Alcohol soaking damages applanation tonometer heads

Goldmann Applanation Tonometry: Comparison of Intraocular Pressure Values Obtained with Disposable Tip and Conventional Applanation Prism in the Population without Clinical Signs of Glaucoma

Aim

Comparing intraocular pressure (IOP) measurements using Goldmann applanation prism and TonoSafe® in the population without signs of glaucoma.

Material and methods

Patients with no ocular pathologies, except ametropia (until ± 4 D) or IOP of <30 mm Hg without signs of glaucoma by optic disc structural analysis by fundus biomicroscopy. The IOP was measured sequentially using the traditional cone and the TonoSafe®, according to a randomization list to determine which device would be used first. The measurements from the right and left eyes were compared separately. Since there was no statistical difference, both eyes were considered in this study.

Results

A total of 385 eyes of 194 patients with a mean age of 66.4 ± 11.2 years old were included. The mean IOP with conventional prism was 14.2 ± 3.6 and 14.3 ± 3.6 mm Hg with TonoSafe®. Differences were not statistically significant by the Wilcoxon test (p = 0.3). The median was 14.0 mm Hg for both groups. The mean difference between measurements was 0.04 mm Hg, with the median equal to zero. There was no statistical difference in IOP readings according to which device was the first measurement.

Conclusion

No statistical difference was found in IOP was measured with conventional prism or TonoSafe® in the population without signs of glaucoma.

Clinical significance

The data provided by our study support the efficacy and safety of the disposable tonometer compared to the Goldman tonometer in measuring IOP in patients without glaucoma.

How to cite this article

Soares PHA, Santos RDO, Filho CRADM, et al. Goldmann Applanation Tonometry: Comparison of Intraocular Pressure Values Obtained with Disposable Tip and Conventional Applanation Prism in the Population without Clinical Signs of Glaucoma. J Curr Glaucoma Pract 2023;17(2):75-78.

Economic and Environmental Impact of Single-use Plastics at a Large Ophthalmology Outpatient Service

PRéCIS:: The use of disposable tonometer prisms and gonioscopy lenses at a large ophthalmology outpatient service incurs significant financial and environmental waste that may not be justified given the limited data surrounding arguments for their use.

PURPOSE

To quantify the economic and environmental burden of single-use plastics from an ophthalmology outpatient service at a large tertiary hospital and describe the relative value and evidence for the safety of disposable versus nondisposable tonometer prisms and gonioscopy lenses.

METHODS

The total number of single-use applanation tonometer prisms and gonioscopy lenses used per year at Boston Medical Center (BMC) was estimated, and the average dollars spent and plastic waste generated in kilograms per year were then determined. These values were compared with the total spending and waste that would be produced if the clinic were to use nondisposable tonometer prisms and gonioscopy lenses exclusively.

RESULTS

Single-use tonometer prisms cost an average of $70,282 per year and produce ~100.8 kg of plastic waste per year at BMC. Single-use gonioscopy lenses cost ~$9,040 per year and produce 8.8 kg of plastic waste per year at BMC. An excess of $65,185 and 109.6 kg of plastic waste could be avoided each year by only using nondisposable tonometer prisms and gonioscopy lenses at the BMC ophthalmology outpatient service.

CONCLUSIONS

Single-use plastics in ophthalmology outpatient services generate significant environmental waste and financial cost compared with nondisposable instruments. This cost may outweigh the benefits of these instruments given the limited data surrounding arguments for their use.

Guidelines and Recommendations for Tonometry Use during the COVID-19 Era

The novel coronavirus disease COVID-19 caused by Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) has resulted in a substantial change in eye care and clinical practice. There has been conflicting information and weak evidence on the virus's transmission through tears. Yet, virus detection on cornea and conjunctiva surface as a gateway for infection is not well-studied. Moreover, there have been no reported cases of SARS-CoV-2 transmission through tonometry to date. Thus, this uncertainty has urged this review on evidence-based guidelines and recommendations on tonometer use in the COVID-19 era. The aim of this article is to provide ophthalmologists with recommendations for tonometry practice based on current evidence and best practice guidelines.

A comparison of applanation tonometry using conventional reusable goldmann prisms and disposable prisms

PURPOSE

To determine the agreement between intraocular pressure (IOP) measurements using conventional Goldmann applanation tonometry (GAT) and Tonosafe disposable prisms, and also to provide a comprehensive cost analysis of the use of both types of prisms

METHODS

: In this prospective observational study, 198 eyes of 100 glaucoma patients had their IOPs measured by 5 consultant ophthalmologists. Data were analyzed using the Bland-Altman method of differences, and correlation was measured using the Pearson coefficient. An analysis of the cost incurred using the 2 methods over a 6-month period was performed.

RESULTS

The majority were Chinese (82%), with a male preponderance (57%). The range of IOPs as measured by GAT was 4 to 34 mm Hg. Using the Bland-Altman method to compare GAT and disposable prisms, the bias was 0.2 mm Hg. Tonosafe overestimated the IOP by 0.2 mm Hg in the right eye and underestimated it by 0.2 mm Hg in the left eye. The Tonosafe IOP correlated well with GAT, with a Pearson coefficient of correlation(r) of 0.91 (P<0.0005) for the right eye and 0.92 (P<0.0005) for the left eye, respectively. For those with GAT IOP≥21 mm Hg (n=26), Tonosafe underestimated the IOP by 0.35 mm Hg. The cost incurred by Tonosafe prisms was approximately 8 times that of GAT, but the cost differential reverses when GAT had to be replaced after every 100 cycles of disinfection.

CONCLUSIONS

We found a good correlation between Tonosafe prisms and conventional GAT in measuring the IOP. Tonosafe prisms may be of use, especially if the risk of transmission of infection is high. However, cost may limit its more widespread use.

A comparison of clinical performance between disposable and Goldmann tonometers

PURPOSE

Applanation tonometry as performed in routine clinical practice is a significant potential vehicle for cross-infection particularly in an emergency eye care setting. The aim of this study is to evaluate the accuracy and reliability of three single-use devices (Tonoshield, Tonosafe, Tonojet) as an alternative to standard Goldmann prisms in an emergency eye department.

METHODS

All patients attending the eye casualty at the Manchester Royal Eye Hospital for a period of 4 months who required intraocular pressure measurement were eligible for this prospective study. Exclusion criteria were: age below 18 years, corneal anomalies that might affect measurement, and refusal to participate. After taking informed consent, the patient was examined by one experienced nurse practitioner, who measured the intraocular pressure three times. In the first part of the study, we compared the standard Goldmann prism vsTonoshield and Tonosafe prisms, while for the second part of the study we used standard Goldmann, Tonosafe, and Tonojet prisms. Agreement and repeatability tests were carried out on separate samples.

RESULTS

Tonosafe and Tonojet correlated well with standard Goldmann tonometry (P<0.001), while the measurements obtained with Tonoshield were higher, especially for raised intraocular pressure measurements. Tonojet and Tonosafe measurements were more reproducible than Tonoshield measurements.

CONCLUSIONS

This study shows that Tonosafe and Tonojet are accurate and reliable alternatives to standard Goldmann tonometry.

Corneal epithelial alterations resulting from use of chlorine-disinfected contact tonometer after myopic photorefractive keratectomy

OBJECTIVE

This study aimed to describe a previously unreported complication associated with the use of chlorine-disinfected applanation tonometer heads for intraocular pressure measurement after excimer laser photorefractive keratectomy.

DESIGN

Two retrospective case reports.

PARTICIPANTS

Two patients underwent, respectively, a 7-diopter and a 4-diopter myopic excimer laser correction in their first eye 2 weeks apart. Complete epithelial closure of the ablated area was observed by biomicroscopy in the first-week examination.

INTERVENTION

Four weeks after photorefractive keratectomy, a complete ophthalmic examination was performed. Goldmann applanation tonometry was performed bilaterally after thoroughly rinsing and drying the tonometer biprism, which had been immersed regularly in a chlorine 5000-parts per million solution.

MAIN OUTCOME MEASURES

Slit-lamp examination and corneal topographic surface regularity were measured.

RESULTS

A few minutes after applanation tonometry, both patients reported ocular discomfort in the excimer laser-treated eyes, whereas the untreated fellow eyes were painless. Punctate corneal lesions and superficial epithelial cell clumping were present in the first patient's treated eye, predominantly in the inferior aspect of the applanated cornea. Visual inspection showed a normal tonometer tip. In the second patient's treated cornea, a focal epithelial defect was identified biomicroscopically, which corresponded to the steeper region within the ablation zone on the videokeratograph. In this case, crystal deposits were found on the tonometer tip. The epithelial alterations resolved without sequelae in both cases.

CONCLUSIONS

Disinfecting solutions of chlorine can cause crystal deposit formation on the tonometer head. Applanation tonometry after repeated disinfection with chlorine solutions appears to have the potential for disrupting the epithelial layer of the healing cornea. Covered contact tonometry or noncontact tonometry should be evaluated as alternative methods to chemically disinfected contact tonometry for intraocular pressure measurement after excimer laser surgery, especially during the first postoperative month.

Goldmann applanation tonometry using sterile disposable silicone tonometer shields

PURPOSE

Placement of a sterile single-use cover over the tonometer tip may be a convenient and safe alternative method to repeated chemical disinfection. This study was undertaken to evaluate the accuracy and performance of Goldmann applanation tonometry using a sterile disposable silicone tonometer shield over the biprism tip.

METHODS

The same investigator measured intraocular pressure in 120 eyes with and without the shield. The eyes were tested randomly first with either the uncovered or the covered tonometer to control for the possible effects of repeated tonometry influencing measurement differences. Readings were recorded independently in a masked fashion.

RESULTS

The intraocular pressure measurements evaluated with the silicone shield caused an average overestimation of the true intraocular pressure of 1.9 +/- 1.9 mmHg (P = 0.0001). Covered and uncovered readings correlated well (r = 0.91, P = 0.0001). The sensitivity and specificity of the covered tonometry in detection intraocular pressures of 21 mmHg or higher (as measured without the shield) were 96.3% and 68.8%, respectively. Minor distortions of the normal-appearing fluorescein bands were seen in 5% of the tonometries, and the shield had to be replaced because of bubbles or wrinkles on the applanating surface in 3.3% of the measurements, which means that care must be taken when fitting the shield.

CONCLUSIONS

Although covered and uncovered tonometry readings correlated well, an overall trend for a slightly increased measured intraocular pressure as a result of using the silicone shield over the Goldmann tonometer tip was found. The outstanding sensitivity of this procedure in detecting increased intraocular pressure suggests that it can be useful in screening for ocular hypertension and glaucoma.

Sources of error with use of Goldmann-type tonometers

There are many sources of error in the use of Goldmann-type applanation tonometers. In clinically normal corneas hypofluorescence of the precorneal tear film, accommodation, the Valsalva maneuver and vertical gaze are preventable causes of large tonometric errors. Repeated tonometry may induce a decline in the intraocular pressure (IOP). Variations in the corneal resistance to indentation between eyes cause significant errors. The most significant cause of error in clinically abnormal eyes is corneal epithelial edema, which causes a marked underestimation of IOP. Measurements obtained with Goldmann-type tonometers can be used with confidence to monitor changes in the IOP of an individual, but should not be relied on to determine the absolute manometric pressure within an eye or to compare the IOPs in eyes of different individuals.