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Title: Central Corneal Edema with Scleral-Lens Wear

Abstract

Purpose: To assess the safety of scleral-lens designs, we model and clinically assess central corneal edema induced by scleral-lens wear for healthy subjects. Materials and Methods: 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. Results: Transport modeling predicts that for open eyes, increasing PoLTF thickness from 50 to 400 µm increases central corneal swelling by approximately 1–1.5% when oxygen transmissibility ( Dk/L) is greater than 10 hBarrer/cm (i.e., hectoBarrer/cm). Although swelling is larger for oxygen Dk/L < 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 Dk/L is > 40 hBarrer/cm. For closed eye, central corneal swelling is greater than 5% for an oxygen Dk/L range of 0–100 hBarrer/cm with typical lens-fitting parameters. For carbon-dioxide transmissibilities increasing from 50 to 250 hBarrer/cm and with amore » fixed oxygen Dk/L 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. Conclusions: Oxygen/metabolite transport calculations for open-eye scleral-lens wear demonstrate that normal PoLTF thicknesses fitted by clinicians (i.e., PoLTF thicknesses < 400 µm) with modern scleral lenses (i.e., oxygen Dk/L > 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.« less

Authors:
 [1];  [1];  [1];  [1]
  1. Univ. of California, Berkeley, CA (United States)
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1571122
Grant/Contract Number:  
AC02-05CH11231
Resource Type:
Accepted Manuscript
Journal Name:
Current Eye Research
Additional Journal Information:
Journal Volume: 43; Journal Issue: 11; Journal ID: ISSN 0271-3683
Publisher:
Taylor & Francis
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; Scleral lens; corneal edema; hypoxia; corneal metabolism; computational modeling; contact lens; oxygen

Citation Formats

Kim, Young Hyun, Tan, Bo, Lin, Meng C., and Radke, Clayton J. Central Corneal Edema with Scleral-Lens Wear. United States: N. p., 2018. Web. doi:10.1080/02713683.2018.1500610.
Kim, Young Hyun, Tan, Bo, Lin, Meng C., & Radke, Clayton J. Central Corneal Edema with Scleral-Lens Wear. United States. doi:10.1080/02713683.2018.1500610.
Kim, Young Hyun, Tan, Bo, Lin, Meng C., and Radke, Clayton J. Mon . "Central Corneal Edema with Scleral-Lens Wear". United States. doi:10.1080/02713683.2018.1500610. https://www.osti.gov/servlets/purl/1571122.
@article{osti_1571122,
title = {Central Corneal Edema with Scleral-Lens Wear},
author = {Kim, Young Hyun and Tan, Bo and Lin, Meng C. and Radke, Clayton J.},
abstractNote = {Purpose: To assess the safety of scleral-lens designs, we model and clinically assess central corneal edema induced by scleral-lens wear for healthy subjects. Materials and Methods: 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. Results: Transport modeling predicts that for open eyes, increasing PoLTF thickness from 50 to 400 µm increases central corneal swelling by approximately 1–1.5% when oxygen transmissibility (Dk/L) is greater than 10 hBarrer/cm (i.e., hectoBarrer/cm). Although swelling is larger for oxygen Dk/L < 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 Dk/L is > 40 hBarrer/cm. For closed eye, central corneal swelling is greater than 5% for an oxygen Dk/L 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 Dk/L 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. Conclusions: Oxygen/metabolite transport calculations for open-eye scleral-lens wear demonstrate that normal PoLTF thicknesses fitted by clinicians (i.e., PoLTF thicknesses < 400 µm) with modern scleral lenses (i.e., oxygen Dk/L > 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.},
doi = {10.1080/02713683.2018.1500610},
journal = {Current Eye Research},
number = 11,
volume = 43,
place = {United States},
year = {2018},
month = {8}
}

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