Conjunctival thickness as a predictive imaging biomarker for the glaucoma filtration surgery outcome: An optical coherence tomography study

A machine learning approach to predict the glaucoma filtration surgery outcome

This study aimed at predicting the filtration surgery (FS) outcome using a machine learning (ML) approach. 102 glaucomatous patients undergoing FS were enrolled and underwent ocular surface clinical tests (OSCTs), determination of surgical site-related biometric parameters (SSPs) and conjunctival vascularization. Break-up-time, Schirmer test I, corneal fluorescein staining, Meibomian gland expressibility; conjunctival hyperemia, upper bulbar conjunctiva area of exposure, limbus to superior eyelid distance; and conjunctival epithelial and stromal (CET, CST) thickness and reflectivity (ECR, SCR) at AS-OCT were considered. Successful FS required a 30% baseline intraocular pressure reduction, with values ≤ 18 mmHg with or without medications. The classification tree (CT) was the ML algorithm used to analyze data. At the twelfth month, FS was successful in 60.8% of cases, whereas failed in 39.2%. At the variable importance ranking, CST and SCR were the predictors with the greater relative importance to the CART tree construction, followed by age. CET and ECR showed less relative importance, whereas OSCTs and SSPs were not important features. Within the CT, CST turned out the most important variable for discriminating success from failure, followed by SCR and age, with cut-off values of 75 µm, 169 on gray scale, and 62 years, respectively. The ROC curve for the classifier showed an AUC of 0.784 (0.692-0.860). In this ML approach, CT analysis found that conjunctival stroma thickness and reflectivity, along with age, can predict the FS outcome with good accuracy. A pre-operative thick and hyper-reflective stroma, and a younger age increase the risk of FS failure.

Ocular surface and glaucoma, a mutual relationship. Practical suggestions for classification and management

The chronic use of glaucoma medications could improve the development of an ocular comorbidity, the glaucoma therapy-related ocular surface disease. This could be related to the exposure of the conjunctiva to preservatives, but also active compounds such as prostaglandin analogues may improve the risk of ocular surface inflammation. Inflammation has a negative impact on tolerability and adherence to eyedrops and to the outcome of filtration surgery as well. A stratification of glaucoma patients based not only on visual field progression but also on glaucoma therapy-related ocular surface disease would be desirable for a strategic management. Early diagnosis, individualized treatment, and safe surgical management should be the hallmarks of glaucoma treatment. One of the main issues for the proper and successful management of patients is the right timing, effectiveness and safety for both medical and surgical treatment options leading to a precision medicine in glaucoma disease as the best modern treatment.

Bleb geometry and morphology after Preserflo Microshunt surgery: Risk factors for surgical failure

PURPOSE

To investigate the possible risk factors for treatment failure in patients who had undergone Preserflo Microshunt (PMS) implantation, using anterior-segment optical coherence tomography (AS-OCT) to analyze the internal structures of the bleb.

METHODS

The PMS blebs of 54 patients were evaluated with AS-OCT. A mathematical model was used to calculate the total filtering surface of the episcleral fluid cavity (EFC) and the hydraulic conductivity (HC) of the bleb wall. Complete and qualified success were defined as IOP between 6 and 17 mmHg with or without glaucoma medication. The relation between baseline characteristics and probability of bleb success was analyzed by bivariate and multivariate logistic regression. The main outcome measures were mean bleb wall thickness (BWT), reflectivity (BWR), HC, mean horizontal and vertical diameter and total filtering surface (TFS) of the EFC.

RESULTS

Blebs from 74% patients were considered as complete success and 26% as failure. BWR and BWT increased linearly up to the first year in both groups. BWR was higher in the group failure (p = 0.02) and BWT in the group success (p<0.001). EFC was wider and shorter in the success group (p = 0.009, p = 0.03). Higher TFS showed a negative correlation with IOP (r = -0.4, p = 0.002). Higher baseline IOP was associated with success of PMS by multivariate analysis (p = 0.01). Mean HC, 0.034 ± 0.008 (μL/min)/mm2/mmHg, was negatively correlated with bleb surface (r = -0.5, p<0.0001) and wall´s thickness (r = -0.3, p = 0.01).

CONCLUSIONS

AS-OCT revealed that successful PMS blebs could show either thick hyporreflective walls or wide filtering surfaces with thin capsules. A higher baseline IOP increased the probability of surgical success.

Effects of Topical Antiglaucomatous Medications on Conjunctival Thickness: A Prospective Anterior Segment Optical Coherence Tomography Study

Purpose: Our aim was to evaluate the effects of topical antiglaucomatous medications on conjunctival thickness using anterior segment optical coherence tomography (AS-OCT). Methods: Thirty eyes of 30 patients with primary open angle glaucoma, who had never used any antiglaucomatous medications, enrolled in this prospective study. Followed by a full ophthalmologic examination, the conjunctival thickness was measured before treatment and at 1, 3, and 6-month post-treatment by AS-OCT. Measurements were taken from the superior bulbar conjunctiva, 3-4 mm from the limbus. Results: The mean age of patients was 67.7 ± 8.6; fourteen cases (46.7%) were given latanoprost, 2 cases (6.7%) brinzolamide+timolol, 2 cases (6.7%) betaxolol, 4 cases (13.3%) travoprost, and 8 cases (26.7%) brimonidine. The mean baseline conjunctival thickness was 222.9 ± 38 μm, while the mean conjunctival thickness was 212.8 ± 36.0 μm in the first month, 198.2 ± 35.8 μm in the third month, and 187.5 ± 40.2 μm in the sixth month. Decrease in conjunctival thickness at each examination was statistically significantly compared to baseline. (P < 0.05) Decrease in conjunctival thickness in Latanoprost subgroup was statistically significant, whereas the decreases in other active ingredients were not. Conclusions: Topical antiglaucomatous medications especially prostaglandin analogs may affect conjunctival thickness even during the first few months. This thinning effect may be crucial for the conjunctiva, as the basis of the possible filtration surgery.

Preparing the ocular surface for glaucoma filtration surgery: an unmet clinical need

The mutual relationship among medical therapy, ocular surface (OS) and filtration surgery (FS) represents one of the most crucial issues in glaucoma management. As the long-term use of intraocular pressure-lowering medications significantly affect the OS health, patients with an uncontrolled disease frequently undergo glaucoma surgery in less-than-ideal conditions. As we known, OS changes strongly affect the post-operative bleb filtration capability. Therefore, improving the OS conditions before proceeding with FS is needed. Currently, given the rapid diffusion of new surgical procedures, this need is even more perceived. Nevertheless, despite surgeons retain the OS preparation of primary importance, and recognize the OS disease (OSD) as the only modifiable risk factor for filtration failure, there is no agreement on which strategies should be preferred to prepare patients. This is largely due to the lack of validated guidelines, which forces clinicians to adopt personal approaches based on evidence derived from low-quality studies. In this review, we provided an overview of risk factors involved in the FS failure, with particular attention to those depending on OS changes, and how OSD negatively affects the aqueous humor resorption after surgery. Moreover, we reported the most exploited measures to mitigate the OSD before surgery, the possible reasons underlying the absence of shared approaches, and the upcoming area of intervention to preserve the OS health during glaucoma management. Finally, based on the current evidence, we proposed a pre-operative outline reporting the main risk factors that should be considered before surgery, and the therapeutical options available to improve the OS.