Contact Lens Sensor with Anti-jamming Capability and High Sensitivity for Intraocular Pressure Monitoring

Contact lens sensors provide a noninvasive approach for intraocular pressure (IOP) monitoring in patients with glaucoma. Accurate measurement of this imperceptible pressure variation requires highly sensitive sensors in the absence of simultaneously amplifying IOP signal and blinking-induced noise. However, current noise-reduction methods rely on external filter circuits, which thicken contact lenses and reduce signal quality. Here, we introduce a contact lens strain sensor with an anti-jamming ability by utilizing a self-lubricating layer to reduce the coefficient of friction (COF) to remove the interference from the tangential force. The sensor achieves exceptionally high sensitivity due to the strain concentration layout and the confined occurrence of sympatric microcracks. The animal tests prove our lens can accurately detect IOP safely and reliably.

Circadian Fluctuation Changes in Intraocular Pressure Measured Using a Contact Lens Sensor in Patients with Glaucoma after the Adjunctive Administration of Ripasudil: A Prospective Study

Nocturnal and circadian intraocular pressure (IOP) fluctuations are important issues in glaucoma treatment. Ripasudil 0.4% eye drops, a new glaucoma medication, lowers IOP by increasing aqueous humor outflow through the trabecular meshwork. We aimed to compare differences between circadian IOP fluctuations measured using a contact lens sensor (CLS) before and after administering 0.4% ripasudil eye drops adjunctively to patients with primary open-angle glaucoma (POAG) and normal tension glaucoma (NTG). Patients with POAG (n = 1) and NTG (n = 5) underwent 24 h IOP monitoring with a CLS before and after administering ripasudil eye drops every 12 h (8 a.m., 8 p.m.) for 2 weeks without discontinuing currently used glaucoma medications. No vision-threatening adverse event occurred. The reduction in IOP fluctuation and the reduction in the SD of IOP in 24 h, awake time and sleep time did not reach statistical significance. The baseline office-hour IOP, which was measured using Goldmann applanation tonometry (GAT), ranged in the low teens, and the reduction in office-hour IOP also did not show a significant difference. Further study is necessary to evaluate whether the low baseline IOP with less IOP reduction relates to attenuated IOP fluctuation reduction.

Using 24-hr ocular dimensional profile recorded with a sensing contact lens to identify primary open-angle glaucoma patients with intraocular pressure constantly below the diagnostic threshold

PURPOSE

To evaluate the use of a 24-hr ocular dimensional profile recorded with a contact lens sensor (CLS) combined with a single tonometric intraocular pressure (IOP) reading to indicate the potential for exceeding the diagnostic threshold for normal tension glaucoma (NTG) in Japanese patients.

METHODS

Intraocular pressure (IOP) of untreated Japanese NTG patients was measured with tonometry every 3 hr from 9:00 to 24:00. The subsequent day a 24-hr CLS (SENSIMED Triggerfish, Sensimed AG, Lausanne, Switzerland) profile was recorded on the same eye. Patients initially diagnosed as NTG were reclassified as NTG when the measured IOP values were consistently <20 mmHg or as primary open-angle glaucoma (POAG) when IOP was ≥20 mmHg in at least 1 measurement. For each patient and each IOP time-point, IOP values were combined with information provided by the CLS profile ('classifier') to indicate the potential for exceeding the diagnostic threshold value. Statistical analyses were performed for each classifier.

RESULTS

A total of 65 patients, 28 males and 37 females (mean ages: 50.8 ± 14.6 years and 52.6 ± 10.2 years, respectively), were analysed. Following IOP diurnal measurement, five patients (7.7%) were reclassified as POAG. Two classifiers (15:00 CLS and 18:00 CLS) showed high sensitivity and negative predictive value (100%), identifying all the POAG patients.

CONCLUSION

Contact lens sensor information can be used in conjunction with a single tonometric reading to determine patients' potential of having IOP levels exceeding the diagnostic threshold within a 24-hr period, without the need to perform a 24-hr tonometric curve. This would allow clinicians to identify POAG patients who may otherwise be eventually misclassified as NTG.

24-hour Intraocular pressure monitoring: the way ahead

Aim: Large diurnal intraocular pressure (IOP) fluctuation is a single most independent risk factor for glaucoma progression besides raised IOP. The major limitation of Goldman applanation tonometer (GAT) is its inability to measure night IOP without disturbing the patient's sleep. We discussed the methods available for the 24-hour IOP monitoring and its relevance in glaucoma. Methods: A PUBMED search was performed using the 24 Hour tonometry, newer tonometry devices, contact lens sensors, as keywords and all relevant articles were studied. Results and Conclusion: A number of methods are available for the 24 hour IOP monitoring. These devices allow home monitoring of IOP without affecting the daily routine. These devices, like Rebound tonometry, Contact lens sensor (CLS), etc., were briefly discussed. Triggerfish is one CLS device that has the capability to measure IOP without affecting the patient's sleep. Besides being safe and easily tolerable, it has shown reproducible results with other tonometry methods. Triggerfish has also been proven the device of choice in measuring IOP in different glaucoma subtypes and determining the efficacy of treatment in them, the only challenge being that it presently provides data on relative IOP rather than absolute IOP. With future research, triggerfish CLS can become an important device to measure the 24 hour IOP values especially in patients whose office measured IOPs seemingly fit in patient's target range but still the patients' disease shows glaucomatous progression. The utility of this device in relation to progressive vision loss is a matter of future study. Abbreviations: CCT = Central Corneal Thickness; CLS = Contact lens sensor; GAT = Goldmann Applanation Tonometer; IOP = Intraocular Pressure; NTG = Normal Tension Glaucoma; PACG = Primary angle closure glaucoma; POAG = Primary open angle glaucoma; VAS = Visual Analogue Score.

Comparison of intraocular pressure fluctuations before and after ab interno trabeculectomy in pseudoexfoliation glaucoma patients

Purpose

Ab interno trabeculectomy (AIT) with the Trabectome has been shown to reduce intraocular pressure (IOP) in eyes with pseudoexfoliation (PEX) glaucoma. Here, we examined the change of IOP fluctuations before and after only AIT or AIT with cataract surgery in PEX patients using the contact lens sensor Triggerfish^®.

Methods

This was a prospective open-label study. Twenty-four consecutive patients with PEX glaucoma were included. Twelve patients underwent cataract surgery and AIT (triple-surgery group), and 12 patients underwent only AIT (single-surgery group). In each eye, IOP fluctuations over 24 h were measured with the contact lens sensor before and at 3 months after the surgery. We compared the change of IOP fluctuation before and after operation. We also evaluated the difference in IOP changes between the triple- and single-surgery groups.

Results

At 3 months after the surgeries, the mean IOP was significantly reduced from 23.5±6.5 mmHg to 14.6±2.8 mmHg in the single-surgery group and from 22.5±3.0 mmHg to 11.5±2.9 mmHg in the triple-surgery group. The mean IOP reduction rate was significantly higher in the triple-surgery group compared to the single-surgery group (p=0.0358). In both groups, the mean range of IOP fluctuations was significantly decreased during nocturnal periods. The mean range of 24 h IOP fluctuations was decreased in the triple-surgery group (p=0.00425), not in the single-surgery group (p=0.970).

Conclusion

Triple surgery could decrease IOP value and the IOP fluctuations to a greater extent than single surgery in PEX glaucoma patients.

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.

Correlation between short-term and long-term intraocular pressure fluctuation in glaucoma patients

Purpose

We investigated correlations between short-term and long-term intraocular pressure (IOP) fluctuations.

Methods

We examined 50 eyes of glaucoma patients who were followed for >2 years. We measured short-term IOP fluctuation using a Triggerfish^® contact lens sensor (CLS). The short-term IOP fluctuation (mVeq) was defined as the difference between the maximum value and the minimum value measured during the 24-hour course with CLS. The long-term IOP fluctuation was defined by four parameters: 1) the mean IOP (mmHg) determined during follow-up; 2) the IOP difference, which was defined as the difference between the maximum IOP and the minimum IOP; 3) the standard deviation of IOP; and 4) the peak IOP, which was defined as the maximum IOP. Correlations between these parameters and the short-term IOP fluctuation were examined.

Results

The mean follow-up period was 5.4 years. The average IOP was 15.0±4.0 mmHg. The range of short-term IOP fluctuation identified with CLS was significantly correlated with all the four long-term IOP fluctuation parameters.

Conclusion

Short-term IOP fluctuations were found to be associated with long-term IOP fluctuations. Examination of 24-hour IOP fluctuations with the CLS might be useful for predicting the long-term IOP fluctuation.

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.

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.

Automated Detection and Quantification of Circadian Eye Blinks Using a Contact Lens Sensor

PURPOSE

To detect and quantify eye blinks during 24-hour intraocular pressure (IOP) monitoring with a contact lens sensor (CLS).

METHODS

A total of 249 recordings of 24-hour IOP patterns from 202 participants using a CLS were included. Software was developed to automatically detect eye blinks, and wake and sleep periods. The blink detection method was based on detection of CLS signal peaks greater than a threshold proportional to the signal amplitude. Three methods for automated detection of the sleep and wake periods were evaluated. These relied on blink detection and subsequent comparison of the local signal amplitude with a threshold proportional to the mean signal amplitude. These methods were compared to manual sleep/wake verification. In a pilot, simultaneous video recording of 10 subjects was performed to compare the software to observer-measured blink rates.

RESULTS

Mean (SD) age of participants was 57.4 ± 16.5 years (males, 49.5%). There was excellent agreement between software-detected number of blinks and visually measured blinks for both observers (intraclass correlation coefficient [ICC], 0.97 for observer 1; ICC, 0.98 for observer 2). The CLS measured a mean blink frequency of 29.8 ± 15.4 blinks/min, a blink duration of 0.26 ± 0.21 seconds and an interblink interval of 1.91 ± 2.03 seconds. The best method for identifying sleep periods had an accuracy of 95.2 ± 0.5%.

CONCLUSIONS

Automated analysis of CLS 24-hour IOP recordings can accurately quantify eye blinks, and identify sleep and wake periods.

TRANSLATIONAL RELEVANCE

This study sheds new light on the potential importance of eye blinks in glaucoma and may contribute to improved understanding of circadian IOP characteristics.

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.