Comparison of intraocular pressure profiles during the water drinking test and the modified diurnal tension curve

OBJECTIVES

To compare intraocular pressure (IOP) during the water drinking test (WDT) and modified diurnal tension curve (mDTC) in open-angle glaucoma (OAG) patients, using multimodal, observer-masked tonometry.

METHODS

Open-angle glaucoma subjects were prospectively enroled, excluding those who had undergone glaucoma filtration or laser surgery. Two-hourly mDTC Goldmann applanation (GAT) and rebound tonometry (RT) was performed between 8:00 and 16:00, and every 15 min for 45 min after ingestion of 800mls of water. Blood pressure, heart rate, pupillometry measurements, and optical coherence tomography (AS-OCT) were also recorded.

RESULTS

Forty-two subjects' right eyes were included. 48% were using topical glaucoma medication. Mean baseline IOP was 14.9 ± 4.52 mmHg, with mean visual field mean deviation (±SD) -5.05 ± 5.45 dB. Strong association was found between maximum IOP during mDTC and WDT (r = 0.90, 95% CI 0.82-0.95 p < 0.0001) with agreement (mDTC-WDT) bias -0.82 mmHg, 95% LoA -1.46 to -0.18. During the WDT, mean systolic blood pressure (±SD) increased from 140.0 ± 20.0 to 153.3 ± 24.0 mmHg (p < 0.0001), mean heart rate ( ± SD) reduced from 69.5 ± 11.3 bpm to 63.6 ± 10.0 bpm (p < 0.0001), and temporal iridocorneal angle increased from 29.2 ± 6.0° to 29.6 ± 5.2° (p = 0.04).

CONCLUSION

This study presents repeated, observer-masked IOP data showing strong correlation between maximum IOP during mDTC and WDT using multimodal tonometry. This supports WDT as a meaningful alternative to mDTC when investigating diurnal IOP characteristics in clinic, with reduced time requirements and associated costs.

How latanoprost changed glaucoma management

Glaucoma is currently considered one of the leading causes of severe visual impairment and blindness worldwide. Topical medical therapy represents the treatment of choice for many glaucoma patients. Introduction of latanoprost, 25 years ago, with an entirely new mechanism of action from that of the antiglaucoma drugs used up to that time was a very important milestone. Since then, due mainly to their efficacy, limited systemic side effects and once daily dosing, prostaglandin analogues (PGAs) have become as the first-choice treatment for primary open-angle glaucoma. PGAs are in general terms well tolerated, although they are associated with several mild to moderate ocular and periocular adverse events. Among them, conjunctival hyperemia, eyelash changes, eyelid pigmentation, iris pigmentation and hypertrichosis around the eyes are the most prevalent. The objective of this paper is to review the role of PGAs in the treatment of glaucoma over the 25 years since the launch of Latanoprost and their impact on clinical practice outcomes.

RP1 Dominant p.Ser740* Pathogenic Variant in 20 Knowingly Unrelated Families Affected by Rod-Cone Dystrophy: Potential Founder Effect in Western Sicily

Background and Objectives. Retinitis pigmentosa (RP) is the most common inherited rod-cone dystrophy (RCD), resulting in nyctalopia, progressive visual field, and visual acuity decay in the late stages. The autosomal dominant form (ADRP) accounts for about 20% of RPs. Among the over 30 genes found to date related to ADRP, RP1 pathogenic variants have been identified in 5-10% of cases. In a cohort of RCD patients from the Palermo province on the island of Sicily, we identified a prevalent nonsense variant in RP1, which was associated with ADRP. The objective of our study was to analyse the clinical and molecular data of this patient cohort and to evaluate the potential presence of a founder effect. Materials and Methods. From 2005 to January 2023, 84 probands originating from Western Sicily (Italy) with a diagnosis of RCD or RP and their relatives underwent deep phenotyping, which was performed in various Italian clinical institutions. Molecular characterisation of patients and familial segregation of pathogenic variants were carried out in different laboratories using Sanger and/or next-generation sequencing (NGS). Results. Among 84 probands with RCD/RP, we found 28 heterozygotes for the RP1 variant c.2219C>G, p.Ser740* ((NM_006269.2)*, which was therefore significantly prevalent in this patient cohort. After a careful interview process, we ascertained that some of these patients shared the same pedigree. Therefore, we were ultimately able to define 20 independent family groups with no traceable consanguinity. Lastly, analysis of clinical data showed, in our patients, that the p.Ser740* nonsense variant was often associated with a late-onset and relatively mild phenotype. Conclusions. The high prevalence of the p.Ser740* variant in ADRP patients from Western Sicily suggests the presence of a founder effect, which has useful implications for the molecular diagnosis of RCD in patients coming from this Italian region. This variant can be primarily searched for in RP-affected subjects displaying compatible modes of transmission and phenotypes, with an advantage in terms of the required costs and time for analysis. Moreover, given its high prevalence, the RP1 p.Ser740* variant could represent a potential candidate for the development of therapeutic strategies based on gene editing or translational read-through therapy for suppression of nonsense variants.

Deep learning to detect macular atrophy in wet age-related macular degeneration using optical coherence tomography

Here, we have developed a deep learning method to fully automatically detect and quantify six main clinically relevant atrophic features associated with macular atrophy (MA) using optical coherence tomography (OCT) analysis of patients with wet age-related macular degeneration (AMD). The development of MA in patients with AMD results in irreversible blindness, and there is currently no effective method of early diagnosis of this condition, despite the recent development of unique treatments. Using OCT dataset of a total of 2211 B-scans from 45 volumetric scans of 8 patients, a convolutional neural network using one-against-all strategy was trained to present all six atrophic features followed by a validation to evaluate the performance of the models. The model predictive performance has achieved a mean dice similarity coefficient score of 0.706 ± 0.039, a mean Precision score of 0.834 ± 0.048, and a mean Sensitivity score of 0.615 ± 0.051. These results show the unique potential of using artificially intelligence-aided methods for early detection and identification of the progression of MA in wet AMD, which can further support and assist clinical decisions.

Detection of macular atrophy in age-related macular degeneration aided by artificial intelligence

INTRODUCTION

Age-related macular degeneration (AMD) is a leading cause of irreversible visual impairment worldwide. The endpoint of AMD, both in its dry or wet form, is macular atrophy (MA) which is characterized by the permanent loss of the RPE and overlying photoreceptors either in dry AMD or in wet AMD. A recognized unmet need in AMD is the early detection of MA development.

AREAS COVERED

Artificial Intelligence (AI) has demonstrated great impact in detection of retinal diseases, especially with its robust ability to analyze big data afforded by ophthalmic imaging modalities, such as color fundus photography (CFP), fundus autofluorescence (FAF), near-infrared reflectance (NIR), and optical coherence tomography (OCT). Among these, OCT has been shown to have great promise in identifying early MA using the new criteria in 2018.

EXPERT OPINION

There are few studies in which AI-OCT methods have been used to identify MA; however, results are very promising when compared to other imaging modalities. In this paper, we review the development and advances of ophthalmic imaging modalities and their combination with AI technology to detect MA in AMD. In addition, we emphasize the application of AI-OCT as an objective, cost-effective tool for the early detection and monitoring of the progression of MA in AMD.

Image processing and supervised machine learning for retinal microglia characterization in senescence

The process of senescence impairs the function of cells and can ultimately be a key factor in the development of disease. With an aging population, senescence-related diseases are increasing in prevalence. Therefore, understanding the mechanisms of cellular senescence within the central nervous system (CNS), including the retina, may yield new therapeutic pathways to slow or even prevent the development of neuro- and retinal degenerative diseases. One method of probing the changing functions of senescent retinal cells is to observe retinal microglial cells. Their morphological structure may change in response to their surrounding cellular environment. In this chapter, we show how microglial cells in the retina, which are implicated in aging and diseases of the CNS, can be identified, quantified, and classified into five distinct morphotypes using image processing and supervised machine learning algorithms. The process involves dissecting, staining, and mounting mouse retinas, before image capture via fluorescence microscopy. The resulting images can then be classified by morphotype using a support vector machine (SVM) we have recently described showing high accuracy. This SVM model uses shape metrics found to correspond with qualitative descriptions of the shape of each morphotype taken from existing literature. We encourage more objective and widespread use of methods of quantification such as this. We believe automatic delineation of the population of microglial cells in the retina, could potentially lead to their use as retinal imaging biomarkers for disease prediction in the future.

In Vivo Detection of Retinal Ganglion Cell Stress in Rodents with DARC

DARC (detection of apoptosing retinal cells) uses fluorescently tagged Annexin A5 to identify retinal apoptosis non-invasively in vivo using a confocal laser scanning ophthalmoscope (cSLO). This can provide insights into the presence and progression of disease pathology and the efficacy of neuroprotective intervention. The methods of administration, imaging, and quantification of DARC, including the operation of the cSLO, are described here.

Automated characterisation of microglia in ageing mice using image processing and supervised machine learning algorithms

The resident macrophages of the central nervous system, microglia, are becoming increasingly implicated as active participants in neuropathology and ageing. Their diverse and changeable morphology is tightly linked with functions they perform, enabling assessment of their activity through image analysis. To better understand the contributions of microglia in health, senescence, and disease, it is necessary to measure morphology with both speed and reliability. A machine learning approach was developed to facilitate automatic classification of images of retinal microglial cells as one of five morphotypes, using a support vector machine (SVM). The area under the receiver operating characteristic curve for this SVM was between 0.99 and 1, indicating strong performance. The densities of the different microglial morphologies were automatically assessed (using the SVM) within wholemount retinal images. Retinas used in the study were sourced from 28 healthy C57/BL6 mice split over three age points (2, 6, and 28-months). The prevalence of 'activated' microglial morphology was significantly higher at 6- and 28-months compared to 2-months (p < .05 and p < .01 respectively), and 'rod' significantly higher at 6-months than 28-months (p < 0.01). The results of the present study propose a robust cell classification SVM, and further evidence of the dynamic role microglia play in ageing.

A proposed theoretical framework for retinal biomarkers

Objective

Propose a theoretical framework for retinal biomarkers of Alzheimer's disease (AD).

Background

The retina and brain share important biological features that are relevant to AD. Developing retinal biomarkers of AD is a strategic priority but as yet none have been validated for clinical use. Part of the reason may be that fundamental inferential assumptions have been overlooked. Failing to recognize these assumptions will disadvantage biomarker discovery and validation, but incorporating them into analyses could facilitate translation.

New theory

The biological assumption that a disease causes analogous effects in the brain and retina can be expressed within a Bayesian network. This allows inferences about abstract theory and individual events, and provides an opportunity to falsify the foundational hypothesis of retina–brain analogy. Graphical representation of the relationships between variables simplifies comparison between studies and facilitates judgements about whether key assumptions are valid given the current state of knowledge.

Major challenges

The framework provides a visual approach to retinal biomarkers and may help to rationalize analysis of future studies. It suggests possible reasons for inconsistent results in existing literature on AD biomarkers.

Linkage to other theories

The framework can be modified to describe alternative theories of retinal biomarker biology, such as retrograde degeneration resulting from brain disease, and can incorporate confounding factors such as co‐existent glaucoma or macular degeneration. Parallels with analogue confirmation theory and surrogate marker validation suggest strengths and weaknesses of the framework that can be anticipated when developing analysis plans.

Highlights

Retinal biomarkers hold great promise for Alzheimer's disease (AD), but none are currently used clinically.

Assumptions about the cause of retinal and brain changes are often overlooked, and this may disadvantage biomarker discovery and validation.

We present a new approach to retinal biomarkers that describes cause and effect graphically in a Bayesian network.

We show how this allows a more complete assessment of how well a biomarker might reflect the brain, and how data from right and left eyes can be used to rule out poor biomarker candidates.

Retinal and Brain Microglia in Multiple Sclerosis and Neurodegeneration

Microglia are the resident immune cells of the central nervous system (CNS), including the retina. Similar to brain microglia, retinal microglia are responsible for retinal surveillance, rapidly responding to changes in the environment by altering morphotype and function. Microglia become activated in inflammatory responses in neurodegenerative diseases, including multiple sclerosis (MS). When activated by stress stimuli, retinal microglia change their morphology and activity, with either beneficial or harmful consequences. In this review, we describe characteristics of CNS microglia, including those in the retina, with a focus on their morphology, activation states and function in health, ageing, MS and other neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, glaucoma and retinitis pigmentosa, to highlight their activity in disease. We also discuss contradictory findings in the literature and the potential ways of reducing inconsistencies in future by using standardised methodology, e.g., automated algorithms, to enable a more comprehensive understanding of this exciting area of research.

Comparison of preserved bimatoprost 0.01% with preservative-free tafluprost: A randomised, investigator-masked, 3-month crossover, multicentre trial, SPORT II

IMPORTANCE

This study compares the efficacy and tolerability of a preservative-free prostaglandin analogue (tafluprost 15 mg/ml) to a prostaglandin analogue that uses 0.02% of benzalkonium chloride (bimatoprost 0.1 mg/ml).

BACKGROUND

Different prostaglandin analogues have been commercially approved, with differences in tolerability.

DESIGN

Prospective, randomised, investigator-masked, 3-month crossover, multicentre trial.

PARTICIPANTS

Sixty-four patients with ocular hypertension or open-angle glaucoma were randomised to two groups, after a 4-week washout period from their current topical drop regimen.

METHODS

Participants were randomised to tafluprost (Group 1; n = 33) or bimatoprost (Group 2; n = 31). At month 3, each group switched to the opposite treatment. IOP was evaluated at multiple timepoints.

MAIN OUTCOME MEASURES

The primary outcome was difference in mean IOP between the two groups at the final visit. Secondary outcomes included change from baseline IOP at month 3 and month 6, difference in mean IOP at month 3 and difference in IOP at all timepoints. Safety outcomes included best-corrected visual acuity (BCVA), adverse events, ocular tolerability, optic nerve assessment and slit lamp biomicroscopy.

RESULTS

Both medications significantly lowered IOP at month 6 compared to baseline: 5.4 mmHg (27%) for tafluprost and 6.8 mmHg (33%) for bimatoprost (p < 0.0001). No significant differences in any of the safety measures (including conjunctival hypearemia) were detected.

CONCLUSIONS AND RELEVANCE

Bimatoprost produced a statistically significant greater IOP reduction compared to tafluprost with minimal to no difference in side effects. This should be borne in mind when weighing up the pros and cons of preserved versus preservative-free prostaglandin analogue therapy.

CLINICALTRIALS.GOV IDENTIFIER

NCT02471105.

Phytochemical characterization and biological activities of Plectranthus barbatus Andrews

Plectranthus barbatus Andrews (Lamiaceae) is widely distributed in the world and has a range of popular therapeutic indications. This work aimed to evaluate the phytochemical characterization of two leaf extracts of P. barbatus, and their antimicrobial, antineoplastic and immunomodulatory potential. After collection, herborization and obtainment of the P. barbatus aqueous extract (PBA) and acetone:water 7:3 P. barbatus organic extract (PBO), the phytochemical characterization was performed by high-performance liquid chromatography (HPLC). The antimicrobial activity was performed to determine the minimum inhibitory concentration (MIC) against eight bacterial strains using the microdilution test and the fungus Trichophyton rubrum by disc diffusion assay and microdilution test. Cytotoxicity was assessed by MTT and trypan blue methods in normal peripheral blood mononuclear cells (PBMCs) at concentrations ranged between 0.1 to 100 µg.mL-1 and in neoplastic cell lines Toledo, K562, DU-145 and PANC-1 at 1, 10 and 100 µg.mL-1 . Immunomodulatory activity, was evaluated by sandwich ELISA of proinflammatory cytokines at BALB/c mice splenocytes cultures supernatant. Both extracts presented flavonoids, cinnamic derivatives, steroids and ellagic acid. PBO showed bacteriostatic activity against Acinetobacter baumannii (MIC = 250 µg.mL-1) clinical isolate and PBA fungistatic activity against Trichophyton rubrum (MIC = 800 µg.mL-1). The extracts did not exhibit toxicity to PBMCs and neoplastic cells (IC50 > 100 µg.mL-1). Additionally, PBO at 100 µg.mL-1 significantly inhibited IFN-γ and IL-17A cytokines (p = 0.03). Plectranthus barbatus is a potential candidate for therapeutic use due to its low toxicity in healthy human cells and exhibits biological activities of medical interest as bacteriostatic, fungistatic and immunomodulatory.

Predicting wet age-related macular degeneration (AMD) using DARC (detecting apoptosing retinal cells) AI (artificial intelligence) technology

OBJECTIVES

To assess a recently described CNN (convolutional neural network) DARC (Detection of Apoptosing Retinal Cells) algorithm in predicting new Subretinal Fluid (SRF) formation in Age-related-Macular-Degeneration (AMD).

METHODS

Anonymized DARC, baseline and serial OCT images (n = 427) from 29 AMD eyes of Phase 2 clinical trial (ISRCTN10751859) were assessed with CNN algorithms, enabling the location of each DARC spot on corresponding OCT slices (n = 20,629). Assessment of DARC in a rabbit model of angiogenesis was performed in parallel.

RESULTS

A CNN DARC count >5 at baseline was significantly (p = 0.0156) related to development of new SRF throughout 36 months. Prediction rate of eyes using unique DARC spots overlying new SRF had positive predictive values, sensitivities and specificities >70%, with DARC count significantly (p < 0.005) related to the magnitude of SRF accumulation at all time points. DARC identified earliest stages of angiogenesis in-vivo.

CONCLUSIONS

DARC was able to predict new wet-AMD activity. Using only an OCT-CNN definition of new SRF, we demonstrate that DARC can identify early endothelial neovascular activity, as confirmed by rabbit studies. Although larger validation studies are required, this shows the potential of DARC as a biomarker of wet AMD, and potentially saving vision-loss.

The efficacy of dexamethasone implants following anti-VEGF failure for macular oedema in retinal vein occlusion

PURPOSE

To investigate the efficacy of intravitreal dexamethasone implants (DEX) after anti-VEGF failure in retinal vein occlusion macular oedema.

METHODS

Retrospective cohort study of DEX implant (0.7 mg) given after anti-VEGF 'failure'. Switch to DEX occurred if a ⩽ +5 ETDRS letter gain and ⩽20% reduction in central subfield thickness was present following ⩾6 consecutive anti-VEGF injections. The primary endpoint was VA change 30 days after DEX. Secondary outcomes were peak VA change, VA change at monthly timepoints, percentage achieving 15-letter gain, central subfield thickness (CST) and intraocular pressure (IOP).

RESULTS

Sixty-two injections in 62 patients associated with 26% central retinal vein occlusion (CRVO) and 74% branch retinal vein occlusion (BRVO) were eligible. There was a modest, significant improvement in mean VA change at 30 days compared to baseline (+6 letters, 95% CI +2.2 to +9.1 letters, p < 0.01). DEX implant significantly improved mean peak VA change compared to preceding anti-VEGF by +18.1 letters in CRVO (p = 0.002) and +13.2 letters in BRVO (p < 0.0001). IOP peaked between 30 and 60 days following injection, with 31% of CRVO and 11% of BRVO patients experiencing an IOP ⩾ 25 mmHg.

CONCLUSION

DEX implant provides useful rescue therapy in cases of anti-VEGF 'failure' for macular oedema following retinal vein occlusion, resulting in improved functional outcomes at 30 days.

Transcutaneous fluorescence spectroscopy as a tool for non-invasive monitoring of gut function: first clinical experiences

Gastro-intestinal function plays a vital role in conditions ranging from inflammatory bowel disease and HIV through to sepsis and malnutrition. However, the techniques that are currently used to assess gut function are either highly invasive or unreliable. Here we present an alternative, non-invasive sensing modality for assessment of gut function based on fluorescence spectroscopy. In this approach, patients receive an oral dose of a fluorescent contrast agent and a fibre-optic probe is used to make fluorescence measurements through the skin. This provides a readout of the degree to which fluorescent dyes have permeated from the gut into the blood stream. We present preliminary results from our first measurements in human volunteers demonstrating the potential of the technique for non-invasive monitoring of multiple aspects of gastro-intestinal health.

A CNN-aided method to predict glaucoma progression using DARC (Detection of Apoptosing Retinal Cells)

BACKGROUND

A key objective in glaucoma is to identify those at risk of rapid progression and blindness. Recently, a novel first-in-man method for visualising apoptotic retinal cells called DARC (Detection-of-Apoptosing-Retinal-Cells) was reported. The aim was to develop an automatic CNN-aided method of DARC spot detection to enable prediction of glaucoma progression.

METHODS

Anonymised DARC images were acquired from healthy control (n=40) and glaucoma (n=20) Phase 2 clinical trial subjects (ISRCTN10751859) from which 5 observers manually counted spots. The CNN-aided algorithm was trained and validated using manual counts from control subjects, and then tested on glaucoma eyes.

RESULTS

The algorithm had 97.0% accuracy, 91.1% sensitivity and 97.1% specificity to spot detection when compared to manual grading of 50% controls.  It was next tested on glaucoma patient eyes defined as progressing or stable based on a significant (p<0.05) rate of progression using OCT-retinal nerve fibre layer measurements at 18 months. It demonstrated 85.7% sensitivity, 91.7% specificity with AUC of 0.89, and a significantly (p=0.0044) greater DARC count in those patients who later progressed.

CONCLUSION

This CNN-enabled algorithm provides an automated and objective measure of DARC, promoting its use as an AI-aided biomarker for predicting glaucoma progression and testing new drugs.

Retinal correlates of psychiatric disorders

Diagnosis and monitoring of psychiatric disorders rely heavily on subjective self-reports of clinical symptoms, which are complicated by the varying consistency of accounts reported by patients with an impaired mental state. Hence, more objective and quantifiable measures have been sought to provide clinicians with more robust methods to evaluate symptomology and track progression of disease in response to treatments. Owing to the shared origins of the retina and the brain, it has been suggested that changes in the retina may correlate with structural and functional changes in the brain. Vast improvements in retinal imaging, namely optical coherence tomography (OCT) and electrodiagnostic technology, have made it possible to investigate the eye at a microscopic level, allowing for the investigation of potential biomarkers in vivo. This review provides a summary of retinal biomarkers associated with schizophrenia, bipolar disorder and major depression, demonstrating how retinal biomarkers may be used to complement existing methods and provide structural markers of pathophysiological mechanisms that underpin brain dysfunction in psychiatric disorders.

Novel USH1G homozygous variant underlying USH2-like phenotype of Usher syndrome

PURPOSE

Usher syndrome (USH) is an autosomal recessive disorder characterized by congenital sensorineural hearing impairment and retinitis pigmentosa. Classification distinguishes three clinical types of which type I (USH1) is the most severe, with vestibular dysfunction as an added feature. To date, 15 genes and 3 loci have been identified with the USH1G gene being an uncommon cause of USH. We describe an atypical USH1G-related phenotype caused by a novel homozygous missense variation in a patient with profound hearing impairment and relatively mild retinitis pigmentosa, but no vestibular dysfunction.

METHODS

A 26-year-old female patient with profound congenital sensorineural hearing loss, nyctalopia and retinitis pigmentosa was studied. Audiometric, vestibular and ophthalmologic examination was performed. A panel of 13 genes was tested by next-generation sequencing (NGS).

RESULTS

While the hearing loss was confirmed to be profound, the vestibular function resulted normal. Although typical retinitis pigmentosa was present, the age at onset was unusually late for USH1 syndrome. A novel homozygous missense variation (c.1187T>A, p.Leu396Gln) in the USH1G gene has been identified as causing the disease in our patient.

CONCLUSIONS

Genetic and phenotypic heterogeneity are very common in both isolated and syndromic retinal dystrophies and sensorineural hearing loss. Our findings widen the spectrum of USH allelic disorders and strength the concept that variants in genes that are classically known as underlying one specific clinical USH subtype might result in unexpected phenotypes.

Multimodal Imaging in Autosomal Dominant Cone-Rod Dystrophy Caused by Novel CRX Variant

AIM

To characterize by multimodal approach the phenotype of patients from a 3 generations pedigree, affected by autosomal dominant cone-rod dystrophy (CRD), found to carry a novel pathogenic variant in the cone-rod homeobox-containing (CRX) gene.

METHODS

Examination of the adult patients included the following tests: visual acuity, multicolour imaging, spectral domain optical coherence tomography (SD-OCT), fundus autofluorescence (FAF) and OCT angiography (OCT-A) recordings. In a 2.5-year-old child, cycloplegic refraction, fundoscopy, ocular motility evaluation and electrophysiological exams were performed. Next Generation Sequencing of patients' DNA has been carried out.

RESULTS

A novel CRX pathogenic variant has been identified in our patients. The 2.5-year-old child in the third generation was found to have inherited the variant, with no clinical signs of the condition, but electroretinographic abnormalities in the scotopic component. In the adult patients, diffuse atrophy of the retinal pigment epithelium/photoreceptor complex in the macular region was evident at the OCT and FAF, while OCT-A showed choriocapillaris density reduction.

CONCLUSIONS

Multimodal study allowed the characterization of a peculiar form of CRD. The novel pathogenic variant seems to have a different effect on the phenotype if compared with a previously described similar one, giving an insight into the pathogenic mechanism of CRX-related retinal dystrophies and offering valuable information that could lead to the development of possible future therapies.

Real-Time Imaging of Retinal Ganglion Cell Apoptosis

Monitoring real-time apoptosis in-vivo is an unmet need of neurodegeneration science, both in clinical and research settings. For patients, earlier diagnosis before the onset of symptoms provides a window of time in which to instigate treatment. For researchers, being able to objectively monitor the rates of underlying degenerative processes at a cellular level provides a biomarker with which to test novel therapeutics. The DARC (Detection of Apoptosing Retinal Cells) project has developed a minimally invasive method using fluorescent annexin A5 to detect rates of apoptosis in retinal ganglion cells, the key pathological process in glaucoma. Numerous animal studies have used DARC to show efficacy of novel, pressure-independent treatment strategies in models of glaucoma and other conditions where retinal apoptosis is reported, including Alzheimer’s disease. This may forge exciting new links in the clinical science of treating both cognitive and visual decline. Human trials are now underway, successfully demonstrating the safety and efficacy of the technique to differentiate patients with progressive neurodegeneration from healthy individuals. We review the current perspectives on retinal ganglion cell apoptosis, the way in which this can be imaged, and the exciting advantages that these future methods hold in store.

Memantine-Loaded PEGylated Biodegradable Nanoparticles for the Treatment of Glaucoma

Glaucoma is a multifactorial neurodegenerative disease associated with retinal ganglion cells (RGC) loss. Increasing reports of similarities in glaucoma and other neurodegenerative conditions have led to speculation that therapies for brain neurodegenerative disorders may also have potential as glaucoma therapies. Memantine is an N-methyl-d-aspartate (NMDA) antagonist approved for Alzheimer's disease treatment. Glutamate-induced excitotoxicity is implicated in glaucoma and NMDA receptor antagonism is advocated as a potential strategy for RGC preservation. This study describes the development of a topical formulation of memantine-loaded PLGA-PEG nanoparticles (MEM-NP) and investigates the efficacy of this formulation using a well-established glaucoma model. MEM-NPs <200 nm in diameter and incorporating 4 mg mL^-1 of memantine were prepared with 0.35 mg mL^-1 localized to the aqueous interior. In vitro assessment indicated sustained release from MEM-NPs and ex vivo ocular permeation studies demonstrated enhanced delivery. MEM-NPs were additionally found to be well tolerated in vitro (human retinoblastoma cells) and in vivo (Draize test). Finally, when applied topically in a rodent model of ocular hypertension for three weeks, MEM-NP eye drops were found to significantly (p < 0.0001) reduce RGC loss. These results suggest that topical MEM-NP is safe, well tolerated, and, most promisingly, neuroprotective in an experimental glaucoma model.

Refractive outcome of combined phacoemulsification and endoscopic cyclophotocoagulation

PURPOSE

To compare the refractive outcome of eyes that underwent phacoemulsification combined with endoscopic cyclophotocoagulation (phaco-ECP) with the eyes that underwent phacoemulsification alone.

METHODS

A retrospective case series review of 103 consecutive eyes that underwent phaco-ECP and 62 eyes that underwent phacoemulsification between January 2006 and August 2012 was conducted. Post-operative refractive outcomes were obtained by subjective refraction or autorefraction. Demographic data, best corrected visual acuity, intraocular pressure, number of glaucoma agents and mean deviation of the Humphrey visual field test (MD) were also analysed.

RESULTS

The total number of eyes included in the study was 62 eyes for the phaco-ECP group and 62 eyes for the control group who underwent phacoemulsification alone. More than 90% of eyes (n = 56) in phaco-ECP group achieved post-operative refraction within ±1 dioptre (D) of the target refraction. In the control group, 100% of eyes achieved post-operative refraction within ±1D of the target refraction. When comparing the difference between the target and the actual refractive outcome between the phaco-ECP and the control group, there was no statistically significant difference.

CONCLUSIONS

Refractive outcome after phaco-ECP is comparable to phacoemulsification alone. This study suggests that the intraocular lens power can be selected for cataract surgery alone and that ECP does not change the effective lens position significantly; therefore, no modification of biometry formulae is required. Phaco-ECP should be considered as an effective, safe and predictable surgical treatment option for glaucoma patients with co-existing cataract.

Glaucoma: the retina and beyond

Over 60 million people worldwide are diagnosed with glaucomatous optic neuropathy, which is estimated to be responsible for 8.4 million cases of irreversible blindness globally. Glaucoma is associated with characteristic damage to the optic nerve and patterns of visual field loss which principally involves the loss of retinal ganglion cells (RGCs). At present, intraocular pressure (IOP) presents the only modifiable risk factor for glaucoma, although RGC and vision loss can continue in patients despite well-controlled IOP. This, coupled with the present inability to diagnose glaucoma until relatively late in the disease process, has led to intense investigations towards the development of novel techniques for the early diagnosis of disease. This review outlines our current understanding of the potential mechanisms underlying RGC and axonal loss in glaucoma. Similarities between glaucoma and other neurodegenerative diseases of the central nervous system are drawn before an overview of recent developments in techniques for monitoring RGC health is provided, including recent progress towards the development of RGC specific contrast agents. The review concludes by discussing techniques to assess glaucomatous changes in the brain using MRI and the clinical relevance of glaucomatous-associated changes in the visual centres of the brain.

Protective role of free and quercetin-loaded nanoemulsion against damage induced by intracerebral haemorrhage in rats

Intracerebral haemorrhage (ICH) is a worldwide public health problem. Experimental studies have shown that oxidative stress plays an important role in the pathogenesis of ICH and could represent a target for its treatment. However, the blood-brain barrier is an obstacle to be overcome, as it hampers the administration of compounds to the central nervous system. In this study, we compared the effects of a quercetin-loaded nanoemulsion (QU-N) with the free form of the drug (QU-SP) in a collagenase-induced ICH rat model. Quercetin (QU) is a polyphenol that has an antioxidant effect in vitro, but due to its high lipophilicity, it has low bioavailability in vivo. In this study, animals submitted or not to ICH were treated with a single intraperitoneal QU dose (free or nanoemulsion) of 30 mg kg(-1). Motor assessment was evaluated by the open field, foot fault and beam walking behavioural tests. 72 h after surgery the haematoma size was evaluated and biochemical measurements were performed. Animals treated with QU-N had a significant improvement in the beam walking and open field tests. Also, QU-N was able to reduce the size of the haematoma, preserving the activity of glutathione S-transferase (GST), increasing GSH content, and the total antioxidant capacity. QU-SP recovered locomotor activity and increased the GSH content and the total antioxidant capacity. Thus, it can be observed that QU presented antioxidant activity in both formulations, but the incorporation into nanoemulsions increased its antioxidant effect, which was reflected in the improvement of the motor skills and in the haematoma size decrement. These results suggest that the nanoemulsion containing QU developed in this study could be promising for future studies on treatments for ICH.

Dendritic changes in rat visual pathway associated with experimental ocular hypertension

PURPOSE

Increasing evidence shows that structural changes in dendrites play an important role in neuronal degenerative processes. The aims of this study were to characterize and delineate morphological changes of dendrites in retinal ganglion cells (RGCs) and their central target neurons in the superior colliculus (SC) and lateral geniculate nucleus (LGN) in experimental rat glaucoma.

METHODS

Chronic ocular hypertension (OHT) was surgically induced in rats and animals were sacrificed at 1, 4, 8, 16 and 32 weeks following IOP elevation. Animals without IOP elevation served as normal control. Dendritic morphology of neurons was visualized by ex vivo DiI labelling using confocal microscopy and dendritic length and number was quantified using Image J.

RESULTS

We found significant dendritic shrinkage (p < 0.001) and loss (p < 0.001) in RGCs and neurons in the SC and LGN in OHT animals compared to age-matched controls. Analysis of the temporal morphological profiles among them revealed the RGCs to have the earliest changes compared to the SC and LGN although the most prominent changes occurred in the SC.

CONCLUSION

Our study has demonstrated that OHT results in dendritic changes of the neurons throughout the visual pathways, from RGCs to SC cells and LGN cells, suggesting that both the retina and the brain should be targeted when considering diagnosis and therapeutic strategies for glaucoma.

In vivo imaging of retinal ganglion cell apoptosis

Apoptosis, or programmed cell death, plays a vital role in normal development and ageing. However, dysregulation of this process is responsible for many disease states including; cancer, autoimmune and neurodegeneration. For this reason, in vivo visualisation of apoptosis may prove a useful tool for both laboratory research and clinical diagnostics. Glaucoma comprises a distinctive group of chronic optic neuropathies, characterised by the progressive loss of retinal ganglion cells (RGCs). Early diagnosis of glaucoma remains a clear and unmet need. Recently, there have been significant advances in the detection of apoptosis in vivo using fluorescent probes to visualise single RGCs undergoing apoptosis, specifically DARC (Detection of Apoptotic Retinal Cells) [1] and capQ technology [2(••)].

Glaucoma and Alzheimer’s disease in the elderly

Primary open angle glaucoma and Alzheimer’s disease have long been established as two separate pathological entities, primarily affecting the elderly. The progressive, irreversible course of both diseases has significant implications on an aging population. As the complex pathophysiology of the two diseases has progressively unraveled over the past two decades, common pathophysiological changes have also been elucidated. Some of these mechanisms have established a strong grounding, whilst others remain principally speculative. The mutual neuropathological changes in primary open angle glaucoma and Alzheimer’s disease have facilitated the development of neuroprotective strategies. While most of these strategies are still in the preclinical phase, they have shown great promise in experimental animal studies. Further understanding of the common pathophysiology of primary open angle glaucoma and Alzheimer’s disease and their timeline may have great implications on early diagnosis and effective therapeutic targeting.

Changes in NMDA receptor contribution to synaptic transmission in the brain in a rat model of glaucoma

In the age-related, blinding disease glaucoma, retinal ganglion cells (RGCs) degenerate, possibly affecting glutamatergic retinofugal transmission to the brain. The superior colliculus (SC) is a major central target of retinofugal axons in the rodent, a much used disease model. We investigated the contribution of NMDA-type glutamate receptors to retinocollicular transmission in a rat glaucoma model, using a SC brain slice preparation to determine the sensitivity of synaptic responses to the NMDAR antagonist D-AP5. At 32 weeks after induction of experimental glaucoma, but not earlier, there was an increase in NMDAR contribution to SC synaptic responses in slices receiving input from glaucomatous eyes. This suggests that there are changes in NMDAR function after RGC degeneration in experimental glaucoma, which may represent functional SC compensation through plasticity via NMDARs. This has implications for studies carried out using rodent glaucoma models, especially those evaluating potential treatment strategies, as it suggests that functional changes in the central visual system need to be considered in addition to those in the eye. Furthermore, the data underline the need for early therapeutic intervention in order to pre-empt subsequent central functional changes.

Imaging multiple phases of neurodegeneration: a novel approach to assessing cell death in vivo

Nerve cell death is the key event in all neurodegenerative disorders, with apoptosis and necrosis being central to both acute and chronic degenerative processes. However, until now, it has not been possible to study these dynamically and in real time. In this study, we use spectrally distinct, well-recognised fluorescent cell death markers to enable the temporal resolution and quantification of the early and late phases of apoptosis and necrosis of single nerve cells in different disease models. The tracking of single-cell death profiles in the same living eye over hours, days, weeks and months is a significant advancement on currently available techniques. We identified a numerical preponderance of late-phase versus early-phase apoptotic cells in chronic models, reinforcing the commonalities between cellular mechanisms in different disease models. We showed that MK801 effectively inhibited both apoptosis and necrosis, but our findings support the use of our technique to investigate more specific anti-apoptotic and anti-necrotic strategies with well-defined targets, with potentially greater clinical application. The optical properties of the eye provide compelling opportunities for the quantitative monitoring of disease mechanisms and dynamics in experimental neurodegeneration. Our findings also help to directly observe retinal nerve cell death in patients as an adjunct to refining diagnosis, tracking disease status and assessing therapeutic intervention.

En face optical coherence tomography: a new method to analyse structural changes of the optic nerve head in rat glaucoma

AIM

To investigate en face optical coherence tomography (eOCT) and its use as an effective objective technique for assessing changes in the glaucomatous rat optic nerve head (ONH) in vivo, and compare it with confocal scanning laser ophthalmoscopy (cSLO).

METHODS

18 Dark Agouti (DA) rats with surgically induced ocular hypertension were imaged with eOCT and cSLO at regular intervals. Assessment included three dimensional (3D) topographic reconstructions, intensity z-profile plots, a new method of depth analysis to define a "multilayered" structure, and scleral canal measurements, in relation to the degree of intraocular pressure (IOP) exposure.

RESULTS

The increased depth resolution of the eOCT compared to the cSLO was apparent in all methods of analysis, with better discrimination of tissue planes. This was validated histologically. eOCT demonstrated several significant changes in imaged rat ONH which correlated with IOP exposure, including the area of ONH (p<0.01), separation between retinal vessel and scleral layers (p<0.05), and anterior scleral canal opening expansion (p<0.05).

CONCLUSION

eOCT appears to be effective in assessing rat ONH, allowing detailed structural analysis of the multilayered ONH structure. As far as the authors are aware, this is the first report of scleral canal expansion in a rat model. They suggest eOCT as a novel method for the detection of early changes in the ONH in glaucoma.

Birth of normal kids after microinjection of pronuclear embryos in a transgenic goat (Capra hircus) production program in Brazil

This pilot project was designed to determine if normal kids could be produced after microinjection in pronuclear embryos and subsequent transfer to recipients in a transgenic goat program in Brazil. Twelve donors of the Saanen breed and 17 recipients of an undefined breed were used. The estrus of both donors and recipients was synchronized by a standard progestagen treatment and superovulation obtained by six pFSH injections. Donors in estrus were mated with fertile Saanen bucks. Zygotes were recovered surgically by flushing oviducts. The recovered zygotes with visible pronuclei were microinjected with 500 to 1000 copies of the human G-CSF gene. Two or four embryos were surgically transferred into the oviducts of recipients. One recipient became pregnant and two kids were born. No transgenic goat was identified after PCR analysis. Even though transgenic goats were not obtained, this experiment establishes the basis of a synchronization and superovulation regimen for use in goats raised in Brazil, for the purpose of collecting and manipulating the pronuclear embryos. This project also showed that microinjected one-cell goat embryos can survive to produce live young following surgical transfer.

Novel antisense oligonucleotides targeting TGF-beta inhibit in vivo scarring and improve surgical outcome

The scarring response is an important factor in many diseases throughout the body. In addition, it is a major problem in influencing results of surgery. In the eye, for example, post-operative scarring can determine the outcome of surgery. This is particularly the case in the blinding disease glaucoma, where several anti-scarring regimens are currently used to improve glaucoma surgery results, but are of limited use clinically because of severe complications. We have recently identified transforming growth factor-beta (TGF-beta) as a target for post-operative anti-scarring therapy in glaucoma, and now report the first study of novel second-generation antisense phosphorothioate oligonucleotides against TGF-beta in vivo. Single applications of a TGF-beta OGN at the time of surgery in two different animal models closely related to the surgical procedure performed in glaucoma patients, significantly reduced post-operative scarring (P<0.05) and improved surgical outcome. Our findings suggest that TGF-beta antisense oligonucleotides have potential as a new therapy for reducing post-surgical scarring. Its long-lasting effects after only a single administration at the time of surgery make it particularly attractive clinically. Furthermore, although we have shown this agent to be useful in the eye, it could have widespread applications anywhere in the body where the wound-healing response requires modulation.

Modulation of wound healing after glaucoma surgery

The healing process after glaucoma filtration is the main determinant of surgical failure and, even more important, the final intraocular pressure. The ability to fully control wound healing may ultimately give us the ability to set the intraocular pressure in the low teens for all patients undergoing glaucoma filtration surgery. The authors review the changes in how to use antimetabolites to improve safety, and many of the exciting new areas of progress, including growth factor neutralization and future molecular therapies to control wound healing.

The role of the immune system in conjunctival wound healing after glaucoma surgery

The immune system has a fundamental role in the development and regulation of ocular healing, which plays an important role in the pathogenesis of most blinding diseases. This review discusses the mechanisms of normal wound healing, describing the animal and fetal wound healing models used to provide further insight into normal wound repair. In particular, conjunctival wound repair after glaucoma filtration surgery will be used to illustrate the contributions that the different components of the immune system make to the healing process. The potential role of macrophages, the possible regulatory effect of lymphocytes, and the important role of growth factors and cytokines in the wound healing reaction are discussed. The significance of the immune system in the pathogenesis of aggressive conjunctival scarring is addressed, particularly assessing the predisposing factors, including drugs, age, and ethnicity. The rationale behind the pharmacological agents currently used to modulate the wound healing response and the effects these drugs have on the function of the immune system are described. Finally, potential new therapeutic approaches to regulating the wound healing response are reported.