Segment Spectral-domain Optical Coherence Research Articles

Influence of sutureless 23-gauge sclerotomy architecture on postoperative intraocular pressure decrease: results of a multivariate analysis

To evaluate the factors affecting the postoperative intraocular pressure (IOP) decrease in 23-gauge (23-G) sutureless vitrectomy, including incision architecture evaluated by anterior segment spectral-domain optical coherence tomography (SD-OCT). A prospective cohort study of 43 patients who underwent primary transconjunctival 23-G pars plana vitrectomy. All sclerotomy wounds were imaged 1day after surgery using the anterior segment module of SD-OCT (OCT Spectralis, Heidelberg Engineering, Heidelberg, Germany). 23-G sclerotomy architecture, preoperative and postoperative medical data were also prospectively collected. Multivariate logistic regression analysis, with backward elimination, found that surgery duration (adjusted OR = 9.17, p = 0.020) and loss of wound apposition (adjusted OR = 15.12, p = 0.022) were risk factors for significant postoperative IOP decrease (≥3mmHg) 1day after surgery; while age, gender, myopia, and gas tamponade were not risk or protective factors for postoperative IOP decrease. In 23-G pars plana vitrectomy, the early postoperative decrease in IOP is mainly influenced by surgery duration and the self-sealing nature of the sclerotomy. The IOP decrease was not influenced by the presence or the absence of gas tamponade.

In vivo human crystalline lens topography

Custom high-resolution high-speed anterior segment spectral domain optical coherence tomography (OCT) was used to characterize three-dimensionally (3-D) the human crystalline lens in vivo. The system was provided with custom algorithms for denoising and segmentation of the images, as well as for fan (scanning) and optical (refraction) distortion correction, to provide fully quantitative images of the anterior and posterior crystalline lens surfaces. The method was tested on an artificial eye with known surfaces geometry and on a human lens in vitro, and demonstrated on three human lenses in vivo. Not correcting for distortion overestimated the anterior lens radius by 25% and the posterior lens radius by more than 65%. In vivo lens surfaces were fitted by biconicoids and Zernike polynomials after distortion correction. The anterior lens radii of curvature ranged from 10.27 to 14.14 mm, and the posterior lens radii of curvature ranged from 6.12 to 7.54 mm. Surface asphericities ranged from −0.04 to −1.96. The lens surfaces were well fitted by quadrics (with variation smaller than 2%, for 5-mm pupils), with low amounts of high order terms. Surface lens astigmatism was significant, with the anterior lens typically showing horizontal astigmatism ( ranging from −11 to −1 µm) and the posterior lens showing vertical astigmatism ( ranging from 6 to 10 µm).

Quantitative OCT-based corneal topography in keratoconus with intracorneal ring segments

Custom high-resolution high-speed anterior segment spectral domain Optical Coherence Tomography (OCT) was used to characterize three-dimensionally (3-D) corneal topography in keratoconus before and after implantation of intracorneal ring segments (ICRS). Previously described acquisition protocols were followed to minimize the impact of the motions of the eye. The collected set of images was corrected from distortions: fan (scanning) and optical (refraction). Custom algorithms were developed for automatic detection and classification of volumes in the anterior segment of the eye, in particular for the detection and classification of the implanted ICRS. Surfaces were automatically detected for quantitative analysis of the corneal elevation maps (fitted by biconicoids and Zernike polynomials) and pachymetry. Automatic tools were developed for the estimation of the 3-D positioning of the ICRS. The pupil center reference was estimated from the segmented iris volume. The developed algorithms are illustrated in a keratoconic eye (grade III) pre- and 30 days post-operatively after implantation of two triangular-section, 0.3-mm thick Ferrara ring segments. Quantitative corneal topographies reveal that the ICRS produced a flattening of the anterior surface, a steepening of the posterior surface, meridional differences in the changes in curvature and asphericity, and increased symmetry of the anterior topography. Optical distortion correction through the ICRS (of a different refractive index from the cornea) allowed accurate pachymetric estimates, which showed increased thickness in the ectatic area as well as in peripheral corneal areas. Automatic tools allowed estimation of the depth of the implanted ICRS ring, as well as its rotation with respect to the pupil plane. Anterior segment sOCT provided with fan and optical distortion correction and analysis tools is an excellent instrument for evaluating and monitoring keratoconic eyes and for the quantification of the changes produced by ICRS treatment.

Spectral domain optical coherence tomography study of pearl-like lesions in the anterior chamber

AimTo study the morphological pattern of pearl-like lesions in the anterior chambers of children before and after management using anterior segment spectral domain optical coherence tomography (SD-OCT).Patients and methodsThis was a prospective, observational cross-sectional study of patients presenting with peculiar pearl-like lesions in the anterior chamber of their eyes. 1 mL of betamethasone sodium phosphate (2 mg/mL) and betamethasone dipropionate (5 mg/mL) was injected subconjunctivally. Follow-ups of all patients were conducted for a period of 6 weeks. Anterior segment imaging was done using SD-OCT and also photo slit lamp before and after management.ResultsTwelve eyes of 12 patients were included in this study. These patients presented with pearl-like lesions in the anterior chamber with signs of anterior uveitis. There was no history of ocular injury or tuberculosis in any patients. Six weeks after subconjunctival steroid injection, all patients achieved mean best-corrected visual acuity, which changed from 0.2 (range 0.1–0.4) to 0.5 (range 0.4–0.8), and the severity of iritis decreased. SD-OCT showed that the lesions at presentation appeared as a globular noncystic mass attached to the back of the cornea, encroaching on the angle of the eye, and attached to the anterior surface of the iris at some points.ConclusionSD-OCT for imaging the anterior segment allowed us to exclude the cystic nature of this pearly lesion. Some similarities may exist between these pearly lesions and superficial phlyctenular keratitis, which may support the immunological and inflammatory origin of these lesions.

Spectral domain anterior segment optical coherence tomography assessment of pterygium and pinguecula

To study the morphological patterns of pterygia and pingueculae using high-resolution anterior segment spectral domain optical coherence tomography (SD-OCT). Prospective cross-sectional study of 25 eyes presented with pterygia and pingueculae was conducted, and the eyes were examined by anterior segment SD-OCT. We examined 25 eyes, including 13 eyes with primary pterygia, six eyes with recurrent pterygia, one case with a pseudopterygium and five eyes with pingueculae. Primary pterygia revealed elevation of the corneal epithelium by a wedge-shaped mass of tissue separating the corneal epithelium from the underlying Bowman's membrane, which became wavy and interrupted. We found satellite masses of pterygium tissue advanced under the epithelium beyond the clinically seen pterygium margins. In recurrent pterygia, we detected that the central tip of the pterygium was more advanced and creeping beneath the basal corneal epithelium than the primary pterygium. In pseudopterygium, the SD-OCT images showed that the overgrowing membrane was not really attached to the underlying cornea. In cases of pingueculae, SD-OCT revealed a wedge-shaped mass that was nearly similar in pattern to that of the pterygia but stopped at the limbal region. Immediately after removal of pterygia, we noticed many remnants of the pterygia masses over the corneal stroma in spite of the clinically clear appearance of cornea. SD-OCT provided us with high-resolution images of the pterygium and the pinguecula and showed clearly the anatomical relationship between the corneal tissues and these lesions. The use of this new modality of imaging may help to decrease the current recurrence rates after pterygium excision through using the anterior segment SD-OCT in the evaluation of these lesions.

Intraoperative Use of Three-Dimensional Spectral-Domain Optical Coherence Tomography

To develop a prototype three-dimensional anterior segment spectral-domain optical coherence tomography (SD-OCT) device and demonstrate the feasibility of its use in the operating room. Single-institution interventional case series including six consecutive patients undergoing Descemet's stripping automated endothelial keratoplasty (DSAEK). The prototype anterior segment SD-OCT was used intraoperatively to search for the presence of interface fluid between the host cornea and the DSAEK graft. Anterior segment SD-OCT was successfully used intraoperatively during DSAEK. After the initial placement of the graft, no fluid was clinically apparent; however, interface fluid was identified by anterior segment SD-OCT in two of the six cases. After additional aspiration, all patients were fluid-free on follow-up anterior segment SD-OCT scanning. Intraoperative anterior segment SD-OCT was used successfully to find interface fluid that was clinically undetectable under the microscope. As such, all patients were able to leave the operating room with a fully attached graft.

Tear Meniscus Height Determination Using the OCT2 and the RTVue-100

To compare anterior segment spectral-domain optical coherence tomography (SOCT) tear meniscus height (TMH) measures with those from the more commonly used time-domain OCT (TOCT). The right eye of 50 healthy subjects had images of their TMH captured with TOCT (OCT2) and SOCT (RTVue-100). Data were acquired using two different anterior segment lenses, the cornea/anterior module-short (CAM-S) and long (CAM-L), on the SOCT. Images were then analyzed for differences in their derived TMH. The average TMH for TOCT was 0.280 ± 0.139 mm, whereas the mean TMH measured using the SOCT was 0.354 ± 0.163 mm and 0.345 ± 0.167 mm for the CAM-S and CAM-L, respectively. There was a significant difference (p < 0.001) when comparing TOCT with either of the SOCT lenses. There was no statistically significant difference between the CAM-L and CAM-S (p = 1.0). Bland-Altman analysis showed poor agreement between TOCT and SOCT (95% limits of agreement -0.138 to + 0.285 mm for the CAM-S and -0.185 to +0.315 mm for the CAM-L). The RTVue-100 produces TMH measurements that are significantly higher than OCT2 in a normal patient population. However, the RTVue-100 showed a number of other advantages over the OCT2 in the measurement and analysis of images. Future work needs to determine the causative factors behind the observed differences.

Dynamic Evaluation of Sutureless Vitrectomy Wounds: An Optical Coherence Tomography and Histopathology Study

To investigate the in vitro dynamic wound morphology of fresh 25- and 23-gauge sutureless sclerotomy wounds. Experimental study; laboratory investigation. Sixteen eyes of New Zealand white rabbits. Eight cadaver heads were obtained, and the eyes were enucleated with their conjunctiva intact to simulate an intact globe. Four eyes were analyzed using 4 different wound types and cannula sizes: 25-gauge straight incision (group a); 25-gauge angled incision (group b); 23-gauge straight incision (group c); and 23-gauge angled incision (group d). Three incisions were created in each eye using either a 25- or 23-gauge trocar/cannula system. Intraocular pressure (IOP) was controlled with intraocular balanced salt solution infused through the infusion cannula. The incisions were imaged with a prototype, anterior segment spectral domain optical coherence tomography device under variable IOP to simulate successive blinks or rubbing of the eye and to evaluate the wounds in a dynamic state. Finally, India ink was applied to the surface of the eye under variable IOP to evaluate for wound leakage and potential ink ingress. The eyes were then analyzed by frozen section. Wound gaping as evaluated with optical coherence tomography (OCT) and presence of India ink particles in incisions evaluated by histology. Gross examination revealed obvious leakage of intraocular fluid in groups A and C (straight incisions) under variable IOP, with some even developing conjunctival blebs. Groups B and D (angled incisions) demonstrated minimal to no clinical leakage. Spectral domain optical coherence tomography demonstrated open wounds in straight incisions under all IOP conditions, with a slightly larger open wound under high IOP. Angled incisions demonstrated less wound gap overall and better wound apposition under high IOP versus low IOP. Histologic examination revealed India ink particles in all straight incisions with penetration across the whole incision in some wounds, whereas no ink particles were observed in angled incisions. Angled incisions have been proposed for sutureless vitrectomy to prevent wound leakage, hypotony, and the secondary risk of endophthalmitis. This study demonstrates that angled incisions provide better wound apposition under dynamic IOP conditions immediately after formation that simulate real-world situations: blinking, squeezing, or even rubbing of the eye. Proprietary or commercial disclosure may be found after the references.