Hypothyroidism is Not Associated with Keratoconus Disease: Analysis of 626 Subjects.

PURPOSE: To analyze the association between hypothyroidism and keratoconus, we examined blood thyroid hormone levels and corneal tomographic parameters in healthy subjects and patients with keratoconus. METHODS: We included 626 subjects (304 left eyes, 49%; 431 males, 69%; age 38.4 ± 14.3 y). Patients with keratoconus were from our Homburg Keratoconus Center (HKC) (n = 463); patients with hypothyroidism were from the Department of Internal Medicine of Saarland Medical University, Homburg/Saar, Germany (n = 75); and healthy subjects were from the Department of Ophthalmology of Saarland University Medical Center (n = 88). We included only one randomly selected eye of each subject and the first examination data. EXCLUSION CRITERIA: Previous thyroid medication, previous ocular surgery, and patients with suspected keratoconus (topographic keratoconus classification, [TKC]: 0 < 1). Patient eyes were classified (TKC) with dedicated, instrument-based, keratoconus detection software provided with the Pentacam. TKC = 0 was considered "normal," and TKCs ≥ 1 were considered keratoconus. Subjects were also classified as euthyroid or hypothyroid, based on blood thyroid hormone status (i.e., TSH, FT3, and FT4). A multiple logistic linear regression model was constructed to determine the effects of age (covariate), gender, and hypothyroidism (effect sizes) on "TKC-positive" disease. RESULTS: The significance levels for a constant parameter, sex, thyroid condition, and age were p < 0.0001, p < 0.0001, p < 0.0001, and p=0.003, respectively. The odds ratios for age, sex, and hypothyroidism were 0.98, 3.05, and 3.34, respectively. Male sex and a euthyroid condition had significantly positive, clinically relevant effects, and age had a significantly negative, but clinically irrelevant effect on the estimated TKC index. CONCLUSIONS: Keratoconus appeared to occur more often in patients classified as euthyroid than in patients with hypothyroidism. Thus, hypothyroidism alone could not support the development of keratoconus. Based on these results, it should not be mandatory to screen patients with hypothyroidism for keratoconus or patients with keratoconus for hypothyroidism.

Scanning-slit topography in patients with keratoconus.

AIM: To evaluate the anterior and posterior corneal surfaces using scanning-slit topography and to determine the diagnostic ability of the measured corneal parameters in keratoconus. METHODS: Orbscan II measurements were taken in 39 keratoconic corneas previously diagnosed by corneal topography and in 39 healthy eyes. The central minimum, maximum, and astigmatic simulated keratometry (K) and anterior axial power values were determined. Spherical and cylindrical mean power diopters were obtained at the central and at the steepest point of the cornea both on anterior and on posterior mean power maps. Pachymetry evaluations were taken at the center and paracentrally in the 3 mm zone from the center at a location of every 45 degrees. Receiver operating characteristic (ROC) analysis was used to determine the best cut-off values and to evaluate the utility of the measured parameters in identifying patients with keratoconus. RESULTS: The minimum, maximum and astigmatic simulated K readings were 44.80±3.06 D, 47.17±3.67 D and 2.42±1.84 D respectively in keratoconus patients and these values differed significantly (P<0.0001 for all comparisons) from healthy subjects. For all pachymetry measurements and for anterior and posterior mean power values significant differences were found between the two groups. Moreover, anterior central cylindrical power had the best discrimination ability (area under the ROC curve=0.948). CONCLUSION: The results suggest that scanning-slit topography and pachymetry are accurate methods both for keratoconus screening and for confirmation of the diagnosis.

Corneal biomechanical data and biometric parameters measured with Scheimpflug-based devices on normal corneas.

AIM: To analyze the correlations between ocular biomechanical and biometric data of the eye, measured by Scheimpflug-based devices on healthy subjects. METHODS: Three consecutive measurements were carried out using the corneal visualization Scheimpflug technology (CorVis ST) device on healthy eyes and the 10 device-specific parameters were recorded. Pentacam HR-derived parameters (corneal curvature radii on the anterior and posterior surfaces; apical pachymetry; corneal volume; corneal aberration data; depth, volume and angle of the anterior chamber) and axial length (AL) from IOLMaster were correlated with the 10 specific CorVis ST parameters. RESULTS: Measurements were conducted in 43 eyes of 43 volunteers (age 61.24±15.72y). The 10 specific CorVis ST data showed significant relationships with corneal curvature radii both on the anterior and posterior surface, pachymetric data, root mean square (RMS) data of lower-order aberrations, and posterior RMS of higher-order aberrations and spherical aberration of the posterior cornea. Anterior chamber depth showed a significant relationship, but there were no significant correlations between corneal volume, anterior chamber volume, mean chamber angle or AL and the 10 specific CorVis ST parameters. CONCLUSIONS: CorVis ST-generated parameters are influenced by corneal curvature radii, some corneal RMS data, but corneal volume, anterior chamber volume, chamber angle and AL have no correlation with the biomechanical parameters. The parameters measured by CorVis ST seem to refer mostly to corneal properties of the eye.

Arginase activity, urea, and hydroxyproline concentration are reduced in keratoconus keratocytes.

PURPOSE: Keratoconus (KC) is a disease characterized by thinning and deformation of the cornea, but its etiology remains unknown. Seventy percent of the corneal stroma consists of collagen, which is composed of three intertwined polypeptide chains with glycine-hydroxyproline-proline repeats along their sequence. Arginase is a cytoplasmatic enzyme and catalyzes the conversion of arginine to urea and ornithine, which serves as a precursor for the endogenous synthesis of proline and hydroxyproline. The purpose of this study was to analyze arginase activity, as well as collagen and urea formation in normal and KC-keratocytes and to determine the impact of urea on keratocyte viability and proliferation in vitro. METHODS: Primary human keratocytes were isolated by digestion in collagenase (1.0 mg/mL) from surgically removed corneas of eight keratoconus patients and eight normal human corneal buttons and cultured in DMEM/Ham's F12 medium supplemented with 5 % fetal calf serum. Arginase activity and urea concentration were measured in cell-lysates, hydroxyproline concentration in supernatant of cultured keratocytes using colorimetric assay. Cell viability and cell proliferation of cultured keratocytes were assessed after treatment with urea at concentrations up to10 mM for 24 h using assays for metabolic activity and DNA replication. RESULTS: Arginase activity and urea concentration in KC-keratocytes decreased by about 50 % compared to normal keratocytes (p = 0.003 and p = 0.008). Hydroxyproline synthesized by cultured KC-keratocytes was also approximately 50 % less compared to normal keratocytes (p = 0.02) and this difference decreased following treatment with 5.0 or 10.0 mM urea (p = 0.02; 0.03), without any change in cell viability (p > 0.09). However, the urea treatment increased modestly (by 20 %) the proliferation rate of KC-keratocytes (p = 0.04; 0.04; 0.04), without any effect on normal cultured keratocytes (p > 0.09). CONCLUSIONS: We identified suppressed arginase activity in the metabolic program of cultured keratoconus keratocytes. The level of urea, as one product of the enzyme arginase was also decreased. This results in impaired collagen synthesis, evidenced in the culture by reduced hydroxyproline concentration. In addition, our data showed that the other product of the arginase reaction, urea supports the proliferation of KC-keratocytes, without changes in their viability. The metabolic reprogramming of keratoconus keratocytes and its impact on development of a clinically detectable keratoconus disease has to be further analyzed.

Corneal endothelial morphology and function after torsional and longitudinal ultrasound mode phacoemulsification.

PURPOSE: To study the endothelial cell morphology and corneal thickness changes after phacoemulsification by using the OZil torsional and longitudinal ultrasound techniques (Infiniti Vision System, Alcon Laboratories). SETTING: Department of Ophthalmology, Clinical Center, University of Debrecen, Debrecen, Hungary. METHODS: 52 patients with cataract were randomly assigned to longitudinal ultrasound and torsional mode group. All surgeries were performed through a 2.2 mm clear corneal incision, the method employed being divide and conquer. The endothelial morphometry such as cell density (ECD), mean cell area, coefficient of variation of cell area, and central corneal thickness were examined with specular microscopy (EM-1000, Tomey) preoperatively and 4, 8 weeks postoperatively. RESULTS: ECD values decreased significantly in both surgical groups (P < .001, repeated- mesures ANOVA), the postoperative endothelial cell loss was higher in the longitudinal ultrasound mode group (3.5% and 6.5%, at 4 and 8 weeks after surgery) than in the torsional group (3.3% and 5.5%, at 4 and 8 weeks after surgery), the difference not being significant between the two groups (P = .164 and P = .479, at 4 and 8 weeks after surgery, Mann-Whitney test). There was no statistically significant difference in any of the assessed parameters between the two surgical groups (P > .05). No significant correlation was found between the endothelial cell loss and the nucleus density. CONCLUSIONS: Both phacoemulsification techniques were safe and effective. The torsional handpiece performs oscillatory movements and delivers less energy into the eye than the longitudinal ultrasound technique, therefore providing more favorable energy and thermal safety profile.