Ocular Function Research Articles

Ocular Changes and Tear Cytokines in Individuals with Low Serum Vitamin D Levels: A Cross-Sectional, Controlled Study

ABSTRACT Background We investigated the effects of vitamin D on the ocular surface, tear functions, corneal imaging, and tear film cytokine levels. Methods Fifty-two patients with vitamin D levels were examined in 3 groups according to serum vitamin D levels; 28 in group 1 (<12 ng/ml), 10 in group 2 (12–20 ng/ml), and 14 in group 3 (>20 ng/ml). Ocular surface disease index (OSDI), tear break up time (BUT), lissamine green (LG) staining, Schirmer test, in vivo confocal microscopy (IVCM), and tear collection for cytokine analysis were performed. Results The mean OSDI score was 35.2 ± 23.3, 36.2 ± 17.7, 24.4 ± 18.2 (p = .253), TBUT was 6.7 ± 2.5 sec, 9.3 ± 1.8 sec, 11.1 ± 2.8 sec (p < .001), Schirmer test was 16.7 ± 8.5 mm, 18.7 ± 7.6 mm, and 20.2 ± 7 mm (p = .254), median LG staining grade was 1 (0–3), 1 (0–2), 0 (0–1) (p = .008) in group 1, group 2, and group 3, respectively. Basal epithelial cell density was 4 027 ± 512 cells/mm2, 4 673 ± 451 cells/mm2, 5 067 ± 817 cells/mm2 (p = < 0.001), sub-basal nerve density was 978 ± 204 μm/frame, 1 236 ± 172 μm/frame, 1 425 ± 290 μm/frame (p = <0.001), median number of long nerve fibers was 3 (2–4) nerve/frame, 4 (3–4) nerve/frame, 4 (3–6) nerve/frame (p = .001), and median grade of nerve fiber tortuosity was 2 (0–3), 2.5 (2–3), 3 (2–4) (p < .001) in group 1, group 2, and group 3, respectively. Mean IL-1 β (82.62 ± 15.26, 85.57 ± 17.41, and 66.44 ± 11 ng/ml in group 1, 2 and 3, respectively, p = .002), IL-17 (77.80 ± 24.91, 64.46 ± 25.47, 55.42 ± 12.05 ng/ml in group 1, 2 and 3, respectively, p = .012), and IL-2 (75.7 ± 18.4, 66.13 ± 26.78, and 59.65 ± 16.04 ng/ml in group 1, 2 and 3, respectively, p = .048) levels were significantly lower in group 3, whereas, IL-13 levels were significantly higher in group 3 (16.12 ± 5.24, 19.20 ± 4.90, and 21.6 ± 5.55 ng/ml in groups 1, 2, and 3, respectively, p = .010). Conclusions Vitamin D deficiency/insufficiency is associated with ocular surface changes shown with significant TBUT, LG staining, and tear film cytokine contents. Besides, significant corneal basal epithelial, sub-basal nerve density, and structural sub-basal nerve changes were associated with lower Vitamin D levels.

Caveolin-1 in vascular health and glaucoma: A critical vascular regulator and potential therapeutic target.

Caveolin-1 (Cav-1) is an integral scaffolding membrane protein found in most cell types. Cav-1 has been found to contribute significantly to ocular function, with mutations of Cav-1 being associated with a genetic risk of glaucoma development. Raised intraocular pressure (IOP) is a major modifiable risk factor for glaucoma. Cav-1 may be involved in both IOP-dependent and independent mechanisms involving vascular dysregulation. Systemic vascular diseases including hypertension, diabetes and hyperlipidaemia, have been shown to be associated with glaucoma development. Cav-1 is closely interlinked with endothelial nitric oxide synthase pathways that mediate vascular function and prevent cardiovascular diseases. Endothelial nitric oxide synthase and endothelin-1 are key vasoactive molecules expressed in retinal blood vessels that function to autoregulate ocular blood flow (OBF). Disruptions in the homeostasis of OBF have led to a growing concept of impaired neurovascular coupling in glaucoma. The imbalance between perfusion and neuronal stimulation arising from Cav-1 depletion may result in relative ischemia of the optic nerve head and glaucomatous injury. OBF is also governed by circadian variation in IOP and systemic blood pressure (BP). Cav-1 has been shown to influence central BP variability and other circadian rhythms such as the diurnal phagolysosomal digestion of photoreceptor fragments and toxic substrates to maintain ocular health. Overall, the vast implications of Cav-1 on various ocular mechanisms leading to glaucoma suggest a potential for new therapeutics to enhance Cav-1 expression, which has seen success in other neurodegenerative diseases.

Methods to measure blood flow and vascular reactivity in the retina.

Disturbances of retinal perfusion are involved in the onset and maintenance of several ocular diseases, including diabetic retinopathy, glaucoma, and retinal vascular occlusion. Hence, knowledge on ocular vascular anatomy and function is highly relevant for basic research studies and for clinical judgment and treatment. The retinal vasculature is composed of the superficial, intermediate, and deep vascular layer. Detection of changes in blood flow and vascular diameter especially in smaller vessels is essential to understand and to analyze vascular diseases. Several methods to evaluate blood flow regulation in the retina have been described so far, but no gold standard has been established. For highly reliable assessment of retinal blood flow, exact determination of vessel diameter is necessary. Several measurement methods have already been reported in humans. But for further analysis of retinal vascular diseases, studies in laboratory animals, including genetically modified mice, are important. As for mice, the small vessel size is challenging requiring devices with high optic resolution. In this review, we recapitulate different methods for retinal blood flow and vessel diameter measurement. Moreover, studies in humans and in experimental animals are described.

Effects of lipid-containing eye drops on the ocular surface and in vivo confocal microscopy findings in patients using systemic isotretinoin

Objective To evaluate the effects of lipid-containing Rohto Dry Aid eye drops and sodium hyaluronate eye drops on the ocular surface and in vivo confocal microscopy (IVCM) findings in patients using systemic isotretinoin. Methods This retrospective study included 71 patients using systemic isotretinoin for acne vulgaris. Ocular surface and tear functions were evaluated with the tear break-up time (TBUT), corneal fluorescein staining (CFS), and the ocular surface disease index questionnaire (OSDI). Meibography was used for the staging of Meibomian gland dysfunction (MGD) while IVCM was used for the analysis of corneal micro-structural changes. The data of 36 patients using Rohto Dry Aid (the Rohto group) and 35 patients using sodium hyaluronate (the SH group) were recorded. Pre-treatment, first month and third month data were analyzed. Results Longer TBUT, lower OSDI score, and less CFS were observed in the first and third months after treatment in the Rohto group (p < 0.001). There was no significant change in TBUT and CFS in the first month (p > 0.05) in the SH group (p < 0.05) but lower TBUT and more CFS were observed in the third month. There was no significant change in the OSDI score in the SH group. There was a significant decrease in dendritic cells, activated keratocytes, and nerve tortuosity with IVCM in both groups. However, no significant difference was found between the two groups. Conclusion Rohto Dry Aid, with its support of the lipid layer, is an effective and safe treatment agent that can improve both ocular surface and IVCM findings in evaporative dry eye cases with MGD.

Changes in Accommodation and Vergence Measurements After Smartphone Use in Healthy Young Adults

Background The primary objective of this study was to explore the impacts of extended smartphone usage on accommodation and vergence measurements among healthy young adults. Specifically it seeks to identify any changes that may occur in these ocular functions as a result of extended use of smartphones.Objectives To determine pre and post accommodation and vergence components.Methods A cross-sectional research project was conducted at Mangala College of Allied Health Sciences in Mangalore. The study involved 32 young and healthy individuals with normal vision emmetropia aged between 18 to 25 years. After initial visual screening the participants were evaluated for their accommodation and vergence abilities. Specifically they were asked to read N8 text on a smartphone device placed at a working distance of 40 cm for a duration of 30 minutes. Measurements were taken before and after this task and tabulated for analysis.Results In this study a total of 32 participants were included comprising of 12 37 males and 20 63 females with an average age of 19.00plusmn1.21 years. The results obtained from the assessment of accommodation and vergence measurements before and after 30 minutes of reading on a smartphone device indicate statistically significant changes.Conclusion The findings of this research indicate that prolonged reading on a smartphone device for 30 minutes can have a significant impact on the accommodation vergence and unit of vision for the individual.

Comparison of Two Types of Comprehensive Eye Surface Analyzers for Evaluation of Ocular Surface Function and Comfort

Comparison of Two Types of Comprehensive Eye Surface Analyzers for Evaluation of Ocular Surface Function and Comfort

Intraocular pressure changes during Valsalva maneuver

Background: Valsalva maneuver (VM) is the performance of forced expiration against a closed glottis. Activities such as straining during defecation, blowing a balloon, lifting heavy weights, or playing the wind instruments like saxophone entail the performance of the VM. Even though many parameters such as blood pressure and pulse rate are changed to certain extent during VM. Aims and Objectives: This study aims to know whether any intraocular pressure (IOP) changes take place by performing VM. IOP is the fluid pressure of the eye. Increased IOP leads to ischemia of retinal nerve fiber. Decreased IOP can lead to impairment of the ocular functions. Elevation of IOP is the major risk factor to develop glaucoma primary open-angle glaucoma (POAG). Materials and Methods: 52 intern students (28 males and 24 females) among 20 myopics and 32 emmetropes are selected for this study from GITAM Institute of Medical Sciences and Research. Complete systemic and ocular examination is conducted. IOP is recorded with the correction of central corneal thickness. All of them are trained for “Valsalva Maneuver” for 10 days during their stay in unit posting. VM is practiced for 2 min. The IOPs recorded before and after the VM procedure. Results: There is a rise in the IOP after VM in all the 52 internee students. The average raise in the IOP after VM for 2 min is about 2.81 mmHg. IOP raised more in females than males. There is an increase of IOP in emmetropes than myopes. Conclusion: VM raises the IOP in all the individuals. The POAG individuals should be cautioned during the weight lifting, conditions which may lead to increase the intra-abdominal pressure. These conditions cause the natural VM. All these maneuvers can cause fluctuations in the IOP, which are dangerous and may lead to the progression of POAG. VM can be used as screening procedure for glaucoma.

Identification of ocular regulatory functions of core histone variant H3.2

The posttranscriptional modifications (PTM) of the Histone H3 family play an important role in ocular system differentiation. However, there has been no study on the nature of specific Histone H3 subtype carrying these modifications. Fortuitously, we had previously identified a dominant small-eye mutant Aey69 mouse with a mutation in the H3.2 encoding Hist2h3c1 gene (Vetrivel et al., 2019). In continuation, in the present study, the role of Histone H3.2 with relation to the microphtalmic Aey69 has been elaborated. Foremost, a transgenic mouse line expressing the fusion protein H3.2-GFP was generated using Crispr/Cas9. The approach was intended to confer a unique tag to the Hist2h3c1 gene which is similar in sequence and encoded protein structure to other histones. The GFP tag was then used for ChIP Seq analysis of the genes regulated by H3.2. The approach revealed ocular specific H3.2 targets including Ephrin family genes. Altered enrichment of H3.2 was found in the mutant Aey69 mouse, specifically around the ligand Efna5 and the receptor Ephb2. The effect of this altered enrichment on Ephrin signaling was further analysed by QPCR and immunohistochemistry. This study identifies Hist2h3c1 encoded H3.2 as an important epigenetic player in ocular development. By binding to specific regions of ocular developmental factors Histone H3.2 facilitates the function of these genes for successful early ocular development.

Is there Cholinesterase Activity in the Eye?

The nervous system regulates the visual system through neurotransmitters that play an important role in visual and ocular functions. One of those neurotransmitters is acetylcholine, a key molecule that plays a variety of biological functions. Moreover, acetylcholinesterase, the enzyme responsible for the hydrolysis of acetylcholine, is implicated in cholinergic function. However, several studies have demonstrated that in addition to their enzymatic functions, acetylcholinesterase exerts non-catalytic functions. In recent years, the importance of evaluating all possible functions of acetylcholine-acetylcholinesterase has been shown. Nevertheless, there is evidence suggesting that cholinesterase activity in the eye can regulate some biological events both in structures of the anterior and posterior segment of the eye and, therefore, in the visual information that is processed in the visual cortex. Hence, the evaluation of cholinesterase activity could be a possible marker of alterations in cholinergic activity in both ocular and systemic diseases.

Effects of contact lens wearing on corneal sensitivity and reflex functions

AbstractPurpose: To study the effects of contact lens (CL) use on corneal sensory nerve activity, exploring corneal sensitivity and ocular functions regulated by sensory input in asymptomatic (CL‐A) and symptomatic (CL‐S) CL wearers.Methods: CL wearers (23.8 ± 1.0 years; n = 31) participating in the study were classified as CL‐S when OSDI ≥13. Sex and age eye glasses (EG) users (24.5 ± 0.8 years, n = 29) participated as control group. Corneal mechanical, chemical and cold sensitivity was explored using a gas esthesiometer and 4°C‐saline drops; intensity, irritation and cold components of the evoked sensation were measured with Visual Analogue Scales (VASs). Tear volume (with phenol red threads), tear stability (TBUT), basal blinking frequency (BF), ocular surface temperature (OST; by IR thermography) were also assessed.Results: CL wearers scored higher irritation VAS values than EG wearers for mechanical (2.5 ± 0.5 vs. 1.4 ± 0.4 for 160 ml/min air flow, CL vs EG, p = 0.09) and chemical stimuli (1.8 ± 0.5 vs. 0.7 ± 0.3 for 40% CO2, p &lt; 0.05), and lower intensity values for cold stimulation (2.2 ± 0.4 vs. 4.5 ± 0.7, p &lt; 0.05); tear volume was similar (27.0 ± 2.2 vs. 27.2 ± 1.6 mm), TBUT lower (8.3 ± 0.5 vs. 11.7 ± 0.5 s, p &lt; 0.001), BF was higher (25.1 ± 2.4 vs. 14.3 ± 1.9 blinks/min, p &lt; 0.001), and OST was lower (34.4 ± 0.2 vs. 35.2 ± 0.2°C, p &lt; 0.01). VAS values for cold stimulation was slightly lower in CL‐S than in CL‐A (2.0 ± 0.4 vs. 4.0 ± 0.8, p = 0.06), while OST was higher (35.0 ± 0.2 vs. 33.9 ± 0.3°C, p &lt; 0.01).Conclusions: CL wearing affects corneal sensory nerve functions, changing corneal sensitivity, blinking rate, tearing stability, and OST. The changes found in corneal sensitivity fully agree with those described in neural activity of corneal sensory nerves after injury or inflammation using animal models: sensitization of corneal nociceptors and inhibition of cold thermoreceptors. The differences between CL‐S and CL‐A wearers could be due to the presence of subclinical ocular surface inflammation in symptomatic subjects.

Caveolar and non-Caveolar Caveolin-1 in ocular homeostasis and disease.

Caveolae, specialized plasma membrane invaginations present in most cell types, play important roles in multiple cellular processes including cell signaling, lipid uptake and metabolism, endocytosis and mechanotransduction. They are found in almost all cell types but most abundant in endothelial cells, adipocytes and fibroblasts. Caveolin-1 (Cav1), the signature structural protein of caveolae was the first protein associated with caveolae, and in association with Cavin1/PTRF is required for caveolae formation. Genetic ablation of either Cav1 or Cavin1/PTRF downregulates expression of the other resulting in loss of caveolae. Studies using Cav1-deficient mouse models have implicated caveolae with human diseases such as cardiomyopathies, lipodystrophies, diabetes and muscular dystrophies. While caveolins and caveolae are extensively studied in extra-ocular settings, their contributions to ocular function and disease pathogenesis are just beginning to be appreciated. Several putative caveolin/caveolae functions are relevant to the eye and Cav1 is highly expressed in retinal vascular and choroidal endothelium, Müller glia, the retinal pigment epithelium (RPE), and the Schlemm's canal endothelium and trabecular meshwork cells. Variants at the CAV1/2 gene locus are associated with risk of primary open angle glaucoma and the high risk HTRA1 variant for age-related macular degeneration is thought to exert its effect through regulation of Cav1 expression. Caveolins also play important roles in modulating retinal neuroinflammation and blood retinal barrier permeability. In this article, we describe the current state of caveolin/caveolae research in the context of ocular function and pathophysiology. Finally, we discuss new evidence showing that retinal Cav1 exists and functions outside caveolae.

Feasibility Study of Dendrimer-Based TTR-CRISPR pDNA Polyplex for Ocular Amyloidosis in Vitro.

Hereditary amyloidgenic transthyretin (ATTR) amyloidosis is caused by a genetic point-mutated transthyretin such as TTR Val30Met (TTR V30M), since it forms protein aggregates called amyloid resulting in the tissue accumulation and functional disorders. In particular, ATTR produced by retinal pigment epithelial cells often causes ATTR ocular amyloidosis, which elicits deterioration of ocular function and ultimately blindness. Therefore, development of novel therapeutic agents is urgently needed. Genome-editing technology using Clustered Regularly Interspaced Short Palindromic Repeats-CRISPR associated proteins (CRISPR-Cas9) system is expected to be a therapeutic approach to treat genetic diseases, such as ATTR amyloidosis caused by a point mutation in TTR gene. Previously, we reported that glucuronylglucosyl-β-cyclodextrin conjugated with a polyamidoamine dendrimer (CDE) had excellent gene transfer ability and that underlying dendrimer inhibited TTR aggregation. Conversely, folate receptors are known to be highly expressed in retina; thus, folate has potential as a retinal target ligand. In this study, we prepared a novel folate-modified CDE (FP-CDE) and investigated its potential as a carrier for the retinal delivery of TTR-CRISPR plasmid DNA (pDNA). The results suggested that FP-CDE/TTR-CRISPR pDNA could be taken up by retinal pigment epithelial cells via folate receptors, exhibited TTR V30M amyloid inhibitory effect, and suppressed TTR production via the genome editing effect (knockout of TTR gene). Thus, FP-CDE may be useful as a novel therapeutic TTR-CRISPR pDNA carrier in the treatment of ATTR ocular amyloidosis.

Scale for Ocular motor Disorders in Ataxia (SODA)

Eye movements are fundamental diagnostic and progression markers of various neurological diseases, including those affecting the cerebellum. Despite the high prevalence of abnormal eye movements in patients with cerebellar disorders, the traditional rating scales do not focus on abnormal eye movements. We formed a consortium of neurologists focusing on cerebellar disorders. The consortium aimed to design and validate a novel Scale for Ocular motor Disorders in Ataxia (SODA). The primary purpose of the scale is to determine the extent of ocular motor deficits due to various phenomenologies. A higher score on the scale would suggest a broader range of eye movement deficits. The scale was designed such that it is easy to implement by non-specialized neurological care providers. The scale was not designed to measure each ocular motor dysfunction's severity objectively. Our validation studies revealed that the scale reliably measured the extent of saccade abnormalities and nystagmus. We found a lack of correlation between the total SODA score and the total International Cooperative Ataxia Rating Scale (ICARS), Scale for Assessment and Rating of Ataxia (SARA), or Brief Ataxia Rating Scale (BARS). One explanation is that conventionally reported scales are not dedicated to eye movement disorders; and when present, the measure of ocular motor function is only one subsection of the ataxia rating scales. It is also possible that the severity of ataxias does not correlate with eye movement abnormalities. Nevertheless, the SODA met the consortium's primary goal: to prepare a simple outcome measure that can identify ocular motor dysfunction in patients with cerebellar ataxia.

Screening of oral tamoxifen ocular toxicity in patients with breast cancer

Background Carcinoma of the breast is considered as one of the main cancer types among women. Its prevalence is reported to be the second most common type. Several treatment lines have been used in breast cancer besides surgical and radiological interventions. Tamoxifen is one of the medical treatments used in postsurgical prophylaxis of breast cancer. Various visual problems were reported with tamoxifen therapy. These include posterior subcapsular cataracts, color vision affection, intraretinal crystals, and optic neuritis. Aim The aim of this work was to screen for ocular toxicity of tamoxifen used for breast cancer treatment in patients having no ophthalmic complaints and treated with tamoxifen for at least 2 years with a dose of 20 mg per day. Patients and methods We included 50 women with breast carcinoma on tamoxifen therapy for at least 2 years, and then we divided them into two groups regarding duration of tamoxifen intake from 2 to 4 years (group 1) and from 5 to 8 years (group 2). All participants underwent complete careful history taking and full ophthalmological examination. Best-corrected visual acuity was measured using Snellen chart with conversion to logMAR notation for statistical analysis. We assessed the retinal structural changes by optical coherence tomography (OCT) and correlated these changes with the function affection (color vision testing and electrophysiological studies). Results There was a statistically significant correlation between duration of tamoxifen intake and Retinal Pigment Epithelium (RPE) mottling. No other significant correlations were detected. There was no significant difference between the two groups in mean best-corrected visual acuity; intraocular pressure; cup values; disc parameters; ganglion cell complex thickness; retinal nerve fiber layer zones, except for in the inferior quadrant; and macular thickness, except for in the superior quadrant. OCT layer thinning shows retinal nerve fiber layer affection in 34% of cases, ganglion cell complex affection in 48% of cases, and macula affection in 64% of cases. Color vision defects were found in 12%, and electrophysiological test changes were found in a few cases. Conclusion Tamoxifen therapy causes minimal affection on the ocular structure and function. OCT layer thinning (34–64% of cases) precedes the clinical changes. This highlights the importance of OCT examination in those patients to evaluate tamoxifen toxicity, and further studies will be needed to evaluate the reversibility of these changes after stoppage of therapy. The main ocular complications associated with tamoxifen therapy were correlated with duration of treatment.

From your kidneys to your eyes: lessons from computational kidney models

Purpose: The purpose of this review is to describe computational models that have been developed for studying kidney function and howthese models may be adapted to study the eyes. Methods: We derive equations for modeling solute andwater transport across epithelial cell membranes in the kidney. These equations describe mass conservation, as well membrane transport via cotransporters, exchangers, and primary active transport. Results: Wedescribe howcomputational models of renal transport have been applied to investigate kidney function in physiological and pathophysiological conditions. Conclusion: The computational models herein described for the kidney may be adapted to study ocular functions and dysfunction.

Single-Cell RNA Sequencing Reveals Molecular Features of Heterogeneity in the Murine Retinal Pigment Epithelium.

Transcriptomic analysis of the mammalian retinal pigment epithelium (RPE) aims to identify cellular networks that influence ocular development, maintenance, function, and disease. However, available evidence points to RPE cell heterogeneity within native tissue, which adds complexity to global transcriptomic analysis. Here, to assess cell heterogeneity, we performed single-cell RNA sequencing of RPE cells from two young adult male C57BL/6J mice. Following quality control to ensure robust transcript identification limited to cell singlets, we detected 13,858 transcripts among 2667 and 2846 RPE cells. Dimensional reduction by principal component analysis and uniform manifold approximation and projection revealed six distinct cell populations. All clusters expressed transcripts typical of RPE cells; the smallest (C1, containing 1–2% of total cells) exhibited the hallmarks of stem and/or progenitor (SP) cells. Placing C1–6 along a pseudotime axis suggested a relative decrease in melanogenesis and SP gene expression and a corresponding increase in visual cycle gene expression upon RPE maturation. K-means clustering of all detected transcripts identified additional expression patterns that may advance the understanding of RPE SP cell maintenance and the evolution of cellular metabolic networks during development. This work provides new insights into the transcriptome of the mouse RPE and a baseline for identifying experimentally induced transcriptional changes in future studies of this tissue.

Vestibular and balance function in veterans with chronic dizziness associated with mild traumatic brain injury and blast exposure.

The purpose of this study was to examine vestibular and balance function in individuals with chronic dizziness associated with mTBI/blast. A prospective case-control study design was used to examine ocular motor, vestibular function, and postural stability in veterans with symptoms of dizziness and/or imbalance following an mTBI or blast exposure (n = 77) and a healthy control group (n = 32). Significant group differences were observed for saccadic accuracy, VOR gain during slow harmonic acceleration at 0.01 Hz, cervical vestibular evoked myogenic potentials asymmetry ratio, composite equilibrium score on the sensory organization test, total Dynamic Gait Index score, and gait. The frequency of test abnormalities in participants with mTBI/blast ranged from 0 to 70% across vestibular, ocular motor, and balance/gait testing, with the most frequent abnormalities occurring on tests of balance and gait function. Seventy-two percent of the mTBI/blast participants had abnormal findings on one or more of the balance and gait tests. Vestibular test abnormalities occurred in ~34% of the individuals with chronic dizziness and mTBI/blast, and abnormalities occurred more frequently for measures of otolith organ function (25% for cVEMP and 18% for oVEMP) than for measures of hSCC function (8% for SHA and 6% for caloric test). Abnormal ocular motor function occurred in 18% of the mTBI/blast group. These findings support the need for comprehensive vestibular and balance assessment in individuals with dizziness following mTBI/blast-related injury.

High-Frequency Ultrasound Elastography to Assess the Nonlinear Elastic Properties of the Cornea and Ciliary Body.

Mechanical properties of the anterior anatomical structures of the eye, such as the cornea and ciliary body, play a key role in the ocular function and homeostasis. However, measuring the biomechanical properties of the anterior ocular structures, especially deeper structures, such as the ciliary body, remains a challenge due to the lack of high-resolution imaging tools. Herein, we implement a mechanical shaker-based high-frequency ultrasound elastography technique that can track the induced elastic wave propagation to assess the linear and nonlinear elastic properties of anterior ocular structures. The findings of this study advance our understanding of the role of anterior ocular structures in the pathogenesis of different ocular disorders, such as glaucoma.

Human ocular surface microcirculation quantified by in vivo computer assisted video microscopy and diffuse reflectance spectroscopy

Non-invasive imaging techniques are increasingly used to objectively quantify anterior segment structures of the eye. In this study, we apply the novel oxygen delivery index (ODIN) concept that, quantifies microvascular capacity for oxygen delivery, to the ocular surface in healthy humans.The purpose of the study was to test the applicability of the technologies used for data acquisition from the human ocular surface. We also validated whether the ODIN concept has sufficient sensitivity to detect and differentiate between microvascular structure and function in limbal and bulbar conjunctiva.Multiple ocular surface measurements using computer-assisted video microscopy (field of view: 1.6 mm × 0.9 mm) and diffuse reflectance spectroscopy (measuring volume: ∼0.1 mm3) were obtained from limbal and bulbar conjunctiva in 20 healthy volunteers. Three parameters were extracted during analyses: Functional capillary density, capillary flow velocity, and microvascular oxygen saturation.Functional capillary density was higher at limbus than in bulbar conjunctiva (11.2 ± 1.8 c/mm versus 5.2 ± 1.2 c/mm, p < 0.01), and microvascular oxygen saturation was lower at limbus (77 ± 8%) as compared to bulbar conjunctiva (89 ± 6%), p < 0.01. More than 80% of scored capillaries had continuous blood flow and no difference was seen between the recording sites (p = 0.68).In conclusion, the ODIN concept is applicable for the assessment of human ocular surface microvascular function and has sufficient sensitivity to detect increased capillary density and oxygen extraction at limbus as compared with bulbar conjunctiva.

Management of Posttraumatic Enophthalmos Including Complex Secondary Deficits.

Posttraumatic enophthalmos (PE) arises when the ocular globe is displaced posteriorly and inferiorly in the orbital cavity due to a mismatch in orbital volume and orbital content. This most commonly happens after orbital fractures. The resulting disruptions to aesthetic form and ocular functions often necessitate surgical correction for reconstruction and restoration. The purpose of surgical management of PE is to reconstruct orbital shape and volume as well as to restore any herniated orbital content. This can be particularly challenging in cases involving large defects that require complex orbital reconstruction. Recent advancements in computer-aided surgery have introduced innovative and important tools to assist surgeons with these difficult cases. The ability to create customized, patient-specific implants can facilitate reconstruction involving complicated anatomy. Additionally, intraoperative imaging and intraoperative navigation can serve as useful guides for surgeons to more accurately place implants, especially in cases with limited visualization, in order to achieve optimal outcomes.