Contribution to the Theory and Practice of Tonometry*

Friedenwald, Jonas S.

doi:10.1016/s0002-9394(37)90425-2

Cited by 400 publications

(155 citation statements)

References 6 publications

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“…It has been suggested that age-related increase in corneal 'stiffness' may induce a further measurement error with GAT. 27 DCT measurements may be less affected by this change in corneal biomechanics.…”

Section: Discussionmentioning

confidence: 99%

Influence of age, central corneal thickness, and quality score on dynamic contour tonometry

Jordão

Lupinacci

Ferreira

et al. 2008

Eye

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Aims To compare the IOP measurements obtained with dynamic contour tonometry (DCT) and Goldmann applanation tonometry (GAT), and to analyse the influence of central corneal thickness (CCT) and age on both measurements, and the influence of the quality score on DCT readings. Methods A total of 500 healthy subjects with no prior history of glaucoma or ocular hypertension (age: 7-86 years) were consecutively recruited. GAT, DCT, and CCT measurements were obtained from both eyes of each individual, in this order, by three observers. The mean of five CCT measurements was used for analysis. DCT measurements were accepted when quality scores varied between 1 (higher quality) and 3 (lower quality). Results Mean DCT measurements were 3.2 mmHg higher than GAT readings. CCT values varied between 449 and 653 lm. IOP measured by GAT correlated strongly with CCT (r 2 ¼ 0.28, P ¼ o0.001), whereas DCT readings correlated poorly with CCT (r 2 ¼ 0.01, P ¼ 0.017). Both DCT (r 2 ¼ o0.01, P ¼ 0.044) and GAT (r 2 ¼ 0.01, P ¼ o0.001) measurements correlated poorly with age. Bland-Altmann analysis revealed disagreement between DCT and GAT readings, with 95% confidence intervals of ±6.7 mmHg. Quality scores for DCT measurements were 1 (n ¼ 369, 36.9%), 2 (n ¼ 340, 34.0%), and 3 (n ¼ 291, 29.1%). DCT readings with quality score of 3 (18.8 ± 3.4 mmHg) were significantly higher than those with quality scores of 1 (16.7±2.9 mmHg) and 2 (17.4±2.9 mmHg; P ¼ o0.001). Conclusions DCT is not influenced by CCT, unlike GAT. Both DCT and GAT measurements are not influenced by age. DCT measurements with lower quality scores are associated with higher readings.

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Section: Discussionmentioning

confidence: 99%

Influence of age, central corneal thickness, and quality score on dynamic contour tonometry

Jordão

Lupinacci

Ferreira

et al. 2008

Eye

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“…T he present technology used to measure intraocular pressure (IOP) was developed some decades ago: Schiö tz (Friedenwald 1937), Goldmann (Goldmann & Schmidt 1957) , Mackay Marg (Mackay & Marg 1959) and the non-contact method (Fisher et al 1988). The Schiö tz tonometer, which is nearly 100 years old, is still one of the methods most commonly used today by general practitioners.…”

mentioning

confidence: 99%

A new induction‐based impact method for measuring intraocular pressure

Kontiola

2000

Acta Ophthalmologica Scandinavica

189

183

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ABSTRACT.Purpose: An improved induction-based impact method for measuring intraocular pressure is presented. Methods: A light probe containing a permanent magnet is launched towards the eye using a solenoid. The probe hits the eye and bounces back. The same solenoid, inside which the probe moves, is used to detect the movement and impact of the probe, because the moving magnet induces voltage in the solenoid. In the clinical study, the Goldmann applanation tonometer was used as a standard. Handheld and fixed tonometers were also compared by means of measurements in pressurized pig eyes. Results: At a low intraocular pressure (IOP), there is a longer impact time than at a high IOP. A handheld tonometer causes more variation in impact times, especially at low intraocular pressure (IOP), than a fixed tonometer. Conclusions: The new induction-based impact method can be used to measure IOP. When a fixed tonometer is used, there is less variation in impact times.

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“…Dexamethasone responders group of animals were then treated with topical forskolin in situ gel (0.25 mg; 25 µl of 1% (w/v) suspension) and suspension (0.5 mg; 50 µl of 1% (w/v) suspension) vehicle at the indicated days and IOP measured. IOP was measured using a Schiötz tonometer (32)(33)(34), by the same operator, using the same tonometer after instilling a drop of xylocaine (a local anesthetic, 4%) into each eye of rabbits. All the measurements were made three times at each interval, and a mean of these was taken.…”

Section: Pharmacodynamic Studiesmentioning

confidence: 99%

Dual-Drug Delivery System Based on In Situ Gel-Forming Nanosuspension of Forskolin to Enhance Antiglaucoma Efficacy

2010

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Abstract. The present study was designed to improve the bioavailability of forskolin by the influence of precorneal residence time and dissolution characteristics. Nanosizing is an advanced approach to overcome the issue of poor aqueous solubility of active pharmaceutical ingredients. Forskolin nanocrystals have been successfully manufactured and stabilized by poloxamer 407. These nanocrystals have been characterized in terms of particle size by scanning electron microscopy and dynamic light scattering. By formulating Noveon AA-1 polycarbophil/poloxamer 407 platforms, at specific concentrations, it was possible to obtain a pH and thermoreversible gel with a pH gel /T gel close to eye pH/ temperature. The addition of forskolin nanocrystals did not alter the gelation properties of Noveon AA-1 polycarbophil/poloxamer 407 and nanocrystal properties of forskolin. The formulation was stable over a period of 6 months at room temperature. In vitro release experiments indicated that the optimized platform was able to prolong and control forskolin release for more than 5 h. The in vivo studies on dexamethasone-induced glaucomatous rabbits indicated that the intraocular pressure lowering efficacy for nanosuspension/hydrogel systems was 31% and lasted for 12 h, which is significantly better than the effect of traditional eye suspension (18%, 4-6 h). Hence, our investigations successfully prove that the pH and thermoreversible polymeric in situ gel-forming nanosuspension with ability of controlled drug release exhibits a greater potential for glaucoma therapy.

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Contribution to the Theory and Practice of Tonometry*

Cited by 400 publications

References 6 publications

Influence of age, central corneal thickness, and quality score on dynamic contour tonometry

Influence of age, central corneal thickness, and quality score on dynamic contour tonometry

A new induction‐based impact method for measuring intraocular pressure

Dual-Drug Delivery System Based on In Situ Gel-Forming Nanosuspension of Forskolin to Enhance Antiglaucoma Efficacy

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