Non-contact Tonometer Research Articles

Comparative Analysis of Central Corneal Thickness in Ocular Hypertension and Healthy Individuals.

This study aimed to compare the central corneal thickness (CCT) between patients with ocular hypertension (OHT) and healthy individuals, and to investigate the relationship between CCT and intraocular pressure (IOP), diopter, and corneal endothelium cell count (CECC). The CCT of 30 healthy subjects and 38 patients with OHT was measured using a non-contact specular microscope. IOP, diopter, and CECC were also assessed for all participants. Comparative analysis of CCT between the two groups was performed, along with correlation analysis between CCT and each parameter. The average CCT for all participants was 527.57 ± 35.84 µm. The average CCT was 516.07 ± 34.76 µm for healthy subjects and 536.66 ± 34.46 µm for patients with ocular hypertension, showing a significant difference between the two groups (P ≤ 0.05). CCT was not correlated with age (Pearson r = -0.098, P = 0.426), diopter (spherical equivalent refraction) (Pearson r = -0.158, P = 0.197), or corneal endothelium cell count (Pearson r = 0.065, P = 0.598). However, a positive correlation was found between ocular hypertension and central corneal thickness (Pearson r = 0.278, P = 0.022). Patients with ocular hypertension of members of the Chinese Han population exhibited greater CCT compared to healthy subjects in this study. CCT showed no association with age, diopter, or corneal endothelium cell count; however, a positive correlation was observed between intraocular pressure and CCT. With CCT as the abscissa and IOP as the ordinate, the linear regression equation is Y=0.05+0.021X (F = 5.508, P = 0.022). The use of non-contact tonometers for measuring CCT may impact the accuracy of diagnosing and treating glaucoma and ocular hypertension.

Corneal and intraocular pressure changes associated to the circadian rhythms: a narrative review.

To synthesize the current body of research regarding the diurnal variations in intraocular pressure (IOP) and corneal biomechanical and morphological parameters, highlighting their significance in various eye conditions. A comprehensive review of studies on the diurnal variations of IOP and corneal parameters was conducted. Tonometry findings from various studies were assessed, including the Goldmann applanation tonometry (GAT) and non-contact tonometers. Data on the variations in central corneal thickness (CCT), corneal curvature, and corneal biomechanics measured by the Ocular Response Analyzer system across different population groups was extracted and analyzed. In both healthy subjects and those with Fuchs dystrophy, IOP and CCT demonstrate marked diurnal declines. GAT remains the gold standard for tonometry, with the highest reliability. However, its measurements are influenced by CCT. Keratoconus patients and those with pseudoexfoliation showed significant diurnal variations in IOP. The biomechanical parameters, especially corneal hysteresis (CH) and the corneal resistance factor (CRF), largely remain stable throughout the day for most of eye conditions, with some exceptions. Notably, the corneal morphology diurnal variation, particularly curvature, yielded mixed conclusions across studies. Circadian rhythms significantly influence various corneal parameters, most notably IOP and CCT. Further studies should emphasize standardized approaches larger sample sizes, and delve deeper into less-explored areas, such as the effects of orthokeratology lenses on diurnal biomechanical shifts.

Aerosolization ocular surface microorganisms accumulation effect during non-contact tonometer measurements

PurposeThis study aimed to verify that aerosolization ocular surface microorganisms (AOSMs) accumulated during non-contact tonometry (NCT) measurements.MethodsA total of 508 participants (740 eyes) were enrolled in the study. In Experiment 1, before NCT was performed on each eye, the air was disinfected, and environment air control samples were collected via Air ideal® 3P (Bio Merieux). During NCT measurements, microbial aerosol samples were collected once from each eye. In Experiment 2, we collected initial blank control samples and then repeated Experiment 1. Finally, in Experiment 3, after the background microbial aerosol investigation, we cumulatively sampled AOSMs from each 10 participants then culture once, without any interventions to interrupt the accumulation. The collected samples were incubated and identified using matrix-assisted laser desorption/ ionization time-of-flight mass spectrometry (MALDI-TOF-MS).ResultsPathogenic Aerococcus viridans and other microorganisms from human eyes can spread and accumulate in the air during NCT measurements. The species and quantity of AOSMs produced by NCT measurements can demonstrate an accumulation effect.ConclusionAOSMs generated during NCT measurements are highly likely to spread and accumulate in the air, thereby may increase the risk of exposure to and transmission of bio-aerosols.

Comparability analysis of the HNT-1P Huvitz non contact tonometer for the measurement of intraocular pressure.

To evaluate the diagnostic validity of the HNT-1P non-contact tonometer (Huvitz) as a tool for accurately measuring intraocular pressure (IOP) in patients with healthy eyes, compared to the Goldmann applanation tonometer (GAT), which is the Gold Standard method for measurement of IOP. Observational, descriptive, transversal study using 148 eyes of 74 healthy patients without a diagnosis of glaucoma or other ophthalmological diseases. Three measurements of IOP were taken in each eye, using three tonometers: HNT-1P, ICR100, and GAT. The median IOP (quartiles) and mean IOP (SD) its statistical significance were calculated, and comparisons were made between the mean and median IOP values found in three groups: GAT-HNT, GAT-ICR, and HNT-ICR. The difference in mean and median IOP was analyzed in each of the three study groups, and its statistical significance and concordance correlation coefficient (CCC) were calculated. The median IOP with HNT-1P was statistically significantly lower than the median IOP with GAT, (1.1 mmHg, p < 0.001). The median IOP with HNT-1P was also lower than the median IOP with ICR100. As an additional result, the median IOP with GAT was lower than the median IOP with ICR. The CCC was moderate for HNT-ICR (0.72) and low for GAT-HNT and GAT-ICR (0.43 and 0.38, respectively). HNT-1P (Huvitz) provides statistically significantly lower IOP values than those obtained with GAT. HNT-1P could be used for screening of ocular hypertension in postoperative patients. The IOP measurement obtained with HNT-1P should be confirmed with GAT. HNT-1P yields lower IOP values than those obtained with ICR.

Comparison of intraocular pressure measurements with the tono-pen, goldmann applanation tonometer, and noncontact tonometer in nonglaucomatous pseudophakic children.

To evaluate the agreement between the Goldman applanation tonometer (GAT), Tono-Pen, and noncontact tonometer (NCT) in the measurement of intraocular pressure (IOP) in pseudophakic children. The medical records of nonglaucomatous pseudophakic children between 2009 and 2019 were retrospectively analyzed. A total of 46 eyes of 23 patients operated for bilateral pediatric cataract were included in the study. The patients' mean age was 13.4 ± 4.1years. Central corneal thickness (CCT) and IOP values measured with the GAT, Tono-Pen, and NCT were recorded. Agreement between the tonometers was evaluated by intraclass correlation coefficients (ICC) and the Bland-Altman method. The mean IOP of the 46 eyes included in the study was measured as 13.7 ± 2.3mm Hg with the GAT, 16.0 ± 2.3mm Hg with NCT, and 16.5 ± 2.3mm Hg with the Tono-Pen (p < 0.001). There is no statistical difference between NCT and Tono-Pen measurements, while GAT measurements were significantly lower than those of the NCT and Tono-pen. ICC values showed fair agreement between NCT and Tono-Pen (ICC = 0.720), whereas there was poor agreement between GAT and NCT (ICC = 0.501) and Tono-pen (ICC = 0.314). With all devices included in the study, thicker corneas were associated with higher IOP measurements. Although there was moderate agreement between the NCT and Tono-Pen, there was a statistically significant difference in the IOP values provided by the three devices. Our results suggest these devices should not be used interchangeably.

Evaluation of a new transpalpebral tonometer for self-measuring intraocular pressure.

We developed a novel transpalpebral self-tonometer called the TapEye tonometer (TET) based on palpation of the upper eyelid. Our goal was to evaluate a method for improving the accuracy of measuring intraocular pressure (IOP) through the eyelid. Participants underwent standardized training by technicians and were required to be able to use the TET for study inclusion. Subsequently, a noncontact tonometer and Goldmann applanation tonometer (GAT) were used. All participants were instructed to measure their IOPs using the three tonometers at baseline (visit 1) and at 1 month (visit 2). At visit 2, the corrected IOP value measured by the TET (c-TET) was calculated using the difference between the TET and GAT measurements obtained at visit 1. No significant correlations were found between the TET and GAT measurements at any visit, but the correlation between the c-TET and GAT measurements at visit 2 was significant. The mean difference between the c-TET and GAT measurements was 0.4 ± 3.7 mmHg in the right eye and 0.5 ± 3.4 mmHg in the left eye. After correcting the IOP based on the difference between the TET and GAT measurements at the initial visit, the corrected IOP value of the TET was correlated with that of the GAT at the second visit. The TET has the potential to address an unmet need by providing a tool for minimally invasive IOP measurements. Clinical trial registration number: jRCTs032220268.

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.

Clinical assessment of corneal alterations in endocrine disorders

Corneal alterations are frequent in many endocrine disorders like Grave’s ophthalmopathy and diabetes mellitus. Since early diagnosis of such a change can prevent visual impairment, it presents a challenge to an ophthalmologist.Clinical assessment &amp; significance of corneal alterations in endocrine disorders.1. To conduct comprehensive assessment of corneal alterations in endocrine disorders. 2. To Identify specific corneal abnormalities in patients with endocrine disorders. 3. To delineate the clinical significance of corneal alterations in endocrine disorders by determining their impact on visual function and guiding therapeutic strategies.This study was a prospective, observational, hospital-based study conducted over a period of two years including 150 patients of different endocrine disorders. Ocular examination included physical examination to check for any pain on ocular movements, ophthalmoplegia, diplopia, or proptosis. Visual acuity was examined by Snellen’s chart, anterior segment by slit-lamp, intra-ocular pressure by non-contact tonometer, qualitative measurement of corneal sensation by a cotton-wisp and central corneal thickness was measured by pachymetry. Corneal endothelial cell parameters like endothelial cell density (ECD), coefficient of variation of cell area (CV), percentage of hexagonal cell (HEX) were measured by clinical specular microscope.The age range was 14 to 82 years with mean age being 48.43±14.2 years. The male to female ratio was 1.34:1. Type-2 diabetes mellitus was the most frequently encountered endocrine disorder (64.7%), followed by hypothyroidism (13.3%). Addison’s disease was the least encountered (0.7%). The most severe changes to the cornea, such as chronic epithelial abnormalities, superficial punctate keratopathy, altered corneal sensations, and dry eyes, were observed in patients with type 2 diabetes, followed by Graves’s ophthalmopathy and hypothyroidism. Patients with T2DM and T1DM had elevated CCT values, reduced endothelial cell density, abnormally high coefficient of variance and low hexagonal cells.The present study showed that different corneal alterations can be possible in endocrine disorders. So all endocrine disorders should undergo comprehensive ophthalmological examination to prevent visual impairment.

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.

Non-contact tonometry: predicting intraocular pressure using a material-corneal thickness-independent methodology.

Introduction: Glaucoma, a leading cause of blindness worldwide, is primarily caused by elevated intraocular pressure (IOP). Accurate and reliable IOP measurements are the key to diagnose the pathology in time and to provide for effective treatment strategies. The currently available methods for measuring IOP include contact and non contact tonometers (NCT), which estimate IOP based on the corneal deformation caused by an external load, that in the case of NCT is an air pulse. The deformation of the cornea during the tonometry is the result of the coupling between the IOP, the mechanical properties of the corneal tissue, the corneal thickness, and the external force applied. Therefore, there is the need to decouple the four contributions to estimate the IOP more reliably. Methods: This paper aims to propose a new methodology to estimate the IOP based on the analysis of the mechanical work performed by the air jet and by the IOP during the NCT test. A numerical eye model is presented, initially deformed by the action of a falling mass to study the energy balance. Subsequently, Fluid-Structure Interaction (FSI) simulations are conducted to simulate the action of Corvis ST. Results and discussion: The new IOP estimation procedure is proposed based on the results of the simulations. The methodology is centred on the analysis of the time of maximum apex velocity rather than the point of first applanation leading to a new IOP estimation not influenced by the geometrical and mechanical corneal factors.

Topical application of hypotensive drugs for the prevention of intraocular pressure elevation after intravitreal injections of anti-VEGF drugs

This study evaluates the effect of topical hypotensive drugs on the short-term IOP rise after IVI of anti-VEGF drugs in patients with nAMD. The prospective study included 80 patients with newly diagnosed nAMD. Before the start of treatment, the patients were divided into 4 groups of 20 people each: 1st - controls, who received no prophylactic drugs, in the 2nd, 3rd and 4th groups local instillations of one drop of hypotensive drugs brinzolamide 1%, brinzolamide-timolol, brimonidine-timolol were performed in the conjunctival sac twice: 1 day before the injection (at 20:00) and on the day of the injection 2 hours before the manipulation (at 08:00), respectively. IOP was measured in each patient using ICare Pro non-contact tonometer before injection, as well as 1 min, 30 and 60 min after injection. Prophylactic use of hypotensive drugs was associated with a significant decrease in IOP immediately after IVI compared to the same parameter in the 1st group (p<0.001), the maximum decrease in IOP values was observed when using a fixed combination of brimonidine-timolol by 12.1 mm Hg compared to the controls (p<0.001), the combination of brinzolamide-timolol reduced IOP by 8.5 mm Hg (p<0.001), brinzolamide 1% led to the smallest decrease in IOP - by 5.1 mm Hg (p<0.001). Study patients that received instillations of brimonidine-timolol combination of one drop into the conjunctival sac 1 day before the injection and on the day of the injection showed the maximum decrease in IOP compared to patients of the other groups.

Removal Large Fragment of Metal Wire from Eye Using Vitrectomy. Clinical Case

Purpose. Demonstration of non-standard clinical case of removing large fragment of metal wire from the eye. Patient and methods. Patient, 37 years old, with penetrating right eye injury with intraocular foreign body (IOFB) introduction — a fragment of metal wire. After unsuccessful attempt to remove IOFB during primary repair of eye injuries lacerations by ophthalmologist of the surgical department of the district hospital, he was sent to the Khabarovsk branch of the S. Fyodorov Eye Microsurgery Federal State Institution. On admission: VIS OD — 0.01 uncorrected, intraocular pressure (IOP) — 16 mm Hg (noncontact tonometer TOMEY, Japan). OD — metal IOFB protrudes by 1.0 mm from the corneoscleral laceration in projection of corneal limbus at the 13 o’clock position, postoperative aphakia; according to B-scan ultrasonic data: metallic foreign body of linear shape, 14.3 mm long, about 1.5 mm thick. There is hemorrhage in the vitreous cavity. Results. Initially, conditions for visualization of the vitreous cavity were created by performing 25G vitrectomy. The course of wire location was specified: under the choroid and retina, going out through the sclera in the equatorial region. After conjunctival tweezers expanded wound edges, the embedded fragment of wire was delicately remove: 25 mm in length and 2 mm in diameter. A single retinal break was delimited by cryotherapy and laser photocoagulation. On the 2nd day: VIS OD — 0.3 with diaphragm, uncorrected; IOP — 13 mm Hg. After 3 months: VIS OD — 0.01 sph + 13.0 D = 0.7, IOP — 14 mm Hg. Silicone removal was combined with intraocular lens implantation model RSP-3 (+23D). The next day: VIS OD — 0.3 with diaphragm, 0.5 cyl — 6.0 D ax 170 = 0.5; IOP — 16 mm Hg. Conclusion. Use of 25G vitrectomy for removal IOFB localized between the inner membranes of the eye created optimal conditions for visualizing depth of its penetration, which minimized traumatic impact and avoided severe intra- and postoperative complications.

Corneal retardation time as an ocular hypertension disease indicator

Objective. A detailed analysis of the corneal retardation time τ as a highly related parameter to the intraocular pressure (IOP), and its plausible role as an indicator of ocular hypertension disease. Approach. A simple theoretical expression for τ is derived within the corneal viscoelastic model of Kelvin-Voigt with 3 elements. This retardation time can be easily calculated from the well-known signal and pressure amplitudes of non-contact tonometers like the Ocular Response Analyzer (ORA). Then, a population-based study was performed where 100 subjects aged from 18 to 30 were analyzed (within this group, about 10% had an elevated IOP with more than 21 mmHg). Main results. A clear relationship between the corneal retardation time and the corneal-compensated intraocular pressure (IOPcc) was found, underlying the risk for ocular hypertensive (OHT) subjects with lower τ values to develop hypertension illnesses (due to the inability of poorly viscoelastic corneas to absorb IOP fluctuations, resulting in probable optic nerve damage). Significance. Our results might provide an useful tool to systematically discern which OHT patients (and even those with normal IOP values) are more likely to suffer glaucoma progression and, consequently, ensure an early diagnosis.

The extraction and application of antisymmetric characteristics of the cornea during air-puff perturbations

BackgroundA non-contact tonometer is used to measure intraocular pressure, and studies have primarily relied on apex displacements to assess corneal properties. However, previous studies have overlooked the asymmetric characteristics of lateral corneal perturbations, leading to a gap in understanding of the lateral mechanical properties and its application. MethodTo investigate these lateral perturbations, we designed an experiment to sequentially record the corneal profiles when two consecutive air-puffs were applied at the center of the same cornea within a short period. Moreover, we used modal decomposition to decompose anterior surface profiles into symmetric and antisymmetric modes to comprehensively analyze the asymmetric characteristics. To extract mechanical properties, we utilized high-pass frequency analysis (>250 Hz) to filter out noise and errors. ResultsSymmetric modes between the two consecutive air-puffs exhibited major similarities during vibration; however, antisymmetric modes exhibited minor differences in lateral perturbations of asymmetric vibration. The antisymmetric modes might be related to air-puff misalignment and mechanical properties. Through applying frequency analysis, the mechanical properties could be proven at high frequencies and misalignment shown at low frequencies. Furthermore, we compared the corneal vibration profiles of 259 healthy participants and 50 patients with keratoconus. Their properties showed that the antisymmetric modes of the keratoconus group exhibited a completely opposite direction of deformation compared to that in the healthy group. ConclusionsOur proposed algorithm not only extracts antisymmetric characteristics but also offers valuable insights into decompose misalignment and mechanical properties of healthy and keratoconus corneas, presenting a new perspective for corneal biomechanics.

Comparison of Three Methods of Tonometry in Patients With Inactive Thyroid-Associated Orbitopathy

Introduction: Intraocular pressure (IOP) measurement in patients with thyroid-associated orbitopathy (TAO) can be difficult and misleading, particularly in patients with diplopia and eye deviation (esotropia or hypotropia). However, when measuring IOP, it is also necessary to pay sufficient attention to TAO patients without diplopia in primary gaze direction and without motility disorder that might not be readily apparent. Purpose: The aim of this study was to evaluate the accuracy of measurement of intraocular pressure (IOP) using three different types of tonometers: the rebound tonometer (iCARE), the Goldmann applanation tonometer (GAT) and the non-contact airpuff tonometer (NCT) in patients with inactive TAO. Materials and Methods: A total of 98 eyes of 49 adult patients with TAO were examined. The study group included 36 females and 13 males, with an age range of 19–70 years and a median age of 55.0. All the patients had evidence of thyroid disease, a history of mild to moderate TAO, no clinical signs or symptoms of active disease, and no diplopia in direct gaze direction. In addition to a comprehensive eye examination, all the patients underwent measurement of intraocular pressure with three tonometers: NCT, iCARE, and GAT. The measurements with these three devices were compared. Results: The mean IOP was 18.1 ± 2.4 mmHg (range 13–25 mmHg) with GAT, 22.3 ±5.0 mmHg (range 13–35 mmHg) with NCT, and 18.0 ±2.4 mmHg (range 13.3–26 mmHg) with iCARE. The mean difference between the GAT and iCARE measurements (using the Bland-Altman analysis) was -0.1 ±1.16 mmHg (limits of agreement -2.4 to 2.1). The mean difference between the GAT and NCT measurements was 4.2 ±3.6 mmHg (limits of agreement -2.8 to 11.2). The mean difference between the iCARE and NCT measurements was -4.3 ±3.7 mmHg (limits of agreement -11.6 to 2.9). No significant difference was found between GAT and iCARE (p = 1.000). However, there was a significant difference between GAT and NCT (p &lt; 0.0001), as well as between iCARE and NCT (p &lt; 0.0001). Conclusions: In patients with TAO, NCT significantly overestimates IOP values compared to the GAT and ICare. By contrast, the iCARE rebound tonometer provides IOP measurements comparable to the gold standard GAT in these patients.

Association Between Days of the Week and Intraocular Pressure: Japan Ningen Dock Study.

The analysis of intraocular pressure (IOP) by day of the week using the mega database showed a periodic weekly pattern with the highest value on Monday. To evaluate IOP by the day of the week. Annual health checkup examinees between April 2014 and March 2015 were cross-sectionally evaluated. As a result, 655,818 participants [51.5±10.5 (range: 20-96) years, 40.1% women] from 103 medical centers were included. IOP was measured using a noncontact tonometer. The mean IOPs of each day of the week were compared using multiple comparison test and multiple linear regression analysis. Wednesday was set as the reference. Moreover, weekly IOP variations stratified by sex and age were also evaluated. Mean IOPs from Monday to Sunday were 13.19±2.97, 13.06±2.92, 13.05±2.91, 13.05±2.92, 13.12±2.94, 13.10±2.96, and 13.16±2.78mmHg. IOP was significantly higher on Monday, Friday, and Saturday than those on Wednesday ( P <0.001, <0.001, 0.002). After adjusting for factors affecting IOP, the IOPs on Monday and Saturday were higher than those on Wednesday [β=0.097 (95% CI: 0.074-0.121), P <0.001; β=0.032 (95% CI: 0.005-0.059), P =0.019]. Men had significantly higher IOPs on Monday and Saturday than on Wednesday [β=0.142 (95% CI: 0.110-0.173), P <0.001; β=0.053 (95% CI: 0.017-0.089), P =0.004], whereas women did not have a significant trend. Participants aged below 65 years had higher IOPs on Monday ( P <0.001 in under 60 years; P =0.003 in 60-64 years), while those aged 65 years or older did not ( P =0.856). IOP values may have a periodic weekly pattern. The high IOP on Monday was more pronounced in men aged less than 65 years.

Assessing Agreement and Variability Among Alternative Devices for Intraocular Pressure Measurement: A Comparative Study.

Intraocular pressure (IOP) measurement is critical in diagnosing and managing eye conditions. This study aims to assess the comparability of three alternative devices for measuring IOP: Noncontact tonometer, Icare rebound tonometer, and Tono-Pen. A cross-sectional study included 172 adult participants (87 males and 85 females) who underwent IOP and central corneal thickness (CCT) assessments. IOP was measured using Noncontact (Canon TX-20), Icare (Icare TA01i), and Tono-Pen (Tonopen XL). CCT was measured with the built-in pachymetry of the Noncontact tonometer. Correlation coefficients and Bland-Altman analyses were conducted to assess the relationships and agreements between these tonometers. Participants were grouped based on IOP and CCT levels. The mean of the standard deviation of the three tonometer results was calculated to evaluate measurement result variability. One-way analysis of variance was conducted for comparing between the groups. IOP measurements among the three devices were not significantly different, indicating their comparability. Correlation analysis revealed strong correlations between the tonometers. Bland-Altman analysis showed good agreement, with the Icare rebound tonometer and Tono-Pen exhibiting narrower limits of agreement. Furthermore, IOP levels influenced measurement result variability, with higher IOP levels associated with greater variance. This study demonstrates that the alternative devices examined can provide reliable IOP measurements. It highlights the potential of these alternative devices for IOP measurement. These findings have implications for clinical practice, offering practitioners additional tools for accurate IOP assessment.

Scope of optometry practice in Trinidad and Tobago: A cross-sectional study.

To report the scope of optometry practice in Trinidad and Tobago to identify areas that need improvement. A cross-sectional study of optometrists in Trinidad and Tobago was conducted using a validated self-structured questionnaire. Data obtained was exported to the Statistical Package for Social Sciences. Descriptive analysis and Pearson χ 2 were used to summarize the demographic data and determine associations, respectively. A total of 63 optometrists participated in the study. Majority of them were females (69.8%, n = 44), Christians (65.1%), East Indians (47.6%), and 30 years and below (66.7%). Most (87%) of them utilized routine optometric equipment in their clinical practice including autorefractors, retinoscopes, direct ophthalmoscopes, lensometers, phoropters, slit lamp biomicroscopes, trial lens boxes, and visual acuity chart projectors. A few of them have noncontact tonometer (4.8%), Volk lenses (1.6%), and perform color vision tests (1.6%). Fewer (12.7%, n = 8) practitioners provided low-vision services. The use of pharmaceutical agents was prevalent among the participants (55.6%). Additionally, the provision of contact lenses was the most frequently practiced service among the participants (85.7%, n = 54). A significant association was observed between the provision of low-vision services and sex (p = 0.03). The scope of optometry practice in Trinidad and Tobago is in accordance with the basic guidelines set out by the World Council of Optometry but there is need to get more involved in the provision of low vision and other specialty services.

Agreement of intraocular pressure measurement with Corvis ST, non-contact tonometer, and Goldmann applanation tonometer in children with ocular hypertension and related factors.

To access the agreement of intraocular pressure (IOP) values obtained from biomechanically corrected tonometer [Corvis ST (CST)], non-contact tonometer (NCT), and Goldmann applanation tonometer (GAT) in children with NCT measured-IOP (NCT-IOP) values of 22 mm Hg or more, and related factors. A total of 51 eyes with NCT-IOP≥22 mm Hg in children aged 7 to 14y were examined and IOP was measured by CST, NCT, and GAT. Based on GAT measured IOP (GAT-IOP), ocular hypertension (OHT) group (≥22 mm Hg, 24 eyes) and the non-OHT group (<22 mm Hg, 27 eyes) were defined. We compared the agreement of the three measurements, i.e., CST measured IOP (CST-IOP), GAT-IOP, and NCT-IOP, and further analyzed the correlation between the differences in tonometry readings, central corneal thickness (CCT), axial length (AL), optic disc rim volume, and age. Compared with the OHT group, thicker CCT, larger rim volume, and higher differences between NCT-IOP and GAT-IOP, were found in the non-OHT group. The differences between CST-IOP and GAT-IOP were lower than the differences between NCT-IOP and GAT-IOP in both groups. The mean differences in CST-IOP and GAT-IOP were 1.26 mm Hg (95% limit of agreement ranged from 0.1 to 2.41 mm Hg, OHT group) and 1.20 mm Hg (95% limit of agreement ranged from -0.5 to 3.00 mm Hg, non-OHT group), and the mean differences in NCT and GAT were 3.90 mm Hg (95% limit of agreement ranged from -0.19 to 9.70 mm Hg, OHT group) and 6.00 mm Hg (95% limit of agreement ranged from 1.50 to 10.50 mm Hg, non-OHT group). The differences between CST-IOP and GAT-IOP were not related to CCT, age, and AL in both groups; while the differences between NCT-IOP and GAT-IOP were related to CCT in the OHT group (r=0.93, P<0.001) and to CCT and AL in the non-OHT group (r=0.66, P<0.001, r=-0.81, P<0.001). The accuracy of NCT in the diagnosis of pediatric OHT is low. The agreement of CST-IOP and GAT-IOP was significantly higher in children with and without OHT than in those with NCT-IOP and GAT-IOP. Therefore, CST can be used as a good alternative for IOP measurement in children. The impacts of CCT and AL on NCT measurement need to be fully considered when managing childhood IOP.

Comparison of intraocular pressure measurements obtained by icare pro tonometer, non-contact tonometer and Goldmann applanation tonometer in healthy individuals

The goal of this paper was to compare the intraocular pressure (IOP) measurements obtained via iCare Pro rebound (IRT), non-contact tonometry (NCT), and Goldmann applanation (GAT) tonometry in healthy subjects. One hundred and twenty-five healthy individuals were included in this study. The participants' IOP measurements were obtained via non-contact tonometry. After routine ophthalmic examination, central corneal thickness (CCT) was measured with a topography device. Intraocular pressure was measured via iCare Pro rebound tonometry. After waiting for 5minutes, three measurements were taken with GAT under topical anaesthesia, and their means were recorded. Interdevice agreement was evaluated with the intraclass correlation coefficient (ICC) and Bland-Altman analysis. The mean IOP measurements for NCT, IRT, and GAT were 15.97±2.99, 17.47±2.86, and 16.46±2.68mmHg, respectively. The mean difference between NCT and GAT was -0.49± 1.89mmHg, the mean difference between IRT and GAT was 1.01±1.90mmHg, and the mean difference between NCT and IRT was -1.50±2.02mmHg. Agreement between devices was found to be >0.8 for each tonometry ICC. There were significant positive correlations between the measurements obtained via these three instruments and CCT. In this study, IOP was measured slightly lower with NCT than GAT, but it was about 1mmHg higher with IRT than GAT on average. All three devices appeared to be affected by CCT, with NCT being the most affected in this regard. The three instruments can be used for routine inspection and screening. However, considering the differences in the measurements obtained by using them, it is clear that following up IOP measurements with GAT measurements is beneficial in advanced glaucoma patients.