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.

Cyclodiode vs micropulse transscleral laser treatment

BACKGROUND

Continuous-wave transscleral cyclophotocoagulation (CW-TSCP) is usually reserved for advanced/refractory glaucoma. Micropulse transscleral laser therapy (MPTLT) utilises short energy pulses separated by 'off'-periods. MPTLT is postulated to have fewer complications, but its relative efficacy is not known. The National Institute for Health and Care Excellence (NICE) has deemed the evidence supporting MPTLT use of inadequate quality, limiting its use to research. This study aims to evaluate MPTLT efficacy and safety compared to CW-TSCP.

METHODS

This 24-month follow-up retrospective audit included 85 CW-TSCP and 173 MPTLT eyes at a London tertiary referral centre. Primary outcome was success rate at the last follow-up; defined as at least 20% intraocular pressure (IOP) reduction with the same/fewer medications, and IOP between 6 and 18 mmHg. Secondary outcomes were acetazolamide use and success rates per glaucoma type. Safety outcomes were reported as complication rates.

RESULTS

By 24-months, mean IOP reduced from 34.6[±1.4]mmHg to 19.0[ ± 3.0]mmHg post-CW-TSCP (p < 0.0001); and from 26.1[±0.8]mmHg to 19.1[±2.2]mmHg post-MPTLT (p < 0.0001). Average IOP decreased by 45.1% post-CW-TSCP, and 26.8% post-MPTLT. Both interventions reduced medication requirements (p ≤ 0.05). More CW-TSCP patients discontinued acetazolamide (p = 0.047). Overall success rate was 26.6% for CW-TSCP and 30.6% for MPTLT (p = 0.83). Only primary closed-angle glaucoma saw a significantly higher success rate following CW-TSCP (p = 0.014). CW-TSCP complication rate was significantly higher than MPTLT (p = 0.0048).

CONCLUSION

Both treatments significantly reduced IOP and medication load. CW-TSCP had a greater absolute/proportionate IOP-lowering effect, but it carried a significantly greater risk of sight-threatening complications. Further prospective studies are required to evaluate MPTLT compared to CW-TSCP.

Effects of COVID-19 pandemic on glaucoma appointment scheduling in a tertiary hospital in London, UK

PURPOSE

To investigate the impact of the delay in patient appointments caused by the COVID-19 pandemic and the triage system on the glaucomatous disease of patients in a London tertiary hospital.

METHODS

Observational retrospective study that randomly selected 200 glaucoma patients with more than 3 months of unintended delay for their post-COVID visit and other inclusion and exclusion criteria. Demographic information, clinical data, number of drugs, best-corrected visual acuity (BCVA), intraocular pressure (IOP), visual field (VF) mean deviation (MD), and global peripapillary retinal nerve fibre layer (pRNFL) thickness were obtained from the pre- and post-COVID visit. At the post-COVID visit, the clinical outcomes subjective clinical concern and change of treatment or need for surgery were also annotated. The variables were stratified by glaucoma severity (according to the MD into early, moderate and advanced) and by delay time (more and less than 12 months) and analysed using SPSS.

RESULTS

We included 121 eyes (from 71 patients). The median patient age was 74 years (interquartile range -IQR- 15), 54% were males and 52% Caucasians. Different glaucoma types and all glaucoma severities were included. When data was stratified for glaucoma severity, at the pre-COVID visit, significant differences in BCVA, CCT and IOP were observed and there were significantly higher values in the early glaucoma group. The median follow-up delay was 11 months (IQR 8), did not differ between the glaucoma severity groups and did not correlate to the glaucoma severity. At the post-COVID visit, significant differences in BCVA, IOP, and Global pRNFL thickness were observed between the glaucoma severity groups, as lower BCVA and higher IOP and pRNFL thickness were observed in the early glaucoma group. At the post-COVID visit there was cause for concern in 40 eyes: 5 were followed more closely, 22 had a change of treatment and 13 were booked for surgery (3 for cataract and 10 for glaucoma surgery). However, the number of eyes with causes for concern were similar between the glaucoma severity groups and there was no correlation between these clinical outcomes and the delay of the post-COVID visit. The number of topical hypotensive medications increased significantly after the post-COVID visit, higher number of medications were observed in the advanced glaucoma group. When differences of IOP, MD and pRNFL thickness between the pre and post-COVID visit, only the MD difference was significantly different between the glaucoma severity groups because it was higher in the severe group. When data was stratified for delay longer or shorter than 12 months, no differences were observed between the groups except at the pre-COVID visit, when the numbers of patients with MD deviation >-6 dB had longer delay time. When differences in IOP, MD and RNFL thickness were calculated, only the pRNFL thickness showed significant differences between the delay groups, because it was higher in the longer delay group. Finally, when paired analysis of the variables at the pre- and post-COVID visits, stratified by glaucoma severity and delay were conducted, although there were no significant differences in IOP in any group, the BCVA decreased significantly in the overall group and in the longer delay groups, the number of hypotensive drugs increased significantly overall and in the moderate and advanced glaucoma, the MD of the VF worsened significantly in the overall group and in the early glaucoma and longer delay groups and the pRNFL thickness decreased significantly in all groups.

CONCLUSIONS

We document that delayed care impacts negatively on the glaucomatous disease of our patients because at the post-COVID visit there were reasons for clinical concern in a third of eyes that resulted in change of treatment or surgery. However, these clinical consequences were not related to IOP, glaucoma severity or delay time and reflect that the triage methods implemented worked adequately. The most sensitive parameter to indicate progression in our sample was the pRNFL thickness.

Glaucoma Rose Plot Analysis: Detecting Early Structural Progression Using Angular Histograms

PURPOSE

To evaluate the novel Rose Plot Analysis (RPA) in the analysis and presentation of glaucoma structural progression data.

DESIGN

Case-control image analysis study using retrospective retinal imaging series.

SUBJECTS

Subjects with open-angle glaucoma with at least 5 registered spectral-domain OCT scans.

METHODS

Glaucoma RPA was developed, combining a novel application of angular histograms and dynamic cluster analysis of circumpapillary retinal nerve fiber layer (cRNFL) OCT data. Rose Plot Analysis plots were created for each eye and each visit. Significant clusters of progression were indicated in red. Three masked clinicians categorized all RPA plots (progressing, not progressing), in addition to measuring the significant RPA area. A masked OCT series assessment with linear regression of averaged global and sectoral cRNFL thicknesses was conducted as the clinical imaging standard.

MAIN OUTCOME MEASURES

Interobserver agreement was compared between RPA and the clinical imaging standard. Discriminative ability was assessed using receiver-operating characteristic curves. The time to detection of progression was compared using a Kaplan-Meier survival analysis, and the agreement of RPA with the clinical imaging standard was calculated.

RESULTS

Seven hundred fourty-three scans from 98 eyes were included. Interobserver agreement was significantly greater when categorizing RPA (κ, 0.86; 95% confidence interval [CI], 0.81-0.91) compared with OCT image series (κ, 0.66; 95% CI, 0.54-0.77). The discriminative power of RPA to differentiate between eyes that were progressing and not progressing (area under the curve [AUC], 0.97; 95% CI, 0.92-1.00) was greater than that of global cRNFL thickness (AUC, 0.71; 95% CI, 0.59-0.82; P < 0.0001) and equivalent to that of sectoral cRNFL regression (AUC, 0.97; 95% CI, 0.92-1.00). A Kaplan-Meier survival analysis showed that progression was detected 8.7 months sooner by RPA than by global cRNFL linear regression (P < 0.0001) in progressing eyes but was not sooner than with sectoral cRNFL (P = 0.06). Rose Plot Analysis showed substantial agreement with the presence of significant thinning on sectoral cRNFL linear regression (κ, 0.715; 95% CI, 0.578-0.853).

CONCLUSIONS

Rose Plot Analysis has been shown to provide accurate and intuitive, at-a-glance data analysis and presentation that improve interobserver agreement and may aid early diagnosis of glaucomatous disease progression.

Recent advances in imaging technologies for assessment of retinal diseases

INTRODUCTION

Retinal imaging is a key investigation in ophthalmology. New devices continue to be created to keep up with the demand for better imaging modalities in this field. This review looks to highlight current trends and the future of retinal imaging.

AREAS COVERED

This review looks at the advances in topographical imaging, photoacoustic microscopy, optical coherence tomography and molecular imaging. There is future scoping on further advances in retinal imaging.

EXPERT OPINION

Retinal imaging continues to develop at a rapid pace to improve diagnosis and management of patients. We will see the development of big data to gain powerful insights and new technologies such as teleophthalmology mature in the future.

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.

Real-Time Imaging of Retinal Cell Apoptosis by Confocal Scanning Laser Ophthalmoscopy and Its Role in Glaucoma

Glaucoma is one of the leading causes of irreversible blindness in the world. It is characterized by the progressive loss of retinal ganglion cells (RGCs), mainly through the process of apoptosis. Glaucoma patients often come to clinical attention when irreversible loss of visual function has been already established; therefore, early recognition of RGC apoptosis is inordinately important in disease prevention. The novel technology called Detection of Apoptosing Retinal Cells (DARC) allows real-time in vivo quantification of apoptosing cells through the use of a fluorescent biomarker and a confocal scanning ophthalmoscope. A recent Phase I clinical trial has evaluated the safety of DARC and its ability to detect retinal apoptosis in glaucoma patients and healthy volunteers. Results suggest that DARC may have potential in the early detection of glaucoma, which could help alleviate the medical, social, and economic burden associated with this blinding condition.

Real-time imaging of single neuronal cell apoptosis in patients with glaucoma

See Herms and Schön (doi10.1093/brain/awx100) for a scientific commentary on this article.

Topical Coenzyme Q10 demonstrates mitochondrial-mediated neuroprotection in a rodent model of ocular hypertension

Coenzyme Q10 (CoQ10) is a mitochondrial-targeted antioxidant with known neuroprotective activity. Its ocular effects when co-solubilised with α-tocopherol polyethylene glycol succinate (TPGS) were evaluated. In vitro studies confirmed that CoQ10 was significantly protective in different retinal ganglion cell (RGC) models. In vivo studies in Adult Dark Agouti (DA) rats with unilateral surgically-induced ocular hypertension (OHT) treated with either CoQ10/TPGS micelles or TPGS vehicle twice daily for three weeks were performed, following which retinal cell health was assessed in vivo using DARC (Detection of Apoptotic Retinal Cells) and post-mortem with Brn3a histological assessment on whole retinal mounts. CoQ10/TPGS showed a significant neuroprotective effect compared to control with DARC (p<0.05) and Brn3 (p<0.01). Topical CoQ10 appears an effective therapy preventing RGC apoptosis and loss in glaucoma-related models.

Real-time imaging of retinal cell apoptosis by confocal scanning laser ophthalmoscopy

Retinal cell apoptosis occurs in many eye conditions, including glaucoma, diabetic retinopathy and Alzheimer's disease. Real-time detection of retinal cell apoptosis has potential clinical value in early disease detection, as well as evaluating disease progression and treatment efficacy. Here, we describe our novel imaging technology DARC (Detection of Apoptosing Retinal Cells), which can be used to visualize single retinal neurons undergoing apoptosis in real time, by using fluorescently labeled Annexin A5 and confocal scanning laser ophthalmoscopy (cSLO ). Clinical trials of DARC in glaucoma patients are due to start shortly, but in this chapter, we describe this technique in experimental animal models.

Topical delivery of Avastin to the posterior segment of the eye in vivo using annexin A5-associated liposomes

Effective delivery to the retina is presently one of the most challenging areas in drug development in ophthalmology, due to anatomical barriers preventing entry of therapeutic substances. Intraocular injection is presently the only route of administration for large protein therapeutics, including the anti-Vascular Endothelial Growth Factors Lucentis (ranibizumab) and Avastin (bevacizumab). Anti-VEGFs have revolutionised the management of age-related macular degeneration and have increasing indications for use as sight-saving therapies in diabetes and retinal vascular disease. Considerable resources have been allocated to develop non-invasive ocular drug delivery systems. It has been suggested that the anionic phospholipid binding protein annexin A5, may have a role in drug delivery. In the present study we demonstrate, using a combination of in vitro and in vivo assays, that the presence of annexin A5 can significantly enhance uptake and transcytosis of liposomal drug carrier systems across corneal epithelial barriers. This system is employed to deliver physiologically significant concentrations of Avastin to the posterior of the rat eye (127 ng/g) and rabbit retina (18 ng/g) after topical application. Our observations provide evidence to suggest annexin A5 mediated endocytosis can enhance the delivery of associated lipidic drug delivery vehicles across biological barriers, which may have therapeutic implications.

The cytoplasmic domain of neuropilin 1 is dispensable for angiogenesis, but promotes the spatial separation of retinal arteries and veins

Neuropilin 1 (NRP1) is a transmembrane glycoprotein that is essential for blood vessel development in vertebrates. Best known for its ability to bind members of the vascular endothelial growth factor (VEGF) and class 3 semaphorin families through its extracellular domain, it also has a highly conserved cytoplasmic domain, which terminates in a SEA motif that binds the PDZ protein synectin/GIPC1/NIP. Previous studies in zebrafish embryos and tissue culture models raised the possibility that the SEA motif of NRP1 is essential for angiogenesis. Here, we describe the generation of mice that express a form of NRP1 that lacks the cytoplasmic domain and, therefore, the SEA motif (Nrp1^cytoΔ/Δ mice). Our analysis of pre- and perinatal vascular development revealed that vasculogenesis and angiogenesis proceed normally in these mutants, demonstrating that the membrane-anchored extracellular domain is sufficient for vessel growth. By contrast, the NRP1 cytoplasmic domain is required for normal arteriovenous patterning, because arteries and veins crossed each other at an abnormally high frequency in the Nrp1^cytoΔ/Δ retina, as previously reported for mice with haploinsufficient expression of VEGF in neural progenitors. At crossing sites, the artery was positioned anteriorly to the vein, and both vessels were embedded in a shared collagen sleeve. In human eyes, similar arteriovenous crossings are risk factors for branch retinal vein occlusion (BRVO), an eye disease in which compression of the vein by the artery disrupts retinal blood flow, causing local tissue hypoxia and impairing vision. Nrp1^cytoΔ/Δ mice may therefore provide a suitable genetic model to study the aetiology of BRVO.

Localisation and significance of in vivo near-infrared autofluorescent signal in retinal imaging

AIM

To evaluate near-infrared (NIR) autofluorescence (AF) in patients with geographic atrophy (GA) secondary to age-related macular degeneration and to investigate the origin of the signal by in vivo and histological analysis in rats and in a human donor eye.

METHODS

Confocal scanning laser ophthalmoscopy in vivo imaging, including blue (excitation: 488 nm, emission 500-700 nm) and NIR (excitation: 790 nm, emission >810 nm) AF was performed in 21 eyes of 18 GA patients. Pigmented and albino rats underwent with the same device both in vivo and post-mortem imaging. For the latter, cryostat prepared retinal cross-sections were imaged using an additional customised magnification lens. Finally, cross-sections of a 49-year old human donor eye were recorded.

RESULTS

Atrophic areas in GA were characterised by low NIR AF intensities. In the junctional zone of atrophy, focal areas of increased intensity were seen which appeared to seldom correlate to blue AF findings. Confocal live scanning in pigmented rats identified the maximum of the NIR AF signal in the outer retina, with histological confirmation of the signal origin localised to the retinal pigment epithelium and sclera in both animals and human donor eye. No NIR AF was found in the retina of young non-pigmented rats.

DISCUSSION

This study further underscores the assumption that melanin is the main source of NIR AF in the healthy retina. Increased NIR AF intensities in the junctional zone in GA may represent accumulation of melanolipofuscin, which may reflect disease activity and thus may allow for early identification of patients at high-risk of GA enlargement.

Tracking longitudinal retinal changes in experimental ocular hypertension using the cSLO and spectral domain-OCT

PURPOSE

Involvement of the outer retina is controversial in glaucoma. The aim of this study was to test, first, whether the outer retina is affected in experimental ocular hypertension (OHT) and, second, whether whole retinal thickness can be used as a surrogate marker of glaucomatous change.

METHODS

OHT was surgically induced in 20 Dark Agouti rats. Animals were imaged using a modified Spectralis OCT (Heidelberg Engineering, Heidelberg, Germany) at baseline and at 3 and 8 weeks after OHT induction. Measurements were recorded for whole and individual retinal layer thickness in four regions-temporal, superior, nasal, and inferior-around the optic nerve head.

RESULTS

Whole retinal thickness in normal eyes was 172.19 ± 5.17 μm, with no significant regional differences. OHT caused a significant reduction in whole retinal thickness and the outer nuclear layer (ONL) at 3 and 8 weeks (P < 0.05), along with the expected thinning of the retinal nerve fiber layer (RNFL). Whole retinal thickness correlated well with RNFL (P = 0.035) and ONL (P ≤ 0.001) changes. Sensitivity of RNFL and ONL to IOP exposure appeared greater at 3 than at 8 weeks. In addition, regional profiles were significantly altered in the ONL and RNFL after OHT induction.

CONCLUSIONS

Adaptation of the Spectralis OCT enables tracking of structural damage in experimental rat OHT. Here the authors show evidence of glaucomatous damage in the outer retinal layers of this model with significant regional changes and highlight whole retinal thickness in the rat as a useful surrogate marker of inner and outer retinal changes. The authors believe that the OCT data can provide useful information with regard to clinical management.

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.