Rebound Tonometer Research Articles

Home iCare – What we already know

Abstract The only known modifiable risk factor for the development and progression of glaucoma is an increased intraocular pressure (IOP). Current follow-up with Goldmann applanation tonometry (GAT) constitutes a suboptimal approach, given out-of-office IOP peaks and fluctuations will not be exposed. Self-tonometry in the home environment could address this unmet need, detecting uncontrolled disease and potentially impacting further therapeutic management. Since recently, iCare HOME was developed as a handheld rebound tonometer for this purpose. The aim of this literature review is twofold. First, the accuracy of iCare HOME compared to GAT will be assessed, including evaluation of the influence of corneal characteristics and the mean IOP. Second, an overview of the reported feasibility and acceptance on the use of iCare HOME will be presented. The literature review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines. Literature was searched on Medline (via Pubmed), Embase, Cochrane Library, and Web of Science (Core Collection) on April 10, 2023. A total of 187 records were identified after deduplication, of which 20 articles were included after full evaluation of their suitability. This study reported that iCare HOME has a moderate to good accuracy compared to GAT and a tendency to underestimate GAT, with a median underestimation of 1 mmHg, ranging from 2.66 mmHg underestimation to 2.08 mmHg overestimation. Success rates ranged between 67.5% and 100% with a median rate of 82.5%. Sufficient acceptance was demonstrated. In conclusion, self-tonometry with iCare HOME constitutes an accurate, feasible, and accepted method for home monitoring of glaucoma, providing additional out-of-office IOP-data, and increasing patient empowerment.

Short-term fluctuation of intraocular pressure and influencing factors following intravitreal injection in patients with retinal vascular diseases.

To investigate the patterns of short-term intraocular pressure (IOP) fluctuations and identify the contributing factors following intravitreal injection in patients with retinal vascular diseases. Totally 81 patients were enrolled in this case control study. Eyes were categorized into 7 groups, including age-related macular degeneration (AMD), polypoidal choroidal vasculopathy (PCV), idiopathic choroidal neovascularization (CNV), proliferative diabetic retinopathy (PDR), diabetic macular edema (DME), macular edema secondary to branch (BVOME) and central (CVOME) retinal vein occlusion. IOP was measured in all patients using rebound tonometer at 7 preset time points perioperatively. Additionally, based on the administered medication, the eyes were classified into three treatment groups, including dexamethasone intravitreal implant (IVO), intravitreal conbercept (IVC), and intravitreal ranibizumab (IVR). To compare IOP values at various time points across groups, we employed one-way ANOVA, independent sample t-test or χ 2 test and multivariate logistic regression analysis. Peak IOP values across all groups were observed at 40s, and 5min after intravitreal injection. Statistical differences in IOP were detected at the 5min among the 7 indication groups (F=2.50, P=0.029). When examing the impact of medications, the IVO group exhibited lower average IOP values at both 40s and 5min compared to the IVC and IVR groups (P<0.001; P=0.007). The IOP values at 40s and 5min were significantly higher in BVOME and CVOME group compared to non-retinal vein occlusion-secondary macular edema (RVOME) group (P<0.001). Multivariate logistic regression analysis further confirmed that IOP measurement at 40s was significantly higher in CVOME group than in non-RVOME group (OR=1.64, 95%CI: 1.09-2.47; P=0.018). Needle size plays a crucial role in the transient changes of IOP following intravitreal injection. Before administering intravitreal injection to patients with central retinal vein occlusion, it is essential to exclude any underlysing causes of increased IOP.

Knockout of TMEM206 in mice associated with a loss of corneal transparency.

To investigate the role of transmembrane protein 206 (TMEM206) in corneal edema in mice by knockout the TMEM206 gene using CRISPR/Cas9 editing technology. TMEM206-knockout mice were generated using the CRISPR-Cas9 system. Variations in ophthalmic pathology were observed using slit lamp microscope and optical coherence tomography (OCT), intraocular pressure (IOP) was measured using a TonoLab Rebound Tonometer, and the ultrastructure of the corneal was observed using a transmission electron microscope. Corneal opacity was observed in 4/18 homozygous TMEM206-/- mice whereas a similar change was not observed in heterozygous TMEM206+/- mice and wild-type littermates. OCT examination showed that the mean central cornea thickness was 125±5.4 µm in 4 homozygous TMEM206-/- mice developed corneal edema and 115±1.2 µm in wild-type mice (t=3.468, P<0.05) at 43wk. The mean IOP was 12.08±0.07 mm Hg in four right eyes with corneal edema and 12.03±0.03 mm Hg in three normal left eyes (P>0.05). Transmission electron microscopy revealed a disruption in the organization of the collagen fibrils in the central part of the cornea in homozygous TMEM206-/- mice. TMEM206 is associated with corneal edema which caused organizational disruption of collagen fibrils in corneas of mice.

The Agreement of Intraocular Pressure Measurement in Healthy Merinos Sheep Using Rebound Tonometer (Tonovet®) and Applanation Tonometer (Tono-Pen VetTM)

The assessment of intraocular pressure (IOP) holds significant importance in ophthalmology as a crucial diagnostic tool for various ocular disorders. In the realm of comparative ophthalmology research, investigating ocular examination in sheep, particularly Merinos, is of considerable interest. This study aimed to evaluate the agreement between rebound (TonoVet®, TV) and applanation (Tono-Pen Vet™, TPV) tonometers in measuring IOP in healthy Merino sheep. 155 healthy Merinos (80 males, 75 females) with a mean weight of 54.4 ± 8.7 kg, aged 24 ± 6 months, were included in the study. IOP was measured between 9:00 and 11:00 am using both the rebound and applanation tonometers. The rebound tonometer was utilized first, followed by the applanation tonometer. A total of 620 readings (310 readings per eye) were obtained from the two devices. No statistical differences were noted between the mean IOP measurements of the right and left eyes for both tonometers (P &gt; 0.05). However, there was a significant difference in the mean IOP measurements between the TV (11.8 ± 2.3 mmHg) and the TPV (13.9 ± 2.9 mmHg) tonometers (P &lt; 0.001). The concordance correlation coefficient indicated weak agreement strength (ρc = 0.319, CI 95% = -0.169 to 0.455) between the TV and TPV. The mean difference in bias and the 95% limits of agreement for the differences between TV and TPV were -2.1 mmHg (-9.0 to 3.5 mmHg). The regression equation derived from a Bland-Altman plot, describing the relationship between the two tonometers, was Y = 1.43 - 0.33X (Y = TV and X = TPV). In conclusion, the TPV measured higher IOP values compared to the TV, and due to the significant bias and limits of agreement, the two tonometers should not be used interchangeably for IOP measurement in Merino sheep.

Expanding the invertebrate medicine toolbox: evaluation of opisthosoma tonometry as a novel diagnostic tool for arachnids.

The objective of this study was to analyze the use of rebound tonometry, as a noninvasive diagnostic tool, in arachnids. 5 juvenile (yearling) female and 1 juvenile male curlyhair tarantulas (Tliltocatl albopilosus, previously Brachypelma albopilosum) were used to track estimated ventral opisthosoma pressures over a 9-month period of time. Younger, growing animals were selected as they are more likely than adults to go through multiple molts throughout the 9 months of the study length. An iCare TONOVET TV01 rebound tonometer was used to measure the estimated ventral opisthosoma pressures of the spiders. Measurements were obtained from the ventral opisthosoma, 1 of the thinnest areas of exocuticle throughout the body. Readings were obtained once per week from the ventral opisthosoma for the first 2 months, then once every 2 weeks for 1 month, then back to once per week for the remainder of the study. Additional measurements were obtained following each ecdysis, after a 2% body weight sampling of hemolymph, and at the end of the study to evaluate readings in response to induction of general anesthesia with 5% isoflurane gas and oxygen flow at 2 L/min for 10 minutes. The average of all estimated ventral opisthosoma pressure when spiders were not in molt was 26.19 mm Hg (SD, 3.54), with a statistically significant decrease postmolt to an average of 15.31 mm Hg (SD, 3.81), followed by a gradual increase back to premolt pressures over a 3-week period with an average of 22 days (SD, 1.93). Estimated ventral opisthosoma pressures decreased post hemolymph removal. There is not sufficient evidence that estimated ventral opisthosoma pressures changed over time following the anesthesia. This study demonstrates that tonometry can be used to generally assess the estimated ventral opisthosoma pressure, which could correlate with where a spider is in an ecdysis cycle.

Exploring the Impact of Blood Draws on the Intraocular Pressure of Older Adults: A Focus on Physiological Responses.

Background/Objectives: This study investigated intraocular pressure (IOP) changes after a blood draw in older adults considering sex, age, and baseline IOP. Methods: Fifty-three subjects (54.7% females; age: 68.50 ± 4.46 years; Visual Function Index [VF14]: 94.50 ± 7.50 points; mean contrast sensitivity function (CSF) for both eyes in each spatial frequency [cdp]: 1.5 cdp [1.41 ± 0.20 log], 3 cdp [1.57 ± 0.29 log], 6 cdp [1.45 ± 0.39 log], 12 cdp [1.04 ± 0.40 log], 18 cdp [0.63 ± 0.31 log]) voluntarily participated. Subjects fasted for at least 8 h before attending the laboratory. First, IOP was measured in a seated position using a portable rebound tonometer. Ten minutes after the initial measurement, two 10 mL tubes of blood were drawn. Five minutes after the blood draw IOP was measured again following the same procedure as the initial measurement. We evaluated the differences using an analysis of variance. Results: Significant, but not clinically relevant, decreases were found in the right eye, with small effect sizes (p = 0.013-0.079, d = 0.35). Only males and subjects older than 68 years showed trends toward IOP reduction in the right eye. Subjects with baseline IOP ≥ 14 mmHg experienced significant IOP reductions in both eyes, with moderate effect sizes (p = 0.001-0.002, d = 0.56-0.69). Conclusions: Our findings suggest that a blood draw of 20 mL is safe for the IOP levels of older adults with baseline IOP between 11 and 21 mmHg. Variations in IOP were observed based on baseline IOP, sex, and age, suggesting the importance of personalized clinical assessments. The primary factor influencing IOP changes appears to be the baseline IOP level.

Association between Risk of Obstructive Sleep Apnea and Intraocular Pressure based on the Korea National Health and Nutrition Examination Survey VIII.

A higher STOP-BANG score and loud snoring, observed breathing interruptions during sleep, hypertension, and wide neck circumference were individually and in combination associated with high intraocular pressure in Koreans aged 40 years and older. To evaluate the relationship between intraocular pressure (IOP) and the risk of obstructive sleep apnea (OSA). In this population-based, cross-sectional study, we included Korean adults aged 40 years or above recruited between 2019 and 2021. 6315 subjects were included from the Korea National Health and Nutrition Examination Survey Ⅷ database. The risk of OSA was measured by STOP-BANG questionnaire. The IOPs were measured using rebound tonometer. Logistic regression was used to analyze the association between IOP quartiles (highest quartile vs. lower 1-3rd quartiles) with OSA risk after adjusting for sociodemographic characteristics, lifestyle, and diabetes. The adjusted odds ratio for high IOP, was 1.27 (95% CI 1.12 to 1.43) for participants with a STOP-BANG score of 3 to 8 compared with those with a score of 0 to 2. Participants with loud snoring, observed breathing interruptions during sleep, hypertension, or wide neck circumference had 24%-40% higher odds of high IOP than those without these components. The odds ratio for high IOP in the group with all four factors was 2.09 times higher (95% CI 1.26 to 3.46) than in the group without these factors. A higher STOP-BANG score was associated with an increased risk of high IOP in Koreans aged 40 years and older. Furthermore, among the STOP-BANG components, loud snoring, observed breathing interruptions during sleep, hypertension, and wide neck circumference were individually and in combination associated with high IOP.

The Effects of Pregnancy Status on Lacrimal Caruncle Temperature, Intraocular Pressure and Rectal Temperature in Cats: A Preliminary Study.

The objectives of this study were to compare the body temperatures between pregnant and nonpregnant cats from two sites, lacrimal caruncle temperature (LCT) and rectal temperature (RT), and to compare intraocular pressure (IOP) between pregnant and nonpregnant cats. This study was performed on 13 pregnant and 16 anoestrous cats. The gestation period of the pregnant cats ranged from 20 to 45 days. A vaginal smear was also performed to determine the sexual cycles of nonpregnant cats. The IOP was measured using a rebound tonometer. The pregnant cats (38 ± 0.7°C) exhibited a lower RT than the nonpregnant cats (38.5 ± 0.5°C) (p < 0.05). No significant differences existed between the pregnant and nonpregnant groups in the right (R)-LCT or left (L)-LCT (p > 0.05). The average LCT temperature measured 32.30 ± 2.23°C in cats. The right (R)-IOP in pregnant cats (17.69 ± 5.6mm Hg) was significantly lower than in nonpregnant cats (22.37 ± 5.27mm Hg) (p < 0.029). Pregnant cats exhibited a significantly lower left (L)-IOP value (17.69 ± 5.76mm Hg) compared to nonpregnant cats (23.18 ± 5.55mm Hg) (p < 0.015). This study presents a preliminary report that documents a noteworthy reduction in RT in pregnant cats (38 ± 0.7°C) as compared to cats in anoestrus. Pregnancy also has an effect on the IOP. It was hypothesised that the hormonal changes induced by pregnancy in cats would have a substantial impact on IOP and RT. Although body temperature can be measured using LCT, RT should still be utilised as the reference measurement site.

The impact of different postures on acute intraocular pressure and accommodation responses during reading

IntroductionTo investigate the effects of different reading postures on intraocular pressure (IOP) and near-work-induced transient myopia (NITM) in children with myopia.MethodsSixty myopic children were instructed to read a book text placed at 33 cm for 30 min with two different reading postures: head bowed and head upright postures. The participants’ IOP and NITM were assessed using a rebound tonometer and an open-field autorefractor. The measurement of IOP was conducted prior to reading, during reading sessions (at 5, 10, 20, and 30-min intervals), and after a 5-min recovery period.ResultsFor the head bowed posture, the mean baseline IOP was 16.13 ± 2.47 mmHg. A significant rise in IOP was observed after 5 min of reading (17.17 ± 2.97 mmHg; +1.03 ± 2.29 mmHg; p = 0.014). Subsequent measurements revealed a further increase after 20 min (17.87 ± 2.90 mmHg; +1.73 ± 2.58 mmHg; p < 0.001), which continued to persist even after 30 min of reading (17.57 ± 3.46 mmHg; +1.43 ± 2.66 mmHg; p = 0.002). The IOP at different time points measured in the head upright posture did not show any significant difference in comparison to the baseline measurement (all p = 1.000). Compared to reading with the head upright, reading with the head bowed resulted in a greater increase in IOP at each time point (p < 0.05). Furthermore, the NITM was higher for reading with the head bowed than for reading with head upright at 30 min (-0.24 ± 0.53 D vs. -0.12 ± 0.47 D, p = 0.038).ConclusionReading in a head bowed position resulted in greater increases in IOP and NITM compared to reading in a head upright posture.

Effects of Phenylcapsaicin on Intraocular and Ocular Perfusion Pressure During a 30-Min Cycling Task: A Placebo-Controlled, Triple-Blind, Balanced Crossover Study.

The main objective of this placebo-controlled, triple-blind, balanced crossover study was to assess the acute effects of phenylcapsaicin (PC) intake (2.5mg) on intraocular pressure (IOP), ocular perfusion pressure (OPP), and heart rate (HR) during a 30-min cycling task performed at 15% of the individual maximal power. Twenty-two healthy young adults performed the cycling task 45min after ingesting PC or placebo. IOP was measured with a rebound tonometer before exercise, during cycling (every 6min), and after 5 and 10min of recovery. OPP was assessed before and after exercise. HR was monitored throughout the cycling task. We found an acute increase of IOP levels related to PC consumption while cycling (mean difference = 1.91 ± 2.24mmHg; p = .007, ηp2=.30), whereas no differences were observed for OPP levels between the PC and placebo conditions (mean difference = 1.33 ± 8.70mmHg; p = .608). Mean HR values were higher after PC in comparison with placebo intake (mean difference = 3.11 ± 15.87 bpm, p = .019, ηp2=.24), whereas maximum HR did not differ between both experimental conditions (p = .199). These findings suggest that PC intake before exercise should be avoided when reducing IOP levels is desired (e.g.,glaucoma patients or those at risk). Future studies should determine the effects of different ergogenic aids on IOP and OPP levels with other exercise configurations and in the long term.

Relationship between hyperglycemia and intraocular pressure, corneal biomechanics, and corneal topography during the oral glucose tolerance test in nondiabetic patients.

Altered corneal biomechanics in patients with diabetes may affect intraocular pressure (IOP) measurements. Although a relationship between IOP and glucose levels has been reported in diabetic and nondiabetic patients, the mechanism by which hyperglycemia influences IOP is unclear. The aim of this study was to determine the effects of hyperglycemia on IOP, corneal biomechanics, and anterior segment parameters during the oral glucose tolerance test (OGTT) in nondiabetic patients. Twenty-one patients without DM who underwent OGTT were included in this study. A complete ophthalmologic examination was performed before the test. Blood glucose, insulin level, IOP (iCare rebound tonometer), Ocular Response Analyzer, and corneal topography (Pentacam) measurements were obtained at 0, 1, and 2h during the OGTT. Data from the patients' right eyes were included in the analysis. The mean age of the patients was 46.9 ± 11.0years. There was a statistically significant difference in IOP between 1 and 2h (p = 0.03) and a clinically significant difference between 0 and 1h (p = 0.06). Corneal resistance factor was lower at 2h than 1h (p = 0.03), while central cornea thickness was increased at 1h (p = 0.01) and 2h (p = 0.05) compared to 0h. There was positive partial correlation between hyperglycemia and IOP at 1h (p = 0.049, r = 0.67). The positive partial correlation between IOP and glucose level suggests that acute hyperglycemia may lead to increased IOP. However, further research is needed to explain the mechanism of IOP elevation in the hyperglycemic phase during OGTT.

Exploring the Link Between Intraocular Pressure and Central Corneal Thickness, as Well as the Diurnal Variation of Intraocular Pressure, in the Elderly Population of North Karnataka.

Purpose The study aimed to understand the relationship between intraocular pressure (IOP) and central corneal thickness (CCT) in older adults living in North Karnataka and the diurnal variation of IOP in the elderly population. Methods This is a population-based cross-sectional study in which 84 eyes of 42 study participants aged over 50 years were examined. A complete ophthalmic examination was done for all subjects. IOPwas measured with an iCare IC100 (Icare Finland Oy, Vantaa, Finland) rebound tonometer and CCTwith an ultrasound pachymeter. Statistical significance was accepted as p<0.05. Results The mean age of the study participants was 64.42±6.917 years. The mean IOP and CCT at 1 pm were 12.4±2.576 and 509.24±25.379 in the right eye, and 12.45±2.319 and 511.05±24.464 in the left eye. Spearman's correlation showed that IOP was positively correlated with CCT, with p<0.05. This showed that CCT has the most significant impact on IOP. In our study, the diurnal variation of IOP by paired samples t-test was also crucial in the elderly population, with p<0.05. Conclusion In this study, IOP was reduced as the CCT was reduced, and vice versa, i.e., IOP was positively correlated with CCT. The diurnal variation of IOP in older people was the same as in the young and middle-aged population, i.e., the highest recording of IOP was in the morning, and it gradually reduced as the day passed.

Intraocular pressure before and after capsulorhexis using two viscoelastic substances and two surgical approaches in enucleated porcine eyes.

To investigate the influence of ophthalmic viscoelastic devices (OVDs) and different surgical approaches on the intraocular pressure (IOP) before and after creation of the curvilinear circular capsulorhexis (CCC) as a measure for anterior chamber stability during this maneuver. Prospective experimental WetLab study carried out on enucleated porcine eyes. IOP was measured before and after CCC with the iCare Rebound tonometer (iCare ic200; iCare Finland Oy, Vantaa, Finland). The OVDs used were a cohesive one [Z-Hyalin, Carl Zeiss Meditec AG, Germany; hyaluronic acid (HA)] and a dispersive [Z-Celcoat, Carl Zeiss Meditec AG, Germany; hydroxy propylmethylcellulosis (HPMC)]. The CCC was created using Utrata forceps or 23 g microforceps in different combinations with the OVDs. Using the Utrata forceps the IOP dropped from 63.65±6.44 to 11.25±3.63 mm Hg during the CCC. The use of different OVDs made no difference. Using the 23 g microforceps the IOP dropped from 65.35±8.15 to 36.55±6.09 mm Hg. The difference between IOP drop using either Utrata forceps or 23 g microforceps was highly significant regardless of the OVD used. Using the sideport for the creation of the capsulorhexis leads to a lesser drop in IOP during this maneuver compared to the main incision in enucleated porcine eyes. The use of different OVD has no significant influence on IOP drop.

Agreement of tonometer for measuring intraocular pressure in Wistar rats: a systematic review

Glaucoma is the most common cause of irreversible blindness in the world. It is associated with elevated intraocular pressure (IOP). Fluctuations in tonometer readings have implications for glaucoma research, where accurate IOP measurements are vital for evaluating disease progression and treatment efficacy. Researchers should carefully select the appropriate tonometer and consider biases associated with different tonometers. Validation against standard measurements can improve IOP measurement accuracy in rat models. In conclusion, this systematic review will emphasize on the importance of selecting the appropriate tonometer for IOP measurement in rat models, considering potential biases and their implications for glaucoma research. Accurate and consistent IOP measurement in rat models is crucial for understanding glaucoma pathophysiology and developing effective treatments. This systematic review aims to assess agreement among tonometers used for measuring IOP in Wistar rat models primarily focusing on TonoLab, TonoVet, and Tono-pen. The review was conducted using PRISMA guidelines. Two articles were included for qualitative synthesis. The studies compared manometric IOP with TonoLab, rebound tonometer, and Tono-pen XL readings. It was observed that TonoLab consistently underestimated IOP, while Tono-pen XL tended to overestimate IOP compared to manometric measurements. The study’s findings will help researchers in making decisions about tonometer selection, leading to more reliable outcomes in glaucoma research using rat models. Further research, specifically RCT’s (randomized controlled trial) is needed to confirm the results and enhance IOP measurement precision in rat models.

Comparing the intraocular pressure values obtained with a rebound tonometer (TONOVET Plus) and an indentation tonometer (IOPvet) in dogs with and without ocular disease.

This study aimed to compare the intraocular pressure (IOP) values obtained from two groups of dogs using the IOPvet indentation tonometer to those obtained from the same dogs using an established rebound tonometer (TONOVET Plus). Tonometry was performed on 36 dogs with ocular diseases (70 eyes; group A) and 25 healthy dogs (49 eyes; group B). First, the TONOVET Plus rebound tonometer was used. Then, one drop of oxybuprocaine hydrochloride was applied to each eye, and 1 minute later, the IOP was estimated using the IOPvet. The IOPvet was safe, well tolerated and easy to use. The instrument had a high specificity (98.5%) for identifying IOPs of 20mmHg or less. A lack of sensitivity (67.9%) was noted when evaluating eyes with an IOP between 20 and 30mmHg. The sensitivity (33.3%) for identifying canine eyes with an IOP of greater than 30mmHg (n = 24) was low. This study lacks manometric work, which would be hard to justify with client-owned dogs. Quantitative numerical data were compared with qualitative values and the same investigator obtained readings using both tonometers without being masked. The IOPvet is highly sensitive for assessing normal IOPs, but underestimation of higher IOPs can lead to poor diagnostics. Digital tonometers remain the best way to assess IOP in veterinary clinics.

A comparison of intraocular pressure measurement using SUOER SW-500 rebound tonometer and conventional reusable Goldmann prisms

A comparison of intraocular pressure measurement using SUOER SW-500 rebound tonometer and conventional reusable Goldmann prisms

IL-17A enhances the inflammatory response of glaucoma through Act1/TRAF6/NF-κB pathway

ObjectivesTo investigate the possible roles of Interleukin 17A (IL-17A) and IL-17A neutralizing antibodies (IL-17Ab) in glaucoma and the potential mechanisms. MethodsThe two glaucoma animal models, chronic ocular hypertension (COH) and N-methyl-D-aspartate (NMDA)-induced retinal ganglion cell (RGC) damage, were established and treated with intravitreal injection of IL-17A or IL-17Ab. Intraocular pressure (IOP) was measured by a rebound tonometer. The retina and RGC injury were evaluated by HE staining, TUNLE assay and Brn3a immunofluorescence staining. The frequency of IL-17A+CD4+T cells in peripheral blood was detected by flow cytometry. The expression of glial fibrillary acidic protein (GFAP) was detected by immunofluorescence staining, Western Blot and qPCR in retina. The RNA and protein expression of Act1/TRAF6/NF-κB were detected by Western Blot and qPCR in retina. ResultsThe expression of IL-17A increased in glaucoma models. After intravitreal injection of IL-17A, in the retina, the number of RGCs decreased, the apoptosis of RGCs increased, the Müller cell gliosis was more obvious. In addition, peripheral inflammation aggravated. Whereas the intravitreal injection of IL-17Ab alleviated the relevant manifestations and peripheral inflammation, reduced the gliosis of Müller cells. In the COH model, IOP increased after the injection of IL-17A, while the intravitreal injection of IL-17Ab led to a decrease in IOP. Furthermore, IL-17A promotes the apoptosis of RGCs by binding to IL-17A receptor, activating Act1/TRAF6/NF-κB pathways. ConclusionIL-17A plays a role in and aggravates RGC damage in glaucoma. IL-17Ab can neutralize the pro-inflammatory effect of IL-17A and have a protective function in glaucoma. These findings reveal the importance of IL-17A in the pathogenesis of glaucoma, which will shed light on a novel direction for the prevention and treatment of glaucoma, and also provide a reference for further research on other retinal diseases.

Test-Retest Reliability of Intraocular Pressure Measurements With Office-Based Versus Home-Based Rebound Tonometers.

Intraocular pressure (IOP) measurements obtained with the HOME2 rebound tonometer are interchangeable with measurements obtained using the office-based IC100 and IC200 rebound tonometers, making characterization of circadian IOP achievable with no inter-device sources of variability. To evaluate test-retest reliability between IOP measurements obtained with a home rebound tonometer operated by patients and those obtained with office rebound tonometers operated by experienced clinical staff. After training and practice with a home rebound tonometer (iCare HOME2) in a randomly selected eye, patients with established or suspected open angle glaucoma underwent IOP measurement in the fellow eye as follows in randomized order: 3 good quality measurements with the iCare IC100 operated by experienced clinical staff, 3 good quality measurements with the iCare IC200 operated by experienced clinical staff, and 3 good quality measurements with the HOME2 operated by the patient. The Shrout-Fleisch intraclass correlation coefficient (ICC; 2,1) was the measure of reliability utilized based on the model using 2-way random effects, absolute agreement, and single measurement. Thirty eyes of 30 patients were evaluated. The Pearson correlation coefficient ( r ) for IOP measurements taken with the IC100 and HOME2 was 0.97, with the IC200 and HOME2 was 0.96, and with the IC100 and IC200 was 0.97. Test-retest reliability between HOME2 and IC100 (ICC: 0.90), HOME2 and IC200 (ICC: 0.92), and IC100 and IC200 (ICC: 0.94) all reflected excellent test-retest reliability. The test-retest reliability of IOP measurements taken by patients using the iCare HOME2 self-tonometer compared with IOP measurements taken by trained operators using the iCare IC100 and IC200 tonometers was uniformly excellent (ICCs all ≥0.9). These findings indicate that these three devices should be considered interchangeable for the clinical assessment of circadian IOP.

Effects of alfaxalone, medetomidine, and xylazine on intraocular pressure in domestic pigeons (Columba livia domestica).

To evaluate the effects of alfaxalone, medetomidine, and xylazine on intraocular pressure (IOP) in domestic pigeons (Columba livia domestica). Eight 12-month-old pigeons (16 eyes). The pigeons were randomly assigned to three treatment groups (10 mg/kg of alfaxalone, 0.2 mg/kg of medetomidine, or 10 mg/kg of xylazine) with a 7-day washout period. The IOP was measured using a rebound tonometer and calibrated using the formula y = 0.439x + 2.059, where y is the tonometric IOP and x is the actual IOP. All three drugs significantly reduced IOP. Alfaxalone led to the least reduction at 5.2 mm Hg, medetomidine reduced IOP to 12.5 mm Hg, whereas xylazine resulted in the greatest reduction at 15.3 mm Hg. Alfaxalone achieved its maximum IOP reduction in 6 min, whereas medetomidine and xylazine required 95 and 115 min, respectively. Both alpha-2 agonists, medetomidine, and xylazine, showed a prolonged duration of effect and a greater reduction in IOP than those of alfaxalone. All three medications provided adequate sedation without any discernible adverse effects. The findings revealed the varied effects of these drugs on IOP in pigeons, potentially providing valuable insights that could be useful for broader applications in veterinary medicine.

Tonometry Through Time

The significance of intraocular pressure (IOP) was first noted in the 10th century. Instrumentation to measure IOP was first developed in the 19th century and has continued to develop over time. We now have anesthetics to aid in measuring intraocular pressure by indentation, applanation, or a combination of both indentation and applanation. In addition, non-contact and rebound tonometers are available and require no anesthetic. This article discusses the development, design and use of these instruments over a historical timeline.