Pulsair Non-contact Tonometer Research Articles

A community based study of scenario of glaucoma in Aligarh, India

Background: Glaucoma is the leading cause of irreversible blindness worldwide and is second only to cataracts as the most common cause of blindness overall. In the developing world, the prevalence of glaucoma is expected to rise even more dramatically as the population of adults has doubled within a span of few decades. So this study was done with an objective of finding out the prevalence of glaucoma among adults aged 40 years and above in the field practice area of the Department of Community Medicine, Jawaharlal Nehru Medical College, Aligarh Muslim University, Aligarh.Methods: A cross-sectional study was carried out for the duration of one year. A total of 680 persons were interviewed and examined by a trained ophthalmologist for detailed eye examination including visual acuity, refraction and slit-lamp bio-microscopy, intraocular pressure (IOP) by Keeler Pulsair non-contact tonometer confirm by applanation tonometry, gonioscopy, and dilated fundus examination after ruling out the risk of angle closure. Anderson criteria were used to diagnose glaucomatous visual field defect.Results: In our study population, the IOP of the majority of population lied in 11-15 mm Hg with a mean IOP of 13.42±4.09 mmHg. In regard to optic disc examination, a cup to disc ratio of >0.6 was found in 35 eyes. According to the predefined criteria, a total of 31 subjects were diagnosed as glaucoma in either one or both eyes. The overall prevalence of glaucoma was found to be 4.6% (31/680), with the prevalence of primary open angle glaucoma, primary angle closure glaucoma, normotensive glaucoma and secondary glaucoma as 1.3%, 1.2%, 1.2% and 0.9% respectively.Conclusions: The prevalence of glaucoma is quite high in an elder population of Aligarh. This should warrant more intensive activities, focusing not only on early diagnosis and management of glaucoma but also include strengthening preventive ophthalmic care.

Clinical comparison of Pulsair non-contact tonometer and Goldmann applanation tonometer in Indian population

IntroductionGoldmann applanation tonometer (GAT) is the gold standard for Intraocular Pressure (IOP) measurement but has disadvantage of being contact device and problems with portability. The aim of the study was to compare the Keeler's Pulsair noncontact tonometer (NCT) with GAT in Indian Population. Materials and methodsEighty-one subjects were screened from a Glaucoma clinic of a tertiary care centre in North India. The IOP was measured by Pulsair NCT and GAT after explaining the procedure. Central corneal thickness (CCT) was measured to avoid its bias on IOP readings. The data were analyzed using SPSS software. ResultsThe mean age of subjects was 49.9±8.8 (mean±SD) years. The mean IOP as taken by Pulsair NCT was 15.79±4.07mmHg and that for GAT was 17.02±4.23mmHg (p=0.062). The mean CCT was 0.536±0.019mm. A positive Pearson's correlation coefficient of 0.909 (p=0.0001) was found between the two instruments. Bland and Altmann analysis showed a fair agreement between the two tonometers at lower IOP range. ConclusionPulsair NCT can be used as a screening tool for community practices but is not reliable in the subjects with higher IOP range.

Response to Dr Rao

Sir, We would like to thank Dr A Rao1 for the comments and questions raised regarding the article ‘Combined trabeculotomy and trabeculectomy: outcome for primary congenital glaucoma in a West African population'.2 As she rightly pointed out, our article highlights some of the challenges in the care of children with congenital glaucoma in the developing world. We would want to respond to some of the concerns raised in her letter. It is worth noting that the overall success at the last follow-up for the patients was 79%. It is the probability of success that falls from 66% at 9 months to below 45% at 1 year and beyond. The finding of 63% of the blebs being functional at the last follow up is therefore consistent with the overall success rate. The definition of a well-functioning bleb used was one that is elevated (low to moderately) and diffuse, without any restricting scar, and relatively avascular. The postoperative assessment was done by the same ophthalmologist to ensure consistency. The intraocular pressures of the infants were usually measured at the initial phase of halothane inhalation 1–1.5% when the patients were just sedated. The intraocular pressures of the two eyes determined during the deep phase of anaesthesia were all done preoperatively, and, therefore admittedly, contributed to a relatively lower mean (30.3±8.8) than expected. However, all postoperative measurements were done at the initial phase of halothane inhalation 1–1.5% when the patients were just sedated except two eyes that had the measurements done using Pulsair non-contact tonometer without anaesthesia and in the office setting, but their results were normal. We appreciate the suggestion to exclude intraocular pressures readings taken with Schiotz tonometer in our analysis due to errors associated with its use. However, Schiotz tonometer was the only tool available to us for a period when the Perkins tonometer was faulty. Presently, Schiotz tonometer is no longer in use at our centre. As regards the visual outcome using visual acuity, as indicated in our study, there was paucity of data on postoperative visual acuity and refraction at the last follow-up to make any meaningful statistical analysis. This we acknowledged as a limitation.

Hereditary primary open angle glaucoma: case study of a Nigerian family

Objective: To present a case of hereditary primary open angle glaucoma in a Nigerian family. Method: Six members of an Ibo family from Delta State, Nigeria were interviewed and examined by the authors. Information on age, gender, tribe, history of blindness, eye disease and other medical conditions was recorded. Visual acuity, slit lamp examination and gonioscopy, assessment of intraocular pressure using the pulsair non-contact tonometer and fundoscopy were carried out on the patients where indicated. Results: The report of four generations of hereditary primary open angle glaucoma involving two males and two females is presented. At presentation, the patients were in the end stages of glaucoma with very poor vision—ranging from light perception to no light perception, high intraocular pressure of 31-48mmHg and cup disc ratio of 1.0 in both eyes at relatively young ages. Conclusion: The mode of inheritance was most probably autosomal dominant. It is important to screen family members of patients with primary open angle glaucoma to reduce the problems that result from late presentation. Nigerian Journal of Ophthalmology Vol. 13(2) 2005: 46-48

Ocular leprosy in Nigeria: a survey of an Eku leprosorium

To determine the ocular morbidity, visual disability and potential for blindness in leprosy patients recently released from treatment. In-patients from Eku leprosy settlement were interviewed and examined for ocular disease from leprosy and other causes. They were examined using the Snellen's chart, pentorch, Kowa portable slit-lamp, direct ophthalmoscope and the pulsair non-contact tonometer. The patients were also refracted. In all, 60 inpatients who were recently released from treatment, comprising 39 men (65%) and 21 women (35%), were examined. Fifty-eight patients (96.67%) had ocular symptoms, the most common being blurred vision in 23 patients (38.33%). Nine patients (15%) were blind. Cataract was the most common cause of blindness occurring in three of the nine patients (33.33%). The most common types of ocular lesions were madarosis (31.67%), lagophthalmos (16.67%) and cataract (16.67%). Potentially blinding conditions due to leprosy were seen in 42 patients (70%). The incidence of ocular involvement, blindness and potentially blinding conditions are high in leprosy patients recently released from treatment. Regular ophthalmic evaluation and integration into Vision 2020 programmes are recommended.

Changes in intraocular pressure during prolonged (7-day) head-down tilt bedrest.

To determine the change in intraocular pressure (IOP) due to postural changes in young healthy volunteers. Intraocular pressure was measured using a calibrated Pulsair noncontact tonometer in both eyes of 25 female volunteers in a sitting position and after 1, 3, and 10 minutes in a supine position. In the second part of the experiment (a 7-day -6 degrees head-down tilt [HDT]), IOP (at 8 am, 12 am and 6 pm) and corneal thickness (12 am) were monitored in 8 female volunteers before, during, and after the HDT period. Blood pressure, hematocrit, plasma volume and osmolality, and plasma catecholamines concentrations were also measured. Intraocular pressure was significantly higher in the supine position (16.1 +/- 3.6 mm Hg) than in the sitting position, with a mean pressure difference of 2.23 +/- 2.9 mm Hg after 1 minute, 0.9 +/- 3 mm Hg after 3 minutes, and 1.9 +/- 3.8 mm Hg after 10 minutes in a supine position (P < 0.001). During the period of HDT, IOP values decreased significantly on the fifth day (13.3 +/- 1.6 mm Hg, P = 0.03) and the seventh day (12.7 +/- 1.7 mm Hg, P = 0.02) when compared with IOP in the supine position (14.26 +/- 2 mm Hg). The corneal thickness increased significantly (P < 0.0001) at day 5 (549.25 +/- 48.7 microm) and day 7 (540.31 +/- 46.9 microm) compared with baseline (532.45 +/- 38.6 microm). Two days after the end of the HDT bedrest, the mean supine IOP significantly increased (14.1 +/- 1.8 mm Hg, P = 0.003) and corneal thickness was similar to that found at baseline. The mean decrease of IOP was positively correlated with that of the plasma volume (-10%, r = 0.61, P = 0.02) and negatively correlated with the mean rise of hematocrit (r = -0.5, P = 0.07), variables that are considered to be indirect measures of plasma dehydration. During a 7-day HDT bedrest experiment in healthy women, eyes seemed to compensate the moderate rise of IOP described between a sitting and a supine position, and exhibited a slight and progressive average decrease of 1.3 mm Hg. These physiological modifications could be related to an ocular dehydration or to systemic cardiovascular and hormonal variations during bedrest.

Design of low cost glaucoma screening.

In 1991 the Netherlands Glaucoma Patient Association organized a glaucoma screening survey. This survey was designed to evaluate the effectiveness of a low cost screening setting. During a screening period of 8 days, 1259 subjects over the age of 49 years were examined by a team of non-ophthalmologically trained students. The following screening methods were used: visual field analysis (Henson CFS3000 perimeter), retinal nerve fiber layer photography (Canon non-mydriatic camera), intraocular pressure measurement (Pulsair non-contact tonometer) and determination of the peripheral anterior chamber depth (slitlamp biomicroscope, the van Herick method). In a later stage, subjects with glaucomatous abnormalities in the visual field and/or the photograph were re-examined by a glaucoma specialist using applanation tonometry, gonioscopy, ophthalmoscopy and Humphrey 30-2 visual field analysis. The time taken to conduct the individual screening tests in a subject varied from 1 to 5 min: perimetry took 5 min, photography 2 min, tonometry 3 min and angle-width determination 1 min. Fifty-six (4.4%) subjects showed glaucomatous defects in perimetry and/or photography. Thirty-seven could be re-examined and glaucoma was diagnosed in 16 subjects. Visual field defects and glaucomatous abnormalities in the photograph were confirmed by Humphrey perimetry in 72.7% and 35.7% respectively. Sixty-seven (5.3%) subjects had an intraocular pressure above 21 mm Hg, while no cases of angle closure glaucoma were found in this population. The costs of this screening setting were estimated at F1. 48,60 per screen. A future low cost screening survey might be limited to non-contact tonometry and visual field analysis with the Henson CFS3000 perimeter or a similar device, using suprathreshold testing with a limited number of points. Screening might be performed by non-medically trained employees. The costs of such a screening program may be estimated at F1. 16,- per screen and F1. 1.989,- per glaucoma case using a mobile screening unit (addendum).

Intraocular pressure asymmetry is not a clinically-significant feature when using the PULSAIR non-contact tonometer

Intraocular pressure asymmetry is not a clinically-significant feature when using the PULSAIR non-contact tonometer

Intraocular pressure asymmetry is not a clinically-significant feature when using the PULSAIR non-contact tonometer

This report describes the results of a retrospective analysis of intraocular pressure (IOP) values recorded from the right (R) and left (L) eyes of middle-aged and elderly at-risk but assumed non-glaucomatous subjects. The tensions had been measured using the Keeler PULSAIR noncontact tonometer (NCT) in the course of routine optometric practice when individuals attended for a sight test. These bilateral IOP data were collated on the basis of each subject's gender, (male/female), age (40–59 years/60+ years) and the time of the tonometry assessment (a.m./ p.m.). Wherever possible material was equi-partitioined across these three bipartite variables producing balanced data groupings. Pair-wise testing of R versus L absolute values of pneumoapplanation pressures across any of the balanced data groupings failed to reveal a statistically-significant difference between the paired IOP distributions. There was a consistent but small relative IOP asymmetry (L>R) in these data. Further analysis indicated that this asymmetry only attained borderline statistical significance with respect to subject's age: neither gender nor the time of assessment were statistically significant features, and there were no statistically-significant interactions between any of the three variables. In conclusion, provided that the manufacturer's operating instructions are adhered to, IOP asymmetry is not a clinically-significant feature when using the PULSAIR NCT on a clinical population at risk of developing glaucoma.

Intraocular pressure asymmetry is not a clinically-significant feature when using the PULSAIR non-contact tonometer

Intraocular pressure asymmetry is not a clinically-significant feature when using the PULSAIR non-contact tonometer

Intra-eye pressure range and pulse profiles in normals with the pulsair non-contact tonometer

The difference in intraocular pressure (IOP) between the highest and lowest measurements on an eye with noncontact tonometry (the range) has been reported to be less than 4 mmHg in most normals. The range of IOP to be expected with the Keeler Pulsair in normals over the age of 50 years was determined by analysing the results of IOP recordings on 741 normal individuals. Between 56% and 62% of eyes recorded a range > 4 mmHg and between 4% and 8% a range > 10 mmHg when four pulses per eye were used. Population pulse profile analysis indicated that this was not due to an erroneously high first pulse in a set of four, and that IOP asymmetry previously reported when screening females is due to a generalised tendency for IOPs in right eyes to measure higher than those recorded in the left. The occurrence of a range of IOP recordings up to 10 mmHg in an eye is relatively common with the Pulsair and individuals undergoing glaucoma screening with this instrument should not be referred purely on the basis of a large IOP range.

Intraocular pressure asymmetry in a population tested with the Pulsair non-contact tonometer

Intraocular pressure asymmetry as measured by noncontact tonometry (NCT) was analysed in a population of 874 individuals aged over 50 years. In both males and females the intraocular pressure (IOP) measured in the right eye exceeded that of the left. Pressure asymmetry followed a normal distribution in a population subgroup known to have normal fields, discs and pressures. The 95% confidence intervals for the equation R IOP--L IOP in normals were 0.63+ or -5.46 mmHg when the mean of four pulses per eye were used to calculate the IOP, increasing to 0.80+ or -6.56 mmHg for two pulses per eye (thus expanding the limits by 20%). The range of asymmetry for NCT in normals therefore exceeds that reported for Goldmann applanation tonometry. Asymmetry was greater in females than males. Knowledge of the normal range of IOP asymmetry in each sex will help glaucoma screeners using NCT in their decision as to when to refer. A minimum of four pulses per eye should be used to assess the IOP when screening.

Maximising the sensitivity and specificity of non-contact tonometry in glaucoma screening

Data from a glaucoma screening study involving 88.5% of the population age 50 and over of a single handed general practitioner were reanalysed to determine the effect of altering the protocol for intraocular pressure assessment and the effect of changing the referral threshold. The predictive power of the Keeler Pulsair noncontact tonometer was found to decrease from 22.5% at four pulses per eye to 12.3% when only one pulse per eye was used, with a reduction of sensitivity from 91.7% to 75%. The sensitivity of the same device fell from 91.7% if all patients with an IOP greater than 21 mmHg were deemed as having a positive screen, to 41.6% when only patients with an IOP greater than 26 mmHg were considered for referral. To create a balance between high sensitivity and acceptable predictive power of a positive result in a population where 50% of glaucoma sufferers are known prior to screening, we advise that four pulses per eye should be used with an IOP of greater than 22 mmHg used as the significant finding indicating that the patient required referral.

Incidence of open‐angle glaucoma and screening of the intraocular pressure with a non‐contact tonometer

New equipment for measuring intraocular pressure have been introduced lately. One of these is the Keeler Pulsair non-contact tonometer which uses pressurized air in measurement. It is found to be safe and easy to use in practice, but it seems to give 1.5-2.0 mmHg lower reading than the Goldmann applanation tonometer. This was confirmed by the present study, where non-contact tonometry was controlled by applanation tonometry with a 2-3 week delay between the measurements. However, for screening procedures the accuracy of the apparatus can be considered as sufficient.

IOP elevation in different phases of sleep

Large and significant increases in intraocular pressure (IOP) have previously been demonstrated after as little as 30 minutes of sleep.12 The present experiment tests the hypothesis that the lack of eye movements during sleep is responsible for this increase in IOP. Nine subjects slept in the laboratory on two separate nights. IOP was measured (with subjects in the supine position) using a Keeler Pulsair noncontact tonometer. Eye movements were monitored using electro-oculography. Subjects were woken from sleep after 60–90 minutes, on one night when they were in rapid eye movement (REM) sleep, and on one night when they were not. IOP increased significantly on both nights, but the differences between these increases was not significant. Thus, mechanical factors associated with lack of eye movements do not appear to contribute to the increase in IOP after sleep.

Non-contact tonometry: an ideal method for mass screening

We evaluated one of the new non-contact tonometers, the Pulsair non-contact tonometer, to assess its accuracy and reliability. Measurements on 101 eyes were used to assess its accuracy against Goldmann tonometry measurements, and another 24 eyes were used to assess its reliability (reproducibility). The results showed the instrument to be highly accurate and reliable in measurement.

Evaluation of the Keeler Pulsair non-contact tonometer.

The recently-introduced Pulsair non-contact tonometer (Keeler Instruments, Inc, Broomall, PA) was evaluated against the Goldmann applanation tonometer in cannulated post mortem human eyes, and in living subjects at three clinical centers. Statistical analysis of the findings revealed strong linear relationships between Goldmann or manometric and Pulsair intraocular pressure readings, with correlation coefficients ranging from 0.79 to 0.97. However, with the Pulsair reading as the dependent variable, the slope of the relationship in each case was significantly less than 1.0 (range 0.65 to 0.83), while the intercept was positive (range 1.31 to 2.33 mmHg). Thus, the Pulsair tended to read low at intraocular pressure above the normal range. Conversion factors and a calibration table allowing intraocular pressure estimates more comparable to Goldmann tonometry using the current (J-series) Pulsair are provided herein. A calibration algorithm could be integrated into the circuitry of future production models of the Pulsair instrument.