Objective: To establish the relationship between uveitis and findings in corneal endothelium and corneal central thickness. Methods: A systematic literature review was performed by searching multiple medical databases, including PubMed, EMBASE, Virtual Health Library (VHL) and a gray literature search in medRxiv. Patients with a diagnosis of anterior uveitis, anterior-intermediate uveitis, and panuveitis, who had reports of specular microscopy or pachymetry, were included. Case series studies with more than 10 patients, cross-sectional, case-control and cohort studies were included. We used CLARITY tools, validated scales such as Hassan Murad, et al. and Hoy, et al. were used to perform risk of bias/quality assessment analysis. A narrative synthesis of the information in the articles was performed; additionally, a quantitative analysis was performed by means of a standardized mean difference (SMD) meta-analysis, heterogeneity was assessed by I2. We used funnel plot to assess publication bias, as well as Egger's test. The study is registered in PROSPERO (CRD42023420148) and was approved by the ethics committee of the Universidad del Rosario DVO005 2277- CV1712. Results: The systematic review included a total of 34 eligible studies involving 1,388 eyes of patients with various types of anterior uveitis, including idiopathic, non-infectious and infectious uveitis. Endothelial parameters, including endothelial cell density (SMD = - 0.93 (95% CI -1.12, -0.74) (P <0.00001)), coefficient of variation (SMD = 0.66 (95% CI 0.47, 0.84) (P<0.00001)) and hexagonality (SMD = -0.68 (95% CI -0.85, -0.50) (P<0.00001)), had a significant mean difference in uveitis compared to healthy controls. However, there was no significant difference in corneal thickness between uveitis and controls (P 0.15). In the subgroup analysis of endothelial cell density, active uveitis and chronic-recurrent uveitis were found to have lower endothelial cell density than controls, only chronic-recurrent uveitis was different from the acute uveitis subgroup. On the other hand, the coefficient of variation was found to be increased compared to healthy controls in active, acute and chronic-recurrent uveitis, but no differences were found in the subgroups. Regarding hexagonality inactive, acute and chronic-recurrent uveitis had lower hexagonality than healthy controls and presented significant differences in the analysis by subgroups. The findings in central corneal thickness showed greater thickness in patients with active and acute uveitis versus healthy controls and also versus the subgroup where they were also statistically different. Discussion: Considering the results we can affirm that there is a negative effect of uveitis on the corneal endothelium and corneal thickness. On the other hand, in the analysis by subgroups it was observed that the corneal endothelium variables had more changes in acute uveitis, so we believe that initially the changes may be only transitory, but with the results in chronic-recurrent uveitis we see that inflammation over time may perpetuate the changes. Finally, the cornea has a very interesting behavior as it becomes thicker in patients with active and acute uveitis, which is similar to what happens in the retinal nerve fiber layer, so the number of studies should be increased to determine if this thickness can impact intraocular pressure measurements or also in the decisions made to perform refractive surgeries. Conclusions: Anterior uveitis can potentially damage the corneal endothelium and cause increased corneal thickness. These changes we think may be transient; however, if inflammatory states are perpetuated, they may generate permanent changes on corneal endothelial variables. Our findings raise new doubts about the biases that may be present in the measurement of intraocular pressure and in refractive surgery decisions in these patients. On the other hand, we see that early management is essential to prevent endothelial changes in patients with uveitis. The impact of cataract surgery on endothelial cells and endothelial values in active and acute uveitis require further investigation.
