearly visualized in vivo and their thicknesses measured precisely with UHR-OCT. Although the PDL thickness showed large spatial variations, the thickness of the DM and END layers was consistent over the entire imaged region of the cornea.

Real-Time Monitoring of Suprachoroidal Space (SCS) Following SCS Injection Using Ultra-High Resolution Optical Coherence Tomography in Guinea Pig Eyes.

To monitor the change of suprachoroidal space (SCS) using ultra high resolution-optical coherence tomography (UHR-OCT) following SCS injection with different drug formulations. An amount of 10 or 20 μL of saline or indocyanine green (ICG) or triamcinolone acetonide (TA) suspension (40 or 80 mg/mL) was injected suprachoroidally into the guinea pig eye with a 30-gauge needle. Immediately after injection, the eyes were imaged by UHR-OCT from 60 minutes up to 24 hours. At each time point, the SCS area on each OCT cross-section was measured in pixels with Image J and the area change from the baselines was analyzed over time. A 20-μL injection produced 130% to 200% SCS expansion compared to a 10-μL injection for saline and TA suspension (P < 0.01). After SCS injection, the time that expansion persisted was formulation dependent. Thus, expansion in response to injection of TA suspension, ICG, and saline persisted for 24 hours, 180 minutes, and 60 minutes, respectively. Moreover, ICG injection produced a significantly larger area of distribution in the SCS than the TA suspension (0.626 vs. 0.275 cm(2), P < 0.0001). The SCS is expandable and can recover to preinjection status after injected fluid is cleared by physiological processes. The injection-induced SCS expansion is volume-dependent, and the drug/dye retained in the SCS is formulation-dependent. The current injection technique with a volume of 20 μL or less is well tolerated in guinea pig eyes.

Monitor corneal epithelial healing under bandage contact lens using ultrahigh-resolution optical coherence tomography after pterygium surgery.

To monitor corneal epithelial healing under bandage contact lens (BCL) using ultrahigh-resolution optical coherence tomography (UHR-OCT) after pterygium surgery. Thirty-nine eyes of 39 patients undergoing pterygium excision and conjunctival autografting were randomly allocated into 2 groups: 20 eyes were covered with silicone hydrogel BCLs at the end of surgery and 19 eyes served as a control. Ultrahigh-resolution optical coherence tomography scans of the cornea were performed sequentially at 1, 2, and 3 days, and then every other day until the end of re-epithelialization after surgery. Complete epithelial healing was verified with fluorescein staining examination after removal of BCLs. Postsurgery pain was evaluated using the visual analog scale. All BCLs were successfully fit without any contact lens-related complications. Ultrahigh-resolution optical coherence images clearly revealed the architectural features of postoperative cornea with BCL in situ and showed epithelial healing process. Ultrahigh-resolution optical coherence tomography imaging agreed with the fluorescein staining examinations in detecting corneal epithelial defect. Based on the assessment by UHR-OCT, the average time course of re-epithelialization in the BCL group was 3.9±1.2 days, whereas in the control group, it was 5.7±1.8 days (P=0.001). Visual analog scale scoring showed lower pain levels in the BCL group comparing with the control group at each point of time (all P<0.05). Ultrahigh-resolution optical coherence tomography is an excellent tool in monitoring corneal epithelial healing under BCLs and determining the appropriate time for lens removal. Silicone hydrogel BCL is recommended as an adjuvant therapy after pterygium surgery for its efficacy in improving re-epithelialization and postoperative comfort.

Non-invasive detection of early retinal neuronal degeneration by ultrahigh resolution optical coherence tomography.

Optical coherence tomography (OCT) has revolutionises the diagnosis of retinal disease based on the detection of microscopic rather than subcellular changes in retinal anatomy. However, currently the technique is limited to the detection of microscopic rather than subcellular changes in retinal anatomy. However, coherence based imaging is extremely sensitive to both changes in optical contrast and cellular events at the micrometer scale, and can generate subtle changes in the spectral content of the OCT image. Here we test the hypothesis that OCT image speckle (image texture) contains information regarding otherwise unresolvable features such as organelle changes arising in the early stages of neuronal degeneration. Using ultrahigh resolution (UHR) OCT imaging at 800 nm (spectral width 140 nm) we developed a robust method of OCT image analyses, based on spatial wavelet and texture-based parameterisation of the image speckle pattern. For the first time we show that this approach allows the non-invasive detection and quantification of early apoptotic changes in neurons within 30 min of neuronal trauma sufficient to result in apoptosis. We show a positive correlation between immunofluorescent labelling of mitochondria (a potential source of changes in cellular optical contrast) with changes in the texture of the OCT images of cultured neurons. Moreover, similar changes in optical contrast were also seen in the retinal ganglion cell- inner plexiform layer in retinal explants following optic nerve transection. The optical clarity of the explants was maintained throughout in the absence of histologically detectable change. Our data suggest that UHR OCT can be used for the non-invasive quantitative assessment of neuronal health, with a particular application to the assessment of early retinal disease.

Visualization of the Precorneal Tear Film Using Ultrahigh Resolution Optical Coherence Tomography in Dry Eye

To visualize the precorneal tear film (PCTF) in dry eye patients using ultrahigh resolution optical coherence tomography (UHR-OCT). A custom-built UHR-OCT with ultrahigh resolution (~3 μm) was used to image the PCTF at the vertical meridian. Eighteen right eyes of 18 previously diagnosed dry eye patients (9 men and 9 women, age, 47.8±20.7 years) with aqueous tear deficiency were studied. Images were taken during normal and delayed blinking. The visualized PCTF was measured directly. An indirect calculation was used to obtain the thickness in cases where the PCTF could not be visualized. During normal blinking, the PCTF was visualized in 5 of 18 eyes (27.8%) with an average PCTF thickness of 5.8 μm (SD, 1.3 μm). During delayed blinking, the PCTF was visualized in 11 eyes (61.1%) with a significantly increased average thickness of 7.3 μm (SD, 0.9 μm; P<0.05). The percent increase of the visualized PCTF thickness was higher during delayed blinking compared with normal blinking (χ test, P<0.05). The averaged PCTF was 4.4 μm during normal blinking, and the PCTF thickness was significantly increased to 6.6 μm (SD, 2.9 μm; P<0.05) during delayed blinking. We report the first visualization of PCTF in vivo in dry eye patients with UHR-OCT. Precorneal tear film can be directly visualized in some eyes during both normal and delayed blinking, and it seemed thicker during delayed blinking compared with normal blinking.

In Vivo Assessment of Thickness and Reflectivity in a Rat Outer Retinal Degeneration Model with Ultrahigh Resolution Optical Coherence Tomography

To provide in vivo quantitative assessment of sodium iodate-induced retinal damage in a rat model of outer retinal degeneration using ultrahigh resolution optical coherence tomography (UHR-OCT). Outer retinal degeneration was induced in four female Long Evans rats via tail vein injection of sodium iodate (40 mg/kg). Changes in the thickness and optical reflectivity of individual retinal layers were extracted using a semi-automatic segmentation algorithm and were assessed in vivo at 6 hours, days 1, 3, and 7, and up to 3 months post injection with UHR-OCT. Hematoxylin and eosin (H&E) histology was used to confirm the morphologic changes observed in the UHR-OCT images. UHR-OCT tomograms showed progressive structural damage in the rat retina over time, such as swelling, thinning, complete disintegration of individual retinal layers, and clustering of highly reflective cellular debris. Photoreceptor swelling was observed 6 hours after injection of sodium iodate, followed by progressive structural decomposition of the outer retina. At 3 months post injection, the outer retina was completely disintegrated, and the inner nuclear layer (INL) was in direct contact with the choroid. Changes in the reflectivity of individual retinal layers were observed over time and correlated well with the morphologic changes. UHR-OCT permits in vivo, noninvasive, longitudinal, quantitative assessment of the progressive changes in retinal morphology and optical reflectivity in a sodium iodate rodent model of outer retinal degeneration.

Three-dimensional, non-invasive, cross-sectional imaging of protein crystals using ultrahigh resolution optical coherence tomography

Micro-scale, non-invasive, three-dimensional cross-sectional imaging of protein crystals was successfully accomplished using ultra-high resolution optical coherence tomography (UHR-OCT) with low noise, Gaussian like supercontinuum. This technique facilitated visualization of protein crystals even those in medium that also contained substantial amounts of precipitates. We found the enhancement of the scattered signal from protein crystal by inclusion of agarose gel in the crystallization medium. Crystals of a protein and a salt in the same sample when visualized by UHR-OCT showed distinct physical characteristics, suggesting that protein and salt crystals may, in general, be distinguishable by UHR-OCT. UHR-OCT is a nondestructive and rapid method, which should therefore find use in automated systems designed to visualize crystals.

Quantitative analysis of the intraretinal layers and optic nerve head using ultra-high resolution optical coherence tomography

This study is designed to test the repeatability of the quantitative analysis of intraretinal layer thickness and cup-disc ratio of the optic nerve head using ultra-high resolution optical coherence tomography (UHR-OCT). Group A, containing 23 eyes of 12 healthy subjects, was imaged twice and group B, containing eight eyes of four subjects, was imaged three times. Intraretinal layers were segmented manually and the cup-to-disc ratio of the optic nerve head was analyzed. Custom-built automatic segmentation software was also used to segment a set of images for comparison. A total of nine intraretinal layers were visualized and extracted manually. With group A, the central foveal thickness was 186.4 ± 15.9 μm (mean ± SD). The average retinal thickness was 296.4 ± 21.3 μm. The best repeatability, obtained when two repeated scans were taken, was obtained for the outer nuclear layer followed by the ganglion cell layer, the inner nuclear layer, the retinal nerve fiber layer and the worst was obtained for the outer segment. The intraclass correlation ranged from 0.824 to 0.997. The coefficients of repeatability ranged from 3.24 to 18.3 μm, corresponding to 1.47% to 26.20%. With group B, high interclass correlations were found and the automatic segmentation results were compatible with the manual results. Our results indicated that more retinal features might be imageable using UHR-OCT.

Ultra-High Resolution Optical Coherence Tomography for Imaging the Anterior Segment of the Eye

Developments in optical coherence tomography (OCT) have expanded its clinical applications for ultra-high resolution imaging of the anterior segment of the human eye. This review presents the latest advances for imaging the anterior segment of the eye using ultra-high resolution OCT (UHR-OCT). Unique applications of UHR-OCT technology in clinical and basic scientific laboratory research are discussed and a summary of the results is provided. The authors focused on the use of UHR-OCT for imaging of tear dynamics, contact lens interactions with the corneal surface, and in vivo histological diagnosis of disorders of the cornea, as well as the future direction in this field.

Characterization of Soft Contact Lens Edge Fitting Using Ultra-High Resolution and Ultra-Long Scan Depth Optical Coherence Tomography

To characterize the edge fitting of soft contact lenses using ultra-high resolution optical coherence tomography (UHR-OCT) and ultra-long scan depth optical coherence tomography (UL-OCT). A total of 20 participants (11 men, 9 women; mean age, 32.3 years) were recruited. Four different types of soft contact lenses were randomly fitted to both eyes of each subject on two separate visits. After 30 minutes, the horizontal meridians of the corneal center, midperiphery, and limbus were imaged by UHR-OCT. UL-OCT imaged each lens in vitro and the ocular surface of a physical model eye. Angle-edged lenses had significantly less conjunctival buildup than did round-edged lenses (P = 0.008). Limbal post-lens tear film gaps were present in 42% of the eyes, with the round-edged lenses having the most at 68%. Similarly, post-lens tear film gaps at the corneal mid-periphery were present in 47% of all eyes, with the round-edged lens having the most at 75%. Mismatches between the lens and the ocular surface were simulated based on UL-OCT images of the in vitro lenses and the model eye. The existence of tear film gaps and touching points were predicted in the simulation. The soft contact lens edge fitting was characterized by the conjunctival buildup and tear film gaps. Different types of contact lenses presented different levels of conjunctival buildup as well as different frequencies of tear film gaps. The findings by UHR-OCT were predicted in the simulation by UL-OCT. The application of these new technologies may open new ways of designing lenses and evaluating their fit.

Ultra-high Resolution Optical Coherence Tomography Assessment of Photoreceptors in Retinitis Pigmentosa and Related Diseases

To assess photoreceptor integrity in patients with retinitis pigmentosa (RP) and related diseases using ultra-high resolution optical coherence tomography (UHR-OCT) and to correlate foveal photoreceptor loss with visual acuity. Observational case series. Nine eyes of nine patients with RP and related diseases were imaged with UHR-OCT at the ophthalmology clinic. Patients were diagnosed based on history, examination, fluorescein angiography, and electroretinography. Concurrently, 36 eyes of 36 normal subjects were imaged with UHR-OCT. Central foveal thickness (CFT) and foveal outer segment/pigment epithelium thickness (FOSPET) were defined and measured on UHR-OCT images in all subjects and were compared between the two groups using unpaired t tests. The two thickness measurements in RP patients were correlated with visual acuity using Pearson correlation and linear regression. UHR-OCT demonstrated macular photoreceptor thinning in all RP patients. The difference in CFT between RP patients and normal subjects was not statistically significant (P = .103), but the difference in FOSPET between the two groups was significant (P = .003). Visual acuity showed a fair correlation with CFT (Pearson r = -0.43, r(2) = 0.187, P = .245) and an excellent correlation with FOSPET (Pearson r = -0.942, r(2) = 0.887, P < .0001). In the current study using UHR-OCT, a new thickness measurement termed FOSPET is demonstrated to quantify photoreceptor loss. FOSPET was statistically thinner in patients with RP and related diseases than in normal eyes and showed correlation with logMAR visual acuity. FOSPET appears to be a probable predictor of visual acuity in RP.

Assessment of Central Visual Function in Stargardt’s Disease/Fundus Flavimaculatus with Ultrahigh-Resolution Optical Coherence Tomography

To assess photoreceptor morphology in patients with Stargardt's disease and fundus flavimaculatus using ultrahigh-resolution optical coherence tomography (UHR-OCT) and correlate it with visual acuity (VA). This was a prospective observational case series. Fourteen patients with Stargardt's disease (nine women, five men; average age, 39 years; range, 27-53) were examined. A clinically viable UHR-OCT system employing a new, compact titanium sapphire laser was used, enabling a 3-microm axial resolution in the retina. All patients received a full ophthalmic examination, including fluorescein angiography. Outcome was judged by central transverse photoreceptor loss, central foveal thickness, VA, central atrophy according to fluorescein angiography, and fundus autofluorescence. UHR-OCT was capable of visualizing and quantifying regions of central transverse photoreceptor (PR) loss. All Stargardt patients with central atrophy had a complete loss of the central photoreceptor layer in the foveal region (mean transverse photoreceptor loss, 4390 +/- 2270 microm; range, 530-9240 microm). Patients without clinically evident central atrophy had an intact photoreceptor layer centrally, but had small, focal parafoveal defects. A correlation was detected between VA and transverse PR loss (Spearman rho=-0.60, P=0.03), which was confirmed on logistic regression analysis (R2=0.49, P=0.0001). Central foveal thickness was reduced in patients with Stargardt's disease (85 +/- 40 microm; range, 58-280 microm). The correlation was statistically significant with VA (Spearman rho=0.43, P=0.04), but not with transverse PR loss (Spearman rho=-0.23, P >>0.05). Linear regression analysis showed a statistically significant association of central foveal thickness with VA (R2=0.51, P=0.0001), but not with transverse PR loss (P >>0.05). The extent of atrophy seen in fluorescein angiography correlated with VA and transverse PR loss (Spearman rho=-0.51, P=0.007; Spearman rho=0.77, P=0.0001). Similar correlations were found with the maximum transverse diameter of fundus autofluorescence (Spearman rho=-0.72, P=0.008; Spearman rho=0.77, P=0.003). Ultrahigh-resolution OCT demonstrates excellent visualization of intraretinal morphology and enables quantification of the photoreceptor layer. Thus, for the first time, an in vivo visualization and quantification of transverse, central photoreceptor loss and correlation with visual function is possible. Lower VA corresponds to a greater transverse photoreceptor loss, which also correlates with the extent of changes seen in fluorescein angiography and in fundus autofluorescence. Furthermore, reduced retinal thickness (i.e., atrophy of retinal layers) does not correlate with the transverse extent of PR loss. Thus, it seems that although there may be progressive atrophy of intraretinal layers, an intact photoreceptor layer leads to better VA. UHR-OCT may present a viable alternative to the assessment of central visual function, due to the easy, objective, and noninvasive data acquisition. Therefore, UHR-OCT could be of future use in judging patients' prognoses in Stargardt's disease.