Faculty Bibliography

The lamina cribrosa (LC) is a sieve-like structure in the sclera where retinal ganglion cell axons exit from the eye. The LC has been known to play a critical role in the pathogenesis of glaucoma. With the advent of imaging technologies, such as enhanced depth imaging, spectral-domain optical coherence tomography (OCT) enables us to unveil the LC in vivo features. The application of adaptive optics technology and a compensatory image-processing algorithm has further improved the visualization of the beams and pores and neural pathways of the LC and the scleral insertion sites. Monitoring the changes of these structures in relation to acute and chronic elevation of intraocular pressure would be germane to decipher the relationship between the stress and strain response of the LC and optic nerve damage and improve our understanding of glaucoma pathophysiology. While the impact of investigating the integrity of LC is substantive, considerable challenges remain for imaging the LC. Nevertheless, with the rapid development of the OCT technology, it is expected that some of these limitations can be overcome and the potentials of LC imaging will be unraveled.

Primary open-angle glaucoma (POAG) is a common disease with complex inheritance. The identification of genes predisposing to POAG is an important step toward the development of novel gene-based methods of diagnosis and treatment. Genome-wide association studies (GWAS) have successfully identified genes contributing to complex traits such as POAG however, such studies frequently require very large sample sizes, and thus, collaborations and consortia have been of critical importance for the GWAS approach. In this report we describe the formation of the NEIGHBOR consortium, the harmonized case control definitions used for a POAG GWAS, the clinical features of the cases and controls, and the rationale for the GWAS study design.

PURPOSE: We developed a method to normalize optical coherence tomography (OCT) signal profiles from two spectral-domain (SD) OCT devices so that the comparability between devices increases. METHODS: We scanned 21 eyes from 14 healthy and 7 glaucoma subjects with two SD-OCT devices on the same day, with equivalent cube scan patterns centered on the fovea (Cirrus HD-OCT and RTVue). Foveola positions were selected manually and used as the center for registration of the corresponding images. A-scan signals were sampled 1.8 mm from the foveola in the temporal, superior, nasal, and inferior quadrants. After oversampling and rescaling RTVue data along the Z-axis to match the corresponding Cirrus data format, speckle noise reduction and amplitude normalization were applied. For comparison between normalized A-scan profiles, mean absolute difference in amplitude in percentage was measured at each sampling point. As a reference, the mean absolute difference between two Cirrus scans on the same eye also was measured. RESULTS: The mean residual of the A-scan profile amplitude was reduced significantly after signal normalization (12.7% vs. 6.2%, P < 0.0001, paired t-test). All four quadrants also showed statistically significant reduction (all P < 0.0001). Mean absolute difference after normalization was smaller than the one between two Cirrus scans. No performance difference was detected between health and glaucomatous eyes. CONCLUSIONS: The reported signal normalization method successfully reduced the A-scan profile differences between two SD-OCT devices. This signal normalization processing may improve the direct comparability of OCT image analysis and measurement on various devices.

PURPOSE: Ocular imaging devices provide quantitative structural information that might improve glaucoma progression detection. This study examined scanning laser polarimetry (SLP) population-derived versus individual-derived cut-off criteria for detecting progression. METHODS: Forty-eight healthy, glaucoma suspect and glaucoma subjects, providing 76 eyes were used. All subjects had reliable visual field (VF) and SLP scans acquired at the same visits from >/=4 visits. VF progression was defined by guided progression analysis (GPA) and by the VF index. SLP measurements were analysed by fast mode (FM) GPA, compared with the population rate of progression, and extended mode (EM) GPA, compared with the individual variability. The agreement between progression detection methods was measured. RESULTS: Poor agreement was observed between progression defined by VF and FM and EM. The difference in temporal-superior-nasal-inferior-temporal (TSNIT) average rate of change between VF defined progressors and non-progressors for both FM (p=0.010) and EM (p=0.015) was statistically significant. CONCLUSIONS: There is poor agreement between VF and SLP progression regardless of the use of population derived or individual variability criteria. The best SLP progression detection method could not be ascertained, therefore, acquiring three SLP scans per visit is recommended.

PURPOSE: To describe the occurrence of cystoid macular edema (CME) in the setting of central foveal thickness (CFT) under 250 mum as measured by optical coherence tomography (OCT) in patients with retinitis pigmentosa (RP). METHODS: Stratus OCT was used to measure CFT in a total of 90 eyes from 46 patients with RP. Cross-sectional OCT images were also evaluated for CME, which was defined as cystoid changes in the macula seen on at least two linear scans. RESULTS: CME was identified in 13 of the 46 patients or in 22 of 90 eyes by OCT. In eyes with macular edema, CFT ranged from 224 to 718 mum (mean = 339 +/- 137 mum). In eyes without macular edema, CFT ranged from 99 to 273 mum (mean = 184 +/- 40 mum). Bilateral CME occurred in 9 of 13 patients (69%). CFT was considered "normal" in 7 of the 22 eyes (32%) with CME. Two patients had bilateral CME with normal CFTs, under 250 mum. CONCLUSION: We demonstrate the occurrence of CME in RP patients without associated thickening, which has not been described. This concept likely is applicable to other diseases with retinal thinning.

PURPOSE: To investigate the potential of human trabecular meshwork stem cells (TMSCs) for homing to mouse TM tissue and survival in vivo. METHODS: Human TMSCs and fibroblasts were labeled with fluorescent membrane dye DiO and injected into normal mouse anterior chamber. Stem cell and TM cell markers were identified by immunofluorescent staining of cryosections or tissue whole mounts. Apoptosis was determined by TUNEL assay. Replicating and inflammatory cells were detected by bromodeoxyuridine (BrdU) incorporation and anti-CD45 staining, respectively. Quantitative RT-PCR detected gene expression of injected cells after isolation by fluorescence activated cell sorting. Intraocular pressure was measured using a TonoLab rebound tonometer. RESULTS: Expanded cultures of DiO-labeled TMSCs expressed stem cell markers preferentially in DiO positive cells, demonstrating a slow-cycling, label-retaining stem cell phenotype. DiO-labeled TMSCs injected into the anterior chamber of normal mice localized primarily in TM, remaining in the tissue at least 4 months. Within 1 week, TM-associated TMSCs began expressing TM marker protein CHI3L1. Fibroblasts injected in mouse anterior chamber showed distributed localization in corneal endothelium, lens epithelium, and TM and did not express CHI3L1. Little apoptosis was detected in injected TM tissue and intraocular pressure was not elevated during the experiment. Dividing cells or CD45-staining cells were not detected after TMSC-injection. CONCLUSIONS: Stem cells isolated from human TM and expanded in vitro exhibit the ability to home to the TM and differentiate into TM cells in vivo. Such cells present a potential for development of a novel cell-based therapy for glaucoma.

PURPOSE: To assess the association between single nucleotide polymorphisms (SNPs) of the gene region containing cyclin-dependent kinase inhibitor 2B antisense noncoding RNA (CDKN2B-AS1) and glaucoma features among primary open-angle glaucoma (POAG) patients. DESIGN: Retrospective observational case series. METHODS: We studied associations between 10 CDKN2B-AS1 SNPs and glaucoma features among 976 POAG cases from the Glaucoma Genes and Environment (GLAUGEN) study and 1971 cases from the National Eye Institute Glaucoma Human Genetics Collaboration (NEIGHBOR) consortium. For each patient, we chose the feature from the eye with the higher value. We created cohort-specific multivariable models for glaucoma features and then meta-analyzed the results. RESULTS: For 9 of the 10 protective CDKN2B-AS1 SNPs with minor alleles associated with reduced disease risk (eg, the G allele at rs2157719), POAG patients carrying these minor alleles had smaller cup-to-disc ratio (0.05 units smaller per G allele at diagnosis; 95% CI: -0.08, -0.03; P = 6.23E-05) despite having higher intraocular pressure (IOP) (0.70 mm Hg higher per G allele at DNA collection; 95% CI: 0.40, 1.00; P = 5.45E-06). For the 1 adverse rs3217992 SNP with minor allele A associated with increased disease risk, POAG patients with A alleles had larger cup-to-disc ratio (0.05 units larger per A allele at diagnosis; 95% CI: 0.02, 0.07; P = 4.74E-04) despite having lower IOP (-0.57 mm Hg per A allele at DNA collection; 95% CI: -0.84, -0.29; P = 6.55E-05). CONCLUSION: Alleles of CDKN2B-AS1 SNPs, which influence risk of developing POAG, also modulate optic nerve degeneration among POAG patients, underscoring the role of CDKN2B-AS1 in POAG.

PURPOSE: To develop and test a novel signal enhancement method for optical coherence tomography (OCT) images based on the high dynamic range (HDR) imaging concept. METHODS: Three virtual channels, which represent low, medium, and high signal components, were produced for each OCT signal dataset. The dynamic range of each signal component was normalized to the full gray scale range. Finally, the three components were recombined into one image using various weights. Fourteen eyes of 14 healthy volunteers were scanned multiple times using time-domain (TD)-OCT before and while preventing blinking in order to produce a wide variety of signal strength (SS) images on the same eye scanned on the same day. For each eye, a pair of scans with the highest and lowest SS with successful retinal nerve fiber layer (RNFL) segmentation was selected to test the signal enhancement effect. In addition, spectral-domain (SD)-OCT images with poor signal qualities were also processed. RESULTS: Mean SS of good and poor quality scans were 9.0 +/- 1.1 and 4.4 +/- 0.9, respectively. TD-OCT RNFL thickness showed significant differences between good and poor quality scans on the same eye (mean difference 11.9 +/- 6.0 mum, P < 0.0001, paired t-test), while there was no significant difference after signal enhancement (1.7 +/- 6.2 mum, P = 0.33). However, HDR had weaker RNFL compensation effect on images with SS less than or equal to 4, while it maintained good compensation effect on images with SS greater than 4. Successful signal enhancement was also confirmed subjectively on SD-OCT images. CONCLUSION: The HDR imaging successfully restored OCT signal and image quality and reduced RNFL thickness differences due to variable signal level to the level within the expected measurement variability. This technique can be applied to both TD- and SD-OCT images.