Amir Marvasti

The Relationship between Visual Field Index and Estimated Number of Retinal Ganglion Cells in Glaucoma

Purpose To evaluate the relationship between visual field index (VFI) and the estimated number of retinal ganglion cells (RGCs) in glaucoma. Methods A multicenter study of 1,245 healthy, glaucomatous and suspected glaucomatous eyes of 1,245 subjects recruited from the Diagnostic Innovations in Glaucoma Study (DIGS) and African Descent and Glaucoma Evaluation Study (ADAGES). All eyes underwent standard automated perimetry (SAP) and time-domain optical coherence tomography (TD-OCT). Estimates of RGC count and percentage of RGCs remaining, compared to age-matched healthy eyes, were calculated from TD-OCT using a previously described formula. Smoothing spline curves were fitted to examine the relationship between VFI and the percent remaining RGCs. The first derivative (i.e., slopes) of these curves was used to explore the relationship between changes in these measures. Results The relationships between the VFI and both estimated RGC counts and the percent remaining RGCs were nonlinear. A unit number of VFI loss corresponded to substantially greater loss of estimated RGCs and estimated percentage of RGCs remaining in early compared to late disease. Conclusions The relationship between VFI and estimated RGC counts is nonlinear and the index substantially underestimates the amount of neural loss early in the disease. Disease severity should be taken into account when interpreting rates of VFI change over time.

The Relative Odds of Progressing by Structural and Functional Tests in Glaucoma.

Purpose The purpose of this study was to evaluate the effect of disease severity and number of tests acquired during follow-up on the relative odds of identifying progression by structural or functional tests in glaucoma. Methods This was an observational cohort study involving 462 eyes of 305 patients with glaucoma and 62 eyes of 49 healthy subjects. Glaucoma patients and healthy subjects were followed for an average of 3.6 ± 0.9 and 3.8 ± 0.9 years, with a median (interquantile range) of 8 (6–9) and 7 (6–8) visits, respectively. At each visit, subjects underwent visual field assessment with standard automated perimetry (SAP) and retinal nerve fiber layer (RNFL) evaluation by spectral-domain optical coherence tomography (SD-OCT). Slopes of change in SAP mean sensitivity and OCT RNFL thickness over time were estimated by linear regression using progressively cumulative visits over time. Cutoff values for age-related expected rates of change for each test were obtained from the healthy group. Progression by SD-OCT and/or SAP was determined if the slope of change was statistically significant and also lower (faster) than the fifth percentile cutoff calculated from the healthy group. A generalized estimating equation logistic regression model was used to evaluate the relative odds of progressing by OCT versus SAP in glaucoma eyes. Results Eyes with less severe disease at baseline had a higher chance of being detected as progressing by SD-OCT but not by SAP, whereas an increase in disease severity at baseline increased the chance that the eye would be detected as progressing by SAP but not SD-OCT. Each 1 dB higher MD was associated with a 5% increase in the odds of detecting progression by SD-OCT versus SAP (odds ratio = 1.05 per 1 dB; 95% confidence interval: 1.01–1.09; P = 0.005). Conclusions The ability to detect glaucoma progression by SAP versus SD-OCT is significantly influenced by the stage of disease. Our results may provide useful information for guiding clinicians on the relative utility of these tests for detecting change throughout the disease continuum.

REAL-TIME FULL-DEPTH VISUALIZATION OF POSTERIOR OCULAR STRUCTURES: Comparison Between Full-Depth Imaging Spectral Domain Optical Coherence Tomography and Swept-Source Optical Coherence Tomography.

Purpose: To compare the real-time visualization of vitreoretino-choroidal structures using full-depth imaging (FDI) spectral domain optical coherence tomography (SD-OCT) and swept-source (SS)-OCT. Methods: Foveal scans using both FDI SD-OCT (Heidelberg Spectralis) and SS-OCT (Topcon Deep Range Imaging-OCT-1) were obtained in 40 normal eyes, 40 eyes with macular pathologies, and 40 eyes with glaucoma. Full-depth imaging SD-OCT images were obtained by manually enhancing the vitreoretinal interface first and then the choroid while averaging each OCT B-scan 100 times. Swept-source-OCT images were obtained by averaging each B-scan 96 times. After masking and randomly mixing the original OCT images, two independent physicians graded visualization of the premacular bursa, interdigitation zone line, and chorioscleral boundary, and also sharpness of choroidal structures. Results: A real-time full-depth image of vitreoretino-choroidal structures was successfully achieved with FDI SD-OCT in 118 cases (98.3%) and with SS-OCT in 45 cases (37.5%, P < 0.001). Full-depth imaging SD-OCT imaging was superior to SS-OCT imaging in visualizing the anterior border of the premacular bursa in 109 eyes (90.8%), with average grading of 1.63 ± 0.53 for the FDI SD-OCT and 0.39 ± 0.52 for the SS-OCT (P < 0.001). Swept-source-OCT was similar to FDI SD-OCT in visualizing the chorioscleral boundary in 108 eyes (90.0%), with average grading of 1.81 ± 0.39 for the SS-OCT and 1.78 ± 0.38 for the FDI-OCT (P = 0.566). The visualization of the interdigitation zone line was identical in the 2 imaging instruments (P = 1.000). The sharpness of the choroidal structures was greater with SS-OCT than with FDI-OCT (P < 0.001). Conclusion: Manual double-enhancing FDI technique using SD-OCT provided a good compromise between vitreous and retinochoroidal structures visualization in real time during scanning procedure. In contrast, SS-OCT imaged well details of choroidal sublayers. Appropriate OCT technology and software should be selected according to its application in clinical settings.

Use of Statistical Analyses in the Ophthalmic Literature

PURPOSE To identify the most commonly used statistical analyses in the ophthalmic literature and to determine the likely gain in comprehension of the literature that readers could expect if they were to add knowledge of more advanced techniques sequentially to their statistical repertoire. DESIGN Cross-sectional study. METHODS All articles published from January 2012 through December 2012 in Ophthalmology, the American Journal of Ophthalmology, and Archives of Ophthalmology were reviewed. A total of 780 peer-reviewed articles were included. Two reviewers examined each article and assigned categories to each one depending on the type of statistical analyses used. Discrepancies between reviewers were resolved by consensus. MAIN OUTCOME MEASURES Total number and percentage of articles containing each category of statistical analysis were obtained. Additionally, we estimated the accumulated number and percentage of articles that a reader would be expected to be able to interpret depending on their statistical repertoire. RESULTS Readers with little or no statistical knowledge would be expected to be able to interpret the statistical methods presented in only 20.8% of articles. To understand more than half (51.4%) of the articles published, readers would be expected to be familiar with at least 15 different statistical methods. Knowledge of 21 categories of statistical methods was necessary to comprehend 70.9% of articles, whereas knowledge of more than 29 categories was necessary to comprehend more than 90% of articles. Articles related to retina and glaucoma subspecialties showed a tendency for using more complex analysis when compared with articles from the cornea subspecialty. CONCLUSIONS Readers of clinical journals in ophthalmology need to have substantial knowledge of statistical methodology to understand the results of studies published in the literature. The frequency of the use of complex statistical analyses also indicates that those involved in the editorial peer-review process must have sound statistical knowledge to appraise critically the articles submitted for publication. The results of this study could provide guidance to direct the statistical learning of clinical ophthalmologists, researchers, and educators involved in the design of courses for residents and medical students.

A Portable Platform for Evaluation of Visual Performance in Glaucoma Patients

Purpose To propose a new tablet-enabled test for evaluation of visual performance in glaucoma, the PERformance CEntered Portable Test (PERCEPT), and to evaluate its ability to predict history of falls and motor vehicle crashes. Design Cross-sectional study. Methods The study involved 71 patients with glaucomatous visual field defects on standard automated perimetry (SAP) and 59 control subjects. The PERCEPT was based on the concept of increasing visual task difficulty to improve detection of central visual field losses in glaucoma patients. Subjects had to perform a foveal 8-alternative-forced-choice orientation discrimination task, while detecting a simultaneously presented peripheral stimulus within a limited presentation time. Subjects also underwent testing with the Useful Field of View (UFOV) divided attention test. The ability to predict history of motor vehicle crashes and falls was investigated by odds ratios and incident-rate ratios, respectively. Results When adjusted for age, only the PERCEPT processing speed parameter showed significantly larger values in glaucoma compared to controls (difference: 243ms; P<0.001). PERCEPT results had a stronger association with history of motor vehicle crashes and falls than UFOV. Each 1 standard deviation increase in PERCEPT processing speed was associated with an odds ratio of 2.69 (P = 0.003) for predicting history of motor vehicle crashes and with an incident-rate ratio of 1.95 (P = 0.003) for predicting history of falls. Conclusion A portable platform for testing visual function was able to detect functional deficits in glaucoma, and its results were significantly associated with history of involvement in motor vehicle crashes and history of falls.

Heidelberg Edge Perimetry for the Detection of Early Glaucomatous Damage: A Case Report

Purpose: To illustrate the potential role for Heidelberg edge perimetry (HEP) in the assessment of early functional loss in glaucoma. Case Report: A 46-year-old male presented with raised intraocular pressure but healthy optic discs and normal standard automated perimetry (SAP). He was diagnosed with ocular hypertension, but after 16 years, he developed glaucomatous changes to the right optic disc and inferior retinal nerve fiber layer thinning. Despite the evidence of progressive structural damage, functional testing using SAP was repeatedly normal, based on conventional criteria. HEP, on the other hand, revealed an extensive superior visual field damage in agreement with the structural changes. Additionally, and in contrast to SAP, the HEP indices of Glaucoma Hemifield Test, mean deviation and pattern standard deviation were all outside normal limits. Conclusion: This case illustrates that HEP may have an important role in the early detection of functional damage in glaucoma, with potential advantages over SAP.

Anterior Segment Scleral Fluorescein Angiography in the Evaluation of Ciliary Body Neoplasm: Two Case Reports.

Introduction: Anterior segment tumors can be difficult to detect until tumor growth is substantial enough to cause local signs or symptoms. Earlier detection may result in improved outcomes, particularly the ability to option for globe-conserving therapy. Multiple diagnostic modalities such as ultrasound or optical coherence tomography exist to aid for earlier detection of ciliary body tumors, but they also have limitations. Here we describe the potential for scleral angiography as an adjunctive modality to assist in evaluating anterior segment ciliary body tumors. Case Presentations: A 61-year-old Caucasian male and a 57-year-old Hispanic female presented for ciliary body tumor evaluation. The Caucasian male notably had abnormal scleral, episcleral, and conjunctival vessels in the affected eye. Scleral angiography was performed in both cases with the abnormal vasculature highlighted in the Caucasian male. The Hispanic female did not demonstrate abnormal scleral angiographic patterns. Notably, the Caucasian male also had regions of abnormal scleral angiography arising in locations of otherwise normal appearing sclera. Both patients had the affected eyes enucleated. Histology of the enucleated eyes demonstrated a ciliary body melanoma in the Caucasian male associated with abnormal vascular and tumor infiltration of the scleral bed. The Hispanic female had a pigmented ciliary body adenoma without involvement of the scleral bed. Conclusion: With limited sample size, scleral angiography has the potential to detect abnormal scleral vascular patterns in otherwise normal appearing sclera in cases of ciliary body tumor with scleral vascular invasion.