High resolution in vivo imaging of the lamina cribrosa

Evaluation of lamina cribrosa parameters, nerve fiber thickness, and macular thickness in primary open-angle glaucoma and pseudoexfoliation glaucoma using optical coherence tomography

PURPOSE

To evaluate the lamina cribrosa, retinal nerve fiber layer (RNFL), and macula in patients with primary open-angle glaucoma (POAG) and pseudoexfoliation glaucoma (PEXG) and healthy individuals using enhanced depth imaging (EDI) of spectral-domain optical coherence tomography (SD-OCT).

METHODS

A total of 158 eyes were included in the study, comprising 58 eyes of 29 patients with POAG, 50 eyes of 25 patients with PEXG, and 50 eyes of 25 healthy individuals. The lamina cribrosa thickness (LCT) (at three locations), lamina cribrosa depth (LCD), RNFL thickness, and the macular thickness were measured using the EDI mode of the SD-OCT. The results were compared among the three groups.

RESULTS

In both POAG and PEXG groups, the LCT was significantly thinner in the center, mid-superior, and mid-inferior areas in both eyes than in the control group (p < 0.001). However, no statistically significant difference was observed between the POAG and PEXG groups in terms of LCT at all three measurement locations in both eyes (p > 0.05). The LCD was significantly lower in the control group compared to the POAG and PEXG groups (p < 0.05), but there was no significant difference between the POAG and PEXG groups (p > 0.05). The RNFL thickness was significantly lower in both the POAG and PEXG groups compared to the control group in both eyes (p < 0.05).

CONCLUSION

The LCT and LCD of patients with POAG and PEXG were thinner than those of healthy individuals, but there was no significant difference between the patients with POAG and PEXG.

Optimizing numerical k-sampling for swept-source optical coherence tomography angiography

High-quality swept-source optical coherence tomography (SS-OCT) requires accurate k-sampling, which is equally vital for optical coherence tomography angiography (OCTA). Most SS-OCT systems are equipped with hardware-driven k-sampling. However, this conventional approach raises concerns over system cost, optical alignment, imaging depth, and stability in the clocking circuit. This work introduces an optimized numerical k-sampling method to replace the additional k-clock hardware. Using this method, we can realize high axial resolution (4.9-µm full-width-half-maximum, in air) and low roll-off (2.3 dB loss) over a 4-mm imaging depth. The high axial resolution and sensitivity achieved by this simple numerical method can reveal anatomic and microvascular structures with structural OCT and OCTA in both macular and deeper tissues, including the lamina cribrosa, suggesting its usefulness in imaging retinopathy and optic neuropathy.

Assessment of the lamina cribrosa in attention-deficit hyperactivity disorder

PURPOSE

The aim of this study was to determine the usefulness of the lamina cribrosa thickness (LCT) and lamina cribrosa depth (LCD) in adolescence with attention-deficit hyperactivity disorder (ADHD) and compare with those receiving methylphenidate (MPH) and healthy controls.

METHODS

Fifty-five children with ADHD (9.23 ± 1.92 years, mean ± standard deviation), 41 children with ADHD given MPH (9.24 ± 1.84 years), and 86 healthy controls (9.95 ± 2.16 years) were recruited for the study. All subjects were subjected to a complete eye exam and optical coherence tomography (OCT) was used to assess LCT and LCD. The severity of ADHD symptoms was evaluated by using parent-report measures, including Conners's Parent Rating Scale-Revised: Short Form (CPRS-R: S) and the Strengths and Difficulties Questionnaire: Parent Form (SDQ: P).

RESULTS

The study showed a significant finding between the research groups with regard to LCT. LCT was shown to be significantly increased in ADHD subjects given MPH compared with the controls. However, LCD was not significantly different between cohorts. Also, a significant inverse correlation was found between the SDQ: P-Emotional Problems Subscale and LCT (r = -0.253; P = 0.030) in ADHD patients.

CONCLUSION

Changes in lamina cribrosa (LC) in ADHD children receiving MPH suggest that the mechanism of action for MPH may target developing LC structures. More studies to define the relationship between MPH medications and the LC variations are defensible.

Optical Coherence Tomography Imaging of the Lamina Cribrosa: Structural Biomarkers in Nonglaucomatous Diseases

The lamina cribrosa (LC) is an active structure that responds to the strain by changing its morphology. Abnormal changes in LC morphology are usually associated with, and indicative of, certain pathologies such as glaucoma, intraocular hypertension, and myopia. Recent developments in optical coherence tomography (OCT) have enabled detailed in vivo studies about the architectural characteristics of the LC. Structural characteristics of the LC have been widely explored in glaucoma management. However, information about which LC biomarkers could be useful for the diagnosis, and follow-up, of other diseases besides glaucoma is scarce. Hence, this literature review aims to summarize the role of the LC in nonophthalmic and ophthalmic diseases other than glaucoma. PubMed was used to perform a systematic review on the LC features that can be extracted from OCT images. All imaging features are presented and discussed in terms of their importance and applicability in clinical practice. A total of 56 studies were included in this review. Overall, LC depth (LCD) and thickness (LCT) have been the most studied features, appearing in 75% and 45% of the included studies, respectively. These biomarkers were followed by the prelaminar tissue thickness (21%), LC curvature index (5.4%), LC global shape index (3.6%), LC defects (3.6%), and LC strains/deformations (1.8%). Overall, the disease groups showed a thinner LC (smaller LCT) and a deeper ONH cup (larger LCD), with some exceptions. A large variability between approaches used to compute LC biomarkers has been observed, highlighting the importance of having automated and standardized methodologies in LC analysis. Moreover, further studies are needed to identify the pathologies where LC features have a diagnostic and/or prognostic value.

Elucidation of the role of the lamina cribrosa in glaucoma using optical coherence tomography

Glaucoma is a chronic and progressive optic neuropathy characterized by the death of retinal ganglion cells and corresponding visual field loss. Despite the growing number of studies on the subject, the pathogenesis of the disease remains unclear. Notwithstanding, several studies have shown that the lamina cribrosa (LC) is considered an anatomic site of glaucomatous optic nerve injury, thus having a key role in the pathophysiology of glaucoma development and progression. Different morphological alterations of the LC have been described in vivo in glaucomatous eyes after the evolution of optical coherence tomography (OCT) devices. The most relevant findings were the reduction of laminar thickness, the presence of localized defects, and the posterior LC displacement. These new laminar parameters documented through OCT are not only promising as possible additional tools for glaucoma diagnosis and monitoring, but also as predictors of disease progression. In spite of the advance of technology, however, proper evaluation of the LC is not yet viable in all eyes. We describe OCT-identified LC changes related to the development and progression of glaucoma and provide future directions based on a critical data analysis, focusing on its clinical relevance and applicability.

Age related changes of the central lamina cribrosa thickness, depth and prelaminar tissue in healthy Chinese subjects

AIM

To investigate the variation in the central lamina cribrosa thickness (cLCT), and the central anterior lamina cribrosa surface depth (cALCSD), as well as the central prelaminar tissue thickness (cPLTT) related to age in healthy Chinese subjects.

METHODS

A total of 96 eyes from 96 Chinese healthy subjects were recruited. According to age, the 96 cases were divided into three groups: the young group (YG, 18-39y), middle-age group (MG, 40-59y) and older-age group (OG, 60y and above). Lamina cribrosa images were obtained from all participants using radial linear protocol by enhanced depth imaging spectral-domain optical coherence tomography. The cLCT, cALCSD and cPLTT were calculated from the average value of the lamina cribrosa thickness, anterior lamina cribrosa surface depth and prelaminar tissue thickness in the optic nerve head (ONH) centre point and paracentral points (150 µm from the centre point in the horizontal and vertical directions).

RESULTS

For the total subjects, the mean cLCT, cALCSD and cPLTT were 235.18±41.27, 358.02±93.80 and 182.02±92.11 µm, respectively. No statistically significant differences in cLCT, cALCSD or cPLTT were found between gender and different eyes (P=0.27-0.92). The cLCT of the OG was the thickest among the three groups, while the cPLTT of the YG was the thickest among the three groups (P<0.05). Age was positively correlated with cLCT (r=0.42, P<0.001), and negatively correlated with cPLTT (r=-0.24, P=0.02). No significant correlation was found between the age and cALCSD (r=-0.06, P=0.55). And no correlation has been found between axial length and cLCT, cALCSD and cPLTT (P=0.11-0.81).

CONCLUSION

The impact of age on the cLCT and the cPLLTT should be taken into account when analysing glaucoma and other diseases related to lamina cribrosa.

Anatomical Characterization of an Optic Disc Notch Using SD-OCT in Glaucoma

PURPOSE

To characterize anatomical dimensions of a disc notch using novel methods using spectral domain optical coherence tomography (SD-OCT).

PARTICIPANTS

All age- and severity-matched glaucoma patients with disc notch (defined as complete loss of neural rim with no residual rim between disc and cup) seen from 2014 to 2015 who underwent enhanced depth imaging with SD-OCT (Cirrus HD-OCT version 6.5, Carl Zeiss, USA) were included for this retrospective observational study.

METHODS

Using known dimensions of the 200 * 200 optic disc cube (6 * 6 mm), the notch width was calculated from the margins of the notch on either side using ImageJ software. The height was calculated from the lowest margin of the cup to the lowest point of the defect on the optic disc. These were compared with the quadrant retinal nerve fiber layer (qRNFT) and sectoral retinal nerve fiber layer (sRNFLT) thickness in notch and the sector 2 clock hours adjacent to the notch region (SaRNFLT).

RESULTS

The height and width of the notch in 31 eyes of 27 patients were 2.6 ± 0.48 mm and 2.23 ± 0.31 mm. The RNFL thickness in the same sector as that of the notch was 41 ± 21.06 µm while the adjacent two sectors measured 62 ± 26.5 and 64 ± 26.5 µm on either sides of the sector of the notch. The difference between the sRNFLT and s_aRNFLT ranged from -9 to 67 and -13 to 50 µm, respectively. This difference was significantly associated with height of the notch (R² = 20.8, p = 0.01).

CONCLUSION

Automated analysis of a notch and RNFL thickness in that sector can help in precise glaucoma monitoring in the region of interest.

iDrugs and iDevices Discovery Research: Preclinical Assays, Techniques, and Animal Model Studies for Ocular Hypotensives and Neuroprotectants

Discovery ophthalmic research is centered around delineating the molecular and cellular basis of ocular diseases and finding and exploiting molecular and genetic pathways associated with them. From such studies it is possible to determine suitable intervention points to address the disease process and hopefully to discover therapeutics to treat them. An investigational new drug (IND) filing for a new small-molecule drug, peptide, antibody, genetic treatment, or a device with global health authorities requires a number of preclinical studies to provide necessary safety and efficacy data. Specific regulatory elements needed for such IND-enabling studies are beyond the scope of this article. However, to enhance the overall data packages for such entities and permit high-quality foundation-building publications for medical affairs, additional research and development studies are always desirable. This review aims to provide examples of some target localization/verification, ocular drug discovery processes, and mechanistic and portfolio-enhancing exploratory investigations for candidate drugs and devices for the treatment of ocular hypertension and glaucomatous optic neuropathy (neurodegeneration of retinal ganglion cells and their axons). Examples of compound screening assays, use of various technologies and techniques, deployment of animal models, and data obtained from such studies are also presented.

Optic nerve compression: the role of the lamina cribrosa and translaminar pressure

AIM

To describe the morphological changes of the lamina cribrosa (LC) in patients with optic nerve compression.

METHODS

Cross-sectional study. Twenty eyes with optic nerve compression, affected by Graves' ophthalmopathy (GO) were compared with 18 refractive error-matched healthy eyes. The following examinations were performed: best-corrected visual acuity (BCVA), intraocular pressure, optic nerve echography, visual field, SD-OCT including the retinal nerve fiber layer (RNFL), ganglion cell complex (GCC), and LC thickness and extent.

RESULTS

A-scan revealed significant differences in the subarachnoid space (SAS) between the affected and control groups. LC thickness and LC area were 233 µm (SD 23) and 0.41 mm² (SD 0.19), respectively. Average GCC thickness (P=0.0005), LC thickness (P=0.001), MD (P=0.001) and PSD (P=0.001) differed significantly between the two groups; whereas LC area (P=0.2) and average RFNL (P=0.1) did not.

CONCLUSION

Optic nerve compression reduces the SAS thereby altering the morphology of LC thickness and causing GCC damage.

Retrolaminar Migration of Intraocular Silicone Oil

BACKGROUND

Migration of intravitreal silicone to the retrolaminar optic nerve was detected pathologically in 1983, symptomatic migration to the subarachnoid space of the optic nerve was reported in 1994, and asymptomatic intraventricular silicone was first seen radiographically in 1999. Since then, little advance has been made in understanding this phenomenon despite numerous case reports. Although some authors have restricted their attention to cases of intraventricular silicone, we believe that these represent part of a clinical spectrum and that all cases with retrolaminar silicone should be considered. The pathophysiology of silicone migration may have significant implications for the management of patients after vitrectomy.

EVIDENCE ACQUISITION

Two patients were evaluated by the authors. An internet-based literature review was conducted, beginning with the key search terms "intraventricular, intracranial, subarachnoid, or optic nerve silicone," and "complications of vitrectomy or intravitreal silicone." Further searches cascaded from the initial search results. An additional 24 cases of retrolaminar migration of silicone oil were found and summarized. The relevant anatomy and pathophysiology were reviewed, with attention to additional information from enucleation studies, as well as to gaps in the current understanding of this process.

RESULTS

Retrolaminar migration of silicone oil may be more common than previously thought, especially in at-risk patient groups, and may be associated with visual and neurologic symptoms. Some impressions regarding the cause and significance of this syndrome seem incorrect. Although this process is likely linked to postoperative elevations of intraocular pressure, the exact mechanisms of silicone entry into the subarachnoid space remain undefined. A number of anatomic factors may influence the movement of silicone from the orbit and in the various compartments of the subarachnoid space and ventricular system, resulting in variability of clinical presentations and radiologic findings. Implications for clinical decision making and directions for further research are discussed.

CONCLUSION

Greater awareness on the part of treating physicians, systematic study of at-risk populations, and advances in imaging technology will allow further insight into this phenomenon.

Anterior lamina cribrosa surface depth in healthy Saudi females

Purpose

This study was conducted to determine normative profile of anterior lamina cribrosa surface depth (ALCSD) in healthy Saudi females using Topcon Three-Dimensional (3D) Optical Coherence Tomography (OCT) 2000 – Spectral Domain (SD-OCT). In addition, the correlation between ALCSD and other clinical factors such as age, refractive error, intraocular pressure (IOP), central corneal thickness, anterior chamber depth, axial length, retinal nerve fiber layer thickness, and disk area was also assessed.

Design

This study was a prospective, nonrandomized, cross-sectional, observational, and quantitative study.

Methods

This study included 191 eyes of 191 healthy Saudi females from the College of Applied Medical Sciences of King Saud University. Stereoscopic disk photographs were reconstructed using Topcon 3D OCT-2000 for all subjects. ALCSD was measured at three planes (superior, middle, and inferior) and defined as the distance from Bruch’s membrane opening level (reference line) to anterior lamina cribrosa surface. Average of ALCSD at all planes was defined as mean ALCSD of the eye. Correlation between ALCSD and all the clinical factors was performed by linear regression analysis. Paired t-test was performed in order to compare ALCSD at all planes.

Results

In this study, the average ALCSD was 371.88±114.62 μm (range, 155–647.6 μm). Paired t-test showed a significant difference between superior and middle planes (P=0.004) and middle and inferior planes (P=0.013). Using the same test, no significant difference between superior and inferior planes (P=0.820) was observed. Generally, the largest ALCSD was in the middle plane. In addition, linear regression analysis showed no significant correlation between ALCSD and associated clinical factors.

Conclusion

This work is the first to provide the normative profile of ALCSD in Saudi females using Topcon 3D OCT-2000. Further studies are recommended for males, different ethnic populations, high myopic eyes, and different age groups using advanced imaging techniques such as enhanced depth imaging OCT.

Enhanced Depth Imaging of Central Laminar Thickness in Optic Neuropathy: Comparison with Normal Eyes

The purpose of this study was to compare central laminar thickness (LT) among patients with glaucomatous optic neuropathy (GON), patients with non-GON, and normal subjects using enhanced-depth imaging optical coherence tomography (EDI-OCT). Enrolled were 57 patients (n = 64 eyes), including 30 women and 27 men. Three groups were identified: GON (n = 18 eyes), non-GON (n = 16 eyes), and control (n = 30 eyes). The GON group comprised eyes with primary open-angle glaucoma (POAG) (n = 9) and normal-tension glaucoma (NTG) (n = 9). The non-GON group comprised eyes with demyelinating optic neuritis (n = 9), anterior ischemic optic neuropathy (AION) (n = 2), compressive ON (n = 2), Leber hereditary ON (n = 2), and traumatic ON (n = 1). GON and non-GON groups were further divided into mild, moderate, and severe subgroups. Inclusion in the GON group was based on mean deviations (MDs) of visual fields; inclusion in the non-GON group was based on critical flicker frequency (CFF) responses. Intraclass correlation coefficients (ICCs) were used to verify reproducibility of measurements. LTs of GON and non-GON group eyes were thinner than those of control group eyes (p < 0.01); LTs of GON group eyes were thinner than those of non-GON group eyes (p = 0.01). LTs of severe GON subgroup eyes were thinner than those of moderate and mild GON subgroup eyes (p < 0.001; p = 0.024, respectively). LTs of severe non-GON subgroup eyes were thinner than those of mild non-GON subgroup eyes (p = 0.002). These results show that EDI-OCT is valuable for documenting structural abnormalities in optic neuropathy (ON).