OCT for glaucoma diagnosis, screening and detection of glaucoma progression.

Optical coherence tomography (OCT) is a commonly used imaging modality in the evaluation of glaucomatous damage. The commercially available spectral domain (SD)-OCT offers benefits in glaucoma assessment over the earlier generation of time domain-OCT due to increased axial resolution, faster scanning speeds and has been reported to have improved reproducibility but similar diagnostic accuracy. The capabilities of SD-OCT are rapidly advancing with 3D imaging, reproducible registration, and advanced segmentation algorithms of macular and optic nerve head regions. A review of the evidence to date suggests that retinal nerve fibre layer remains the dominant parameter for glaucoma diagnosis and detection of progression while initial studies of macular and optic nerve head parameters have shown promising results. SD-OCT still currently lacks the diagnostic performance for glaucoma screening

Live outflow imaging in porcine eyes

Purpose: Although outflow of aqueous humor can be estimated using fluorophotometry and tonography, no method exists to assess segmental outflow directly. This has hindered investigations into outflow resistance elements that are downstream of the trabecular meshwork and into causes of failure of canal-based minimally invasive glaucoma surgeries (MIGS). Here, we describe a method to observe and quantify conventional outflow directly in ex vivo whole eyes and an organotypic culture model using standard fluorescence visualization equipment. Results: Aqueous outflow paths could be distinguished from venous and arterial vessels. Intricate vascular tree filling patterns were observed down to estimated 50 micrometer diameter. Whole eyes demonstrated significantly earlier filling of the nasal (SN, IN) than of the temporal quadrants (ST, IT). The fastest, superonasal quadrant filled 1.6 times faster than the slowest, superotemporal quadrant (p≤0.05). The inferotemporal quadrant also filled faster than the superotemporal quadrant. In contrast, perfused anterior segment cultures had lost these characteristic filling time differences (p>0.05). One eye showed no outflow after 20 minutes of pressurization. After three days of culture, the same quadrant that was the fastest in whole eyes (SN), was 2.2 times as fast as the slowest (ST) but this did not reach statistical significance with the number of eyes tested. The eye without flow at 20 minutes did not recuperate during 3 days of culture. Reverse filling was occasionally seen in d3 anterior segments (bottom row, red arrowhead). Whole eyes could not be reliably cultured for 3 days. Discussion: Canalograms using a green fluorescent chromophore can be obtained with standard visualization equipment to estimate the local outflow function. Regionally different outflow patterns and filling times can be observed that match channel size equivalents in human eyes. Outflow is impaired in fresh anterior segment cultures but then normalizes to the pattern seen in whole eyes. The nasally increased flow may have implications for placement and study of MIGS

A feature agnostic approach for glaucoma detection in OCT volumes

Optical coherence tomography (OCT) based measurements of retinal layer thickness, such as the retinal nerve fibre layer (RNFL) and the ganglion cell with inner plexiform layer (GCIPL) are commonly used for the diagnosis and monitoring of glaucoma. Previously, machine learning techniques have utilized segmentation-based imaging features such as the peripapillary RNFL thickness and the cup-to-disc ratio. Here, we propose a deep learning technique that classifies eyes as healthy or glaucomatous directly from raw, unsegmented OCT volumes of the optic nerve head (ONH) using a 3D Convolutional Neural Network (CNN). We compared the accuracy of this technique with various feature-based machine learning algorithms and demonstrated the superiority of the proposed deep learning based method. Logistic regression was found to be the best performing classical machine learning technique with an AUC of 0.89. In direct comparison, the deep learning approach achieved a substantially higher AUC of 0.94 with the additional advantage of providing insight into which regions of an OCT volume are important for glaucoma detection. Computing Class Activation Maps (CAM), we found that the CNN identified neuroretinal rim and optic disc cupping as well as the lamina cribrosa (LC) and its surrounding areas as the regions significantly associated with the glaucoma classification. These regions anatomically correspond to the well established and commonly used clinical markers for glaucoma diagnosis such as increased cup volume, cup diameter, and neuroretinal rim thinning at the superior and inferior segments.Comment: 13 pages,3 figure

Glaucoma surgery calculator: limited additive IOP effect of phacoemulsification on Ab Interno Trabeculectomy

Purpose: To compare reduction of intraocular pressure (IOP) after Trabectome in pseudophakic patients and Trabectome combined with phacoemulsification (Trabectome-phaco) in phakic patients. Methods: Cases were excluded if patients were followed for less than 12 months, diagnosed with neovascular glaucoma, or required additional glaucoma surgery within 12 months after Trabectome or Trabectome-phaco. Missing data such as type of glaucoma, gender, or age was imputed by generating 5 similar but non-identical datasets. Groups were matched using Coarsened Exact Matching based on age, gender, type of glaucoma, race, preoperative number of glaucoma medications and baseline IOP. Linear regression was used to examine IOP reduction after surgery. Results: A total of 612 cases were included in the study with 248 Trabectome cases and 364 Trabectome-phaco cases. Baseline IOP was found to be statistically significant. An average of 0.73±0.03 mmHg IOP reduction is associated with an increment of 1 mmHg in baseline IOP. Type of surgery was not statistically significant after adjusting for baseline IOP, age, baseline number of glaucoma medications and type of glaucoma. Conclusion: Patients with higher baseline IOP are expected to have a greater IOP reduction

Stratification of phaco-trabectome surgery results using a glaucoma severity index

The outcomes of phacoemulsification combined with trabectome surgery was analyzed using a glaucoma severity index based on preoperative intraocular pressure (IOP), number of preoperative medications, and visual field damage. Despite a less absolute indication to lower IOP, a substantial pressure reduction was seen in patients with more advanced glaucoma

Intracameral dexamethasone reduces inflammation on the first postoperative day after cataract surgery in eyes with and without glaucoma

Purpose: To evaluate whether dexamethasone injected intracamerally at the conclusion of surgery can safely and effectively reduce postoperative inflammation and improve surgical outcomes in eyes with and without glaucoma. Methods: Retrospective chart review of 176 consecutive eyes from 146 patients receiving uncomplicated phacoemulsification (PE) (n = 118 total, 82 with glaucoma), glaucoma drainage device (GDD) (n = 35), combined PE/GDD (n = 11) and combined PE/endoscopic cyclophotocoagulation (n = 12). Ninety-one eyes from 76 patients were injected with 0.4 mg dexamethasone intracamerally at the conclusion of surgery. All eyes received standard postoperative prednisolone and ketorolac eyedrops. Outcomes were measured for four to eight weeks by subjective complaints, visual acuity (VA), slit-lamp biomicroscopy, intraocular pressure (IOP) and postoperative complications. Results: Dexamethasone significantly reduced the odds of having an increased anterior chamber (AC) cell score after PE (p = 0.0013). Mean AC cell score ± SD in nonglaucomatous eyes was 1.3 ± 0.8 in control and 0.8 ± 0.7 with dexamethasone; scores in glaucomatous eyes were 1.3 ± 0.7 in control and 0.9 ± 0.8 with dexamethasone. Treated nonglaucomatous eyes had significantly fewer subjective complaints after PE (22.2% vs 64.7% in control; p = 0.0083). Dexamethasone had no significant effects on VA, corneal changes, IOP one day and one month after surgery, or long-term complications. Conclusions: Intracameral dexamethasone given at the end of cataract surgery significantly reduces postoperative AC cells in eyes with and without glaucoma, and improves subjective reports of recovery in nonglaucomatous eyes. There were no statistically significant risks of IOP elevation or other complications in glaucomatous eyes. © 2009 Chang et al, publisher and licensee Dove Medical Press Ltd