Increased Choroidal Thickness in Keratoconus Patients: Perspectives in the Disease Pathophysiology

Abstract

Purpose To analyze and compare choroidal thickness between keratoconus (KC) patients and age-matched non-KC subjects. Methods A cross-sectional, case-control study. One hundred and thirty-four keratoconic eyes and 78 control eyes, from individuals aged from 12 to 30 years old, were studied. Patients with KC followed in Corneal Department of Centro Hospitalar São João, Porto, Portugal, were identified and consecutively included between December 2017 and February 2018. A spectral-domain optical coherence tomography (OCT) using depth enhanced imaging was performed, and choroidal thickness in the center of the fovea and at 500 μm intervals along a horizontal section was measured and compared. Results The statistical analysis showed that keratoconic eyes present a thicker choroid in every measured location (p < 0.05). Mean subfoveal choroidal thickness (SFCT) values obtained were 375.86 ± 89.29 and 322.91 ± 85.14 in keratoconus and control groups, respectively (p < 0.001). In a multivariate analysis, SFCT was significantly associated with spherical equivalent (p=0.004) and the presence of keratoconus (p < 0.001), but not with age (p=0.167), gender (p=0.579), or best-corrected visual acuity (p=0.178). In a “fixed model,” keratoconus patients were found to have a 67.55 μm (95% CI 36.61–98.49) thicker subfoveal choroid compared to controls. Conclusion Keratoconus patients seem to have a thicker choroid than healthy individuals. The exact pathophysiological mechanism resulting in a thicker choroid in KC patients is not known, but it could possibly be associated with inflammatory choroidal mechanisms.

Increased choroidal thickness is not a disease progression marker in keratoconus

“…The median age was 24.00 years (range [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] and individuals in our sample were predominately men (76.3%). Median best corrected visual acuity (BCVA) was 0.90 Snellen (range 0.10-1.00), with glasses or contact lenses.…”

“…Until now all evaluations of KC progression were centered in tomographic and biomechanical corneal parameters 21,22,[28][29][30][31] , but the recently raised questions of an inflammatory hit in the disease and an increased CT in those patients opens new research possibilities. Using a Spectralis OCT our group have previously described a thicker macular choroid in KC eyes compared to healthy age-matched control, with KC patients showing a 67.55 µm thicker subfoveal choroid (CI 95% 36.61-98.49) 23 . The more recent theories about the pathophysiology of KC hint to a possible inflammatory component, which might explain the increase in their CT profile compared to a healthy population 6,7,23,24 .…”

“…Using a Spectralis OCT our group have previously described a thicker macular choroid in KC eyes compared to healthy age-matched control, with KC patients showing a 67.55 µm thicker subfoveal choroid (CI 95% 36.61-98.49) 23 . The more recent theories about the pathophysiology of KC hint to a possible inflammatory component, which might explain the increase in their CT profile compared to a healthy population 6,7,23,24 . In fact, a large number of studies provided evidence of increased levels of pro-inflammatory cells, cytokines and other inflammatory mediators in tears of KC patients, whereas inflammatory suppressants seem to be reduced 6,13 .…”

“…The recent findings of increased CT in KC patients raised the question of whether CT could help to differentiate progressive from non-progressive disease [23][24][25][26][27] . Until now all evaluations of KC progression were centered in tomographic and biomechanical corneal parameters 21,22,[28][29][30][31] , but the recently raised questions of an inflammatory hit in the disease and an increased CT in those patients opens new research possibilities.…”

“…pathophysiology of KC hint to a possible inflammatory component, which might explain the increase in their CT profile compared to a healthy population 6,7,23,24 . An important clue is raised by Gutierrez-Bonet et al as they observed that the increase in CT is only verified until age 45 24 , and is well known that KC typically progresses over a period of 15-20 years from its diagnosis, usually during early adult life 1,21 .…”