Intraocular Pressure Readings Research Articles

Anterior Chamber Air Bubble Dynamics With Decreases in Atmospheric Pressure.

To evaluate the effect of decreasing barometric pressure on intracameral bubble size and intraocular pressure (IOP) in eyes with varying air fills in the anterior chamber. A total of 36 human donor eyes received 30%, 50%, or 90% anterior chamber air fill. The eyes were subjected to decreases in atmospheric pressure down to 750 hPa, equal to 2400 m in altitude, and were repeatedly imaged using anterior segment OCT while IOP was measured continuously. Eyes with 30% air fill initially showed moderate increases in IOP yet rising to an average of 30.83 mm Hg at 850 hPa (mimicking 1400 m altitude) and 42.08 mm Hg at 750 hPa. Eyes with larger air bubbles showed more acute increases in IOP with increases to an average of 47.25 mm Hg in eyes with 50% air fill at 850 hPa and 63.33 mm Hg at 750 hPa. In eyes with 90% air fill in the anterior chamber, IOP readings with an average of 113.42 mm Hg were observed already at 850 hPa, at which point additional pressure reduction was not performed. While severe increases in IOP were observed with decreased atmospheric pressure in eyes with large air bubbles in the anterior chamber, small and moderately sized bubbles seem to allow for travel over modest changes in altitude.

A comparison of iCare and Goldmann applanation tonometry measurements during the COVID-19 pandemic: a retrospective study

PurposeTo evaluate factors associated with differences in intraocular pressure (IOP) readings between iCare and Goldmann applanation tonometry (GAT) in established glaucoma patients.MethodsThis retrospective comparative study included clinical data of 350 eyes from 350 established glaucoma patients who had iCare and GAT IOP measured by an ophthalmic technician and a glaucoma specialist, respectively. The main outcome measure was the difference in IOP measurements of the right eyes with iCare and GAT.ResultsThe intraclass correlation coefficient (ICC) between GAT and iCare was 0.90. The mean IOP difference between tonometers was − 0.18 ± 2.89 mmHg. Bland–Altman plots indicated a 95% limit of agreement of − 5.8 to 5.5 mmHg. Central corneal thickness (CCT) and age were significantly correlated with the difference in IOPs of the iCare and GAT. GAT-IOP and age were significantly associated with the absolute difference in measured IOP of the two tonometers. The difference in measurements was not significantly associated with prior glaucoma surgery, average global index of optical coherence tomography, axial length, technician years of experience and certification, and IOP range.ConclusionAlthough there is good agreement between the iCare and GAT mean values, these devices are not interchangeable in glaucoma patients due to the wide range of the limit of agreement.

Validation of intraocular pressure measurement using tonometer AVIA across different postures: A Bland Altman analysis.

Tonometry is a fundamental procedure in the diagnosis and management of glaucoma. Different tonometers have been proposed but none are as accurate as the Goldman applanation tonometry (GAT). Nonetheless, due to the limitations of GAT, mobile tonometry methods became prevalent. This study aims to examine the reliability of the Tono-Pen AVIA® (TPA) in measuring intraocular pressure (IOP) across different postures. A total of 196 eyes were prospectively examined for IOP changes using GAT and TPA. IOP measurements were taken across different postures using the TPA. Reliability of measurements was compared using interclass correlation coefficients (ICC), while agreement was represented using Bland-Altman analysis. Pearson r coefficient was used to measure correlations. When compared to GAT (14.5 ± 4.4 mmHg), IOP readings were significantly higher for TPA at both seated (16.5 ± 4.5 mmHg; p < 0.001) and supine (16.9 ± 5.7; p < 0.001) positions. The ICC values for GAT and TPA among seated and supine patients were 0.79 (0.54-0.90) and 0.76 (0.48-0.87) indicating good reliability between the readings. There were significantly positive correlations between GAT and TPA at both seated (r = 0.626, p < 0.001) and supine (r = 0.727, p < 0.001) positions. Per Bland-Altman analysis, limits of agreement were -8.57 to 4.37 for GAT and seated TPA and -10.34 and 5.34 for GAT and supine TPA. Good reliability exists between IOP measurements using GAT and TPA. However, the devices are not interchangeable and therefore cannot be used reciprocally in the same patient.

Phospholipid Free Nano-Vesicles of Brinzolamide Biopolymer Ocular Insert; Design, In vitro and In vivo Evaluation

The aim of this work to study the feasibility of using phospholipid free vesicles with positive charge inducer in a slowly dissolving polymer ocular insert to successfully control intraocular pressure (IOP) for an extended period. Brinzolamide (BRNZ) was chosen as a model drug and a full factorial design was assembled to investigate the drug loading effect, ratio of cholesterol to fatty moiety and the type of the fatty moiety used on the vesicle size and entrapment efficiency. Linear regression models were constructed, and optimization of the formulation compositions yielded two formulae with palmitic acid as a negatively charged vesicles and cetrimide positively charged vesicles. Both formulae were studied in term of permeation efficiency through bovine corneal membranes. Positively charged vesicles although it didn't achieve the highest flux and cumulative amount permeated per unit surface area in the experiment time course, it achieved the highest retention of drug inside the corneal tissue, so it was chosen to be incorporated in a slowly dissolving polymer ocular insert. The insert was evaluated in term content, physical evaluation, and release properties. In vivo evaluation of the casted ocular inserts was conducted in male albino rabbits against market eye drop product and IOP readings were collected for 48 hours. The positively charged sterosomes containing BRNZ and formulated in polymer ocular inserts achieved extended control of IOP of the test animals compared to the market product.

Comparison of Tonovet® and Tonovet plus® tonometers for measuring intraocular pressure in dogs, cats, horses, cattle, and sheep.

Reference ranges for intraocular pressure (IOP) in healthy animals are device-specific; therefore, it is strongly recommended to use appropriate reference values according to the device. Therefore, our aim was to compare IOP readings made by TonoVet® and TonoVet Plus® in healthy dogs, cats, sheep, cattle, and horses. We compared IOP values measured by TonoVet® and TonoVet Plus® tonometers in clinically normal eyes of dogs, cats, horses, cattle, and sheep. Five groups comprising 20 animals each of dogs (various breeds, 9 months-10 years old, 14 females, 6 males), cats (various breeds, 6 months-12 years old, 8 females, 12 males), horses (various breeds, 5-12 years old, 12 females, 8 males), cattle (Holstein, 1-7 lactation, female), and sheep (Latvian Darkhead ewes, 1-8 years old) were included in the study. Both eyes of all animals were subjected to ophthalmic examination, including evaluation of IOP by rebound tonometry using TonoVet® and TonoVet Plus® devices. Normality was determined using the Shapiro-Wilk test. The independent t-test was used to determine differences between IOP values in the right and left eyes and between both tonometers. This study was approved by the Ethical Commission of the Latvia University of Life Sciences and Technologies (Nr. LLU_Dzaep_2022-2-4). No differences in IOP between the right and left eyes were found in all cases (p > 0.05). The mean IOP ± standard deviation values in both eyes for TonoVet® and TonoVet Plus® tonometers were as follows: for dogs, 15.25 ± 2.73 mmHg and 19.65 ± 3.46 mmHg; and in cats, 18.88 ± 3.98 mmHg and 18.78 ± 4.26 mmHg, respectively. In horses, mean IOP was 22.15 ± 3.74 mmHg and 24.28 ± 3.00 mmHg; in cattle, 24.73 ± 2.89 mmHg and 23.28 ± 2.97 mmHg; and in sheep, 18.05 ± 3.54 mmHg and 22.49 ± 4.66 mmHg, respectively. Significant differences in IOP values were observed between the tonometers in sheep, dog, and horse groups (mean difference -4.40, -4.48, and 2.13, respectively). This study showed significantly higher IOP values measured by the TonoVet Plus® tonometer in dogs and sheep.

Correlation of diurnal fluctuations in intraocular pressure and progression of chronic simple glaucoma

Purpose: To study the correlation between diurnal fluctuations of intraocular pressure and progression of chronic simple glaucoma. Introduction: Out of all the risk factors for glaucoma, only modifiable risk factor is intraocular pressure. A lot of studies have been done to determine the relationship between the behavior of diurnal intraocular pressure (IOP) and progression of glaucoma. The results varied and are inconclusive because the visual field damage could have occurred at a time when the IOP was high, although it was low at the time of measurement. Materials and Methods: A prospective study was conducted on all patients diagnosed or suspected CSG with office IOP &lt;25 mmHg. Measurement of diurnal fluctuation in IOP was done by taking 2 hourly IOP readings after admitting patients in hospital for 1 day. Results: The mean baseline diurnal fluctuation of our patients was 8.5 mmHg with values reaching as high as 13.6 mmHg in some patients. 28.8% of the patients of our study group showed progression at the end of 2-year follow-up. As the baseline diurnal fluctuation increased, the number of patients showing progression increased.

Determination of intraocular pressure and Schirmer tear test and the comparison between the applanation tonometer (Tono-Pen AVIA®) and the rebound tonometer (TonoVet Plus®) in mini lionhead rabbits.

To determine intraocular pressure (IOP) and tear production, as well as to compare the IOP obtained with the TonoVet Plus® (rebound) with the Tono-Pen Avia® (applanation) tonometers. Twenty-five Mini Lionhead rabbits (n = 50 eyes). Tear production was measured at 6:00 a.m. and 6:00 p.m. by using the STT. The IOP reading was performed with the rebound tonometer, followed by the applanation tonometer, at 6:00 a.m., 9:00 a.m., 12:00 p.m., 3:00 p.m., and 6:00 p.m. Regression analysis, analysis of variance (anova) and Bland-Altman statistics were used. Daily tear production was 10.25 ± 3.75 mm/min, with no differences among the moments evaluated. Average daily IOP was 17.7 ± 3.08 mmHg with the TonoVet Plus® and 11.5 ± 4.56 mmHg with the Tono-Pen Avia®. IOP values were higher at the beginning and end of the day with both tonometers. The IOP values are higher with the TonoVet Plus® tonometer. The reference values of IOP and tear production obtained in this work may support the diagnosis, treatment, and monitoring of ocular disorders in pet Mini Lionhead rabbits.

Intraocular pressure and its determinants in a very old population. The ural very old study

Aims/Purpose: To assess the distribution of intraocular pressure (IOP) and its determinants in a very old population.Methods: The population‐based Ural Very Old Study (UVOS) was performed in a rural and urban region of Bashkortostan/Russia and consisted of 1526 (81.1%) out of 1882 eligible individuals aged 85+ years. As part of a series of medical and ophthalmological examinations, we measured IOP by non‐contact tonometry.Results: The study included 1042 (68.3%) individuals with available IOP readings (mean age:88.1 ± 2.7 years). After excluding individuals with anti‐glaucomatous therapy, mean IOP was 14.5 ± 5.1 mmHg (median:14 mmHg; 95%CI:8,25) with a right‐sided skewed distribution. In multivariable analysis, higher IOP was associated (correlation coefficient r:0.38) with female sex (beta:0.13; p = 0.002), thinner central cornea thickness (beta:0.23; p &lt; 0.001), higher systolic blood pressure (beta:0.13; p = 0.006), higher estimated cerebrospinal fluid pressure (CSFP) (beta:0.11; p = 0.04), longer axial length (beta:0.09; p = 0.02), and status after cataract surgery (beta:‐0.17; p &lt; 0.001). In that model, the IOP measurements increased by 0.02 mmHg (95%CI:0.01,0.03) for each increase in systolic blood pressure by 1 mmHg, by 0.11 mmHg (95%CI:0.004,0.22) for each increase in estimated CSFP by 1 mmHg, by 0.2 mmHg (95%CI:0.1,0.3) for each central corneal thickness increase by 10 μm, and by 0.31 mmHg (95%CI:0.05,0.59) for each axial length increase by 1 mm. It decreased by 1.13 mmHg (95%CI:0.54,1.72) with cataract surgery.Conclusions: In this study population aged 85 + years, corneal thickness‐adjusted IOP‐readings increased with higher blood pressure and estimated CSFP and longer axial length, and it decreased with cataract surgery.

Comparative study of recording intraocular pressure in adults by three different tonometers Goldmann applanation tonometer, noncontact tonometer, and tonopen

Purpose To compare and correlate the intraocular pressure (IOP) measurement obtained by Goldmann applanation tonometer (GAT), noncontact tonometer (NCT), and tonopen in normal and glaucomatous patients. Patients and methods A cross-sectional, observational, and comparative study was carried out. Two hundred eyes of 100 patients were screened, detailed history was taken, and thorough ocular examination was done. IOP was recorded using NCT (Keeler Pulsair), Tonopen (Tonopen XL), and GAT. Gonioscopy, optic disc examination, central corneal thickness, and visual field testing were done. Results The mean age of the study group was 53.25 years. Mean IOP by NCT was 19.20 mmHg, by GAT was 22.44 mmHg, and by tonopen was 19.33 mmHg. There was statistically significant difference between mean IOP with respect to method used (P&lt;0.001). Forty-eight percent of eyes, 40% eyes, and 49% eyes had IOP less than 18 mmHg by NCT, GAT, and tonopen, respectively. In total, 35.5% eyes, 19.5% eyes, and 35.5% eyes had IOP ranging between 18 and 25 mmHg by NCT, GAT, and tonopen, respectively. In total, 16.5% eyes, 40.5% eyes, and 15.5% eyes had IOP more than 25 mmHg by NCT, GAT, and tonopen, respectively. Conclusion NCT and tonopen readings correlate well with GAT readings in physiologic IOP range up to 20 mmHg, but at higher IOP range they tend to underestimate IOP readings as compared with GAT. However, NCT and tonopen can be used for screening purpose as they are portable and easy to use.

Accuracy of Icare Rebound Tonometer and Its Comparison with Goldman Applanation Tonometer

Purpose: To determine accuracy of iCare rebound tonometer (IRT) in terms of agreement with Goldman Applanation Tonometer (GAT) and effect of Central corneal thickness (CCT) on its accuracy. Study Design: Comparative cross sectional study. Place and Duration of Study: Ophthalmology Department of Ittefaq Hospital Lahore from September 2022 to May 2023. Methods: Participants of the study were recruited through non-probability convenient sampling. With Icare PRO® rebound tonometer (IRT), two consecutive sets of measurements with 6 measurements for each set were made, and the averaged values were used for the statistical analyses. After 5 minutes GAT measurement was taken for intraocular pressure (IOP). CCT was measured by ultrasound pachymetry from mean of 2 measurements noted. Data was analyzed by Bland-Altman plots for determining agreement of GAT-IOP and IRT-IOP. Pearson correlation coefficient determined the correlation of GAT-IOP and IRT-IOP with CCT. Results: Out of 200 participants there were 76 (38%) males and 124 (62%) females. Mean age of participants was 27.84 ± 6.1 years. Mean IOP with IRT was 16.24 ± 2.02 (range 12.1 – 20.3 mmHg). Mean IOP with GAT was 14.40 ± 1.98 (range 11.00 – 19 mmHg). Mean IOP with adjusted CCT using GAT was 14.40 ± 1.64 (range 11 – 18 mmHg). Mean CCT was 544.81 ± 42.04 (range 615 – 471 um). Mean IOP-GAT &amp; IOP-IRT with adjusted CCT showed normal distribution. Mean difference of IOP-GAT and IOP-IRT with t test was 1.83 ± 1.12 (p = .079). Conclusion: There is a strong agreement between IOP-GAT and IOP-IRT. CCT had a strong impact on IOP measurements with both tonometers. However, CCT affected IOP reading of GAT more than IRT.

Twenty-Four-Hour Intraocular Pressure Pattern In Glaucoma Suspects in an African Population.

Twenty-four-hour intraocular pressure measurement (Phasing) among glaucoma suspects showed higher intraocular pressure (IOP), greater fluctuation, and more varying peak times occurring mostly outside clinic hours, between 12 midnight and 8 am in 68.9% of them. To characterise 24-hour variation in IOP, in glaucoma suspects and normal individuals in an African population. A cross-sectional analytical study was carried out between March and October 2019 at the University of Ilorin Teaching Hospital. A total of 204 study participants, comprising 102 primary open angle glaucoma (POAG) suspects and 102 age and sex-matched controls with healthy eyes were recruited. Participants had a comprehensive ophthalmic examination. Measurements of IOP were taken every 2 hours during a 24-hour period using an iCare tonometer. The mean age was 43.64±14.02 SD and 43.02±13.55 SD ( P =1.000) for POAG suspects and controls, respectively. The mean peak IOP was significantly higher in POAG suspects (21.87± 4.65mmHg) compared with controls (17.17± 2.32mmHg) ( P <0.001). Whereas, the mean trough IOP reading was not significantly different between the 2 groups. In both groups of participants, the peak and trough IOP in the majority were recorded outside of clinic hours. The majority (68.9%) of POAG suspects had a peak IOP between midnight and 8 am, whereas the control group peaked mostly at 4 pm (16.7%) and 4 am (41.7%). Twenty-four-hour IOP variation was 6mmHg or less in 73.6% of control eyes, while in the POAG suspects, 83.3% of eyes had variation greater than 6mmHg. Compared with age and sex-matched healthy controls, glaucoma suspects of African descent showed significantly higher mean IOP and IOP variation, with most peak IOP detected outside of clinic hours.

Transient Intraocular Pressure Fluctuations After Intravitreal Bevacizumab Injection in Proliferative Diabetic Retinopathy Patients: A Prospective Study.

The clinical use ofintravitreal bevacizumab (IVB),a recombinant humanized monoclonal antibody that functions as an anti-vascular endothelial growth factor (anti-VEGF), has recently increased in patients with retinal ischemic diseases such asproliferative diabetic retinopathy (PDR). The short-term and long-term complications associated with this procedure have not been well established. We aimedto study the possible short-term complication of intraocular pressure (IOP) fluctuations shortly after IVB injection in patients with PDR. A prospective case series of diabetic patients with PDR who underwent IVB injection was performed in the Department of Ophthalmology, Medical Teaching Institution, Khyber Teaching Hospital, Peshawar, Pakistan, from November 1, 2020, to May 1, 2021. The total number of PDR patients of both sexesincluded in the study was 101. A slit lamp examination was performed, and IOP readings were recorded before and 30 min after IVB injection using Goldmann applanation tonometry (GAT). IBM Statistical Package for the Social Sciences version 22 for Windowswas used to analyze the data. Safety of the procedure, defined as IOP ≤20 mmHg 30 min after IVB injection, was determined and stratified according to sex,age, duration of diabetes, and baseline IOP.A post-stratification chi-square test was applied,and a p-value <0.05 was taken as statistically significant. In this study, 60.4% of the participants were male and 39.6% were female. The age of the patients ranged from 30 to 75 years, with a mean age of 55.66±6.37 years. The mean duration of diabetes among the participants was 7.73±2.94 years and the mean baseline IOP was 15.40±1.77 mmHg. Safety(IOP ≤20 mmHg 30 min after IVB injection) was observed in 90.1% of the patients. IVBinjections are safe for use in patients with PDR in terms of immediate IOP changes. However, patients with higher baseline IOP (>15 mmHg) are more likely to develop increased IOP post-procedure and prophylaxis may be prudent in such cases.

EyeCee One preloaded intraocular lens: are patients with glaucoma more at risk?

ObjectiveThe Medicine and Healthcare products Regulatory Agency reported links of raised intraocular pressure (IOP) with recently implanted EyeCee One intraocular lens (IOL). This work investigates if glaucomatous eyes were more...

Assessment of the iCare HOME2, a New IOP Self-Measurement Tonometer.

The iCare HOME2 tonometer generally can be considered reliable for most eyes and clinical settings, although it may produce slightly overestimated or underestimated intraocular pressure readings in thicker and thinner corneas, respectively. To evaluate the accuracy, correlation, and analysis of differences in intraocular pressure (IOP) measurements between the gold standard Goldmann applanation tonometer (GAT) and the new, self-measurement iCare HOME2 tonometer (icare, Vantaa, Finland). In this retrospective study, patients were randomly selected from those who attended for a routine examination in our clinic. After a complete ocular examination, each patient's IOP was measured and recorded with GAT (IOPG) and iCare HOME2 (IOPi). Central corneal thickness (CCT) was measured. Eyes with any corneal morbidity were excluded. Pearson's correlation coefficient was used to determine correlation between paired IOP measurements. Bland-Altman plots were graphed for the analysis of differences for IOP between the instruments. One hundred and thirty-five eyes of 70 patients were included in the study. The mean IOPG was 16.3 ±6.5mm Hg (range 3-56). The mean IOPi was 16.5 ±7.3mm Hg (range 3-55), (P=0.47). A strong, significant positive correlation was found for paired IOP measurements by the two instruments (r=0.94; P<0.0001). A small systematic proportional bias was seen for the paired IOP measurements, meaning that with higher IOPs the iCare HOME2 yielded higher IOP readings than GAT; but this difference was clinically insignificant. The instrument underestimated IOPs with corneas thinner than 522 µm while it overestimated IOPs when corneas were thicker than this. The iCare HOME2 could be a reliable tonometer for most eyes and clinical settings. CCT measurement is recommended in patients who use the instrument.

Real-world agreement of same-visit Tono-Pen vs Goldmann applanation intraocular pressure measurements using electronic health records

PurposeTo compare intraocular pressure (IOP) obtained with Tono-Pen (TP) and Goldmann applanation (GAT) using large-scale electronic health records (EHR). DesignRetrospective cohort study. MethodsA single pair of eligible TP/GAT IOP readings was randomly selected from the EHR for each ophthalmology patient at an academic ophthalmology center (2013–2022), yielding 4550 eligible measurements. We used Bland-Altman analysis to describe agreement between TP/GAT IOP differences and mean IOP measurements. We also used multivariable logistic regression to identify factors associated with different IOP readings in the same eye, including demographics, glaucoma diagnosis, and central corneal thickness (CCT). Primary outcome metrics were discrepant measurements between TP and GAT as defined by two methods: Outcome A (normal TP despite elevated GAT measurements), and Outcome B (TP and GAT IOP differences ≥6 mmHg). ResultThe mean TP/GAT IOP difference was 0.15 mmHg ( ± 5.49 mmHg 95% CI). There was high correlation between the measurements (r = 0.790, p < 0.001). We found that TP overestimated pressures at IOP <16.5 mmHg and underestimated at IOP >16.5 mmHg (Fig. 4). Discrepant measurements accounted for 2.6% (N = 116) and 5.2% (N = 238) for outcomes A and B respectively. Patients with thinner CCT had higher odds of discrepant IOP (OR 0.88 per 25 μm increase, CI [0.84–0.92], p < 0.0001; OR 0.88 per 25 μm increase, CI [0.84–0.92], p < 0.0001 for outcomes A and B respectively). ConclusionIn a real-world academic practice setting, TP and GAT IOP measurements demonstrated close agreement, although 2.6% of measurements showed elevated GAT IOP despite normal TP measurements, and 5.2% of measurements were ≥6 mmHg apart.

Goldmann Applanation Tonometry: Comparison of Intraocular Pressure Values Obtained with Disposable Tip and Conventional Applanation Prism in the Population without Clinical Signs of Glaucoma.

Comparing intraocular pressure (IOP) measurements using Goldmann applanation prism and TonoSafe® in the population without signs of glaucoma. Patients with no ocular pathologies, except ametropia (until ± 4 D) or IOP of <30 mm Hg without signs of glaucoma by optic disc structural analysis by fundus biomicroscopy. The IOP was measured sequentially using the traditional cone and the TonoSafe®, according to a randomization list to determine which device would be used first. The measurements from the right and left eyes were compared separately. Since there was no statistical difference, both eyes were considered in this study. A total of 385 eyes of 194 patients with a mean age of 66.4 ± 11.2 years old were included. The mean IOP with conventional prism was 14.2 ± 3.6 and 14.3 ± 3.6 mm Hg with TonoSafe®. Differences were not statistically significant by the Wilcoxon test (p = 0.3). The median was 14.0 mm Hg for both groups. The mean difference between measurements was 0.04 mm Hg, with the median equal to zero. There was no statistical difference in IOP readings according to which device was the first measurement. No statistical difference was found in IOP was measured with conventional prism or TonoSafe® in the population without signs of glaucoma. The data provided by our study support the efficacy and safety of the disposable tonometer compared to the Goldman tonometer in measuring IOP in patients without glaucoma. Soares PHA, Santos RDO, Filho CRADM, et al. Goldmann Applanation Tonometry: Comparison of Intraocular Pressure Values Obtained with Disposable Tip and Conventional Applanation Prism in the Population without Clinical Signs of Glaucoma. J Curr Glaucoma Pract 2023;17(2):75-78.

Comparison of intraocular pressure in New Zealand White rabbits measured using rebound and applanation tonometers and four different methods of physical restraint

ABSTRACT Aims To compare intraocular pressure (IOP) measurements obtained in rabbits using rebound (TV) and applanation (TPV) tonometers with four different methods of physical restraint. Methods A total of 20 New Zealand White rabbits (40 eyes) were included in this study. IOP readings were obtained from both eyes using the two different tonometers. The rabbits were placed on a table and restrained by wrapping in a cloth (Method I), by scruffing with rear support (Method II), by wrapping in a cloth and cupped in the hands (Method III), or by a box restrainer (Method IV). Results The mean IOP measurement obtained by TPV was higher than that obtained with the TV for all handling methods. Mean differences (TV−TPV, in mmHg) in IOP were −5.3 (95% Cl = −6.5 to −4.1) for Method 1, −4.7 (95% Cl = −6.2 to −3.29) for Method II, −4.9 (95% Cl = −6.2 to −3.7) for Method III and −7.6 (95% Cl = −9.2 to −5.9) for Method IV. Using the TV tonometer, mean IOP for Method IV was higher than for Method I (mean difference 2.1 (95% Cl = 1.1–3.1)), whereas using the TPV tonometer, mean IOP for Method IV was significantly higher than Method I, II, and III (mean differences: 4.4 (95% Cl = 2.6–5.9), 3.7 (95% Cl = 2–5.3) and 3.8 (95% Cl = 2–5.4), respectively). According to Bland-Altman plots, IOP readings for TPV tended to be higher than those for TV with all handling methods, but with a lack of agreement. The mean difference and 95% limits of agreement for the differences between TV and TPV were −5.4 mmHg (−12.5–1.9 mmHg), −4.7 mmHg (−12.9–3.5 mmHg), −4.9 mmHg (−12–2.2 mmHg), and −7.5 mmHg (−17.4–2.3 mmHg), with Methods I, II, III, and IV, respectively. Comparing TV and TPV, only 7.5%, 12.5%, 27.5%, and 15% of IOP measurements from 20 rabbits were within the range considered clinically acceptable for IOP (± 2 mmHg) for Method I, II, III, and IV, respectively. Conclusion and clinical relevance In conclusion, the physical restraint method should be recorded when IOP is measured in rabbits, and TV and TPV tonometers cannot be used interchangeably (high bias and low proportion of measurements within ± 2 mmHg).

A brief history of the evolution of tonometers and comparison of goldmann applanation tonometer versus non–contact tonometer and their correlation to central corneal thickness

: This study was designed to evaluate and compare differences between Goldmann applanation tonometer’s (GAT) values and non-contact tonometer’s (NCT) values In various central corneal thickness(CCT).: This prospective study of 100 eyes of 50 subjects was done for the age group of 25 yrs – 75 yrs, who did not have any glaucomatous changes in the optic disc. Intraocular pressure readings were taken by GAT and NCT was measured within a fixed time range of 10:00 AM to 1:00 PM to minimize the effect of diurnal variation. CCT and NCT readings were measured by NIDEK 530P while GAT was performed by Appasamy ref AATM-K001 after 20 minutes and was recorded from both eyes of 50 subjects. Then the CCT effect was correlated with the intraocular pressure values, which were obtained by GAT and NCT.: The data were recorded from 100 eyes of 50 subjects, of whom 24 were females and 26 were males.The mean age was 51.22 ± 2.7 years, while the mean CCT value was 530.6 ± 5.7 µ.The mean IOP values respectively for NCT and GAT were 15.41 ± 0.6 mmHg, and 15.11 ± 0.5 mmHg, respectively (Table 1). The data shows a significantly strong positive correlation between NCT and CCT (r= 0.73, P&amp;#60; .0001), and a strong positive correlation between GAT and CCT (r= 0.55, P&amp;#60; .0001) (Table 2, 5 and 6).The Pearson coefficient value between NCT and GAT was also strong (r = 0.76, P&amp;#60; .00001)(Table 3). The findings in our study correlate with earlier research. It demonstrates that, with the application of appropriate correction factors for CCT, NCT can be considered a good screening tool for the measuring Intraocular pressure.

Easyton® transpalpebral versus Perkins applanation tonometry in different populations.

To compare intraocular pressure (IOP) measurements obtained using the new transpalpebral Easyton® tonometer and Perkins applanation tonometer (PAT) in three different clinical populations. The participants of this prospective study were 84 subjects divided into the groups: 22 healthy children (G1), 42 healthy adults (G2), and 20 adult patients with primary open angle glaucoma (G3). The data recorded in 84 eyes of these subjects were age, sex, gender, central corneal thickness (CCT), and axial length (AL). In all eyes, IOP was determined in the same examination room by the same experienced examiner using Easyton® and PAT in random order. Mean differences in IOP readings between Easyton® and PAT were 0.45 ± 1.97 (p = 0.295), -0.15 ± 2.13 (p = 0.654), -1.65 ± 3.22 (p = 0.033), and -0.018 ± 2.50mmHg (p = 0.500) in the groups G1, G2, G3, and whole sample (G4), respectively. Correlations between Easyton® and PAT IOP values were 0.668 (p = 0.001) for G1, 0.463 (p = 0.002) for G2, 0.680 (p < 0.001) for G3, and 0.605 (p < 0.001) for G4. Moderate to good agreement between the two tonometers was found in all groups according to intraclass correlation coefficients, which were 0.794 (p < 0.001) for G1, 0.632 (p < 0.001) for G2, 0.809 (p < 0.001) for G3, and 0.740 (p < 0.001) for G4. The lower and upper limits of agreement between the devices were -5.1 and 4.7mmHg, respectively, in the complete group. No correlation was noted between CCT or AL and the Easyton® IOP measurements. IOP measurements obtained with Easyton® and PAT show an acceptable level of agreement mainly in healthy individuals, recommending it for IOP screening in children and in patients in which PAT measurement may be impared as patients with hemifacial spasms, corneal irregularities, or reduced mobility. It is not recommended for glaucoma patients follow-up.

Modern approaches to interpretation of Maklakov tonometry results

Based on the presumption that the average values of ocular rigidity determined ex vivo are sufficient for clinical evaluation of intraocular pressure (IOP), calibration of the Maklakov tonometer is done without taking into due account the biomechanical properties of the tunics of the eye, which can affect the results of IOP measurements. Corneal-compensated IOP (IOPcc) allows evaluating patients' individual structural features of the fibrous tunic of the eye, and according to literature sources, for glaucoma it is a parameter with higher diagnostic value. Comparison of Maklakov tonometer readings and IOPcc from the same patients can improve our understanding of the diagnostic value of tonometry. This article aims to determine based on sufficient clinical data the ranges of corneal-compensated IOP corresponding to applanation tonometry readings performed with a 10-g Maklakov tonometer, and to reveal the dependency between the tip diameter and the IOP with consideration of the variability of biomechanical properties of the fibrous tunic in the population. The comparison study analyzed the readings of 10-g Maklakov tonometer and corneal-compensated intraocular pressure in 14 440 eyes of 7 220 patients (mean age 60.1±10.8 years old) with primary open-angle glaucoma and suspected glaucoma. For analysis, IOPcc values of 6 to 35 were included, with a prerequisite of corneal thickness/ hysteresis data being of high quality. The tip diameter was measured with a Vernier caliper within the accuracy of 0.1 mm according to the instructions from the tonometer manual. It was established that with equal tip diameter the readings of applanation tonometry can still vary significantly, which is associated with population variability in the structure of the fibrous tunic of the eye. A measuring scale was derived consisting of a computation chart with markings denoting the borders of confidence intervals for IOPcc values for 10-g Maklakov tonometer. Mean IOPcc is connected to the applanation tip diameter and the cornea by the following equation: IOP=4.14×D2 -62.4×D+248, which can be used for calibrating Maklakov tonometer in the lower and upper ranges of IOP values. The results of 10-g Maklakov tonometry can be presented as a range of IOP values, which with a certain probability includes the individual IOP level of the patient.