Icare Tonometer Research Articles

Comparison of the Icare Tonometer and the Hand-held Goldmann Applanation Tonometer in Pediatric Aphakia

To compare the intraocular pressure (IOP) measurements obtained by the Icare and the hand-held Goldmann applanation tonometer (also called Perkins) in aphakic children after congenital cataract surgery. We investigated 125 children with aphakia after congenital cataract surgery in this study. A younger group (3 to 30 mo) and an elder group (31 to 72 mo) were divided in those patients by their age. In the younger group, all measurements were performed under sedation using chloral hydrate. Axial length of the eye and central corneal thickness (CCT) were also measured from all patients. Significant correlation was found on IOP readings obtained by the Icare and the Perkins tonometers (r=0.943, P<0.001). After establishing a Bland-Altman plot, we found that 95% limit of the agreement between the 2 methods distributed between -1.6 to 5.6 mm Hg. The IOPs recorded from the Icare increased faster than that from the Perkins tonometer with the increase of the CCT thickness; a significant association relationship was found on the IOP difference between the 2 measurements (r=0.408, P<0.001). However, no statistical correlation was identified between the axial length and the IOPs recorded by either tonometer. Most of the young patients accepted the Icare tonometer under unsedated conditions. This significant advantage indicated that the Icare tonometer will be overall better tolerated in pediatric aphakia population, although it could overestimate the IOPs compared with the measurements obtained from the Perkins tonometer. Differences in readings between the 2 tonometers become bigger as the CCT increase.

This issue of ACTA, printed and electronic

The illustration on the cover shows virtual reality cataract surgery, which is discussed by Selvander and Åsman in this issue of ACTA. Prokofyeva et al. in Germany and Belgium review the potential prevention of cataracts in Europe. Risk factors for cataract include smoking, diabetes, asthma and cardiovascular disease. Heijl et al. in Sweden, Germany and the UK find visual field progression in patients with glaucoma to be variable and frequently rapid enough to influence quality of life. Andersson et al. in Sweden tested an artificial neural network and found this to equal physicians in the assessment of visual fields in glaucoma. Kok et al. in the Netherlands show that cataracts influence the estimation of retinal nerve fibre layer thickness with OCT. Martinez-de-la-Casa et al. in Spain recommend tissue glue to close conjunctiva after trabeculectomy. Rii et al. in Japan discuss childhood-onset optic disc pit maculopathy following blunt ocular trauma. Hamoudi et al. in Denmark report a small change in refraction following pars plana vitrectomy. Burstedt et al. in Sweden describe genotype–phenotype in Bothnia-type retinitis pigmentosa. Gustavsson et al. in Sweden found signs of intraocular inflammation in proliferative diabetic retinopathy, but less so in patients with no or nonproliferative retinopathy. Immonen et al. in Finland conclude that telomere length is not associated with exudative AMD or high-risk drusen. Matsuba et al. in Japan used 3D-CT to localize intraocular foreign body. Molvær et al. in Denmark use computer models to localize stem cells in the corneal limbal region. Koranyi et al. in Sweden recommend cut and paste method for surgery of pterygium. Selvander and Åsman in Sweden recommend a virtual reality training system for cataract surgery. Cornut et al. in France found that initial visual acuity predicts outcome in post-traumatic endophthalmitis. Nangia et al. in India and Germany found undercorrected refractive errors to be a major cause of visual impairment in India. Sveinn Hakon Hardarsson in Iceland presents his PhD thesis on retinal oximetry, which is published as an electronic supplement to the journal. The following publications are published in the electronic portion of ACTA and are available on www.actaophtalmologica.com, as are all publications in ACTA Ophthalmologica. Scanlon et al. in the UK demonstrate that the risk of progression of diabetic retinopathy is significantly higher for patients with diabetic retinopathy in both eyes compared with those who have retinopathy in one or neither eye. Bezatis et al. in Germany found that Ozurdex improves vision and reduces macular oedema in retinal vein occlusion. Pemp et al. in Romania and Austria found increased vessel diameters in the retina of patients with type 1 diabetes and no or mild retinopathy. Nishi et al. in Japan suggest that contrast and functional visual acuity may detect early visual disturbance in patients with epiretinal membranes. Yang et al. in China and Germany report choroidal vascular engorgement in patients with central serous chorioretinopathy. Linke et al. in Germany report similar results in both eyes in 12500 patients undergoing refractive surgery. Ling et al. in China found that doxycycline reduced angiogenesis and inflammation in alkali-burned mouse corneas. Mansouri et al. in USA found only modest intragrader reproducibility in evaluating parapapillary atrophy. Häntzschel et al. in Germany examined the correlation between structural damage to optic nerve and visual field and found this to be less prominent in normal tension than high tension glaucoma. Mastropasqua et al. in Italy found increased density of conjunctival goblet cells in patients treated with preservative-free tafluprost. Kim et al. from Korea found the I-care tonometer to be reliable and give slightly higher IOP readings than Goldman tonometry. Dimitrova et al. in Macedonia and Japan comment on the paper by Stalmans et al. on blood flow and body posture. Rencová et al. in Czech Republic report that rheohemapheresis reduces drusenoid retinal pigment epithelium detachment. Comez et al. in Turkey recommend evisceration with cornea preservation. Yoshikawa et al. in Japan suggest that blocking vascular adhesion protein suppresses neovascularization. Mattila et al. in Finland used corneal cross-linking to treat pseudomonas keratitis. de Geus et al. in the Netherlands found little help in changing from bevacizumab to ranibizumab in unresponsive patients. Bailie et al. in the UK report significant visual and psychological morbidity in patients with optic atrophy. I wish you all a warm and happy summer.

Consistency study on intraocular pressure measured through different position with different angle by iCare rebound tonometer

Objective To analyze the effect of iCare rebound tonometer in different position,different angle measuring on intraocular pressure.Methods Intraocular pressure was measured using the iCare rebound tonometer on the right eyes of 108 subjects in various conditions as follows:first,in an upright position toward the center of the cornea with the probe perpendicular to the corneal plane ; then,at 2 mm from the limbus in the nasal and temporal regions with the probe perpendicular to the corneal plane or along the visual axis; and lastly,with the angled probe touching the central cornea at angles of 10-20°.Paired t-test was used to assess the agreement between the three methods.Pearson's correlation coefficient was used for correlation analysis.Results When the probe was vertical,angle measure central corneal limbal 2 mm nasal and temporal region (0-180 ° along Meridian),IOP respectively was (16.388 9 ± 5.305 32),(16.370 4 ± 5.479 94),(16.435 2 ±5.719 74)mm Hg,and good correlation was found between intraocular pressure and central cornea intraocular pressure and horizontal meridian nasal (r2 =0.910,P ＜ 0.05),temporal (r2 =0.878,P ＜ 0.05).Probe tilt of 10-20°,central cornea intraocular pressure IOP results was (16.472 2 ± 5.339 78)mm Hg,and relevance was found between IOP results and central cornea intraocular pressure with vertical probe (r2 =0.853,P ＜ 0.05).Conclusions iCare tonometer is reliable measurement of intraocular pressure not only through the central region of the cornea but also through corneal peripheral region,no matter whether the probe is vertical or inclined. Key words: Measuring of intraocular pressure; Intraocular pressure; iCare rebound tonometer

Effects of Different Sleeping Postures on Intraocular Pressure and Ocular Perfusion Pressure in Healthy Young Subjects

To investigate the effects of different sleeping positions of head and body on intraocular pressure (IOP) and ocular perfusion pressure (OPP) in healthy, young subjects. Prospective, comparative case series. Twenty healthy young Korean subjects. We measured IOP and blood pressure (BP) with the subjects seated and recumbent, including supine, right lateral decubitus, left lateral decubitus, prone with right head turn, and prone with left head turn positions. We measured IOP using an Icare tonometer in both eyes 5 minutes after assuming each position in a randomized sequence. We calculated the OPP using the formulas based on the mean BP adjusted for the height of the eye over the heart. The eye on the lower side in the lateral decubitus or prone with head turn position was termed the dependent eye. Difference in IOP and OPP of the dependent and nondependent eyes during changes of sleeping positions of body and head. Mean IOP of right and left eyes while sitting was significantly lower than that measured in each recumbent position (all P<0.001). The OPPs in both eyes were significantly higher in all recumbent positions than in a sitting position (all P<0.001). Mean IOP of the dependent eyes was higher than that of the nondependent eyes in the lateral decubitus positions and in the prone positions with head turns (all P<0.001). No significant intereye difference in OPP was found for any position. Among IOPs measured in the recumbent positions, mean IOP of the dependent eye in the lateral decubitus position or in the prone position with head turn was significantly higher than that of the ipsilateral eye in the supine position (all P<0.0001). All sleeping positions of head and body resulted in an elevation of IOP and an increase in the calculated OPP compared with the sitting position in healthy, young subjects. The postural change from supine to lateral decubitus or prone with head turn position increased the IOP of the dependent eyes without significant alteration in OPP in healthy awake subjects. Further research is needed under nocturnal conditions in a sleep laboratory. The authors have no proprietary or commercial interest in any of the materials discussed in this article.

Comparative measurement of intraocular pressure by Icare tonometry and Airpuff tonometry in healthy subjects and patients wearing therapeutic soft contact lenses

The aim of the present study was to compare the measurement of intraocular pressure (IOP) through a therapeutic soft contact lens with the "native" measurement. We additionally investigate whether a rebound tonometer (RT) or non-contact tonometer (NCT) is more suitable to measure IOP through a bandage contact lens. The IOP was determined using each of the two methods, three times successively with (lens measurement) and without (native measurement) a soft contact lens. The Icare tonometer (Icare® TA01i, Icare Finland Oy, 23 subjects) and the Airpuff tonometer (Nidek NT 53OP, Nidek CO., LTD, Hiroishi Gamagori, Aichi, Japan, 16 subjects) were used. We compared the mean values (validity parameter) and standard deviation (precision parameter) of the three individual measurements in each case using the paired t-test. In addition, we conducted a power analysis to estimate the maximum error in the measurement caused by the contact lens (power level set to 0.8). With the Airpuff tonometer we detected no statistically significant between the lens and the native measurement (15.6 ± 2.6 vs. 15.3 ± 2.6mmHg; p = 0.42). The power analysis revealed that the maximum error caused by the contact lens was 1.2mmHg. The Icare tonometry, however, trended toward higher values in the contact lens measurements (17.5 ± 4.3 vs. 16.4 ± 3.5mmHg in the native measurements; p = 0.05). Interestingly, this difference exhibited a statistically significant correlation with the corneal thickness (0.03mmHg per μm corneal thickness; p = 0.04). The use of NCT and RT for IOP measurement over a soft contact lens is feasible. The accuracy appears to be sufficient for the most common clinical applications.

Does Rebound Tonometry Probe Misalignment Modify Intraocular Pressure Measurements in Human Eyes?

Purpose. To examine the influence of positional misalignments on intraocular pressure (IOP) measurement with a rebound tonometer. Methods. Using the iCare rebound tonometer, IOP readings were taken from the right eye of 36 healthy subjects at the central corneal apex (CC) and compared to IOP measures using the Goldmann applanation tonometer (GAT). Using a bespoke rig, iCare IOP readings were also taken 2 mm laterally from CC, both nasally and temporally, along with angular deviations of 5 and 10 degrees, both nasally and temporally to the visual axis. Results. Mean IOP ± SD, as measured by GAT, was 14.7 ± 2.5 mmHg versus iCare tonometer readings of 17.4 ± 3.6 mmHg at CC, representing an iCare IOP overestimation of 2.7 ± 2.8 mmHg (P < 0.001), which increased at higher average IOPs. IOP at CC using the iCare tonometer was not significantly different to values at lateral displacements. IOP was marginally underestimated with angular deviation of the probe but only reaching significance at 10 degrees nasally. Conclusions. As shown previously, the iCare tonometer overestimates IOP compared to GAT. However, IOP measurement in normal, healthy subjects using the iCare rebound tonometer appears insensitive to misalignments. An IOP underestimation of <1 mmHg with the probe deviated 10 degrees nasally reached statistical but not clinical significance levels.

Intraocular pressure in a cohort of healthy eastern European schoolchildren: variations in method and corneal thickness

BackgroundIntraocular pressure (IOP) in the developing eye of a child is not always easy to measure and there is no technique that is known to be the most accurate for the young eye. Measurements are needed on many cohorts of children with different tonometers to determine how the values correlate between instruments, whether corneal parameters affect readings and whether correlations between age and IOP values can be discerned. The aim of this study was to undertake a comparative analysis of three different tonometers on a group of healthy children to see whether differences exist and whether these may be related to central corneal thickness and/or radius of curvature. In addition, the study adds to the relatively small body of literature on IOP in the growing eye which will collectively allow trends to be identified and ultimately norms to be established.MethodsIOP was measured on 115 eyes in a group of Polish children, aged between 5–17 years (mean ± standard deviation [SD] 11.3 ± 3.0 years) using three different tonometers: non-contact (NCT), the ICare and Goldmann applanation (GAT). Readings obtained were compared between instruments and with central corneal thickness and radius of curvature.ResultsThe ICare tonometer provided statistically higher IOP values (16.9 ± 3.4 mmHg) than the GAT (14.7 ± 2.9 mmHg) regardless of corneal thickness and whether or not a correction factor was applied. A correlation was found between central corneal thickness (CCT) and IOP values obtained with all three tonometers but only the IOP values detected with the ICare tonometer showed a statistically significant correlation with radius of curvature (p < 0.004). No correlations with age or gender were found for IOP values measured with any of the instruments.ConclusionsIOP measurements on children vary significantly between instruments and correlations are affected by the corneal thickness. Further studies on children are needed to determine which instrument is most appropriate and to derive a normative IOP scale for the growing eye.

The use of the Icare tonometer reduced the need for anesthesia to measure intraocular pressure in children

To determine whether the introduction of iCare rebound tonometry in a pediatric ophthalmology clinic resulted in fewer examinations under anesthesia to evaluate children with glaucoma. The medical records of consecutive glaucoma patients were retrospectively reviewed. The numbers of examinations under anesthesia (EUAs) and office visits that included measurement of intraocular pressure (IOP) were compared for three periods relative to introduction of the Icare (Icare Finland Oy, Helsinki, Finland) rebound tonometer into our clinical practice: before device introduction, learning/transition period, and routine use. A total of 87 subjects were included: 48 subjects met inclusion criteria for the first period; 58 patients met inclusion criteria for the third period (some subjects straddled all three periods). The average patient age for the first period was 4.2 years and 4.9 years (P = 0.3) for the third period. The number of EUAs performed before the introduction of the Icare was 55 and after the introduction of the Icare was 18 (P < 0.001). The number of office visits at which IOP was measured increased from 34 to 151 (P < 0.001). Data from the transition period suggest a trend and a short learning period. The use of Icare tonometry decreased the need for EUAs to evaluate children with glaucoma and significantly increased successful IOP measurement in clinic.

Nanoparticles for drug delivery

AbstractPurpose To test dorzolamide cyclodextrin microparticle eye drops applied once a day (QD)for intraocular pressure control,compared with Trusopt® 3 times a day (TID).Methods Self aggregating cyclodextrin microparticle eye drops (DorzNP) containing 3% dorzolamide were formulated. The effect of the DorzNP eye drops QD was compared to Trusopt® TID in a prospective randomized single masked crossover trial over 24 hours. Seventeen healthy volunteers with intraocular pressure (IOP) over 18 mmHg were recruited. IOP was measured with an Icare tonometer pro and each patient underwent full eye examination.Results DorzNP eye drops QD and Trusopt® TID lower IOP in a similar manner. At no time point was there a significant difference in IOP between the two groups. The peak effect in both groups was at 4 hours: In the DorzNP group IOP decreased from 21.7 ± 2.4 mmHg at baseline to 17.9 ± 3.9 mmHg, which is 3.8 ± 2.6 mmHg and 18% IOP decrease. In the Trusopt® group IOP decreased from 20.9 ± 2.2 mmHg at baseline to 17.9 ± 3.3, at 4 hours which is 3.1 ± 3.7 mmHg ,14%, (p = 0.97 between groups) IOP drop. At trough at 24 hours the IOP drop was 1.4 ± 2.8 (6%) in DorzNP eyes and 1.5 ± 2.0 (7%) in Trusopt eyes (p = 0.23). Burning in DorzNP eyes on the scale 1‐100 was 12±15 and in Trusopt® eyes 37±30 (p=0.0038). Vision aquity and redness did not differ between the two groupsConclusion The results suggest that once a day dorzolamide nanoparticle eye drops have a similiar effect on intraocular pressure as Trusopt® applied 3 times a day. The dorzolamide microparticle eye drops are well tolerated, less burning than Trusopt®and significantly reduce intraocular pressure. Commercial interest

This issue of Acta, printed and electronic

This issue of Acta, printed and electronic

Age variations in intraocular pressure in a cohort of healthy Austrian school children

Limited data exist detailing the normal range of intraocular pressure (IOP) for healthy school age children. This study aims to describe the mean and normal range of IOP measurements that may be expected using the Icare rebound tonometer and to examine associations between visual function measures and IOP. Six measurements of IOP from each eye were obtained from 211 normal children aged 6-15 years (79 females and 132 males) using the Icare tonometer. Other measures of visual function obtained included: visual acuity, non-cycloplegic retinoscopy, amplitude of accommodation, accommodative facility, and accommodative response. Statistical analysis (Mann-Whitney U test) demonstrated that the male subjects were more likely to have higher IOP measurements than the female subjects (mean IOP males 15.02 mm Hg (SD 2.19), mean IOP females 14.44 (SD 2.01) P=0.041). Analysis (Spearman's rho) showed a statistically significant association between age and IOP (right eye) in males (P<0.001) but no association for females (P=0.459). Using Spearman's rank analysis, statistically significant associations were found between IOP and amplitude of accommodation in males, for the whole data set (P=0.09) and for data up to age 11 (P<0.001). For females no statistically significant association was found for the whole data set (P=0.253) or for data up to age 11 (P=0.08). IOP was not significantly associated with visual acuity, refractive error, accommodative facility, or accommodative response. This study provides useful normative IOP data using the Icare tonometer for a European cohort of school age children.

Effects of trabeculectomy on posture-induced intraocular pressure changes over time

To determine whether trabeculectomy affects postural-induced changes in intraocular pressure (IOP), and whether it is maintained. Thirty-six eyes of 36 patients with open-angle glaucoma who were scheduled for their initial trabeculectomy with adjunctive mitomycin C were prospectively examined. The IOP was measured in the sitting and the lateral decubitus position with an ICare rebound tonometer before, and 1, 3, and 12 months after trabeculectomy. Twenty-nine eyes of 29 patients completed this study. The mean baseline IOP measured with the ICare tonometer was 17.4 ± 4.9 mmHg in the sitting position and 21.3 ± 5.6 mmHg in the lateral decubitus position (p < 0.001). This postural IOP difference, +3.9 mmHg, was reduced to +1.3 ± 1.7 mmHg at 1 month and to +0.8 ± 1.5 mmHg at 3 months after the trabeculectomy (p < 0.001 and p = 0.004 respectively). This decrease in the degree of posture-dependent IOP change was maintained at +1.7 ± 2.2 mmHg at 1 year postoperatively (p < 0.001). In three cases, the postural IOP changes returned to the baseline level, and all three had a failed bleb. Our results indicate that trabeculectomy not only reduces the IOP but also reduces the degree of posture-induced changes in the IOP. Our findings also speculate that measuring the postural IOP changes after trabeculectomy might provide a clue on the functioning of a filtering bleb.

Home Tonometry for Management of Pediatric Glaucoma

To use iCare rebound tonometry in the home setting for documentation of diurnal intraocular pressure (IOP) fluctuations in children. Nonrandomized, prospective clinical study. Pediatric ophthalmology clinic patients were recruited between October 2009 and February 2010 who were able to cooperate with IOP measurement by iCare rebound tonometry and whose caregiver was willing and able to obtain iCare measurements at home. The child's IOP was measured first by iCare tonometry followed by a second method (Goldmann applanation [GAT]). The caregiver was instructed on the use of the iCare tonometer. The subject's IOP was measured by the caregiver at home at designated time periods for at least 2 consecutive days. Seventeen children (17 eyes) with known or suspected glaucoma and 11 normal children were included. Excellent reliability was obtained by caregivers in 70% of iCare measurements. Mean difference between iCare and GAT in clinic was 2.0 ± 4.0 mm Hg, P = .08. Daily IOP fluctuation occurred in both subjects with glaucoma and normal subjects. In children with known or suspected glaucoma, relative peak and trough IOPs occurred in the early morning (45%) and late evening (43.5%), respectively. Comparison of the peak IOP measured at home vs in the clinic was >6 mm Hg in 5 of 16 subjects (31%) and affected glaucoma management in several subjects. In selected children with glaucoma, home tonometry by iCare rebound tonometry was reliable, easily performed by caregivers, and well tolerated, and offered IOP information valuable in clinical management.

Comparison of iCare tonometer and Goldmann applanation tonometry in normal corneas and in eyes with automated lamellar and penetrating keratoplasty

To compare intraocular pressure (IOP) measurements with Goldmann applanation tonometry (GAT) and iCare tonometry in normal and post-keratoplasty corneas and to assess the influence of central corneal thickness (CCT), corneal curvature (CC), and corneal astigmatism (CA) on IOP. This prospective cross-sectional study included one eye of 101 subjects with normal corneas (58 healthy subjects, 43 glaucoma); and 90 post-keratoplasty patients: 34 penetrating keratoplasties (PK); 20 automated-lamellar-therapeutic keratoplasties (ALTK); 19 Descemet-stripping-automated-endothelial keratoplasties (DSAEK); 17 edematous grafts. All subjects underwent GAT and iCare IOP measurements in random order, and CCT, CC, and CA evaluation. The Bland-Altman method and multivariate regression analysis were used to assess inter-tonometer agreement and the influence of CCT, CC, and CA on IOP. iCare significantly underestimated IOP in all groups compared with GAT (GAT minus iCare of 3.5±3.5 mm Hg, P<0.001), but overestimated IOP in the edematous grafts (GAT minus iCare of -6.5±1.9 mm Hg, P<0.001). In normal corneas, both tonometer measurements were directly related to CCT values; iCare readings appeared inversely related to CC. There was no significant relationship between IOP and CCT, CC and CA in post-keratoplasty eyes, except between CC and iCare measurements for PK eyes. The agreement between GAT and iCare was clinically acceptable in control, ALTK and DSAEK groups, and poor in PK and edematous grafts eyes. In normal corneas, GAT was significantly affected by CCT; iCare was influenced by CCT and CC. The iCare appeared less influenced by corneal edema when compared with GAT. High IOP readings taken with both tonometers in grafts should raise suspicion of true elevated IOP.

Distribution and associations of intraocular pressure in indigenous Australians within central Australia: the Central Australian Ocular Health Study

To determine the distribution and associations of intraocular pressure (IOP) among the indigenous Australian population living in central Australia. Clinic-based cross-sectional study. 1884 individuals living in one of 30 remote communities within the statistical local area of 'Central Australia'. This equated to 36% of those aged ≥20 years and 67% of those aged ≥40 years within this district. Participants aged 20 years or over were recruited as they presented to the eye clinic at each remote community. Of those recruited into the study, 1060 underwent IOP measurement using either a Perkins tonometer (Haag-Streit, Koeniz, Switzerland) or an ICare tonometer (Tiolat Oy, Helsinki, Finland) depending on the availability of equipment. Central corneal thickness (CCT) was also measured using ultrasound pachymetry. The distribution and associations of IOP from the right eye of each participant is presented. Mean IOP was 12.8 mmHg (SD 3.2 mmHg) and CCT was 512 µm (SD 36 µm). IOP was strongly associated with CCT (r(2) = 0.14, t = 3.87; P < 0.0001), showing an increase of 0.4 mmHg with every 10 µm increase in CCT. Furthermore, IOP was strongly associated with age, decreasing by 1.9 mmHg for every decade increase in age, but only for eyes with a CCT above the mean. IOP of indigenous Australians is lower than any other racial group previously published. This may relate to the low CCT readings found among this population. Clinicians will need to bear this in mind when examining indigenous Australians and make appropriate allowances for the measured IOP.

Icare rebound tonometry in children with known and suspected glaucoma

Accurate intraocular pressure (IOP) measurement, important in managing pediatric glaucoma, often presents challenges. The Icare rebound tonometer shows promise for screening healthy children and has been reported comparable with Goldmann applanation in adults with glaucoma. The purpose of this study was to evaluate the Icare tonometer against Goldmann applanation for clinic IOP measurement in pediatric glaucoma. This was a prospective study comparing Icare versus Goldmann tonometry in pediatric glaucoma. Children with known or suspected glaucoma were recruited from scheduled clinic visits. IOP was measured with the Icare tonometer by a clinician and subsequently measured with Goldmann applanation tonometry (GAT) by a different single masked clinician. A total of 71 eyes of 71 children with known or suspected glaucoma were included. IOP by GAT ranged from 9 to 36 mm Hg. Icare readings ranged from 11 to 44 mm Hg. Mean difference between Icare and GAT was 2.3 ± SD 3.7 mm Hg, p < 0.0001. Icare IOPs were within ± 3 mm Hg of GAT in 63%. Icare IOPs were ≥GAT IOPs in 75%. The following factors were not associated with Icare IOPs greater than GAT: child's age, glaucoma diagnosis, strabismus, nystagmus, central corneal thickness, Icare instrument-reported reliability, number of glaucoma surgeries or medications, corneal abnormalities, and visual acuity. IOP by Icare tonometry was within 3 mm Hg of IOP by GAT in 63% and greater than GAT in 75%. This device may be reasonable to estimate IOP in selected children with known or suspected glaucoma whose IOP cannot otherwise be obtained in clinic; however, correlation of Icare IOPs with clinical findings must continue to be considered in each case.

Evaluation of the ICare Rebound Tonometer as a Home Intraocular Pressure Monitoring Device

(a) To investigate whether the ICare rebound tonometer can provide accurate measurements of intraocular pressure (IOP) in the hands of an inexperienced user compared with ICare measurements and Goldmann tonometry by a trained technician and (b) to assess the intrauser reproducibility of IOP measurements and the learning curve among patients using the ICare rebound tonometer. A trained technician used the ICare rebound tonometer to measure the IOP of the right eye of 100 glaucoma patients. The technician then instructed each patient on use of the ICare tonometer. Each patient then measured his/her own pressure using the ICare tonometer. Finally, a different technician, who was masked to both of the earlier readings, measured IOP by Goldmann applanation tonometry. Thirty patients repeated the ICare measurement 3 times (once every 5 min) 20 minutes after the initial IOP measurement. Of the 100 patients, 82 of patient ICare and the technician ICare readings were within 3 mm Hg of each other, and 75 of the patient ICare and Goldmann applanation tonometry measurements were within 3 mm Hg of each other. Intraclass correlations between self-administered ICare measurements 1 and 2, 1 and 3, and 2 and 3 were 0.69, 0.71 and 0.81, respectively. In this study, the ICare rebound tonometer was accurate and reliable in the hands of patients. Patients can easily learn to self-administer this test, possibly allowing for home monitoring of IOP.

The effect of introducing the Icare tonometer in a pediatric ophthalmology clinic

The effect of introducing the Icare tonometer in a pediatric ophthalmology clinic

Suitability and calibration of a rebound tonometer to measure IOP in rabbit and pig eyes

To utilize the Icare tonometer TAO1 for intraocular pressure (IOP) determination in experimental animals. To calculate true IOP calibration functions for rabbit and porcine eyes. Enucleated eyes of 3-year-old healthy experimental rabbits (New Zealand white), and healthy 1 year old experimental pigs (Deutsche Landrasse) were used for the determination of IOP. Manometric (Geuder GmbH, Heidelberg/Germany) and rebound tonometry (Icare tonometer TAO1, Icare, Helsinki/Finland) were used to record IOP in enucleated animal eyes (rabbit n=2, pig n=3). The Icare tonometer TAO1 measurements underestimated true IOP by 37-60% in rabbit eyes and 17-63% in porcine eyes. IOP values obtained by both rebound and manometric tonometry for rabbit and porcine eyes followed a linear regression curve. Linear functions were calculated to correct the Icare tonometer TAO1 measurements to true IOP for both rabbit (p=1.4244p(ic) + 4.2421) and porcine eyes (p=1.0799p(ic) + 5.8557). The Icare tonometer TAO1 can be utilized for IOP determination in rabbit and porcine eyes when measured values are corrected with the appropriate linear function.

Precision and accuracy of the ICare tonometer – Peripheral and central IOP measurements by rebound tonometry

The purpose of this study was to evaluate the ICare tonometers precision and accuracy and the extent to which intraocular pressure (IOP) measurements are influenced by measuring position. This was carried out by comparing the central and peripheral ICare-IOP readings and comparing ICare- with the Goldmann applanation tonometer (GAT)-IOP readings. IOP was measured using the ICare rebound tonometer on the right eye of 40 subjects, straight at the centre of the cornea (CS), straight 2 mm from the nasal and temporal limbus (NS and TS), and in 10 degrees nasally and temporally angled positions measured from the same location as CS (NA and TA). The IOP was also assessed with the GAT. Central IOP (CS) was significantly (p < 0.001) greater than peripheral measurements (NS, TS, NA and TA) by approximately 3-4 mmHg. Centre IOP (CS) significantly overestimated by mean 2 mmHg and the peripheral measurements significantly underestimates approximately 1.4-2 mmHg compared with GAT readings. The ICare tonometer may be useful in a routine clinical setting for IOP screening, but the ICare measurement is not a substitute for the GAT measurement, when a precise and accurate IOP is desired.