Effect of proparacaine on central corneal thickness values: an evaluation using noncontact specular microscopy and pentacam

Non-contact specular microscopy with Topcon instruments to assess central corneal thickness of healthy human eyes - A 20 year review

BACKGROUND

The purpose of this review was to evaluate the consistency of central corneal thickness (CCT) values reported with use of Topcon SP-2000 P and SP-3000 P non-contact specular microscopes since their introduction in 1999 with the two microscopes having been commonly used in a wide range of studies.

METHODS

As a primary resource, PubMed was used to search for peer-reviewed articles in any language that included CCT values obtained with non-contact specular microscopy reported for humans with nominally healthy corneas. Relevant articles were obtained and any cited publications also checked.

RESULTS

A total of 76 articles were identified which reported CCT on different small-to-moderate sized groups of individuals, published between 1999 and 2019. From these, an overall group mean CCT value of 0.525 ± 0.013 mm (median 0.525 mm) can be calculated. An estimated 95 % confidence interval (CI, based on 1.96 SD) would be between 0.500 and 0.550 mm. For the two Topcon models, the group mean ± SD values were 0.529 ± 0.013 mm and 0.517 ± 010 mm respectively. An assessment of the CCT data sets in relation to the reported average age indicated no statistically significant effect (p = 0.289, r = -0.129). Very similar average CCT values were also encountered in 4 other reports where these microscopes were used in large-scale population studies as well as in 2 other reports using the newer Topcon SP-1 P model.

CONCLUSIONS

The Topcon stand-alone non-contact specular microscopes have yielded consistent and predictable corneal thickness measures over many years.

Comparison of rebound tonometry and non-contact airpuff tonometry to Goldmann applanation tonometry

Purpose:

The aim of this study was to compare the intraocular pressure measurements obtained from healthy subjects with the rebound tonometry, non-contact airpuff tonometry, and Goldmann applanation tonometry in different age groups.

Methods:

A total of 180 eyes of 90 healthy subjects were included in the study. According to the subjects’ ages, the eyes were categorized into three groups: group 1 (age: 7–17 years), group 2 (age: 18–40 years), and group 3 (age: 41–75 years). Intraocular pressure was measured on each subject always in the same order: rebound tonometry, non-contact airpuff tonometry, and Goldmann applanation tonometry. Central corneal thickness values were obtained using ultrasonic pachymetry. One-way repeated-measures analysis of variance, Pearson’s correlation coefficient, and Bland–Altman analysis were used for the statistical assessment.

Results:

The mean corneal thickness was found to be 604 ± 13 µm, 546 ± 15 µm, and 547 ± 15 µm in group 1, group 2, and group 3, respectively. Non-contact airpuff tonometry was significantly higher than both Goldmann applanation tonometry and rebound tonometry measurements in all groups (p < 0.001, for all). No statistical difference between Goldmann applanation tonometry and rebound tonometry measurements was found in group 1 (p = 0.248), group 2 (p = 0.63), and group 3 (p = 0.126). There was a significant positive correlation in the meaning of intraocular pressure measurements between rebound tonometry and non-contact airpuff tonometry; non-contact airpuff tonometry and Goldmann applanation tonometry; and Goldmann applanation tonometry and rebound tonometry in all groups.

Conclusion:

As a result, without need for topical anesthesia, fast measurement and ease-of-use rebound tonometry is a reliable alternative to Goldmann applanation tonometry in different age groups.

Corneal Thickness Response after Anesthetic Eye Drops: Our Own Results and Meta-Analysis

We aimed to test if there are different patterns in the central corneal thickness (CCT) response after instilling oxybuprocaine anesthetic eye drops and also to determine whether there is a significant change in the CCT. CCT was measured in 60 eyes of 60 healthy subjects before and during the hour after oxybuprocaine 0.4% eye drops were instilled. In addition, a systematic review and meta-analysis were carried out in order to answer the following PICO (patient, intervention, comparison, and outcome) question: What effect do anesthetic eye drops have on CCT values? We found no significant changes in the mean CCT values during the hour's observation (ANOVA, p = 0.209), and the meta-analysis revealed no statistically significant changes in the CCT after anesthesia (Q-Value = 1.111; p value = 1.000; I2 = 0.000; Tau2 = 0.000; Stderr = 0.020). However, we found three CCT response patterns 5 minutes after anesthesia: Pattern 1, subjects with no significant changes in their CCT values (n = 14, 46.7%); Pattern 2, subjects with significant CCT increases (n = 11, 36.7%); and Pattern 3, subjects with significant CCT decreases (n = 5, 16.7%). In sum, there are no significant changes in the CCT after anesthesia, but there are three different CCT response patterns 5 minutes after anesthesia.

Repeatability of Central Corneal Thickness Measurement Using Rotating Scheimpflug Camera in Dry and Normal Eyes

PURPOSE

To compare the repeatability of central corneal thickness (CCT) measurement using the Pentacam between dry eyes and healthy eyes, as well as to investigate the effect of artificial tears on CCT measurement.

METHODS

The corneal thicknesses of 34 patients with dry eye and 28 healthy subjects were measured using the Pentacam. One eye from each subject was assigned randomly to a repeatability test, wherein a single operator performed three successive CCT measurements time points-before and 5 min after instillation of one artificial teardrop. The repeatability of measurements was assessed using the coefficient of repeatability and the intraclass correlation coefficient.

RESULTS

The coefficient of repeatability values of the CCT measurements in dry and healthy eyes were 24.36 and 10.69 μm before instillation, and 16.85 and 9.72 μm after instillation, respectively. The intraclass correlation coefficient was higher in healthy eyes than that of in dry eyes (0.987 vs. 0.891), and it had improved significantly in dry eyes (0.948) after instillation of one artificial teardrop. The CCT measurement fluctuated in dry eyes (repeated-measures analysis of variance, P<0.001), whereas no significant changes were detected in healthy eyes, either before or after artificial tear instillation.

CONCLUSIONS

Central corneal thickness measurement is less repeatable in dry eyes than in healthy eyes. Artificial tears improve the repeatability of CCT measurements obtained using the Pentacam in dry eyes.

Effect of supine body position on central corneal thickness

BACKGROUND

To evaluate the effect of supine body position on central corneal thickness (CCT) in open-angle glaucoma patients and in healthy subjects.

DESIGN

A cross-sectional study at a university eye clinic.

PARTICIPANTS

Twenty-three subjects were recruited in each group, for a total of 46 patients.

METHODS

CCT was measured using an ultrasound pachymeter in each subject. Three consecutive measurements in each eye were first taken in the sitting position, and repeated after 10 min and 30 min in a supine position. Results were analyzed using mixed model repeated measures, which adjusted for age, gender and laterality of eyes.

MAIN OUTCOME MEASURES

CCT RESULTS: In healthy subjects, CCT decreased with supine positioning at 10 min (mean = -5.2 µm, P = 0.0043) and at 30 min (mean = -6.5 µm, P < 0.0001). In the glaucoma group, CCT decreased with supine positioning at 10 min (mean = -6.7 µm, P = 0.0043) and at 30 min (mean = -10.2 µm, P < 0.0001). There was no statistically significant difference between the CCT at 10 min supine and at 30 min supine in the healthy subjects (P = 0.37) and glaucoma patients (P = 0.14). CCT was shown to decrease linearly over time (P < 0.0001), and the slopes were not statistically different between groups (P = 0.40).

CONCLUSIONS

CCT is a dynamic measurement that can be influenced by body position. It decreases linearly in the first 30 min of supine positioning at a similar rate in both open angle glaucoma patients and in healthy subjects.

The effect of oxybuprocaine on corneal thickness as measured with optical coherence tomography

Background: No previous study in South Africa has used optical coherence tomography (OCT) in assessing corneal thickness changes following the instillation of an anaesthetic.Aim: The purpose of this study was to investigate the short-term effects of oxybuprocaine 0.4% on corneal thickness.Setting: The study was conducted at a university eye clinic in Westville, KwaZulu-Natal.Methods: A total of 34 (N = 34) participants, of both genders, aged 18–25 years participated in the study. Data collection commenced once ethical clearance was obtained. Baseline measurements of central corneal thickness (CCT) (within 0 mm – 2 mm of the corneal apex) and mid-peripheral corneal thickness (MPCT) (within 2 mm – 5 mm of the corneal apex) were taken using the Optovue iVue 100 OCT. Measurements were obtained using the standard iVue 100 corneal pachymetry map. One drop of oxybuprocaine was then instilled using a sterile technique in the right eye (RE) of each participant. Central and MPCT measurements were obtained using the OCT at time intervals of 30 s for the first 2 min and then for 60-s intervals up until 5 min. Baseline central and MPCT were then measured for the left eye (LE) using the OCT. The effect of two drops of oxybuprocaine on CCT was also investigated on the left eye only using the same procedure as on the right eye.Results: There were minimal fluctuations of the CCT and MPCT in the 5 min following instillation of either one or two drops of oxybuprocaine. The fluctuation of both the CCT and MPCT was within 10 µm irrespective of dosage and returned to baseline thickness after 5 min.Conclusion: Clinically, short-term CCT and MPCT changes following the instillation of oxybuprocaine are not large enough to affect the accuracy of Goldmann applanation tonometry.

Corneal thickness differences between sexes after oxybuprocaine eye drops

PURPOSE

We aimed to analyze the corneal thickness (CT) values of female and male subjects before and after instillation of oxybuprocaine 0.4% anesthetic eye drops.

METHODS

The CT of 30 female subjects and 28 male subjects was measured using scanning-slit corneal topography (Orbscan Topography System II, Orbscan, Inc, Salt Lake City, UT). Measurements were carried out before and 3 minutes after the instillation of oxybuprocaine 0.4% eye drops.

RESULTS

The difference between the baseline values and those obtained after anesthesia ranged as follows: male subjects: central, -26 to +24 μm; superior, -24 to +23 μm; inferior, -19 to +20 μm; nasal, -25 to +30 μm; and temporal, -21 to +20 μm; female subjects: central, -16 to +24 μm; superior, -19 to +32 μm; inferior, -14 to +34 μm; nasal, -19 to +33 μm; and temporal, -36 to +16 μm. No significant differences were found in any corneal location in male subjects. The differences were significant at inferior (p = 0.001) and nasal (p = 0.011) corneal sites in female subjects.

CONCLUSIONS

Oxybuprocaine anesthetic eye drops induce significant CT increases in female subjects but not in male subjects.

Effects of inhaled fluticasone on intraocular pressure and central corneal thickness in asthmatic children without a family history of glaucoma

Purpose:

The aim of this study is to report the effects of fluticasone-inhaled corticosteroid on intraocular pressure (IOP) and central corneal thickness (CCT) of asthmatic children without a family history of glaucoma.

Materials and Methods:

In this prospective study, 93 children were divided into two groups: 69 asthmatic children with no family history of glaucoma who were taking inhaled fluticasone propionate 250 μg daily for at least 6 months (Group 1) and 24 age-matched control subjects without asthma (Group 2). Three measurements each, of IOP and CCT, were performed with a hand-held noncontact tonometer and a noncontact specular microscope, respectively, over a 12-week period. The order of IOP and CCT measured were randomized at each visit. Between-group comparison and the relationship between CCT and IOP measurements were investigated. P < 0.05 was statistically significant.

Results:

The mean age was 8 ± 2.4 years (range, 5–15 years) and 9 ± 2.9 years (range, 5–15 years) for Groups 1 and 2, respectively (P = 0.1337). The mean IOP was 14 ± 3.3 mmHg (range, 10–24 mmHg) and 14 ± 2.9 mmHg (range, 11–22 mmHg) for Groups 1 and 2, respectively (P = 0.3626). The mean CCT was 531 ± 30.1 μm (range, 467–601 μm) and 519 ± 47.0 μm (range, 415589 μm) for Groups 1 and 2, respectively (P = 0.1625). There was a weak but statistically significant correlation between IOP and CCT in Group 1 (Pearson's R = 0.3580, P = 0.0025).

Conclusions:

Inhaled fluticasone at the regular dose used in this study over a short period (6–24 months) was not associated with a significant effect on CCT and IOP measured with noncontact devices in asthmatic children between 5 and 15 years, without a family history of glaucoma. A weak correlation between IOP and CCT values in asthmatic children did exist.

Comparison of the influence of nonpreserved oxybuprocaine and a preserved artificial tear (thera tears) on human corneal thickness measured by two pachymeters

PURPOSE

To compare the effect of nonpreserved oxybuprocaine and preserved artificial tears on central corneal thickness (CCT) obtained by 2 pachymeters.

METHODS

In this prospective, placebo-controlled study, involving a random sample of 100 eyes of 50 subjects, aged 24±2.3 years, CCT readings were obtained in 2 separate sessions with the Topcon SP-3000P and ultrasound pachymetry (USP), respectively, before, 5 and 10 min after instillation of a drop each of either oxybuprocaine hydrochloride (oxybuprocaine HCl) (group 1) or carboxymethylcellulose sodium, thera tears (group 2), and placebo.

RESULTS

The baseline mean CCT for SP-3000P was 509±38 μm and 542±36 μm for USP. No statistical significant differences between baseline CCTs (P>0.05 for both devices) in both groups. In both group experimental eyes, neither SP-3000P nor USP-measured CCTs varied significantly from the control eyes at 5 (P>0.05) and 10 (P>0.05) mins postinstillation of drops in both sessions. In group one, the 95% confidence intervals (CIs) for the SP-3000P CCTs were similar at 5 (-16 to 17 μm) and 10 min (-16 to 17 μm), but in the USP-measured CCTs, it was wider at 10 min (-41 to 46 μm) than at 5 min (-30 to 41 μm) postinstillation. In group two, the 95% CIs at 5 and 10 mins postinstillation, respectively, ranged between -20 and 47 μm, -21 and 43 μm (SP-3000P) and -29 and 23 μm, -26 and 23 μm (USP). Within groups and between groups, variations in CCT were similar at both times intervals in all comparisons.

CONCLUSION

Although oxybuprocaine HCl and thera tears consistently did not affect the mean CCT obtained by both devices at both time intervals, variation in SP-3000P measured CCT was more consistent in both sessions and narrower in relation to USP-measured CCT. It may be reasonable to suggest that measurements of CCT in normal patients be taken before examinations requiring instillation of anesthetics or such measurements when obtained postinstillation of either oxybuprocaine or preserved artificial tears be interpreted with caution.

Changes in central corneal thickness values after instillation of oxybuprocaine hydrochloride 0.4%

PURPOSE

To assess the variation in central corneal thickness (CCT) following the instillation of oxybuprocaine hydrochloride (0.4%), in normal subjects.

METHODS

This was a randomized, prospective study of CCT measurements (before and after the instillation of topical anaesthesia) obtained with the Topcon SP-3000P noncontact specular microscope, in 60 eyes of thirty subjects. The subjects' mean age was 20±1 years (mean±SD). In each subject, one eye was treated with one drop of oxybuprocaine hydrochloride (HCl) and the fellow eye with one drop of normal saline (control). The SP-3000P CCT readings were first obtained before instillation (baseline) and monitored every 30 s after instillation of each eye drop for a period of 10 min.

RESULTS

The mean baseline CCT for oxybuprocaine was 526±23 μm. Ten minutes after, it was 526±24 μm. In the control, the mean CCT was 526±27 μm, 10 min after it was 526±28 μm. The mean variation in CCT measurement was -0.7±3.1 (5.5 to -6.8 μm, 95% CI) for oxybuprocaine and -0.6±4.1 μm (7.5 and -8.6 μm, 95% CI) for the fellow eyes (P>0.05). There was no significant variation among the 20 CCT columns for either oxybuprocaine or the control group (P>0.05 for both).

CONCLUSIONS

One drop of topical oxybuprocaine 0.4% did not cause a significant change in CCT at up to 10 min following instillation. However, higher differences were observed at 2.30 min and 4.30 min after instillation.

Effect of topical anesthesia on evaluation of corneal sensitivity and intraocular pressure in rats and dogs

OBJECTIVE

To determine the effect of 0.5% proparacaine in tonometry by evaluating corneal touch threshold (CTT) and intraocular pressure (IOP).

ANIMAL STUDIED

  Nine rats (18 eyes, Sprague-Dawley) and 10 dogs (20 eyes, Beagle)

PROCEDURES

The IOP and CTT were measured in each eye before and after topical anesthesia with 0.5% proparacaine. The IOP was evaluated using Tonopen for dogs and Tonolab for rats. The corneal sensitivity was evaluated by CTT through a Cochet-Bonnet aesthesiometer.

RESULTS

The mean IOP was not significantly changed in rats or dogs before and after topical anesthesia. However, after application of proparacaine, CTT was significantly increased in both animal groups compared with that before application of proparacaine.

CONCLUSION

  From this study, topical anesthesia was found to significantly lower the corneal sensitivity but have little effect on IOP measurements. In ophthalmologic examination, topical anesthesia can be used to reduce corneal sensation without an effect on IOP.

An indirect method to compare the reference centres for corneal measurements

PURPOSE

Corneal measurements are commonly presented with respect to a specific reference centre, but the location of the reference centre on the corneal surface could vary from one diagnostic modality to another. This study aimed to develop a method for comparing reference centres used by corneal measurement systems.

METHODS

An indirect method was developed to compare reference centres by making use of the pupil centre and its offset from the reference centre. Reference centres in a Scheimpflug imaging system, the Pentacam HR, and a Placido-ring corneal topography system, the ATLAS Corneal Topography System, were compared for the right and left eyes of 30 subjects. The subjects all had similar pupil sizes when measured by the two systems. Differences and correlations of the pupil centre offsets between the two systems were statistically tested and compared by Bland-Altman analyses.

RESULTS

There were no significant differences in mean pupil offsets between the two systems for either the right or left eyes (p > 0.05). There were strong correlations of the pupil centre offsets between the two systems for each eye (right eye x-axis: r = 0.95, p < 0.0001; right eye y-axis: r = 0.98, p < 0.0001; left eye x-axis: r = 0.96, p < 0.0001, left eye y-axis: r = 0.93, p < 0.0001). Bland-Altman analyses revealed no significant differences in pupil centre offsets between the two systems.

CONCLUSIONS

The Pentacam HR system and the ATLAS system have very similar reference centres. Thus it is possible to directly analyze data from the Pentacam HR and other instruments using the corneal vertex or the pupil centre as the reference centres due to the similarity in the reference centre settings between the two systems.

Effect of oxybuprocaine eye drops on corneal volume and thickness measurements

PURPOSE

To investigate the effect of oxybuprocaine eye drops on corneal volume (CV) and corneal thickness measurements.

METHODS

Central corneal thickness (CCT), corneal thinnest point (CTP), and CV of 78 eyes of 78 healthy volunteers were measured with Pentacam, before and 5 min after the administration of oxybuprocaine eye drops. The fellow non-anesthetized eyes were used as control.

RESULTS

Before topical anesthesia, the mean CCT was 546.76 ± 35.3 μm, after anesthesia, it was 547.76 ± 36.56 μm (p = 0.86). In the fellow eyes, the first mean CCT was 548.82 ± 35.2 μm and the second was 547.55 ± 35.9 μm (p = 0.82). The mean CTP before anesthesia was 543.99 ± 35.23 μm, after it was 544.89 ± 36.3 μm (p = 0.88). In the fellow eyes, the first mean CTP was 544.15 ± 35.35 μm and the second was 542.81 ± 36 μm (p = 0.81). Before topical anesthesia, the mean CV was 60.55 ± 3.84 mm, after it was 60.66 ± 3.97 mm (p = 0.86). In the fellow eyes, the first mean CV was 60.93 ± 3.87 mm and the second was 60.73 ± 4 mm (p = 0.75).

CONCLUSIONS

Oxybuprocaine eye drops do not appear to induce a significant corneal swelling and do not affect the measurements when comparing CCT measured with optical or ultrasound devices.

Intrasession and intersession repeatability of the Pentacam system on posterior corneal assessment in the normal human eye

PURPOSE

To study the intrasession and intersession repeatability of the Pentacam system (Oculus Inc.) in measuring the posterior corneal shape.

SETTING

School of Optometry, Hong Kong Polytechnic University, Hong Kong, China.

METHODS

The posterior corneal shape in 1 eye (randomly selected) was measured with the Pentacam system. Three consecutive readings were taken for intrasession repeatability analysis. Measurements were repeated 1 to 2 weeks later for intersession repeatability analysis. The anterior best-fit sphere (BFS) and posterior BFS at the 5.0 mm and 8.0 mm zones, as well as the elevation of the posterior cornea at these 2 zones, were compared.

RESULTS

The anterior and posterior BFS demonstrated good intrasession repeatability (Cronbach alpha > or = 0.997; intraclass correlation coefficients > or = 0.990). No significant difference was found between the 2 visits. The 95% limits of agreement of posterior BFS were 52.3 to -41.7 microm at the 5.0 mm zone and 66.1 to -60.9 microm at the 8.0 mm zone. The elevation was similar between the 2 visits. The 95% limits of agreement were 4.27 to -5.29 microm at the 5.0 mm zone and 5.33 to -5.77 microm at the 8.0 mm zone.

CONCLUSIONS

Pentacam provided good performance in assessing the posterior cornea. To improve the intersession repeatability, it is suggested that 3 consecutive readings, rather than 1 image, be taken to generate an average BFS for analysis. When comparing the posterior corneal elevation between sessions, an average BFS generated from the first visit should be used for elevation calculation.