Continuous IOP Fluctuation Recording in Normal Tension Glaucoma Patients

A first-in-human pilot study of a novel electrically-passive metamaterial-inspired resonator-based ocular sensor embedded contact lens monitoring intraocular pressure fluctuations

Glaucoma is a leading cause of blindness with no cure, but early treatment and effective monitoring can often slow the progression of the disease. Monitoring of glaucoma is based on the measurement of intra-ocular pressure (IOP) that is a physiological parameter related to the mechanical state and parameters of the eye. Conventionally, diagnosing and assessing the progression of glaucoma is based on the method of measuring IOP discretely at clinics. Recent studies have demonstrated the importance of continuously monitoring IOP for 24 h to elucidate the effect of circadian rhythm. In this work, a metamaterial-inspired electrically-passive sensor-embedded contact lens is presented to monitor the IOP fluctuations based on a first-in-human pilot study. The sensor inside the contact lens is an electrically passive, metamaterial-based resonator that can be measured using a wearable antenna patch. The system has been tested with six healthy volunteers during an experiment to induce deliberate IOP changes via water-loading and placing the individuals in supine position using a recliner seat. The initial data compared with tonometer measurements suggest that the system can be used to assess the variation of IOP continuously.

Efficacy and safety of timolol-dorzolamide fixed-combination three times a day versus two times a day in newly diagnosed open-angle glaucoma

Objective

This study aimed to compare the therapeutic efficacy and safety of dorzolamide/timolol fixed-combination(Cosopt) in newly diagnosed primary open-angle glaucoma (POAG) patients.

Methods

In this prospective, interventional case series, newly POAG patients were included. Patients were started on Cosopt twice a day (BID) for one month and then switched to three times a day (TDS) for an additional month. Patients underwent comprehensive ophthalmic examination, diurnal intraocular pressure (IOP), blood pressure (BP), and 24-h heart rate (HR) measurements at baseline, month 1(BID), and month 2(TDS). Throughout the study, all adverse events were monitored by the investigators.

Results

In 31 POAG patients that completed the study, the mean baseline IOP was 23.1 ± 3.15 mmHg. IOP was decreased significantly 16.5 ± 2.21 at one month (p < .0001) and 13.9 ± 2.23 mmHg at 1 and 2 months follow up (p < .0001). IOP was significantly lower in month 2 compared to month 1 (p = .0004). While Cosopt BID significantly reduced the mean 24-h systolic BP and mean 24-h HR from baseline (p < .0001), the mean 24-h systolic BP and HR remained unchanged with Cosopt TDS compared to BID (p = .62).

Conclusions

Cosopt TDS has a superior IOP-lowering effect than Cosopt BID in POAG patients with comparable safety profiles.

How to Measure Intraocular Pressure: An Updated Review of Various Tonometers

Intraocular pressure (IOP) is an important measurement that needs to be taken during ophthalmic examinations, especially in ocular hypertension subjects, glaucoma patients and in patients with risk factors for developing glaucoma. The gold standard technique in measuring IOP is still Goldmann applanation tonometry (GAT); however, this procedure requires local anesthetics, can be difficult in patients with scarce compliance, surgical patients and children, and is influenced by several corneal parameters. Numerous tonometers have been proposed in the past to address the problems related to GAT. The authors review the various devices currently in use for the measurement of intraocular pressure (IOP), highlighting the main advantages and limits of the various tools. The continuous monitoring of IOP, which is still under evaluation, will be an important step for a more complete and reliable management of patients affected by glaucoma.

Triggerfish Recording of IOP Patterns in Combined HFDS Minimally Invasive Glaucoma and Cataract Surgery: A Prospective Study

BACKGROUND

The aim of the study is to investigate whether the circadian IOP rhythm can be influenced by combined cataract surgery with high frequency deep sclerotomy (HFDS) and whether intraocular pressure (IOP) can be significantly reduced by HFDS.

METHODS

In our study 10 patients were included, in whom 24 h IOP monitoring was installed before and after HFDS/cataract surgery using a Triggerfish. HFDS is a minimally invasive glaucoma surgery (MIGS).

RESULTS

After performed HFDS combined with cataract surgery, the IOP was reduced from 27.7 ± 2.11 mmHg to 14.4 ± 2.59 mmHg, which is highly significant (p < 0.001). The contact lens sensor (CLS) cosinor analysis pre- and postoperatively showed that the circadian rhythm is not influenced by the surgery, i.e., the circadian IOP rhythm did not show significant differences before and after surgery.

CONCLUSIONS

HFDS combined with cataract surgery is a potent surgical method that can significantly reduce the IOP. However, the circadian rhythm cannot be changed by the surgery. The acrophase remained during the night in all patients.

Central-to-peripheral corneal edema during wear of embedded-component contact lenses

PURPOSE

With active investigation underway for embedded-circuit contact lenses, safe oxygen supply of these novel lenses remains a question. Central-to-peripheral corneal edema for healthy eyes during wear of soft contact (SCL) and scleral lenses (SL) with embedding components is assessed.

METHODS

Various 2-dimensional (2D) designs of SL and SCL with embedded components are constructed on Comsol Multiphysics 5.5. Local corneal swelling associated with the designed lenses is determined by a recently developed 2D metabolic-swelling model. Settled central post-lens tear-film thicknesses (PoLTFs) are set at 400 μm and 3 μm for SL and SCL designs, respectively. Each lens design has an axisymmetric central and an axisymmetric peripheral embedment. Oxygen permeability (Dk) of the lens and the embedments ranges from 0 to 200 Barrer. Dimensions and location of the embedments are varied to assess optimal-design configurations to minimize central-to-peripheral corneal edema.

RESULTS

By adjusting oxygen Dk of the central embedment, the peripheral embedment, or the lens matrix polymer, corneal swelling is reduced by up to 2.5 %, 1.5 %, or 1.4 % of the baseline corneal thickness, respectively, while keeping all other parameters constant. A decrease in PoLTF thickness from 400 μm to 3 μm decreases corneal edema by up to 1.8 % of the baseline corneal thickness. Shifting the peripheral embedment farther out towards the periphery and towards the anterior lens surface reduces peak edema by up to 1.3 % and 0.6 % of the baseline corneal thickness, respectively.

CONCLUSIONS

To minimize central-to-peripheral corneal edema, embedments should be placed anteriorly and far into the periphery to allow maximal limbal metabolic support and oxygen transport in the polar direction (i.e., the θ-direction in spherical coordinates). High-oxygen transmissibility for all components and thinner PoLTF thickness are recommended to minimize corneal edema. Depending on design specifications, less than 1 % swelling over the entire cornea is achievable even with oxygen-impermeable embedments.

Intereye Symmetry of 24-Hour Intraocular Pressure-related Patterns in Untreated Glaucoma Patients Using a Contact Lens Sensor

PURPOSE

Scarce data are available on the symmetry of 24-hour intraocular pressure (IOP) variations between fellow eyes of glaucoma patients, and such evidence could have profound consequences on the interpretation of monocular therapeutic trials. The objective is to evaluate the intereye correlation of continuously measured circadian IOP-related patterns in untreated glaucoma patients.

METHODS

In this single-center prospective study, a total of 29 untreated patients with open-angle glaucoma underwent bilateral ambulatory 24-hour monitoring of IOP-related patterns using a contact lens sensor (CLS; SENSIMED Triggerfish). IOP was measured before and after CLS monitoring using Goldmann applanation tonometry. Intereye agreement of 24-hour patterns was calculated using Spearman correlation (r) of raw data and after cosinor rhythmometry modeling.

RESULTS

Complete bilateral CLS data could be obtained in 20 patients (mean age: 55.5±15.7 y; 51.7% women). On average, intereye correlation was r=0.76±0.19 (range: 0.16 to 0.95) and r=0.77±0.15 (range: 0.49 to 0.91), after excluding 8 patients with lower quality recordings. Cosine rhythmometry modeling showed mean acrophases occurring at 4:21±2:20 AM in left eyes and 3:39±1:50 AM in right eyes (r=0.48; P=0.034). Mean acrophase amplitude was 110.9±51.9 for left eyes and 107.8±46.2 for right eyes (r=0.79; P<0.001). No serious adverse events related to CLS monitoring were recorded. Transient conjunctival hyperemia (13 patients) and blurred vision (11 patients) were the most frequent adverse events.

CONCLUSIONS

In this group of untreated glaucoma patients, there was good intereye agreement for circadian IOP-related patterns using the CLS. These results show a higher degree of intereye symmetry, in terms of IOP peak timings and amplitudes, than previously reported with standard tonometry.

Quantitative analysis of retinal nerve fiber layer defect in early open-angle glaucoma with normal intraocular pressure

PURPOSE

To quantitatively analyze the topographic features of localized retinal nerve fiber layer (RNFL) defects according to baseline intraocular pressure (IOP) level in cases of early primary open-angle glaucoma (POAG).

STUDY DESIGN

Retrospective comparative study.

METHODS

POAG patients meeting the following conditions were consecutively included: (1) baseline office-hour diurnal IOP ≤ 21 mmHg, (2) 1 localized RNFL defect as observed on red-free fundus photography, and (3) corresponding visual field defect. Defects' approximations to the macula (angle α) and width (angle ß) as well as the angle between the disc long axis and the vertical meridian line (angle Ɣ) were measured on red-free fundus photography. The corrected angle α was calculated as the difference between angles α and Ɣ. The defect area's RNFL thickness was calculated by means of optical coherence tomography's Advanced Extraction analysis utility.

RESULTS

Comparative analysis was performed between 2 groups: 45 eyes of 45 patients with low-teen IOP (group A: highest IOP ≤ 15 mmHg) and 49 eyes of 49 patients with high-teen IOP (group B: lowest IOP > 15 mmHg). In group A, the mean baseline IOP was lower (12.9 ± 1.3 vs 17.1 ± 1.0 mmHg; P < .001), the corrected angle α was smaller (32.4 ± 15.1 vs 39.5 ± 13.1 degrees; P = .017), and the defect area's RNFL thickness was thinner (66.3 ± 16.8 vs 76.3 ± 14.9 μm; P = .003) than in group B; angle ß showed no intergroup difference (P = .230).

CONCLUSIONS

In POAG patients with low-teen IOP relative to those with high-teen IOP, localized RNFL defects were closer to the macula. In addition, the RNFL thickness of the defect area was markedly thinner.

Comparison of ExPress Implantation and Partial Deep Sclerectomy Combined with ExPress Implantation and Simultaneous Phacoemulsification

Background

To compare the effectiveness and safety profile of ExPress implantation versus partial deep sclerectomy combined with ExPress implantation and simultaneous phacoemulsification.

Patients and Methods

A prospective, randomized control study with 24-month follow-up was performed. 114 eyes were included, of which 42 eyes underwent phacoemulsification with simultaneous implantation of the Ex-Press device (ExPress), and deep sclerectomy with phacoemulsification and simultaneous implantation of the Ex-Press device (DS-ExPress) was performed in 72 eyes. The main outcome measures were intraocular pressure (IOP), corrected distance visual acuity (CDVA), the number of antiglaucoma medications, and the rate of complications. Surgical success was defined as complete (without antiglaucoma medications) with IOP ≤18 mmHg in criterion A, IOP ≤16 mmHg in criterion B, and IOP ≤12 mmHg in criterion C. Satisfactory success was defined as the same IOP levels for individual criteria with a maximum of 2 antiglaucoma medications.

Results

Before the procedure, mean IOP in the ExPress group was 17.5 ± 4.7 mmHg; after 24 months, it decreased by 13% to 16.0 ± 3.0 mmHg (P < 0.05). In the DS-ExPress group, mean IOP reduced from 16.3 ± 4.4 mmHg to 14.3 ± 3.3 mmHg (P < 0.05), which was a 9% reduction compared to the initial value. In the DS-ExPress group, 65.9% of the patients did not use topical pharmacotherapy, and the same is true for 29.2% of the ExPress group (P=0.004).

Conclusions

This modification is efficient in surgical treatment of glaucoma, especially when very low postoperative IOP is needed. A less amount of antiglaucoma medicines are needed.

Role of 24-Hour Intraocular Pressure Monitoring in Glaucoma Management

Glaucoma is the leading cause of irreversible blindness worldwide and the prevalence is on the rising trend. Intraocular pressure (IOP) reduction is the mainstay of treatment. The current practice of IOP monitoring is based on spot measurements during clinic visits during office hours. However, there are up to 50% of glaucoma patients who had normal initial IOP, while some treated patients continued to have progressive glaucomatous optic nerve damage even with a low IOP. Recent studies have shown that the IOP of glaucoma patients fluctuated during the day with different patterns, and some of them had peak IOP outside office hours. These findings provided us with new insights on the role of 24-hour IOP monitoring in managing normal tension glaucoma and patients with progressive deterioration despite apparently well-controlled IOP. Nevertheless, results to date are rather inconsistent, and there is no consensus yet. In this review, we briefly highlighted the current modalities of 24-hour IOP monitoring and summarized the characteristic 24-hour IOP pattern and the clinical relevance of IOP parameters in predicting glaucomatous progression in different glaucoma subtypes. We also discussed the therapeutic efficacy of current glaucoma treatment modalities with respect to the mentioned 24-hour IOP profiles, so as to strengthen the role of 24-hour IOP monitoring in identifying and stratifying the risks of progression in glaucoma patients, as well as optimizing treatments according to their IOP profiles.

Current trends in Nanotechnology applications in surgical specialties and orthopedic surgery

Nanotechnology is manipulation of matter on atomic, molecular and supramolecular scale. It has extensive range of applications in various branches of science including molecular biology, Health and medicine, materials, electronics, transportation, drugs and drug delivery, chemical sensing, space exploration, energy, environment, sensors, diagnostics, microfabrication, organic chemistry and biomaterials. Nanotechnology involves innovations in drug delivery,fabric design, reactivity and strength of material and molecular manufacturing. Nanotechnology applications are spread over almost all surgical specialties and have revolutionized treatment of various medical and surgical conditions. Clinically relevant applications of nanotechnology in surgical specialties include development of surgical instruments, suture materials, imaging, targeted drug therapy, visualization methods and wound healing techniques. Management of burn wounds and scar is an important application of nanotechnology.Prevention, diagnosis, and treatment of various orthopedic conditions are crucial aspects of technology for functional recovery of patients. Improvement in standard of patient care,clinical trials, research, and development of medical equipments for safe use are improved with nanotechnology. They have a potential for long-term good results in a variety of surgical specialties including orthopedic surgery in the years to come.

Twenty-Four-Hour Contact Lens Sensor Monitoring of Aqueous Humor Dynamics in Surgically or Medically Treated Glaucoma Patients

Aim

This study assessed the 24 h circadian rhythm of intraocular pressure (IOP) using a contact lens sensor in three groups of patients with open-angle glaucoma.

Methods

This study was a monocentric, cross-sectional, nonrandomized, prospective, pilot study. Eighty-nine patients were enrolled: 29 patients previously underwent an Ex-PRESS mini glaucoma device procedure (Group 1), 28 patients previously underwent Hydrus microstent implantation (Group 2), and 32 patients were currently being treated medically for primary open-angle glaucoma (Group 3). Circadian rhythm patterns were considered with five circadian indicators: fluctuation ranges, maximum, minimum, acrophase (time of peak value), and bathyphase (time of trough value). A two-tailed Mann–Whitney U-test was used to evaluate differences between groups.

Results

All subjects exhibited a circadian rhythm and a nocturnal pattern. The signal fluctuation range was significantly smaller in the surgical groups than in the medically treated group (Group 1 vs. Group 3, p=0.003; Group 2 vs. Group 3, p=0.010). Subjects who underwent the Ex-PRESS procedure (Group 1) exhibited significant differences compared with the drug therapy group (Group 3) with regard to the minimum value (p=0.015), acrophase (p=0.009), and bathyphase (p=0.002). The other circadian indicators were not significantly different among groups.

Conclusions

Patients who underwent IOP-lowering surgery had an intrinsic nyctohemeral rhythm. Both surgical procedures, Ex-PRESS and Hydrus, were associated with smaller signal fluctuations compared with medical treatment.

Diurnal and 24-h Intraocular Pressures in Glaucoma: Monitoring Strategies and Impact on Prognosis and Treatment

The present review casts a critical eye on intraocular pressure (IOP) monitoring and its value in current and future glaucoma care. Crucially, IOP is not fixed, but varies considerably during the 24-h cycle and between one visit and another. Consequently, a single IOP measurement during so-called office hours is insufficient to characterize the real IOP pathology of a patient with glaucoma. To date IOP remains the principal and only modifiable risk factor for the development and progression of glaucoma. Only by evaluating IOP characteristics (mean, peak and fluctuation of IOP) at diagnosis and after IOP-lowering interventions can we appreciate the true efficacy of therapy. Unfortunately, a major limiting factor in glaucoma management is lack of robust IOP data collection. Treatment decisions, advancement of therapy and even surgery are often reached on the basis of limited IOP evidence. Clearly, there is much room to enhance our decision-making and to develop new algorithms for everyday practice. The precise way in which daytime IOP readings can be used as predictors of night-time or 24-h IOP characteristics remains to be determined. In practice it is important to identify those at-risk glaucoma patients for whom a complete 24-h curve is necessary and to distinguish them from those for whom a daytime curve consisting of three IOP measurements (at 10:00, 14:00 and 18:00) would suffice. By employing a staged approach in determining the amount of IOP evidence needed and the rigour required for our monitoring approach for the individual patient, our decisions will be based on more comprehensive data, while at the same time this will optimize use of resources. The patient’s clinical picture should be the main factor that determines which method of IOP monitoring is most appropriate. A diurnal or ideally a 24-h IOP curve will positively impact the management of glaucoma patients who show functional/anatomical progression, despite an apparently acceptable IOP in the clinic. The potential impact of nocturnal IOP elevation remains poorly investigated. The ideal solution in the future is the development of non-invasive methods for obtaining continuous, Goldmann equivalent IOP data on all patients prior to key treatment decisions. Moreover, an important area of future research is to establish the precise relationship between 24-h IOP characteristics and glaucoma progression.

Innovative Development of Contact Lenses

Contact lenses have been a common means of vision correction for more than half a century. Recent developments have raised the possibility that the next few decades will see a considerable broadening of the range of applications for contact lenses, with associated expansions in the number and type of individuals who consider them a valuable option. The novel applications of contact lenses include treatment platforms for myopic progression, biosensors, and ocular drug delivery. Orthokeratology has shown the most consistent treatment for myopia control with the least side effects. Recent work has resulted in commercialization of a device to monitor intraocular pressure for up to 24 hours, and extensive efforts are underway to develop a contact lens sensor capable of continuous glucose tear film monitoring for the management of diabetes. Other studies on drug-eluting contact lenses have focused on increasing the release duration through molecular imprinting, use of vitamin E, and increased drug binding to polymers by sandwiching a poly (lactic-co-glycolic acid) layer in the lens. This review demonstrates the potential for contact lenses to provide novel opportunities for refractive management, diagnosis, and management of diseases.

Circadian rhythms, refractive development, and myopia

PURPOSE

Despite extensive research, mechanisms regulating postnatal eye growth and those responsible for ametropias are poorly understood. With the marked recent increases in myopia prevalence, robust and biologically-based clinical therapies to normalize refractive development in childhood are needed. Here, we review classic and contemporary literature about how circadian biology might provide clues to develop a framework to improve the understanding of myopia etiology, and possibly lead to rational approaches to ameliorate refractive errors developing in children.

RECENT FINDINGS

Increasing evidence implicates diurnal and circadian rhythms in eye growth and refractive error development. In both humans and animals, ocular length and other anatomical and physiological features of the eye undergo diurnal oscillations. Systemically, such rhythms are primarily generated by the 'master clock' in the surpachiasmatic nucleus, which receives input from the intrinsically photosensitive retinal ganglion cells (ipRGCs) through the activation of the photopigment melanopsin. The retina also has an endogenous circadian clock. In laboratory animals developing experimental myopia, oscillations of ocular parameters are perturbed. Retinal signaling is now believed to influence refractive development; dopamine, an important neurotransmitter found in the retina, not only entrains intrinsic retinal rhythms to the light:dark cycle, but it also modulates refractive development. Circadian clocks comprise a transcription/translation feedback control mechanism utilizing so-called clock genes that have now been associated with experimental ametropias. Contemporary clinical research is also reviving ideas first proposed in the nineteenth century that light exposures might impact refraction in children. As a result, properties of ambient lighting are being investigated in refractive development. In other areas of medical science, circadian dysregulation is now thought to impact many non-ocular disorders, likely because the patterns of modern artificial lighting exert adverse physiological effects on circadian pacemakers. How, or if, such modern light exposures and circadian dysregulation contribute to refractive development is not known.

SUMMARY

The premise of this review is that circadian biology could be a productive area worthy of increased investigation, which might lead to the improved understanding of refractive development and improved therapeutic interventions.

Intraocular Pressure Fluctuations and 24-Hour Continuous Monitoring for Glaucoma Risk in Wind Instrument Players

PURPOSE

The purpose of this study is to investigate the influence of playing a wind instrument on intraocular pressure (IOP) and to monitor 24-hour (IOP) fluctuations in wind musicians of symphony and wind orchestras to compare IOP levels during normal daily activities with IOP levels during playing.

METHODS

Professional and amateur musicians of symphony and wind orchestras were invited to participate. A total of 42 participants, 9 with glaucoma, underwent a routine ophthalmologic examination. IOP measurements were taken before and immediately after 20 minutes of playing wind instruments. In addition, 6 participants underwent 24-hour IOP monitoring with the Triggerfish (Sensimed AG, Switzerland) sensing contact lens, during which they kept an activity logbook.

RESULTS

Eleven professionals and 31 amateur musicians participated in the study. A total of 7 eyes of 6 patients underwent additional 24-hour IOP monitoring. Mean IOP before playing was 13.6±2.6 mm Hg, IOP change after playing was +1.5±2.2 mm Hg with a significant difference between professionals (2.5±1.5 mm Hg) and amateurs (1.1±2.3 mm Hg). There were no significant differences in IOP change between subjects with or without glaucoma. During 24-hour IOP monitoring there were slight increases in IOP while playing an instrument, but also during other activities and overnight. These latter IOP levels were similar or even higher than the IOP rise caused by playing a wind instrument.

CONCLUSIONS

IOP often rises after playing wind instruments, but similar or even higher IOP levels seem to occur during common other daily activities or at night. These peaks may be relevant for glaucomatous field progression and treatment of glaucoma patients.

24-Hour Intraocular Pressure Rhythm in Patients With Untreated Primary Open Angle Glaucoma and Effects of Selective Laser Trabeculoplasty

PURPOSE OF THE STUDY

The purpose of the study was to evaluate the 24-hour nyctohemeral rhythm of intraocular pressure (IOP) in patients with untreated primary open angle glaucoma using a contact lens sensor. To evaluate the effect of selective laser trabeculoplasty (SLT) on the 24-hour rhythm of IOP.

MATERIALS AND METHODS

Prospective study conducted in a chronobiology center. Fourteen patients with primary open angle glaucoma underwent three 24-hour IOP measurement sessions after a complete wash-out of the medical treatment: before SLT and 1 and 6 months after, using the contact lens sensor Triggerfish (SENSIMED, Lausanne, Switzerland). IOP and the main parameters of nyctohemeral rhythm (existence of a rhythm, acrophase, bathyphase, midline estimating statistic of rhythm, amplitude, and range) before SLT were compared with the same parameters measured 1 and 6 months later.

RESULTS

IOP increased from 16.3±3.7 to 22.1±8.4 mm Hg (5.8 mm Hg; 95% confidence interval (CI), 2.41-12.71; P=0.009) after the wash-out procedure. After SLT, IOP significantly decreased by 3.4 mm Hg (95% CI, 0.09-7.89; P=0.041) (14.9%) at 1 month and 1.9 mm Hg (95% CI 0.10-3.84; P=0.044) (8.1%) at 6 months. After medication wash-out, 100% of the subjects had a nyctohemeral IOP rhythm with nocturnal acrophase (01:57±3:32 AM, 01:22±3:01 AM, and 03:17±2:12 AM at inclusion, 1 and 6 mo, respectively). SLT did not significantly change the characteristics of the 24-hour IOP pattern, notably the amplitude and the type of rhythm (persistence of nocturnal acrophase).

CONCLUSIONS

After medical treatment wash-out, patients with open angle glaucoma consistently had a significant 24-hour IOP rhythm with nocturnal acrophase. SLT reduces the absolute IOP value but does not modify the nyctohemeral IOP rhythm.

Glaucoma: Biological Trabecular and Neuroretinal Pathology with Perspectives of Therapy Innovation and Preventive Diagnosis

Glaucoma is a common degenerative disease affecting retinal ganglion cells (RGC) and optic nerve axons, with progressive and chronic course. It is one of the most important reasons of social blindness in industrialized countries. Glaucoma can lead to the development of irreversible visual field loss, if not treated. Diagnosis may be difficult due to lack of symptoms in early stages of disease. In many cases, when patients arrive at clinical evaluation, a severe neuronal damage may have already occurred. In recent years, newer perspective in glaucoma treatment have emerged. The current research is focusing on finding newer drugs and associations or better delivery systems in order to improve the pharmacological treatment and patient compliance. Moreover, the application of various stem cell types with restorative and neuroprotective intent may be found appealing (intravitreal autologous cellular therapy). Advances are made also in terms of parasurgical treatment, characterized by various laser types and techniques. Moreover, recent research has led to the development of central and peripheral retinal rehabilitation (featuring residing cells reactivation and replacement of defective elements), as well as innovations in diagnosis through more specific and refined methods and inexpensive tests.

The Sensimed Triggerfish contact lens sensor: efficacy, safety, and patient perspectives

Intraocular pressure, a major modifiable risk factor for glaucoma, has been shown to fluctuate throughout the day in patients with glaucoma. The detection and measurement of this fluctuation may help guide the clinical management of glaucomatous individuals. The Sensimed Triggerfish contact lens sensor (CLS), which has recently gained approval for marketing in the USA, is designed to detect intraocular pressure-related changes in an eye over a 24-hour period. This review will provide an overview of the Triggerfish CLS, as well as summarize current clinical data pertaining to the device. Overall, the current evidence suggests that the Triggerfish CLS is safe and well tolerated, and provides reproducible results. One challenge of using the Triggerfish CLS is that it may only provide data on relative changes in intraocular pressure rather than absolute intraocular pressure. In addition, its validity at estimating intraocular pressure compared to other methods is still controversial. Despite these limitations, recent studies suggest a myriad of potential indications for the Triggerfish CLS, including predicting glaucomatous progression and predicting efficacy of glaucoma treatment. With further research, the Triggerfish CLS may become a useful tool for eye care practitioners.

24-h monitoring devices and nyctohemeral rhythms of intraocular pressure

Intraocular pressure (IOP) is not a fixed value and varies over both the short term and periods lasting several months or years. In particular, IOP is known to vary throughout the 24-h period of a day, defined as a nyctohemeral rhythm in humans. In clinical practice, it is crucial to evaluate the changes in IOP over 24 h in several situations, including the diagnosis of ocular hypertension and glaucoma (IOP is often higher at night) and to optimize the therapeutic management of glaucoma. Until recently, all evaluations of 24-h IOP rhythm were performed using repeated IOP measurements, requiring individuals to be awakened for nocturnal measurements. This method may be imperfect, because it is not physiologic and disturbs the sleep architecture, and also because it provides a limited number of time point measurements not sufficient to finely asses IOP changes. These limitations may have biased previous descriptions of physiological IOP rhythm. Recently, extraocular and intraocular devices integrating a pressure sensor for continuous IOP monitoring have been developed and are available for use in humans. The objective of this article is to present the contributions of these new 24-h monitoring devices for the study of the nyctohemeral rhythms. In healthy subjects and untreated glaucoma subjects, a nyctohemeral rhythm is consistently found and frequently characterized by a mean diurnal IOP lower than the mean nocturnal IOP, with a diurnal bathyphase - usually in the middle or at the end of the afternoon - and a nocturnal acrophase, usually in the middle or at the end of the night.

The Use of Contact Lenses as Biosensors

: The tear film is a complex multilayer film consisting of various proteins, enzymes, and lipids and can express a number of biomarkers in cases of disease. The development of a contact lens sensor presents a noninvasive alternative for the detection and management of various diseases. Recent work has resulted in the commercialization of a device to monitor intraocular pressure for up to 24 h, and there are extensive efforts underway to develop a contact lens sensor capable of continuous glucose tear film monitoring to manage diabetes. This clinical perspective will highlight the major developments within this field and list some of the major challenges that still need to be addressed.

The Application of a Contact Lens Sensor in Detecting 24-Hour Intraocular Pressure-Related Patterns

Glaucoma is one of the leading causes of blindness worldwide. Recent studies suggest that intraocular pressure (IOP) fluctuations, peaks, and rhythm are important factors in disease advancement. Yet, current glaucoma management remains hinged on single IOP measurements during clinic hours. To overcome this limitation, 24-hour IOP monitoring devices have been employed and include self-tonometry, permanent IOP, and temporary IOP monitoring. This review discusses each IOP measuring strategy and focuses on the recently FDA-approved contact lens sensor (CLS). The CLS records IOP-related ocular patterns for 24 hours continuously. Using the CLS, IOP-related parameters have been found to be associated with the rate of visual field progression in primary open-angle glaucoma, disease progression in primary angle-closure glaucoma, and various clinical variables in ocular hypertension. The CLS has been used to quantify blink rate and limbal strain and measure the circadian rhythm in a variety of disease states including normal-tension glaucoma and thyroid eye disease. The effects of various IOP-lowering interventions were also characterized using the CLS. CLS provides a unique, safe, and well-tolerated way to study IOP-related patterns in a wide range of disease states. IOP-related patterns may help identify patients most at risk for disease progression and assist with the development of tailored treatments.

Challenges in the management of glaucoma in developing countries

Glaucoma is the most common optic neuropathy characterized by normal to raised intraocular pressure (IOP), visual field defects, loss of retinal nerve fiber layer, thinning of the neuroretinal rim, and cupping of the optic disc. IOP reduction by medical, laser, or surgical therapies remains the only clinically proven treatment of glaucoma. The challenges in glaucoma management are diverse. They include early detection and diagnosis, setting of appropriate target IOP, choice of treatment, monitoring of quality of life and sight, and compliance with the treatment. Early diagnosis can be made by assessing optic nerve structure using imaging devices and optic nerve function through perimetry. Reducing IOP and controlling its fluctuations are considered to be the most important factors in limiting progression of glaucoma. Selection of the best suitable therapy out of medical, surgical, or laser treatment options is yet another management challenge. Patients suffering from glaucoma experience poor quality of life owing to the diagnosis itself, functional visual loss, inconvenience and cost of treatment, and side effects of treatment. All these factors lead to poor compliance, adherence, and persistence to treatment, and further progression of the disease. It is, therefore, important that ophthalmologists keep all the aforementioned factors in mind when managing patients with glaucoma.

Effect of glaucoma medications on 24-hour intraocular pressure-related patterns using a contact lens sensor

BACKGROUND

The aim of this article was to study the circadian intraocular pressure (IOP)-related effects of ocular hypotensive medications using a contact lens sensor (CLS).

DESIGN

This is a university-based prospective, randomized, crossover trial.

PARTICIPANTS

A total of 23 patients with primary open-angle glaucoma participated.

METHODS

Patients underwent ambulatory recording of IOP-related patterns for 24 h in one eye during 3 monthly sessions using a CLS. Patients were untreated in session 1 (S1), were randomized to one of four classes of glaucoma drops for S2 and had a prostaglandin analogue add-on for S3.

MAIN OUTCOME MEASURES

Changes in IOP-related patterns were defined using (i) slopes from wake/sitting to sleep/supine; (ii) cosinor rhythmometry modelling; and (iii) area under receiver operating curve (AUC) of sleep period.

RESULTS

Mean patient age was 63.8 ± 11.8 years. Positive linear slopes were seen from wake/sitting to sleep/supine at S1 (17.1 ± 14.2 mVeq/h) and S2 (5.5 ± 23.9 mVeq/h) and negative slopes at S3 (-1.9 ± 29.4 mVeq/h) (S1-S2, P = 0.01; S1-S3, P = 0.02). In the prostaglandin group, slopes changed significantly with introduction of drops (S1-S2, P < 0.024), whereas they did not in a mixed group combining the three other classes (S1-S2, P = 0.060). Overall, cosinor amplitudes were 98.4 ± 46.5 mVeq (S1), 113.0 ± 35.6 mVeq (S2) and 109.6 ± 58.3 mVeq (S3) (S1-S2, P = 0.23; S1-S3, P = 0.66; S2-S3, P = 0.93). AUC were 91.8 ± 63.0 mVeq (S1), 76.3 ± 102.7 mVeq (S2) and 19.9 ± 135.8 mVeq (S3). Differences between sessions were not statistically significant (S1-S2, P = 0.541; S1-S3, P = 0.083; S2-S3, P = 0.092).

CONCLUSIONS

Prostaglandin analogues, but not other medications, seem to flatten the IOP-related increase at transition of the wake/sitting to the sleep/supine period, but do not seem to have an effect on acrophase and amplitude.

Noninvasive intraocular pressure monitoring: current insights

Glaucoma is the second leading cause of blindness worldwide and intraocular pressure (IOP) is currently its only modifiable risk factor. Peak IOP has for a long time been considered as a major contributor to glaucoma progression, but its effects may depend not only on its magnitude, but also on its time course. The IOP is nowadays considered to be a dynamic parameter with a circadian rhythm and spontaneous changes. The current practice of punctual measuring the IOP during office hours is therefore a suboptimal approach, which does not take into account the natural fluctuation of IOP. Because of its static nature a single IOP measurement in sitting position fails to document the true range of an individual's IOP, peak IOP, or variation throughout the day. Phasing means monitoring a patient's IOP during the daytime or over a 24-hour period. This can provide additional information in the management of glaucoma patients. This review focuses on the current insight of non-invasive IOP monitoring as a method of obtaining more complete IOP profiles. Invasive techniques using an implantable sensor are beyond the scope of this review.

Estimation of 24-Hour Intraocular Pressure Peak Timing and Variation Using a Contact Lens Sensor

PURPOSE

To compare estimates of 24-hour intraocular pressure (IOP) peak timing and variation obtained using a contact lens sensor (CLS) and using a pneumatonometer.

METHODS

Laboratory data collected from 30 healthy volunteers (ages, 20-66 years) in a randomized, controlled clinical trial were analyzed. Participants were housed for 24 hours in a sleep laboratory. One randomly selected right or left eye was fitted with a CLS that monitored circumferential curvature in the corneoscleral region related to the change of IOP. Electronic output signals of 30 seconds were averaged and recorded every 5 minutes. In the contralateral eye, habitual IOP measurements were taken using a pneumatonometer once every two hours. Simulated 24-hour rhythms in both eyes were determined by cosinor fitting. Simulated peak timings (acrophases) and simulated data variations (amplitudes) were compared between the paired eyes.

RESULTS

Bilateral change patterns of average 24-hour data for the group were in parallel. The simulated peak timing in the CLS fitted eye occurred at 4:44 AM ± 210 min (mean ± SD) and the IOP peak timing in the contralateral eye at 4:11 AM ± 120 min (P=0.256, Wilcoxon signed-rank test). There was no significant correlation between the simulated data variations in the paired eyes (P=0.820, linear regression).

CONCLUSIONS

The 24-hour CLS data showed a simulated peak timing close to the 24-hour IOP peak timing obtained using the pneumatonometer. However, the simulated variations of 24-hour data in the paired eyes were not correlated. Estimated 24-hour IOP rhythms using the two devices should not be considered interchangeable.

Association between glaucoma and obstructive sleep apnea syndrome: a meta-analysis and systematic review

Background

Obstructive sleep apnea syndrome (OSAS) is a common disease that increases the risk of diabetes, heart disease, and stroke. However, studies of an association between OSAS and glaucoma neuropathy have reported controversial findings.

Objective

The main purpose of this study was to evaluate whether a significant association exists between OSAS and glaucoma by performing a meta-analysis of previous studies.

Methods

A comprehensive literature search using the PubMed and Embase databases was performed to identify cross-sectional, case-control, and cohort studies related to the topic. We estimated a pooled odds ratio (OR) for the association between OSAS and glaucoma, by a fixed- or random-effects model.

Results

In total, 16 studies with 2,278,832 participants met the inclusion criteria: one retrospective cohort study reported an adjusted hazard ratio of glaucoma of 1.67 (95% CI = 1.30–2.17). Using a fixed-effects model, the pooled OR of six case-control studies was 1.96 (95% CI = 1.37 2.80). A significant association was also identified in a meta-analysis of nine cross-sectional studies using a random-effects model, which showed a pooled OR of 1.41 (95% CI = 1.11 1.79). However, the reported pooled estimates for case control studies and cross-sectional studies were based on unadjusted ORs.

Conclusions

Our results suggest that OSAS is associated with the prevalence of glaucoma. However, this result was based only on unadjusted estimates. Prospective cohort studies designed to take into consideration potential confounders, or examination of data from interventional trials to determine whether a reduction in OSAS status is associated with a reduced incidence of glaucoma, are needed to clarify whether OSAS is an independent risk factor for glaucoma.

Circadian intraocular pressure patterns in healthy subjects, primary open angle and normal tension glaucoma patients with a contact lens sensor

PURPOSE

To examine the circadian intraocular pressure (IOP) patterns in healthy subjects, in primary open angle and normal tension glaucoma (POAG; NTG) using a contact lens sensor (CLS; Sensimed Triggerfish, Lausanne, Switzerland).

METHODS

This was an observational, nonrandomized study. Ten healthy subjects (Group 1, 10 eyes) and 20 glaucomatous patients [20 eyes, 10 with POAG (Group 2) and 10 with NTG (Group 3)] were enrolled. All patients were controlled with prostaglandin analogues. The 24-hr IOP pattern was the main outcome. The morning (6AM-11AM), afternoon/evening (noon-11PM) and night (midnight-5AM) subperiod patterns, peaks and prolonged peaks (>1 hr) were secondary outcomes.

RESULTS

Mean 24-hr IOP pattern showed a nocturnal acrophase in all groups. Patterns were significantly different among groups (p = 0.02), with highest nocturnal IOP values in POAG. Prolonged peaks were more common in patients with glaucoma (70%) than in healthy subjects (33.3%) (p < 0.001). Significant differences were found for Groups 2 and 3 in the morning versus afternoon/evening (p = 0.019 and p = 0.035, Bonferroni correction), morning versus night (p = 0.005 and p < 0.0001) and afternoon/evening versus night periods comparisons (p < 0.0001 for both groups). In Group 1, patterns significantly differed in the morning versus night and afternoon/evening versus night period comparisons (p < 0.0001).

CONCLUSIONS

Continuous 24-hr IOP monitoring with the CLS revealed a nocturnal acrophase in healthy subjects and, more markedly, in glaucoma. Because the diurnal IOP profile seems not to predict the nocturnal rhythm, the circadian IOP pattern should be evaluated in clinical practice. These findings may be worthwhile for the management of glaucoma.

Continuous 24-hour ocular dimensional profile recording in medically treated normal-tension glaucoma

PURPOSE

To analyze the 24-hour ocular dimensional profile in normal-tension glaucoma (NTG) patients on medical treatment.

METHODS

Consecutive, medically treated NTG subjects were recruited from a university eye center. Subjects were on a mean of 1.7±0.7 types of antiglaucoma medications and 56.6% were on a prostaglandin analog. A contact lens-based sensor device was worn in one eye of NTG patients to record the intraocular pressure (IOP)-related profile for 24 hours, recording the following: variability from mean over 24 hours, nocturnally and diurnally, as well as the number of peaks and troughs diurnally and nocturnally.

RESULTS

In 18 NTG subjects, the nocturnal variability around the mean contact lens-based sensor device signal was 48.9% less than the diurnal variability around the mean. The number of peaks was 54.7% less during the nocturnal period than during the diurnal period. The rate of increase in the ocular dimensional profile when going to sleep was significantly greater than the rate of decrease upon waking (P<0.001).

CONCLUSION

In medically treated NTG subjects, there was more variability in the IOP-related pattern during the daytime and there were fewer peaks during sleep.

Intraocular pressure fluctuation and glaucoma progression: what do we know?

While mean intraocular pressure (IOP) has long been known to correlate with glaucomatous damage, the role of IOP fluctuation is less clearly defined. There is extensive evidence in the literature for and against the value of short-term and long-term IOP fluctuation in the evaluation and prognosis of patients with glaucoma. We present here the arguments made by both sides, as well as a discussion of the pitfalls of prior research and potential directions for future studies. Until a reliable method is developed that allows for constant IOP monitoring, many variables will continue to hinder us from drawing adequate conclusions regarding the significance of IOP variation.

Effect of overnight wear of the Triggerfish(®) sensor on corneal thickness measured by Visante(®) anterior segment optical coherence tomography

PURPOSE

To evaluate the effect of overnight wear of the Triggerfish(®) contact lens sensor (CLS) on central corneal thickness (CCT) using the Visante(®) anterior segment optical coherence tomography (AS-OCT).

METHODS

Twelve healthy subjects were studied in a sleep laboratory. An ophthalmic examination including ultrasonic CCT, corneal topography, specular microscopy and AS-OCT CCT was performed. Starting at 7 pm, the Triggerfish(®) CLS was fitted on one randomly selected eye. Similar AS-OCT measurements were taken on both eyes every 2 hr from 8 pm to 8 am. The CLS was removed just after the 8 am measurement session. Measurements were repeated at 9 am.

RESULTS

Twenty-four eyes of 12 subjects were studied (mean age, 22.1 ± 2.4 years; four men/eight women). CCT significantly increased during the night in both CLS and control eyes (p < 0.01). The maximal change was +4.4 ± 1.7% in the CLS eyes and +2.9 ± 1.8% in the control eyes (p < 0.05). Throughout the night, CCT significantly increased more in eyes with CLS than in control eyes (p < 0.05). There were significantly more corneal curvature irregularities after overnight wear of the CLS than in the control eye: +1.63 Dioptre (D) versus -0.02 D in the 3-mm central zone and +3.17 D versus +0.01 D in the 5-mm central zone (p < 0.01).

CONCLUSION

CCT and corneal curvature irregularities increased slightly but significantly more in eyes with the Triggerfish(®) CLS than in control eyes during overnight wear. Further studies are required to determine whether the corneal curvature changes modify the signal recorded by the sensor.

Reliable intraocular pressure measurement using automated radio-wave telemetry

PURPOSE

To present an autonomous intraocular pressure (IOP) measurement technique using a wireless implantable transducer (WIT) and a motion sensor.

METHODS

The WIT optical aid was implanted within the ciliary sulcus of a normotensive rabbit eye after extracapsular clear lens extraction. An autonomous wireless data system (AWDS) comprising of a WIT and an external antenna aided by a motion sensor provided continuous IOP readings. The sensitivity of the technique was determined by the ability to detect IOP changes resulting from the administration of latanoprost 0.005% or dorzolamide 2%, while the reliability was determined by the agreement between baseline and vehicle (saline) IOP.

RESULTS

On average, 12 diurnal and 205 nocturnal IOP measurements were performed with latanoprost, and 26 diurnal and 205 nocturnal measurements with dorzolamide. No difference was found between mean baseline IOP (13.08±2.2 mmHg) and mean vehicle IOP (13.27±2.1 mmHg) (P=0.45), suggesting good measurement reliability. Both antiglaucoma medications caused significant IOP reduction compared to baseline; latanoprost reduced mean IOP by 10% (1.3±3.54 mmHg; P<0.001), and dorzolamide by 5% (0.62±2.22 mmHg; P<0.001). Use of latanoprost resulted in an overall twofold higher IOP reduction compared to dorzolamide (P<0.001). Repeatability was ±1.8 mmHg, assessed by the variability of consecutive IOP measurements performed in a short period of time (≤1 minute), during which the IOP is not expected to change.

CONCLUSION

IOP measurements in conscious rabbits obtained without the need for human interactions using the AWDS are feasible and provide reproducible results.

A novel implantable glaucoma valve using ferrofluid

Purpose

To present a novel design of an implantable glaucoma valve based on ferrofluidic nanoparticles and to compare it with a well-established FDA approved valve.

Setting

Massachusetts Eye & Ear Infirmary, Boston, USA.

Methods

A glaucoma valve was designed using soft lithography techniques utilizing a water-immiscible magnetic fluid (ferrofluid) as a pressure-sensitive barrier to aqueous flow. Two rare earth micro magnets were used to calibrate the opening and closing pressure. In-vitro flow measurements were performed to characterize the valve and to compare it to Ahmed™ glaucoma valve. The reliability and predictability of the new valve was verified by pressure/flow measurements over a period of three months and X-ray diffraction (XRD) analysis over a period of eight weeks. In vivo assessment was performed in three rabbits.

Results

In the in vitro experiments, the opening and closing pressures of the valve were 10 and 7 mmHg, respectively. The measured flow/pressure response was linearly proportional and reproducible over a period of three months (1.8 µl/min at 12 mmHg; 4.3 µl/min at 16 mmHg; 7.6 µl/min at 21 mmHg). X-ray diffraction analysis did not show oxidization of the ferrofluid when exposed to water or air. Preliminary in vivo results suggest that the valve is biocompatible and can control the intraocular pressure in rabbits.

Conclusions

The proposed valve utilizes ferrofluid as passive, tunable constriction element to provide highly predictable opening and closing pressures while maintaining ocular tone. The ferrofluid maintained its magnetic properties in the aqueous environment and provided linear flow to pressure response. Our in-vitro tests showed reliable and reproducible results over a study period of three months. Preliminary in-vivo results were very promising and currently more thorough investigation of this device is underway.