A Noncontact Applanation Tonometer

Forbes, Max; Picó, Guillermo; Grolman, Bernard

doi:10.1001/archopht.1974.03900060140012

Cited by 95 publications

(32 citation statements)

References 1 publication

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“…NCT readings are highly correlated with those of GAT in the normal IOP range. [12][13][14] However, little is known about the impact of CCT on the NCT measurements. Recently, the ocular blood flow tonometer (OBFT) has been introduced as another option for measuring IOP and pulsatile ocular blood flow.…”

Section: Introductionmentioning

confidence: 99%

Varying Effects of Corneal Thickness on Intraocular Pressure Measurements with Different Tonometers

Liu

Hsu

2004

Eye

109

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Aims To compare the intraocular pressure (IOP) measurements using the Goldmann applanation tonometer (GAT), noncontact tonometer (NCT), and ocular blood flow tonometer (OBFT), and to evaluate the effects of varying central corneal thickness (CCT) on the readings. Methods Ultrasound pachymetry and tonometry were performed on 170 eyes. Using the corrected GAT values that took CCT into account as the standard, we calculated the NCT and OBFT measurement errors related to the CCT variable by a linear regression model. Group comparisons were performed with the v 2 test and one-way ANOVA test. The correlation between the various tonometer measurements was analysed by Pearson's correlation method. Results Both the NCT (r ¼ 0.872, Po0.001) and OBFT measurements (r ¼ 0.861, Po0.001) were highly correlated with the GAT measurements. IOP measurements using the three tonometers were all correlated with CCT (all Po0.001), with the NCT measurements showing the greatest regression coefficient (b ¼ 0.063, r ¼ 0.650) and the GAT measurements the least (b ¼ 0.037, r ¼ 0.496). A linear regression model indicated that a 10 lm change in CCT resulted in a NCT measurement deviation of 0.47-0.98 mmHg and an OBFT measurement deviation of 0.29-0.81 mmHg.Conclusion Pressure readings with the GAT, NCT, and OBFT are all affected by CCT, with the NCT being the one most affected and the GAT the least. Our findings suggest CCT an essential variable to consider in interpreting IOP readings, especially for the NCT measurements.

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Section: Introductionmentioning

confidence: 99%

Varying Effects of Corneal Thickness on Intraocular Pressure Measurements with Different Tonometers

Liu

Hsu

2004

Eye

109

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“…Em sua primeira publicação sobre a TNC, Forbes (3) alertava para o chamado efeito "squeezer", no qual a primeira medida da Po mostravase menor que as seguintes devido à ansiedade do paciente com um conhecimento prévio do exame, fato também descrito por Vernon. Uma limitação do presente estudo é o tamanho da amostra, o que provoca uma diminuição do poder dos testes estatísti-cos para verificarem-se variações muito pequenas de pressões intra-oculares, no entanto, o tamanho da amostra é maior do que o necessário para detectar-se variações maiores ou iguais a 1 mmHg, isto é, valores que poderiam ser considerados relevantes do ponto de vista clínico.…”

Section: Discussionunclassified

“…O primeiro estudo clínico sobre TNC foi descrito em 1973 por Forbes (3) e ressaltava suas vantagens, como a aplicabilidade para programas de rastreamento e a não necessidade da utilização de colírios. Outras vantagens apontadas são a realização por pessoal não médico e o menor risco de Descritores: Tonometria de não-contato; Tonometria de Goldmann; Pressão intra-ocular; Anestésico; Glaucoma Tonometria de não-contato: variação com medidas repetidas com e sem colírio anestésico contaminação.…”

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Tonometria de não-contato: variação com medidas repetidas com e sem colírio anestésico

Tavares¹,

Melo²,

Motta³

et al. 2003

Arq. Bras. Oftalmol.

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Objetivos: Avaliar a influência da utilização do colírio anestésico, bem como verificar o comportamento da medida da pressão intra-ocular (Po) com a adaptação (aprendizado) do paciente à tonometria de não-contato (TNC). Materiais e métodos: Estudo clínico randomizado duplo-mascarado em que se avaliaram 24 olhos de 24 voluntários normais, sem experiência prévia com a TNC, divididos em 2 grupos: grupo I (TNC com instilação prévia de colírio anestésico seguido de tonometria de aplanação de Goldmann (TAG)) e grupo II (TNC com instilação prévia de colírio placebo seguido de TAG). As medidas da Po foram realizadas em três visitas com intervalo de um a três dias aproximadamente no mesmo horário. Resultados: Constatou-se a Po por meio da TAG como a única variável preditora estatisticamente significante (p < 0,05) para a TNC. Não houve diferença na variação da Po entre os grupos (p = 0,884), tampouco entre as visitas (p = 0,144). Houve melhor correlação entre a TNC e TAG no grupo II em relação ao grupo I em todas as visitas, porém esta diferença não se mostrou estatisticamente significante (p = 0,4853). Conclusões: A utilização de anestésico tópico e a adaptação de indivíduos normais ao exame de tonometria de não-contato não demonstraram influência significante sobre a medida da Po obtida por este método.

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“…8 On repeated applanation in 18 normal eyes of 10 patients involving 144 sets of four pulses, Piltz found that a range of >4 mmHg in a set of four was found in only 12.5% of sets. No men tion of the age or sex of the patients was made and as each eye had eight sets of readings, individuals would be con siderably experienced in NeT as data collection proceeded.…”

Section: Discussionmentioning

confidence: 99%

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

Vernon

1993

Eye

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SUMMARYThe difference in intraocular pressure (lOP) between the highest and lowest measurements on an eye with non contact tonometry (the range) has been reported to be less than 4 mmHg in most normals. The range of lOP to be expected with the Keeler Pulsair in normals over the age of 50 years was determined by analysing the results of lOP 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 analy sis indicated that this was not due to an erroneously high first pulse in a set of four, and that lOP asymmetry pre viously reported when screening females is due to a generalised tendency for lOPs in right eyes to measure higher than those recorded in the left. The occurrence of a range ofIOP recordings up to 10 mmHg in an eye is rela tively common with the Pulsair and individuals under going glaucoma screening with this instrument should not be referred purely on the basis of a large lOP range.Non-contact tonometry (NeT) samples the ocular pulse by causing a momentary applanation event on the cornea with a ramped jet of air. In order to estimate the mean intraocular pressure (lOP) in an eye, a number of NeT pulses are used. The Keeler Pulsair NeT was introduced in 1988.1 We have reported previously on the effect of altering the number of pulses used to estimate the lOP in a population at risk of glaucoma,2 and the asymmetry to be expected in normal individuals when using the Keeler Pul sair NeT. 3 In the latter study we demonstrated that, when screening for glaucoma, normal individuals record an lOP which is on average 0.63 mmHg higher in the right eye than the left eye when the right eye is tested first. The effect is marked in females, reaching a level of statistical significance of p

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A Noncontact Applanation Tonometer

Cited by 95 publications

References 1 publication

Varying Effects of Corneal Thickness on Intraocular Pressure Measurements with Different Tonometers

Varying Effects of Corneal Thickness on Intraocular Pressure Measurements with Different Tonometers

Tonometria de não-contato: variação com medidas repetidas com e sem colírio anestésico

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

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