Tonometry in pediatric patients: a comparative study among Tono-pen, Perkins, and Schiötz tonometers

Comparison of intraocular pressure measurements with the tono-pen, goldmann applanation tonometer, and noncontact tonometer in nonglaucomatous pseudophakic children

BACKGROUND

To evaluate the agreement between the Goldman applanation tonometer (GAT), Tono-Pen, and noncontact tonometer (NCT) in the measurement of intraocular pressure (IOP) in pseudophakic children.

METHODS

The medical records of nonglaucomatous pseudophakic children between 2009 and 2019 were retrospectively analyzed. A total of 46 eyes of 23 patients operated for bilateral pediatric cataract were included in the study. The patients' mean age was 13.4 ± 4.1 years. Central corneal thickness (CCT) and IOP values measured with the GAT, Tono-Pen, and NCT were recorded. Agreement between the tonometers was evaluated by intraclass correlation coefficients (ICC) and the Bland-Altman method.

RESULTS

The mean IOP of the 46 eyes included in the study was measured as 13.7 ± 2.3 mm Hg with the GAT, 16.0 ± 2.3 mm Hg with NCT, and 16.5 ± 2.3 mm Hg with the Tono-Pen (p < 0.001). There is no statistical difference between NCT and Tono-Pen measurements, while GAT measurements were significantly lower than those of the NCT and Tono-pen. ICC values showed fair agreement between NCT and Tono-Pen (ICC = 0.720), whereas there was poor agreement between GAT and NCT (ICC = 0.501) and Tono-pen (ICC = 0.314).

CONCLUSIONS

With all devices included in the study, thicker corneas were associated with higher IOP measurements. Although there was moderate agreement between the NCT and Tono-Pen, there was a statistically significant difference in the IOP values provided by the three devices. Our results suggest these devices should not be used interchangeably.

Changes in intraocular pressures associated with inhalational and mixed anesthetic agents currently used in ophthalmic surgery

Purpose:

The aim of this study was to measure changes in intraocular pressures (IOPs) associated with inhalational and mixed anesthetic agents currently used for general anesthesia (GA) in ophthalmic surgery.

Methods:

In a cross-sectional study, 48 eyes from 48 consecutive subjects that underwent ophthalmic surgery under GA were included. Mixed anesthetics were used in 26 eyes and sevoflurane in 22 eyes. IOPs of the nonsurgery eyes were recorded at T1 (5 min before induction of anesthesia), T2 (5 min after intubation), and T3 (at the conclusion of surgery before extudation) using ICare PRO and Perkins tonometers. Linear mixed-effects models were used to compare differences in IOPs at various time points. Outcome measures were changes in IOP after induction of GA, intubation, and just before extubation and comparisons of decreases in IOPs induced by sevoflurane and mixed anesthetics.

Results:

Mean preanesthesia IOP for patients in this study (mean age ± standard deviation = 26.9 ± 18.3 years; range: 5–70 years) was 17.9 ± 4.9 (range: 10–30) mm Hg. There was a significant decrease in the mean IOP (standard error (SE) (in mm Hg) at T2 (Perkins: –4.65 (0.57); ICare PRO: –5.16 (0.56) and T3 (Perkins: –5.63; ICare PRO: –5.36) as compared to the IOP at T1 (P < 0.001). The decreases in IOPs at T2 and T3 were similar in both anesthetic groups (T2:P = 0.60; T3: P = 0.33).

Conclusion:

Significant decreases in IOPs after GA were observed and the differences were not significantly different between sevoflurane and mixed anesthetic agents. For management decisions in pediatric glaucoma, the IOP measurements under GA are crucial, the underestimation of IOP as noted with currently used anesthetic agents has to be accounted for and decisions are taken appropriately.

Influence of Axial Length on Intraocular Pressure Measurement With Three Tonometers in Childhood Glaucoma

PURPOSE

To determine the agreement between intraocular pressure (IOP) measurements obtained using the handheld version of the Goldmann applanation (Perkins; Clement-Clarke, Haag-Streit, Harlow, United Kingdom), rebound Icare-Pro (Icare, Tiolat Oy, Helsinki, Finland), and Tonopen XL (Reichert Inc., Depew, NY) tonometers in children with childhood glaucoma and to identify factors that may affect those measurements.

METHODS

Ninety-one eyes of 46 children with early-onset childhood glaucoma were included in this cross-sectional study in which IOP, ocular axial length, anterior chamber depth, lens thickness, vitreous length, and central corneal thickness measurements were obtained under general anesthesia. Agreement between tonometers was evaluated using intraclass correlation coefficients (ICCs) and the Bland-Altman method. The influence of ocular biometric parameters and central corneal thickness on IOP measurements was analyzed using multiple linear regression analysis.

RESULTS

The mean age of the children in the current study was 29.1 months (range: 13 to 31 months). The Icare-Pro and Tonopen XL overestimated IOP measurements compared to the Perkins tonometer (Icare-Pro-Perkins mean IOP difference: 2.2 ± 3.4 mm Hg, P < .0001, 95% confidence interval [CI]: 1.5 to 2.9 vs Tonopen XL-Perkins mean IOP difference: 6.7 ± 7.1 mm Hg, P < .0001, 95% CI: 5.2 to 8.2). The Icare-Pro showed greater agreement with the Perkins tonometer than the Tonopen XL (ICC: 0.789, 95% CI: 0.697 to 0.856, P < .0001 vs 0.453, 95% CI: 0.272 to 0.603, P < .0001). Ocular axial length affected IOP measurements the most, finding increased impact on Tonopen XL (slope: 0.086, 95% CI: 0.013 to 0.16, P = .022 vs 0.997, 95% CI: 0.369 to 1.625, P = .002 vs 1.571, 95% CI: 0.541 to 2.602, P < .0001 for Perkins, Icare-Pro, and Tonopen XL IOP measurements, respectively).

CONCLUSIONS

Ocular axial length affects IOP measured by the Perkins, Icare-Pro, and Tonopen XL devices in patients with childhood glaucoma. The Icare-Pro shows more agreement with the Perkins tonometer than the Tonopen XL; therefore, it seems to be a more suitable option for these patients. [J Pediatr Ophthalmol Strabismus. 2020;57(1):27-32.].

Effect of anesthesia on intraocular pressure measurement in children

Measurement of the intraocular pressure (IOP) is central to the diagnosis and management of pediatric glaucoma. An examination under anesthesia is often necessary in pediatric patients. Different agents used for sedation or general anesthesia have varied effects on IOP. Hemodynamic factors, methods of airway management, tonometry technique, and body positioning can all affect IOP measurements. The most accurate technique is one that reflects the awake IOP. We review factors affecting IOP measurements in the pediatric population and provide recommendations on the most accurate means to measure IOP under anesthesia based on the present literature.

Steroid-induced glaucoma in the pediatric population

Steroid medications may cause elevation of intraocular pressure, sometimes with permanent damage to the optic nerve. These therapies, via various routes of administration, are commonly prescribed for children, but the potential sequelae of elevated intraocular pressure and glaucomatous optic nerve damage can be even more severe and devastating in children than in adults. This review discusses the pathophysiology and potential risk factors, including the impact of intraocular pressure elevation via the different common routes of administration of steroids, clinical evaluation, and management of steroid response and steroid-induced glaucoma in children.

Intraocular pressure and biomechanical corneal properties measure by ocular response analyser in patients with primary congenital glaucoma

PURPOSE

To measure the differences in corneal hysteresis (CH) and corneal resistance factor (CRF) in primary congenital glaucoma (PCG) and in control subjects using ocular response analyser (ORA) and also to compare intraocular pressure (IOP) measurements given by ORA against IOP given by Perkins tonometer, a handheld version of Goldman applanation tonometer (GAT), to determine correlation.

METHODS

One hundred and eighteen eyes of 78 patients with PCG (group I) and 103 eyes of 53 controls (group II) were evaluated using ORA. In all participants, IOP was measured using the Perkins tonometer. The ORA device uses applanation pressure peaks to generate the corneal-compensated IOP (IOPcc), which is reportedly independent of corneal thickness, and the measurement of Goldman-correlated IOP (IOPg), which is influenced by corneal thickness.

RESULTS

The measures in group I were as follows: IOPcc 20.92 ± 5.33; IOPg 18.87 ± 6.67; CH 8.51 ± 2.25; CRF 9.85 ± 3.03; and IOP measured by Goldman 18.32 ± 5.13. The measures in group II were as follows: IOPcc 14.33 ± 2.91; IOPg 14.77 ± 3.00; CH 11.37 ± 1.61; CRF 11.02 ± 1.74; and IOP measured by Goldman 13.74 ± 2.42. The differences of all parameters compared between both groups were statistically significant (p < 0.001 for CH and for all IOP measures and p = 0.001 for CRF). The values of IOPcc, IOPg and IOP measured with Goldman were higher in group I than the values in group II. However, CH and CRF values were lower in group I.

CONCLUSION

A decrease in CH and CRF has been observed in patients with PCG compared to controls. Future research should assess how these parameters are modified in PCG and whether they could provide more information about progression.

Comparison of Tono-Pen and Goldmann applanation tonometers for measurement of intraocular pressure in healthy children

PURPOSE

To assess the agreement of intraocular pressure (IOP) measured with the Tono-Pen and the Goldmann applanation tonometer (GAT) in normal children and adolescents.

METHODS

A total of 439 subjects from birth to <18 years of age without anterior segment anomalies or glaucoma had their IOP measured with the two instruments by separate, masked examiners in the office or under general anesthesia.

RESULTS

On average, the Tono-Pen measured values slightly lower than the GAT for IOP <11 mm Hg and slightly higher than the GAT for IOP >11 mm Hg in the office setting. Using the average of GAT and Tono-Pen IOPs to estimate the true IOP, the average difference (GAT - Tono-Pen) was 0.4 mm Hg at IOP of 10 mm Hg and -3.0 mm Hg at IOP of 20 mm Hg. The 95% limits of agreement on the average difference between instruments were ± 6.4 mm Hg in the office setting and ± 6.8 mm Hg under general anesthesia. Larger differences between instruments were found with younger age. Standard error of measurement with the Tono-Pen was 1.44 mm Hg and 1.82 mm Hg for the office and anesthesia settings, respectively. Thicker corneas were associated with higher IOP with both the GAT and the Tono-Pen.

CONCLUSIONS

In normal children, average differences between IOP measured by Tono-Pen and GAT were small, although there was substantial test-retest variability. Younger age was associated with larger average differences, as was higher IOP in the office setting.

Measurement of intraocular pressure with pressure phosphene tonometry in children

PURPOSE

To study the accuracy and acceptability of intraocular pressure (IOP) measurement by the pressure phosphene tonometer, non-contact tonometer, and Goldmann tonometer in children.

METHODS

Fifty children (5 to 14 years old) participated in this prospective comparative study. IOP was measured with the pressure phosphene tonometer, non-contact tonometer, and Goldmann tonometer by three different examiners who were masked to the results. The children were also asked to grade the degree of discomfort from 0 to 5 (0 = no discomfort; 5 = most discomfort).

RESULTS

The mean IOPs measured by the Goldmann tonometer, pressure phosphene tonometer, and non-contact tonometer were 15.9 mm Hg (standard deviation [SD]: = 5.5 mm Hg; range: 10 to 36 mm Hg), 16.0 mm Hg (SD: 2.9 mm Hg; range: 12 to 25 mm Hg), and 15.7 mm Hg (SD = 5.1 mm Hg; range: 8 to 32 mm Hg), respectively (P = .722). The mean difference between pressure phosphene tonometer and Goldmann tonometer readings was 2.9 mm Hg and that between non-contact tonometer and Goldmann tonometer readings was 2.1 mm Hg. The 95% confidence interval of the mean difference between pressure phosphene tonometer and Goldmann tonometer readings was -1.07 and 1.19, and that between non-contact tonometer and Goldmann tonometer readings was -1.07 and 0.53. The mean discomfort ratings for the pressure phosphene tonometer, non-contact tonometer, and Goldmann tonometer were 0.6, 2.0, and 2.3, respectively (P < .001).

CONCLUSION

Although the pressure phosphene tonometer was less accurate than the non-contact tonometer compared with Goldmann tonometer, it gave a reasonably close estimate and had a high specificity of raised IOP. In addition, measurement by the pressure phosphene tonometer is most acceptable to children. The pressure phosphene tonometer can be considered as an alternative method of IOP measurement in children.

[Intraocular pressure measurement in children]

Intraocular pressure (IOP) measurement in children is often difficult to perform because younger children are non-compliant and resisting the examination. Normal IOP in children is not well established yet because in the studies reporting about IOP, the instruments used and clinical conditions have varied. Non contact tonometer often overestimates IOP in blinking children and is not always reliable. But all the others measurement techniques use contact (GAT, Perkins, Tono-Pen, ORA, RBT), and are not always suitable and easy-touse. Under general anaesthesia, mean IOP measured with Perkins applanation tonometer is under 8 mmHg before age of 3 months and under 12 mmHg between ages of 6 and 9 months. After, IOP shows an increasing trend with age of 1 mmHg per year up to 12 years. Some studies have proposed as normal pediatric IOP: To=0.71 x age (years) +10, up to age 10. Then, IOP tends to approach adult levels by 12 years of age. However pediatric glaucoma is rare: congenital glaucoma, before age of 3 years, autosomal dominant juvenile glaucoma, with family history of glaucoma and elevated IOP, or secondary glaucoma with special context. Thus, hypertony has to be confirmed by another measurement technique, correlated to central corneal thickness, and clinical examination (optic nerve head and visual field).

Comparison of intraocular tonometry using three different non-invasive tonometers in children

BACKGROUND

In childhood glaucoma, the correct determination of intraocular pressure (IOP) is crucial in clinical decision-making. We therefore investigated how intraocular tonometry readings correlate with readings from commonly used tonometers.

METHODS

IOP was measured unilaterally in 20 children suffering from congenital (n = 7) or secondary glaucoma (n = 13), 10 minutes after the induction of general anaesthesia. The children were aged from 1 month to 17 years (mean age 4.3 years, median age 1.3 years). Non-invasive applanation (Tono-Pen XL, Perkins tonometer) and indentation tonometry (Schiötz tonometer) were performed in random order prior to intraocular tonometry with a 26-gauge needle connected to a pressure sensor. Linear regression analysis and the coefficients of variance (CV) were used to compare the data obtained from the various tonometers.

RESULTS

Compared with intraocular pressure, the CV was 10% for the Tono-Pen XL, 17% for the Schiötz, and 19% for the Perkins tonometer. The coefficient of determination (r(2)) was 0.74 for Tono-Pen XL, 0.60 for Schiötz and 0.78 for Perkins tonometry. The IOP values obtained with the Tono-Pen XL scattered homogeneously around the intraocular IOP, while the Perkins and Schiötz tonometers underestimated intraocular measured IOP.

CONCLUSION

Of the three tonometers evaluated in this series of paediatric glaucoma patients, the Tono-Pen XL most closely reflected true IOP.

A clinical evaluation of proview pressure phosphene tonometry in children

PURPOSE

The Proview tonometer measures intraocular pressure by inducing a pressure phosphene through the eyelid and, if reliable and valid, may offer a quick, nonthreatening and noninvasive alternative method of obtaining intraocular pressures (IOPs) without the use of eye drops. This study compares the IOP measurements obtained in children using Proview pressure phosphene tonometry (PPPT) and Goldmann tonometry (GT).

METHODS

One hundred four 5- to 12-year-old patients of the University Optometric Center/SUNY College of Optometry participated in the study. Subjects were randomized to receive, by different investigators, either PPPT or GT first. Two measurements with each instrument were attempted on each eye of all subjects. A subgroup of 41 subjects was asked which of the two methods was preferred.

RESULTS

Seven percent of the subjects did not report a pressure phosphene response compared with 12% of the subjects on whom the investigators were unable to perform GT. The remaining 85 subjects completed the subject protocol. Of the 41 subjects asked, 56% preferred PPPT, 24% had no preference, and 20% preferred GT. The coefficient of repeatability between the two readings was higher for PPPT (3-4 mm Hg) than for GT (1 mm Hg). Mean IOP was 4 mm Hg higher for PPPT than GT with the difference in readings between the two instruments increasing with higher IOPs (r >19%, p < 0.005).

CONCLUSIONS

In our study of healthy young subjects, PPPT measurements of IOP appear to be repeatable within a few millimeters of mercury in most children, but for some children, variability in repeat measurements can be substantial. Our data showed a mean difference in readings of 4 mm Hg with a 95% confidence interval that the PPPT reading was between 12 mm Hg above GT and 4 mm Hg below GT. This wide range of values indicates that PPPT is not comparable to GT. However, because our study found that children can appreciate pressure phosphenes and most prefer PPPT over GT, the Proview monitor may have value as a noninvasive, portable screener in pediatric patients. To fully evaluate this potential, further studies are needed that include patients with high IOPs.

Corneal hysteresis and intraocular pressure measurement in children using the reichert ocular response analyzer

PURPOSE

To examine corneal hysteresis in children with normal eyes and congenital glaucoma and assess intraocular pressure (IOP) measurement with the Reichert Ocular Response Analyzer (RORA).

DESIGN

Observational, cross-sectional study.

METHODS

setting: Clinical practice. patients: Corneal hysteresis and intraocular pressure (Goldmann correlated [IOPg] and corneal compensated [IOPcc]) were recorded with RORA. IOP was also measured by Goldmann applanation tonometry.

RESULTS

Mean corneal hysteresis of 12.5 mm Hg was recorded in 81 [corrected] normal eyes of 42 children. It was markedly lower (mean 6.3 mm Hg) in 11 eyes of eight children with congenital glaucoma. No correlation was found between age and corneal hysteresis (r = -0.08). IOPg did not differ significantly from Goldmann applanation tonometry (P = .27). IOPcc was statistically significantly greater than IOPg (P = .014). RORA measurement was not possible in the presence of nystagmus but was possible with applanation tonometry. Cooperation with IOP measurement was much higher with RORA (89.8%) compared with applanation tonometry (78.7%).

CONCLUSIONS

Corneal hysteresis in children is similar to that reported in adults. No correlation was found with age. In the presence of nystagmus, IOP measurement was possible with Goldmann applanation tonometry but not RORA. Cooperation with IOP measurement was better with RORA than with Goldmann applanation tonometry.

Is the tono-pen accurate for measuring intraocular pressure in young children with congenital glaucoma?

PURPOSE

We sought to compare intraocular pressure (IOP) measurements by Perkins tonometer and Tono-Pen in young children with primary congenital glaucoma (PCG).

METHODS

This was a retrospective comparative case series. We reviewed the clinical records of all children with primary congenital glaucoma who underwent examinations under general anesthesia at Soroka University Medical Center between January 1999 and July 2002. Our main outcome measures were IOP with Perkins hand-held tonometer and Tono-Pen tonometer.

RESULTS

A total of 28 eyes of 16 children were examined under general anesthesia. The mean IOP was 18 +/- 6 mm Hg with the Perkins tonometer and 22 +/- 8 mm Hg with the Tono-Pen. In 18 eyes, IOP was less than 21 mm Hg with the Perkins tonometer; these eyes had already undergone surgical procedures. The other 10 eyes with IOP greater than 21 mm Hg with the Perkins tonometer underwent surgery at the end of the examination under anesthesia. In eyes with IOP greater than 16 mm Hg (Group A, n = 18), a significant difference (P < 0.001) was found between the Perkins and Tono-Pen measurements, even although the values were strongly correlated (r = 0.60). In contrast, in eyes with IOP less than 16 mm Hg (Group B, n = 10) no statistically significant difference (P = 0.28) and good correlation (r = 0.78) were obtained. A difference of 5.8 +/- 3.8 mm Hg and 0.6 +/- 1.7 mm Hg between Perkins and Tono-Pen readings, respectively, was found in Groups A and B.

CONCLUSIONS

Tono-Pen readings disagree with Perkins tonometer measurements for measuring IOP in children with PCG who present with IOP greater than 16 mm Hg and tends to overestimate IOP. A further study with a similar population is necessary to confirm these results.

The interoccasion repeatability of intraocular pressure measurement using the Tono-Pen in a sample of school-aged children

PURPOSE

The purpose of this study was to assess the interoccasion repeatability of the Tono-Pen XL portable applanation tonometer in school-aged children.

METHODS

Thirty-one normal children were recruited from The Ohio State College of Optometry Pediatric Clinic. They ranged in age from 6 to 14 years. Intraocular pressure was measured using the Tono-Pen XL in both eyes of all subjects on two different occasions within a median of 9 days. Refractive error was measured by noncycloplegic autorefraction. Data from right eyes only are presented.

RESULTS

There was no average difference in the intraocular pressure between occasions. The 95% limits of agreement between occasions were -5.58 to 4.87 mm Hg.

CONCLUSIONS

The Tono-Pen XL gives reasonably repeatable readings between occasions in school-aged children.

New Tonopen XL: comparison with the Goldmann tonometer

PURPOSE

To compare the intraocular pressure (IOP) values obtained using a Goldmann tonometer (Haag-Streit) with those obtained with the new Tonopen XL (Mentor), which has certain differences compared with first- and second-generation models.

METHODS

The IOPs of 104 patients were assessed by Goldmann tonometer and Tonopen XL tonometer. Goldmann measurements was done first in 145 eyes and Tonopen measurements were done first in 53 eyes. Four observers measured the IOP. Observers A, B and C used the Goldmann tonometer first and then the Tonopen XL, while observer D used the Tonopen XL first and then the Goldmann tonometer. The results were analysed by descriptive analysis and, when the distribution of the data was normal, paired t-test and Pearson's r coefficient were used to compare and correlate IOP measurements between Goldmann and Tonopen measurements. When the distribution of the data was non-normal, the Wilcoxon matched-pair test and Spearman coefficient were used. The agreement between Goldmann and Tonopen values was also calculated. ANOVA test was used to compare the difference obtained by 'Goldmann minus Tonopen' measurements among the three different observers.

RESULTS

A statistically significant difference (p < 0.0001) was found between the IOP readings obtained by Goldmann tonometer and the Tonopen XL and a significant correlation was found between the Goldmann values and Tonopen XL values (p < 0.001). When the Goldmann IOP was more than 20 mmHg the Tonopen XL measurements were lower than the Goldmann values. Also in this group this difference was statistically significant. No significant difference was found between Goldmann values and Tonopen values among the three observers, even though a significant difference was found between Goldmann values and Tonopen values for observer B. When the values obtained by first the Goldmann tonometer and then the Tonopen XL were compared with those obtained by first the Tonopen XL and then the Goldmann tonometer, no significant difference was found between the two groups.

CONCLUSION

The new Tonopen XL provides similar results to the Goldmann tomometer in 62% of the cases and was slightly less accurate than the Goldmann tonometer for extreme values, just like the previous Tonopen. Nevertheless the precision is good enough for the purpose of adequate screening.

Clinical comparison of the measurement of the IOP with the ocular blood flow tonometer, the Tonopen XL and the Goldmann applanation tonometer

PURPOSE

In addition to measuring ocular blood flow, the ocular blood flow tonometer (OBF) can also be set to solely record intraocular pressure (IOP). In this mode it provides a quick means of tonometry which may allow nursing staff to be more easily trained in its use than conventional Goldmann tonometry. With a view to its eventual use in nurse-led clinics we undertook a study to compare both the OBF tonometer and our currently favoured nurse practitioners tonometer the tonopen XL with Goldmann tonometry.

METHOD

IOP was measured in 99 eyes with all three tonometers in a random order.

RESULTS

There was not any statistically significant difference between the measurements of all three tonometers.

CONCLUSIONS

It is concluded that OBF tonometer can provide clinically useful measurements of intraocular pressure which may in fact be more accurate than the tonopen, however, our opinion is that it possibly is not suitable for a universal glaucoma clinics application.

Tonometry in adults and children. A manometric evaluation of pneumatonometry, applanation, and TonoPen in vitro and in vivo

OBJECTIVE

The purpose of the study was to determine the accuracy of applanation tonometry, pneumatonometry, and TonoPen tonometry in adults and children and the effect of age on tonometer error.

DESIGN

The design was divided into four parts: part 1 was prospective and cross-sectional, and parts 2 through 4 were prospective, cross-sectional, and masked.

PARTICIPANTS

This study contained 72 patients representing 74 data points.

INTERVENTION

Tonometry with simultaneous manometry was performed.

MAIN OUTCOME MEASURES

Intraocular pressure (i.o.p.) and the tonometric estimate of IOP were obtained.

RESULTS

The normal pediatric IOP follows the line Ta = 0.71 age(years) + 10 up to age 10. Applanation tonometry under anesthesia differs from pneumatonometry by an average of -8.6 mmHg and is age related by the equation Ta = Tpn + 2.6 log(age) - 10.3. The TonoPen was the most accurate instrument for enucleated eyes, and the pneumatonometer was the most accurate in anesthetized living eyes.

CONCLUSIONS

Applanation tonometry markedly underestimated IOP in young eyes. TonoPen tonometry performed well with enucleated eyes but was not adequately accurate for clinical use. The pneumatonometer performed the best clinically and the best overall.