Corneal biomechanics and glaucoma beyond the bidirectional impact of intraocular pressure and corneal deformation response / Biomecânica corneana e glaucoma além do impacto bididirecional da pressão intraocular e da resposta da deformação corneana

ABSTRACT The purpose of this study was to highlight the impact of biomechanical corneal response in available in vivo tonometry methods for glaucoma management. Systematic review of non-contact air-puff tonometers that analyzes the corneal deformation response, with special focus on the investigation of the correlation of derived parameters with intraocular pressure measurements. The two actual and commercially available in vivo corneal tonometers provide promising information about biomechanical characteristics of the cornea and its relation to glaucoma, allowing the development of new protocols to evaluate, diagnose, and manage this disease.

RESUMO O objetivo deste estudo é destacar o impacto da resposta biomecânica corneana em métodos de tonometria in vivo disponíveis para o manejo do glaucoma. Trata-se de revisão sistemática de tonômetros de ar que analisa a resposta à deformação corneana, com foco especial na investigação da correlação dos parâmetros derivados com as medições da pressão intraocular. Os dois tonômetros mais recentes e comercialmente disponíveis fornecem informações promissoras sobre as características biomecânicas da córnea e sua relação com o glaucoma, permitindo o desenvolvimento de novos protocolos para avaliar, diagnosticar e controlar a doença.

Weekly and seasonal changes of intraocular pressure measured with an implanted intraocular telemetry sensor.

BACKGROUND/AIMS: To better understand seasonal and weekday intraocular pressure (IOP) variations, long-term daily IOP measurements were assessed in patients with glaucoma using an intraocular telemetric sensor. METHODS: This prospective, open-label, multicentre observational study analysed the IOP variation patterns in 22 eyes of 22 patients with primary open-angle glaucoma (67.8±6.8 years, 36.4% female) who had undergone placement of an intraocular telemetric sensor at the time of cataract surgery. The telemetric system combines an implantable IOP sensor with a hand-held reading device. Patients were instructed to self-measure their IOP as often as desired, but at least four times daily. Analysis of variance and Tukey multiple-comparison correction were used to assess the statistical significance of average and peak IOP variations between individual weekdays and months. RESULTS: Each enrolled patient recorded daily IOP measurements for an average duration of 721 days. On average, IOPs were highest on Wednesdays and lowest on Fridays (p=0.002). There were significant variations of IOP throughout the year, and IOP showed a seasonal pattern. Between mid-winter (December-January) and mid-summer months, there was a reduction in mean IOP of 8.1% (-1.55 mm Hg, p<0.05). CONCLUSION: This study confirms previously observed seasonal variations of IOP. IOP was significantly higher in winter compared with summer months. Moreover, IOP was lower on Friday than on other days. The explanation for these results is not known.

Economic and Environmental Impact of Single-use Plastics at a Large Ophthalmology Outpatient Service.

PRéCIS:: The use of disposable tonometer prisms and gonioscopy lenses at a large ophthalmology outpatient service incurs significant financial and environmental waste that may not be justified given the limited data surrounding arguments for their use. PURPOSE: To quantify the economic and environmental burden of single-use plastics from an ophthalmology outpatient service at a large tertiary hospital and describe the relative value and evidence for the safety of disposable versus nondisposable tonometer prisms and gonioscopy lenses. METHODS: The total number of single-use applanation tonometer prisms and gonioscopy lenses used per year at Boston Medical Center (BMC) was estimated, and the average dollars spent and plastic waste generated in kilograms per year were then determined. These values were compared with the total spending and waste that would be produced if the clinic were to use nondisposable tonometer prisms and gonioscopy lenses exclusively. RESULTS: Single-use tonometer prisms cost an average of $70,282 per year and produce ~100.8 kg of plastic waste per year at BMC. Single-use gonioscopy lenses cost ~$9,040 per year and produce 8.8 kg of plastic waste per year at BMC. An excess of $65,185 and 109.6 kg of plastic waste could be avoided each year by only using nondisposable tonometer prisms and gonioscopy lenses at the BMC ophthalmology outpatient service. CONCLUSIONS: Single-use plastics in ophthalmology outpatient services generate significant environmental waste and financial cost compared with nondisposable instruments. This cost may outweigh the benefits of these instruments given the limited data surrounding arguments for their use.

Device profile of the EYEMATE-IO™ system for intraocular pressure monitoring: overview of its safety and efficacy.

INTRODUCTION: Assessment of intraocular pressure (IOP) is a core diagnostic tool in management of glaucoma. All established ways to measure IOP use indirect approaches through ocular tissues, mainly the cornea or the sclera. Telemetric IOP measurement with an implantable device could eliminate bias caused by indirect techniques and could allow continuous monitoring. A favorable safety profile, high efficacy and good tolerability are key requirements. AREAS COVERED: The Eyemate-IO™ system (Implandata Ophthalmic Products GmbH, Hannover, Germany) is a novel CE-marked implantable medical device for direct measurement of IOP. It consists of an intraocular sensor ring and an external reading device. This review presents the mechanism of telemetric IOP measurement and summarizes the available clinical data. Twelve months follow-up data of two clinical trials provide support for the efficacy and safety of this device. EXPERT OPINION: The implantable Eyemate-IO™ in keratoprosthesis was well tolerated; recorded adverse events were known complications of standalone surgery. The system had a good agreement with other IOP measuring modalities, including intraoperative manometry. In glaucoma patients, the Eyemate-IO™ could be implanted safely and showed a favorable efficacy and safety profile in the first twelve months postoperatively. The potential to achieve IOP monitoring with the Eyemate-IO™ seems promising.

Comparison of intraocular pressure measured by ocular response analyzer and Goldmann applanation tonometer after corneal refractive surgery: a systematic review and meta-analysis.

BACKGROUND: Accurate measurement of intraocular pressure (IOP) after corneal refractive surgery is of great significance to clinic, and comparisons among various IOP measuring instruments are not rare, but there is a lack of unified analysis. Although Goldmann Applanation Tonometer (GAT) is currently the internationally recognized gold standard for IOP measurement, its results are severely affected by central corneal thickness (CCT). Ocular Response Analyzer (ORA) takes certain biomechanical properties of cornea into account and is supposed to be less dependent of CCT. In this study, we conducted the meta-analysis to systematically assess the differences and similarities of IOP values measured by ORA and GAT in patients after corneal refractive surgery from the perspective of evidence-based medicine. METHODS: The authors searched electronic databases (MEDLINE, EMBASE, Web of science, Cochrane library and Chinese electronic databases of CNKI and Wanfang) from Jan. 2005 to Jan. 2019, studies describing IOP comparisons measured by GAT and ORA after corneal refractive surgery were included. Quality assessment, subgroup analysis, meta-regression analysis and publication bias analysis were applied in succession. RESULTS: Among the 273 literatures initially retrieved, 8 literatures (13 groups of data) with a total of 724 eyes were included in the meta-analysis, and all of which were English literatures. In the pooled analysis, the weighted mean difference (WMD) between IOPcc and IOPGAT was 2.67 mmHg (95% CI: 2.20~3.14 mmHg, p < 0.0001), the WMD between IOPg and IOPGAT was - 0.27 mmHg (95% CI: - 0.70~0.16 mmHg, p = 0.2174). In the subgroup analysis of postoperative IOPcc and IOPGAT, the heterogeneity among the data on surgical procedure was zero, while the heterogeneity of other subgroups was still more than 50%. The comparison of the mean difference of pre- and post-operative IOP (∆IOP) was: mean-∆IOPg > mean-∆IOPGAT > mean-∆IOPcc. CONCLUSIONS: IOPcc, which is less dependent on CCT, may be more close to the true IOP after corneal refractive surgery compared with IOPg and IOPGAT, and the recovery of IOPcc after corneal surface refractive surgery may be more stable than that after lamellar refractive surgery.

Telemetric Measurement of Intraocular Pressure via an Implantable Pressure Sensor-12-Month Results from the ARGOS-02 Trial.

PURPOSE: The aim of this study was to investigate the safety and performance of the second generation of an implantable intraocular pressure (IOP) sensor in patients with primary open angle glaucoma (POAG). DESIGN: prospective, noncomparative, open-label, multicenter clinical investigation. METHODS: In this study, patients with POAG, regularly scheduled for cataract surgery, were implanted with a ring-shaped, sulcus-placed, foldable IOP sensor in a single procedure after intraocular lens implantation. Surgical complications as well as adverse events (AEs) during 12 months of follow-up were recorded. At each follow-up visit, a complete ophthalmic examination, including visual acuity, IOP, slit lamp examination, and dilated funduscopy as well as comparative measurements between Goldmann applanation tonometry and the EYEMATE-IO implant were performed. RESULTS: The EYEMATE-IO implant was successfully implanted in 22 patients with few surgical complications and no unexpected device-related AEs. All ocular AEs resolved quickly under appropriate treatment. Comparative measurements showed good agreement between EYEMATE-IO and Goldmann applanation tonometry (GAT) with an intraclass correlation coefficient (ICC(3,k)) of 0.783 (95% confidence interval [CI]: 0.743, 0.817). EYEMATE-IO measurements were higher than GAT, with a mean difference of 3.2 mm Hg (95% CI: 2.8, 3.5 mm Hg). CONCLUSIONS: The EYEMATE-IO sensor was safely implanted in 22 patients and performed reliably until the end of follow-up. This device allows for continual and long-term measurements of IOP.

A Wireless Handheld Pressure Measurement System for In Vivo Monitoring of Intraocular Pressure in Rabbits.

Intraocular pressure (IOP) is the leading modifiable risk factor for preventing vision loss in glaucoma patients. Direct and frequent IOP measurements are highly desirable to assess adequacy of treatment and prevent further vision loss. In this study, we report on successful in vivo measurements of intraocular pressure in rabbits using an optical IOP measurement system. The sensor was implanted during cataract surgery in two New Zealand white (NZW) rabbits and tested in vivo for ten weeks. Prior to implantation, the sensors were characterized in vitro in the physiologically relevant pressure range of 0-60 mmHg. A portable wireless handheld reader consisting of an internal beam splitter, a monochromatic light source, and a digital single-lens reflex (DSLR) camera was also designed and implemented to capture interference patterns from the sensor. The sensitivity and accuracy of the sensor was 30 nm/mmHg and ±0.2 mmHg, respectively. Ten weeks post-implantation, the two NZW rabbits continued to respond well to the implant with no observable inflammation, signs of infection, or biofouling. All IOP measurements were obtained using the portable DSLR handheld reader. Successful in vivo studies demonstrate biocompatibility of the IOP sensor and prove feasibility of the IOP measurement system. The system has the potential to be used in both clinical and patient point-of-care (home) settings to frequently and accurately measure pressure.

A comparison of Icare PRO and Perkins tonometers in anesthetized children.

AIM: To compare intraocular pressure (IOP) measurements obtained with the Perkins applanation tonometer and Icare PRO (ICP) rebound tonometer in anesthetized aphakic or strabismus children. Furthermore, intra-operator correlation and inter-operator correlation have been evaluated, along with the effects of central corneal thickness (CCT) on IOP measurements. METHODS: Seventy children undergoing examination under anesthesia with sevoflurane for aphakic patients and for surgery for strabismus were included. IOP have been measured twice immediately after anesthesia induction with both Perkins applanation tonometer (PAT) and ICP in one eye and by two different operators with both devices in the fellow eye. Furthermore, CCT was measured with ultrasound pachymetry Pacline (Optikon). Agreement between the device measurements has been evaluated using Bland-Altman analyses. Repeatability and reproducibility of the device have been evaluated with intraclass correlation coefficient (ICC) with a value > 0.75 associated with excellent reliability. The relationship between IOP and CCT has been evaluated with Spearman's correlation coefficient r and determination coefficient r2. RESULTS: Mean difference in IOP measurements between ICP and PAT was 1.97 mmHg ± 1.23 mmHg (p < 0.05). This difference appeared to be higher in aphakic patients (mean difference 2.15 ± 1.35) than in patients undergoing strabismus surgery (mean difference 1.83 mmHg ± 1.12). Intraclass correlation coefficient (ICC) is used to evaluate repeatability and reproducibility, which are both high for PAT (repeatability 0.96, reproducibility 0.76) compared with ICP (repeatability 0.81, reproducibility 0.70). Correlation coefficient between CCT and IOP is 0.66 for both ICP and PAT. CONCLUSION: ICP tends to overestimate IOP compared to PAT. Repeatability and reproducibility are both high for PAT as compared to ICP. A significant correlation between IOP and CCT for both instruments has been demonstrated.

Effectiveness of the Goldmann Applanation Tonometer, the Dynamic Contour Tonometer, the Ocular Response Analyzer and the Corvis ST in Measuring Intraocular Pressure following FS-LASIK.

Purpose: To test the performance of the four tonometers in providing IOP measurements that were free of the effects of corneal biomechanics changes caused by refractive surgery.Methods: Four tonometers were employed to provide IOP measurements for 65 participants who accepted Femtosecond laser-assisted LASIK (FS-LASIK). The measurements included GAT-IOP by the Goldmann Applanation Tonometer, DCT-IOP by the Dynamic Contour Tonometer, Goldmann-correlated IOP (ORA-IOPg) and corneal-compensated IOP (ORA-IOPcc) by the Ocular Response Analyzer, and uncorrected IOP (CVS-IOP) and biomechanically corrected IOP (CVS-bIOP) by the Corvis ST. Statistical analyses were performed to assess the association of the differences in IOP caused by FS-LASIK with central corneal thickness (CCT), mean corneal curvature (Km), age, refractive error correction (REC), optical zone diameter (OZD), ablation zone diameter (AZD), residual stromal bed thickness (RSB) and RSB ratio (RSB/CCT). Multiple linear regression models were constructed to explore factors influencing IOP changes.Results: All four tonometers exhibited significant differences between IOP measurements taken pre and post-surgery except for CVS-bIOP in the low to moderate myopia group (t = 1.602, p = .12). CVS-bIOP, followed by DCT-IOP, provided the best agreement between pre and post-FS-LASIK measurements with the lowest differences in IOP and the narrowest limits of agreement. The pre-post IOP differences were also significantly associated with the reduction in CCT in only GAT-IOP, ORA-IOPg, and CVS-IOP. CVS-bIOP and ORA-IOPcc were the only measurements that were not correlated with CCT, Km or age both before and after FS-LASIK.Conclusions: The biomechanically corrected bIOP from the Corvis ST provided post-FS-LASIK measurements that were in closest agreement with those obtained before surgery. In comparison, GAT-IOP, ORA-IOPg, ORA-IOPcc, and CVS-IOP appeared to be more influenced by the changes in corneal biomechanics caused by FS-LASIK.

Profile and variability of intraocular pressure after the EX-PRESS device implant / Perfil e variabilidade da pressão intraocular após implante do dispositivo EX-PRESS

Abstract Objective: The EX-PRESS device is a surgical alternative for the treatment of POAG. To describe the IOP behavior before and after the implantation of the EX-PRESS, the pharmacological treatment used in the pre and postoperative period and the complications in the first year of the postoperative period. Methods: A quantitative descriptive study with review of electronic medical records of a private ophthalmological reference hospital in Goiânia (GO) from 2013 to 2018. Sample composed of 8 eyes with POAG subjected to the EX-PRESS implant. We observed the variables: gender, age, operated eye, antiglaucomatous medications used, pre and postoperative intraocular pressure, and possible complications. Results: In the preoperative period, all eyes used antiglaucomatous drops, 75% used 3 or more different classes simultaneously. After 12 months of EX-PRESS, only 12.5% used three or more eye drops and 37.5% did not use any eye drops. On average, IOP varied from 18.63mmHg (SD 9.38) in the preoperative period to 14.50mmHg (SD 4.14) at 12 months postoperatively. Complications were: ocular hypotension, ocular hypertension; thinning of the conjunctival blister, cystic blister obstruction of the EX-PRESS. We resolved all coplications. Conclusion: The efficacy of EX-PRESS in IOP reduction was verified in the study. Concomitantly, there was a considerable decrease in anti-glaucomatous medications, and few associated complications.

Resumo Objetivo: O dispositivo EX-PRESS é uma alternativa cirúrgica para o tratamento do GPAA. Descrever o comportamento da PIO antes e após a implantação do EX-PRESS, o tratamento farmacológico utilizado no período pré e pós-operatório e as complicações no primeiro ano do pós-operatório. Métodos: Estudo descritivo quantitativo com revisão de prontuários eletrônicos de um hospital particular de referência oftalmológica de Goiânia (GO) no período de 2013 a 2018. Amostra composta por 8 olhos com GPAA submetidos ao implante de EX-PRESS. Foram observadas variáveis: sexo, idade, olho operado, medicações antiglaucomatosas usadas, pressão intraocular pré e pós-operatória, e possíveis complicações. Resultados: No pré-operatório, todos os olhos usavam colírios antiglaucomatosos, 75% faziam uso simultâneo de 3 ou mais classes diferentes. Após 12 meses do EX-PRESS, apenas 12,5% usavam três ou mais colírios e 37,5% não usavam nenhum colírio. Em média, as PIO variaram de 18,63 (DP 9,38) mmHg no pré-operatório para 14,50 (DP 4,14) mmHg em 12 meses do pós-operatório. As complicações foram: hipotensão ocular, hipertensão ocular,afinamento de bolha conjuntival, bolha cística, obstrução parcial do EX-PRESS. Conclusão: A eficácia do EX-PRESS na redução da PIO foi verificada na amostra desse estudo. Concomitantemente, constatou-se diminuição considerável de medicações anti-glaucomatosas, e poucas complicações associadas.

Comparison of Icare Pro Tonometry and Icare One Tonometry Measurements in Healthy Eyes

Objectives: To compare intraocular pressure (IOP) measurements obtained with the Icare Pro tonometer used in clinical practice and the Icare One self-tonometer. Materials and Methods: Fifty-two eyes of 52 healthy, right-handed individuals with no prior intraocular surgery or ocular trauma, structural ocular pathology, or systemic disease were evaluated. IOP was first measured using the Icare Pro tonometer. The participants were then told how to use the Icare One tonometer and asked to measure their own IOP. The results were analyzed statistically using SPSS v.24. Results: Of the 52 healthy participants, 16 (30.7%) were male and 36 (69.3%) were female. Their mean age was 31.6±6.3 (23-47) years. Mean IOP measured with the Icare Pro was 17.10±6.2 (11.5-25.2) mmHg, and the mean self-measured IOP with Icare One was 14.01±3.4 (7-24) mmHg. When the two methods were compared using Levene's t-test, there was a significant mean difference of -3.08±0.6 (95% confidence interval: -4.39 -1.78; p<0.001). Conclusion: In this study, there was a significant difference between the IOP measurements we made using the Icare Pro and the participants' self-measured IOP using the Icare One, with the latter being relatively lower. This may be related to the fact that the participants were unfamiliar with using the Icare One. Although the Icare One is a promising tool for glaucoma patients to self-monitor their IOP, further studies are needed.

Estudo comparativo entre as medidas da pressão ocular dos tonômetros de rebote, pneumático e de Goldmann / Comparative study between ocular pressure measurements made by rebot tonometer, pneumatic tonometer, Goldmann tonometry

RESUMO Objetivo: Comparar o resultado entre dois tipos de tonômetros, tendo como padrão ouro a tonometria de aplanação, relacionando com a espessura corneana e suas validações como instrumentos de rastreio populacional. Métodos: Estudo transversal comparativo, realizado com 400 olhos do ambulatório de oftalmologia da Adachi Oftalmologia, em Macapá (Amapá), entre os valores médios da pressão ocular medidos pelo tonômetro Icare®, o Tonômetro Pneumático e o Tonômetro de Aplanação de Goldmann em função da espessura corneana. Foram divididos conforme a ECC em 3 grupos. Grupo 1: 260 olhos com ECC< 530µ; grupo 2: 217 olhos com ECC entre 530µ e 590µ; e, grupo 3: 157 olhos com ECC>590µ. Resultados: A ECC média obtida na paquimetria foi de 557µ, variando de 651µ a 477µ (desvio padrão de 32.9). A PIO média obtida pela TP foi de 19,4 mmHg (com desvio padrão de 2,32); pelo Icare® foi de 16,7mmHg (desvio padrão de 2,12); e, na TAG foi de 15.5 mmHg (desvio padrão de 2,02). Para paquimetrias inferiores a 530µ e superiores a 590µ a PIOm não diferiu significativamente entre a TAG e Icare® (p = 0,232), sendo estatisticamente significativa diferença obtida para córneas com ECC entre 530 e 590 µ. A PIOm obtida pelo TP foi significativamente maior do que a pressão ocular média dos TAG e Icare® (p < 0,001 para ambos) em todos os grupos. Conclusões: Os três métodos podem ser utilizados em campanhas de rastreamento, porém o Icare® se mostrou mais confiável que a TP, com valores obtidos estatisticamente mais confiáveis quando comparados à TP. Existe suficiente concordância entre o Icare e a TAG para recomendar o seu uso.

ABSTRACT Objective: To compare the result between two types of tonometres, using as gold standard the aplanation tonometry, relating to the corneal thickness and its validations as instruments of population screening. Methods: A comparative cross-sectional study was carried out with 400 eyes from the ophthalmology clinic of Adachi Ophthalmology, in Macapá (Amapá), between the mean values of ocular pressure measured by the Icare® tonometro, the Pneumatic Tonometer and the Goldmann Flattening Tonometro as a function of corneal thickness. They were divided according to ECC in 3 groups. Group 1: 260 eyes with ECC <530µ; group 2: 217 eyes with ECC between 530µ and 590µ; and, group 3: 157 eyes with ECC> 590µ. Results: The mean ECC obtained in pachymetry was 557µ, ranging from 651µ to 477µ (standard deviation of 32.9). The mean IOP obtained by PT was 19.4 mmHg (with a standard deviation of 2.32); by Icare® was 16.7mmHg (standard deviation of 2.12); and in the TAG it was 15.5 mmHg (standard deviation of 2.02). For pachymetry less than 530µ and greater than 590µ, PIOm did not differ significantly between TAG and Icare® (p = 0.232), and a statistically significant difference was obtained for corneas with ECC between 530 and 590 µ. The IOP obtained by the PT was significantly higher than the mean ocular pressure of the TAG and Icare® (p <0.001 for both) in all groups. Conclusions: All three methods can be used in screening campaigns, but Icare® proved to be more reliable than TP, with values obtained statistically more reliable when compared to TP. There is sufficient agreement between Icare and TAG to recommend its use.

Intraocular Pressure Measurement by Rebound Tonometry (TonoVet) in Normal Pigeons (Columba livia).

We evaluated the applicability of a rebound tonometer (TonoVet) in pigeon eyes and established normal reference intraocular pressure (IOP) values in healthy pigeons; 20 eyes of euthanized pigeons were used for calibration of the TonoVet and 48 eyes of 24 adult pigeons were used for measurement of reference IOP. First, IOP of pigeon eyes ex vivo were measured using the 'd' and the 'p' modes of the TonoVet and compared to manometric IOP values from 5 to 80 mm Hg. Then, to establish normal reference values, IOP was measured from clinically normal pigeons in vivo. The 'd' and the 'p' modes of the TonoVet showed a strong linear correlation with the manometric IOP (R2 = .996 and .991, respectively). The obtained regression formulas were: y1 = 0.439x + 2.059 and y2 = 0.330x - 0.673, respectively (y1, 'd' mode of TonoVet; y2, 'p' mode of TonoVet; x, manometric IOP). The 'd' and the 'p' modes consistently measured one-half and one-third of the actual IOP, respectively. Therefore, the formula obtained through the 'd' mode was applied to obtain reference values. The calibrated IOP of normal pigeon eyes was 19.5 ± 4.4 mm Hg. The actual IOP could be calculated using the presented formula. Considering the limitations of the 'p' mode, use of the 'd' mode is more appropriate. Therefore, the TonoVet rebound tonometry under the 'd' mode is a reliable method for measuring IOP in pigeons.

The Outcomes of a Comprehensive Program for Maintenance of Goldmann Applanation Tonometer.

PRECIS: We checked 190 tonometers every month and repaired faulty ones. Calibration error (CE) frequency reduced from 23% to 0.6% at 1 year. Tonometers needing one or >1 CE repair differed in survival but not in age. PURPOSE: The purpose of this study was to report the outcomes of a comprehensive program to maintain calibration status of the Goldmann applanation tonometer. METHODS: This prospective cohort study was carried out at 2 tertiary eye care referral centers. We included 190 slit-lamp mounted Goldmann applanation tonometers (Model AT 900 C/M). Health care providers (error checking and reporting) and clinical engineers (maintenance) participated. The team carried out CE check once a month, and repair of faulty tonometers, if any, within 24 hours. Failure of tonometer was defined as development of unacceptable CE beyond the third repair. The main outcome measures were the frequency of CE and survival function of the tonometer over 1 year. RESULTS: The median age of the tonometers was 10.7 (range, 0.2 to 25.1) years. The total number of repairs was 86. The proportion (95% confidence interval) of faulty tonometers reduced from 23.1% (17.7, 29.6) in the first month to 0.6% (0.1, 3.3) at 1 year (P<0.01). The median age of the tonometer did not differ between those needing (n=63, 9.4 y) and not needing (n=127, 10.7 y; P=0.24) repair. All tonometers requiring 1 CE repair (n=49, 25.7%) survived until 1 year. The survival of tonometers requiring >1 CE repair (n=14, 7.3%) was 40% at 1 year. CONCLUSIONS: Our in-house program maintained 92.6% tonometers error free. Number of repairs rather than age determined the need for replacement/sending back the tonometer to the manufacturer. Our simple and easy to follow maintenance program has the potential for wide application.

Fluctuations of the Intraocular Pressure in Medically Versus Surgically Treated Glaucoma Patients by a Contact Lens Sensor.

PURPOSE: To compare fluctuations in intraocular pressure (IOP) in medically vs surgically treated glaucoma patients. DESIGN: Prospective, nonrandomized case series. METHODS: IOP-related fluctuations were measured for 24 hours using a contact lens sensor (CLS). SUBJECTS: We performed monitoring with CLS in 91 eyes of 77 patients; 59 eyes were receiving ocular hypotensive medication and had no previous history of glaucoma surgery (medical group), while 32 eyes with open-angle glaucoma (OAG) had previously undergone glaucoma surgery (surgical group). MAIN OUTCOME MEASURES: The amplitude, expressed as an indicator of the IOP-related fluctuation, and the presence of a nocturnal acrophase. We also identified maximum and minimum IOP-related values for each patient. RESULTS: The mean (standard deviation) amplitude of IOP-related CLS signal in the group of surgically treated eyes was 100 (41) mV eq, while in the medically treated group it was 131 (69) mV eq (difference: P = .010). We found that 42.9% of the surgically treated but only 13.8% of the medically treated glaucoma group exhibited an absence of nocturnal acrophase (difference: P = .011). The maximum and minimum IOP-related values for the medical group were statistically higher than the surgical group (P = .001 and P = .006, respectively). CONCLUSIONS: IOP-related fluctuations were larger in eyes with medically treated glaucoma than in those with surgically treated glaucoma. A significantly larger fraction of the surgical group exhibited an absence of nocturnal acrophase compared to the medically treated group.

The Effect of Therapeutic IOP-lowering Interventions on the 24-hour Ocular Dimensional Profile Recorded With a Sensing Contact Lens.

PRéCIS:: The 24-hour ocular dimensional profile recorded by a contact lens sensor was affected by intraocular pressure lowering interventions. Among different treatments, incisional surgery had the most significant effect. PURPOSE: We investigated the effect of different intraocular pressure (IOP)-lowering interventions on contact lens sensor (CLS) parameters and their relationship with Goldmann applanation tonometry (GAT)-measured IOP reduction. METHODS: Data from reliable CLS recordings performed before and after IOP-lowering interventions were analyzed. Three interventions were evaluated: topical medications, laser trabeculoplasty, and incisional surgery. A set of 115 different CLS parameters were derived from 24-hour curves. We compared before versus after values for each parameter. In addition, linear regression was performed using the percentage change of each CLS parameter as the outcome variable and the type of IOP-lowering procedure as the predictor after adjusting age and race. Finally, we investigated the relationship between changes in CLS parameters and GAT IOP with the Spearman rank correlation coefficient. RESULTS: A total of 182 eyes of 182 patients were included in the analyses: 60 (33%) topical medications, 69 (38%) laser, and 53 (29%) surgery. The mean GAT IOP change was 3.6±6.5 mm Hg (P<0.001). Overall, more CLS parameters had a significant change after surgery than in the other groups (surgery>laser=drug). Linear regression showed that, for 20 CLS parameters, surgery was the most predictive of greatest percentage change in CLS signals. In all, 11 (9.5%) of the CLS parameters were significantly correlated with GAT changes. CONCLUSIONS: Incisional glaucoma surgery had a more pronounced effect on GAT and CLS parameters than laser and drugs. The CLS can detect changes in patterns resulting from IOP-lowering interventions beyond daytime GAT IOP. This device could potentially be used to assess treatment efficacy in glaucoma.

Comparison of intraocular pressure fluctuation before and after cataract surgeries in normal-tension glaucoma patients.

PURPOSE: Cataract surgeries have been shown to reduce intraocular pressure. We used a Sensimed Triggerfish® contact lens sensor to compare intraocular pressure levels and their fluctuation between before and after cataract surgeries in patients with normal-tension glaucoma. METHODS: This was a prospective open-label study. Thirteen patients with normal-tension glaucoma were included. All patients underwent a 1-month washout and discontinued glaucoma medications during this study. In each eye, intraocular pressure fluctuations over 24 h were measured with the contact lens sensor before and at 3 months after the cataract surgery. We compared intraocular pressure levels and their fluctuation between before and after cataract surgeries. We used two approaches to evaluate the amplitude of intraocular pressure fluctuations: dual-harmonic regression analysis, and measurement of the difference between the maximum and the minimum value. RESULTS: The mean pre-operative intraocular pressure was 14.7 ± 2.2 mm Hg and mean post-operative intraocular pressure was 11.4 ± 2.2 mm Hg. Cataract surgery significantly decreased intraocular pressure (p = 0.0005). In both methods, the post-operative fluctuations in intraocular pressure over 24 h were significantly smaller than their pre-operative counterparts (dual-harmonic regression analysis: p = 0.0171; difference between the maximum and the minimum: p = 0.0398). CONCLUSION: Cataract surgery decreased both intraocular pressure values and intraocular pressure fluctuations in normal-tension glaucoma patients.

The influence of electromagnetic radiation on the measurement behaviour of the triggerfish® contact lens sensor.

BACKGROUND: To assess a possible signal drift, noise and influences of electromagnetic radiation on the measurement behaviour of the Triggerfish® contact lens sensor, which might be mistaken as IOP fluctuations. METHODS: Contact lens sensors (Triggerfish®, SENSIMED AG, Lausanne, Switzerland) were fixed in a water bath. To reduce any external electromagnetic impulses, all plugs were removed from the sockets, no lights were switched on and no electronic devices, except a temperature logger were left in the test room. For 24 h signal drift, noise and the influences of a cordless telephone (Ascom d43 DECT Handset, EU DECT 1880-1900 MHz, Ascom Wireless, Baar, Switzerland), a smartphone (Sony Xperia Go ST27i, Sony Corporation, Tokyo, Japan) and a computer (Hewlett-Packard ProBook 650 15,6″ - D9S33AV, Hewlett-Packard Inc., Palo Alto, USA) on the measuring profile were analysed. RESULTS: Twenty-four-hour measurements without provoked external electromagnetic impulses yielded a profile without any signal drift and 8.2 mV eq noise. During the activation of the cordless telephone a maximum measurement variation of 3.2 mV eq. (4.1-7.3), smartphone 1.8 mV eq. (4.7-6.5) and computer 1.4 mV eq. (6.3-7.7) were observed. CONCLUSIONS: During 24-h measurements there was no signal drift and a very low noise. Patients concerned about electronic devices possibly interfering with the measurements of the contact lens sensor, can be informed, that the use of their cordless telephone, smartphone or computer does not cause any problems. The amount of the signal noise might help to define actual IOP fluctuations. Temperature fluctuations might influence the measuring profile.

Comparison of intraocular pressure measurements between Icare PRO Tonometer, Goldmann Applanation Tonometer and non-contact tonometer in healthy and glaucomatous eyes / Comparação da medição da pressão intraocular entre o tonômetro Icare PRO, o tonômetro de aplanação de Goldmann e o tonômetro de não-contacto em olhos saudáveis e olhos glaucomatosos

Abstract Purpose: To validate the comparative measurements of intraocular pressure performed with IcarePRO tonometer (IPT) in relation to Goldmann applanation tonometer (GAT) and non-contact tonometer (NCT), as well as to evaluate the influence of central corneal thickness (CCT) on these values. Methods: This was a prospective and comparative study conducted during 6 months in the Department of Ophthalmology, Hospital de Braga, Portugal. The study population comprised two groups: healthy adults and adults with primary open angle glaucoma (POAG). The IOP values were obtained by the three tonometers and the order of execution was randomly selected. CCT values were obtained by ultrasonic pachymetry. Results: A total of 168 eyes (74 with diagnosis of POAG and 94 healthy) of 84 patients were included in this study. The mean IOP values obtained by IPT, GAT and NCT were 17.36±3.78 mmHg; 14.59±3.32 mmHg; and 17.04±4.01 mmHg, respectively. The comparison between IPT and NCT did not reveal statistically significant differences in the two groups studied. However, statistically significant differences were obtained between IPT and GAT values (p <0.001). The IOP values, recorded by all the tonometers, were significantly and positivily correlated with the CCT (p <0.001). Conclusion: IOP readings measured by IPT are comparable with those obtained by NCT, but higher than those obtained by the GAT. CCT values are correlated with IOP measurements with IPT, as it does in GAT and NCT, and should be always taken into consideration.

Resumo Objetivo: Validar os valores de pressão intraocular (IOP) realizados com o tonômetro IcarePRO (IPT) em relação ao tonômetro de aplanação de Goldmann (GAT) e tonômetro de sopro (NCP), assim como avaliar a influência da espessura central da córnea (CCT) nesses valores. Métodos: Estudo prospectivo e comparativo realizado durante 6 meses consecutivos no Departamento de Oftalmologia do Hospital de Braga, Portugal. A população estudada compreendeu dois grupos: adultos saudáveis e adultos com glaucoma primário de ângulo aberto (POAG). Os valores de IOP foram obtidos pelos três tonômetros e a ordem de execução foi selecionada aleatoriamente. Os valores de CCT foram obtidos por paquimetria ultrassônica. Resultados: Um total de 168 olhos (74 com diagnóstico de POAG e 94 saudáveis) de 84 pacientes foram incluídos neste estudo. Os valores médios de IOP obtidos pelo IPT, GAT e NCT foram de 17.36±3.78 mmHg; 14.59±3.32 mmHg; e 17.04±4.01 mmHg, respectivamente. A comparação entre IPT e NCT não revelou as diferenças estatisticamente significativas nos dois grupos estudados. No entanto, foram obtidas diferenças estatisticamente significativas entre os valores registados pelo IPT em comparação ao GAT (p <0.001). Os valores de IOP, medidos por todos os tonômetros, foram significativamente correlacionados com a CCT (p <0.001). Conclusão: As leituras de PIO medidas pelo IPT são comparáveis às obtidas pelo NCT, mas superiores às obtidas pelo GAT. Os valores de CCT estão correlacionados com medidas de IOP, tal como acontece com o GAT e NCT, pelo que devem ser levados em considerados.