Corneal biomechanical changes in allergic conjunctivitis

Abstract

Background To explore corneal biomechanical changes, identify related factors and determine early indicators of keratoconus (KC) development risk in allergic conjunctivitis (AC) patients. Methods A total of 50 patients, including 20 eyes without AC and 30 eyes with AC were enrolled in this study. All patients underwent a complete ocular examination, including evaluations of clinical manifestations of AC, corneal tomography and densitometry by Pentacam, corneal biomechanics by Corvis ST, and corneal and epithelial thickness mapping by RTvue optical coherence tomography (OCT). Results The index of surface variance (ISV), index of vertical asymmetry (IVA), keratoconus index (KI), index of height decentration (IHD) and Belin/Ambrosio enhanced ectasia total deviation index (BAD-D) were significantly higher in the AC group than in the non-allergic conjunctivitis (NAC) group (P < 0.05). The tomography and biomechanical index (TBI) was also significantly higher in the AC group (P = 0.04). The average epithelial thickness in the 2–7 mm annulus was significantly thinner in the AC group than in the NAC group (P < 0.05). The average densitometry of the total cornea and the anterior layer were higher in the AC group than in the NAC group (P < 0.001). The ISV, IVA, KI, IHD and BAD-D were significantly correlated with the TBI and changes in corneal epithelial thickness in AC patients (P < 0.05). The changes in epithelial thickness were closely related to the eye rubbing frequency and allergic sign scores (P < 0.05). Conclusions AC patients should be advised to routinely undergo corneal tomographic and biomechanical measurements, and the TBI could be used as an indicator of KC development risk in AC patients. Trial registration Corneal Biomechanical Changes of Allergic Conjunctivitis, NCT04299399. Registered March 3, 2020 - Retrospectively registered.

Changes in Anterior and Posterior Corneal Elevation in Patients With Allergic Conjunctivitis

“…Therefore, among the parameters evaluated in their study, posterior corneal elevation changes were identified as the earliest sign of subclinical KC ( 15 , 16 ). Additionally, in our study, we found that the increased elevations of both the anterior and posterior corneal surfaces were positively correlated with altered TBI, which was identified as a sensitive indicator of KC development risk in AC patients in our previous study ( 19 ). This result to a certain extent demonstrates the possibility and risk of KC occurrence in AC patients.…”

“…However, sensitive indicators for screening AC patients at high risk of developing KC are still under investigation. In our previous study, we showed that TBI could be used as an indicator of KC development risk in AC patients ( 19 ). In the current study, we found that both the anterior and posterior corneal elevation values were significantly higher in AC patients than in normal subjects and were further identified to positively correlate with the altered TBI in AC patients.…”

“…Eye rubbing frequency and ocular allergy signs were evaluated in AC patients as reported in our previous study ( 19 ). Briefly, eye rubbing frequency was assessed on a scale from 1 (absent) to 5 (constant eye rubbing).…”

“…An example of the data output for corneal elevations assessment is shown in Figure 1 . The corneal biomechanical parameters measured by Corvis ST have been presented in detail in our previous article ( 19 ). TBI was selected for analysis in this study because we previously found that only TBI showed significant differences between AC patients and normal subjects.…”

“…Moreover, VKC was reported to cause a reduction in corneal biomechanics, as indicated by decreased corneal resistance factor (CRF) (18). Additionally, our previous study found alterations in the tomography and biomechanical index (TBI) in AC patients (19). In terms of posterior corneal surface changes in AC patients, studies have mainly concentrated on corneal aberrations and densitometry, and few have investigated posterior surface elevations.…”