[Immune reaction after penetrating keratoplasty depending on graft size and centration]. / Immunreaktion nach perforierender Keratoplastik in Abhängigkeit von der Transplantatgröße und -zentrierung.

BACKGROUND: Immune reaction (IR) after penetrating keratoplasty (PKP) is a serious complication with a high risk of graft failure. The aim of this study was to analyze and evaluate the risk factors for IR, in particular, the influence of graft size and centration. PATIENTS AND METHODS: A total of 2133 patients who underwent PKP between January 2009 and July 2019 were included in this retrospective study. The following endpoints were analyzed: frequency of IR, graft origin, donor and patient age, diagnosis, corneal diameter and ratio of the graft size to the recipient cornea size. In addition, the role of graft centration, with the help of distance measurements of the graft margins to the vascularized limbus at four locations, was investigated in detail. RESULTS: Overall, 8.25% of patients suffered from IR during the observational period. The frequency of IR was significantly correlated (p < 0.001) with the ratio of the graft size to the recipient cornea size. In addition, a statistically significant correlation was found between the occurrence of IR and a small distance to the limbal margins in the Y­axis (inferior and superior). In particular, the correlation coefficient was larger at the inferior limbus (p < 0.001). CONCLUSION: An IR after PKP is a not uncommon complication and is significantly related to graft size and centration. A large graft chosen in relation to the recipient cornea and the proximity of the graft to the vascularized limbus at the inferior and superior sites significantly correlate with the occurrence of IR. These are important risk factors for graft survival, which can be influenced by the corneal microsurgeon and could possibly be further optimized in the future.

[Interobserver and intraobserver reliability of corneal surface temperature measurements with the TG-1000 thermograph in normal eyes]. / Inter- und Intraobserverreliabilität der kornealen Oberflächentemperaturmessung mit dem TG-1000 bei Normalaugen.

PURPOSE: The aim of this study was to analyze the reliability of temperature measurements with the ocular TG-1000 thermograph in a setup of sequential measurements performed by one observer (intraobserver) and a sequence of measurements performed by different observers (interobserver) in normal subjects without pathologies of the anterior segment of the eye. PATIENTS AND METHODS: A total of 50 right eyes from 50 individuals (mean age 29.1 ± 7.9 years) without ocular pathologies or history of ocular surgery were enrolled in this prospective monocentric clinical case series. Eyes with signs of dry eye syndrome (based on a positive McMonnies questionnaire) were excluded from the study. Corneal surface temperature measurements were performed by three examiners to assess interobserver reliability. In addition, in a subgroup of 22 individuals, a sequence of 3 measurements were performed by 1 of the examiners to examine intraobserver reliability. Corneal surface temperature was measured within an interval of 10 s (11 frames) on a region of interest of 16 ± 12 mm (320 ± 240 pixels). Central and mid-peripheral local temperatures at 3 mm (3, 6, 9 and 12 o'clock) were extracted and analyzed from the raw data. RESULTS: The ocular TG-1000 thermograph yielded consistent results for the interobserver as well as intraobserver conditions in measuring corneal surface temperature in the center as well as mid-periphery of the cornea. Cronbach's alpha was 0.9 or higher at all corneal locations, which proves a high consistency of results for the interobserver and intraobserver measurements. The average corneal surface temperature ranged between 34.0 °C and 34.7 °C with a slight decrease from the upper temporal (9 and 12 o'clock) to the lower nasal (3 and 6 o'clock) quadrants. CONCLUSION: The TG-1000 thermograph yielded consistent results of corneal surface temperature in individuals without anterior segment pathologies or history of ocular surgery. With the option of raw data export (11 frames within 10 s with a lateral resolution of 320 × 240 pixels) the thermograph offers a wide range of new diagnostic options for a spatiotemporal analysis of corneal surface temperature.

[A comparison of device-based diagnostic methods for keratoconus]. / Gerätegestützte Diagnostikverfahren des Keratokonus im Vergleich.

PURPOSE: Due to the modern device-assisted diagnosis of keratoconus by topography, tomography and biomechanical properties of the cornea, a large number of parameters and indices are obtained as a result of clinical examinations. The aim of the present study was to investigate how modern screening methods support the diagnosis of keratoconus. PATIENTS AND METHODS: In this prospective study, 93 eyes of 93 keratoconus patients and 107 eyes of 107 healthy subjects (control group) were included. The keratoconus group contained 85 % males, whereas the distribution in the control group was balanced. The mean age was 35 ± 12 years in the keratoconus group and 27 ± 7 years in the control group. Exclusion criteria for both groups were previous eye surgery, cross-linking therapy, glaucoma, uveitis or other inflammatory diseases of the eye. All patients with a thyroid disorder were also excluded from the control group. All eyes were examined using the TMS-5 topographer, Pentacam and Ocular Response Analyzer (ORA). Based on receiver operator characteristics (ROC), the performance of various keratoconus indices was determined by means of the area under the curve (AUC). RESULTS: All parameters showed statistically highly significant differences between the keratoconus and control group (p ≤ 0.0001). The Surface Asymmetry Index (SAI) and the Keratoconus Severity Index (KSI) of TMS performed well with (mean value keratoconus group/mean value control group/AUC) SAI (2.43/0.36/0.969) and KSI (50.87/0.37/0.912). Pentacam parameters Index of Surface Variance (ISV) and Topographic Keratoconus Classification (TKC) were comparable to TMS parameters with ISV (90.05/15.77/0.969), TKC (2.23/0.00/0.940). ORA indices Corneal Hysteresis (CH), Corneal Resistance Factor (CRF) and Keratoconus Match Index (KMI) showed slightly poorer performance with CH (8.22/11.48/0.909), CRF (7.25/11.20/0.951), KMI (0.31/1.05/0.909). CONCLUSION: In this study, tomography and topography was more reliable in diagnosing keratoconus than evaluating the biomechanical properties of the cornea. SAI and KSI (TMS) as well as TKC and ISV (Pentacam) showed improved recognition rates compared to the KMI (ORA). However, individual parameters alone are not sufficient for the diagnosis of keratoconus.