Correlation between type 2 diabetes, dry eye and Meibomian glands dysfunction / Correlación entre diabetes tipo 2, ojo seco y disfunción de las glándulas de Meibomio

PURPOSE: To assess the Meibomian glands, ocular surface and tear function in patients with type 2 diabetes, and study the correlation between these conditions. METHODS: Prospective study of 76 males, 37 with type 2 diabetes with an average of duration between 7 ± 5 years, and 36 males from control group. After completing an ocular surface disease index (OSDI) questionnaire, the non-invasive tear film break-up time (NIBUT) and the tear lipid layer pattern was performed using interferometry system and tear meniscus height/TMH. Ocular surface was studied with lissamine green staining and morphology of the glands with evaluation of Marx's line (lid margin abnormalities); meibomian secretion was expressed and was also assessed the quality. The results were analyzed using the statistical Kruskal-Wallis and Mann-Whitney, and correlations by Spearman Rho. RESULTS: The mean age was 59 ± 8 years; 71% of participants presented MGD (76% diabetics and 67% controls). OSDI were significantly higher (p = 0.01) in the diabetic group. A positive correlation was found between glycemia and symptoms (p = 0.0005) and strong correlation between Hb1Ac and OSDI in MGD. NIBUT was lower in the control group (2.47 ± 1.2s) than for the diabetic group (2.9 ± 1.2s), with a significant inverse correlation (52.22%) with MG inflammation. CONCLUSIONS: MGD in type 2 diabetic patients is more severe compared with nondiabetic patients. Longer duration of diabetes is associated with major symptoms and changes in MG. Diabetic group showed major changes in lids and tear function, accounting for evaporative dry eye and presenting a high degree of correlation with MG inflammation and obstruction

OBJETIVO: Evaluar las glándulas de Meibomio, la superficie ocular y la función de la lágrima en pacientes con diabetes tipo 2, y estudiar la correlación entre estas situaciones. MÉTODOS: Estudio prospectivo de 76 varones, 37 de ellos con diabetes tipo 2, con una media de duración de entre 7 ± 5 años, y 36 mujeres como grupo control. Tras completar el cuestionario del índice de enfermedad de la superficie ocular (OSDI), se obtuvieron el tiempo de ruptura lagrimal no invasivo (NIBUT) y el patrón de la capa lipídica de la lágrima utilizando interferometría y altura del menisco lagrimal/AML. Se estudió la superficie ocular con tinción verde de lisamina y la morfología de las glándulas con evaluación de la línea de Marx (anomalías del margen del párpado); se expresó la secreción de las glándulas de Meibomio, así como su calidad. Los resultados se analizaron utilizando la pruebas estadísticas Kruskal-Wallis y Mann-Witney, y las correlaciones con Rho de Spearman. RESULTADOS: La edad media fue de 59 ± 8 años; el 71% de los participantes presentaron DGM (76% diabéticos y 67% controles). OSDI fue significativamente superior (p = 0,01) en el grupo diabético. Se encontró una correlación positiva entre glucemia y síntomas (p = 0,0005), y una fuerte correlación entre Hb1Ac y OSDI en DGM. NIBUT fue inferior en el grupo control (2,47 ± 1,2 s) que en el grupo diabético (2,9 ± 1,2 s), con una correlación inversa significativa (52,22%) con la irregularidad del borde palbebral y queratinización del OM. CONCLUSIONES: DGM en los pacientes con diabetes tipo 2 es más grave, en comparación con los pacientes no diabéticos. La mayor duración de la diabetes se asocia a síntomas mayores y cambios en la GM. El grupo diabético reflejó cambios mayores en los párpados y la función de la lágrima, lo cual supone ojo seco evaporativo, y un alto grado de correlación con irregularidad del margen palpebral y obstrucción de la GM

Qualitative and quantitative characterization of the in vitro dehydration process of hydrogel contact lenses.

PURPOSE: To investigate the in vitro dehydration process of conventional hydrogel and silicone-hydrogel contact lens materials. METHODS: Eight conventional hydrogel and five silicone-hydrogel contact lenses were dehydrated under controlled environmental conditions on an analytical balance. Data were taken at 1-min intervals and dehydration curves of cumulative dehydration (CD), valid dehydration (VD), and dehydration rate (DR) were obtained. Several quantitative descriptors of the dehydration process were obtained by further processing of the information. RESULTS: Duration of phase I (r(2) = 0.921), CD at end of phase I (r(2) = 0.971), time to achieve a DR of -1%/min (r(2) = 0.946) were strongly correlated with equilibrium water content (EWC) of the materials. For each individual sample, the VD at different time intervals can be accurately determined using a 2nd order regression equation (r(2) > 0.99 for all samples). The first 5 min of the dehydration process show a relatively uniform average CD of about -1.5%/min. After that, there was a trend towards higher average CD for the following 15 min as the EWC of the material increases (r(2) = 0.701). As a consequence, average VD for the first 5 min displayed a negative correlation with EWC (r(2) = 0.835), and a trend towards uniformization among CL materials for the following periods (r(2) = 0.014). Overall, silicone-hydrogel materials display a lower dehydration, but this seems to be primarily due to their lower EWC. CONCLUSIONS: DR curves under the conditions of the present study can be described as a three-phase process. Phase I consists of a relatively uniform DR with a duration that ranges from 10 to almost 60 min and is strongly correlated with the EWC of the polymer as it is the CD during this phase. Overall, HEMA-based hydrogels dehydrate to a greater extent and faster than silicone-hydrogel materials. There are differences in water retention between lenses of similar water content and thickness that should be further investigated.

Equivalences between refractive index and equilibrium water content of conventional and silicone hydrogel soft contact lenses from automated and manual refractometry.

PURPOSE: The purpose of the present study was to develop mathematical relationships that allow obtaining equilibrium water content and refractive index of conventional and silicone hydrogel soft contact lenses from refractive index measures obtained with automated refractometry or equilibrium water content measures derived from manual refractometry, respectively. METHODS: Twelve HEMA-based hydrogels of different hydration and four siloxane-based polymers were assayed. A manual refractometer and a digital refractometer were used. Polynomial models obtained from the sucrose curves of equilibrium water content against refractive index and vice-versa were used either considering the whole range of sucrose concentrations (16-100% equilibrium water content) or a range confined to the equilibrium water content of current soft contact lenses (approximately 20-80% equilibrium water content). RESULTS: Values of equilibrium water content measured with the Atago N-2E and those derived from the refractive index measurement with CLR 12-70 by the applications of sucrose-based models displayed a strong linear correlation (r2 = 0.978). The same correlations were obtained when the models are applied to obtain refractive index values from the Atago N-2E and compared with those (values) given by the CLR 12-70 (r2 = 0.978). No significantly different results are obtained between models derived from the whole range of the sucrose solution or the model limited to the normal range of soft contact lens hydration. CONCLUSIONS: Present results will have implications for future experimental and clinical research regarding normal hydration and dehydration experiments with hydrogel polymers, and particularly in the field of contact lenses.

Correlations between central and peripheral changes in anterior corneal topography after myopic LASIK and their implications in postsurgical contact lens fitting.

PURPOSE: To investigate the changes in central and peripheral anterior corneal curvatures after myopic laser in situ keratomileusis (LASIK) and to correlate them with the manifest refractive change to discuss how such results could affect post-LASIK corneal topography profiles and midterm stability and their implications in postsurgical contact lens fitting. METHODS: Topographic and refractive data from 18 eyes of 11 patients that had undergone myopic LASIK were collected for 6 months after surgery. Short-term and midterm topographic responses were investigated and correlated with spherical equivalent manifest refractive changes. RESULTS: There was a strong correlation between eccentricity changes and manifest refractive change 15 days after surgery (r = 0.753, P < 0.001), with no significant changes thereafter for the following 6 months (r = 0.148, P = 0.114). A strong linear relationship was found between baseline manifest refraction and changes in corneal curvature at the center (r = 0.810, P < 0.001), 4-mm chord (r = 0.895, P < 0.001), and 6-mm chord (r = 0.696, P < 0.001). Statistically significant changes were also found after the first 15 days (P < 0.005) and showed a regression effect that affects the three zones. In this case, a weaker relationship was found between curvature regression and the final refractive change for the central location (r = 0.412, P = 0.004), 4-mm chord area (r = 0.430, P = 0.003), and 6-mm chord area (r = 0.283, P = 0.023). CONCLUSIONS.: After myopic LASIK, the anterior corneal dioptric power is expected to change, on average, approximately 77% of the attempted spherical equivalent correction at the center; 60% at the 4-mm chord region, where the stronger correlation between topographic and refractive change is found; and 30% at the 6-mm chord area. The paracentral area 4 mm from the center seems to be more likely to predict baseline corneal curvature from manifest refractive change. Some degree of regression in the midterm period is expected to occur after myopic LASIK, which shows a significant correlation with the manifest refractive change. Again, this effect is more evident and more accurately predicted at the 4-mm chord area. The results of the current study are of interest for those fitting contact lenses after myopic LASIK.

Refractive index and equilibrium water content of conventional and silicone hydrogel contact lenses.

PURPOSE: The purpose of the present study was to measure equilibrium water content (EWC) and refractive index of conventional and silicone hydrogel soft contact lenses (SCL) using a hand refractometer and an automated refractometer. METHODS: Sixteen SCL were used in this study including 12 conventional SCL not containing siloxane moieties (equilibrium water content (EWC) range: 38.6-74%) and the four silicone hydrogel based contact lenses currently available (WC range: 24-47%). Two experienced observers performed the measurements in a randomised order being masked by a third party during the three sessions at which the measurements were collected. The Atago N-2E hand refractometer and the CLR 12-70 digital refractometer were used. Data were analysed separately for conventional and silicone hydrogel materials. RESULTS: Measured EWC and refractive index correlate better when measured with the instruments used in this study (r(2) = 0.979, p < 0.001) than the nominal parameters (r(2) = 0.666, p < 0.001). The linear relationship that correlates nominal and measured EWC shows higher spread of data when all lenses are analysed together (r(2) = 0.840) than when conventional hydrogel (r(2) = 0.953) and silicone hydrogel contact lenses (r(2) = 0.967) are analysed separately. Regarding refractive index, the relationship between nominal and measured values when all the lenses are considered together (r(2) = 0.794) becomes weaker when conventional hydrogel are considered separately (r(2) = 0.688), while a stronger relationship is observed for silicone hydrogel lenses (r(2) = 0.939). Hence, hand refractometry overestimates the EWC of silicone hydrogels, while automated refractive index measurements are more accurate in silicone hydrogels than in conventional hydrogels. CONCLUSIONS: New relationships are presented that correlate nominal and measured values of EWC and refractive index for the silicone containing hydrogels. The linear relationships derived fit well to the data. Hand refractometry overestimates the EWC of silicone hydrogel materials and this bias is related to the proportion of siloxane moieties in the material. Conversely, refractive index can be obtained more accurately with automated refractometry for silicone hydrogels than for conventional hydrogels. Present results are of interest in planning future clinical studies involving the measurement of EWC of current hydrogels.

Microscopic observations of superficial ultrastructure of unworn siloxane-hydrogel contact lenses by cryo-scanning electron microscopy.

The purpose of this study was to analyze three commercial siloxane-hydrogel contact lens materials, lotrafilcon A, balafilcon A, and galyfilcon A, by cryogenic scanning electron microscopy (cryoSEM). The fully hydrated lenses were frozen in slush liquid nitrogen and qualitatively observed in a cryogenic scanning electron microscope. The superficial ultrastructure of the siloxane-hydrogels was observed at the areas where the lens fractured during sample cryogenic preparation. There are qualitative differences among the three examined materials in the complex polymer network structure existing between the outer layer and the underlying polymer. CryoSEM, although destructive, is a useful tool to investigate the structure of polymers used in contact lenses. This technique allows the observation of the inner structure of polymers in the hydrated state. The ultrastructure, the polymer network underlying the outer surface of siloxane-hydrogels by cryoSEM microscopy, have never been reported before.

Microscopic observation of unworn siloxane-hydrogel soft contact lenses by atomic force microscopy.

In the present study, samples of lotrafilcon A, balafilcon A, and galyfilcon A contact lenses were observed by atomic force microscopy (AFM) in tapping mode at areas ranging from 0.25 to 400 microm2. Mean roughness (Ra), root-mean-square roughness (Rms) and maximum roughness (Rmax) in nanometers were obtained for the three lens materials at different magnifications. The three contact lenses showed significantly different surface topography. However, roughness values were dependent of the surface area to be analyzed. For a 1 microm2 area, statistics revealed a significantly more irregular surface of balafilcon A (Ra = 6.44 nm; Rms = 8.30 nm; Rmax = 96.82 nm) compared with lotrafilcon A (Ra = 2.40 nm; Rms = 3.19 nm; Rmax = 40.89 nm) and galyfilcon A (Ra = 1.40 nm; Rms = 1.79 nm; Rmax = 15.33 nm). Ra and Rms were the most consistent parameters, with Rmax presenting more variability for larger surface areas. The higher roughness of balafilcon A is attributed to the plasma oxidation treatment used to improve wettability. Conversely, galyfilcon A displays a smoother surface. Present observations could have implications in clinical aspects of siloxane-hydrogel contact lens wear such as lens spoliation, resistance to bacterial adhesion, or mechanical interaction with the ocular surface.

Oxygen transmissibility of piggyback systems with conventional soft and silicone hydrogel contact lenses.

PURPOSE: To investigate the apparent oxygen transmissibility of various piggyback systems using conventional and silicone hydrogel soft contact lenses of different water content and permeability, rigid poly(methyl methacrylate), and rigid gas-permeable lenses of medium, high, and ultrahigh oxygen permeability. The aim of the study was to establish which material (rigid or hydrogel) is more representative of the resulting oxygen performance of piggyback systems. METHODS: The apparent oxygen transmissibility of 66 piggyback systems was measured with an electrochemical method. Eighteen of these combinations involved the use of silicone hydrogel contact lenses currently available. One hyperpermeable rigid gas-permeable contact lens (tisilfocon A) was also included in the study. RESULTS: Measured apparent transmissibility correlates with rigid lens permeability (r = 0.403; SE = +/-3.03 barrer/cm; P < 0.001) and hydrogel lens permeability (r = 0.334; SE = +/-3.2 barrer/cm; P < 0.001). As expected, a linear model comprising permeability values from both rigid and soft materials gave a more precise estimation of the piggyback transmissibility (r = 0.736; SE = +/-2.02 barrer/cm; P < 0.001). The highest values of apparent oxygen transmissibility were found for the combination of tisilfocon A rigid material with any of the 3 silicone hydrogel lenses. Tisilfocon A material significantly improved the transmissibility of all piggyback systems even when conventional hydrogels are involved. CONCLUSION: The combination of hypertransmissible rigid gas permeable lenses with silicone hydrogel soft materials should result in normal corneal function under daily wear conditions. When fitting piggyback systems, clinicians must be aware of material selection to optimize oxygen performance. This is of particular importance in already compromised corneas.

pH stability of ophthalmic solutions.

BACKGROUND: In this study, we evaluated the pH value of 17 ophthalmic solutions, and we investigated whether the pH of these solutions changed over time after the bottle was opened. METHODS: Fifteen bottles of each type of solution were chosen at random from different production lots. A 0.05-ml increment was taken from each bottle and was measured daily using a micropH 2002 Crison pH-meter over a period of 30 days. RESULTS: The results revealed differences between the pH values of the solutions; nine solutions presented pH values within ocular comfort range and eight solutions presented pH values between 3.5 and 6.4. Ten solutions presented nonstatistically significant variations over time (p > 0.01) and seven solutions presented isolated but statistically significant variations. CONCLUSIONS: We may assume that the nine solutions with pH values within the ocular comfort range will not produce initial discomfort. The solutions with acid pH values will produce initial discomfort. The solutions with nonstatistically significant pH variations over 30 days in relation to their initial pH values presented great stability.

Porous structure of Purevision versus Focus Night&Day and conventional hydrogel contact lenses.

The surface and bulk structures of hydrogel contact lenses that contain siloxane moieties, Purevisiontrade mark (balafilcon A) and Focus(R)Night&Daytrade mark (lotrafilcon A), were investigated. Standard hydrogel lenses of low (Seequence(R)), medium (Acuvue(R)), and high water content (Precision UV(R)) were used as controls. All the lenses were dehydrated in a series of ethanol solutions of increased concentration, critical-point dried in CO(2), and sputter coated with gold/palladium before they were examined by scanning electron microscopy. Of all lenses examined, only the balafilcon lenses presented, in addition to the polymer network porosity characteristic of all hydrogels, a macroporous structure that was observed on the front and back surfaces, and in their bulk. The average diameter of the macropores appears to be much larger, from one to several orders of magnitude, than the network porosity of standard hydrogel lenses. The macropores might contribute to the gas and water permeability of these lenses, as well as to their mobility on the cornea.