High-resolution Anterior Segment Optical Coherence Tomography Research Articles

Association of Changes in Thickness of Limbal Epithelial and Stroma with Corneal Scars Detected by High-Resolution Anterior Segment Optic Coherence Tomography.

To investigate the corneal central and limbal thickness in cornea scar patients using high-resolution anterior segment optical coherence tomography (AS-OCT) and to determine the changes in the limbal region due to the corneal scar. Also, to evaluate tear film parameters in scar patients. Thirty patients with central corneal scar and 30control subjects. The control subjects were healthy individuals who came to our clinic for routine ophthalmological examination. They were enrolled in this matched case-control study. Central epithelial thickness (ET), stromal thickness (ST), limbal epithelial thickness (LET), and limbal stromal thickness (LST) were analyzed using high-resolution AS-OCT. For evaluation of the ocular surface, the following techniques were used: tear break-up time (BUT) employing standard sterile strips of fluorescein sodium, Schirmer test-I (SCH), and the Ocular Surface Disease Index (OSDI) Questionnaire. The mean central ET of the patient group was 51.5 ± 12.4 µm, while the mean central ET of the control group was 59.2 ± 9.0 µm. There was a statistically significant difference between patients and controls (p = 0.008). The mean LST of the patients was 747.9 ± 115.7 µm, and the mean LST of the controls was 726.3 ± 79.7 µm. There was a statistically significant difference between patients and controls according to BUT (p = 0.009) and SCH (p = 0.04). However, there was no significant difference between OSDI results of patients and controls (p = 0.08). Corneal monitoring with high-resolution AS-OCT is a simple, noninvasive, useful technique for corneal scar patients. Cornea scars cause decreased ET. This result could be associated with lower tear film parameters in scar patients. The scar length is associated with higher intraocular pressure (IOP) values. Decreased LET and increased LST were detected in scar patients.

Late capsular blockage syndrome: Clinical and anterior segment optical coherence tomography characteristics.

Late capsular blockage syndrome (CBS) is a rare phenomenon which is found after cataract surgery. The mechanism, anterior segment optical coherence tomography (OCT) presentation, and clinical characteristics are not well studied. We studied patients who developed late CBS in Taipei Veterans General Hospital from 2012 to 2019. Age, sex, systemic disease, ocular disease, interval between cataract surgery and CBS, axial length, type of intraocular lens implanted, grading of posterior capsular opacity, refraction, visual acuity, and anterior segment OCT findings were documented. Patients are categorized into two groups according to anterior segment OCT findings. All patients underwent Nd:YAG laser capsulotomy and were prescribed a low-dose topical steroid for 7 days. Postcapsulotomy refraction and visual acuity were recorded. All the clinical data were compared in the two groups. This study included 18 eyes with late CBS. Patients' median age was 80 (range, 54-92) years. The mean duration between cataract surgery and CBS diagnosis was 80.28 (range 15-136) months. According to anterior segment OCT findings, we subcategorized the patients into two groups: gravel appearance (n = 7) and milky (n = 11) appearance. After laser capsulotomy, mean visual acuity improved 0.18 ± 0.10 on the LogMAR. A significant myopic shift in refraction after laser capsulotomy was noted in the gravel appearance group compared to the milky appearance group ( p = 0.027). No patient developed complications or needed further treatment for CBS during the median follow-up of 14.5 months (range 1-84 months). High-resolution anterior segment OCT is useful for analyzing patients with late CBS. Our study implies that the two types of CBS presentation indicate different causes of late CBS formation, as well as distinct clinical presentation and postlaser capsulotomy refractive outcome. In addition, YAG laser capsulotomy is a safe late CBS treatment modality.

Long term outcome of Tenon's patch graft in corneal perforation secondary to neurotrophic keratitis: A case report on a 4-year anatomical functional outcome.

IntroductionThis report describes the long-term outcomes of Tenon’s patch graft (TPG) in a corneal perforation secondary to neurotrophic keratitis and outcome of subsequent successful cataract surgery.Presentation of the caseA 60-year gentleman presented with a corneal perforation secondary to Herpes Zoster ophthalmicus (HZO). After multiple unsuccessful attempts of cyanoacrylate tissue adhesive application over the perforation, he was referred for a corneal patch graft. Following TPG, he had a tectonically stable cornea that was managed with topical steroids and prophylactic oral Acyclovir. Sequential imaging of the cornea using high-resolution anterior segment- optical coherence tomography (HR-ASOCT) was done to monitor wound healing. Fifteen months later, he underwent uneventful cataract surgery with best-corrected visual acuity improving to 20/30 at 1-month.DiscussionSerial imaging of the site of perforation with HR-ASOCT revealed that a fluffy, oedematous TPG in the early postoperative period transitioned into a hyper-reflective, thin, and compact graft over 3-4 months. Despite the corneal thickness at the site of perforation being only 142 μm, the wound had adequate tensile strength to withstand the altered anterior chamber dynamics during phacoemulsification. The resultant translucent nature of the scar provided superior media clarity and better visual outcomes.ConclusionThis case demonstrates the efficacy of TPG in acute phase management of corneal perforation following HZO thereby restoring the tensile strength of the cornea, enabling it to withstand the stress of future surgeries like phacoemulsification.

The role of imaging technologies for ocular surface tumors.

This review will discuss the utility of high-resolution anterior segment optical coherence tomography (HR-OCT), in-vivo confocal microscopy (IVCM) and ultrasound biomicroscopy (UBM) in characterizing and diagnosing various ocular surface tumors, namely ocular surface squamous neoplasia (OSSN), conjunctival lymphoma and conjunctival melanoma. The strengths and limitations of each imaging modality will be discussed along with the characteristics findings of each lesion on each imaging platform. HR-OCT can consistently be utilized in the clinic setting to distinguish between epithelial ocular surface tumors such as OSSN as compared with subepithelial tumors such as conjunctival lymphoma and conjunctival melanoma given their distinctive findings. IVCM can be used as an adjunct to HR-OCT to obtain cellular and surface characteristics, whereas UBM can be used to assess tumor depth and thickness for larger and highly pigmented lesions as well as to detect intraocular invasion. HR-OCT, IVCM and UBM are all helpful imaging modalities to diagnose and characterize various ocular surface tumors and can serve as valuable adjuncts to monitor treatment response and assess for recurrence ocular surface tumors.

Mechanism of fluid leak in non-traumatic corneal perforations: an anterior segment optical coherence tomography study

AimNon-traumatic corneal perforations (CPerfs) may present with shallow/flat or formed anterior chamber (AC). This study uses anterior segment optical coherence tomography (ASOCT) to ascertain these differences.MethodThe study included 14 eyes...

The use of high resolution anterior segment optical coherence tomography for the characterization of conjunctival lymphoma, conjunctival amyloidosis and benign reactive lymphoid hyperplasia

BackgroundConjunctival lymphoma, conjunctival amyloidosis and benign reactive lymphoid hyperplasia (BRLH) are conditions that often have a similar appearance on the ocular surface. The use of high resolution anterior segment optical coherence tomography (HR-OCT) enables clinicians to evaluate distinctive differences in tissue morphology and cellular patterns in various ocular surface conditions. In this study, we characterize the morphological differences seen in conjunctival lymphoma, conjunctival amyloidosis and BRLH on HR-OCT imaging.MethodsA retrospective chart review was performed of patients with biopsy proven conjunctival lymphoma, conjunctival amyloidosis and BRLH between 2012 and 2019 at the Bascom Palmer Eye Institute. Patients were excluded if HR-OCT imaging was not performed on initial presentation.ResultsThirty-four total eyes of 27 patients were identified. Twenty eyes had conjunctival lymphoma (16 patients), 8 eyes had conjunctival amyloidosis (6 patients) and 6 eyes had BRLH (5 patients). All conditions appeared clinically as pink, red or yellow subepithelial lesions but had different features on HR-OCT. In lymphoma, HR-OCT images typically showed homogenous, dark subepithelial lesions with smooth borders, containing monomorphic dot-like infiltrates. HR-OCT images of amyloidosis typically showed heterogeneous, dark lesions with irregular borders, often containing hyperreflective linear infiltrates. HR-OCT images of BRLH showed variable infiltration of the subepithelial tissue, at times with homogenous lesions containing dot-like infiltrates like lymphoma and other times with more hyperreflective, subepithelial tissue. Flow cytometry and gene rearrangement was needed for final differentiation between BRLH and lymphoma lesions.ConclusionsDistinctive features on HR-OCT of conjunctival lymphoma, conjunctival amyloidosis and BRLH can help characterize these lesions beyond what is apparent with the clinical examination. Future studies can further validate this technology’s use with more subtle and challenging lesions.

Ability of novice clinicians to interpret high-resolution optical coherence tomography for ocular surface lesions

ObjectiveTo assess the ability of novice clinicians to use a commercially available high-resolution anterior segment optical coherence tomography (HR-OCT) device to diagnose various lesions of the ocular surface and cornea. MethodsCross-sectional study. Twenty-six black-and-white HR-OCT images were projected, and clinicians were asked to determine whether the lesions represented ocular surface squamous neoplasia (OSSN) or another ocular surface pathology. A 20-minute instructional lecture was given on HR-OCT interpretation, and the same 26 images were shown. The clinicians were asked to repeat their assessment of the lesions. Thirty-four novice clinicians at the Bascom Palmer Eye Institute, Miami, FL, participated. A commercially available device (RTVue, Optovue, Fremont, Calif.) was specifically chosen for this study. ResultsThe mean frequency of correct identification of the 26 lesions was 70% (standard deviation [SD] 15%) before instruction; after a short lecture, the frequency of correct identification improved to 84% (SD 9%, p = 0.002). Novice clinicians were more accurate in correctly determining that a lesion was not an OSSN (ruling it out as a diagnosis) than in determining that a lesion was an OSSN (p = 0.001). Some lesions (both OSSN and not OSSN), however, were more difficult to interpret than others. ConclusionThis study demonstrated that all levels of novice clinicians can quickly improve diagnostic accuracy with a commercially available HR-OCT after a short training session.

Morphometric characterisation of pterygium associated with corneal stromal scarring using high-resolution anterior segment optical coherence tomography

AimsTo investigate the role of high-resolution anterior segment optical coherence tomography (HR-ASOCT) in the assessment of pterygia.MethodsSingle centre cross-sectional study. Patients with primary pterygium and/or pingueculae were included. Clinical assessment...

Epithelial Downgrowth After Penetrating Keratoplasty

To report the clinical utility of high-resolution anterior segment optical coherence tomography (AS-OCT) combined with in vivo confocal microscopy (IVCM) to diagnose and follow the effectiveness of treatment of 2 cases of epithelial downgrowth after penetrating keratoplasty. A retrospective case review was performed on 2 eyes of 2 patients with a history of multiple penetrating keratoplasties that developed epithelial downgrowth 4 and 6 months after the most recent penetrating graft. At various time points, high-resolution AS-OCT images were obtained using the Spectralis (Heidelberg Engineering GmbH), and IVCM images were obtained using the Heidelberg Retina Tomograph III Rostock Cornea Module (Heidelberg Engineering GmbH). In 1 case, the diagnosis was confirmed by histopathologic evaluation. Two patients developed epithelial downgrowth after penetrating keratoplasty. In case 1, a 48-year-old man with a history of Acanthamoeba keratitis developed epithelial downgrowth after undergoing 2 therapeutic grafts over a 1-year period. In case 2, a 40-year-old man with a history of a corneal laceration complicated by fungal keratitis was diagnosed with epithelial downgrowth after undergoing 3 penetrating grafts, the placement of a glaucoma drainage device, and a pars plana vitrectomy over a 3-year period. In both cases, at the level of the endothelium, AS-OCT identified a highly reflective layer and IVCM revealed round hyperreflective nuclei consistent with epithelium. Epithelial downgrowth is an uncommon complication after penetrating keratoplasty. High-resolution AS-OCT and IVCM are noninvasive imaging modalities that may potentially be more sensitive in identifying and monitoring epithelial downgrowth than routine light biomicroscopy and may obviate the need for invasive diagnostic measures.

High-Resolution Spectral Domain Anterior Segment Optical Coherence Tomography in Type 1 Boston Keratoprosthesis

To report the results of imaging using high-resolution, Fourier domain anterior segment optical coherence tomography (AS-OCT) to evaluate patients with a type 1 Boston Keratoprosthesis (KPro). We performed a retrospective comparative study of patients in whom we implanted the Boston KPro. A total of 26 eyes of 23 patients from the Cornea Service at the University of California Davis Eye Center were included. Subjects were evaluated with the Spectralis AS-OCT (Heidelberg Engineering GmbH). Preoperative diagnoses for KPro surgery included failed corneal transplant (69%), chemical burn (23%), and aniridia (8%). The average age of patients was 63.2 years (range, 17-88 years). Fifty-four percent of the patients were female. The mean duration between the KPro surgery and the acquisition of high-resolution AS-OCT imaging was 35.8 months (range, 2-90 months). The most commonly observed finding was retroprosthetic membrane formation, which we found in 77% of KPro eyes. In 65% of KPro eyes, we identified epithelium behind the front plate, and in 54%, we identified an epithelial lip over the anterior surface of the KPro front plate. In 31% of KPro eyes, we identified periprosthetic cysts, gaps or spaces, and thinning in the corneal carrier graft. Fourier domain AS-OCT is a useful noninvasive imaging technique in patients with a KPro and provides the ability to identify changes that are sometimes difficult to appreciate by clinical evaluation. The higher resolution Fourier domain systems may aid in the clinical diagnosis and management of pathology that might not be imaged with instruments of lower resolution. AS-OCT has the potential for monitoring the anatomic stability of an implanted KPro and may also help to monitor for complications. Moreover, high-resolution imaging may enhance our understanding of periprosthetic anatomy.

The complementary benefit of anterior segment optical coherence tomography in penetrating keratoplasty

PurposeTo evaluate the utility of anterior segment optical coherence tomography (AS-OCT) assessment in the pre- and postsurgical management of full-thickness corneal grafts.MethodsSeventy eyes of 58 patients who had penetrating keratoplasty were included in the study. High resolution AS-OCT scans of the cornea and the anterior segment were performed before and after transplantation in 17 eyes with the Visante™ optical coherence tomography. Fifty-three eyes were examined in the late postoperative period.ResultsThe mean follow-up was 4.3 years (range, 1–15 years). Six different graft–host junctions were identified. Three patients with graft rejection, four patients with anterior synechia, and three patients with corneal ulcer were evaluated. Preoperative evaluation of eyes with semiopaque and totally opaque corneas revealed important information about anterior segment structures additional to slit-lamp findings.ConclusionAS-OCT is a useful complementary tool for the evaluation of penetrating corneal transplantation surgery and in the management of its postoperative complications.

Assessment of Intrastromal Corneal Ring Segment Position With Anterior Segment Optical Coherence Tomography

To examine the exact position of implanted Keraring (Mediphacos, Belo Horizonte, Brazil) segments by high-resolution anterior segment optical coherence tomography (AS-OCT). This study included 17 eyes of 13 patients with keratoconus who underwent uneventful intracorneal ring segment implantation with the aid of femtosecond laser. Eyes were evaluated by AS-OCT at the third postoperative month. Distance from the apex of the triangular cross-section of the ring segment to the anterior corneal surface and distances from two basal corners to the posterior corneal surface were measured. Distance from apex to anterior corneal surface (263.1 ± 42.9 μm) was significantly smaller than target depth calculated intraoperatively (356.9 ± 35.7 μm, P < .001). Distance between outer basal corner and posterior corneal surface was significantly greater than distance between inner basal corner and posterior corneal surface. High-resolution AS-OCT is a rapid, convenient, and valuable technique in the follow-up of patients with implanted Keraring segments that may be helpful in predicting ring-related complications.

Tomography-Based Customized IOL Calculation Model

Purpose: To provide a mathematical calculation scheme for customized intraocular lens (IOL) design based on high resolution anterior segment optical coherence tomography (AS-OCT) of anterior eye segment and axial length data.Material and Methods: We use the corneal and anterior segment data from the high resolution AS-OCT and the axial length data from the IOLMaster to create a pseudophakic eye model. An inverse calculation algorithm for the IOL back surface optimization is introduced. We employ free form surface representation (bi-cubic spline) for the corneal and IOL surface. The merit of this strategy is demonstrated by comparing with a standard spherical model and quadratic function. Four models are calculated: (1) quadratic cornea + quadratic IOL; (2) spline cornea + quadratic IOL; (3) spline cornea + spline IOL; and (4) spherical cornea + spherical IOL. The IOL optimization process for the pseudophakic eye is performed by numerical ray-tracing method within a 6-mm zone. The spot diagram on the fovea (forward ray-tracing) and wavefront at the spectacle plane (backward ray-tracing) are compared for different models respectively.Results: The models with quadratic (1) or spline (3) surface representation showed superior image performance than the spherical model 4. The residual wavefront errors (peak to valley) of models 1, 2, and 3 are below one micron scale. Model 4 showed max wavefront error of about 15 µm peak to valley. However, the combination of quadratic best fit IOL with the free form cornea (model 2) showed one magnitude smaller wavefront error than the spherical representation of both surfaces (model 3). This results from higher order terms in cornea height profile.Conclusions: A four-surface eye model using a numerical ray-tracing method is proposed for customized IOL calculation. High resolution OCT data can be used as a sufficient base for a customized IOL characterization.

In Vivo Quantification of Bacterial Keratitis with Optical Coherence Tomography

To quantify the human corneal inflammatory response in treated bacterial keratitis with long-wavelength anterior segment optical coherence tomography (AS-OCT). Patients with clinically suspected bacterial keratitis were recruited from the corneal service at Southampton Eye Unit, UK. Patients underwent AS-OCT and slit-lamp examination on presentation (day 0) and days 3, 7, and 14 of treatment. Corneal thickness (CT) in the infiltrated area, infiltrate thickness (IT), and infiltrate width (IW) were measured on high-resolution AS-OCT scans. Mean values for each day and rates of change for each interval were calculated and compared (one-way ANOVA, paired t-test). Twenty-six eyes of 26 patients were recruited. Mean CT and IT on presentation were 905 μm and 388 μm, respectively. On days 3, 7, and 14, CT and IT decreased to 753 μm and 320 μm (P < 0.01), 678 μm and 296 μm (P < 0.01), and 584 μm and 207 μm (P < 0.01), respectively. Mean IW, 1498 μm on presentation, did not change during treatment (P > 0.30). Mean daily rate of CT reduction was faster in the early (days 0-3) compared to late (days 7-14) phase (4.49% vs. 1.33%, P = 0.006). Mean daily rate of IT reduction was no different in early, middle, and late phases (5.41% vs. 1.19% vs. 3.38%, P > 0.01). In the late phase, IT decreased faster than CT (3.38% vs. 1.33%, P = 0.003). CT and IT decreased significantly by day 3 in resolving bacterial keratitis. The rapid early phase reduction in IT and CT was followed by rapid late phase IT reduction. This study demonstrates that serial AS-OCT examination can be used to monitor in vivo the clinical course of inflammatory disease.

Anterior Segment Optical Coherence Tomography Findings of Acute Hydrops in a Patient with Keratoconus

The authors describe the anterior segment optical coherence tomography (AS-OCT) findings of a 25-year-old patient with acute hydrops associated with keratoconus. The patient presented with decreased visual acuity, pain, and redness in the left eye. The symptoms, clinical presentation, and topographical findings of the right eye confirmed this condition to be acute corneal hydrops. The patient was closely followed up with hyper-osmotic (NaCl 5%) and nonsteroidal anti-inflammatory (ketorolac tromethamine 0.5%) topical treatment. At the initial examination and during follow-up, the evaluation of the anterior segment was performed using optical coherence tomography. Changes in the stroma and Descemet's membrane during the healing process of acute hydrops could be demonstrated by high-resolution AS-OCT.

Anterior Segment Optical Coherence Tomography Findings of Acute Hydrops in a Patient With Keratoconus

In this case report, the anterior segment optical coherence tomography (AS-OCT) findings of a 25-year-old patient with acute hydrops associated with keratoconus are described. The patient presented to our ophthalmology department in Turkey with decreased visual acuity, pain, and redness in the left eye. The symptoms, clinical presentation, and topographical findings of the right eye confirmed this condition to be acute corneal hydrops. The patient was closely observed with hyper-osmotic (NaCl 5%) and non-steroidal anti-inflammatory (ketorolac tromethamine 0.5%) topical treatment. At the initial examination and during follow-up, the evaluation of the anterior segment was performed using optical coherence tomography (Visante OCT; Carl Zeiss Meditec, Inc., Dublin, CA). By high-resolution AS-OCT, the changes in the stroma and Descemet's membrane during the healing process of acute hydrops were demonstrated.