Samantha Slotnick

Buried disc drusen have hypo-reflective appearance on SD-OCT.

Purpose. Buried disc drusen are an important differential diagnosis for papilledema. Spectral domain optical coherence tomography (SD-OCT) affords clinicians with new non-invasive opportunities to probe below the surface of the optic nerve. Clinicians may use the knowledge of this appearance to rule out buried disc drusen in patients with irregular optic nerve borders or a bulging, hyperemic appearance. Methods. SD-OCTs were obtained in a patient with one surfacing disc druse, identifying the nature of the appearance of this disc druse and others in this and the contralateral eye when imaged with this technology. B-scan ultrasonography was used to confirm the presence of disc drusen. Additional scans in multiple patients with confirmed buried drusen were obtained for comparison. Results. Drusen appear as rounded hyporeflectant areas on SD-OCT, similar in appearance to blood vessels. They share the appearance of cysts but show a fine hyperreflective border anteriorly. These same discrete hyporeflective areas were found at various depths within optic nerve heads with confirmed buried disc drusen. Conclusions. The hyporeflective appearance may not be anticipated by clinicians, as B-scans show calcified drusen as hyperreflective on echo. It is hypothesized that the hyporeflectant appearance of drusen is due to a constancy in refractive index through the druse, as OCT detects changes in optical reflectivity. Thus, drusen are likely dense and homogenous. SD-OCT may be more useful in those patients with buried disc drusen which are not calcified as B-scan often contributes little in such cases.

A novel retinal biomarker for Parkinson's disease: Quantifying the foveal pit with optical coherence tomography

Optical coherence tomography offers a potential biomarker tool in Parkinsons disease (PD). A mathematical model quantifying symmetry, breadth, and depth of the fovea was applied.

Discordance between structure and function in glaucoma: Possible anatomical explanations.

PURPOSE The aim of this study was to analyze glaucomatous eyes that show discordance between structure and function and hypothesize plausible anatomical explanations for discordance. METHODS Fifty eyes from 50 consecutive subjects with glaucoma (which was diagnosed according to multicenter criteria) were studied. One eye from each subject was selected randomly for inclusion, counterbalancing right eye (O.D.) and left eye (O.S.). By comparing the available structural information (from clinical disc assessment as well as GDx retinal nerve fiber layer [RNFL] measurements) to the Swedish Interactive Threshold Algorithm (SITA) Standard 24-2 (SS24-2) visual field results, study eyes were assigned to the following categories: (1) positive structure-function correlation, (2) structural abnormalities with no functional deficits, and (3) functional abnormalities with no structural deficits. Structure and function also were compared on a statistical basis, utilizing the nerve fiber indicator (NFI) of the GDx and the mean deviation (MD) and pattern standard deviation (PSD) of SS24-2 visual fields. RESULTS Forty-four eyes were classified in category 1, 5 eyes in category 2, and 1 eye in category 3. Scatter plots showing the relationship between the NFI and MD and between the NFI and PSD depict a positive correlation in the 44 category 1 eyes with R(2) values of 0.465 and 0.322, respectively. The remaining 6 eyes with discordant structural and functional findings were analyzed in detail. CONCLUSION The majority (88%) of glaucoma cases show concordance between structural loss and functional deficits. The primary proposed explanations for discordance include (1) visual field sampling and test selection limitations (i.e., the SS24-2 samples only axons that are anatomically connected to photoreceptors in the central retina, whereas the GDx samples virtually all axons) and (2) GDx measurement limitations in the papillo-macula bundle (i.e., the GDx has difficulty differentiating the normally thin RNFL from the pathologically even thinner RNFL). Tests of both structure and function are recommended in glaucoma suspects and patients, as neither mode is capable of identifying all glaucomatous deficits. Due to the apparent diagnostic benefit that the peripheral functional data may provide, we strongly recommend that future studies evaluating the structure-function relationship in glaucoma record peripheral (60-4) visual fields for all subjects at the outset of the study.

Sensitivity and specificity of the iVue iWellnessExam™ in detecting retinal and optic nerve disorders

BACKGROUND The purpose of this study was to assess the specificity and sensitivity of the iWellnessExam™ screening protocol available on iVue® spectral domain optical coherence tomography (SD-OCT), in a cohort of confirmed normal subjects and subjects with confirmed disease. METHODS In total, 126 of 132 confirmed normal subjects and 101 of 107 subjects with confirmed disease were included for analysis. Of the patients with confirmed disease, 67 had retinal disease, 50 had optic nerve disease, and 16 had both retinal and optic nerve pathology. All subjects were screened on the iWellnessExam protocol. Screen shots of the OD, OS, and OU comparison data were obtained and deidentified for reviewer analysis. Based on these data alone, each subject was sorted by a well trained eye care clinician into one of four categories (1, normal; 2, retinal disease; 3, optic nerve disease; 4, retinal and optic nerve disease). RESULTS Of the confirmed normal subjects, 125 of 126 were correctly identified as normal (specificity 99%). Retinal and/or optic nerve disease was correctly detected in 97 of 101 patients with confirmed disease (category 2, 3, 4), retinal pathology was correctly detected in 64 of 67 patients with retinal disease (category 2, 4), and optic nerve pathology was properly detected in 45 of 50 patients with optic nerve disease (category 3, 4), with a sensitivity of 96%, 95.5%, and 90%, respectively. CONCLUSION The iWellnessExam offers the health care provider an excellent method for identifying eyes at risk using very reliable technology. High specificity and sensitivity was obtained when reviewed by a well trained eye care clinician. It would be valuable to repeat the study with a novice and/or student clinician reviewing the same data set to ascertain interobserver variability, as well as the impact of clinical experience on accurate referral, based on the screening data.