Deep learning is effective for the classification of OCT images of normal versus Age-related Macular Degeneration.

In recent years, ophthalmology has experienced significant developments with respect to imaging modalities. Optical coherence tomography angiography is one such technology that seeks to improve diagnostics for retinal diseases. Using standard structural ocular coherence tomography hardware, optical coherence tomography angiography demonstrates the ability to non-invasively visualise the vasculature in the retina and the choroid with high resolution, allowing greater insight into retinal vascular pathologies. In addition, retinal and choroidal vessel density and blood flow can be quantified, offering potential to assist in the diagnosis of a variety of retinal diseases. To date, numerous retinal diseases, such as open-angle glaucoma, have been found to possess a vascular component. Specifically, ischaemia of the optic nerve head and lamina cribrosa has been theorised as a causative factor in ganglion cell death; however, confirmation of this mechanism has been prohibited by the limitations of currently existing imaging modalities. Optical coherence tomography angiography provides clear imaging of these regions and the possibility to elucidate further understanding of vascular factors that contribute to glaucoma development and progression. Furthermore, this imaging modality may provide insight to neural pathologies with vascular components such as Alzheimer's disease. Herein, the authors discuss the theory of operation for optical coherence tomography angiography and the current findings from pilot studies with a focus on open-angle glaucoma. In addition, speculation is offered for future applications of the technology to study other diseases with microvascular contributions.

https://bjo.bmj.com/content/bjophthalmol/early/2016/10/04/bjophthalmol-2016-309389.full.pdf

Optical coherence tomography angiography: an overview of the technology and an assessment of applications for clinical research.

Despite the critical impact of glaucoma on global blindness, its aetiology is not fully characterised. Elevated intraocular pressure is highly associated with glaucomatous optic neuropathy. However, visual field loss still progresses in some patients with normal or even low intraocular pressure. Vascular factors have been suggested to play a role in glaucoma development, based on numerous studies showing associations of glaucoma with blood pressure, ocular perfusion pressure, vasospasm, cardiovascular disease and ocular blood flow. As the retinal vasculature is the only part of the human circulation that readily allows non-invasive visualisation of the microcirculation, a number of quantitative retinal vascular parameters measured from retinal photographs using computer software (eg, calibre, fractal dimension, tortuosity and branching angle) are currently being explored for any association with glaucoma and its progression. Several population-based and clinical studies have reported that changes in retinal vasculature (eg, retinal arteriolar narrowing and decreased fractal dimension) are associated with optic nerve damage and glaucoma, supporting the vascular theory of glaucoma pathogenesis. This review summarises recent findings on the relationships between quantitatively measured structural retinal vascular changes with glaucoma and other markers of optic nerve head damage, including retinal nerve fibre layer thickness. Clinical implications, recent new advances in retinal vascular imaging (eg, optical coherence tomography angiography) and future research directions are also discussed.

https://bmjophth.bmj.com/content/bmjophth/1/1/e000032.full.pdf

Retinal vasculature in glaucoma: a review

PURPOSE To compare results between standard and accelerated corneal collagen cross-linking (CXL) for the treatment of progressive keratoconus. METHODS We performed literature searches in PubMed, Cochrane Library, Web of Science, ISRCTN registry, ClinicalTrials.gov, and EMBASE for studies comparing conventional Dresden (C-CXL) and accelerated CXL (A-CXL). Outcomes were clinical results and changes in corneal properties. Weighted mean differences were used to evaluate the effects. RESULTS Here, 22 studies with 1158 eyes (C-CXL: 577 eyes; A-CXL: 581 eyes) were included. At the last follow-up, C-CXL was superior regarding minimum keratometry (p < 0.00001) and demarcation line depth (p < 0.00001), whereas A-CXL should be favoured when considering minimum corneal thickness (p = 0.0005). No differences in uncorrected and corrected distance visual acuity (p = 0.09 and 0.98), spherical equivalent (p = 0.11), spherical and cylindrical error (p = 0.29 and 0.32), maximal and average keratometry (p = 0.05 and 0.65), central corneal thickness (p = 0.15), corneal biomechanical properties (p ≥ 0.21 respectively), time of reepithelialization (p = 0.76), subbasal nerve density (p = 0.69), endothelial cell density (p = 0.30) and morphology (p ≥ 0.40 respectively) were found among both groups. CONCLUSION Consideration of less corneal thinning favours A-CXL, whereas the deeper demarcation line and greater changes in minimum keratometric values in C-CXL may indicate a higher treatment efficacy. Altogether, C-CXL, as well as A-CXL, provides successful results in the strengthening of corneal tissue.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/aos.13814

Comparison of standard and accelerated corneal cross‐linking for the treatment of keratoconus: a meta‐analysis

Corneal imaging is essential for diagnosing and management of a wide variety of ocular diseases. Corneal topography is used to characterize the shape of the cornea, specifically, the anterior surface of the cornea. Most corneal topographical systems are based on Placido disc that analyse rings that are reflected off the corneal surface. The posterior corneal surface cannot be characterized using Placido disc technology. Imaging of the posterior corneal surface is useful for diagnosis of corneal ectasia. Unlike corneal topographers, tomographers generate a three-dimensional recreation of the anterior segment and provide information about the corneal thickness. Scheimpflug imaging is one of the most commonly used techniques for corneal tomography. The cross-sectional images generated by a rotating Scheimpflug camera are used to locate the anterior and posterior corneal surfaces. The clinical uses of corneal topography include, diagnosis of corneal ectasia, assessment of corneal astigmatism, and refractive surgery planning. This review will discuss the applications of corneal topography and tomography in clinical practice.

Applications of corneal topography and tomography: a review.

Purpose. To investigate retinal function using microperimetry in patients affected by idiopathic epiretinal membrane (iERM) and cataract who underwent combined surgery: 4-year follow-up. Design. Prospective, interventional case series. Methods. 30 eyes of 30 consecutive patients with iERM and age-related cataract underwent 25-gauge vitrectomy and cataract surgery. At baseline, 90 and 180 days, and 1 and 4 years, we examined retinal mean sensitivity (MS), retinal mean defect (MD), fixation stability, and frequency of microscotomas using MP1 microperimetry. Best-corrected visual acuity (BCVA) and central retinal thickness (CRT) using a spectral domain optical coherence tomography (SD-OCT) were also performed. Results. All patients completed 1-year follow-up, while 23 patients reached last follow-up. Baseline MS and MD (10.48 ± 4.17 and -9.18 ± 4.40 dB) significantly changed at one year (12.33 ± 3.66 and -7.49 ± 3.31 dB, p < 0.01), at four years (14.18 ± 3.46 and -4.66 ± 2.85, p < 0.01), and between one and four years (p < 0.01) after surgery. Compared to baseline, CRT and BCVA significantly changed at one year and remained stable at four years. No variations were observed in fixation stability and frequency of microscotomas compared to baseline. Conclusions. Long-term follow-up using microperimetry seems useful to evaluate patients after iERM surgery: retinal sensitivity changes even when BCVA and CRT remain stable.

/pdf/microperimetric-assessment-after-epiretinal-membrane-surgery-4dz4b3a2yy.pdf

Microperimetric Assessment after Epiretinal Membrane Surgery: 4-Year Follow-Up

The purpose of the present is to measure and to compare the intraocular pressure (IOP) during manual and mechanical Perfluorodecalin (PFD) injection in 23 and 25-Gauge(G) simulated pars plana vitrectomy using a StellarisPC® vitrectomy system. A human eye model was developed and IOP recorded during infusion of PFD using three sensors, two located at the equator and one in an area corresponding to the macula (M) of the human eye. Three measurements were performed with 23 and 25G settings: during manual PFD injection by two vitreoretinal surgeons with different experience; during Venting Gas Forced Infusion (VGFI) of PFD at 8 psi and 12 mmHg of infusion; during VGFI of balanced salt solution at 30 mmHg of infusion in the closed eyeball model. The manual infusion of both surgeons (in particular that of the surgeon in training) showed IOP values significantly higher (p<0.0001) and more scattered than the VGFI. The average IOP recorded during VGFI at 8 psi and 12 mmHg was higher than the set one, with both 23G and 25G (29.03 and 27.56 mmHg respectively). In the closed eyeball model, the actual IOP was steady but higher than the 30 mm Hg set. In all the experiments, except for two observations, the IOP recorded at the sensor M was significantly higher than that at the equator. In conclusion, potential damage due to excessive IOP fluctuations can be minimized using the mechanical infusion. Mechanical infusion prevents sustained pressure overshoot but it introduces a systematic pressure offset.

Marco Dal Vecchio

Papers

Microperimetric Assessment after Epiretinal Membrane Surgery: 4-Year Follow-Up

Behaviour of the intraocular pressure during manual and vented gas forced infusion in a simulated pars plana vitrectomy