Anterior Segment Optical Coherence Tomography System Research Articles

Refractive Index Measurement of the Crystalline Lens in Vivo.

This study provides a new method to measure the refractive index of crystalline lens in the human eye in vivo . Accessing the refractive index of crystalline lenses in the human eye in vivo has long been a challenge. This study aimed to measure the refractive index of a lens in vivo using an anterior segment optical coherence tomography (AS-OCT) system combined with a Scheimpflug imaging system. A ray-traceable Scheimpflug imaging was developed and integrated into an AS-OCT system. A theoretical study revealed that the combination of these two systems provides a unique solution for simultaneously measuring the refractive index and the thickness of the lens. The average lens refractive index along the ray pathway ( Nav ) and lens shape were measured for seven subjects. The lens Nav along the central ray varies from 1.383 to 1.419 between subjects. The lens refractive index function across the lens diameter varies from subject to subject. The lens Nav increases for accommodated eyes. The thicknesses and profiles of the lenses are also determined. The lens refractive index varies substantially from individual eye to individual eye, not only along the central ray pathway but also for the lens refractive index function across the lens diameter. Ray-traceable Scheimpflug imaging-equipped AS-OCT is useful for testing the refractive index of lenses in the human eye in vivo .

Evaluation of Mooren's corneal ulcer by anterior segment optical coherence tomography

BackgroundThis study evaluates the use of anterior segment optical coherence tomography (AS-OCT) to identify focal changes and inform surgical plans in eyes with Mooren's ulcer. MethodsA total of 18 eyes of 17 patients with Mooren's ulcer were examined prospectively using the AS-OCT system. ResultsOptical hyperreflectivity noted on AS-OCT images was in accordance with corneal ulceration, neovascularization, fibrovascular membranes, the junction of the native stromal bed, and the overlying lamellar corneal grafts. Focal corneal ectasia was observed in 13 eyes with a decrease in corneal thickness to ≤0.39 mm. There was a cut-off value of 0.39 mm in corneal thickness between the eyes with and without focal corneal ectasia in the thinned corneal area (Fisher = 0.383, χ2 = 14.873, P = 0.000). Based on the AS-OCT findings, six eyes were subjected to an individualized lamellar corneal graft. The thickness of the residual cornea after surgery was 47 ± 34 μm less than the presumed healthy corneal thickness before surgery (t = 3.376, P = 0.02). A small corneal perforation covered by a pseudopterygium in Mooren's ulcer was found through AS-OCT but undetectable by slit-lamp biomicroscopy. ConclusionsAS-OCT is a valuable non-contact technique for monitoring corneal thinning in Mooren's ulcer, and assisting surgical design. A decrease in peripheral corneal thickness to ≤0.39 mm may cause focal corneal ectasia.

Anterior segment-optical coherence tomography for evaluation of the epithelium thickness profile in keratoconic corneas and normal corneas

Purpose This study intends to compare the characteristic distributive epithelial pattern by Fourier-domain anterior segment-optical coherence tomography (AS-OCT) corneal mapping between keratoconic and normal eyes. Patients and methods This prospective case–control study included 51 participants who were divided into two groups: study group A (formed of 50 eyes of 26 keratoconic participants) and control group B (50 eyes of 25 healthy controls of matched age and sex with group A). Maps of corneal epithelial statistics within central 5 mm [S: 2–5 mm (superior), I: 2–5 mm (inferior), minimum, maximum, SD (topographic variability), minimum−maximum], and the total corneal pachymetry maps were assessed by the Fourier-domain AS-OCT system and imaged by Scheimpflug imaging corneal topography for both groups. Results For group A of keratoconic corneas, the attained results are as follows: the mean of epithelial thickness at the center was 50.1±7.98 µm, superior 56.01±6.98 µm, inferior 48.73±5.97 µm, minimum 39.95±9.11 µm, maximum 62.92±8.85 µm, minimum−maximum −22.01±10.91 µm, and topographic variability 6.9±4.2 µm. For group B of healthy control eyes, the mean of epithelial thickness at the center was 52.71±3.71 µm, superior 52.29±3.32 µm, inferior 53.42±3.11 µm, minimum 48.89±3.71 µm, maximum 55.92±3.47 µm, minimum−maximum −6.3±3.51 µm, and topographic variability 1.53±0.82 µm. All variables of epithelial thickness between the two groups are significant (P<0.01). In comparing the epithelial map of keratoconus (KCN) with the control group, the epithelium was found to be thicker at the maximum (+7 µm) and superior location (+3.72 µm), but thinner at the minimum (−8.94 µm) and the inferior (−4.69 µm) with highly significant differences in both minimum−maximum (−15.71) and topographic variability (+5.37). Moreover, in KCN, the point of minimum epithelial thickness was in accordance with the minimum point of the total corneal thickness and the maximum point of back elevation. Conclusion The mapping for epithelial thickness utilizing AS-OCT could be a promising tool in KCN diagnosis.

Effects of 0.01% Atropine Instillation Assessed Using Swept-Source Anterior Segment Optical Coherence Tomography

In this paper, we assessed the short-term effects of 0.01% atropine eye drops on anterior segment parameters by performing ocular biometry using a swept-source anterior segment optical coherence tomography system (AS-OCT). We recruited 17 healthy volunteers (10 men and 7 women aged 24–35 years) with no history of eye disease. Participants without accommodative demand demonstrated significant mydriasis 1 h after the atropine instillation (4.58 ± 0.77 to 5.41 ± 0.83 mm). Pupil diameters with a 5 diopter (D) accommodative stimulus at 1 h (4.70 ± 1.13 mm) and 24 h (4.05 ± 1.06 mm) after atropine instillation were significantly larger than those at baseline (3.71 ± 0.84 mm). Barring pupil diameter, no other biometric parameters significantly changed at any point in time after atropine instillation without accommodative demand. However, with an accommodative stimulus, anterior chamber depth (ACD) at 1 h and posterior curvature of the lens at 1 and 24 h were both significantly larger than those before atropine instillation. Using AS-OCT, we detected a slight decrease in the accommodation response of ocular biometric components evoked by 0.01% atropine instillation. Morphologically, our measurements suggested a change in the ACD and horizontal radius of the lens’ posterior surface curvatures due to the subtle reduction of accommodation.

Longitudinal evaluation of posterior corneal power by anterior segment optical coherence tomography 18 months following photorefractive keratectomy.

To investigate the change in anterior, posterior, and net corneal power more than 18 months after photorefractive keratectomy (PRK) by RTVue anterior segment optical coherence tomography (OCT). Farabi Eye Hospital, Tehran University of Medical Sciences, Tehran, Iran. Prospective observational study. PRK was performed using Technolas TENEO 317 laser platform. Anterior, posterior, and net corneal power was measured by the RTVue-XR anterior segment OCT system with the Pachymetry + Cpwr scan pattern at baseline and months 1, 3, 6, 12, 18, and more than 18 (up to 27) after PRK. Three hundred twenty-six eyes of 163 patients (61 men [37.4%], 102 women [62.6%]; mean age 29.71 years; range 18.5 to 46.5 years) were enrolled in this study. Mean preoperative spherical equivalent was -3.15 ± 1.50 diopter (D) (range -8.37 to -0.62 D). The mean change in net corneal power was 3.052 D, 3.281 D, 3.324 D, 3.114 D, 3.446 D, and 3.972 D at months 1, 3, 6, 12, 18, and more than 18 postoperatively compared with baseline, respectively (P < .001 for all comparisons). The mean change in posterior corneal power at postoperative visits compared with baseline was not statistically significant (P > .1) except for 1 month postoperatively, which increased by 0.13 D (P < .001). Changes in posterior corneal power were not correlated with any of the preoperative clinical and Scheimpflug variables. Posterior corneal power did not change for more than 18 months after PRK, except for an early small increase at 1 month postoperatively.

Anterior Segment Biometry During Accommodation and Effects of Cycloplegics by Swept-Source Optical Coherence Tomography.

PurposeWe analyzed changes in the crystalline lens during accommodation and the effects of cycloplegics by swept-source anterior-segment optical coherence tomography (AS-OCT).Materials and MethodsTwenty healthy volunteers (7 males and 13 females, aged 22–34 years), with no history of eye disease except for refractive errors, were recruited. Biometric parameters, including anterior chamber depth (ACD), lens thickness (LT), and anterior and posterior curvature of the lens (ACL and PCL), were measured using AS-OCT (CASIA2). The measurements were performed with or without an accommodative demand of 5.0 diopters (D). The same tests were repeated following the topical administration of 1% cyclopentolate or a compounding agent comprising 0.5% tropicamide and 0.5% phenylephrine.ResultsThe AS-OCT system was capable of simultaneous visualization of all optical components of the anterior segment in a single frame. ACD, LAC, and LPC decreased and LT increased significantly during 5.0 D accommodative stimulation in both eyes. Both cyclopentolate and tropicamide/phenylephrine eyedrops led to deeper ACD, thinner LT, and flatter LAC. There were no significant differences in all lens parameters despite having 5.0 D accommodative stimulation in both eyes with cycloplegia.ConclusionOur results suggest that both tropicamide/phenylephrine and cyclopentolate eyedrops have enough cycloplegic effects in young adults.

Application of CASIA SS-1000 Optical Coherence Tomography Tear Meniscus Imaging in Testing the Efficacy of New Strip Meniscometry in Dry Eye Diagnosis.

To investigate the applicability of CASIA SS-1000 anterior-segment optical coherence tomography (AS-OCT) imaging parameters in testing the efficacy of the new strip meniscometry (SM) namely "Strip Meniscometry Tube" (SMTube) in the diagnosis of dry eyes. Forty-three eyes of 22 patients (4 men and 18 women) with definite dry eye disease (DED) and 49 eyes of 28 normal controls (6 men and 22 women) were studied. All subjects underwent symptom questionnaires, SMTube, the Schirmer-1 test, tear film break-up time measurement, vital staining examinations, as well as tear meniscus height (TMH) and TM area (TMA) measurements using an AS-OCT system. We evaluated the cutoff values for the diagnosis of DED, looked into the correlations between TMH, TMA, and SMTube scores and checked the sensitivity and specificity of these parameters in the diagnosis of DED. The mean values of TMH, TMA, and SMTube scores in the patient group were 0.138±0.102 mm, 0.013±0.015 mm and 1.4±2.3 mm, whereas those for the control group were 0.27±0.10 mm, 0.033±0.025 mm and 5.8±2.8 mm, respectively. The differences between both groups were significant (P<0.001). The cutoff values of TMH, TMA, and SMTube for DED were 0.197 mm, 0.020 mm and 3.8 mm, respectively. SMTube had significant correlations with TMH (r=0.82, P<0.001) and TMA (r=0.86, P<0.001). The SMTube was useful in DED diagnosis, the validity of which could be effectively evaluated by the CASIA SS-1000 AS-OCT TM parameters.

Pupil Tracking for Real-Time Motion Corrected Anterior Segment Optical Coherence Tomography.

Volumetric acquisition with anterior segment optical coherence tomography (ASOCT) is necessary to obtain accurate representations of the tissue structure and to account for asymmetries of the anterior eye anatomy. Additionally, recent interest in imaging of anterior segment vasculature and aqueous humor flow resulted in application of OCT angiography techniques to generate en face and 3D micro-vasculature maps of the anterior segment. Unfortunately, ASOCT structural and vasculature imaging systems do not capture volumes instantaneously and are subject to motion artifacts due to involuntary eye motion that may hinder their accuracy and repeatability. Several groups have demonstrated real-time tracking for motion-compensated in vivo OCT retinal imaging, but these techniques are not applicable in the anterior segment. In this work, we demonstrate a simple and low-cost pupil tracking system integrated into a custom swept-source OCT system for real-time motion-compensated anterior segment volumetric imaging. Pupil oculography hardware coaxial with the swept-source OCT system enabled fast detection and tracking of the pupil centroid. The pupil tracking ASOCT system with a field of view of 15 x 15 mm achieved diffraction-limited imaging over a lateral tracking range of +/- 2.5 mm and was able to correct eye motion at up to 22 Hz. Pupil tracking ASOCT offers a novel real-time motion compensation approach that may facilitate accurate and reproducible anterior segment imaging.

Comparison of anterior section parameters using anterior segment optical coherence tomography and ultrasound biomicroscopy in myopic patients after ICL implantation.

To compare the agreement of anterior chamber depth (ACD) and central vault measurements obtained by anterior segment optical coherence tomography (AS-OCT) and ultrasound biomicroscopy (UBM) of post surgical high myopic eyes with posterior chamber phakic intraocular lens (Visian ICL; STAAR Surgical) implantation. Fifty-two phakic eyes of 28 high myopic patients who underwent implantable Collamer lens (ICL) surgery for the correction of high myopia were studied. The postoperative ACD, the distance between the corneal endothelium and the anterior surface of ICL (cornea-ICL) and the central vault were measured with the AS-OCT system and the UBM system. Intraclass correlation coefficient (ICC) and the Bland-Altman plot were used to evaluate the repeatability and agreement of two devices. The mean ACD, cornea-ICL and central vault in the 52 phakic eyes after ICL surgery was 3.19±0.28 mm, 2.47±0.28 mm, 0.50±0.19 mm by AS-OCT and 3.13±0.25 mm, 2.49±0.25 mm, 0.44±0.19 mm by UBM, respectively. Pairwise comparison of ACD and central vault measurements showed significant differences between AS-OCT and UBM (P<0.05). However, no statistically significant difference was found between these imaging techniques in cornea-ICL (P>0.05). The Pearson correlation coefficient (r) between AS-OCT and UBM measurements for ACD, cornea-ICL and vault was 0.88, 0.80 and 0.89, respectively (P<0.001). The ICC was 0.89-0.94 for the measurements of AS-OCT and UBM. Bland-Altman analysis showed the 95% limits of agreement of ACD, cornea-ICL, central vault measurements between these two devices were -0.20 to 0.32 mm, -0.36 to 0.32 mm and -0.12 to 0.24 mm, respectively. Central ACD and vault measurements using AS-OCT demonstrated a slight significantly higher value than using UBM in phakic eyes after ICL surgery. These two devices should not be used interchangeably for measurements of central ACD and vault in patients after phakic intraocular lens implantation.

Descemet membrane endothelial keratoplasty: intraoperative and postoperative imaging spectral-domain optical coherence tomography.

We describe a case report of using the same handheld spectral-domain anterior segment optical coherence tomography (ASOCT) for rapid intraoperative and postoperative imaging in a case of Descemet membrane endothelial keratoplasty (DMEK). A 67-year-old woman, with Fuchs dystrophy and corneal decompensation, underwent DMEK with intraoperative ASOCT imaging using the handheld Envisu spectral domain ASOCT system (Bioptigen, Inc., Morrisville, NC, USA). We found that this easy-to-use portable system with handheld probe allowed for rapid imaging of the anterior segment during donor manipulation to visualize the orientation of the DMEK donor, as well as to confirm the initial adhesion of the DMEK donor. Moreover, the same system may be used for postoperative monitoring of graft adhesion, corneal thickness, and stromal remodeling in the clinic with very high-definition images.

Corneal epithelial remodeling following cataract surgery: three-dimensional investigation with anterior-segment optical coherence tomography.

To map corneal and epithelial layer thickness changes following cataract removal surgery employing a spectral-domain anterior-segment optical coherence tomography system. Corneal and epithelial thickness three-dimensional profile distribution was clinically imaged preoperatively and up to 3 months postoperatively with anterior-segment optical coherence tomography in 116 consecutive cases. Descriptive statistics investigated central corneal thickness, minimum corneal thickness, and epithelial thickness at the central 2-mm area, the mean over the 6-mm area, and mid-peripherally at 5-mm ring. In comparison to preoperative, the center, mean, and mid-peripheral epithelial thickness at the first postoperative day increased by +2.84, +2.35, and +2.25 μm, respectively (P < .001, < .001, and = .0014). One week postoperatively, the epithelial thickness differences were -1.91, -2.62, and -2.76 μm, respectively (P < .001, < .001, and < .001). Four weeks postoperatively, the differences of -0.20, -0.59, and -0.66 μm for the center, mean, and mid-periphery were not statistically significant (P = .6449, .1512, and .11097). Three months postoperatively, the differences were -0.05, -0.28, and -0.09 μm, respectively (P = .8722, .2341, and .6431). Qualitative and quantitative assessment of epithelial remodeling following cataract removal indicated that the early (1 day and 1 week) corneal and epithelial thickness returned to the preoperative baseline 4 weeks postoperatively. This in vivo epithelial and corneal screening with optical coherence tomography can be valuable for the postoperative assessment and follow-up.

Preoperative anterior segment optical coherence tomography as a predictor of postoperative phakic intraocular lens position

To evaluate anterior segment optical coherence tomography (AS-OCT) in the preoperative simulation of postoperative iris-fixated phakic intraocular lens (pIOL) position in the anterior chamber. Farabi Eye Research Center, Department of Ophthalmology, Tehran University of Medical Sciences, Tehran, Iran. Case series. Using AS-OCT, the pIOL position was simulated preoperatively in 2 ways and compared with the actual postoperative pIOL position. For preoperative evaluations, the simulator was placed on the posterior pigmented epithelium of the iris. Then, the simulation was performed with the simulator placed in the middle of the iris tissue. The following distances were measured: from the center of the pIOL to the endothelium, from the edge of the pIOL to the endothelium, and from the posterior surface of the pIOL to the crystalline lens. The study examined 26 eyes (16 patients). Although all distances in both simulation methods (except the lens vault in the first method of simulation) were highly correlated (all P<.009), only the results with the simulator placed in the middle of the iris tissue were not statistically different from the corresponding postoperative measurements (P=.209 and P=.564 for distance from endothelium to the center and the pIOL edge, respectively). Using the pIOL template of the AS-OCT system for preoperative simulation of iris-fixated pIOLs improved the criteria for patient selection for implantation of these pIOLs. The simulator should be placed in the middle of the iris tissue for preoperative simulation. No author has a financial or proprietary interest in any material or method mentioned.

Anterior Chamber Cell Grading by Optical Coherence Tomography

To quantify cells in the ocular anterior chamber (AC) by optical coherence tomography (OCT). A time-domain anterior segment OCT system was used to image latex microsphere suspensions in vitro and the AC of uveitis and normal subjects in vivo. The OCT scan pattern, consisting of 2- and 4-mm-diameter concentric circular scans, was divided into central, superior, and inferior regions. A computer algorithm was developed to automatically identify particles in OCT images. A uveitis specialist used slit-lamp biomicroscopy to grade the AC cells on a scale of 0 to 4+. Latex microspheres and ac cells were visualized as reflective spots in oct images. OCT latex microsphere concentration measurements were highly correlated to known particle concentrations (r = 1.000) and had an efficiency of 0.72. in 30 nongranulomatous and 12 granulomatous eyes, the OCT cell counts correlated well with slit-lamp grades in all three regions (Spearman's rho coefficient: >0.63). The average OCT cell count was 3.7 cells/grade in nongranulomatous eyes and 2.0 cells/grade in granulomatous eyes. OCT revealed significant amounts of inferior AC cells in 5 of 16 quiescent uveitis eyes (mean ± SD: 19.9 ± 7.4 cells). OCT captured rare cells in normal eyes (1.1 ± 1.1 cells centrally). OCT provided quantitative information on AC inflammatory cells. The OCT cell counts correlated well with clinical grading, and particles in the inferior AC that were missed by slit-lamp examination were detected by OCT. OCT could be a valuable tool for the diagnosis and management of anterior uveitis.

Comparison of intraoperative subtraction pachymetry and postoperative anterior segment optical coherence tomography of laser in situ keratomileusis flaps

To prospectively compare intraoperative subtraction pachymetry flap thickness measurements and postoperative anterior segment optical coherence tomography (AS-OCT) flap thickness measurements in eyes that had laser in situ keratomileusis (LASIK) flap creation with a femtosecond laser or a mechanical microkeratome. Stanford Eye Laser Center, Stanford University School of Medicine, Stanford, California, USA. Comparative case series. Each patient received wavefront-guided LASIK using an Intralase femtosecond laser in 1 eye and a Hansatome mechanical microkeratome in the fellow eye. Flap morphology was assessed with an ultrasound pachymeter intraoperatively and an AS-OCT system postoperatively at 1 year. Thirty-six eyes (18 patients) were enrolled. Intraoperative subtraction pachymetry consistently underestimated mechanical microkeratome flap thickness compared with postoperative AS-OCT (P<.001). There was no significant difference between intraoperative subtraction pachymetry and postoperative AS-OCT measurements for femtosecond flaps (P=.38). The overall mean variation in flap thickness (ie, mean deviation from targeted flap thickness) was 2.6μm (range 3 to 11 μm) with the femtosecond laser and 14.2 μm (range 17 to 52 μm) with the mechanical microkeratome (P<.001). Postoperative AS-OCT measurements showed femtosecond flaps had a planar configuration and mechanical microkeratome flaps had a meniscus-shaped configuration. The femtosecond laser created more uniformly planar flaps than the mechanical microkeratome as measured by intraoperative subtraction pachymetry and postoperative AS-OCT. Postoperative AS-OCT measurements varied less than intraoperative subtraction pachymetry measurements for mechanical microkeratome flaps. Neither author has a financial or proprietary interest in any material or method mentioned.

The Assessment of the Filtering Bleb Function With Anterior Segment Optical Coherence Tomography

To assess the usefulness of anterior segment optical coherence tomography (AS-OCT) in evaluating postoperative filtering bleb function. Forty-eight eyes of 39 patients who had earlier undergone trabeculectomy were enrolled. Blebs were imaged with a commercially available AS-OCT system. The correlation between intraocular pressure (IOP) and 4 quantitative parameters, bleb height, bleb wall thickness, and the height and extent of internal cavity, and 2 qualitative parameters, bleb wall reflectivity, and the presence or absence of posterior episcleral fluid, were analyzed. Of the 39 participants, 25 (64.1%) were males (mean age, 65.3±10.0 y). The height and extent of the internal cavity and the bleb height were not correlated with the IOP. The bleb wall thickness was negatively (P=0.004) correlated with the IOP. The mean IOP in eyes with a low-reflectivity bleb wall was significantly (P=0.001) lower than in eyes with a high-reflectivity wall. The IOP levels were significantly (P=0.008) lower in eyes with posterior episcleral fluid than in eyes without it. AS-OCT is a useful tool to evaluate filtering bleb function. The height and extent of the total bleb and the internal cavity were not correlated with IOP control. A low-reflectivity wall and the presence of episcleral fluid were associated with lower IOP.

Intraocular stability of an angle-supported phakic intraocular lens with changes in pupil diameter

To use anterior segment optical coherence tomography (AS-OCT) to evaluate the stability of a recently released angle-supported phakic intraocular lens (pIOL) in the anterior segment with changes in pupil diameter. Keratoconus Unit, Vissum Corporation, Alicante, Spain. In this observational cross-sectional study of consecutive eyes with moderate to high myopia, an AcrySof Cachet pIOL was implanted with the aim of minimizing the refractive error. An analysis of the position and stability of the pIOL before and after pharmacologic pupil dilation was performed 3 months postoperatively using the Visante AS-OCT system. A measurement protocol that included several anatomic parameters was developed and applied; the parameter values before and after dilation were compared. Twenty eyes of 20 patients ranging in age from 24 to 48 years old were evaluated. The anterior chamber depth increased significantly with pupil dilation (mean change 0.06 mm +/- 0.08 [SD]) (P<.01). A significant change was also observed in the distance between the center of the cornea at the endothelial plane and the anterior surface of the pIOL (mean change 0.03 +/- 0.05 mm) (P = .01). The distances between the peripheral edges of the pIOL and the corneal endothelium and the distance between the crystalline lens and the pIOL did not change significantly (P>or=.14). The angle-supported pIOL showed excellent intraocular behavior after pupil dilation, with no shortening of the distance between the pIOL and corneal endothelium at the center or peripheral edges of the pIOL.

Repeatability, reproducibility, and agreement of central anterior chamber depth measurements in pseudophakic and phakic eyes: Optical coherence tomography versus ultrasound biomicroscopy

To evaluate the intraexaminer repeatability, interexaminer reproducibility, and agreement of central anterior chamber depth (ACD) measurements obtained by anterior segment optical coherence tomography (AS-OCT) and ultrasound biomicroscopy (UBM) in pseudophakic eyes and phakic eyes. Eye Hospital, Wenzhou Medical College, Wenzhou, Zhejiang, China. In this prospective study, the central ACD in right pseudophakic eyes and right phakic eyes was measured with the Visante AS-OCT system and the OTI-Scan HF 35-50 UBM system. Intraexaminer repeatability and interexaminer reproducibility were evaluated in a subgroup of eyes from each group. The repeatability and reproducibility of the measurements were evaluated using intraclass correlation coefficients (ICCs) and the Bland-Altman method. The mean ACD in the 70 pseudophakic eyes was 3.91 mm +/- 0.29 (SD) by AS-OCT and 3.76 +/- 0.33 mm by UBM and in the 70 phakic eyes, 2.97 +/- 0.31 mm and 2.90 +/- 0.32 mm, respectively. The 95% limits of agreement between the 2 methods were -0.32 to 0.62 mm in pseudophakic eyes and -0.11 to 0.25 mm in phakic eyes. The ICC for the repeatability and reproducibility of AS-OCT and UBM measurements was high (range 0.985 to 0.996). Both AS-OCT and UBM ACD measurements showed good repeatability and reproducibility. However, the agreement was better in phakic eyes than in pseudophakic eyes. Thus, the measurements should not be used interchangeably in pseudophakic eyes.

Optical coherence tomography of clear corneal incisions for cataract surgery

To study the architecture of clear corneal incisions for phacoemulsification cataract surgery using optical coherence tomography (OCT). Doheny Eye Institute and Department of Ophthalmology, Keck School of Medicine of the University of Southern California, Los Angeles, California, USA. This prospective study comprised 20 eyes of 20 patients 1 month after cataract surgery performed by 1 of 2 experienced surgeons. Temporal clear corneal single-plane incisions were made with 3.0 mm metal keratomes. Each eye was scanned before and 1 month after surgery with a prototype high-speed anterior segment OCT system (Carl Zeiss Meditec, Inc.). The OCT scans were repeated 3 times during the same visit. The length of the corneal incision, thickness of the cornea, and position of the incision (distance from external wound edge to scleral spur) were measured using a computer caliper. The angle of the incision relative to the corneal surface was then calculated. The mean corneal incision length was 1.81 mm +/- 0.27 (SD), the mean corneal thickness at the incision was 747 +/- 67 microm, and the mean distance between the incision and the scleral spur was 1.46 +/- 0.24 mm. The mean angle of the incision was 26.8 +/- 5.5 degrees. The measurements were repeatable to within +/-0.072 mm (pooled standard deviation) for the incision length, +/-11 microm for the corneal thickness, and +/-0.042 mm for the position of the incision. Optical coherence tomography allowed excellent evaluation of corneal incisions in cataract surgery postoperatively. Measurements of wound dimensions using OCT were highly repeatable.

Corneal Imaging with Anterior Segment Optical Coherence Tomography for Lamellar Keratoplasty Procedures

To assess and describe the uses of anterior segment optical coherence tomography (OCT) in the evaluation of the cornea before and after lamellar corneal transplantation procedures. Prospective, noncomparative, observational case series. Seven eyes of seven patients undergoing anterior and posterior lamellar corneal transplantation procedures at the Singapore National Eye Centre were included in the study. High-resolution anterior segment OCT scans of the cornea and anterior segment were performed both before and after lamellar transplantation procedures on the cornea with the Visante anterior segment OCT system (Visante OCT; Carl Zeiss Meditec, Inc, Dublin, California, USA), and the imaging findings were correlated with the clinical picture. Measurements of lamella thickness were performed with the software provided. Anterior segment OCT images were able to provide valuable information on donor apposition, Descemet membrane detachment after deep anterior lamellar keratoplasty (DALK), posterior lamellar dislocation, primary graft failure, and anterior chamber crowding with consequent chamber angle encroachment and pupillary block after Descemet stripping automated endothelial keratoplasty (DSAEK). Anterior segment OCT is a valuable imaging tool for assessing the feasibility of lamellar transplantation surgery in the diseased cornea and in the management of surgical complications after such procedures.

Anterior Segment Optical Coherence Tomography for Evaluation of Changes in Anterior Chamber Angle and Depth after Intraocular Lens Implantation in Eyes with Glaucoma

To examine anterior chamber depth (ACD) and anterior chamber angle (ACA) in patients with glaucoma after cataract extraction with an anterior optical coherence tomography (OCT) system. A new commercially available 1310 nm infrared light anterior segment OCT system was used for anterior chamber evaluation. Sixty patients (n=20 with primary open angle glaucoma [POAG], n=20 with angle closure glaucoma [ACG], and n=20 with no known glaucoma as control group) with a mean age of 68.8+/-13.9 years undergoing cataract surgery were enrolled. Before cataract surgery, ACD and ACA of the ACG group were significantly lower compared to the POAG and control groups (ACD p<0.005; ACA p<0.005). After cataract extraction, ACD and ACA increased significantly in the ACG group (3.1+/-0.4 mm vs 1.8+/-0.2 mm, p<0.005 and 32.3 degrees +/-7.7 degrees vs 16.0 degrees +/-4.7 degrees , p<0.005). In the POAG and control groups, ACD and ACA also increased postoperatively, but not as much as in the ACG group. After cataract extraction, IOP decreased significantly in the glaucoma groups (ACG: 15.6+/-6.1 vs 18.6+/-5.7 mm Hg, p=0.008; POAG: 16.2+/-3.4 vs 20.7+/-8.0 mmHg, p=0.02) and was almost the same in all three groups after surgery (control group after surgery: 15.2+/-2.8 mmHg). Both ACD and ACA increased significantly after cataract extraction and IOL implantation. IOP reduction after surgery was higher in the glaucoma groups compared to the control group.