Corneal Hydration Control in Fuchs' Endothelial Corneal Dystrophy

Abstract

PurposeTo assess corneal hydration control across a range of severity of Fuchs' endothelial corneal dystrophy (FECD) by measuring the percent recovery per hour (PRPH) of central corneal thickness after swelling the cornea and to determine its association with corneal morphologic parameters.MethodsTwenty-three corneas of 23 phakic FECD patients and 8 corneas of 8 healthy control participants devoid of guttae were graded (modified Krachmer scale). Effective endothelial cell density (ECDe) was determined from the area of guttae and local cell density in confocal microscopy images. Steady-state corneal thickness (CTss) and standardized central corneal backscatter were derived from Scheimpflug images. Corneal swelling was induced by wearing a low-oxygen transmissible contact lens for 2 hours in the morning. De-swelling was measured over 5 hours after lens removal or until corneal thickness returned to CTss. Percent recovery per hour was 100 × (1 – e−k), where k was determined from CT(t) = (de−kt) + CTss, and where d was the initial change from CTss.ResultsAfter contact lens wear, corneas swelled by 9% (95% CI 9–10). Percent recovery per hour was 49%/h (95% CI 41–57) in controls and 37%/h in advanced FECD (95% CI 29–43, P = 0.028). Low PRPH was associated with disease severity, low ECDe, and increased anterior and posterior corneal backscatter. Anterior backscatter was associated with PRPH in a multivariable model (R2 = 0.44).ConclusionsCorneal hydration control is impaired in advanced FECD and is inversely related to anterior corneal backscatter. Anterior corneal backscatter might serve as an indicator of impaired endothelium in FECD.

Predicting the Prognosis of Fuchs Endothelial Corneal Dystrophy by Using Scheimpflug Tomography

“…Corneal backscatter increases in FECD 9,10 because of the presence of corneal edema and also because of structural changes in response to chronic edema 15 ; it also correlates with, but is poorly predictive of, corneal endothelial function. 16 In these previous studies, we standardized corneal backscatter measurements to eliminate any confounding effect introduced by variations in the light source and camera of the instrument. Standardizing backscatter measurements requires imaging a fixed scatter source (standard) before every examination followed by adjustment of corneal measurements relative to the image intensity of the standard (which should remain the same over time).…”

Scanning Acoustic Microscopy Comparison of Descemet's Membrane Normal Tissue and Tissue With Fuchs' Endothelial Dystrophy

“…48 FECD is also known to develop edema that is clinically detectable only at the most advanced grade. 46 The decreased elasticity in Descemet membrane with FECD observed in the present study, can likely be attributed to the structural changes induced by FECD in to the Descemet membrane that are known to result in a decreased stiffness in terms of Young's modulus of elasticity. 12…”

“…The biomechanical properties of cornea have been reported as being altered in cases of FECD, where a significant decrease in corneal hysteresis (CH) and corneal resistance factor (CRF) than in normal eyes with a significant elevation in the intraocular pressure (IOP cc ) than in normal cases have been quantified. 45 Corneal dehydration, which is normally performed by the endothelia of the normal corneas by functioning as both a barrier to fluid movement into the cornea and as an active pump that moves ions 46 and draws water osmotically from the stroma into the aqueous humor, is known to be altered in FECD. The reduced corneal endothelium cell density in FECD results in a decrease of the dehydration capacity 46,47 which likely contributes to a decreased stiffness (Young's modulus) of Descemet membrane The acoustic micrograph in 2A with frames indicating the regions 1, 2, and 3 for which V(z) curves were generated.…”

“…45 Corneal dehydration, which is normally performed by the endothelia of the normal corneas by functioning as both a barrier to fluid movement into the cornea and as an active pump that moves ions 46 and draws water osmotically from the stroma into the aqueous humor, is known to be altered in FECD. The reduced corneal endothelium cell density in FECD results in a decrease of the dehydration capacity 46,47 which likely contributes to a decreased stiffness (Young's modulus) of Descemet membrane The acoustic micrograph in 2A with frames indicating the regions 1, 2, and 3 for which V(z) curves were generated. (B) Averaged V(z) curves computed from the data taken from a stack of images for the areas marked by the frames in (A).…”

Mixed Model Analysis of Between-Subject Variability in Overnight Corneal Swelling and Deswelling With Silicone Hydrogel Lenses

“…The slower corneal deswelling rate in older individuals might be attributed (among other things) to lower endothelial pump function in older individuals 32 by endothelial morphologic changes 34 with older age. An association between endothelial morphological changes and endothelial pump function (recovery from swelling) was found in both normal 32 and diseased 35,36 corneal endothelium in the past.…”