Ultrasound Pachymetry Research Articles

Comparison of Central Corneal Thickness Measured by Tono-pachymetry and Ultrasound Pachymetry

Purpose: We compared the accuracy of central corneal thickness (CCT) measurements according to CCT measured by noncontact Tono-pachymetry and ultrasound pachymetry (USP). Methods: CCT was measured in 90 eyes of 90 subjects by two optometrists. The CCT measurements were compared and the correlations between the measurements were analyzed. To evaluate whether the measurements varied depending on CCT, the subjects were classified into three groups according to CCT (group 1: thin thickness group; group 2: medium thickness group; and group 3: thick thickness group). The differences in CCT obtained by the two devices (△CCT = Tono-pachymetry-USP) were compared and analyzed among the three groups. Results: The average CCT measurements by Tono-pachymetry and USP were 523.26 ± 32.93 μm and 527.08 ± 37.33 μm, respectively. CCT by Tono-pachymetry was significantly thinner than by USP (△CCT= -3.82 ± 15.34, p = 0.020). The two measurements were strongly correlated (r = 0.912, p < 0.001). The △CCT values were 5.40 ± 12.13 μm in group 1, -6.37 ± 15.07 μm in group 2, and -10.50 ± 14.39 μm in group 3 (p < 0.001). Conclusions: CCT measured by tono-pachymetry was thinner on average compared to the value measured by USP and the differences in measurements between the two devices were different according to CCT. The thinner the CCT, the thicker the measurement, and the thicker the CCT, the thinner the measurement. Therefore, this trend should be considered when interpreting tono- pachymetry results in clinical practice.

Corneal Biomechanical Parameters and Central Corneal Thickness in Glaucoma Patients, Glaucoma Suspects, and a Healthy Population.

Purpose: To evaluate and compare corneal hysteresis (CH), corneal resistance factor (CRF), and central corneal thickness (CCT), measurements were taken between a healthy population (controls), patients diagnosed with glaucoma (DG), and glaucoma suspect patients due to ocular hypertension (OHT), family history of glaucoma (FHG), or glaucoma-like optic discs (GLD). Additionally, Goldmann-correlated intraocular pressure (IOPg) and corneal-compensated IOP (IOPcc) were compared between the different groups of patients. Methods: In this prospective analytical-observational study, a total of 1065 patients (one eye of each) were recruited to undergo Ocular Response Analyzer (ORA) testing, ultrasound pachymetry, and clinical examination. Corneal biomechanical parameters (CH, CRF), CCT, IOPg, and IOPcc were measured in the control group (n = 574) and the other groups: DG (n = 147), FHG (n = 78), GLD (n = 90), and OHT (n = 176). We performed a variance analysis (ANOVA) for all the dependent variables according to the different diagnostic categories with multiple comparisons to identify the differences between the diagnostic categories, deeming p < 0.05 as statistically significant. Results: The mean CH in the DG group (9.69 mmHg) was significantly lower compared to controls (10.75 mmHg; mean difference 1.05, p < 0.001), FHG (10.70 mmHg; mean difference 1.00, p < 0.05), GLD (10.63 mmHg; mean difference 0.93, p < 0.05) and OHT (10.54 mmHg; mean difference 0.84, p < 0.05). No glaucoma suspects (FHG, GLD, OHT groups) presented significant differences between themselves and the control group (p = 1.00). No statistically significant differences were found in the mean CRF between DG (11.18 mmHg) and the control group (10.75 mmHg; mean difference 0.42, p = 0.40). The FHG and OHT groups showed significantly higher mean CRF values (12.32 and 12.41 mmHg, respectively) than the DG group (11.18 mmHg), with mean differences of 1.13 (p < 0.05) and 1.22 (p < 0.001), respectively. No statistically significant differences were found in CCT in the analysis between DG (562 μ) and the other groups (control = 556 μ, FHG = 576 μ, GLD = 569 μ, OHT = 570 μ). The means of IOPg and IOPcc values were higher in the DG patient and suspect groups than in the control group, with statistically significant differences in all groups (p < 0.001). Conclusion: This study presents corneal biomechanical values (CH, CRF), CCT, IOPg, and IOPcc for diagnosed glaucoma patients, three suspected glaucoma groups, and a healthy population, using the ORA. Mean CH values were markedly lower in the DG group (diagnosed with glaucoma damage) compared to the other groups. No significant difference was found in CCT between the DG and control groups. Unexpectedly, CRF showed higher values in all groups than in the control group, but the difference was only statistically significant in the suspect groups (FHG, GLD, and OHT), not in the DG group.

Fiabilité de la pachymétrie par OCT comparée à la pachymétrie par ultrasons

Measuring the central corneal thickness is an important step in the diagnosis and monitoring of glaucoma. Ultrasound pachymetry was the gold standard before the advent of OCT. The purpose of this study is to assess the reliability of OCT pachymetry compared to ultrasound pachymetry in black patients. Pachymetry was performed as part of a glaucoma work-up. Ultrasonic pachymetry was measured using the Alcon Ocuscan by the same operator and OCT pachymetry using the Topcon 2000 OCT. The Student's t-test was used to compare means with statistical significance of 5%. The Pearson's correlation coefficient (r2) was used to measure correlations. One-hundred thirty-five right eyes and 135 left eyes, corresponding to 270 eyes of 135 patients, were examined. There was a female predominance (59 men/76 women), with a gender ratio of 0.78. The mean age was 42.3±17.3 [8-86] years. In the right eye, the mean OCT pachymetry was 522.4±36.8μ versus 528.2±37.9μ for ultrasonic pachymetry (P=1.00). In the left eye, the mean OCT pachymetry was 522.0±33.8μ versus 524.9±42.5μ for ultrasonic pachymetry (P=1.00). The overall mean OCT pachymetry was 522.2±35.2μ versus 526.5±40.2μ, with a non-significant difference (P=1.00). There was a strong correlation between ultrasonic pachymetry and OCT pachymetry (r2=0.83; P<0.05). On the other hand, there was a very low correlation between pachymetry and age (r2=0.09; P<0.05). Pachymetry decreased by 5μ per 10 years, corresponding to corneal thinning of 0.5μ per year. OCT pachymetry can be a reliable alternative to ultrasound pachymetry and could be performed at the same time as the OCT for glaucoma assessment.

Comparability of corneal thickness and opacity depth assessed by OCT and UBM.

To compare the measurement of central thickness and depth of involvement of opacity-bearing corneas at different intensities (mild, moderate, and dense) using different instruments: Visante and Optovue OCTs, ultrasound biomicroscopy (UBM), and ultrasound pachymetry (central thickness). Sample of 102 eyes: 70 eyes (68.63 %) with corneal opacity; 32 eyes (31.37%) with normal corneas. Corneal opacity grading included mild (28 eyes, 40.00 %), moderate (27 eyes, 37.57 %), and dense (15 eyes, 21.43 %). Opacity intensity was graded and documented. Central corneal thickness was determined using Optovue and Visante OCTs, ultrasound pachymetry, and UBM VuMax (50 MHz), and depth of corneal opacity, using Optovue and Visante OCTs and UBM. Total corneal thickness of the control group showed differences with a small correction factor using Optovue OCT (534.03 ± 39.88 μm), Visante OCT (523.72±38.70 μm), and ultrasound pachymetry (529.84 ± 39.76 μm), and were higher when compared to UBM (492.06 ± 37.93 μm). In mild opacity, depth measurements were the same with OCT Optovue and Visante and higher than those by UBM. In moderate opacities, there were no differences in measurements by different instruments. In dense opacities, OCT Optovue and Visante measurements were the same and higher than those by UBM. Central corneal thickness measurements were considered higher in corneas with opacity than in normal corneas. We observed that the greatest thicknesses were measured in corneas with dense opacities. There was a difference between the measurements taken by different instruments, both in central thickness and in opacity depth in cases of mild and dense opacity, and no difference in moderate opacity.

Sirius Scheimpflug\u2013Placido versus ultrasound pachymetry for central corneal thickness: meta-analysis

BackgroundTo compare the difference in central corneal thickness (CCT) measurements in normal eyes between a rotating Scheimpflug camera combined with a Placido-disk corneal topographer (Sirius, CSO, Italy) and ultrasound pachymetry (USP).MethodsA systematic literature search was conducted for relevant studies published on PubMed, Medline, EMBASE, and the Cochrane Library and ClinicalTrials.gov from inception to August 1st, 2019. Primary outcome measures were CCT measurements between Sirius and USP. A random effects model was used to pool CCT measurements.ResultsA total of twelve studies involving 862 eyes were included in this meta-analysis. The meta-analysis found CCT measurements between Sirius and USP to be statistically significantly different (P < 0.0001). The mean difference between Sirius and USP was −11.26 μm with a 95% confidence interval (CI) (−16.92 μm, −5.60 μm). The heterogeneity was I2 = 60% (P = 0.004).ConclusionCCT measurements with the Sirius Scheimpflug-Placido topographer were statistically significantly lower than USP. However, it may be argued that the mean difference of 11.26 μm is not a clinically significant difference.

Comparison of central corneal thickness and intraocular pressure measured with two different tono/pachymeter devices in non-glaucomatouse children.

The goal of this research is to compare the intraocular pressure (IOP) and the mean central corneal thickness (CCT) values obtained from the measurements with Nidek NT-530P and Canon TX-20P devices with the values obtained by ultrasound pachymetry (UP) and Goldmann applanation tonometry (GAT) in children. This prospective study was conducted with 119 healthy children. The measurements were repeated three times for each eye. The intraclass correlation coefficient (ICC) was used to assess the correlation between the measurements obtained from different devices. The Bland-Altman plot was used to analyze the agreement between two different devices graphically. The measurements were taken in the same order in all subjects: TX-20P, NT-530P, UP, and GAT. The mean age of the children was 10.1 ± 3.2 (6-17) years. The mean CCT values for the eyes were 568.90 and 569.68 (TX-20P), 571.44 and 566.37 (NT-530P), 564.77 and 564.67 μm UP, (right and left, respectively). The highest correspondence observed for CCT was between UP and NT-530P devices (ICC, 0.982, the left eye). The mean IOP measurements for Canon TX-20P, NT-530P, and GAT were 16.5 ± 3.2, 16.3 ± 3.2, and 16.8 ± 3.6 mmHg for the right eyes, respectively, while those for the left eyes were 16.6 ± 3.1, 16.2 ± 3.3, and 16.8 ± 3.7 mmHg. The highest correspondence was noted between measurements obtained using GAT and Nidek NT-530P devices (ICC, 0.945, in the left eye). Tono/pachymetry devices in the healthy children are provides significant agreements with the gold standard methods for IOP and CCT measurements.Clinical Trial Registration number: 2016-94.

Corneal Cross-linking at the Slit Lamp.

To describe a new surgical technique where corneal cross-linking (CXL) (to treat corneal ectasias) and photo-activated chromophore for keratitis-CXL (PACK-CXL) are performed while the patient is seated in an upright position at the slit lamp. Topical anesthesia is applied in the waiting room, 10 minutes before the procedure. Once in the office or procedure room, eyelids and periorbital areas are disinfected with chloramphenicol and the patient is seated at the slit lamp. Epithelial debridement is performed with a cotton swab soaked in freshly prepared 40% ethanol, using 70 seconds of tapping, followed by gentle pressure to remove the epithelium. The patient is placed in the supine position for riboflavin application for 10 minutes. Stromal thickness is assessed using ultrasound pachymetry after 5 and 10 minutes. Finally, the patient is returned to the slit lamp to receive ultraviolet irradiation. CXL at the slit lamp is an easy-to-perform technique that substantially reduces the infrastructure needed to perform CXL and PACK-CXL procedures. A significant advantage of allowing CXL treatment at the slit lamp is that CXL technology can now be used in clinics that do not have easy access to an operating room infrastructure. Slit-lamp CXL can also reduce procedure costs by eliminating the technical fees related to the use of an operating room, making this treatment not only more accessible for patients, but also affordable. [J Refract Surg. 2021;37(2):78-82.].

Evaluation of the Difference between Predicted and Measured Central Corneal Thickness Reduction after SMILE and Femtosecond Laser-assisted LASIK for Myopia

ABSTRACT Purpose To evaluate the agreement between the predicted and measured central corneal thickness (CCT) reduction after the small incision lenticule extraction (SMILE) surgery and femtosecond laser-assisted in situ keratomileusis (FS-LASIK) surgery. Methods A total 165 patients were enrolled in this prospective study. Eighty patients with a mean spherical equivalent (SE) of −4.72 ± 1.80 Diopters (D) were treated with the FS-LASIK procedure and Eighty-five patients with a mean SE of −4.78 ± 1.63 D were treated with SMILE procedure. One eye for each patient was randomly selected and included for statistical analysis. Ultrasound pachymetry measurement and Scheimpflug camera corneal topography were performed preoperatively and 3 months postoperatively. The measured CCT reduction was calculated by comparing the preoperative examinations with postoperative examinations. Comparative statistics and linear regression analyses were performed. Results The mean predicted CCT reduction was 95.02 ± 21.39 μm in FS-LASIK group and 103.49 ± 22.87 μm in SMILE group (P = .015). The prediction of laser platform was found to overestimate the measured CCT reduction for both FS-LASIK group (ultrasound 13.20 ± 9.34 μm) and SMILE group (ultrasound 13.12 ± 8.68 μm). The prediction of laser platform was found to systematically overestimate the measured CCT reduction in FS-LASIK group. In SMILE group, the difference between predicted and measured CCT reduction were found significantly related with the predicted CCT reduction (P < .001 for ultrasound; and P = .004 for Pentacam). Conclusion A systematic overestimation of measured CCT reduction in FS-LASIK group did not influence the refractive precision of FS-LASIK. Due to the different biomechanical distributions in post-SMILE cornea, the measured CCT reduction was influenced as the changes in refractive correction. Nomogram adjustment for high myopic correction needs further research.

Comparison of central corneal thickness measured by noncontact tonometry and ultrasound pachymetry

PurposeTo compare and analyze central corneal thickness (CCT) as measured by ultrasound pachymetry(USP) with noncontract tonometry(NCT) TX‐20P, which involves the function to measure central corneal thickness.MethodsThe central corneal thickness was measured in 45 eyes of 26 glaucoma patients and in 84 eyes of 43 healthy patients by two optometrist. First, noncontact tonometry TX‐20P was used to measure the CCT, followed by measurements taken using ultrasound pachymetry later. The results were compared and the correlations between two devices were analyzed. To determine whether the measurements vary depending on use of anti‐glaucoma eyedrops, all subjects were classified into two groups. Then, the difference of the CCT measured by the two devices was analyzed.ResultsThe average measurements of central corneal thickness using ultrasound pachymetry and noncontact tonometry TX‐20P were 529.07 ± 40.40 μm and 526.26 ± 35.30 μm, respectively. The central corneal thickness by ultrasound pachymetry was thicker than by noncontact tonometry TX‐20P. There was statistically significant differences between the measurements (p &lt; 0.001) and the two exams showed high degree of linear correlation(r = 0.919, p &lt; 0.001). The difference of central corneal thickness between two devices was 2.80 ± 19.00 μm in group 1 and 2.81 ± 14.29 μm in group 2. The difference between two groups was not statistically significant (p = 0.997).ConclusionsThis study showed that the results using ultrasound pachymetry and noncontact tonometry TX‐20P had significant positively correlation with each other regardless of using anti‐glaucoma eyedrops.

Comparison of Six Methods of Central Corneal Thickness Measurement in Healthy Eyes.

Objectives:Several methods of measuring central corneal thickness (CCT) have been compared, however, the data are still limited and conflicting. The aim of this study was to determine the agreement of CCT measurements performed in healthy eyes using ultrasound pachymetry (USP), non-contact tono/pachymetry, specular microscopy, biometry, Scheimpflug-based corneal topography, and optical coherence tomography (OCT).Methods:All of the participants underwent a complete ophthalmological examination. The CCT of all of the eyes included was measured using 6 different methods. The agreement between the methods was analyzed using the mean difference and Bland-Altman analysis based on a 95% limits of agreement.Results:A total of 64 patients with a mean age of 40.96±14.52 years (range: 20-78 years) were included in the study. The mean CCT value was 552.10±35.65 µm, 550.40±35.55 µm, 554.67±35.49 µm, 545.39±34.21 µm, 546.25±35.49 µm, and 552.64±33.59 µm using USP, non-contact tono/pachymetry, non-contact specular microscopy, biometry, Scheimpflug-based corneal topography, and OCT, respectively. The bias values determined by Bland-Altman plots were -1.70, -2.56, 6.71, 5.85, and -0.53 for tono/pachymetry, specular microscopy, biometry, topography, and OCT, respectively. OCT demonstrated the lowest bias compared to USP. The overall intraclass correlation coefficient was 0.961 (range: 0.945-0.974) with a 95% confidence interval.Conclusion:All of the CCT measurements obtained using non-contact tono/pachymetry, non-contact specular microscopy, biometry, Scheimpflug-based corneal topography, and OCT were consistent with the USP measurements of healthy controls. Larger prospective studies to determine the interchangeability of different methods for CCT measurements in pathological conditions are warranted.

Central corneal thickness and intraocular pressure in primary open angle glaucoma suspects in a south Indian population. Is it time for “corneal anthropology”?

To study correlation between central corneal thickness (CCT) and intraocular pressure (IOP) in the primary open angle glaucoma (POAG) suspects and to assess the importance of the local population reference CCT in pachymetry adjusted IOP.Prospective, cross sectional study.A total of 100 patients aged 40-70 years of age diagnosed as POAG suspects were included. CCT measurements using ultrasound pachymetry and IOP measurement with Goldmann applanation tonometer (GAT) was done. IOP was corrected to the local south-Indian baseline CCT and also to the International CCT and comparison was done.The study included 100 patients (58 male and 42 female) with mean age of 51.7 ± 6.1 years. The mean CCT was 518.91 ± 24.26 μm, 522.19 ± 21.56 μm among females, males respectively. The mean uncorrected IOP (GAT) was 19.50 mmHg, 20.14 mmHg (right, left sides). Significant, moderate positive correlation between CCT and IOP was observed. The two groups i.e mean IOP corrected for South-Indian CCT (Mean_CX_IOP) versus IOP corrected for CCT international (Mean_CX_INT_IOP) showed significant difference. The mean IOP in Indian CCT corrected group was 19.76 ± 2.81 mmHg and in international CCT group was 21.51 ± 2.83 mmHg. Levene's test indicated significant difference in mean IOP of 2 groups (p=0.000).CCT is an important parameter in glaucoma management and known to vary in different ethnic groups. Local ethnicity specific CCT should be used in IOP correction with the help of anthropologists.

To study the relation between central corneal thickness, intro ocular pressure and visual field changes in primary open angle glaucoma

To correlate 3 important factors central corneal thickness, intraocular pressure and visual field changes in the POAG suspects which it helps to predict the onset of POAG and in early diagnosis.In this prospective study, a total 100 patients from 40 to 70 years of age diagnosed as PAOG suspects were included in the study. Slit lamp bio microscopy, ultrasound pachymetry was done to measure CCT and IOP was measured with Goldman applanation tonometer the visual field assessment was done with the octopus field analyser.The patient population consisted of 42 females and 58 males with average age of 51.7 years. Significant and moderate positive correlation between the CCT and IOP was observed for the right side (r)=0.39 and left side(r)=0.36 statistically significant (P=0.001). In our study highest percentage of abnormal (glaucomatous) visual field changes was seen in eyes with low CCT (&amp;#60;510µm) (P=0.008). Mean corrected IOP reading was 21.43 mmHg for the 14 patients with abnormal visual fields on right side and this was statistically significant at P=0.01.Thinner corneal readings in south Indian population especially when presenting at younger age should alarm the ophthalmologist to evaluate the patient thoroughly for glaucoma and should be followed up for the progression of glaucoma.

Repeatability and agreement of corneal thickness measurements by three methods of pachymetry in small incision lenticule extraction eyes

ABSTRACT Background: The accurate evaluation of corneal thickness (CT) post small incision lenticule extraction (SMILE) is clinically relevant to reduce the risk of complications. We aimed to analyze repeatability and agreement of central corneal thickness (CCT), thinnest corneal thickness (TCT), and mid-peripheral corneal thickness (MPCT) measurements using Scheimpflug imaging, anterior segment swept-source optical coherence tomography (AS-SS-OCT, CASIA 1000, Tomey), and ultrasound pachymetry (USP, SP-3000, Tomey) in eyes with previous SMILE. Methods: Ninety-one eyes of 91 patients were included. Within-subject standard deviation (Sw), test-retest repeatability (TRT), intraclass correlation coefficient (ICC), and coefficient of variation (CoV) were used to evaluate repeatability. Agreement was assessed by repeat-measurement analysis of variance and Bland–Altman analysis. Results: The above three instruments revealed that Sw was <5.91 µm, CoV was <1.08%, TRT was <16.38 µm, and ICC was >0.94. The 95% limits of agreement were relatively narrow and Bland–Altman plots were more concentrated at the CCT, at the TCT, and at the CT2mm. However, it was shown to be wide at the CT5mm. Conclusions: The three devices provide good repeatability of CT measurements in patients who undergone SMILE. Agreement between measurements at the CCT, TCT, and CT2mm were high, but measurement agreements among CT5mm revealed poor agreement.

Comparison of Central Corneal Thickness Measurements between Angiovue Optical Coherence Tomography, Ultrasound Pachymetry and Ocular Biometry

Purpose: To compare central corneal thickness (CCT) measurements and their reproducibility when taken by Ultrasound Pachymetry, Ocular Biometry and Angiovue Optical Coherence Tomography (OCT).&#x0D; Methods: Twenty-five healthy volunteers were recruited creating a sample size of 50 eyes. All subjects had pachymetric measurements by Ultrasound pachymetry (PachPen Handheld Pachymeter, Keeler Instruments Inc), Ocular biometry (IOL Master 700 Swept Source Biometry, Zeiss) and Angiovue Optical Coherence Tomography (Optovue Avanti RTVue XR Angiovue). The measurements of central corneal thickness for the three devices were taken by the same examiner twice for more accuracy.&#x0D; Results: The average measurements of central corneal thickness by Ultrasound pachymetry (PachPen Handheld Pachymeter, Keeler Instruments Inc), Ocular biometry (IOL Master 700 Swept Source Biometry, Zeiss) and Angiovue Optical Coherence Tomography (Optovue Avanti RTVue XR Angiovue) were 547.26 μm, 551.36 μm, and 536.42 μm, respectively. The mean standard deviation (SD) of repeated measurements by Ocular biometry was 48.87 μm, which was greater than the mean SD of 44.24 μm and 40.35 μm (P &lt; 0.001) by ultrasound pachymetry and Angiovue optical coherence tomography, respectively. There were statistically significant differences in the measurement results among the 3 methods (Ultrasound pachymetry vs. Ocular biometry P = 0.019; Ultrasound pachymetry vs. Angiovue Optical Coherence Tomography; P &lt; 0.001; Ocular biometry vs. Angiovue Optical Coherence Tomography P &lt; 0.001). There was a significant linear correlation between the Ultrasound pachymetry and Ocular biometry (r = 0.945, P&lt;0.001), Ultrasound pachymetry and Angiovue Optical Coherence Tomography (r = 0.895, P&lt;0.001), and Ocular biometry and Angiovue Optical Coherence Tomography (r = 0.902, P&lt;0.001).&#x0D; Conclusion: Central corneal thickness readings were comparable between PachPen Handheld Pachymeter, IOL Master 700 Biometry and Angiovue Optical Coherence Tomography; Angiovue optical coherence tomography gave significantly smaller values. The measurements of the 3 methods showed significant linear correlations with one another. All methods provided acceptable repeatability of measurements.

Factors affecting central corneal thickness measurement agreement between Scheimpflug imaging and ultrasound pachymetry in keratoconus

PurposeTo evaluate the agreement of central corneal thickness (CCT) measurement between Scheimpflug imaging and ultrasound (U/S) pachymetry in keratoconic eyes, and investigate factors that affect the agreement.MethodsThis post hoc analysis...

To study the correlation between type 2 diabetes mellitus and central corneal thickness

To study the correlation between type 2 diabetes mellitus and central corneal thickness in patients coming to the outpatient department of Dr. B.R. Ambedkar Medical College and Hospital. This prospective case control study was conducted over a period of 1 year from June 2018 to June 2019 at DR. B. R. Ambedkar Medical College and Hospital, Bangalore. A total of 120 patients were enrolled in the study. Among them, 60 patients had type 2 diabetes mellitus and 60 patients were non diabetics. Detailed ophthalmic examination was conducted in all patients and Central corneal thickness was measured using ultrasound pachymetry. In our study, 120 patients were enrolled including 60 diabetics and 60 non diabetics. The mean central corneal thickness in diabetics was 56722µ and in non diabetics it was 520 23µ. The difference between cases and control group was found to be clinically significant.According to our study, the patients with type 2 diabetes mellitus were found to have thicker corneas as compared to non diabetics.

Comparative Study of Corneal Thickness before and after FemtoLasik Surgery with Pentacam® AXL and Ultrasound Device (Tomey SP-100)

Aims: The purpose of our research is to evaluate corneal thickness, pre-operative and post-operatively after FemtoLasik surgery, using “Pentacam® AXL” and Ultrasound device. To evaluate the correlation of the two devices and their interchangeability.&#x0D; Sample and Study Design: Our data includes 70 eyes of patients, age 19- 59 years, who undergone Lasik surgery for myopia. The data concerned pre-operative and post-operative central corneal pachymetry using Ultrasound pachymeter (Tomey SP-100) and “Pentacam® AXL”.&#x0D; Methodology - Place and Duration of Study: University of West Attica Dept Biomedical Science Course Optics &amp; Optometry in collaboration with Private Ophthalmology Clinic “Athens Opthalologiko” during the period between May 2018 until September 2018. In this study, a comparison of data taken with Pentacam and Ultrasound was performed concerning central corneal thickness before and after FemtoLasik to evaluate the correlation of these devices. All the FemtoLasik surgeries were performed by the same experienced surgeon in order to ensure good repeatability of surgical procedures and all the patients selected had healthy eyes with no other ophthalmic pathology or systemic disease and myopia ranging from -1.00 to 9.25 Diopters. All patients were measured one month after FemtoLasik having achieved 6/6 visual acuity.&#x0D; Results: Central corneal thickness before FemtoLasik measured by ultrasound device had an arithmetic mean value of 552.43 μm ± SD 26.95. The thickness preoperatively with “Pentacam” had an arithmetic mean value of 556.26 μm ± SD 27.82. The corneal thickness after Lasik measured by ultrasound device had an arithmetic mean value of 493.21μm ± SD 36.30, while for “Pentacam” the arithmetic mean value was 499.07μm ± SD 36.17. The two devices correlate strongly (0.9218 and 0.9986 respectively with significant level P&lt;0,0001)&#x0D; Conclusion: Our conclusions after statistical analysis are that Ultrasound pachymetry and “Pentacam” topography correlated strong.

The Mont Blanc Study: The effect of altitude on intra ocular pressure and central corneal thickness.

The aim of the Mont Blanc Study was to investigate the relationship between intraocular pressure (IOP), central corneal thickness (CCT), and altitude in healthy subjects. Thirty-three eyes of 33 healthy volunteers (mean age: 24.8 years, 17 females) had their IOP measured with Perkins and I-Care tonometers and their CCT using ultrasound pachymetry at three locations in Italy with different altitudes: Pavia, (PV), 77 meters above sea level (a.s.l); Courmayeur (CM), 1300 meters a.s.l; Pointe Helbronner (PH), 3466 meters a.s.l.). The measurements were performed at 9 am, 11 am, 1 pm and 3 pm (±30') in indoor settings (mean temperature of 19°C) in PV and PH. At 9 am, CCT and IOP were measured outdoor (mean temperature of -1.4°C) at PH. The mean values of the IOP curve decreased from PV to PH with the Perkins (p = 0.02) and I-Care tonometers (p = 0.001). Instead, CCT increased upon ascension from PV to PH (p = 0.01), and from CM to PH (p = 0.002). When exposed to sub-zero temperature, the IOP increased (p<0.001), while the CCT did not change (p = 0.30). The results suggest that IOP significantly decreased and CCT significantly increased upon ascension from the sea level to higher altitudes.

Comparison between OrbscanIIz, Pentacam, Ultrasound Pachymetry (Tomey SP-100) at Different Stages of Keratoconus

Aims: To compare results of OrbscanIIz and Pentacam and Ultrasound pachymetry at different stages of keratoconus on corneal thickness.&#x0D; Sample and Study Design: 94 keratoconic patients participated in the study, of which 52 were men and 42 women. Keratoconus patients were measured with OrbscanIIz, Pentacam and Ultrasound pachymetry in pre-operation examinations for corneal collagen cross-linking. The patients belong to different keratoconus stages.&#x0D; Place and Duration of Study: University of West Attica Dept Biomedical Sciensce Course Optics &amp; Optometry in collaboration with Athens “Ophthalmologico” Clinic during the period between October 2017 to January 2019.&#x0D; Methodology: Corneal Pachymetry maps correlation of three types of corneal pachymeters OrbscanIIz, Pentacam and Ultrasound pachymetry (Tomey SP-100 Pachymeter). The measurements of the thinnest point of the cornea from each patient were collected at different stages of keratoconus and compared.&#x0D; Results: A sample of 188 eyes were measured at different stages of keratoconus and compared for the thinnest corneal thickness with three different measurement systems, OrbscanIIz ,Pentacam and Ultrasound pachymetry. At sublinical stage Orbscan-Pentacam had Correlation coefficient r=0,7971, Orbscan-Ultrasound r=0,7483 and Pentacam-Ultrasound r=0,9442. At 1st stage Orbscan-Pentacam had Correlation coefficient r=0,8913, Orbscan-Ultrasound r=0,8151 and Pentacam-Ultrasound r=0,8151. At 2nd stage Orbscan-Pentacam had Correlation coefficient r=0,9339, Orbscan-Ultrasound r=0,8819 and Pentacam-Ultrasound r=0,9633. For 3rd stage Orbscan-Pentacam had Correlation coefficient r=0,8317, Orbscan-Ultrasound r=0,8457 and Pentacam-Ultrasound r=0,9633. For 4th stage Orbscan-Pentacam had Correlation coefficient r=-0,4655, Orbscan-Ultrasound r=0,3089 and Pentacam-Ultrasound r=0,9633. In Iatrogenic keratoectasiaafter refractive surgery Orbscan-Pentacam had Correlation coefficient r=0,9327, Orbscan-Ultrasound r=0,3089 and Pentacam-Ultrasound r=0,9859.&#x0D; Conclusion: Statistical differences between OrbscanIIz, Pentacam and Ultrasound pachymetry were found for corneal thickness in all stages of keratoconus for the thinnest point measured. Orbscan-Pentacam have statistical significant differences but weak to moderate correlation. Orbscan-Ultasound have also statistical significant differences their correlation is very weak, while Pentacam-Ultrasound have statistical significant differences smaller as the previous but their correlation is very strong at all stages of keratoconus.

Comparison of central corneal thickness measurement by scanning slit topography, infrared, and ultrasound pachymetry in normal and post-LASIK eyes.

To compare central corneal thickness (CCT) measurements by scanning slit topography (SST), infrared pachymetry (IRP), and ultrasound pachymetry (USP), and their agreement in normal and post-laser in situ keratomileusis (LASIK) eyes. Sixty normal and 35 post-LASIK subjects were recruited. Only one eye from each subject was analyzed. Non-contact pachymetry was performed first, and the order for SST (Orbscan IIz) and IRP (Tonoref III) was randomized for each patient, to be followed by contact USP (Echoscan US-4000). Pearson's correlation, paired t test, and Bland-Altman plots were used to investigate association, difference, and agreement among different instruments respectively. The measurements obtained with the instruments were highly correlated. Compared to CCT determined by USP (CCTUSP), CCT determined by SST (after correction with acoustic factor) (CCTSSTC) was thicker by 7µm in normal eyes (P < 0.001). There was no significant difference between CCTSSTC and CCTUSP (P = 0.128), but a thickness-dependent deviation in post-LASIK eyes (P = 0.003). The CCT determined by IRP (CCTIRP) was thicker than CCTUSP in normal (P < 0.001) and post-LASIK eyes (P < 0.001) and demonstrated proportional overestimation with thinner corneas, with less predictable ultrasonic equivalent corneal thickness in normal eyes. Conversely, CCTIRP significantly underestimated CCT compared to CCTSST and showed increasing underestimation with thinner corneas in both normal and post-LASIK eyes (both P < 0.001). Central corneal thickness determined by SST, IRP and USP were not interchangeable or interconvertible, probably attributed to difference in methodologies. Compensation with algorithms may improve agreements amongst instruments.