RESUMEN
BACKGROUND/AIMS: Certain degenerative eye conditions occur predominantly nasally, at the limbal region, and are associated with solar ultraviolet radiation (UVR) induced damage. The relative contribution to the in vivo ocular flux of (a) the reflection of UVR incident on the skin of the nose onto the nasal limbus, and (b) the focusing of UVR incident on the temporal side of the cornea onto the nasal limbus were examined. METHODS: A novel photodiode sensor array was used to measure the UVR field across the eye. In addition, a novel spectrometer set-up was used to measure the spectrum of radiation refracted across the cornea. The efficacy of UVR blocking hydrogel contact lenses in filtering incident UVR was assessed in vivo. RESULTS: Qualitative and quantitative data indicated an increase nasally of UVR. Photodiode readings showed a net UVR increase from the temporal to the nasal side. Transmission curves showed that most UVR incident on the limbal region is either absorbed by, or transmitted through, the ocular tissues. This radiation is filtered by UVR blocking soft contact lens. CONCLUSIONS: An increased UVR flux on the nasal side of the eye, due to reflection off the nasal skin, was identified in vivo. Any UVR passing through the cornea is either absorbed by the conjunctiva and/or transmitted through it onto the sclera where it is absorbed. UVR blocking hydrogel contact lenses can eliminate these sources of UVR.
Asunto(s)
Lentes de Contacto Hidrofílicos , Ojo/efectos de la radiación , Rayos Ultravioleta , Diseño de Equipo , Oftalmopatías/prevención & control , Tecnología de Fibra Óptica/métodos , Humanos , Hidrogel de Polietilenoglicol-Dimetacrilato , Dosis de Radiación , Traumatismos por Radiación/prevención & control , Radiometría/instrumentación , Radiometría/métodos , Dispersión de Radiación , Análisis Espectral/métodosRESUMEN
PURPOSE: The goal of this study was to develop a short-term, practical, yet effective regimen for the perioperative use of recombinant human erythropoietin (r-HuEPO) as an alternative to autologous blood donation and/or homologous transfusion. In addition, changes in iron kinetics during accelerated erythropoiesis were examined. PATIENTS AND METHODS: A randomized trial was performed on 24 healthy, iron-replete men. Subjects were given r-HuEPO in one of three dosage schedules, receiving a total dose of 1200 U/kg r-HuEPO subcutaneously: Group I--300 U/kg on Days 1, 4, 7, and 10; Group II--400 U/kg on Days 1, 5, and 9; Group III--600 U/kg on Days 1 and 10. All subjects received 300 mg of elemental iron orally each day for 10 days beginning on Day 1. Complete blood counts (CBC), absolute reticulocyte counts, serum ferritin, serum iron, serum total iron-binding capacity (TIBC), and serum transferrin receptor protein concentrations were measured periodically during the 24-day study period. RESULTS: All groups showed a statistically significant increase in hematocrit, hemoglobin, and absolute reticulocyte count. There was no significant difference in response among the three groups with respect to hemoglobin and hematocrit. The mean maximum increases in hematocrit were 5.4 +/- 1.7, 6.0 +/- 2.1, and 7.2 +/- 2.6 in groups I, II, and III, respectively. The increase in hematocrit positively correlated with log baseline ferritin (r = 0.682, p < 0.001). Administration of r-HuEPO was associated with a highly significant (p < or = 0.0005) 74% decrease in serum ferritin, as well as a marked decrease in percent saturation of TIBC from 39% +/- 14% to 14% +/- 4% (p < or = 0.0005). This was despite the fact that subjects lost less than 250 mL of blood as a result of venipunctures during the entire course of the study. CONCLUSION: Each of these r-HuEPO dose schedules provides an effective, convenient regimen for perisurgical use. However, "normal" iron stores for basal erythropoiesis may not always be sufficient to supply optimal amounts of iron for the accelerated erythropoiesis associated with acute r-HuEPO administration, even with oral iron supplementation. Nonetheless, these findings provide support for further study of the use of r-HuEPO as an alternative to autologous blood donation in the perisurgical setting.