Photosensitivity of murine skin greatly depends on the genetic background: clinically relevant dose as a new measure to replace minimal erythema dose in mouse studies.

Artificial UV irradiation of murine skin is a frequently used method for testing photosensitivity, study carcinogenesis and photoprotective effects of different compounds. However, doses of UV radiation and mouse strains used in experiments vary greatly. The genetic background of mice may influence the photosensitivity as melanin content, pigmentation and hair cycle parameters are dissimilar. Doses of UV are often expressed in relation to the minimal erythema dose (MED) that was not necessarily determined for the given strain. We set out to standardize the method of measuring photosensitivity in three commonly used mouse strains, C57BL/6N, Balb/c and SKH-1. We found that MED may not be determined for some strains as erythema development in mice with diverse genotypes differs greatly. We measured the oedema response in vivo and ex vivo by using OCT. Given the strain-specific variability of erythema, we introduced Clinically Relevant Dose (CRD) as a new term to replace MED in experiments, to describe the lowest dose that triggers a perceptible skin reaction in mice. Not only the CRD but the proportion of erythema and oedema were different in strains examined. C57BL/6N mice display skin reactions at the lowest UVB dose, while SKH-1 hairless mice show changes, mostly oedema, after higher doses of UVB. The cellular composition and skin thickness were examined by histopathology. IL-1beta and IL-6 levels in skin correlated with the increasing doses of UVB. Despite the variations in the degree of erythema and oedema, no major differences in cytokine expressions were seen among various strains of mice.

The effect of incorrect scanning distance on boundary detection errors and macular thickness measurements by spectral domain optical coherence tomography: a cross sectional study.

BACKGROUND: To investigate the influence of scan distance on retinal boundary detection errors (RBDEs) and retinal thickness measurements by spectral domain optical coherence tomography (SD-OCT). METHODS: 10 eyes of healthy subjects, 10 eyes with diabetic macular edema (DME) and 10 eyes with neovascular age-related macular degeneration (AMD) were examined with RTVue SD-OCT. The MM5 protocol was used in two consecutive sessions to scan the macula. For the first session, the device was set 3.5 cm from the eye in order to obtain detectable signal with low fundus image quality (suboptimal setting) while in the second session a distance of 2.5 cm was set with a good quality fundus image. The signal strength (SSI) value was recorded. The score for retinal boundary detection errors (RBDE) was calculated for ten scans of each examination. RBDE scores were recorded for the whole scan and also for the peripheral 1.0 mm region. RBDE scores, regional retinal thickness values and SSI values between the two sessions were compared. The correlation between SSI and the number of RBDEs was also examined. RESULTS: The SSI was significantly lower with suboptimal settings compared to optimal settings (63.9±12.0 vs. 68.3±12.2, respectively, p = 0.001) and the number of RBDEs was significantly higher with suboptimal settings in the "all-eyes" group along with the group of healthy subjects and eyes with DME (9.1±6.5 vs. 6.8±6.3, p = 0.007; 4.4±2.6 vs. 2.5±1.6, p = 0.035 and 9.7±3.3 vs. 5.1±3.7, p = 0.008, respectively). For these groups, significant negative correlation was found between the SSI and the number of RBDEs. In the AMD group, the number of RBDEs was markedly higher compared to the other groups and there was no difference in RBDEs between optimal and suboptimal settings with the errors being independent of the SSI. There were significantly less peripheral RBDEs with optimal settings in the "all-eyes" group and the DME subgroup (2.7±2.6 vs. 4.2±2.8, p = 0.001 and 1.4±1.7 vs. 4.1±2.2, p = 0.007, respectively). Retinal thickness in the two settings was significantly different only in the outer-superior region in DME. CONCLUSIONS: Optimal distance settings improve SD-OCT SSI with a decrease in RBDEs while retinal thickness measurements are independent of scanning distance.

Macular morphology assessed by optical coherence tomography image segmentation after femtosecond laser-assisted and standard cataract surgery.

PURPOSE: To evaluate and compare thickness changes in the retinal layers in the macula with optical coherence tomography (OCT) segmentation software after femtosecond laser-assisted phacoemulsification (study group) and conventional phacoemulsification (control group). SETTING: Department of Ophthalmology, Semmelweis University, Budapest, Hungary. DESIGN: Case-control study. METHODS: Total retinal thickness of the macula was evaluated using Stratus OCT 4 to 8 weeks postoperatively. The OCT images were segmented using OCT retinal image analysis software. Regional thickness data in the central area, inner rings, and outer rings were obtained and absolute and relative thicknesses of the individual retinal layers in the 2 study groups compared. Relative thickness was calculated as the ratio of the retinal layer to the total retinal thickness. RESULTS: All surgeries were uneventful. Statistically significant differences were found in absolute outer nuclear layer thickness and relative outer nuclear layer thickness in the inner and outer macular rings between the 2 groups. After adjusting for effective phaco time in multivariate modeling, type of surgery showed a significantly lower relative outer nuclear layer ratio in the inner retinal ring (0.26 with 95% confidence interval [CI], 0.25-0.27 versus 0.28 with 95% CI, 0.27-0.29; P=.03) and in the outer retinal ring (0.27 with 95% CI, 0.25-0.28 versus 0.29 with 95% CI, 0.28-0.31; P=.02) in the study group. CONCLUSION: After cataract surgery, macular edema was detectable mainly in the outer nuclear layer in both groups but was significantly less using the femtosecond laser platform.

Retinal layer thickness changes in eyes with preserved visual acuity and diffuse diabetic macular edema on optical coherence tomography.

BACKGROUND AND OBJECTIVE: Diabetic macular edema has several patterns on optical coherence tomography. This retrospective study aimed to assess which retinal layers show thickness changes in type 1 diffuse diabetic macular edema with preserved vision. PATIENTS AND METHODS: Eleven eyes with diffuse diabetic macular edema on optical coherence tomography and eight control eyes with 20/20 best-corrected visual acuity were enrolled. Optical coherence tomography images were segmented using an algorithm of the authors' design (OCTRIMA): regional thickness data in the central area, pericentral rings, and peripheral rings were obtained for the retinal cellular layers. RESULTS: The retinal nerve fiber layer showed no changes, the ganglion cell and inner plexiform composite layer and the ganglion cell complex were thicker only in the pericentral regions, and all other layers were thicker in all regions in diffuse diabetic macular edema. Macular thickness was normal in the peripheral region. CONCLUSION: The results show that the outer retina in the foveal area is the most affected in diffuse diabetic macular edema.