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We propose that, for materials having positive dielectric anisotropy, the biaxiality can be clearly verified or excluded by measuring the transmitted light intensity as a function of electric field. If the material is biaxial and is observed in homeotropically aligned cells, the schlieren texture should not disappear (transmitted intensity is not zero) even at very high fields, since the field does not affect the distribution of the second director normal to the main director. On the other hand, if the material is uniaxial the transmitted intensity should decrease with increasing field and a perfect homeotropic texture can be achieved at high fields. We have studied a bent-core compound in which a uniaxial-biaxial nematic (N_{u}-N_{b}) transition has been reported. This material has a positive dielectric anisotropy at low frequencies, so we could apply the technique described above. Our studies indicate that the material is uniaxial in the entire nematic range.

We report the determination of the Kerr constant (B) and the real part of the third-order nonlinear optic susceptibility (chi(3)) above the nematic-isotropic phase transition temperature (TNI) of a liquid crystal composed of bent-shaped molecules. The values of B and chi(3) just above (approximately 0.3 degrees C) TNI are approximately 8x10(-12) m/V2 and 5x10(-20) m2/V2, respectively. The estimated critical temperature TC* is about 1.5 degrees C below TNI indicating that the nematic-isotropic (NI) transition is weakly first order as in the case of calamitic liquid crystals. The temperature-dependent Kerr constant is found to be in good agreement with the predictions of the Landau-de Gennes theory. The experimental results are compared with those in a calamitic liquid crystal material with negative dielectric anisotropy in the nematic phase.

Background: Treatment of corneal abrasions often involves antibiotic ointment and pressure patching. The corneal abrasions following excimer laser photorefractive keratectomy have been managed with disposable soft contact lenses and diclofenac (Voltaren) eye drops., Methods: We report 13 patients with corneal abrasions from trauma or recurrent corneal erosions treated with application of a disposable soft contact lens and instillation of diclofenac and antibiotic eye drops., Results: All 13 patients reported significant pain relief and all abrasions healed within 3 days (most within 24 hours). Two of the recurrent erosion patients suffered subsequent spontaneous abrasions and one of the traumatic abrasion patients developed a possible infectious keratitis which cleared without visual loss., Conclusions: In this small series, the combination of a disposable soft contact lens and the instillation of diclofenac drops provided significant pain relief while the abrasion healed and allowed the patients to function with binocular vision. This treatment regimen offers an alternative to pressure patching in the treatment of corneal abrasions.