Tunable degrees of neurodegeneration in rats based on microsphere-induced models of chronic glaucoma.

This study compares four different animal models of chronic glaucoma against normal aging over 6 months. Chronic glaucoma was induced in 138 Long-Evans rats and compared against 43 aged-matched healthy rats. Twenty-five rats received episcleral vein sclerosis injections (EPIm cohort) while the rest were injected in the eye anterior chamber with a suspension of biodegradable microspheres: 25 rats received non-loaded microspheres (N-L Ms cohort), 45 rats received microspheres loaded with dexamethasone (MsDexa cohort), and 43 rats received microspheres co-loaded with dexamethasone and fibronectin (MsDexaFibro cohort). Intraocular pressure, neuroretinal function, structure and vitreous interface were evaluated. Each model caused different trends in intraocular pressure, produced specific retinal damage and vitreous signals. The steepest and strongest increase in intraocular pressure was seen in the EPIm cohort and microspheres models were more progressive. The EPIm cohort presented the highest vitreous intensity and percentage loss in the ganglion cell layer, the MsDexa cohort presented the greatest loss in the retinal nerve fiber layer, and the MsDexaFibro cohort presented the greatest loss in total retinal thickness. Function decreased differently among cohorts. Using biodegradable microspheres models it is possible to generate tuned neurodegeneration. These results support the multifactorial nature of glaucoma based on several noxa.

Chronic Glaucoma Using Biodegradable Microspheres to Induce Intraocular Pressure Elevation. Six-Month Follow-Up.

BACKGROUND: To compare two prolonged animal models of glaucoma over 24 weeks of follow-up. A novel pre-trabecular model of chronic glaucoma was achieved by injection of biodegradable poly lactic-co-glycolic acid (PLGA) microspheres (10-20 µm) (Ms20/10) into the ocular anterior chamber to progressively increase ocular hypertension (OHT). METHODS: Rat right eyes were injected to induce OHT: 50% received a suspension of Ms20/10 in the anterior chamber at 0, 2, 4, 8, 12, 16 and 20 weeks, and the other 50% received a sclerosing episcleral vein injection biweekly (EPIm). Ophthalmological clinical signs, intraocular pressure (IOP), neuroretinal functionality measured by electroretinography (ERG), and structural analysis of the retina, retinal nerve fiber layer (RNFL) and ganglion cell layer (GCL) protocols using optical coherence tomography (OCT) and histological exams were performed. RESULTS: Both models showed progressive neuroretinal degeneration (p < 0.05), and contralateral eye affectation. The Ms20/10 model showed a more progressive increase in IOP and better preservation of ocular surface. Although no statistical differences were found between models, the EPIm showed a tendency to produce thicker retinal and thinner GCL thicknesses, slower latency and smaller amplitude as measured using ERG, and more aggressive disturbances in retinal histology. In both models, while the GCL showed the greatest percentage loss of thickness, the RNFL showed the greatest and earliest rate of thickness loss. CONCLUSIONS: The intracameral model with biodegradable microspheres resulted more like the conditions observed in humans. It was obtained by a less-aggressive mechanism, which allows for adequate study of the pathology over longer periods.

Angiography with optical coherence tomography as a biomarker in multiple sclerosis.

PURPOSE: To investigate superficial retinal microvascular plexuses detected by optical coherence tomography angiography (OCT-A) in multiple sclerosis (MS) subjects and compare them with healthy controls. METHODS: A total of 92 eyes from 92 patients with relapsing-remitting MS and 149 control eyes were included in this prospective observational study. OCT-A imaging was performed using Triton Swept-Source OCT (Topcon Corporation, Japan). The vessel density (VD) percentage in the superficial retinal plexus and optic disc area (6 x 6 mm grid) was measured and compared between groups. RESULTS: MS patients showed a significant decrease VD in the superior (p = 0.005), nasal (p = 0.029) and inferior (p = 0.040) parafoveal retina compared with healthy subjects. Patients with disease durations of more than 5 years presented lower VD in the superior (p = 0.002), nasal (p = 0.017) and inferior (p = 0.022) parafoveal areas compared with healthy subjects. Patients with past optic neuritis episodes did not show retinal microvasculature alterations, but patients with an EDSS score of less than 3 showed a significant decrease in nasal (p = 0.024) and superior (p = 0.006) perifoveal VD when compared with healthy subjects. CONCLUSIONS: MS produces a decrease in retinal vascularization density in the superficial plexus of the parafoveal retina. Alterations in retinal vascularization observed in MS patients are independent of the presence of optic nerve inflammation. OCT-A has the ability to detect subclinical vascular changes and is a potential biomarker for diagnosing the presence and progression of MS.

Effect of age and sex on neurodevelopment and neurodegeneration in the healthy eye: Longitudinal functional and structural study in the Long-Evans rat.

The processes involved in neurodevelopment and aging have not yet been fully discovered. This is especially challenging in premorbid or borderline situations of neurodegenerative diseases such as Alzheimer's or glaucoma. The retina, as part of the central nervous system, can be considered the easiest and most accessible neural structure that can be analyzed using non-invasive methods. Animal studies of neuroretinal tissue in situations of health and under controlled conditions allow the earliest sex- and aging-induced changes to be analyzed so as to differentiate them from the first signs occurring in manifested disease. This study evaluates differences by age and sex based on intraocular pressure (IOP) and neuroretinal function and structure in healthy young and adult rats before decline due to senescence. For this purpose, eighty-five healthy Long-Evans rats (31 males and 54 females) were analyzed in this 6-month longitudinal study running from childhood to adulthood. IOP was measured by tonometer (Tonolab; Tiolat Oy Helsinki, Finland), neuroretinal function was recorded by flash scotopic and light-adapted photopic negative response electroretinography (ERG) (Roland consult® RETIanimal ERG, Germany) at 4, 16 and 28 weeks of age; and structure was evaluated by in vivo optical coherence tomography (OCT) (Spectralis, Heidelberg® Engineering, Germany). Analyzing both sexes together, IOP was below 20 mmHg throughout the study; retina (R), retinal nerve fiber layer (RNFL) and ganglion cell layer (GCL) thicknesses measured by OCT decreased over time; an increase in ERG signal was recorded at week 16; and no differences were found between right and left eyes. However, analyzing differences by sex revealed that males had higher IOP (even reaching ocular hypertension [>20 mmHg] by the end of the study [7 months of age]), exhibited greater neuroretinal thickness but higher structural percentage loss, and had worse dark- and light-adapted function as measured by ERG than females. This study concludes that age and sex influenced neurodevelopment and neurodegeneration. Different structural and functional degenerative patterns were observed by sex; these occurred earlier and more intensely in males than in age-matched females.

Dexamethasone delivery to the ocular posterior segment by sustained-release Laponite formulation.

This paper presents a novel nanoformulation for sustained-release delivery of dexamethasone (DEX) to the ocular posterior segment using a Laponite (LAP) carrier-DEX/LAP 1:10 w w-1 formulation; 10 mg ml-1. In vivo ocular feasibility and pharmacokinetics after intravitreal (IV) and suprachoroidal (SC) administration in rabbit eyes are compared against IV administration of a DEX solution (1 mg ml-1). Thirty rabbit eyes were injected with the DEX/LAP formulation (15 suprachoroid/15 intravitreous). Ophthalmological signs were monitored at day 1 and at weeks 1-4-12-24 post-administration. Three eyes per sample time point were used to quantify DEX concentration using high-performance liquid chromatography-mass spectrometry. The ocular tissues' pharmacokinetic parameters (lens, vitreous humour, choroid-retina unit and sclera) were studied. DEX/LAP was well tolerated under both administration methods. Peak intraocular DEX levels from the DEX/LAP were detected in the vitreous humour after both deliveries soon after administration. The vitreous area under the curve was significantly greater after both DEX/LAP deliveries (IV: 205 968.47; SC: 11 442.22 ng g-1 d-1) than after IV administration of the DEX solution (317.17 ng g-1 d-1). Intravitreal DEX/LAP delivery extended higher vitreous DEX levels up to week 24 (466.32 ± 311.15 ng g-1). With SC delivery, DEX levels were detectable in the choroid-retina unit (12.04 ± 20.85 ng g-1) and sclera (25.46 ± 44.09 ng g-1) up to week 24. This study demonstrated the intraocular feasibility of both SC and IV administration of the DEX/LAP formulation. The LAP increased the intraocular retention time of DEX when compared with conventional solutions. DEX/LAP could be considered a biocompatible and useful sustained-release formulation for treating posterior-pole eye diseases.

Computer-Aided Diagnosis of Multiple Sclerosis Using a Support Vector Machine and Optical Coherence Tomography Features.

The purpose of this paper is to evaluate the feasibility of diagnosing multiple sclerosis (MS) using optical coherence tomography (OCT) data and a support vector machine (SVM) as an automatic classifier. Forty-eight MS patients without symptoms of optic neuritis and forty-eight healthy control subjects were selected. Swept-source optical coherence tomography (SS-OCT) was performed using a DRI (deep-range imaging) Triton OCT device (Topcon Corp., Tokyo, Japan). Mean values (right and left eye) for macular thickness (retinal and choroidal layers) and peripapillary area (retinal nerve fibre layer, retinal, ganglion cell layer-GCL, and choroidal layers) were compared between both groups. Based on the analysis of the area under the receiver operator characteristic curve (AUC), the 3 variables with the greatest discriminant capacity were selected to form the feature vector. A SVM was used as an automatic classifier, obtaining the confusion matrix using leave-one-out cross-validation. Classification performance was assessed with Matthew's correlation coefficient (MCC) and the AUCCLASSIFIER. The most discriminant variables were found to be the total GCL++ thickness (between inner limiting membrane to inner nuclear layer boundaries), evaluated in the peripapillary area and macular retina thickness in the nasal quadrant of the outer and inner rings. Using the SVM classifier, we obtained the following values: MCC = 0.81, sensitivity = 0.89, specificity = 0.92, accuracy = 0.91, and AUCCLASSIFIER = 0.97. Our findings suggest that it is possible to classify control subjects and MS patients without previous optic neuritis by applying machine-learning techniques to study the structural neurodegeneration in the retina.

Reproducibility and reliability of retinal and optic disc measurements obtained with swept-source optical coherence tomography in a healthy population.

PURPOSE: To analyze the reproducibility of macular and peripapillary thickness measurements, and optic nerve morphometric data obtained with Triton Optical coherence tomography (OCT) in a healthy population. STUDY DESIGN: Observational cross sectional study. MATERIAL AND METHODS: A total of 108 eyes underwent evaluation using the Triton Swept Source-OCT. A wide protocol was used and measurements in each eye were repeated three times. Morphometric data of the optic nerve head, full macular thickness, ganglion cell layer (GCL) and retinal nerve fiber layer thickness (RNFL) were analyzed. For each parameter, the coefficient of variation (COV) and the intra-class (ICC) correlation values were calculated. RESULTS: Measurements were highly reproducible for all morphometric measurements of the optic disc, with a mean COV of 6.36%. Macular full thickness showed good COV and ICC coefficients, with a mean COV value of 1.00%. Macular GCL thickness showed a mean COV value of 3.06%, and ICC higher than 0.787. Peripapillary RNFL thickness showed good COV and ICC coefficients, with a mean COV value of 8.31% and ICC higher than 0.684. The inferotemporal sector showed the lowest ICC (0.685). CONCLUSIONS: Triton OCT presents good reproducibility values in measurements corresponding to retinal parameters, with macular measurements showing the highest reproducibility rates. Peripapillary RNFL measurements should be evaluated with caution.

Ability of Swept-Source Optical Coherence Tomography to Detect Retinal and Choroidal Changes in Patients with Multiple Sclerosis.

PURPOSE: To evaluate the ability of new swept-source (SS) optical coherence tomography (OCT) technology to detect changes in retinal and choroidal thickness in patients with multiple sclerosis (MS). METHODS: A total of 101 healthy and 97 MS eyes underwent retinal and choroidal assessment using SS Triton OCT (Topcon). Macular thickness and peripapillary data (retinal, ganglion cell layer (GCL+, GCL++) and retinal nerve fiber layer (RNFL) thickness) were analyzed, including choroidal thickness evaluation. RESULTS: Significant macular thinning was observed in all ETDRS areas (p < 0.001) in MS patients. Peripapillary retinal, RNFL, and GCL ++ thickness showed a significant reduction in patients in all sectors (p < 0.001) except in the nasal quadrant/sector (p > 0.05). GCL+ measurements were found to be reduced in the nasal (p=0.003), inferonasal (p=0.045), and temporal (p=0.001) sectors and total thickness (p < 0.001). Choroidal thickness was reduced in the outer macular ring in MS patients compared with controls (p=0.038). CONCLUSION: New swept-source technology for OCT devices detects retinal thinning in MS patients, providing increased depth analysis of the choroid in these patients. MS patients present reduced retinal and choroidal thickness in the macular area and reduced peripapillary retinal, RNFL, and GCL thickness.

Peripapillary Choroidal Thickness Analysis Using Swept-Source Optical Coherence Tomography in Glaucoma Patients: A Broader Approach.

AIMS: To evaluate and compare peripapillary choroidal thickness (PPCT) in a wide area around the optic disk and various choroidal established zones in healthy controls and primary open-angle glaucoma (POAG) patients using a new swept-source (SS) optical coherence tomography (OCT) device. METHODS: A total of 246 eyes were finally included in this observational, prospective, cross-sectional study: 111 healthy controls and 135 POAG patients. The healthy subjects were divided into 2 populations: the teaching population (25 used to establish choroidal zones) and the validating population (86 used for comparing choroidal thickness with POAG patients). A 26 × 26 cube grid centered on the optic disk was generated using an SS-OCT to automatically measure choroidal thickness. Four choroidal zones were established and used to compare PPCT between healthy controls and POAG patients. RESULTS: PPCT was significantly thinner in zones 3 and 4 of the POAG group. The choroid exhibited a similar pattern in controls and patients with POAG; it was thickest in the superior region, followed in order by the temporal, nasal, and inferior regions. CONCLUSIONS: Peripapillary choroidal tissue shows a concentric pattern in both groups, and glaucoma patients present with peripapillary choroidal thinning compared with healthy subjects, especially in areas further away from the optic disk.

The use of zonal analysis of peripapillary choroidal thickness in primary open-angle glaucoma.

PURPOSE: To evaluate automatic peripapillary choroidal thickness (PPCT) measurements in a wide area around the optic disc and various established zones in primary open-angle glaucoma (POAG) patients and age- and sex-matched healthy controls using a new swept-source optical coherence tomography (SS-OCT) device. STUDY DESIGN: Single center cross-sectional observational study. METHODS: A total of 135 POAG patients and 86 healthy subjects were consecutively enrolled. An optic disc 6.0 × 6.0 mm three-dimensional scan OD was obtained using the SS-OCT Triton. A 26 × 26 cube-grid centered in the optic disc was generated to automatically measure choroidal thickness. Seven choroidal zones were established (superior temporal, central, and nasal; inferior temporal, central, and nasal, and the optic nerve head) and compared between healthy controls and POAG patients. RESULTS: PPCT was significantly thinner in the central superior, nasal superior, and nasal inferior zones of the POAG subjects. Choroidal thickness in the central superior zone was 124.61 ± 54.95 µm in POAG group vs 156.17 ± 80.89 µm in healthy controls (p = 0.029); in the nasal superior zone, 133.84 ± 58.89 µm in the POAG group vs 168.34 ± 73.45 µm in healthy controls (p = 0.012); and in the nasal inferior zone, 113.45 ± 49.93 µm in the POAG group vs 137.47 ± 65.96 µm in healthy controls (p = 0.049). CONCLUSION: Compared with healthy subjects, glaucoma patients present with peripapillary choroidal thinning, especially in the central superior, nasal superior, and nasal inferior zones. The new SS-OCT could be a useful tool to evaluate choroidal thinning, and it could be an additional support to facilitate glaucoma diagnosis.

Normal reference ranges of optical coherence tomography parameters in childhood.

OBJECTIVE: To report normal reference values for peripapillary retinal nerve fibre layer (RNFL) thickness and optic disc parameters in children from a community population. METHODS: The authors performed a cross-sectional study examining RNFL and optic nerve head (ONH) properties in 358 children aged between 6 and 13 years with no ocular disease. All children underwent an ophthalmic examination that included visual acuity (logMAR), stereopsis assessment (TNO) and optical coherence tomography (Cirrus OCT Zeiss, 'Optic Disc Cube 200×200' protocol). One eye from each subject selected at random was finally analysed. The authors evaluated the influence of height, gender and age on measurements. RESULTS: High-quality scan data were obtained from 357 children and 344 were finally included. The mean age (SD) was 9.16 (1.7) years and the mean (SD) RNFL average thickness was 98.46 (10.79) µm. The temporal quadrant showed the thinnest RNFL (69.35±11.28 µm), followed by the nasal (71.30±13.45 µm), superior (123.65±19.49 µm) and inferior (130.18±18.13 µm) quadrants. The mean rim area (SD) and disc area (SD) were 1.59 (0.33) and 2.05 (0.39) mm(2), respectively. The average cup to disc (C:D) ratio (SD) was 0.43 (0.19). The authors found no differences in any of the parameters with regard to weight, height and gender. CONCLUSIONS: This study demonstrates normative values of RNFL thickness and ONH parameters in a sample of Caucasian children from the general population.

New findings in the ataxia of Charlevoix-Saguenay.

The aim of the study was to enhance our understanding of the pathogenesis of the ataxia of Charlevoix-Saguenay, based on the findings presented herein. Five patients with a molecular diagnosis of this disease underwent clinical, radiological, ophthalmologic and electrophysiological examinations. Five novel mutations, which included nonsense and missense variants, were identified, with these resulting in milder phenotypes. In addition to the usual manifestations, a straight dorsal spine was found in every case, and imaging techniques showed loss of the dorsal kyphosis. Cranial MRI demonstrated hypointense linear striations at the pons. Tensor diffusion MRI sequences revealed that these striations corresponded with hyperplastic pontocerebellar fibres, and tractographic sequences showed interrupted pyramidal tracts at the pons. Ocular coherence tomography demonstrated abnormal thickness of the nerve fibre layer. Electrophysiological studies showed nerve conduction abnormalities compatible with a dysmyelinating neuropathy, with signs of chronic denervation in distal muscles. The authors suggest that the hyperplastic pontocerebellar fibres compress the pyramidal tracts at the pons, and that the amount of retinal fibres traversing the optic discs is enlarged. These facts point to the contribution of an abnormal developmental mechanism in the ataxia of Charlevoix-Saguenay. Accordingly, spasticity would be mediated by compression of the pyramidal tracts, neuromuscular symptoms by secondary axonal degeneration superimposed on the peripheral myelinopathy, while the cause of the progressive ataxia remains speculative. The distinctive aspect of the dorsal spine could be of help in the clinical diagnosis.

Effects of smoking during pregnancy on the optic nerve neurodevelopment.

BACKGROUND: Tobacco smoking during pregnancy alters neurodevelopment. Optical coherence tomography (OCT) provides precise measurements of the retinal nerve fiber layer (RNFL), which forms part of the central nervous system. AIMS: To assess using the OCT how smoking during pregnancy would affect optic nerve development as detected in human offspring. STUDY DESIGN: Visual examination and OCT were performed on a group of children (n=70; 4.15-13.50 years of age), classified as being exposed or not to maternal smoking during gestational period. The association between smoking during pregnancy and RNFL thickness was assessed by a linear regression analysis adjusted for possible confounding factors. RESULTS: Although visual outcomes did not differ between groups, a significant decrease in the RNFL thickness was found in the group of infants exposed to smoke (105.3 vs 95.6; p=0.002), even when adjusting for gestational age, birth weight or gender. CONCLUSIONS: OCT measurements show that intrautero exposure to tobacco smoke interferes with the development of the optic nerve.

Sub-clinical atrophy of the retinal nerve fibre layer in multiple sclerosis.

PURPOSE: This study aimed to evaluate the presence of abnormalities in the retinal nerve fibre layer (RNFL) in multiple sclerosis (MS) patients with normal ophthalmic examination, and to compare the ability of optical coherence tomography (OCT) and scanning laser polarimetry (GDx) to detect axonal loss. METHODS: Patients with MS and disease-free controls were invited to enrol in the study from 1 February 2007 to 30 June 2008. Ophthalmic examination, including evaluation of visual acuity (VA) and visual field (VF), showed normal results in all subjects. Retinal nerve fibre layer properties were measured by means of OCT and GDx. Visual evoked potentials (VEPs) were also recorded. RESULTS: Forty eyes of 40 MS patients and 20 eyes of age- and sex-matched controls were included in the study. Despite normal VA and VF results, significant differences between the two groups were observed in VF mean deviation (MD), most of the RNFL measurements provided by OCT and GDx, and VEP P100 latency and amplitude. There was a significant correlation between OCT and GDx parameters, and between these parameters and VEP results. Nineteen MS eyes (35.7%) showed RNFL abnormalities detected either by OCT or GDx. DISCUSSION: Sub-clinical ganglion cell loss can be detected in MS patients with normal visual function. Both OCT and GDx are useful complementary tools with which to identify this damage.

Ability of optical imaging devices to detect early structural damage in ocular hypertension.

We evaluated the ability of functional and structural technologies to detect early damage in ocular-hypertensive (OHT) eyes with normal standard automated perimetry (SAP) in 48 normal and 130 ocular-hypertensive subjects. We found that optical imaging devices may detect early damage in the RNFL and the optic nerve head in ocular-hypertensive eyes with no defect in SAP.

Diagnostic ability of the Heidelberg retina tomograph, optical coherence tomograph, and scanning laser polarimeter in open-angle glaucoma.

PURPOSE: To compare the ability to discriminate between healthy and glaucomatous eyes of different criteria based on parameters from 3 optical imaging devices: Heidelberg retina tomograph (HRT-II), optical coherence tomograph (Stratus OCT 3000) and scanning laser polarimeter (GDx VCC). DESIGN: Cross-sectional study. PARTICIPANTS: A total of 139 eyes from 139 subjects were enrolled in this study and classified into 66 healthy subjects and 73 glaucomatous patients according to intraocular pressure and standard automated perimetry. METHODS: All the subjects underwent complete ophthalmic examination, including HRT-II, OCT, and GDx VCC evaluations. MAIN OUTCOME MEASURES: Several parameters were obtained by these techniques and 8 diagnostic criteria were assessed. Receiver operating characteristics curves were plotted and compared among them, and sensitivity for specificity higher than 95% was calculated for every criterion. Agreement among the 3 technologies was assessed by means of Venn diagrams. RESULTS: The best criteria discriminating between healthy and glaucomatous eyes were Moorfields regression analysis out of the 95% confidence interval (HRT-II), OCT retinal nerve fiber layer average thickness <77 microm, and nerve fiber indicator >37 (GDx VCC) with sensitivities of 85%, 66%, and 48%, with specificity higher than 95%. Sixty-six patients out of 73 were correctly identified by at least 1 of the devices and 30 were detected by the 3 of them. CONCLUSIONS: Structural criteria assessed by the optical imaging devices evaluated in this study are useful to discriminate glaucomatous damage.