Goldmann applanation tonometry after myopic photorefractive keratectomy

Rosa, Nicola; Cennamo, Giovanni; Breve, Maria Angelica; Rana, Abhilasha

doi:10.1034/j.1600-0420.1998.760508.x

Cited by 42 publications

(37 citation statements)

References 9 publications

(15 reference statements)

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“…On the contrary, Rosa et al 10 and Montés-Micó and Charman 12 supported the hypothesis that the decrease in thickness and the decrease in curvature might be the reason behind this underestimation.…”

Section: Discussionmentioning

confidence: 56%

“…Several authors studying the IOP after refractive surgery found the measurements obtained with both GAT and NCT [10][11][12][13][14][15][16] unreliable, and proposed different ways to overcome this problem, such as correcting factors, 10,11,13 or different techniques, such as pneumotonometry, dynamic contour tonometry or peripheral measurements. [1][2][3]5,17 The possible causes of the decrease of the measured postoperative IOP with GAT and NCT are debated.…”

Section: Discussionmentioning

confidence: 99%

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Accuracy of Schiotz Tonometry in Measuring the Intraocular Pressure After Corneal Refractive Surgery

Rosa

Lanza

Cennamo

et al. 2008

Journal of Optometry

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PURPOSE:To test the accuracy of Schiotz tonometry (ST) in patients that underwent photorefractive keratectomy (PRK). METHODS: 175 eyes previously treated with PRK for myopia, myopic astigmatism or mixed astigmatism, with a mean preoperative spherical equivalent (SE) of -4.27±2.83 diopters (range: -13 to -0.25 diopters), had their intraocular pressure (IOP) measured, at least 3 months after PRK, with Goldmann applanation tonometry (GAT) and ST with both 5.5-g and 10-g load and also utilizing the Friedenwald nomogram. These measurements were retrospectively compared to the IOP readings obtained with GAT before surgery. RESULTS: Before PRK the mean IOP, as measured with GAT, was 14.7±2.63 mmHg. After PRK, the mean IOP readings were 10.9± 2.85 mmHg (P<0.001) with GAT, 13.58±3.42 mmHg (P<0.001) with 5.5-g load ST; 12.32±3.67 mmHg (P<0.001) with 10-g load ST, and 16.19±5.63 mmHg (P<0.001) with the Friedenwald nomogram. The different methods showed a poor agreement, the worst one being between GAT before surgery and the Friedenwald nomogram (r 2 =0.05). Moreover, ST with both 5.5 g and 10 g load showed an underestimation (more pronounced for the 10-g than for the 5.5-g load) that increased with the amount of treatment. CONCLUSIONS: Although ST with a 5.5 g load seems to be more accurate to measure the true IOP in patients that have undergone PRK compared to the Goldmann technique, it cannot be considered to be accurate in a sufficient number of cases. IOP measurement after refractive surgery is still a problem, and further studies are needed to overcome it. RESUMEN OBJETIVO:Evaluar el grado de precisión de la tonometría de Schiotz (TS) en pacientes que se han sometido a una operación de queratectomía fotorrefractiva (en inglés, PRK). MÉTODOS: Se midió la presión intraocular (PIO) de 175 ojos que habían sido previamente tratados con PRK de miopía con o sin astigmatismo, con una refracción preoperativa (equivalente esférico, o SE) de -4.27±2.83 (rango: -13 a -0,25 dioptrías). Las medidas, realizadas al menos transcurridos 3 meses desde la operación de PRK, utilizaron las técnicas de tonometría por aplanación de Goldmann (TAG) y la TS, esta última con cargas de 5,5 g, de 10 g y utilizando un nomograma de Friedenwald. Estas medidas se compararon retrospectivamente a los valores de PIO obtenidos con TAG antes del procedimiento quirúrgico. RESULTADOS: Antes de la PRK, la PIO media obtenida con TAG fue de 14,7±2,63 mmHg. Después de la PRK, la PIO resultante fue de 10,9±2,85 mmHg (P<0,001) con TAG; de 13,58±3,42 mmHg (P<0,001) con TS y una carga de 5,5 g; de 12,32±3,67 mmHg (P<0,001) con TS y una carga de 10 g; y de 16,19±5,63 mmHg (P<0,001) con TS y utilizando un nomograma de Friedenwald. Los resultados revelan una mala concordancia, siendo las medidas con TAG antes de la operación y las que utilizaron un nomograma de Friedenwald (r 2 =0,05) las que produjeron la peor concordancia. Además, la TS tanto con carga de 5,5 g como con carga de 10 g produjeron estimaciones de la PIO por debajo del valor real (con carga de ...

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Section: Discussionmentioning

confidence: 56%

Section: Discussionmentioning

confidence: 99%

Accuracy of Schiotz Tonometry in Measuring the Intraocular Pressure After Corneal Refractive Surgery

Rosa

Lanza

Cennamo

et al. 2008

Journal of Optometry

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“…The difference between CCT Pach-Pen and CCT estimated from the expected ablanation of the excimer laser was defined as DCCT. Due to the GAT-limitation of only measuring IOP exceeding 12.5 mmHg in this model, together with an expected underestimation after laser correction [3,17,25,29], all measurements were done at IOP VC = 30 mmHg.…”

Section: Methodsmentioning

confidence: 99%

“…A well-known consequence of laser refractive surgery for myopia is an underestimation of the IOP measured with GAT [17,25,27]. However, the causes are not fully understood.…”

Section: Introductionmentioning

confidence: 97%

Underestimation of intraocular pressure after photorefractive keratectomy: a biomechanical analysis

et al. 2006

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Excimer laser surgery, to correct corneal refraction, induces changes in corneal thickness and curvature. Both factors can cause measurement errors when determining intraocular pressure (IOP). This study evaluates effects of photorefractive keratectomy (PRK) on IOP measurements, using Goldmann applanation tonometry (GAT) and Applanation resonance tonometry (ART), in an in vitro model. Six porcine eyes was enucleated and pressurised to a constant IOP=30 mmHg. After removal of the epithelium, the eyes were PRK-treated for a total of 25 dioptres. The measured IOP decreased 13.2 mmHg for GAT and 9.0 mmHg for ART. The total underestimation by GAT was larger than for ART, and a part of the ART underestimation (3.5 mmHg) was assigned to sensitivity to the change in corneal surface structure resulting from the removal of epithelium. The flat contact probe of GAT, as compared with the convex tip of ART, provided explanation for the difference in IOP measurement error after PRK.

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“…22 Regarding the effect of refractive surgery on GAT IOP measurements, there seems to be an agreement on the apparent IOP-lowering effect of the different modalities of surgery. [23][24][25][26][27] Kirwan et al 26 found that the mean GAT IOP decreased 3.7±2.3 mmHg following LASIK, and a similar decrease was observed following LASEK. Moreover, photorefractive keratectomy (PRK) seems to induce a smaller GAT IOP underestimation than LASIK.…”

Section: Applanation Tonometers Goldmann Tonometer (Haag Streit Koenmentioning

confidence: 99%

Modalities of Tonometry and their Accuracy with Respect to Corneal Thickness and Irregularities

Moraes

Prata

Liebmann

et al. 2008

Journal of Optometry

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Recent advances in tonometry have led to the development of a number of devices with differing clinical applications. Their role in cases of abnormal corneal thickness and surface irregularities is particularly important, as inaccurate estimation of the true intraocular pressure (IOP) in such cases may lead to suboptimal evaluation. The purpose of the present review was to evaluate the accuracy of the most widely used devices in cases of corneal thickness and surface irregularities, based on a survey of the published literature. The analysis was based on a Medline search focusing mainly on papers that have evaluated the devices' accuracy with respect to corneal thickness and irregularities. Nine device types (Goldmann tonometer, Tono-Pen, Perkins tonometer, Ocular Response Analyzer, non-contact tonometer, pneumatonometer, I-Care rebound tonometer, Pascal dynamic contour tonometer (DCT) and Phosphene tonometer) were described in detail. Moreover, the physical principles and major utility of each tonometer were compared. Each of the many different commercially available tonometers has specific advantages and disadvantages. New non-invasive technologies are getting closer to a precise estimation of the true IOP. However, among all tonometers, none is highly accurate when both corneal thickness and surface irregularities are present. Fifty years after its development, Goldmann tonometry remains the gold standard to which all other devices are compared. RESUMENAvances recientes en el campo de la tonometría han propiciado el desarrollo de diversos dispositivos con diferentes aplicaciones clíni-cas. Resulta de particular importancia el papel que juegan en el caso de espesores corneales anormales o en presencia de irregularidades en la superficie de la córnea, puesto que, en esos casos, una medida imprecisa de la presión intraocular (PIO) real puede traer como consecuencia una valoración incorrecta del caso. El objetivo de esta revisión es evaluar el grado de precisión de los dispositivos más utilizados hoy en día en casos en los que existen irregularidades en la superficie de la córnea o en el espesor corneal. Para ello, se llevó a cabo una búsqueda de datos entre los artículos publicados. El análisis estuvo basado en una búsqueda bibliográfica realizada dentro de Medline, centrándose principalmente en aquellos artícu-los científicos que habían estudiado el grado de precisión del dispositivo en función del espesor corneal del paciente y de la presencia o no de irregularidades corneales. Se describen en detalle nueve tipos de dispositivos: tonómetro de Goldmann, Tono-Pen, tonómetro de Perkins, Ocular Response Analyzer, tonómetro sin contacto, neumotonómetro, tonómetro de rebote I-Care, tonómetro de contorno dinámico Pascal y tonómetro de fosfeno. Además, se presentan de forma comparada los principios físicos en los que está basado cada tonómetro y las situaciones en las que cada uno resulta de mayor utilidad. Cada uno de los distintos tonómetros disponibles en el mercado presenta ventajas y desventajas respecto...

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Goldmann applanation tonometry after myopic photorefractive keratectomy

Cited by 42 publications

References 9 publications

Accuracy of Schiotz Tonometry in Measuring the Intraocular Pressure After Corneal Refractive Surgery

Accuracy of Schiotz Tonometry in Measuring the Intraocular Pressure After Corneal Refractive Surgery

Underestimation of intraocular pressure after photorefractive keratectomy: a biomechanical analysis

Modalities of Tonometry and their Accuracy with Respect to Corneal Thickness and Irregularities

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