Pachymetric Measurements Research Articles

TOWARDS A TREATMENT FOR DIABETIC RETINOPATHY: Intravitreal Toxicity and Preclinical Safety Evaluation of Inducible Nitric Oxide Synthase Inhibitors.

The purpose of this study is to determine the maximum tolerated dose of a single intravitreal injection of aminoguanidine and 1400W, 2 inhibitors of inducible nitric oxide synthase, in rabbit eyes. Inhibition of inducible nitric oxide synthase has already been shown to be beneficial in various animal models of diabetic eye disease. Groups of 4 New Zealand white rabbits were injected with balanced salt solution in the right eye and a single dose of either aminoguanidine (5, 1, 0.25 mg) or 1400W (2 mg and 0.4 mg) in the left eye. Toxicity was assessed by slit-lamp and fundus examination, intraocular pressure and pachymetric measurements, and electrophysiologic and histologic analysis. Eyes injected with high doses of aminoguanidine (5 mg) or 1400W (2 mg) demonstrated severe retinal vascular attenuation and infarction. Lower doses of intravitreal aminoguanidine (1 mg) and 1400W (0.4 mg) caused no significant toxic ocular effects in rabbit eyes. If the difference in vitreal volume between rabbit eyes and human eyes is taken into account, aminoguanidine (2.7 mg) and 1400W (1 mg) would be reasonable intravitreal doses to test for safety and efficacy in early clinical trials.

Repeatability and Agreement of Orbscan II, Pentacam HR, and Galilei Tomography Systems in Corneas With Keratoconus

To assess the repeatability and agreement of keratometry and pachymetry measurements obtained using 3 tomographers in eyes with keratoconus. Reliability analysis. setting: Institutional. Fifty eyes of 50 participants with keratoconus. observational procedure: Steep keratometry, flat keratometry, central corneal thickness (CCT), and thinnest corneal thickness (TCT) measurements using Galilei, Orbscan II, and Pentacam HR. Repeatability was assessed using within-subject standard deviation (SW), coefficient of variation (CV), and intraclass correlation coefficient (ICC). Bland-Altman plots and 95% limits of agreement (LoA) were used to evaluate agreement between device pairs. For all studied parameters, ICC was >0.97 with the least repeatable measurements obtained using Orbscan II. Mean steep keratometry values were similar while mean flat keratometry values were significantly different between all devices. The Galilei and Pentacam HR had the lowest 95% LoA for both CCT and TCT. There were no significant differences in mean CCT between Galilei and Pentacam HR. Mean Orbscan II CCT measurements were not significantly different overall but had wide 95% LoA with Pentacam HR (-47.95 to 58.09μm) and Galilei (-43.70 to 53.91μm). Mean Orbscan II CCT measurements were significantly lower when an acoustic factor of 0.92 was applied (-33.6μm vs Pentacam HR, P < .001;-33.6μm vs Galilei; P < .001). Keratometric and pachymetric measurements of keratoconic eyes obtained by Galilei, Orbscan II, and Pentacam were disparate. Measurements were less repeatable with Orbscan II compared with Pentacam HR and Galilei, although overall repeatability was high for all instruments.

Assessment of Corneal Parameters in Patients with Constitutional Thinness Using Scheimpflug Imaging

ABSTRACTPurpose: To assess corneal parameters in constitutional thinness (CT) subjects and to compare them with those of healthy individuals. Methods: Twenty-four CT subjects (BMI < 18.5 kg/m2) and 24 healthy subjects (BMI: 18.5–25 kg/m2) were enrolled in this observational cross-sectional study. All participants were screened for age, gender, and medical history, then underwent a detailed ophthalmological examination. Corneal parameters were evaluated by Scheimpflug imaging. Height and weight of all subjects were measured and body mass index (BMI) was calculated. Results: The mean corneal thicknesses at the apex point, the center of pupil, the thinnest point, and the mean corneal volume were significantly lower in CT patients than those of controls. The mean intraocular pressure (IOP) was significantly lower in CTs than in controls. There was a significant correlation between BMI and IOP, and BMI was significantly correlated with all pachymetric measurements and corneal volume. Conclusion: Corneal thicknesses were significantly thinner in CT subjects compared to those in control subjects. The impact of constitutional thinness on corneal parameters should be further investigated.

The Results of Cross-Linking With Riboflavin/UV-A in Patients With Progressive Keratoconus

Objective: To evaluate the results of corneal cross-linking with UV-A/riboflavin in patients with progressive keratoconus. Methods: Forty-seven eyes of 30 patients with progressive keratoconus (16 female, 14 male) were included in the study. Uncorrected and the best corrected distance visual acuities, biomicroscopic findings, intraocular pressure measurements, fundoscopic findings, pachymetric measurements and corneal topography parameters were recorded for each patient. Results: The mean age of the patients was 18.3±5.34 (range: 8-31) years and the mean follow-up duration was 7±2.4 (range: 3-12) months. Following the procedure, the mean decrease in K1, K2, Kav, spherical and cylindrical values were 0.77 D, 0.85 D, 0.80 D, 0.50 D and 0.74 D, respectively (p<0.05). There were no cases with decrease in visual acuity and significant complication during or after the treatment. Conclusion: Cross-linking with riboflavin/UV-A in patients with progressive keratoconus is an effective procedure. In addition, the preservation of visual acuity and not seen a significant complication indicate that a safe metod. However, large prospective randomized controlled studies are needed to evaluate the long-term effects of this treatment. Key words: corneal cross-linking, keratoconus, corneal topography

Evaluation of the Anterior Segment Parameters of the Patients with Scleroderma

ABSTRACTPurpose: To evaluate corneal parameters of scleroderma (SC) patients by Pentacam-HR.Methods: Twenty-two eyes of 22 SC patients and 33 eyes of 33 control subjects were enrolled. All participants underwent Pentacam (Pentacam-HR, Oculus, Germany) evaluation. Both SC and control groups were divided into two subgroups as dry eye (DE) (Schirmer test with topical anesthesia (STA) ˂5 mm) and without DE (STA ˃5 mm).Results: Pachymetric measurements and mean corneal volume (CV) were significantly lower in the SC group than in the control group (p<0.001). Pachymetric measurements and CV of SC patients with DE were significantly lower than all the other subgroups. Control subgroups with or without DE were similar in pachymetric measurements and CV.Conclusions: The results suggest that SC patients have thinner corneas compared with control subjects. Additionally, coexistence of DE seems to have an additional impact in the thinning of cornea in SC patients.

Precision of pachymetric measurements with Scheimpflug –Placido disc cornealTopography and comparison of these measurements with ultrasonic pachymetry

Back ground: Several devices with different physical bases have been developed for the clinical measurement of corneal thickness, they classified into 4 categories: Scheimpflug photography based, Slit –Scanning topography, optical coherence tomography (OCT) based and ultrasound (US) based.Objective:To evaluatethe precision of the new Scheimpflug –Placido disc corneal topography in measurement of corneal thickness and to compare the measured values with that obtained by US pachymetry.Methods: Setting of this study is Lasik center in Eye Specialty Private Hospital. Baghdad. Iraq.Eyes of healthy subjects were examined with the Sirius topography.3 consecutive measurements of central (CCT)and thinnest (TCT) corneal thicknesses were obtainedand the measurements repeated within 1 week. The within –subject standard deviation (Sw),test-retest repeatability ,coefficient of variation (CoV),and interclass correlation coefficient (ICC) were calculated to evaluate intra session repeatability and intersession reproducibility. For US pachymetry (Tomey-SP 100) only CCT was measured. Comparison ofthe measurements that obtained by the 2 devices done by paired t-test.Results: The topography provides high intrasession repeatability with test-retest and CoV close to 6μm and0.4%, respectively for both CCT and TCT. The inter session reproducibility also high with test-retest and CoV close to 8μm and 0.5%, respectively.ICC was higher than 0.97 for repeatability and reproducibility . Anarrow 95% limit of agreement was found between the pachymetry obtained by topography and US pachymetry measurements.Conclusions :The topography has been used showed high intrasession repeatability and intersession reproducibility of CCT and TCT measurements in healthy eyes .Absence of statistically significant differences suggest that the topography -TCT and the US pachymetry - CCT can be used interchangeably in subject with normal cornea.Financial Disclosure: No financial or proprietary interest in any material or method mentioned.

Evaluation of pachymetric measurements with scheimpflug photography-based system and optical coherence tomography pachymetry at different stages of keratoconus.

The aim of this study was to compare the central and peripheral pachymetric measurements determined with Sirius system and Visante OCT and evaluate the agreement between them at different stages of keratoconus. Measurements were not significantly different in all patients and subgroups and showed high correlation for the corneal thicknesses of the entire cornea in different stages of keratoconus.

Evaluation of Corneal Parameters with Scheimpflug Imaging in Patients with Rheumatoid Arthritis

Purpose: To evaluate corneal parameters of rheumatoid arthritis (RA) patients by Pentacam-HR.Methods: Seventy RA patients and 100 control subjects were enrolled. All participants underwent Pentacam (Pentacam-HR, Oculus, Germany) evaluation. Both RA and control groups were divided into two subgroups as dry eye (DE) (Schirmer test with topical anesthesia (STA) ≤ 5 mm) and without DE (STA > 5 mm).Results: Pachymetric measurements and the mean corneal volume were significantly lower in RA group (p < 0.001). Disease duration was negatively correlated with pachymetric measurements in RA group. Pachymetric measurements and corneal volume of RA patients with DE were significantly lower than all the other subgroups. Control subgroups with or without DE were similar in pachymetric measurements and corneal volume.Conclusions: The results suggest that RA patients have thinner corneas compared to control subjects that may be affected by disease duration. Furthermore, coexistence of DE and RA seems to aggravate the thinning of cornea as well.

Intraoperative corneal thickness measurements during corneal collagen cross-linking with isotonic riboflavin solution without dextran in corneal ectasia

Objective: To monitor the changes in corneal thickness during the corneal collagen cross-linking procedure by using isotonic riboflavin solution without dextran in ectatic corneal diseases.Materials and Methods: The corneal thickness measurements were obtained before epithelial removal, after epithelial removal, following the instillation of isotonic riboflavin solution without dextran for 30 min, and after 10 min of ultraviolet A irradiation.Results: Eleven eyes of eleven patients with progressive keratoconus (n = 10) and iatrogenic corneal ectasia (n = 1) were included in this study. The mean thinnest pachymetric measurements were 391.82 ± 30.34 µm (320–434 µm) after de-epithelialization of the cornea, 435 ± 21.17 µm (402–472 µm) following 30 min instillation of isotonic riboflavin solution without dextran and 431.73 ± 20.64 µm (387–461 µm) following 10 min of ultraviolet A irradiation to the cornea.Conclusion: Performing corneal cross-linking procedure with isotonic riboflavin solution without dextran might not induce corneal thinning but a little swelling throughout the procedure.

Central Corneal Thickness in a Korean Population: The Namil Study

We investigated the distribution of central corneal thickness (CCT), and its association with age, sex, intraocular pressure (IOP), anterior chamber depth (ACD), axial length (AL), and the presence of systemic hypertension and diabetes in a Korean population. Our study is a population-based glaucoma prevalence study of residents aged ≥40 years in Namil-meon area, located in central South Korea. All subjects underwent a complete ophthalmic examination that included CCT measurement with an ultrasonic pachymeter, ACD and AL measurements by optical biometry, and Goldmann applanation tonometry. The right eye of all subjects was analyzed. The mean (SD) CCT of the 1259 right eyes was 530.9 (31.5) μm. In univariate analysis, a thicker CCT was associated with a higher IOP (P < 0.001), a longer AL (P = 0.003), and a younger age (P < 0.001). ACD was not correlated significantly with CCT (P = 0.087). Men had a 5.7 μm higher CCT than women (age adjusted, P = 0.001). Subjects with hypertension had a 4.1 μm lower CCT than those without hypertension (age, sex-adjusted, P = 0.027), and the presence of diabetes was not associated significantly with CCT (age, sex-adjusted, P = 0.892). In multivariate analysis, a higher CCT was associated with a higher IOP (P < 0.001), younger age (P = 0.001), male sex (P = 0.005), and the absence of hypertension (P = 0.018). The mean CCT of a Korean population was 530.9 μm. CCT was associated with IOP, age, sex, and hypertension.

Descemet Membrane Endothelial Transfer: “Free-Floating” Donor Descemet Implantation as a Potential Alternative to “Keratoplasty”

To describe corneal clearance after reendothelialization of the recipient posterior stroma, by a "free-floating" donor Descemet roll in the recipient anterior chamber after Descemet membrane endothelial keratoplasty (DMEK), as a potential new approach in managing corneal endothelial disorders. An 80-year-old woman underwent DMEK for Fuchs endothelial dystrophy. Within hours after the surgery, a "free-floating" Descemet roll was observed in the recipient anterior chamber. Because the operated eye had low visual potential, the patient requested to await the clinical outcome, which was monitored by biomicroscopy, and endothelial cell density (ECD) and pachymetric measurements were evaluated. Within the first few weeks after DMEK, the transplanted cornea showed diffuse corneal edema with a central pachymetry of more than 1000 μm. From 1 month onward, the transplanted cornea started to clear in the inferior quadrants. At 6 months, only remnant edema was present in the superior far periphery, pachymetry across the cornea had returned to normal, and ECD measured 830 cells per square millimeter. The performance of a descemetorhexis followed by the implantation of a "free-floating" Descemet roll in the recipient anterior chamber, tentatively named Descemet membrane endothelial transfer, may have potential as a "no-keratoplasty" surgical concept in the management of corneal endothelial disorders.

Correlation between epithelial thickness in normal corneas, untreated ectatic corneas, and ectatic corneas previously treated with CXL; is overall epithelial thickness a very early ectasia prognostic factor?

To determine and correlate epithelial corneal thickness (pachymetric) measurements taken with a digital arc scanning very high frequency ultrasound biomicroscopy (HF UBM) imaging system (Artemis-II), and compare mean and central epithelial thickness among normal eyes, untreated keratoconic eyes, and keratoconic eyes previously treated with collagen crosslinking (CXL). Epithelial pachymetry measurements (topographic mapping) were conducted on 100 subjects via HF UBM. Three groups of patients were included: patients with normal eyes (controls), patients with untreated keratoconic eyes, and patients with keratoconic eyes treated with CXL. Central, mean, and peripheral corneal epithelial thickness was examined for each group, and a statistical study was conducted. Mean, central, and peripheral corneal epithelial thickness was compared between the three groups of patients. Epithelium thickness varied substantially in the keratoconic group, and in some cases there was a difference of up to 20 μm between various points of the same eye, and often a thinner epithelium coincided with a thinner cornea. However, on average, data from the keratoconic group suggested an overall thickening of the epithelium, particularly over the pupil center of the order of +3 μm, while the mean epithelium thickness was on average +1.1 μm, compared to the control population (P = 0.005). This overall thickening was more pronounced in younger patients in the keratoconic group. Keratoconic eyes previously treated with CXL showed, on average, virtually the same average epithelium thickness (mean -0.7 μm, -0.2 μm over the pupil center, -0.9 μm over the peripheral zone) as the control group. This finding further reinforces our novel theory of the "reactive" component of epithelial thickening in corneas that are biomechanically unstable, becoming stable when biomechanical rigidity is accomplished despite persistence of cornea topographic irregularity. A highly irregular epithelium may be suggestive of an ectatic cornea. Our results indicate that the epithelium is thinner over the keratoconic protrusion, but to a much lesser extent than anticipated, and on average epithelium is thicker in this group of patients. This difference appears to be clinically significant and may become a screening tool for eyes suspected for ectasia.

Corneal thickness measurements with the Concerto on-board pachymeter

Purpose To assess the Concerto excimer laser on-board pachymeter (COP) measurements of the central corneal thickness (CCT), central stromal thickness (CST) and flap thickness (FT) in terms of repeatability and agreement with the Pentacam and ultrasound pachymetery. Methods Patients undergoing photorefractive keratectomy (PRK), PRK with mitomycin-C (MMC), and laser in situ keratomileusis (LASIK) were enrolled in the study. All eyes had CCT measurement with the Pentacam, the COP, and ultrasound, preoperatively. In the LASIK group, the CST was measured intraoperatively with the COP and ultrasound, after removing the flap. Each measurement was done 3 times to study the repeatability, and we calculated the 95% limits of agreement (LoA) for paired readings. Results The study sample comprised of 82 eyes of 41 patients. All three devices showed excellent repeatability with intraclass correlation coefficients between 0.946 and 0.993. Mean CCT was 546 ± 31 μm with the COP, and 548 ± 32 μm and 548 ± 34 μm with the ultrasound and Pentacam, respectively. COP readings demonstrated high correlations with their paired ultrasound and Pentacam readings. The 95% LoA between COP and ultrasound were −16.6 μm to 12.0 μm for CCT, −25.6 μm to 26.2 μm for CST, and −29.5 to 21.3 μm for FT. The 95% LoA between COP and Pentacam CCT readings were −15.1 μm to 10.1 μm. Conclusions COP generated repeatable readings that were highly correlated with their pair readings by the Pentacam and ultrasound. Although the agreement between COP and ultrasound was better with CCT measurements, the inter-device agreement for CST readings was not worse than that reported in other comparative studies of pachymeters.

Comparison of corneal thickness measurement with the Pentacam, the PARK1 and an ultrasonic pachymeter

Purpose: The aim was to determine the agreement between PARK1 pachymetric readings and measurements made with the Pentacam and ultrasonic pachymetry.Methods: In this prospective study, we enrolled refractive surgery patients free of other ocular conditions and performed Pentacam and PARK1 acquisitions followed by ultrasonic pachymetry. We recorded pachymetric readings on the centre, apex and thinnest point with the Pentacam, corneal thickness values of the apex and minimum readings from the PARK1, and the central corneal thickness with the ultrasonic system. Data were compared using t‐tests, and the Pearson correlations and 95% limits of agreement (LoA) of all pairs were determined.Results: The mean age of the 47 participants was 32 ± 10.4-years and data from their right eyes were used. Overall, ultrasonic measurements were significantly higher than all readings from the PARK1 and the Pentacam. The smallest difference was between the PARK‐apex and Pentacam‐apex readings (0.2 ± 11 µm); the 95% LoA of this pair gave a width of 43.7 µm (‐21.7 to 22.0 µm). The smallest width pertained to the Pentacam‐centre and ultrasound‐centre paired readings; the width was 32.5 µm (‐21.8 to 11.8 µm), while the mean difference was ‐5.54 ± 8 µm.Conclusion: The PARK1 measurements of the apical corneal thickness can be a substitute for central corneal pachymetry with an ultrasonic device, provided that the range of agreement is taken into consideration in the interpretation of the results. Similar studies on populations with different corneal conditions such as keratoconus are needed.

Novel Pachymetric Parameters Based on Corneal Tomography for Diagnosing Keratoconus

To describe pachymetric progression indices (PPI) of the Pentacam HR (Oculus Optikgeräte GmbH) and the concept of relational thickness, and to test their accuracy for differentiating keratoconic and normal corneas compared with single-point thickness values. One hundred thirteen individual eyes randomly selected from 113 normal patients and 44 eyes of 44 patients with keratoconus were studied using the Pentacam HR by acquiring central corneal thickness (CCT), thinnest point (TP), position of the TP and PPI at minimal (PPI Min) and maximal (PPI Max) meridians, and the average (PPI Ave) of all meridians. Relational thickness parameters were calculated as the ratios of TP and CCT and PPI values. Mann-Whitney U test assessed differences in groups for each variable. Receiver operating characteristic (ROC) curves were calculated for all variables and pairwise comparisons were performed. Statistically significant differences were noted between normal and keratoconic eyes for all parameters (P<.001), except for horizontal position of TP (P=.79). The best parameters, named Ambrósio's Relational Thickness (ART), were ART-Ave (TP/PPI Ave) and ART-Max (TP/PPI Max) with areas under the ROC curves of 0.987 and 0.983, respectively. The best cutoffs were 424 μm and 339 μm for ART-Ave and ART-Max, respectively. Pachymetric progression indices and ART had a greater area under the curve than TP and CCT (P<.001); TP (0.955) had a greater area under the curve than CCT (0.909; P=.002). Tomographic-derived pachymetric parameters were better able to differentiate normal and keratoconic corneas than single-point pachymetric measurements. Further studies are needed to evaluate the role of tomography in identifying early forms of ectasia as well as ectasia risk among LASIK candidates.

Pachymetric measurements with a new Scheimpflug photography–based system: Intraobserver repeatability and agreement with optical coherence tomography pachymetry

To evaluate the intraobserver repeatability of pachymetric measurements obtained with a new Scheimpflug photography-based system and the agreement of the measurements with those obtained by optical coherence tomography (OCT). Vissum Corporation, Alicante, Spain. Evaluation of diagnostic technology. Corneal thickness was measured at different locations (center; 2.5 mm and 4.0 mm nasal, temporal, superior, and inferior) in 18 eyes of 18 patients with no ocular pathology or previous surgery with a Scheimpflug photography-based system (Sirius). Three consecutive measurements at each location were obtained with the system to evaluate intraobserver repeatability. Afterward, pachymetric measurements were obtained at the same locations with an OCT system (Visante) to evaluate the agreement between techniques using the Bland-Altman method. The intraclass correlation coefficient of repeated measures ranged from 0.990 to 0.997. The coefficient of variation was lower than 1% and the standard deviations of the repeated measurements (S(w)) were below 6 μm at all corneal locations. Statistically significant differences were found between the coefficient of variation and S(w) values of the repeated measurements corresponding to the 2.5 mm and 4.0 mm locations (P ≤ .037). The agreement with OCT pachymetric measurements was poor, with ranges of agreement larger than 20 μm at all corneal locations. Statistically significant differences were found between standard deviations of the differences between the 2 devices at the 2.5 mm and 4.0 mm locations (P ≤ .017). Scheimpflug photography-based technology provided repeatable pachymetric measurements that were not equivalent to those obtained with OCT.

Intraoperative Pachymetric Measurements during Corneal Collagen Cross-Linking with Riboflavin and Ultraviolet A Irradiation

To study central corneal pachymetric variations during corneal collagen cross-linking (CXL) treatment with the use of riboflavin and ultraviolet A irradiation (UVA). Prospective, noncomparative, interventional clinical study. Fifteen keratoconic patients (19 eyes) were enrolled. All patients underwent riboflavin-UVA-induced corneal CXL. Intraoperative central corneal thickness (CCT) measurements using ultrasound pachymetry were performed during the procedure. Measurements were obtained after epithelial removal, after riboflavin drop instillation, and every 5 minutes (6 interval times) during UVA irradiation (30 minutes). Central corneal thickness measurements. Mean patient age was 26.9+/-6.5 years (range, 17-40 years). Ten were male and 5 were female. Mean preoperative CCT was 458.5+/-21.5 microm (range, 427-494 microm; 95% confidence interval [CI], 448-467 microm) and 415.7+/-20.6 microm (range, 400-468 microm; 95% CI, 406-426 microm) before and after epithelial removal, respectively. There was a statistically significant decrease (mean, 75 microm) of CCT between the epithelial removal interval (415.7+/-20.6 microm; range, 400-468 microm) and at the end of riboflavin solution instillation (340.7+/-22.9 microm; range, 292-386 microm; P<0.001). There was no statistically significant change in CCT during irradiation (P>0.05). There was no statistically significant difference between preoperative and 1-month postoperative endothelial cell count (preoperative, 2780+/-197 to 1-month postoperative, 2713+/-116; P = 0.14). No intraoperative, early postoperative, or late postoperative complications were observed in this patient series. During corneal CXL with the use of riboflavin and UVA irradiation, a statistically significant decrease of CCT was demonstrated.

Corneal thickness values in case of patients who underwent lamellar keratoplasty using various evaluation techniques.

Abstract Purpose To analyze results of pachymetric measurements in patients after deep anterior lamellar keratoplasty (DALK) and endothelial keratoplasty (DSEK) using three techniques of pachymetry estimation. Methods For the study 35 eyes after various lamellar keratoplasty were qualified. 20 eyes they who underwent DSEK (12 women and 8 men) and 15 after DALK (9 men and 6 women). The subjects age ranged from 23 to 92 years old (mean 45.0.1 years). The follow‐up ranged from 9 to 31 months (mean 16.8 months). Patients underwent routine DSEK and DALK, using “big bubble” technique, surgery. Pachymetric values were achieved using three devices: ultrasonic pachymeter, specular microscope, Anterior Segment OCT. Pachymetric outcomes were analyzed and compared. Results Total corneal thickness in case of patients who underwent DSEK surgery using ultrasound pachymeter ranged from 581 to 829µm (672.4 ± 89.1), specular microscope registered values from 518 to 719µm (575.4 ± 78.3), OCT Visante ranged from 575 to 911µm (690± 122.1). Total corneal thickness in patients who underwent DALK surgery using ultrasound pachymeter ranged from 382 to 571µm (487 ± 76.8), specular microscope registered values from 380 to 481µm (427 ± 84.2), OCT Visante ranged from 379 to 569µm (439± 143.1). Corneal thickness values received with the use of ultrasound and OCT values significantly differed form obtained using specular microscope. Conclusion Specular microscope seems to omit graft thickness in corneal pachymetry evaluation, also pachymetric outcomes are underrated, even though is able to calculate endothelial cell density in patients who underwent lamellar keratoplasty.

Alterations in ocular surface and corneal thickness in relation to metabolic control in patients with chronic renal failure

Ocular surface changes and ocular symptoms may be encountered in patients with chronic renal failure (CRF) undergoing haemodialysis. The ocular surface changes and its relationship with metabolic control in CRF patients were aimed to be emphasized in this study. Thirty-eight CRF patients (75 eyes) undergoing haemodialysis were enrolled. Patients underwent a complete ocular examination together with Schirmer, tear break-up time tests, pachymetric measurements and conjunctival impression cytologies. Blood calcium, phosphate levels and total body volume changes after haemodialysis were recorded. The most common findings were conjunctival calcification with red eye (81.3%) and dry eye (62.7%, according to tear break-up time test) in 75 eyes of 38 patients. Impression cytologies were graded as 0 in 57.3% of eyes and 2-3 in 40% of eyes showing positive correlation with the extent of conjunctival calcification (R = 0.486, P = 0.0001). Serum calcium and phosphate levels were also positively correlated with the degree of conjunctival calcification (R = 0.684, P = 0.0001 and R = 0.428, P = 0.0001, respectively) as well as with the grades of impression cytology (R = 0.587, P = 0.0001 and R = 0.385, P = 0.0001, respectively). Furthermore, the mean corneal thickness decreased significantly (9.31 +/- 26.9 mum) following haemodialysis (Paired t-test, P = 0.002). Dry eye and irritational symptoms are major ocular symptoms in CRF patients. Serum calcium and phosphate levels seem to have a prognostic importance for the ocular findings and symptoms in patients with CRF.

Ultrasound and Partial Coherence Interferometry With Measurement of Central Corneal Thickness

To compare noncontact pachymeter measurements with ultrasound pachymeter measurements and assess their reproducibility. Central corneal thickness was measured in 104 eyes of 56 patients with three laser interference pachymeters (OLCR [Haag Streit, Könitz, Switzerland], OCP [4optics AG, Lübeck, Germany], and ACMaster [Carl Zeiss Meditec, Jena, Germany]) and an ultrasound pachymeter (Tomey AL2000 [Tomey Corp, Nagoya, Japan]). Compared to the ultrasound measurements, the mean difference for the laser interference pachymeter measurements were +8.8 microm (standard deviation [SD] 5.68) for the OLCR, -8.0 microm (SD 5.39) for the OCP, and -0.12 microm (SD 5.88) for the ACMaster. Reproducibility could only be estimated as not all of the devices allowed access to individual measurements. For all laser interference devices, reproducibility was estimated to be approximately 2 microm. Ultrasound measurements yielded a reproducibility of approximately 3.4 microm. Although ultrasound pachymeter measurements differed significantly from OLCR and OCP measurements, agreement was considered good because the mean differences were <10 microm, and the results can be regarded as clinically interchangeable.