Supriya Dabir

Subthreshold micropulse yellow laser (577 nm) in chronic central serous chorioretinopathy: safety profile and treatment outcome.

PurposeTo assess the safety and efficacy of a single session of subthreshold micropulse (SM) yellow laser (577 nm) in the treatment of chronic central serous chorioretinopathy (CSCR).MethodsThis was a retrospective analysis of 15 eyes of 13 patients with CSCR of >3 months duration who had been treated with SM yellow laser (577 nm). All patients had been treated using multiple spots of laser with a duty cycle of 10% over areas of focal and diffuse leak, as seen on fundus fluorescein angiography (FFA) and indocyanine green angiography (ICGA). Reduction in subretinal fluid height on spectral domain optical coherence tomography (SD-OCT) was used to measure the response to treatment.ResultsThe mean follow-up was at 8 weeks (4–19 weeks). All eyes responded to treatment. The mean subretinal fluid height pre and post treatment was 232 and 49 μm, respectively, showing a 79% average reduction (P<0.001) in fluid height. There was no evidence of retinal pigment epithelium or retinal damage on SD-OCT, FFA, or fundus autofluorescence. Median visual improvement was one line on Snellen’s visual acuity chart (P=0.015). Microperimetry was performed in eight eyes of which six eyes (75%) showed an improvement in the threshold values post treatment.ConclusionSM yellow laser is an effective treatment option for chronic CSCR.

Differential systemic gene expression profile in patients with diabetic macular edema: Responders versus nonresponders to standard treatment

Introduction: Diabetic macular edema (DME) is a vision-threatening complication of diabetic retinopathy. The current practice of management is a trial and error method of using intravitreal antivascular endothelial growth factor (VEGF)” or steroids to treat the patient and watch the response. However, if the patients genetic profile helps us choose appropriate medicine, it would help customize treatment option for each patient. This forms the basis of our study. Materials and Methods: A case-control, prospective, observational series, where DME patients were treated with bevacizumab and subclassified as treatment naοve, treatment responders, and treatment nonresponders. Blood samples of 20 subjects were studied, with five patients in each of the groups (nondiabetic- group 1, treatment naοve- group 2, treatment responder- group 3, and treatment nonresponder-group 4). Whole blood RNA extraction followed by labeling, amplification and hybridization was done, and microarray data analyzed. Genes were classified based on functional category and pathways. Results: The total number of genes upregulated among all three experimental groups was 5, whereas 105 genes were downregulated. There were no common genes upregulated between the responders and nonresponders. There was only one gene upregulated between the diabetic and diabetic responders posttreatment. There were 19 genes upregulated and 8 genes downregulated in the inflammatory pathway in group 2 versus group 1. There were no downregulated genes detected in vascular angiogenesis and transcription group. There were identical numbers of genes up- and downregulated in the inflammatory pathway. Seventeen genes were upreguated and 11 genes downregulated in receptor activity, which remained the predominant group in the group classification. Discussion: In summary, this study would provide an insight into the probable signaling mechanisms for disease pathogenesis as well as progression. This type of study eventually would aid in developing or improvising existing treatment modules with a rational approach towards personalized medicine, in future addressing the differential responses to treatment.

The use of handheld spectral domain optical coherence tomography in pediatric ophthalmology practice: Our experience of 975 infants and children.

Purpose: Optical coherence tomography (OCT) is an important imaging tool assessing retinal architecture. In this article, we report a single centers experience of using handheld spectral domain (SD)-OCT in a pediatric population using the Envisu 2300 (Bioptigen Inc., Research Triangle Park, NC, USA). Methods: We studied SD-OCT images from 975 patients imaged from January 2011 to December 2014. The variety of cases that underwent an SD-OCT was analyzed. Cases examples from different case scenarios were selected to showcase unique examples of many diseases. Results: Three hundred and sixty-eight infants (37.7%) were imaged for retinopathy of prematurity, 362 children (37.1%) underwent the test for evaluation of suboptimal vision or an unexplained vision loss, 126 children (12.9%) for evaluation of nystagmus or night blindness, 54 children (5.5%) for an intraocular tumor or a mass lesion such as retinoblastoma, and 65 children (6.7%) for other diseases of the pediatric retina. The unique findings in the retinal morphology seen with some of these diseases are discussed. Conclusion: The handheld SD-OCT is useful in the evaluation of the pediatric retinal diseases. The test is useful in the assessment of vision development in premature children, evaluation of unexplained vision loss and amblyopia, nystagmus and night blindness, and intraocular tumors (including retinoblastoma).

Normative Database of Retinal Oximetry in Asian Indian Eyes

Objective To study the oxygen saturation profile in normal Asian Indian eyes. Design A cross sectional prospective study. Subjects Ninety eight consecutive patients presenting to our hospital with best corrected distance visual acuity (BCVA) of 20/20 and a normal ophthalmic examination were included in the study. Patients having any ocular or systemic disease were excluded from the study. Materials and Methods Oximetry was performed on all subjects with the Oxymap T1 retinal oximeter (Oxymap hf, Reykjavik, Iceland). Main Outcome Measures The images were analysed for oxygen saturation and diameter. Results The mean age was 33 years (Range: 18-63; SD: 12.4). The average arteriolar saturation was 90.3 ± 6.6% and the venous saturation was 56.9% ± 6.3. The average A-V (arterio-venous) difference was 33.2% ± 5.2. There was an increase in arteriolar (R2 = 0.264; p=0.001) and venous saturation (R2 = 0.151; p=0.001) with age. There was no significant change in the arterio-venous saturation difference (AVSD). The inferotemporal quadrant had the lowest saturations. Age correlated positively with ocular perfusion pressure (OPP)(R2 = 0.07; p=0.007). OPP correlated positively with global arteriolar saturation (R2=0.057, p=0.018). Conclusion This study provides the normative database for an Indian population and is comparable to previous studies. Age, vessel diameter and OPP were the significant factors that influenced the saturation. Arteriolar and venous saturations increased with age while the AVSD did not change significantly.

Microscope-integrated optical coherence tomography: A new surgical tool in vitreoretinal surgery

Optical coherence tomography (OCT) has revolutionized imaging of ocular structures and various disease conditions. Though it has been used in the clinic for some decades, the OCT has only recently found its way into the operating theater. Early attempts at intraoperative OCT, hand-held and microscope mounted, have already improved our understanding of the surgical pathology and the role it might play in surgical decision-making. The microscope-integrated OCT now allows seamless, high-resolution, real-time imaging of surgical maneuvers from the incision to wound closure. Visualization of instruments and intraoperative tissue manipulation are possible with this in vivo modality and, therefore, help improve the outcome of surgery. In this article, we describe the advantages it offers during various vitreoretinal procedures.

Adaptive optics imaging of the retina

Adaptive optics is a relatively new tool that is available to ophthalmologists for study of cellular level details. In addition to the axial resolution provided by the spectral-domain optical coherence tomography, adaptive optics provides an excellent lateral resolution, enabling visualization of the photoreceptors, blood vessels and details of the optic nerve head. We attempt a mini review of the current role of adaptive optics in retinal imaging. PubMed search was performed with key words Adaptive optics OR Retina OR Retinal imaging. Conference abstracts were searched from the Association for Research in Vision and Ophthalmology (ARVO) and American Academy of Ophthalmology (AAO) meetings. In total, 261 relevant publications and 389 conference abstracts were identified.

Variations in the cone packing density with eccentricity in emmetropes

AimTo describe the parafoveal cone arrangement in emmetropic subjects and its variations with eccentricity, meridians and change in axial length in Indian eyes.MethodsWe imaged 25 subjects using compact adaptive optics (AO) retinal camera prototype, the rtx1. Imaging was done at 1, 2, and 3° eccentricity from the fovea in four meridians: nasal, temporal, superior, and inferior.ResultsA statistically significant drop in the cone packing density was observed from 2 to 3° (2° eccentricity=25 350/mm2 (5300/mm2, 8400–34 800/mm2) 3° eccentricity=20 750/mm2 (6000 mm2, 9000–33 670/mm2)) P<0.05. The spacing correspondingly increased with increase in distance from the fovea (2° eccentricity=6.9 μm (0.70 μm, 5.95–11.6 μm)) and 3°eccentricity=7.80 μm (1.00 μm, 6.5–13.5 μm) P<0.05. As the axial length increases, the cone density significantly decreases. Interocular variations were noted.ConclusionWith the advent of AO, visualization at the cellular level is now possible. Understanding the photoreceptor mosaic in the parafoveal space in terms of its density, spacing, and arrangement is crucial so as to detect early pathology and intervene appropriately. Newer therapeutic modalitites that are targeted at the cellular level like yellow micropulse laser, stem cells, gene therapy and so on may be better monitored in terms of safety and efficacy.

Segmentation and analysis of retinal layers (ILM & RPE) in Optical Coherence Tomography images with Edema

Optical Coherence Tomography (OCT) is a noninvasive technique and depth-resolved imaging modality which is a prominent ophthalmic diagnostic tool. In this paper, an automated segmentation algorithm to detect few intra-retinal layers which are important for Edema detection present in Spectral Domain Optical Coherence Tomography (SDOCT) images is presented. An algorithm for accurate segmentation of intra-retinal layers for normal subjects and patients with edema is discussed. The layers segmented are Inner Limiting Layer (ILM) and Retinal Pigment Epithelium (RPE) layer. The thickness is measured and then based on the thickness the image is classified as edema or non-edema. The accuracy of the algorithm is found to be more than that of the standard edge based segmentation techniques which are more prone to detection of false and disjoint edges. The graph based segmentation is solely based on pixel intensity variation and distance between neighbour pixels. Using the weighing scheme and shortest path search, it eases the task by identifying the neighbourhood pixel having same or similar intensity value and connects it by the path having the least weight. This segmentation method is less prone to noise and the preprocessing step can be considered as optional.

Perivascular and Quadrant Nerve Fiber Layer Thickness and Its Relationship with Oxygen Saturation

ABSTRACT Purpose: To study whether there exists a relationship between retinal nerve fiber layer thickness and oxygen saturation and to identify whether perivascular thickness (pRNFL) or quadrant thickness (qRNFL) has a stronger correlation. Methods: Patients without any detectable ocular abnormality on complete ophthalmic evaluation underwent non-invasive photo-spectrometric retinal oximetry on the Oxymap T1 retinal oximeter (Oxymap hf, Reykjavik, Iceland) and spectral-domain optical coherence tomography to determine if the pRNFL (Spectralis, Heidelberg, Germany) and the qRNFL (RtVue, Optovue) correlated with the measured light intensities and the calculated retinal oxygen saturations. Results: 30 eyes of 30 patients (120 arterioles, 120 venules) were included in the study. The mean arteriolar saturations (%) were temporal: 84.5 (95% CI 82.7–86.3) and nasal: 93.5 (95% CI 91.0–95.8); venous saturations were temporal: 54.4 (95% CI 52.9–55.9) and nasal: 59.9 (95% CI 58.3–61.4). The mean pRNFL thickness (µm) around arterioles was temporal: 153.1 (95% CI 146–159) and nasal: 109.4 (95% CI 103–115); around venules it was temporal: 147.4 (95% CI 140–154) and nasal: 101.2 (95% CI 95–107). The oxygen saturations correlated significantly with pRNFL (arteriolar r = −0.514; p < 0.001 and venous r = −0.513; p < 0.001) but did not show a significant correlation with qRNFL values. Conclusion: This relationship between perivascular RNFL could be physiological or artifactual. If physiological, it would explain and form the basis of altered oxygen saturation in a multitude of diseases. If artifactual, it would necessitate the incorporation of a pRNFL correction. However, the results of this study enable us to expect increased saturation in areas of thinner RNFL or vice versa with the current methodology of retinal vessel oximetry as obtained by dual-wavelength photo-spectrometric fundus imaging.

Axial length and cone density as assessed with adaptive optics in myopia

Aim: To assess the variations in cone mosaic in myopia and its correlation with axial length (AL). Subjects and Methods: Twenty-five healthy myopic volunteers underwent assessment of photoreceptors using adaptive optics retinal camera at 2° and 3° from the foveal center in four quadrants superior, inferior, temporal and nasal. Data was analyzed using SPSS version 17 (IBM). Multivariable regression analysis was conducted to study the relation between cone density and AL, quadrant around the fovea and eccentricity from the fovea. Results: The mean cone density was significantly lower as the eccentricity increased from 2° from the fovea to 3° (18,560 ± 5455–16,404 ± 4494/mm2 respectively). There was also a statistically significant difference between four quadrants around the fovea. The correlation of cone density and spacing with AL showed that there was a significant inverse relation of AL with the cone density. Conclusion: In myopic patients with good visual acuity cone density around the fovea depends on the quadrant, distance from the fovea as well as the AL. The strength of the relation of AL with cone density depends on the quadrant and distance.