Purpose To evaluate early changes in visual function and visual quality parameters after Descemet membrane endothelial keratoplasty (DMEK) and to compare the outcomes with healthy controls. Methods Thirteen patients who underwent DMEK and 14 controls were evaluated. All subjects underwent visual function evaluation, including visual acuity under photopic and mesopic lighting conditions and contrast sensitivity (CSV) tests CSV 1000 and Pelli-Robson. Corneal parameters were assessed with Oculus Pentacam. Corneal mean keratometry (Km), corneal densitometry values, and low and high order aberrations (LOA and HOA) were recorded. In DMEK patients, all tests were performed before surgery and 1 and 6 months after surgery. Results In patients who underwent DMEK, photopic visual acuity improved from 0.59 to 0.31 at 1 month (p=0.013) and 0.13 at 6 months (p=0.008); mesopic visual acuity and all contrast sensitivity values (both CSV and Pelli-Robson test) improved significantly in the first month (p < 0.005). A significant decrease was observed in corneal density in the 0–2 mm ring (from 43.83 to 35.60, p=0.043) and mean posterior Km (from −5.84 to −6.80, p=0.005) in the first month. Corneal HOAs and all corneal densities improved at 6 months after DMEK (p < 0.05). All visual function parameters and corneal aberrations remained lower and higher, respectively, compared with healthy controls (p < 0.05). Corneal densities were comparable with controls at 6 months after DMEK (p > 0.05). Conclusions Patients undergoing DMEK present visual function improvement and a decrease in corneal density at 1 month after surgery. Decrease in corneal posterior HOAs can be observed at 6 months. However, visual function outcomes and corneal aberrations remained worse compared with healthy controls.

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Evaluar los efectos y la seguridad del perfluorohexiloctano (F6H8) tópico en la superficie ocular y el endotelio corneal.Métodos: Fueron diagnosticados 45 pacientes (90 ojos) de enfermedad de ojo seco, se seleccionaron y se les prescribió tratamiento con F6H8 durante 6 meses. Las variables en la tinción corneal se documentaron usando la escala National Eye Institute/Industry Workshop (NEI), las variables conjuntivales usando la escala Oxford y los parámetros corneales, como el espesor corneal central, la densidad celular, el coeficiente de variación, la hexagonalidad y el área celular promedio, al inicio del estudio, a los 3 meses y a los 6 meses. Se evaluó también el cumplimiento y la satisfacción.Resultados: El tratamiento con F6H8 redujo la tinción corneal promedio en pacientes cumplidores a una media de −0,84 ± 1,95 a los 3 meses (p = 0,001) y a −1,65 ± 2,42 a los 6 meses (p < 0,001). La tinción conjuntival a los 6 meses mostró una disminución promedio de −0,13 (p = 0,319). Los parámetros endoteliales no mostraron diferencia significativa, excepto el espesor corneal central, que mostró una disminución estadísticamente significativa (era de 545,30 ± 32,25 m al comienzo del estudio y 538,40 ± 31,36 m tras 6 meses, p = 0,009). Al final del estudio, el 46% de los pacientes informaron sentirse subjetivamente mejor, el 40,5% no sintió cambios y el 13,5% se sintió subjetivamente peor.Conclusiones: El tratamiento tópico con F6H8 para la enfermedad de ojo seco no alteró las variables medidas del endotelio corneal, aunque sí mostró mejoría en la tinción corneal y en la satisfacción.

PurposeTo analyze the rheological behaviours of several artificial tears.MethodsIn vitro viscosity profile of the different artificial tears was obtained. A cone‐plate rotational rheometer was used with ascending and descending shear rate (from 1 s‐1 to 1000 s‐1, 330 measurements) at a constant temperature of 30°C and a fluid volume of 5 ml. The difference between viscosities in each section of shear rate was calculated.ResultsFour different rheological patterns were found in 78 artificial tears: shear‐thinning, shear‐thickening, thixotropic and Newtonian. Thixotropy was found between 0.17 and 104.576 mPas. Shear‐thinning, shear‐thickening and Newtonian behaviours showed a variation in viscosity in the last measurement section between −1.22 and 517 mPas.DiscussionThe viscosity of artificial tears always depends on the shear rate. It is possible to find two patterns simultaneously depending on the shear rate. These rheological patterns could serve to optimize the treatment with lubricants in different conditions of the ocular surface.ConclusionsThe variation of the shear rate conditions the viscous behavior of the fluids. We have defined four possible rheological models in the measured artificial tears. In vivo studies are necessary to evaluate the clinical utility of these findings.Bibliography Bhushan B. Introduction To Tribology. 2nd ed. New York: John Wiley & Sons, Inc; 2013. 711 p. Simmons PA, Aragona P, Wang H, Wang T. Physiochemical Properties of Hyaluronic Acid‐based Eye Drops. Montpellier, France; 2016. Lievens C, Berdy G, Douglass D, Montaquila S, Lin H, Simmons P, et al. Evaluation of an enhanced viscosity artificial tear for moderate to severe dry eye disease: A multicenter, double‐masked, randomized 30‐day study. Contact Lens Anterior Eye. 2019;42(4):443–9. Pult H, Tosatti SGP, Spencer ND, Asfour JM, Ebenhoch M, Murphy PJ. Spontaneous Blinking from a Tribological Viewpoint. Ocul Surf. 2015;13(3):236–49.