This systematic review investigates the prevalence and underlying causes of corneal edema following cataract surgery employing manual phacoemulsification. A comprehensive search encompassing databases such as PubMed, Embase, ProQuest, Cochrane Library, and Scopus was conducted, focusing on variables encompassing cataract surgery and corneal edema. Two independent reviewers systematically extracted pertinent data from 103 articles, consisting of 62 theoretical studies and 41 clinical trials. These studies delved into various aspects related to corneal edema after cataract surgery, including endothelial cell loss, pachymetry measurements, visual performance, surgical techniques, supplies, medications, and assessments of endothelial and epithelial barriers. This review, encompassing an extensive analysis of 3060 records, revealed significant correlations between corneal edema and endothelial cell loss during phacoemulsification surgery. Factors such as patient age, cataract grade, and mechanical stress were identified as contributors to endothelial cell loss. Furthermore, pachymetry and optical coherence tomography emerged as valuable diagnostic tools for assessing corneal edema. In conclusion, this systematic review underscores the link between corneal edema and endothelial cell loss in manual phacoemulsification cataract surgery. It highlights the relevance of factors like patient demographics and diagnostic modalities. However, further research is essential to unravel the complexities of refractive changes and the underlying mechanisms.

Introduction There is growing evidence that confirms morphological changes in the posterior structures in patients with keratoconus (KC); however, isolated alterations could have been missed. This study assesses choroidal thickness (CT) in the fovea and beyond in KC eyes. Methods This prospective case–control and non-randomized study enrolled 107 eyes, 62 eyes of 62 patients with KC, and 45 age-matched eyes of 45 control subjects with axial length in the range of 22–26 mm. Swept-source optical coherence tomography (SS-OCT) was performed to manually measure the subfoveal choroidal thickness (SCT) using a single-line scan. CT was obtained automatically from the Early Treatment Diabetic Retinopathy Study (ETDRS) grid using the 12-lines radial scan pattern. A two-way repeated-measures analysis of variance (ANOVA) was conducted to evaluate CT variations among macular eccentricity, parafoveal area, and the interaction between both factors. CT was compared in all parafoveal areas between groups and subgroups of KC. Results SCT was significantly thicker in KC eyes (357 ± 57 µm) than in healthy eyes (325 ± 63 µm) (p < 0.001). Significant choroidal thickening was observed in the central ring and outer and inner rings of the temporal, superior, and inferior parafoveal macular areas (p < 0.001), except in the outer ring of the nasal macular zone (p > 0.05) of KC compared to healthy eyes. The CT significantly decreased from the center to the outer ring regardless of the presence of KC (p < 0.001). The choroid in the nasal macular zone was significantly thinner than that in the temporal, superior, and inferior parafoveal areas (p < 0.001). Conclusions The choroidal structure increased its thickness not only in the subfoveal area, but also in eight parafoveal areas of the ETDRS grid encompassing a wider area of macular examination. These findings demonstrate and corroborate that keratoconus is not a purely corneal disease. Furthermore, it confirms the role that the choroidal structure has in the pathophysiology of keratoconus.

Purpose: To evaluate the relationship between choroidal thickness (CT) and anterior scleral thickness (AST) in patients with subclinical keratoconus (SKC) and established keratoconus (KC). Methods: This single-center prospective case-control study included 97 eyes of 97 patients: 44 KC eyes, 14 SKC eyes, and 39 age- and axial length (AL)-matched healthy eyes. Using swept-source optical coherence tomography, the AST was manually measured in four directions and the CT was obtained automatically from the Early Treatment Diabetic Retinopathy Study (ETDRS) grid. Principal component analysis (PCA) was used to linearly reduce the dimensionality of nine CT inputs to one significant component, CT1. A multivariate model was created to evaluate the association between CT1, AST, and several ocular parameters in SKC and KC patients. Partial correlation was then performed to adjust the confounding factors and to examine the effect of AST on CT1. Results: The PCA showed that CT1 accounts for 86.54% of the total variance in the nine original CTs of the ETDRS grid. The CT1 model was associated with age, AL, and AST in the superior meridian in SKC eyes, whereas in KC eyes, it was correlated with gender, age, AL, and AST in the inferior meridian (p < 0.001). The partial correlation between CT1 and AST in the superior zone was found to be significant, positive, and strong in SKC eyes (r = 0.79, p = 0.019), whereas a significant, positive, and moderate correlation between CT1 and AST at the inferior zone (r = 0.41, p = 0.017) was observed in KC eyes. Conclusions: Choroidal tissue was significantly correlated with the anterior sclera across the vertical meridian. This relationship was observed over the superior sclera in SKC eyes, whereas in established KC, it was over the inferior sclera. These results reveal new insights regarding the interactions between the anterior and posterior structures of the KC eyes and confirm the enigma of the pathophysiology of KC.

Background/Objectives: Corneal oedema is known for changing the cornea’s optical properties, particularly its ability to transmit ultraviolet (UV) light, which is crucial for visual clarity and eye health. This study explores how changes in corneal thickness in oedematous states affect UV light transmission. Methods: This study included 107 porcine eyes with artificially induced corneal oedema. Corneal thickness (CCT) was measured histologically, UV transmittance was assessed using a UV/VIS spectrometer, and endothelial cell parameters were evaluated with specular microscopy. Statistical analyses included the Kruskal–Wallis test, Mann–Whitney U test, and Spearman’s correlation. Results: The findings indicated a significant increase in CCT in oedematous corneas at 24 and 48 h post extraction compared to controls, with median CCT values of 816.59 ± 139.71 μm for controls, 1022.40 ± 234.48 μm at 24 h, and 1074.21 ± 220.83 μm at 48 h (p < 0.001). UV transmittance (395–280 nm) decreased substantially, dropping from 50.79 ± 7.65% in controls to 43.24 ± 5.35% at 24 h and 39.66 ± 6.51% at 48 h (p < 0.001). There was a significant negative correlation between CCT and UV transmittance (ρ = −0.346, p < 0.001). Endothelial parameters showed notable changes: maximum cell area (Area_MAX) decreased at 24 and 48 h, while endothelial cell density (ECD) increased at 24 h. Conclusions: Our study found a substantial inverse link between CCT and UV light transmission in oedematous corneas, highlighting the importance of UV protection, especially in individuals who are prone to recurrent oedema. Changes in CCT and endothelial measures, such as Area_MAX and ECD, are useful signs of corneal integrity. However, the study’s small sample size and potential tissue modifications during processing need more research with bigger, in vivo samples to corroborate these findings and improve therapeutic use.

Background/Objectives: The aim of this work is to investigate how corneal oedema influences the thickness of several corneal layers and the refractive index (n_cornea), therefore clarifying its effect on corneal structure and endothelial function.Subjects/Methods: A laboratory study was conducted with thirty-four porcine eyes, categorised into three groups: Control (non-oedematous), 24-h oedema, and 48-h oedema. The thickness of corneal layers—epithelium (ET), Bowman’s membrane (BMT), stroma (ST), Descemet’s membrane (DMT), and endothelium (EnT)—was assessed histologically. Endothelial morphology was evaluated using specular microscopy, and corneal measurements were obtained with an Abbe refractometer. Statistical analyses comprised the Kruskal-Wallis test, Spearman correlations, Wilcoxon signed-rank tests, and multiple regression models.Results Control (1.36475 ± 0.0044); 24-h (1.36025 ± 0.0097); 48-h (1.3485 ± 0.0040; p = 0.001); n_cornea significantly dropped as oedema progressed. BMT, ST, and EnT were clearly thickened; ST grew by 85% after 48 hours. n_cornea revealed a substantial negative correlation with BMT (ρ = -0.491, p = 0.0002) and ST (ρ = -0.684, p = 0.002), but the maximum endothelial cell area (Area_MAX) was favourably associated (ρ = 0.502, p = 0.039). The Wilcoxon test confirmed, at p = 0.001, that n_cornea was routinely less than Gullstrand's theoretical value, 1.3771, in all groups.Conclusions Corneal oedema significantly thickens corneal layers and lowers n_cornea, therefore affecting optical clarity and measurement accuracy. These findings challenge the idea that ophthalmic equipment should have a fixed corneal refractive index (1.3771), emphasising the need for dynamic index modifications to improve surgical and diagnostic accuracy.