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Purpose: To report the corneal thinning during and after corneal cross-linking (CXL). Design: Prospective, nonrandomized, single-center observational study. Methods: Thirty patients (30 eyes; 9 female, 21 male; age, 38 ± 12 years) were consecutively scheduled for CXL between January 23 and July 6, 2009. Twenty-four eyes had progressive keratoconus, 2 had pellucid marginal degeneration, 3 eyes had progressive keratectasia after a LASIK operation, and 1 eye had pseudophakic bullous keratopathy. Riboflavin-ultraviolet A (UVA)-induced CXL included the instillation of 0.1% riboflavin drops for 30 minutes followed by riboflavin instillation combined with UVA irradiation for another 30 minutes. Corneal thickness was measured preoperatively, during CXL, and after 1 and 6 months using an ultrasound pachymeter. Changes in the endothelial cell count, corneal steepness, refraction, and visual performance are also given. Results: On average, the corneas thinned 87 ± 40 μm (range, 37-206 μm; 19% ± 7%) during a 60-minute CXL treatment. In 1 patient, the cornea did not swell, even with hypotonic solution such that CXL would be safe. After 1 month, the corneal thickness was lower than the preoperative thickness, but after 6 months, the corneas had regained their original thicknesses. The endothelial cell count and corneal steepness were unchanged after CXL. The UCVA (uncorrected visual acuity) and BSCVA (best spectacle-corrected visual acuity) were improved 6 months after CXL. Conclusions: Corneal thickness decreases significantly during CXL, even to a level where the health of the endothelium and cornea is jeopardized. Visual performance is improved 6 months after CXL. [ABSTRACT FROM AUTHOR]

Abstract: Lysobisphosphatidic acid (LBPA) can be regarded to represent a unique derivative of phosphatidylglycerol. This lipid is highly enriched in late endosomes where it can comprise up to 10–15mol% of all lipids and in these membranes, LBPA appears to be segregated into microdomains. We studied the thermotropic behavior of pure dioleoyl-LBPA mono- and bilayers using Langmuir-lipid monolayers, electron microscopy, differential scanning calorimetry (DSC), and fluorescence spectroscopy. LBPA formed metastable, liquid-expanded monolayers at an air/buffer interface, and its compression isotherms lacked any indication for structural phase transitions. Neat LBPA formed multilamellar vesicles with no structural transitions or phase transitions between 10 and 80°C at a pH range of 3.0–7.4. We then proceeded to study mixed LBPA/dipalmitoylphosphatidylcholine (DPPC) bilayers by DSC and fluorescence spectroscopy. Incorporating increasing amounts of LBPA (up to XLBPA (molar fraction)=0.10) decreased the co-operativity of the main transition for DPPC, and a decrease in the main phase transition as well as pretransition temperature of DPPC was observed yet with no effect on the enthalpy of this transition. In keeping with the DSC data for DPPC, 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC)/LBPA mixed bilayers were more fluid, and no evidence for lateral phase segregation was observed. These results were confirmed using fluorescence microscopy of Langmuir-lipid films composed of POPC and LBPA up to XLBPA=0.50 with no evidence for lateral phase separation. As late endosomes are eminently acidic, we examined the effect of lowering pH on lateral organization of mixed PC/LBPA bilayers by DSC and fluorescence spectroscopy. Even at pH 3.0, we find no evidence of LBPA-induced microdomain formation at LBPA contents found in cellular organelles. [Copyright &y& Elsevier]

Objective: To evaluate visual performance after unilateral photorefractive keratectomy (PRK) performed for ≥2.75-diopter (D) myopic anisometropia.Design: Prospective observational case series.Participants: Eleven patients exhibiting ≥2.75-D myopic anisometropia appropriate for PRK.Methods: Photorefractive keratectomy was performed on 11 eyes of 11 patients for myopic anisometropia ranging from –2.75 to –9.00 D. Best spectacle-corrected visual acuity (VA), contrast sensitivity (CS), and pattern visual evoked potentials (pVEPs) were measured preoperatively and at 3 and 6 months.Main outcome measures: Best spectacle-corrected VA; pVEPs; and CS, measured as the area under the CS curve.Results: Best spectacle-corrected VA increased nonsignificantly 6 months after PRK. A tendency towards decreased latency time of pVEPs for both eyes was observed after PRK. A significant increase in CS occurred after PRK in the operated eye at 6 months, but a tendency toward decreased CS appeared in the unoperated eye at 3 months. Preoperative CS levels, however, were reached at 6 months.Conclusions: The adult central visual system is sensitive to visual deprivation caused by anisometropia. Imbalance between eyes may improve visual performance in the more emmetropic eye. Anisometropia appears to reduce visual performance in the more myopic eye, but this can probably be reversed by refractive correction. [Copyright &y& Elsevier]

Atherosclerosis is characterized by the accumulation in the arterial intima of mainly low-density lipoprotein (LDL)-derived lipids, together with apolipoprotein B-100 (apoB-100), the protein moiety of LDL. Recent studies indicate aggregation of LDL within the arterial wall to represent a critical step in the initiation of this disease. Aggregation of LDL has been further proposed to involve ceramide, the levels of which are elevated in atherosclerotic plaques as well as in LDL isolated from these lesions. Biophysical studies have shown ceramide to have a pronounced tendency for self-aggregation, presumably driven by intermolecular hydrogen bonding. Importantly, the segregated ceramide-enriched lipid phases have high melting temperatures and are in a gel state at 37°C. The plasma levels of sphingomyelin, which upon enzymatic hydrolysis by sphingomyelinase (SMase) yields ceramide, have been shown to correlate with the severity of coronary heart disease. The formation of ceramide from sphingomyelin could thus represent a critical step in atherosclerosis. We recently showed that LDL itself possesses SMase activity. Moreover, sequence analogy with bacterial enzymes suggests that this activity may be intrinsic to apoB-100. Possible physiological role of this activity is uncertain, yet could be involved in nonreceptor-mediated endocytotic entry of LDL into cells. Importantly, it also opens a possible mechanistic link between elevated plasma levels of LDL, apoptosis (programmed cell death), and atherosclerosis. [Copyright &y& Elsevier]

Highlights: [•] We simulate interactions of pyrene-linked lipids in a lipid membrane. [•] We study the effects of where pyrenes are attached to the chains of their host lipids. [•] Pyrene-induced perturbations are largely similar in all cases in a DOPC environment. [•] Transition to membrane-spanning pyrene dimers is very abrupt. [ABSTRACT FROM AUTHOR]

Purpose To analyze the outcome of penetrating keratoplasty (PK) to the first eye for corneal amyloidosis in familial amyloidosis, Finnish type (FAF). Design Single-center, retrospective, nonrandomized, interventional, noncomparative case series. Participants Thirty-one eyes of 31 patients with FAF. Intervention All patients with FAF who had their first PK in Helsinki University Eye Hospital between January 1, 1990, and August 1, 2011, were identified and a retrospective analysis of the patient charts was performed. Main Outcome Measures Best spectacle-corrected visual acuity (BCVA), intraoperative and postoperative complications, graft survival, reason for graft failure, and frequency of regrafting. Results The median follow-up period was 32 months (range, 5–114). After 24 months, the median BCVA was 1.15 on a logarithm of the minimum angle of resolution scale (20/280; mean, 1.1; SD, 0.5) in comparison with the preoperative median BCVA of 1.3 (20/400; mean, 1.3; SD, 0.4). At 24 months, 3 of 18 eyes (17%) had a visual acuity of ≥0.5 (20/63) and 13 of 18 grafts (72%) were clear. Rejection occurred in 6 of 31 primary grafts (19%). Graft failure occurred in 16 of 31 eyes and resulted from surface complications in 11 eyes and additionally from rejection in 5 eyes. Seven eyes needed regrafting (twice in 1 eye). Complications were frequent in the early and late postoperative periods. Presence of preoperative corneal or graft neovascularization was an indicator of a high risk of graft failure and poor visual outcome. Conclusions In a minority of FAF patients, PK improves vision. Owing to the high failure risk and guarded visual prognosis after PK, it is important that both the surgeon and the patient have realistic expectations. It may be reasonable to limit PK to cases with bilateral advanced disease. It seems reasonable to optimize ocular surface health and to delay PK. [ABSTRACT FROM AUTHOR]

Abstract: The purpose of this review is to provide insight into the biophysical properties and functions of tear fluid and lung surfactant – two similar fluids covering the epithelium of two distinctive organs. Both fluids form a layer-like structure that essentially comprise of an aqueous layer next to the epithelium and an anterior lipid layer at the air-water interface. The aqueous layers contain soluble proteins and metabolites, and they are responsible for the host defence system and nutrition of the organ. However, many proteins also interact with the lipid layer and are important for the surface-active function of the fluid film. The lipid layer of lung surfactant comprises mainly of phospholipids, especially phosphatidylcholines, and only small amounts of non-polar lipids, mainly cholesterol. In contrast, tear fluid lipid layer comprises of a mixture of polar and non-polar lipids. However, the relative proportion and the spectrum of different polar and non-polar lipids seem to be more extensive in tear fluid than in lung surfactant. The differing lipid compositions generate distinctive lipid layer structures. Despite the structural differences, these lipid layers decrease the surface tension of the air-water interface. The structure of the tear film lipid layer also minimises the evaporation of the tear fluid. In lung surfactant surface activity is crucial for the function of the organ, as the lipid layer prevents the collapse of the lung alveoli during the compression-expansion cycle of breathing. Similarly the tear film experiences a compression-expansion cycle during blinking. The dynamics of this cycle have been studied to a lesser extent and are not as clear as those of lung surfactant. The common structure and properties suggest a similar behaviour under rapid compression–expansion for both fluids. [Copyright &y& Elsevier]

Abstract: The function of mammalian ocular lens is to provide a sharp image to the retina. Accordingly, the lens needs to be transparent and minimize light scattering. To do so the lens fiber cells first loose intracellular organelles, organize the cytoplasm and arrange the fiber cell membranes. Because the fiber cells are metabolically inactive, the plasma membrane becomes the only cellular organelle and consequently, the phase behavior of these membranes determines the physiological state of the lens. Previous studies have shown that lipids extracted from the nuclear and cortical region of human lens show a temperature-induced phase transition close to the body temperature. Yet, the physiological function of this phase transition is not known, and even the presence of the phase transition in intact lenses is unknown. Positron annihilation lifetime spectroscopy (PALS) was used to characterize the sub-nanometer-sized local structure of intact porcine lens and these studies were complemented with differential scanning calorimeter and mass spectrometric analysis in extracted porcine lens lipids. Using PALS, we present evidence for the presence of a temperature-dependent structural transition centered at 35.5°C in-situ in clear extracted porcine lenses. Further studies employing extracted lens lipids and purified egg-yolk sphingomyelin and cholesterol mixtures suggest that the nano-scale transition emerges from the phase behavior of lens lipids. Based on our results, PALS seems to be a viable method for gaining additional information on biological tissues, especially since it enables non-destructive studies on intact tissues. [Copyright &y& Elsevier]

Abstract: Fusidic acid (FA), a narrow spectrum steroidal antibiotic, is useful for treatment of most skin, conjunctival, and corneal infections and also in infections caused by atypical microbes in the surface of the eye. Liposome electrokinetic capillary chromatography (LEKC) was used to study the interactions between FA and lipid membranes. Liposomes prepared by extrusion were composed of 1-palmitoyl-2-oleyl-sn-glycero-3-phosphocholine (POPC) and 1-palmitoyl-2-oleyl-sn-glysero-3-phosphor-l-serine (POPS), cholesterol, FA, and sphingomyelin (SM) in various molar ratios. 26 different liposome dispersions were studied as dispersed (pseudostationary) phase in LEKC. The hydrophobicities of the liposomes were evaluated by calculating the retention factors of model neutral steroids. The retention factors were calculated using the EOF and the effective electrophoretic mobilities of the analytes and the liposomes. The latter were separately determined by capillary electrophoresis with a polyacrylamide (PAA)-coated capillary. FA–lipid membrane interactions were studied by determining the retention factor of FA. In addition, liposomes prepared from lipids extracted from Escherichia coli bacterium were studied and used as dispersed phase in LEKC for interaction studies between FA and lipid membranes. [Copyright &y& Elsevier]