Investigation of a novel implantable suprachoroidal pressure transducer for telemetric intraocular pressure monitoring

The relationship between intraocular pressure and glaucoma: An evolving concept

Intraocular pressure (IOP) is the most important modifiable risk factor for glaucoma and fluctuates considerably within patients over short and long time periods. Our field's understanding of IOP has evolved considerably in recent years, driven by tonometric technologies with increasing accuracy, reproducibility, and temporal resolution that have refined our knowledge regarding the relationship between IOP and glaucoma risk and pathogenesis. The goal of this article is to review the published literature pertinent to the following points: 1) the factors that determine IOP in physiologic and pathologic states; 2) technologies for measuring IOP; 3) scientific and clinical rationale for measuring diverse IOP metrics in patients with glaucoma; 4) the impact and shortcomings of current standard-of-care IOP monitoring approaches; 5) recommendations for approaches to IOP monitoring that could improve patient outcomes; and 6) research questions that must be answered to improve our understanding of how IOP contributes to disease progression. Retrospective and prospective data, including that from landmark clinical trials, document greater IOP fluctuations in glaucomatous than healthy eyes, tendencies for maximal daily IOP to occur outside of office hours, and, in addition to mean and maximal IOP, an association between IOP fluctuation and glaucoma progression that is independent of mean in-office IOP. Ambulatory IOP monitoring, measuring IOP outside of office hours and at different times of day and night, provides clinicians with discrete data that could improve patient outcomes. Eye care clinicians treating glaucoma based on isolated in-office IOP measurements may make treatment decisions without fully capturing the entire IOP profile of an individual. Data linking home blood pressure monitors and home glucose sensors to dramatically improved outcomes for patients with systemic hypertension and diabetes and will be reviewed as they pertain to the question of whether ambulatory tonometry is positioned to do the same for glaucoma management. Prospective randomized controlled studies are warranted to determine whether remote tonometry-based glaucoma management might reduce vision loss and improve patient outcomes.

Long-term astigmatism after intraocular pressure sensor implantation and nonpenetrating glaucoma surgery: EYEMATE-SC trial

PURPOSE

To investigate long-term astigmatism after combined nonpenetrating glaucoma surgery (NPGS) and implantation of the first miniaturized suprachoroidal intraocular pressure (IOP) sensor EYEMATE-SC.

SETTING

The study was conducted in 5 medical centers in 2 different countries.

DESIGN

Retrospective multicenter clinical study.

METHODS

Astigmatism of patients instrumented with the EYEMATE-SC IOP sensor was assessed over a follow-up period of 3 years. Refraction and corrected distance visual acuity (CDVA) were obtained preoperatively, after 6 months, 1, 2, and 3 years. A canaloplasty-operated patient cohort served as control. Astigmatism was evaluated using 3-dimensional power vector analysis involving the spherical equivalent M, and the Jackson crossed cylinder projections J 0 and J 45 . Exclusion criteria included neovascular and angle-closure glaucoma, myopia, axial length outside 22 to 26 mm, other ocular diseases, prior glaucoma surgery, other ocular surgery within 6 months (cataract surgery within 3 months) before NPGS, serious generalized conditions, and other active medical head/neck implants.

RESULTS

Multivariate analysis indicated no changes in astigmatism along the observation period in both the EYEMATE-SC (n = 24) and the canaloplasty (n = 24) group ( P > .05 or nonsignificant after Bonferroni correction). Astigmatism was unchanged between the EYEMATE-SC and the canaloplasty group at all timepoints ( P > .05). CDVA did not change along the observation period of 3 years in each of both groups ( P > .05).

CONCLUSIONS

Despite its suprachoroidal localization, this study indicated that the miniaturized EYEMATE-SC IOP sensor did not negatively affect long-term astigmatism after combined implantation with NPGS.

Microfluidics in the eye: a review of glaucoma implants from an engineering perspective

Glaucoma is a progressive optic neuropathy in the eye, which is a leading cause of irreversible blindness worldwide and currently affects over 70 million individuals. Clinically, intraocular pressure (IOP) reduction is the only proven treatment to halt the progression of glaucoma. Microfluidic devices such as glaucoma drainage devices (GDDs) and minimally invasive glaucoma surgery (MIGS) devices are routinely used by ophthalmologists to manage elevated IOP, by creating an artificial pathway for the over-accumulated aqueous humor (AH) in a glaucomatous eye, when the natural pathways are severely blocked. Herein, a detailed modelling and analysis of both the natural microfluidic pathways of the AH in the eye and artificial microfluidic pathways formed additionally by the various glaucoma implants are conducted to provide an insight into the causes of the IOP abnormality and the improvement schemes of current implant designs. The mechanisms of representative glaucoma implants have been critically reviewed from the perspective of microfluidics, and we have categorized the current implants into four groups according to the targeted drainage sites of the AH, namely Schlemm's canal, suprachoroidal space, subconjunctival space, and ocular surface. In addition, we propose to divide the development and evolution of glaucoma implant designs into three technological waves, which include microtube (1st), microvalve (2nd) and microsystem (3rd). With the emerging trends of minimal invasiveness and artificial intelligence in the development of medical implants, we envision that a comprehensive glaucoma treatment microsystem is on the horizon, which is featured with active and wireless control of IOP, real-time continuous monitoring of IOP and aqueous rate, etc. The current review could potentially cast light on the unmatched needs, challenges, and future directions of the microfluidic structural and functional designs of glaucoma implants, which would enable an enhanced safety profile, reduced complications, increased efficacy of lowering IOP and reduced IOP fluctuations, closed-loop and on-demand control of IOP, etc.

Safety and Efficacy of Three Modifications of Canaloplasty to Treat Open-Angle Glaucoma: 3-Year Outcomes

BACKGROUND

This is a report of 3-year results of a prospective assessment of three modifications of canaloplasty (C): ab externo (ABeC), mini-canaloplasty (miniABeC), and ab interno (ABiC) performed concomitantly with cataract removal in subjects suffering from primary open-angle glaucoma (POAG).

METHODS

Forty-eight individuals were randomized for one of the surgeries: ABeC, miniABeC, or ABiC and cataract removal-16 eyes for each group. Follow-up examinations were carried out on the day of the surgery, on days 1 and 7, after 1, 3, 6 months, and at 1, 2, and 3 years. Complete and qualified success was an IOP ≤ 15 mmHg without or with antiglaucoma eye drops, respectively. The IOP reduction of 20% or more was considered an additional success criterion.

RESULTS

Within three years the probability of qualified success was ABiC and miniABeC-94%, ABeC-100%, and of complete success ABiC-75%, miniABeC-100%. At the 3-year follow-up, the median IOP decreased from 22 to 15 mmHg in the ABeC group (p = 0.001), from 22 to 15 mmHg in the miniABeC group 15 (p < 0.001), and from 21 to 15 mmHg in the ABiC group (p = 0.001) compared to the post-washout stage. The IOP dropped by 20% or more without medications in 56.2% of patients post ABiC, 68.8% post miniABeC and 75% post ABeC. The median number of antiglaucoma medications dropped in all three groups; at the 3-year follow-up, only one patient following ABeC and four subjects following miniABeC required treatment. One patient required reoperation and further intensification of topical treatment-post miniABeC. The levels of IOP, CDVA, and success probability at the 36-month follow-up showed no significant difference for individual groups.

CONCLUSIONS

ABeC, miniABeC, and ABiC have significant IOP-lowering potential in individuals diagnosed with POAG at a mild to moderate stage and no history of IOP ≥ 30 mmHg with a good safety profile.

Advancements in Wearable and Implantable Intraocular Pressure Biosensors for Ophthalmology: A Comprehensive Review

Glaucoma, marked by its intricate association with intraocular pressure (IOP), stands as a predominant cause of non-reversible vision loss. In this review, the physiological relevance of IOP is detailed, alongside its potential pathological consequences. The review further delves into innovative engineering solutions for IOP monitoring, highlighting the latest advancements in wearable and implantable sensors and their potential in enhancing glaucoma management. These technological innovations are interwoven with clinical practice, underscoring their real-world applications, patient-centered strategies, and the prospects for future development in IOP control. By synthesizing theoretical concepts, technological innovations, and practical clinical insights, this review contributes a cohesive and comprehensive perspective on the IOP biosensor's role in glaucoma, serving as a reference for ophthalmological researchers, clinicians, and professionals.

Advances in Canaloplasty-Modified Techniques Yield Strong Pressure Reduction with Low Risk Profile

For decades, trabeculectomy (TE) was considered the gold standard for surgical treatment of open-angle glaucoma owing to its powerful intraocular pressure (IOP)-lowering potency. However, owing to the invasive nature and high-risk profile of TE, this standard is changing, and minimally invasive procedures are becoming more preferable. In particular, canaloplasty (CP) has been established as a much gentler alternative in everyday life and is under development as a full-fledged replacement. This technique involves probing Schlemm's canal with a microcatheter and inserting a pouch suture that places the trabecular meshwork under permanent tension. It aims to restore the natural outflow pathways of the aqueous humor and is independent of external wound healing. This physiological approach results in a significantly lower complication rate and allows considerably simplified perioperative management. There is now extensive evidence that canaloplasty achieves sufficient pressure reduction as well as a significant reduction in postoperative glaucoma medications. Unlike MIGS procedures, the indication is not only mild to moderate glaucoma; today, even advanced glaucoma benefits from the very low hypotony rate, which largely avoids a wipeout phenomenon. However, approximately half of patients are not completely medication-free after canaloplasty. As a consequence, a number of canaloplasty modifications have been developed with the goal of further enhancing the IOP-lowering effect while avoiding the risk of serious complications. By combining canaloplasty with the newly developed suprachoroidal drainage procedure, the individual improvements in trabecular facility and uveoscleral outflow facility appear to have an additive effect. Thus, for the first time, an IOP-lowering effect comparable to a successful trabeculectomy can be achieved. Other implant modifications also enhance the potential of canaloplasty or offer additional benefits such as the possibility of telemetric IOP self-measurement by the patient. This article reviews the modifications of canaloplasty, which has the potential to become a new gold standard in glaucoma surgery via stepwise refinement.

Safety and performance of a suprachoroidal sensor for telemetric measurement of intraocular pressure in the EYEMATE-SC trial

AIM

To investigate the safety and performance of a telemetric suprachoroidal intraocular pressure (IOP) sensor (EYEMATE-SC) and the accuracy of its IOP measurements in open angle glaucoma (OAG) patients undergoing simultaneous non-penetrating glaucoma surgery (NPGS).

METHODS

Prospective, multicentre, open-label, single-arm, interventional clinical trial. Twenty-four eyes of 24 patients with OAG regularly scheduled for NPGS (canaloplasty or deep sclerectomy) were simultaneously implanted with an EYEMATE-SC sensor. Six-month follow-up on the sensor's safety and performance as well as on the level of agreement between the EYEMATE-SC measurements and IOP measurements with Goldmann applanation tonometry (GAT).

RESULTS

The eyes underwent canaloplasty (n=15) or deep sclerectomy (n=9) and achieved successful implantation of the sensor. No device migration, dislocation or serious device-related complications occurred. A total of 367 comparisons were included in the IOP agreement analysis. The overall mean difference between GAT and EYEMATE-SC measurements was 1.31 mm Hg (lower limit of agreement (LoA) 7.55 mm Hg; upper LoA -4.92 mm Hg). The maximum difference of 2.5 mm Hg ±3.96 (LoA 0.30-2.29) was reached on day 10 and continuously improved to an agreement of -0.15 mm Hg ±2.28 (LoA -1.24 to 0.89) after 6 months. Accordingly, the percentage of eyes within an IOP difference of ±5 mm Hg improved from 78% (day 3) to 100% (6 months).

CONCLUSIONS

After 6 months, the EYEMATE-SC sensor was safe and well tolerated, and allowed continual IOP monitoring.

TRIAL REGISTRATION NUMBER

NCT03756662.

EYEMATE-SC Trial: Twelve-Month Safety, Performance, and Accuracy of a Suprachoroidal Sensor for Telemetric Measurement of Intraocular Pressure

PURPOSE

Measuring and controlling intraocular pressure (IOP) provide the foundation for glaucoma treatment. Self-tonometry has been proposed as an alternative to measure IOP throughout the entire day better. The novel EYEMATE-SC sensor (Implandata) is implanted in the suprachoroidal space to enable contactless continual IOP monitoring. The aim of the present study was to investigate the 1-year safety, performance, and accuracy of the EYEMATE-SC in patients with primary open-angle glaucoma undergoing simultaneous nonpenetrating glaucoma surgery (NPGS).

DESIGN

Prospective, multicenter, open-label, single-arm, interventional clinical trial.

PARTICIPANTS

Twenty-four eyes of 24 patients with primary open-angle glaucoma who were due to undergo NPGS (canaloplasty or deep sclerectomy).

METHODS

An EYEMATE-SC sensor was implanted during NPGS. Goldmann applanation tonometry (GAT) measurements were compared with the sensors' IOP measurements at all postoperative visits through 12 months.

MAIN OUTCOME MEASURES

Device position and adverse events.

RESULTS

Fifteen eyes underwent canaloplasty, and 9 underwent deep sclerectomy. Successful implantation of the sensor was achieved in all eyes with no reported intraoperative difficulties. Through the 12-month follow-up, no device migration, dislocation, or serious device-related complications were recorded. A total of 536 EYEMATE-SC measurements were pairwise included in the IOP agreement analysis. The overall mean difference between GAT and EYEMATE-SC measurements was 0.8 mmHg (95% confidence interval [CI] of the limits of agreement [LoA], -5.1 to 6.7 mmHg). The agreement gradually improved, and from 3 months after surgery until the end of the follow-up, the mean difference was -0.2 mmHg (95% CI of LoA, -4.6 to 4.2 mmHg) over a total of 264 EYEMATE-SC measurements, and 100% of measurements were within ±5 mmHg of GAT.

CONCLUSIONS

The EYEMATE-SC sensor was safe and well tolerated through 12 months. Moreover, it allowed accurate, continuous IOP monitoring.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found after the references.

[Tonometry: Review and Perspectives]

Reliable and repeated IOP measurement are essential in the diagnosis and treatment of glaucoma. In this second part, the other contact tonometry and non-contact tonometry are presented. The clinical value of the different methods and the value of multimodality in tonometry will be discussed based on a review of the literature, and the latest innovations with telemetric IOP sensors will be introduced.

Tonometrie: Rückblick und Ausblick (Teil 2)

In 2. Teil des Beitrags werden die sonstigen Kontakttonometer und die Nonkontakttonometrie präsentiert. Es wird anhand einer Revue der Literatur über den klinischen Wert der verschiedenen Methoden und den Wert der Multimodalität in der Tonometrie diskutiert; ferner werden die letzten Innovationen mit den telemetrischen IOD-Sensoren eingeführt.

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.

Intraocular Pressure Telemetry for Managing Glaucoma during the COVID-19 Pandemic

PURPOSE

To evaluate in glaucoma patients the feasibility and use of remote monitoring of intraocular pressure (IOP) with an implanted telemetry sensor during the coronavirus disease 2019 (COVID-19) lockdown.

DESIGN

Cross-sectional study.

PARTICIPANTS

Patients previously implanted with a telemetric IOP sensor (Eyemate; Implandata GmbH) were included.

METHODS

Intraocular pressure measurements acquired by the patients during the lockdown were collected by physicians who were located remotely. A questionnaire was sent to 10 participating study centers to evaluate the clinical impact of remote monitoring of IOP via the IOP sensor system.

MAIN OUTCOME MEASURES

Number of patients who obtained home IOP measurements.

RESULTS

Data were available from all centers and from 37 eyes of 37 patients (16 patients with a sulcus-based sensor and 21 patients with a suprachoroidal sensor). Thirty-four patients obtained IOP measurements during the lockdown. Mean age of the patients was 69.3 ± 9.6 years, and 48.6% were women. A total of 8415 IOP measurements from 370 measurement days were obtained. Based on remote IOP measurements, treatment was changed in 5 patients. In another 5 patients, treatment change was considered when physicians received the IOP measurements after the lockdown. Nine of the 10 study centers judged remote IOP measurements to have a clinical impact.

CONCLUSIONS

These results show the feasibility of patient-acquired measurement of IOP in conjunction with remote IOP monitoring by physicians with an implantable sensor. The data obtained impacted clinical decision making, including adjustment of ocular hypotensive therapy and avoiding unnecessary office visits during the COVID-19 pandemic.

Enhanced depth imaging in swept-source optical coherence tomography: Improving visibility of choroid and sclera, a masked study

Purpose

To compare enhanced depth imaging in swept-source optical coherence tomography and non–enhanced depth imaging optical coherence tomography in their ability to capture choroidal and scleral details.

Methods

Averaged foveal B-Scans were obtained from 40 eyes of 20 healthy volunteers by swept-source optical coherence tomography with and without enhanced depth imaging. Visibility and contrast of vascular details within the choroid, choroidoscleral junction, and sclera were evaluated by masked readers using an ordinal scoring scale. Outcomes were analyzed using the Wilcoxon signed rank-sum test.

Results

Visibility of the choroidal vascular details ( Z = 5.94, p < .001), the choroidoscleral junction ( Z = 5.85, p < .001), and the sclera ( Z = 6.80, p < .001) was significantly higher with enhanced depth imaging than with non–enhanced depth imaging swept-source optical coherence tomography. Similarly, image contrast was significantly higher with enhanced depth imaging than with non–enhanced depth imaging swept-source optical coherence tomography for the choroidal vascular details ( Z = 9.47, p < .001), for the choroidoscleral junction ( Z = 9.28, p < .001), and for the sclera ( Z = 9.42, p < .001).

Conclusion

Enhanced depth imaging applied to swept-source optical coherence tomography–averaged foveal B-scans enhances visualization of the choroidal details, of the choroidoscleral junction, and of the sclera. This novel modality can easily be implemented in clinics and could improve our understanding of conditions involving the choroid or the sclera.

Ultrathin and Robust Micro-Nano Composite Coating for Implantable Pressure Sensor Encapsulation

Implantable pressure sensors enable more accurate disease diagnosis and real-time monitoring. Their widescale usage is dependent on a reliable encapsulation to protect them from corrosion of body fluids, yet not increasing their sizes or impairing their sensing functions during their lifespans. To realize the above requirements, an ultrathin, flexible, waterproof while robust micro-nano composite coating for encapsulation of an implantable pressure sensor is designed. The composite coating is composed of a nanolayer of silane-coupled molecules and a microlayer of parylene polymers. The mechanism and principle of the composite encapsulation coating with high adhesion are elucidated. Experimental results show that the error of the sensors after encapsulation is less than 2 mmHg, after working continuously for equivalently over 434 days in a simulated body fluid environment. The effects of the coating thickness on the waterproof time and the error of the sensor are also studied. The encapsulated sensor is implanted in an isolated porcine eye and a living rabbit eye, exhibiting excellent performances. Therefore, the micro-nano composite encapsulation coating would have an appealing application in micro-nano-device protections, especially for implantable biomedical devices.

Top-Down Strategy of Implantable Biosensor Using Adaptable, Porous Hollow Fibrous Membrane

Fabrication of an outer membrane is crucial for an implantable biosensor to enhance the long-term stability and accuracy of sensors. Herein, an adaptable, controllable, porous outer membrane for an implantable biosensor was fabricated using a "top-down" method, allowing maximum retention of enzyme activity and fine control over membrane microstructure. Polysulfone hollow fibrous membranes with different pore sizes and porosities were used as a base membrane. Chitosan (CH) and sodium alginate (SA) were self-assembled on the inner surface of PSfHM to construct a biocompatible and conductive interface between PSfHM and the electrode. In vitro and in vivo experiments were used to evaluate the performance of implantable glucose biosensors with PSfHM and CH/SA modified PSfHM (PSfHM-CH/SA). The glucose biosensor with PSfHM-CH/SA exhibited a more stable output current than bare sensors and a quick response time (<50 s). The glucose biosensor with PSfHM-CH/SA linear sensing range was between 0 and 22 mM ( R² = 0.9905), and relative sensitivity remained at >87% within 7 days and >76% within 15 days. Furthermore, response currents recorded by implanted sensors closely followed the blood glucose trend from the tail vein blood during in vivo experiments.

New Technologies for Glaucoma Detection

This review describes some of the most recent advances in the development and application of new technologies for detecting and managing glaucoma, including imaging, visual function testing, and tonometry. The widespread availability of mobile technology in the developing world is improving health care delivery, for example, with smartphones and mobile applications that allow patient data to be assessed remotely by health care providers.

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.

Moving From Clinic to Home: What the Future Holds for Ophthalmic Telemedicine

PURPOSE

To describe the expanding role of telemedicine in healthcare, the key criteria required for a successful device and program implementation, and the current and future role of home monitoring in ophthalmology.

DESIGN

Expert perspective.

METHODS

Analysis with real-world interpretation of home monitoring technologies, including current adoption barriers and expanded future demands based on demographic and market forces.

RESULTS

Remote patient monitoring represents a paradigm shift in the way physicians care for patients. Success depends on meeting several criteria, among which are a recognized value proposition to the physician, robust device performance validation, ease of use for the patient, reliability of connectivity, safe and secure data transmission, and economic feasibility. Ophthalmic diseases, such as age-related macular degeneration, glaucoma, and diabetic retinopathy, are ideal candidates for home monitoring practice integration. Established home monitoring technology is already facilitating early detection and improved visual outcomes for patients with age-related macular degeneration. Future innovation currently underway or on the horizon will continue to evolve and expand the footprint of telemedicine within ophthalmology.

CONCLUSION

Home monitoring has the potential to enhance the patient-physician relationship and to positively impact visual acuity outcomes in ophthalmic diseases. Advances in technology, demographic shifts, market changes, and patient demand for personalized medicine will require physicians to embrace technology in new and diverse ways, perhaps facilitating widespread adoption of home monitoring technology platforms.

Twenty-four hour intraocular pressure measurements and home tonometry

PURPOSE OF REVIEW

IOP is the only treatable risk factor contributing to glaucoma and most management and treatment of glaucoma is based on IOP. However, current IOP measurements are limited to office hours and control of glaucoma in many patients would benefit from the ability to monitor IOP diurnally so as not to miss abnormal pressures, which occur outside of office hours Consequently, to improve patient care, the ability to enable accurate and minimally disruptive diurnal IOP monitoring would improve caring for these patients.

RECENT FINDINGS

The studies we selected for this review can be divided into three categories: self-/home-tonometry, continuous invasive intraocular pressure measurements, and continuous noninvasive ocular measurements.

SUMMARY

The desire to obtain better insight in our patients' true diurnal IOP has led to the development of home-tonometers, in addition to extraocular and intraocular continuous pressure measurement devices. All of the devices have respective advantages and disadvantages, but none to date completely fulfills the goal of providing a true diurnal IOP profile.Video abstracthttp://links.lww.com/COOP/A27.

Implantation and testing of a novel episcleral pressure transducer: A new approach to telemetric intraocular pressure monitoring

Measurement of intraocular pressure (IOP) is an essential tool in monitoring glaucoma. Single IOP assessments during clinical routine examinations represent punctual values and are not able to identify IOP fluctuations and spikes. Telemetric IOP measurements are able to monitor IOP during the day and night, and are location-independent. Six telemetric episcleral IOP sensors were investigated after minimally invasive subconjunctival implantation in 6 eyes of 6 New-Zealand-White rabbits. Three of the 4 edges of the implant were fixated intrasclerally with non-absorbable sutures. The sutures were stitched into the edges of the implants' silicone rubber encasements. Telemetric IOP measurements were validated 1 week, 4 weeks, 8 weeks, 12 weeks and 30 weeks after implantation. For each validation the anterior chamber was cannulated and connected to a height-adjustable water column. Different intracameral pressure levels (10-45 mmHg) were generated by height adjustment of the water column. Measurement reliability and concordance between telemetric and intracameral IOP was validated using Bland-Altman analysis. Overall comparison (10-45 mmHg) between telemetric and intracameral pressure revealed a standard deviation of ±1.0 mmHg. A comparison of pressure values in the range between 10 and 30 mmHg revealed a standard deviation of ±0.8 mmHg. Device deficiency was related to follow-up length: 4 weeks after implantation, 3 of the 6 sensors showed malfunction, with all sensors having failed 30 weeks after implantation. The most likely reason for the sensor malfunction is the loss of hermeticity as a result of penetration of the encasement during the episcleral fixation, resulting from the lack of preformed suture holes at the implants encasement. However, no clinical signs of injury or inflammation of the conjunctiva, sclera, implantation site or any other involved structures were observed, except for an expected mild short-term irritation postoperatively. The episcleral pressure transducer for telemetric IOP monitoring is able to assess IOP without the need for invasive intraocular surgery. Episcleral implantation is an easy and safe procedure and can be undone very easily, so even temporary implantation and IOP measurements could be possible in the future. Sensor malfunction over time is a problem that needs to be addressed. Improvements in sensor encapsulation and especially preformed suture holes could significantly decrease the failure rate and increase durability.