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Thomas Kohnen

Publications and source records attributed to Thomas Kohnen.

64 records · Page 4Linked to original sources
PubMed2002

Confocal microscopic characteristics of stage 1 to 4 diffuse lamellar keratitis after laser in situ keratomileusis.

PURPOSE: To evaluate 4 stages of diffuse lamellar keratitis (DLK) after laser in situ keratomileusis using confocal microscopy. SETTING: Department of Ophthalmology, Johann Wolfgang Goethe-University, Frankfurt am Main, Germany. METHODS: This retrospective study comprised 17 eyes (15 patients): 11 cases of stage 1 DLK, 5 cases of stage 2, 1 case of stage 3, and 2 cases of stage 4. All eyes were examined by slitlamp biomicroscopy and confocal microscopy. RESULTS: In all cases of stage 1 and 2 DLK, confocal microscopy showed infiltration of inflammatory cells into the flap stroma and the interface. The density of the infiltrates and the number of cells varied within the stage 1 corneas; all stage 2 corneas had dense infiltrates. In the eye with stage 3 DLK, an aggregation of presumed cell remnants was noticed. In the stage 4 cases, there was no active inflammation but stromal folds and numerous activated keratocytes were detected. CONCLUSIONS: Confocal microscopy showed differences in the appearances of the DLK groups. There were similarities in the features of stages 1 and 2. Only stages 1 and 2 represented active inflammation, whereas stages 3 and 4 showed the result of accumulation and decay of the inflammatory cells.

Adult↗
PubMed2002

[Laser epithelial keratomileusis (LASEK): histological investigation for vitality of corneal epithelial cells after alcohol exposure].

BACKGROUND: Laser epithelial keratomileusis (LASEK) is a new surgical procedure to treat myopia. An epithelial flap is created after the exposure to 20 % alcohol and following the laser ablation the epithelium is repositioned to its original location. The advantage of LASEK is that the ablated corneal surface is covered by a full thickness epithelium immediately after surgery. It is hypothesised that this epithelial coverage inhibits the wound healing response of the cornea. However, this concept will only work if the epithelial cells are still vital after the exposure to alcohol. MATERIAL AND METHODS: The vitality of the corneal epithelial cells was investigated in 6 human cadaver eyes after the exposure to 20 % alcohol over 15 to 60 s. The vitality of the corneal epithelial cells was assessed by soaking the specimen in a 0.1 % trypan blue solution and incubated at 37 degrees C for 2 min. After a wash with BSS the specimen were re-incubated at 37 degrees C for 30 min in culture medium. After one more wash with BSS the cells were observed with a standard light microscope. Cells which retained the blue colour would be dead and vital cells would appear clear. Light microscopy and transmission electron microscopy was used to detect morphological changes. RESULTS: Mainly vital corneal epithelial cells were seen for an alcohol exposure time of up to 30 s. In particular the basal epithelial cells appeared alive. With a exposition time of 60 s most cells were dead. CONCLUSION: In LASEK the exposure time of 20 % alcohol is between 20 and 30 s. Based on our results we can conclude that after such exposure time most cells are alive, which is essential for the postoperative wound healing response.

Cell Count↗
PubMed2002

[Highly refractive silicone lens with sharp optic edge (CeeOn Edge, Model 911): one year results of a multicenter clinical trial on performance and efficacy].

PURPOSE: To investigate the performance and efficacy of a new high refractive index (1.46) silicone intraocular lens with sharp optic edges. MATERIALS AND METHODS: In this open prospective multicenter study 149 patients underwent cataract surgery and implantation of CeeOn Edge in one eye. Best corrected visual acuity was determined at day 1 - 2, week 1 - 2, month 6 and month 12 postoperatively. Posterior capsule was clinically evaluated according to existence or absence of posterior capsule opacification (PCO). PCO was defined as relevant if the visual acuity loss exceeded at least two lines. The intraoperative handling of the lens was assessed concerning foldability, haptic handling, positioning, unfolding and general assessment. RESULTS: Visual acuity increased from preoperatively 0.3 to 0.9 after one year. PCO with impact on visual acuity (loss of 2 lines or more) was recorded in only two patients, after 2 weeks (YAG) resp. 1 year (no YAG). The handling and implantation was considered to be good to very good. No lens-related complications were seen during the one year study period. CONCLUSIONS: CeeOn Edge, Model 911, restores visual acuity after cataract surgery and shows promising handling results. The low rate of PCO and YAG is most probably related to the sharp edge of the lens.

Aged↗
PubMedDate not supplied

Comparison of endothelial cell count using confocal and contact specular microscopy.

Precise examination of the corneal endothelium has become increasingly important due to the growing number of intraocular and corneal procedures. The purpose of this study was to compare prospectively the corneal endothelial cell count in normal eyes obtained by confocal and specular microscopy. Central corneal endothelial cell densities of 42 eyes from 42 patients were measured by confocal and contact specular microscopy. Endothelial cells were analyzed with the same software in a manual, an automated and a semi-automated mode. The mean endothelial cell density obtained by confocal microscopy was (in the manual, automated and semi-automated modes) 3,069 +/- 285, 2,791 +/- 344 and 3,077 +/- 286 cells/mm(2), and obtained by specular microscopy 3,076 +/- 298, 2,796 +/- 271 and 3,082 +/- 282 cells/m(2), respectively. No statistically significant difference of endothelial cell density between confocal and specular microscopy was found. Endothelial cell count was significantly lower in the automated than in the semi-automated and manual analysis both with confocal and with specular microscopy. In conclusion, endothelial cell count measurements with confocal and contact specular microscopy are comparable.

Adolescent↗