Jay Chhablani

State of science: Choroidal thickness and systemic health

The choroid is a highly vascular structure; therefore, a wide range of systemic conditions can affect it. Conversely, choroid health may also give us insight into systemic health. With the emergence of optical coherence tomography, there has been a surge in the research on choroidal thickness and factors affecting it. Studies regarding the effect of systemic health on the choroid have largely been in the form of cross-sectional, prospective, and case studies. We offer a summary of recent findings on the topic.

A randomised, double-masked, controlled study of the efficacy and safety of intravitreal bevacizumab versus ranibizumab in the treatment of macular oedema due to branch retinal vein occlusion: MARVEL Report No. 1

Purpose To assess the efficacy and safety of intravitreal bevacizumab (IVB) compared with ranibizumab (IVR) in the treatment of macular oedema due to branch retinal vein occlusion (BRVO). Methods In this prospective, randomised, non-inferiority trial, 75 participants with macular oedema due to BRVO received intravitreal injections of ranibizumab or bevacizumab after 1:1 block randomisation. The primary outcome measure was the difference in mean changes in best-corrected visual acuity (BCVA) at 6 months. Secondary outcome measures included mean change in central retinal thickness (CRT), the proportion of patients improving by >15 letters and the proportion of patients developing neovascularisation. Results Participants received either IVR (n=37) or IVB (n=38). The mean BCVA at baseline was 52.8±14.4 letters (20/80) and 56.1±10.0 letters (20/80) (p=0.24) in the ranibizumab and bevacizumab groups, respectively. At 6 months, the mean gains in BCVA were +18.1 letters (p<0.0001; 95% CI, +12.8 to +22.6) in the ranibizumab group and +15.6 letters (p<0.0001; 95% CI +12.0 to +20.5) in the bevacizumab group. The difference between the mean visual gains of the treated groups (bevacizumab–ranibizumab) was −2.5 letters (95% CI −8.0 to +5.0; p=0.74). Mean reductions in CRT at 6 months were 177.1±122.3 µm in the ranibizumab group (p<0.0001) and 201.7±166.2 µm in the bevacizumab group (p<0.0001), with no significant difference between the two groups (p=0.48). The mean numbers of ranibizumab and bevacizumab injections were 3.2±1.5 and 3.0±1.4, respectively (p=0.55). Two serious adverse events occurred in the ranibizumab group and one in the bevacizumab group but both were unrelated to intravitreal injections. Conclusions This study demonstrated significant gain in visual acuity in eyes with BRVO treated with either bevacizumab or ranibizumab. Pro-re-nata strategy was effective in maintaining the visual gain. Trial registration number http://www.ctri.nic.in/ CTRI/2012/01/003120.

Choroidal imaging: A review

Being the most vascular tissue of the eye, importance of the choroid has been very well established in various retinal and chorio-retinal diseases. Understanding of the choroidal structures has improved significantly since the evolution of enhanced depth imaging. Quantitative assessment of choroidal measurements has been found to be reproducible using different devices. This review article describes factors affecting choroidal thickness and choroidal changes in several diseases and reports its clinical importance. Evaluation of choroid would provide insight into the pathogenesis, treatment planning and follow up in chorioretinal diseases.

Automated estimation of choroidal thickness distribution and volume based on OCT images of posterior visual section

A variety of vision ailments are indicated by anomalies in the choroid layer of the posterior visual section. Consequently, choroidal thickness and volume measurements, usually performed by experts based on optical coherence tomography (OCT) images, have assumed diagnostic significance. Now, to save precious expert time, it has become imperative to develop automated methods. To this end, one requires choroid outer boundary (COB) detection as a crucial step, where difficulty arises as the COB divides the choroidal granularity and the scleral uniformity only notionally, without marked brightness variation. In this backdrop, we measure the structural dissimilarity between choroid and sclera by structural similarity (SSIM) index, and hence estimate the COB by thresholding. Subsequently, smooth COB estimates, mimicking manual delineation, are obtained using tensor voting. On five datasets, each consisting of 97 adult OCT B-scans, automated and manual segmentation results agree visually. We also demonstrate close statistical match (greater than 99.6% correlation) between choroidal thickness distributions obtained algorithmically and manually. Further, quantitative superiority of our method is established over existing results by respective factors of 27.67% and 76.04% in two quotient measures defined relative to observer repeatability. Finally, automated choroidal volume estimation, being attempted for the first time, also yields results in close agreement with that of manual methods.

Artifacts in optical coherence tomography

Optical coherence tomography (OCT) is now an integral part of management for numerous retinal diseases for diagnosis, treatment planning and follow up. OCT interpretation must involve the understanding of the associated artifacts. These artifacts can mislead physicians to wrong diagnosis or inappropriate management. This review article discusses the various types of artifacts in OCT scans obtained from various devices in various retinal diseases. This article would help to improve the understanding about the various artifacts and their clinical importance.

Central serous chorioretinopathy: what we have learnt so far.

Central serous chorioretinopathy (CSCR) is a common retinal cause of visual loss. The mainstays of management are observation, photodynamic therapy (PDT) and laser procedures. Over the past decade, there has been rapid development in the existing and novel imaging techniques, functional testing and management of CSCR. However, there is no convincing treatment designed for CSCR yet. In recent years, the advances in PDT, with various adjustments in fluence and verteporfin dosage, and the comparisons between different types of PDT for acute and chronic CSCR in recent studies have provided greater insights into the role of PDT in treating CSCR. Novel laser procedures, such as the diode micropulse laser, have shown comparable efficacy to conventional lasers without laser‐induced damage. Antivascular endothelial growth factor, which was originally developed for treating cancers, has emerged to be a potentially effective treatment for CSCR. The potential role of mineralocorticoid receptor antagonists in treating CSCR has provided greater understanding of the pathogenesis. Based on the relevant studies, mainly from the past decade, we discuss updates to the management of CSCR according to the risk factor modifications, pharmacological interventions, PDT and laser procedures and concluded that PDT is the current best option for CSCR.

Intravitreal ziv-aflibercept for recurrent macular edema secondary to central retinal venous occlusion

Dear Editor, Recurrent macular edema (ME) secondary to central retinal venous occlusion (CRVO) is a challenging situation. Recently, newer anti-vascular endothelial growth factor (VEGF) drug, aflibercept (Eyelea®, Bayer Healthcare, Germany), approved by Food and Drug Administration (FDA), has shown good treatment outcomes in randomized clinical trials in patients with ME secondary to CRVO.[1,2] However, this drug is not available in India. Ziv-aflibercept (Zaltrap; Regeneron, New York, USA), anti-VEGF drug, is a recombinant fusion protein with a similar mechanism to aflibercept. It was approved by FDA in August 2012, for the treatment of resistant metastatic colorectal carcinoma. Recently, Mansour et al. reported intravitreal ziv-aflibercept as safe treatment at 4 weeks without any ocular toxicity in patients with diabetic ME and age-related macular degeneration, and they clarified the concerns about the osmolarity of this preparation.[3,4] Here, we present a single case of off-label use of intravitreal Zaltrap® in a patient with recurrent ME secondary to CRVO. Ethics committee approval was taken to report this case. A 64-year-old male presented with a sudden vision loss in both eyes since 1-month. On examination, his best-corrected visual acuity was 20/160 in right and left eye respectively. He was diagnosed to have CRVO with ME and was treated with intravitreal bevacizumab in both eyes. His systemic investigations were within normal limits. During the follow-up of 20 months, he had multiple episodes of recurrent ME and received 12 and 13 anti-VEGF injections in right and left eye respectively, along with one intravitreal triamcinolone injection and peripheral panretinal photocoagulation in both eyes. After a treatment-free interval of 2 months that is, at 22 months of follow-up, he presented with recurrent edema in both eyes with of 20/200 in both eyes. On examination, there was ME in both eyes, with a central macular thickness (CMT) of 834 μ and 938 μ on optical coherence tomography (OCT) [Fig. ​[Fig.1a1a and ​andb].b]. In view of recurrent recalcitrant edema, after obtaining informed consent, he underwent intravitreal Zaltrap® (1.25 mg in 0.05 ml) in both eyes under aseptic conditions, with an interval of 5 days between two eyes. The patient was subsequently followed at postinjection day 1, day 7 and day 30 (1-month). He did not have any symptoms of blurred vision or ocular pain related to injection without any signs of inflammation/toxicity. At 1-month follow-up, his visual acuity improved to 20/100 and 20/159 in his right and left eye respectively. OCT showed a decrease in edema with CMT of 193 μ and 232 μ [Fig. ​[Fig.1c1c and ​andd]d] in right and left eye respectively. As there was no observed clinical toxicity at 1-month follow-up and good clinical response, the patient has been advised to undergo another injection of Zaltrap® in both eyes. Figure 1 Top panel shows severe cystoid macular edema (ME) on spectral domain optical coherence tomography in the right eye (OD) and the left eye (OS) before intravitreal ziv-aflibercept injection. Bottom panel shows significant decrease in ME at 1-month follow-up ... This is the first report of intravitreal Zaltrap® in eyes with ME secondary to CRVO. Our report presents evidence supporting the clinical safety and efficacy of a single intravitreal Zaltrap® injection and supports its use as the primary or second line of anti-VEGF therapy in recalcitrant ME due to CRVO. However, further studies are warranted to evaluate the long-term safety and efficacy of this drug in various situations where anti-VEGF therapy is indicated.

Microbiologic spectrum and susceptibility of isolates in acute postcataract surgery endophthalmitis: are they same as they were more than a decade ago?

Endophthalmitis is a severe and vision-threatening complication of intraocular surgeries like cataract surgery. Treatment of endophthalmitis includes vitreous tap/biopsy to identify the etiologic organisms and prompt initiation of broad-spectrum intravitreal antibiotics. The choice of initial broad-spectrum antibiotics is based on the susceptibility patterns of micro-organisms in a particular region. The purpose of the current study was to investigate the spectrum of organisms causing culture-proven acute postcataract surgery endophthalmitis and their antimicrobial susceptibilities at our centre between 2006 and 2013, and to compare the results with the previously published data from the same centre.1 This was a retrospective, non-comparative, consecutive case series. Microbiology records were reviewed of all the culture-proven, acute postcataract surgery endophthalmitis cases treated at L V Prasad Eye Institute, Hyderabad, India, between January 2006 and March 2013. Bacterial isolates were identified using Analytical Profile Index (API, Bio Meriux, France). The susceptibility was determined by the Kirby–Bauer disk diffusion method. …

Optical coherence tomography angiography: a non-invasive tool to image end-arterial system

Optical coherence tomography angiography (OCTA) is a relatively novel technology for in vivo imaging of vascular network. It uses moving erythrocytes as contrasting mechanism and avoids the use of intravenous dyes. A depth-resolved 3-dimensional image set can be generated within seconds using the technique of OCTA. Therefore, it possesses a great potential for widespread application in ophthalmic angiography. Herein we discuss the most common technologies behind OCTA and the scope of future technical improvement. We provide a perspective on advantages and disadvantages of OCTA over conventional fluorescein angiography and indocyanine green angiography. Lastly, current literature on the clinical application of OCTA in common ocular diseases including neovascular age-related macular degeneration, diabetic retinopathy, retinal artery and vein occlusion, and glaucoma are reviewed.

Investigation of alterations in multifractality in optical coherence tomographic images of in vivo human retina

Abstract. Optical coherence tomography (OCT) enables us to monitor alterations in the thickness of the retinal layer as disease progresses in the human retina. However, subtle morphological changes in the retinal layers due to early disease progression often may not lead to detectable alterations in the thickness. OCT images encode depth-dependent backscattered intensity distribution arising due to the depth distributions of the refractive index from tissue microstructures. Here, such depth-resolved refractive index variations of different retinal layers were analyzed using multifractal detrended fluctuation analysis, a special class of multiresolution analysis tools. The analysis extracted and quantified microstructural multifractal information encoded in normal as well as diseased human retinal OCT images acquired in vivo. Interestingly, different layers of the retina exhibited different degrees of multifractality in a particular retina, and the individual layers displayed consistent multifractal trends in healthy retinas of different human subjects. In the retinal layers of diabetic macular edema (DME) subjects, the change in multifractality manifested prominently near the boundary of the DME as compared to the normal retinal layers. The demonstrated ability to quantify depth-resolved information on multifractality encoded in OCT images appears promising for the early diagnosis of diseases of the human eye, which may also prove useful for detecting other types of tissue abnormalities from OCT images.