Measurement of the intraocular pressure with the “transpalpebral tonometer” TGDc-01 in comparison with applanation tonometry

Background An irregular corneal surface compromises IOP measurement by Goldmann applanation tonometry. In such cases accurate measurement without corneal contact would be desirable. The new eyelid tonometer TGDc-01 measures IOP without corneal contact through the eyelid. The aim of the study was to evaluate the accuracy of the eyelid tonometer compared with Goldmann applanation tonometry (cornea thickness-corrected values) in subjects without corneal alterations.Methods IOP was measured in 199 eyes of 103 subjects without corneal alterations by means of two different methods. Measurements with the transpalpebral tonometer TGDc-01 and the Goldmann applanation tonometer were performed within 5 min in random order.Results The mean difference between lid tonometry and Goldmann applanation tonometry was 0.71 mmHg, SD ±2.467 mmHg. In the reliability analysis the intraclass correlation coefficient was 0.8620. Compared with Goldmann applanation tonometry 66.4% of the IOP readings measured by lid tonometry were in an interval of ±2 mmHg, 81.0% in an interval of ±3 mmHg. The maximum of deviation was –6 mmHg and +6 mmHg, respectively. The Bland and Altman plots are shown.Conclusions Lid tonometry correlates sufficiently with Goldmann applanation tonometry, but in more than 10% of the measurements the IOP readings differed by more than 3 mmHg. The eyelid tonometer may be helpful as a screening tool when Goldmann applanation tonometry is not applicable.     

Dynamic contour tonometry versus Goldmann applanation tonometry: a comparative study

Background Various sources of error, including central corneal thickness (CCT) and structural corneal rigidity, have been proposed for Goldmann applanation tonometry (GAT). The Pascal dynamic contour tonometer (DCT) is a novel device designed for intraocular pressure (IOP) measurements assumed to be largely independent of CCT and corneal curvature. We compared DCT with GAT in eyes with normal corneas of various thickness.Methods We prospectively measured IOP using DCT and GAT in random order in 100 eyes of 100 subjects (M:F=46:54; mean age 42±19, range 23–88 years).Results Mean DCT values were about 1mmHg higher than GAT readings (16±3 vs 15±3 mmHg, p=0.001). Bland–Altman analysis of individual pairs of DCT and GAT measurements revealed a bias of –1.0 mmHg [95% confidence interval (CI): ±1.2]. Neither GAT nor DCT showed a significant correlation with CCT (533±48, range 399–641 m).Conclusions In eyes with normal corneas, DCT allows suitable and reliable IOP measurements which are in good concordance with GAT. Comparison of DCT with intracameral manometry is desirable in the future.     

Intraocular pressure difference in Goldmann applanation tonometry versus a transpalpebral tonometer TGDc-01"PRA" in glaucoma patients

PURPOSE: The object of this study was to compare intraocular pressure measurements obtained with the TGDc-01"PRA", a new, transpalpebral indentation tonometer, with those from Goldmann applanation tonometry in normal and glaucomatous eyes. METHODS AND PATIENTS: Forty healthy eyes and 185 eyes suffering from glaucoma were included in the study. For Goldmann tonometry three measurements and for the TGDc-01 ten measurements were performed in a random order. All participants were placed in an upright position for all measurements. RESULTS: In both groups a systematic increase of intraocular pressure was found within the TGDc-01-measurements. Therefore, the first 3 measurements of each device were used for further statistical analysis. No learning curve could be demonstrated for the TGDc-01-measurement with normal eyes. Within the group of normal eyes the mean IOD obtained with the TGDc-01 was 1.84 mmHg lower than the mean IOD obtained with Goldmann tonometry (two-sided Student's t-test; P = 0.003). In the group of glaucomatous eyes, the mean intraocular pressure obtained with the Goldmann tonometry was 19.7 +/- 10.1 mmHg, with the TGDC-01 18.1 +/- 7.1 mmHg (coefficient of correlation r = 0.64, P < 0.001). The mean standard deviation of intraocular pressure measurements with Goldmann tonometry was 1.2 +/- 0.9 mmHg, with the TGDc-01 3.1 +/- 2.1 mmHg. TGDc-01-measurements overestimated intraocular pressure compared to Goldmann tonometry up to values of 16 mmHg and underestimated intraocular pressure at values over 16 mmHg. The difference increased by 5.5 mmHg per 10 mmHg Goldmann tonometry. The probability of success, defined as TGDc-01-recordings within +/- 3 mmHg of the Goldmann tonometry recordings, was less than 53 % between 5 and 20 mmHg and less than 30 % between 20 and 30 mmHg. Intraocular pressure (Goldmann tonometry) over 30 mmHg was always accompanied by TGDc-01-measurements lower than 3 mmHg. CONCLUSION: In eyes with elevated intraocular pressure, the TGDc-01"PRA" significantly underestimated the intraocular pressure measurement when compared to the gold standard, Goldmann tonometry. At present, measurement of the intraocular pressure with the TGDc-01 should not be used for clinical management of patients with glaucoma.     

Transpalpebral measurement of intraocular pressure using the TGDc-01 tonometer versus standard Goldmann applanation tonometry

Background A recently developed digital tonometer for transpalpebral intraocular pressure (IOP) measurement, distributed by Corneal, Inc., allows the noninvasive measurement of IOP for screening purposes.Method We measured the IOP of 218 eyes in 109 patients of the Interdisciplinary Uveitis Center of the University of Heidelberg with intact corneal epithelium. IOPs were measured first with the TGDc-01 tonometer, and then by means of Goldmann tonometry. IOPs were recorded by two independent examiners. The mean of three measurements obtained with the TGDc-01 was taken, whereas only one measurement was performed with the Goldmann tonometer.Results The mean difference between the TGDc-01 and Goldmann measurements was 3.7 mmHg. The standard deviation of the differences was ±4.06 mmHg. Thus measurements acquired with the TGDc-01 may range 4.4 mmHg above or 11.8 mmHg below the values given by Goldmann tonometry.Conclusion The IOP values obtained with the TGDc-01 were in poor agreement with Goldmann tonometry. We found a higher variation as well as a bias towards lower IOP values with the TGDc-01. It is a question of clinical judgement as to how far these deviating measurements can be accepted for screening purposes. Because the IOPs obtained with the TGDc-01 are generally lower and less accurate than those obtained with the Goldmann tonometer we believe that the TGDc-01 is not a reliable tool for IOP measurement in clinical routine.This work was presented at the 101st meeting of the German Society of Ophthalmology, Berlin, 2003     

Effects of topical anaesthetics and repeated tonometry on intraocular pressure

Purpose: To investigate the effects of repeated measurements of intraocular pressure (IOP) using Goldmann applanation tonometry (GAT) and applanation resonance tonometry (ART) to identify mechanisms contributing to the expected IOP reduction. Methods: A prospective, single‐centre study with six healthy volunteers. Consecutive repeated series (six measurements/serie/method) were made alternately on both eyes for 1 hr with oxybuprocaine/fluorescein in the right eye and tetracaine in the left. The left eye was Pentacam^® photographed before and repeatedly for 20 min after the IOP measurements. On a separate occasion, the same volunteers received the same amount of anaesthetic drops for 1 hr but without repeated IOP measurements. Results: A significant IOP reduction occurred with both ART and GAT in the oxybuprocaine‐treated eye, ?4.4 mmHg and ?3.8 mmHg, respectively and with ART in the tetracaine eye, ?2.1 mmHg. There was a significant difference in IOP reduction between the oxybuprocaine and tetracaine eyes with ART. There was a significant drop in anterior chamber volume (ACV) immediately after the IOP measurements, ?12.6 μl that returned to pretrial level after 2 min. After 1 hr of receiving anaesthetic eye drops (without IOP measurements), the IOP decreased significantly in the oxybuprocaine eye for both ART and GAT, ?3.1 and ?1.7 mmHg, respectively, but not in the tetracaine eye (p = 0.72). Conclusion: The IOP reduction cannot be explained solely by aqueous humor being pressed out of the anterior chamber. While significant IOP reduction occurred with both tetracaine and oxybuprocaine after repeated mechanical applanation, the IOP reduction was significantly greater with oxybuprocaine.     

Evaluation des mobilen TGDc-01-Tonometers und Vergleich mit dem Applanationstonometer nach Goldmann

PURPOSE: The aim of this study was to evaluate patients' acceptance and intraocular pressure (IOP) readings of a new digital mobile tonometer (TGDc-01) and compare it to Goldmann applanation tonometry.METHOD: Measurements repeated five times with the TGDc-01 and three times with Goldmann tonometry were performed in 100 eyes of 100 patients by two independent investigators. Patients' acceptance of both techniques was evaluated by a visual analogue scale (VAS).RESULTS: The mean IOP with the TGDc-01 yielded 15.4 mmHg for investigator 1 and 12.7 mmHg for investigator 2 (range: 4-43 mmHg). Results of the measurements with Goldmann tonometry showed 17.6 mmHg for investigator 1 and 17.3 mmHg for investigator 2 (9-42 mmHg). The IOP difference of the two tonometry methods was highly significant (p<0.001). The intraobserver variability was 29% for investigator 1 and 8% for investigator 2. Mean IOP values of the two investigators taken with the TGDc-01 differed significantly (p<0.01) from each other by a mean of 2.6 mmHg.CONCLUSIONS: The new mobile tonometer TGDc-01 is better accepted by patients but IOP values are significantly lower compared to Goldmann tonometry and variability is high. Regarding glaucoma diagnostics it seems to be less suitable than Goldmann tonometry.     

Three portable tonometers, the TGDc-01, the ICARE and the Tonopen XL, compared with each other and with Goldmann applanation tonometry*.

Three portable tonometers, the TGDc-01, the ICARE and the Tonopen XL, were compared with each other and to Goldmann applanation tonometry in a large group of healthy subjects and patients with ocular hypertension or glaucoma (n = 103). Measurements performed with the ICARE and the Tonopen XL were in good agreement with that of the Goldmann tonometer. Intraocular pressure (IOP) values measured with the TGDc-01 were significantly lower and showed more variability. The 95% limits of agreement (portable tonometer - Goldmann) were -17 to +10 mmHg for the TGDc-01, -6 to +7 mmHg for the ICARE and -6 to +8 mmHg for the Tonopen. Corneal thickness could not explain the differences between an IOP measured with the portable tonometers and an IOP measured with the Goldmann tonometer. Patient comfort was slightly higher for ICARE when compared with the Tonopen.     

Intraocular pressure difference in Goldmann applanation tonometry versus Perkins hand-held applanation tonometry in overweight patients

Objective

To analyze the increase in intraocular pressure (IOP) caused by anatomic and physiologic factors in overweight patients when using Goldmann applanation tonometry.

Design

A prospective cohort study.

Participants

Seventy average-weight individuals who had no difficulties with IOP measurements at the slit lamp and 12 obese patients with suspected glaucoma who could position the head at the slit lamp only with great effort participated.

Intervention

The authors compared IOP values between slit-lamp-mounted Goldmann applanation tonometry and Perkins hand-held tonometry.

Main outcome measure

The difference in Goldmann and Perkins IOP measurements was examined.

Results

In the group of obese patients, the mean IOP was 20.9 ± 2.28 mmHg (mean ± standard deviation; range, 18–26 mmHg) for the right eye and 21.4 ± 3.16 mmHg (range, 16–28 mmHg) for the left eye when determined by Goldmann tonometry and 16.3 ± 2.39 mmHg (range, 13–20 mmHg) for the right eye and 16.3 ± 2.42 (range, 11–19 mmHg) for the left eye when determined by Perkins tonometry. The mean decrease was 4.5 ± 1.3 mmHg (range, 3–7 mmHg) for the right eye and 4.9 ± 1.9 mmHg (range, 2–9 mmHg) for the left eye. In the control group, the mean difference between the two types of tonometers for the right eye was 0.34 ± 0.69 mmHg and for the left eye was 0.33 ± 0.82 mmHg. Patients who had a falsely elevated IOP on Goldmann tonometry had an average body mass index of 34 ± 3.82 (range, 28.5–41.9); most were female (5:1 ratio).

Conclusion

The authors believe simultaneous breath-holding and thorax compression, with subsequent increase in venous pressure, may be a causative factor for transitory elevations of IOP. Perkins tonometry in obese patients may help avoid a false diagnosis of glaucoma caused by transitory elevations in IOP.     

Transpalpebral measurement of intraocular pressure using the Diaton tonometer versus standard Goldmann applanation tonometry

Background  

Diaton transpalpebral tonometry is a new version of TGDc-01 transpalpebral tonometry. The aim of this study is to evaluate the reliability of this method, and to compare the results with those of corrected Goldmann applanation tonometry (c-GAT), which is the “gold standard” for the clinical measurement of IOP.     

Prospective comparison of the new indentation tonometer TGdC-01, the non-contact tonometer PT100 and the conventional Goldmann applanation tonometer

BACKGROUND: This study aimed to compare the results of newer tonometric techniques with standard tonometry for the examples of the Goldmann applanation tonometry (GAT), the indentation tonometer "TGDc-01" and the non-contact tonometer "PT 100". PATIENTS: The study was conducted on a total of 52 healthy subjects. The IOP was measured in each subject on both eyes with all three methods. There were 27 males (51.9 %), 25 females (48.1 %) with an average age of 28.5 years, with a minimum of 13 and a maximum of 79 years. RESULTS: There was no statistically significant difference between the non-contact and the Goldmann applanation tonometry. The measurements were 0.4 mmHg lower, no difference for the left or right side was seen. For IOP higher than 15 mmHg - 0.88 mmHg lower and for IOP lower 15 mmHg - 0.15 mmHg. The results for the "TGDc01" were 0.82 mmHg lower than GAT, the standard deviation was a little higher with 2.9 mmHg compared to 2.67 mmHg for GAT. For IOP higher than 15 mmHg they rose up to - 2.28 mmHg, for IOP lower than 15 mmHg the results for "TGDc-01" were only - 0.2 mmHg lower. There was also an effect with respect to the side, on the right eye the difference was significant with 3.03 mmHg (p = 0.006), in contrast to the left eye with 2.69 mmHg (p = 0.235). For "TGDc01" the standard deviation was higher with 2.9 mmHg compared to 2.6 mmHg for "PT 100". CONCLUSIONS: The non-contact tonometer showed no clinical relevant difference compared with GAT for measuring IOP. The indentation tonometer showed differences for precision, for higher tension IOP the measurement was lower compared with GAT. There was also a significant side difference using the "TGDc-01".     

Clinical evaluation of the new TGDc-01 "PRA" palpebral tonometer: comparison with contact and non-contact tonometry.

PURPOSE: The TGDc-01 "PRA" (Ryazan State Instrument, Ryazan, Russia) tonometer is a new portable small-sized tonometer that measures intraocular pressure (IOP) through the eyelid. The purpose of this study is to assess the repeatability of the TGDc-01 IOP measurements by comparing them against those obtained with Goldmann tonometer and with those from Perkins applanation tonometer, Xpert (Reichert, Depew, NY) noncontact tonometer, and Tono-Pen XL (Medtronic Solan, Jacksonville, FL) digital tonometer. METHODS: Fifty-eight right eyes of 58 young subjects were measured with each of the tonometers. Noncontact tonometry was performed first, followed by Goldmann and Perkins applanation tonometer (in random order), digital Tono-Pen XL, and finally TGDc-01 tonometer (sitting and supine position). Correlation analysis was used to evaluate the relationship between the Goldmann tonometer and the remaining tonometers used in this study. Plotting the difference between the methods against mean was also done to compare the tonometers. The hypothesis of zero bias was examined by a paired t-test. The 95% limits of agreement (LoA) were also calculated. RESULTS: TGDc-01 showed no statistical difference between the IOP measurements obtained in sitting and supine positions. A poor relationship between the TGDc-01 and Goldmann tonometer was found (r = 0.173; p = 0.001). Although the mean differences between Goldmann and Tonopen XL, Xpert, and TGDc-01 IOP measurements were statistically significant, the wider 95% LoA was observed when comparing the Goldmann and TGDc-01 tonometers. Computation of the 95% LoA resulted in a wide bias range when comparing the TGDc-01 with all the tonometers used in this study. CONCLUSIONS: The TGDc-01 "PRA" tonometer was not comparable with the other techniques used in the study. The wide dispersion range of the values obtained shows low repeatability of the TGDc-01 for screening purposes. These results could be because of the technique of measurement and/or interindividual variables.     

Central corneal thickness and Diaton transpalpebral tonometry

Background To examine the effects of central corneal thickness on the measures obtained from transpalpebral tonometry (Diaton), and to identify correlations between intraocular pressure (IOP) measurements with Diaton and the Goldmann applanation tonometer (GAT). Methods In this cross-sectional study, 162 eyes of 81 participants were included. Intraocular pressure measurements were obtained in all patients using Diaton and GAT. Central corneal thickness was determined by ultrasound pachymetry. The participants were stratified by corneal thickness: group I <530 μm (n = 56), group II 530–560 μm (n = 65), and group III >560 μm (n = 41). Results There were moderate correlations between IOP readings obtained using the Diaton and corrected GAT (C-GAT) (r = 0.303; P < 0.0001), and between corrected Diaton (C-Diaton), and C-GAT (r = 0.399; P < 0.0001). The mean Diaton tonometer readings were lower than C-GAT measurements (Diaton-corrected GAT mean difference, 0.9 ± 3.8 mmHg; c-Diaton-corrected GAT mean difference, 0.7 ± 3.5 mmHg). Differences were detected between the groups of patients for the GAT values [2.4 ± 3.6 mmHg for those with the thinnest corneas (<530 μm), 0.7 ± 3.6 mmHg for those with moderate corneas (between 531 μm and 560 μm), and −0.6 ± 3.6 mmHg for those with the thickest (>560 μm) corneas], whereas a significantly lower difference (0.9 ± 3.8 mmHg) was noted for the Diaton values of all individuals. Conclusions The Diaton measurements show moderate correlation with those provided by applanation tonometry. The Diaton tonometer seems to be more affected by the corneal thickness, especially in the thinnest corneas. No author has a financial interest in any product mentioned in the article. No author has a conflict of interest in any product mentioned in the article.     

Comparison of dynamic contour tonometry with Goldmann applanation tonometry in glaucoma practice

Purpose: To compare intraocular pressure (IOP) readings taken using dynamic contour tonometry (DCT) with IOP readings taken with Goldmann applanation tonometry (GAT) in eyes with glaucoma or ocular hypertension. Methods: The present study included 100 eyes in 100 patients with glaucoma or ocular hypertension. After pachymetry DCT and GAT were performed. Intraocular pressures as measured with DCT and GAT were compared with one another and with central corneal thickness (CCT). Results: Mean DCT IOP measurements (20.1 ± 4.3 mmHg) were significantly (p < 0.001) higher than GAT IOP values (17.9 ± 4.7 mmHg). The mean difference between DCT and GAT measurements was 2.1 mmHg (range ? 3.4 to 9.7 mmHg). The difference followed a normal distribution. Measurements made with DCT and GAT correlated significantly with one another (Spearman’s rho = 0.761, p < 0.001). Neither GAT nor DCT measurements showed a significant correlation with CCT (537 ± 39 μm, range 458–656 μm). Multivariate regression analysis has shown that the difference between DCT and GAT is influenced significantly by ocular pulse amplitude (r = ? 0.334, p = 0.001) and it is not influenced by CCT (r = ? 0.106, p = 0.292). Conclusions: In eyes with glaucoma or ocular hypertension, DCT facilitates suitable and reliable IOP measurements which are in good concordance with GAT readings. Variation in CCT cannot by itself explain the differences in measurements taken with DCT and GAT in a number of eyes.     

Pressure phosphene tonometry versus Goldmann applanation tonometry for measuring intraocular pressure before and after LASIK

PURPOSE: To compare pressure phosphene tonometry with Goldmann applanation tonometry for measuring intraocular pressure (IOP) before and after LASIK. METHODS: Forty-three (18 men and 25 women) consecutive healthy patients underwent complete pre- and postoperative LASIK ophthalmologic assessments including manifest and cycloplegic refraction, keratometry, and central corneal thickness. Three repetitive sets of pressure phosphene tonometry and Goldmann applanation tonometry measurements were performed the day before and 3 months following uneventful LASIK. RESULTS: Mean preoperative spherical equivalent refraction was -4.70 +/- 2.50 diopters (D) (range: -1.50 to -12.90 D) and mean preoperative keratometry was 43.95 +/- 1.08 D. After LASIK, spherical equivalent refraction was +0.23 +/- 0.11 D and mean keratometry was 39.46 +/- 2.28 D. Preoperative pressure phosphene tonometry (12.16 +/- 1.58 mmHg) and Goldmann applanation tonometry (12.01 +/- 1.55 mmHg) IOP measurements were similar. Postoperative IOP was 10.30 +/- 1.16 mmHg with Goldmann applanation tonometry and 12.20 +/- 1.62 mmHg with pressure phosphene tonometry. The postoperative IOP difference between Goldmann applanation tonometry and pressure phosphene tonometry was 0.15 +/- 1.12 mmHg (P = .41). The mean change in pachymetry after LASIK was 68.73 +/- 73 microm. The change in Goldmann applanation between preoperative and postoperative LASIK values was 1.71 +/- 1.43 mmHg (P < .0001), a change that was strongly correlated with changes in corneal thickness (R = 0.75, P < .0001) and keratometry (R = 0.72, P < .0001). No such correlations were found with pressure phosphene tonometry. CONCLUSIONS: Goldmann applanation tonometry-measured IOP decrease after LASIK is strongly correlated with a decrease in central corneal thickness and changes in keratometry, whereas pressure phosphene tonometry-measured IOP is independent of corneal thickness. Pressure phosphene tonometry appears to be a more reliable method for recording tonometry in these patients.     

Diaton tonometry: an assessment of validity and preference against Goldmann tonometry

Background: To assess agreement between the Diaton, a new transpalpebral tonometer, and Goldmann applanation tonometry, the accepted gold standard. Design: Comparative study of two devices in a hospital setting. Participants: Two hundred and fifty‐one patients attending the eye casualty and general ophthalmology clinics at St James' University Hospital, Leeds between February and December 2009. Methods: Intraocular pressure was measured using Goldmann applanation tonometry and Diaton tonometry by one examining ophthalmologist. Patient preference for either technique was also recorded. Main Outcome Measures: Intraocular pressure measured by Diaton was compared with intraocular pressure measured by Goldmann applanation tonometry. Limits of agreement were determined using the Bland‐Altman method. Results: Two hundred and fifty right eyes underwent both Goldmann applanation tonometry and Diaton tonometry. Mean intraocular pressure was 13.8 ± 3.6 mmHg using Goldmann applanation tonometry and 13.2 ± 4.3 mmHg using Diaton tonometry. Upper and lower limits of agreement were +8.4 mmHg and ?9.6 mmHg, respectively. Order of intraocular pressure measurement and positioning did not influence limits of agreement in a clinically significant manner. Overall, more patients expressed preference for Diaton tonometry (40.2%) than Goldmann applanation tonometry (30.3%). Those aged 50 or less were more likely to prefer Diaton tonometry. Conclusions: The Diaton tonometer is portable, lightweight, user‐friendly and well tolerated by patients. However, it shows poor agreement with Goldmann applanation tonometry, thereby precluding it from being regarded as a substitute in routine clinical practice.     

The effect of contact lens-induced corneal edema on Goldmann applanation tonometry and dynamic contour tonometry

Purpose  To evaluate the effect of contact lens-induced corneal edema on intraocular pressure (IOP) measurements using Goldmann applanation tonometry (GAT) and dynamic contour tonometry (DCT) in Asian subjects. Participants  The study included 40 eyes of 20 normal volunteers with no evidence of ocular disease. Methods  Forty eyes of 20 healthy volunteers were required to wear soft contact lenses for 2 hours to induce corneal swelling. Central corneal thickness (CCT) and IOP were measured before and immediately after contact lens wear using specular microscope, GAT, and DCT. The IOP measurements by GAT and DCT were compared. The changes in the CCT and the IOP measurements after wearing contact lenses were assessed. Results  The mean CCT of the 40 eyes evaluated was 532.6 ± 31.6 μm. The mean IOP was 11.78 ± 2.04 mmHg for the GAT and 14.46 ± 1.89 mmHg for the DCT, and the difference was statistically significant (P < 0.001). After wearing contact lenses, the mean CCT was 553.2 ± 34.3 μm, which was 20.6 ± 12.9 μm greater than before wearing them (P < 0.001). The mean IOP measurements of the GAT and DCT were decreased after wearing the contact lenses. The mean decrease of the GAT values was 0.43 ± 1.95 mmHg, which was not statistically significant (P = 0.175). However, the mean decrease of the DCT readings, which was 0.75 ± 1.74 mm Hg, was statistically significant (P = 0.010). Conclusion  The IOP measurements with DCT were significantly higher than those with GAT in healthy Asian eyes. Although the mean IOP measurements of both the GAT and the DCT were decreased in the edematous cornea, IOP measurements of the DCT were more affected by corneal edema than were the GAT. The authors have no proprietary, commercial, or financial interests in any of the products described in this study.     

Should Orbscan pachometry be performed before or after Goldmann applanation tonometry?

PURPOSE: To compare the Orbscan central corneal thickness (CCT) values before and after intraocular pressure (IOP) measurement with Goldmann applanation tonometry in young normal adults. MATERIALS AND METHODS: Fifty-three eyes of 53 subjects who were free from any ocular problems were studied. The measurements included optical pachometry by the Orbscan II system, followed by Goldmann applanation tonometry, and finally Orbscan optical pachometry again. Standard Goldmann technique was adopted with the application of one drop of 0.4% benoxinate and fluorescein sodium prior to the measurement. The same operator was involved in the Orbscan pachometry before and after Goldmann tonometry. Another investigator was responsible for Goldmann tonometry. Three readings were obtained in each case, and the means were used for analysis. RESULTS: The mean IOP of the sample was 14.6 +/- 2.6 mmHg. There was no significant difference (paired t-test: p = 0.50) in the mean CCT values before and after the Goldmann tonometry (551 +/- 32 and 552 +/- 35 microm respectively). CONCLUSION: Standard Goldmann applanation tonometry does not affect the Orbscan CCT values. Measurement of CCT for the adjustment of true IOP can be carried out either before or after Goldmann tonometry.     

Measurement of intraocular pressure in LASIK and LASEK patients using the Reichert Ocular Response Analyzer and Goldmann applanation tonometry

PURPOSE: To determine the efficacy of the Reichert Ocular Response Analyzer (ORA) to measure intraocular pressure (IOP) following corneal laser refractive surgery. METHODS: Intraocular pressure was measured using Goldmann applanation tonometry preoperatively and 3 months following LASIK and LASEK for all levels of myopia and low levels of hyperopia. In LASIK eyes, 120-microm flaps were cut using the Hansatome XP. The ORA was used to measure Goldmann correlated IOP and corneal compensated IOP 3 months postoperatively. Postoperative central corneal thickness, hysteresis, and corneal curvature were assessed to determine their relationship with postoperative change in Goldmann applanation tonometry IOP. Efficacy of ORA IOP measurement was analyzed by comparing Goldmann applanation tonometry IOP with Goldmann correlated IOP. RESULTS: LASEK was performed on 35 eyes, and LASIK was performed on 90 eyes. In the LASIK group, mean Goldmann applanation tonometry IOP decreased 3.7+/-2.3 mmHg postoperatively (P=.00). Postoperative Goldmann applanation tonometry did not differ significantly (P=.06) from postoperative ORA Goldmann correlated IOP (10.2+/-2.1 mmHg). In the LASEK group, mean Goldmann applanation tonometry IOP decreased 3.9+/-2.3 mmHg (P=.00). Postoperative Goldmann applanation tonometry did not differ significantly (P=.6) from postoperative ORA Goldmann correlated IOP (10.7+/-2.5 mmHg). Postoperative decrease in Goldmann applanation tonometry IOP did not correlate with age, ablation depth, pre- and postoperative central corneal thickness or corneal hysteresis, or postoperative decrease in corneal curvature. CONCLUSIONS: Intraocular pressure measurements were similar using both the ORA Goldmann correlated IOP and Goldmann applanation tonometry following keratorefractive surgery.     

Comparison of the ICare® rebound tonometer with the Goldmann tonometer in a normal population

The aim of this study was to evaluate the accuracy of measurement of intraocular pressure (IOP) using a new induction/impact rebound tonometer (ICare) in comparison with the Goldmann applanation tonometer (AT). The left eyes of 46 university students were assessed with the two tonometers, with induction tonometry being performed first. The ICare was handled by an optometrist and the Goldmann tonometer by an ophthalmologist. In this study, statistically significant differences were found when comparing the ICare rebound tonometer with applanation tonometry (AT) (p < 0.05). The mean difference between the two tonometers was 1.34 +/- 2.03 mmHg (mean +/- S.D.) and the 95% limits of agreement were +/-3.98 mmHg. A frequency distribution of the differences demonstrated that in more than 80% of cases the IOP readings differed by <3 mmHg between the ICare and the AT. In the present population the ICare overestimates the IOP value by 1.34 mmHg on average when compared with Goldmann tonometer. Nevertheless, the ICare tonometer may be helpful as a screening tool when Goldmann applanation tonometry is not applicable or not recommended, as it is able to estimate IOP within a range of +/-3.00 mmHg in more than 80% of the population.     

Comparison of dynamic contour tonometry and Goldmann applanation tonometry following penetrating keratoplasty

Objective: To evaluate dynamic contour tonometry (DCT) versus Goldmann applanation tonometry (GAT) intraocular pressure (IOP) measurements in eyes that underwent penetrating keratoplasty (PKP).Design: Prospective, cross-sectional, observational study.Participants: Thirty-one eyes of 28 patients were examined after PKP.Methods: All eyes had undergone PKP with interrupted sutures. The postoperative period was more than 1 year for 25 eyes and less than 1 year for 6. Sutures were removed based on corneal topography and refraction. IOP was measured by both DCT and GAT methods and was correlated to the number of remaining sutures.Results: IOP readings were successfully obtained in 25/31 (80.6%) with DTC and in 21/31 (67.7%) with GAT (p = 0.25). In eyes with fewer than 4 remaining sutures, both methods were successful. In eyes with more than 4 sutures, the success rates of DCT and GAT were 66.7% and 44.4%, respectively (p = 0.18). In PKPs with a postoperative period of more than 1 year, the success rates of DCT and GAT were 96% and 84%, respectively (p = 0.16). In 20 eyes, both methods measured the IOP. The mean IOP obtained by DCT (16.6 [SD 2.8] mm Hg) was higher than the mean IOP obtained from GAT (15.1 [SD 3.6] mm Hg). The IOPs from the 2 instruments correlated significantly (p < 0.05) and the mean difference was 1.5 mm Hg.Conclusions: The success rate in measuring IOP with DCT and GAT did not show any statistically significant difference. Both methods were less effective measuring the IOP after recent PKPs and regrafts. However, DCT seemed to be superior to GAT in corneas with more than 4 remaining sutures and in PKPs performed more than 1 year earlier. The absolute values of IOP were higher with DCT than with GAT.