Central Corneal Edema with Scleral-Lens Wear [electronic resource]

• Ngôn ngữ: eng
• Ký hiệu phân loại: 621.876 Applied physics
• Thông tin xuất bản: Washington, D.C. : Oak Ridge, Tenn. : United States. Dept. of Energy. Office of Science ; Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2018
• Mô tả vật lý: Size: p. 1305-1315 : , digital, PDF file.
• Bộ sưu tập: Metadata
• ID: 260188
• Chủ đề: 1. 60 applied life sciences; 2. Computational modeling; 3. Contact lens; 4. Corneal edema; 5. Corneal metabolism; 6. Hypoxia; 7. Oxygen; 8. Scleral lens

Tóm tắt

 <
 p>
 <
 strong>
 Purpose:<
 /strong>
  To assess the safety of scleral-lens designs, we model and clinically assess central corneal edema induced by scleral-lens wear for healthy subjects. <
 /p>
 <
 p>
 <
 strong>
 Materials and Methods: <
 /strong>
 Typically, central corneal swelling during scleral-lens wear is measured using optical coherence tomography (OCT). Transport resistances are modeled for oxygen diffusion through the scleral lens and post-lens tear-film (PoLTF), and into the cornea. Oxygen deficiency in the cornea activates anaerobic metabolic reactions that induce corneal edema. Oxygen permeability, carbon-dioxide permeability, settled-lens PoLTF thickness, and scleral-lens thickness are varied in the calculations to mimic different lens fits. <
 /p>
 <
 p>
 <
 strong>
 Results:<
 /strong>
  Transport modeling predicts that for open eyes, increasing PoLTF thickness from 50 to 400��m increases central corneal swelling by approximately 1?1.5% when oxygen transmissibility (<
 em>
 Dk/L<
 /em>
 ) is greater than 10 hBarrer/cm (i.e., hectoBarrer/cm). Although swelling is larger for oxygen <
 em>
 Dk/L<
 /em>
 �<
 �10 hBarrer/cm, PoLTF thickness has minimal impact in this range. For open eye, oxygen transmissibility of the lens plays a significant role in corneal edema, but is negligible when oxygen <
 em>
 Dk/L<
 /em>
  is >
 �40 hBarrer/cm. For closed eye, central corneal swelling is greater than 5% for an oxygen <
 em>
 Dk/L<
 /em>
  range of 0?100 hBarrer/cm with typical lens-fitting parameters. For carbon-dioxide transmissibilities increasing from 50 to 250 hBarrer/cm and with a fixed oxygen <
 em>
 Dk/L<
 /em>
  of 25 hBarrer/cm, calculated swelling diminishes by an additional 0.5%. Comparison of model calculations to clinical-swelling data is within the error range of the clinical measurements. <
 /p>
 <
 p>
 <
 strong>
 Conclusions:<
 /strong>
  Oxygen/metabolite transport calculations for open-eye scleral-lens wear demonstrate that normal PoLTF thicknesses fitted by clinicians (i.e., PoLTF thicknesses <
 �400��m) with modern scleral lenses (i.e., oxygen <
 em>
 Dk/L<
 /em>
 �>
 �25 hBarrer/cm) produce corneal swelling of less than 2% in agreement with experiment. Therefore, scleral lenses prescribed today evoke less than physiological hypoxic swelling (i.e., less than 4%) for healthy corneas during open-eye. Closed-eye wear, however, appears clinically unsafe.<
 /p>