Handan Akil

Swept-source OCT angiography imaging of the foveal avascular zone and macular capillary network density in diabetic retinopathy

PURPOSE We compared the area of the foveal avascular zone (FAZ) and macular capillary network density at different retinal layers using swept-source optical coherence tomography angiography (OCT-A) in normal individuals and patients with diabetic retinopathy (DR). METHODS Images (a 3 × 3 mm cube centered on the fovea) were acquired in 40 eyes of 22 normal individuals and 28 eyes of 18 patients with varying levels of DR using a swept-source OCT-A device (central wavelength 1050 nm; A-scan-rate of 100,000 scans per second). En face images of the retinal vasculature were generated from the superficial and deep retinal layers (SRL/DRL). Quantitative analysis of the vessel density (VD) and FAZ area was performed. Vessel density was assessed as the ratio of the retinal area occupied by vessels. RESULTS Among the DR subjects (mean age, 72 years; 61% male), 35.7% of the eyes had mild, 35.7% moderate, and 7.1% severe nonproliferative DR (NPDR), and 21.4% and proliferative DR (PDR). The mean FAZ area in patients with DR and in normal individuals was 0.518 and 0.339 mm2, respectively, for the SRL (P = 0.003), and 0.615 and 0.358 mm2, respectively, for the DRL (P < 0.001). The mean VD (ratio) at the SRL and DRL was statistically significantly lower in patients with DR (SRL, P < 0.001; DRL, P = 0.028). CONCLUSIONS Swept-source OCT-A of the microcirculation in eyes of patients with DR can be used to quantitatively demonstrate alterations in the FAZ and VD in the SRL/DRL of the macula compared to normal eyes. Future longitudinal studies may use these metrics to evaluate changes over time or in response to treatment.

Image artefacts in swept-source optical coherence tomography angiography

Purpose To describe optical coherence tomography angiography (OCTA) image artefacts in eyes with and without ocular pathologies. Methods The OCTA images of healthy subjects and patients with age-related macular degeneration, diabetic retinopathy and retinal vascular occlusions were retrospectively reviewed. All OCTA images were obtained using a swept-source OCTA instrument (Triton, Topcon). The frequency of various image artefacts including segmentation, banding, motion, projection, masking, unmasking, doubling of the retinal vessels, blink, stretching, out-of-window and crisscross artefacts was assessed. The impact of the artefact on the grading of the images for the foveal avascular zone in deep and superficial retinal layers, capillary non-perfusion and choroidal neovascularisation (CNV) was evaluated. Results OCTA images of 57 eyes of 48 subjects including 23 eyes (40.3%) with CNV, 13 eyes (22.8%) with dry age-related macular degeneration, 9 eyes (15.7%) with cystoid macular oedema due to diabetic retinopathy or retinal vein occlusion and 12 normal eyes (21.1%) were available for evaluation. At least one type of artefact was present in the images from 51 eyes (89.4%). Banding artefact, segmentation, motion, unmasking, blink, vessel doubling, masking and out-of-window artefacts were found in 51 (89.4%), 35 (61.4%), 28 (49.1%), 9 (15.8%), 5 (8.8%), 1 (1.7%), 1 eye (1.7%) and 1 eye (1.7%), respectively. Projection artefact, stretch artefact or crisscross artefact was not observed. Banding, motion and segmentation artefacts were statistically significantly more frequent in eyes with ocular pathology compared with control eyes (all p<0.001). Eyes with choroidal diseases had significantly higher rate of segmentation error in the choriocapillaris slab compared with eyes with only retinal disease (p=0.02). In nine eyes (17.6%), the artefacts were deemed severe enough by the graders to preclude accurate grading of the image. Conclusions Image artefacts occur frequently in OCTA images. The artefacts are more frequent in eyes with pathology.

Retinal vessel density from optical coherence tomography angiography to differentiate early glaucoma, pre-perimetric glaucoma and normal eyes

Purpose To evaluate optic nerve vascular density using swept source optical coherence tomography angiography (OCTA) in patients with early primary open angle glaucoma (POAG), pre-perimetric glaucoma and normal eyes. Methods This is a prospective, observational study including 56 eyes in total and divided into 3 groups; 20 eyes with mild POAG, 20 pre-perimetric glaucoma eyes, and 16 age-matched normal eyes as controls. The optic disc region was imaged by a 1050-nm-wavelength swept-source OCT system (DRI OCT Triton, TOPCON). Vessel density was assessed as the ratio of the area occupied by the vessels in 3 distinct regions: 1) within the optic nerve head; 2) in the 3 mm papillary region around the optic disc; and 3) in the peripapillary region, defined as a 700-μm-wide elliptical annulus around the disc. The potential associations between vessel density and structural, functional measures were analyzed. Results There was a statistically significant difference for the peripapillary vessel density, optic nerve head vessel density, and papillary vessel density among all the groups (p<0.001). Control eyes showed a significant difference for all measured vessel densities compared to glaucomatous eyes (p values from 0.001 to 0.024). There was a statistically significant difference between control and pre-perimetric glaucoma eyes for peripapillary, optic nerve head and papillary vessel density values (p values from 0.001 to 0.007). The optic nerve head vessel density, superior and inferior papillary area vessel density (Pearson r = 0.512, 0.436, 0.523 respectively) were highly correlated with mean overall, superior and inferior RNFL thickness in POAG eyes (p = 0.04, p = 0.02 and p = 0.04 respectively). Multiple linear regression analysis of POAG group showed that optic nerve head vessel density in POAG group was more strongly linked to RNFL thickness than to any other variables. Conclusions Eyes with mild POAG could be differentiated from pre-perimetric glaucoma eyes, which also could be differentiated from normal eyes using OCTA-derived retinal vessel density measurements.

Clinical Results of Ab Interno Trabeculotomy Using the Trabectome in Patients with Pigmentary Glaucoma compared to Primary Open Angle Glaucoma

To evaluate outcomes of Trabectome on pigmentary glaucoma (PG) patients compared to matched controls with primary open angle glaucoma (POAG).

Optical coherence tomography angiography of the optic disc; an overview

Different diseases of the optic disc may be caused by or lead to abnormal vasculature at the optic nerve head. Optical coherence tomography angiography (OCTA) is a novel technology that provides high resolution mapping of the retinal and optic disc vessels. Recent studies have shown the ability of OCTA to visualize vascular abnormalities in different optic neuropathies. In addition, quantified OCTA measurements were found promising for differentiating optic neuropathies from healthy eyes.

Ab interno Schlemm's Canal Surgery

In primary open-angle glaucoma, the site of greatest resistance to aqueous outflow is thought to be the trabecular meshwork (TM) and inner wall of Schlemms canal. Augmentation of the conventional (trabecular) outflow pathway can facilitate physiologic outflow and subsequently lower intraocular pressure. The most recent approach to enhancing the conventional outflow pathway is via an internal approach to the TM and Schlemms canal. Ab interno Schlemms canal surgery includes 4 novel surgical approaches: (1) removal of the TM and inner wall of Schlemms canal by an internal approach (ab interno trabeculectomy), (2) implantation of a microstent to bypass the TM, (3) disruption of the TM and inner wall of Schlemms canal via an internal approach (ab interno trabeculotomy), and (4) dilation of Schlemms canal via an internal approach (ab interno canaloplasty). The first category includes the Trabectome (Neomedix, Tustin, CA, USA), and Kahook Dual Blade (New World Medical, Rancho Cucamonga, CA, USA). The second category includes the iStent (Glaukos, Laguna Hills, CA, USA), as well as the investigational Hydrus Microstent implant (Ivantis, Irvine, CA, USA). The third category includes gonioscopic-assisted transluminal trabeculotomy (iSciences catheter; Ellex, Adelaide, Australia), and 360° suture trabeculotomy (TRAB360, Sight Sciences, Menlo Park, CA, USA). The fourth category includes ab interno canaloplasty or AbiC (Ellex), and Visco360 (Sight Sciences). In contrast to external filtration surgeries, such as trabeculectomy and aqueous tube shunt, these procedures are categorized as internal filtration surgeries and are performed from an internal approach via gonioscopic guidance. Published results suggest that these surgical procedures are both safe and efficacious for the treatment of open-angle glaucoma.

Ocular manifestations of Type 1 diabetes mellitus in pediatric population

Context: To evaluate the necessity of ocular screening in Type 1 diabetes mellitus (DM). Aims: This study aims to investigate the diabetes-related ocular changes according to the glycosylated hemoglobin (HbA1c) level and duration of diabetes in children and compare the results with nondiabetic healthy children. Settings and Design: Observational cross-sectional study designed by ophthalmology and pediatric endocrinology clinics. Subjects and Methods: Forty-two children with Type 1 DM, 42 healthy gender- and age-matched children as controls were enrolled. All patients underwent ophthalmic and physical examination, with a review of medical history and current medication. HbA1c level, best corrected visual acuity, intraocular pressure (IOP), central corneal thickness (CCT), tear break-up time (BUT), Schirmer test, dilated fundus examination findings, central retinal thickness (CRT), and total macular volume (TMV) measurements were noted. Statistical Analysis: Descriptive statistics, Students t-test, Mann–Whitney U-test, Chi-square test for comparison of the group parameters and correlation analyses (Spearman analysis) were performed with SPSS statistical software 17.0 (SPSS Inc., Chicago, IL, USA). Results: Type 1 DM group exhibited significantly reduced Schirmer test, increased IOP and decreased retinal thickness relative to the age-matched control group (P < 0.05) but no statistically significant difference was found for the BUT (P = 0.182) and for the CCT (P = 0.495). The correlations between the age, duration, HbA1c and IOP, BUT, Schirmer test, TMV, CRT measurements did not reach statistical significance. Conclusions: More frequent screening may be needed for complications, including neuropathy-related dry eye syndrome, IOP changes, and diabetic retinopathy in children with Type 1 DM.

Choroidal thickness and structural glaucoma parameters in glaucomatous, preperimetric glaucomatous, and healthy eyes using swept-source OCT.

Purpose To evaluate choroidal thickness (CT) and its relationship with retinal nerve fiber layer (RNFL) and ganglion cell-inner plexiform layer thickness (GCIPLT) in glaucomatous, preperimetric glaucomatous, and healthy eyes using swept-source optical coherence tomography (SS-OCT). Methods Fifty eyes with primary open-angle glaucoma, 20 eyes with preperimetric glaucoma, and 20 age-matched healthy eyes were enrolled. Three-dimensional wide-field (12 × 9 mm) images were obtained using a SS-OCT instrument. Peripapillary CT and RNFL thickness, as well as macular CT and GCIPLT, were recorded. The correlation of the CT with nerve fiber layer and GCIPLT measurements was assessed. The association between CT and potential confounding variables including age, sex, axial length, intraocular pressure, and central corneal thickness was also examined. Results Mean peripapillary CTs were 111.7 ± 41.7, 127.7 ± 40.1, and 120.8 ± 35.4 μm in glaucomatous, preperimetric glaucomatous, and normal eyes, respectively. There was statistically significant but weak correlation for the mean RNFL and mean peripapillary CT in glaucomatous subjects (r = 0.341, p = 0.04). There was a significant correlation between RNFL thickness and peripapillary CT in 1, 2, 5, and 6 clock hours of glaucomatous eyes (r = 0.410, p = 0.005; r = 0.316, p = 0.03; r = 0.346, p = 0.02; r = 0.35, p = 0.04, respectively). Mean macular CT was 181.5 ± 70.5, 187.4 ± 65.5, and 185.4 ± 76.4 μm in glaucomatous, preperimetric glaucomatous, and healthy eyes, respectively (p = 0.7). There was no statistically significant correlation between the mean GCIPLT and mean macular CT in all subjects (p>0.05). Conclusions Choroidal thinning and its correlation with other parameters in patients with glaucoma should be further investigated with the proprietary software of SS-OCT.

Swept-source OCT angiography imaging of the macular capillary network in glaucoma

Purpose To evaluate the macular capillary network density of superficial and deep retinal layers (SRL/DRL) by swept-source optical coherence tomography angiography (OCTA) in patients with primary open angle glaucoma (POAG) and to compare the results with those of normal subjects. Method In this prospective study, 24 eyes of 24 normal individuals and 24 eyes of 24 patients with mild to moderate POAG underwent fovea centred 6×6 mm cube macular OCTA imaging by a swept-source OCTA device (Triton, Topcon, Tokyo, Japan). Quantitative analysis of the retinal vasculature was performed by assessing vessel density (VD) as the ratio of the retinal area occupied by vessels at the SRL and DRL. Results The mean VD (ratio) at the SRL and DRL was statistically significantly lower in patients with POAG (SRL, p<0.001; DRL, p<0.001). In the SRL, the mean±SD VD ratio was 0.34±0.05 in patients with POAG and 0.40±0.02 in normal individuals (p<0.001). In the DRL, the mean (SD) ratio was 0.37±0.05 in patients with POAG and 0.43±0.02 in normal individuals (p<0.001). The mean VD at the SRL was significantly correlated with ganglion cell inner plexiform layer thickness (r=0.42, p=0.04) but not with visual field mean deviation (r=0.4, p=0.06) and retinal nerve fibre layer thickness (r=0.5, p=0.06). The mean VD at the DRL did not show significant correlation with any other glaucoma parameter (p>0.05). Conclusion The assessment of macular VD by swept-source OCTA may offer additional information for detection of glaucoma.

Assessment of Anterior Segment Measurements with Swept Source Optical Coherence Tomography before and after Ab Interno Trabeculotomy (Trabectome) Surgery

Purpose. To compare the changes of anterior segment parameters, assessed by swept source anterior segment optical coherence tomography (AS-OCT) after combined Trabectome-cataract surgery and Trabectome-only surgery in open angle glaucoma patients. Methods. Thirty-eight eyes of 24 patients with open angle glaucoma were scanned with swept source AS-OCT before and 4 weeks after combined Trabectome-cataract or Trabectome-only surgery. Intraocular pressure, number of medications, and AS-OCT parameters, such as angle opening distance at 500 and 750 μm from the scleral spur (AOD500 and AOD750), trabecular-iris space area at 500 and 750 mm2 (TISA500, TISA750), angle recess area at 500 and 750 mm2 (ARA500, ARA750), trabecular iris angle (TIA), anterior chamber depth (ACD), anterior chamber width (ACW), and anterior chamber volume (ACV), were obtained before the surgery. These parameters were compared to evaluate whether the outcome of the surgery differed among the patients after the surgery. The width of the trabecular cleft was also measured for both groups. Results. The reduction of IOP and number of medications was found to be statistically significant in both groups (p < 0.001). ACD, ACV, and angle parameters such as AOD 500/750, TISA 500/750, ARA 500/750, and TIA500 showed significantly greater changes from the preoperative values to postoperative 1st month values in combined Trabectome-cataract surgery group (p < 0.05), whereas Trabectome-only group did not show statistically significant difference (p > 0.05). There was no statistically significant difference between two groups for the width of the trabecular cleft (p = 0.7). Conclusion. Anterior chamber angle parameters measured with swept source AS-OCT may be useful for evaluating glaucoma patients before and after Trabectome surgery with or without cataract surgery.