ABSTRACT
PURPOSE: Foveal herniation occurs when neuroretinal tissue protrudes through and above the level of an epiretinal membrane. This study describes the visual symptoms and spectral domain optical coherence tomography findings associated with foveal herniation and evaluates the postoperative visual, anatomical, and surgical outcomes. METHODS: A multicenter retrospective review of patients diagnosed with epiretinal membrane identified 59 patients with preoperative foveal herniation on spectral domain optical coherence tomography. Data regarding visual symptoms, preoperative and postoperative best-corrected visual acuity (BCVA), central retinal thickness, macular volume, and size of foveal herniation were collected, and statistical analysis was performed. RESULTS: A total of 58 of the 59 patients with foveal herniation underwent surgical epiretinal membrane peeling, with foveal contour restored in 53.5% of patients after surgery. Average BCVA improved from 20/80 to 20/40 Snellen equivalent at most-recent postoperative visit (P < 0.0001). The average central retinal thickness decreased from 632 µm to 432 µm (P < 0.0001) and the average macular volume decreased from 11.3 mm3 to 9.5 mm3 (P < 0.0001) at 3 months postoperatively. Preoperatively, greater herniation height was associated with worse BCVA (P = 0.008), greater central retinal thickness (P = 0.01), retinoschisis, cystoid macular edema, foveolar detachment, ellipsoid zone abnormality, and external limiting membrane abnormalities (P < 0.05). Postoperatively, there was a decrease in retinoschisis, cystoid macular edema, foveolar detachment, ellipsoid zone, and external limiting membrane abnormality (P < 0.05) on spectral domain optical coherence tomography. CONCLUSION: Patients with larger foveal herniation height had greater preoperative central retinal thickness, worse preoperative and postoperative BCVA, and more intraretinal abnormalities on spectral domain optical coherence tomography. Surgical epiretinal membrane peeling in patients with foveal herniation resulted in a significant improvement in patients' BCVA and microstructural abnormalities.
Subject(s)
Epiretinal Membrane , Macular Edema , Retinoschisis , Humans , Epiretinal Membrane/diagnosis , Epiretinal Membrane/surgery , Macular Edema/diagnosis , Macular Edema/etiology , Macular Edema/surgery , Retinoschisis/surgery , Vitrectomy/methods , Tomography, Optical Coherence/methods , Retrospective Studies , Treatment OutcomeABSTRACT
PURPOSE: We have previously shown that the amplitude of the mfERG response obtained to a single (large) hexagon is significantly smaller than that obtained when summating all the mfERG responses evoked to an array of 7-61 hexagons covering the same retinal area. The purpose of this study was to confirm our initial findings in normal subjects of different ages and in selected patients. METHODS: Binocular mfERGs (1, 7, 19, 37 and 61 hexagon arrays; Espion V6.0.54 Diagnosys LLC) were recorded from 40 normal subjects (25 aged 18-25, and 15 aged 3-12). Individual mfERG waveforms evoked in response to the multi-hexagon arrays (7, 19, 37 and 61) were summated, and the amplitude of the resulting composite mfERG waveform was compared to that measured in the response evoked to the single (large) hexagon stimulus to yield the amplitude ratio (i.e., 7:1 X100, 19:1X100, etc.). RESULTS: In normal subjects, the 7:1 ratio was 119.5 ± 9.2%, a value that gradually decreased to reach 109.4 ± 20.6% with the 61:1 ratio and a finding that was similar across all ages. CONCLUSION: The present study indicates a significant enhancement in amplitude of the summed mfERG composite waveform evoked to the 7 hexagon stimulus array (and to a lesser extent to the 19, 37 and 61 stimuli) compared to the 1 hexagon array, possibly mediated through the retinal lateral pathway (horizontal or amacrine cells), a claim that awaits confirmation. Preliminary results obtained from patients treated with Plaquenil suggest that this new method of mfERG analysis might probe a feature of macular function different from that investigated with the more usual method of mfERG ring ratio.
Subject(s)
Electroretinography/drug effects , Retina/physiopathology , Adolescent , Adult , Antirheumatic Agents/adverse effects , Antirheumatic Agents/therapeutic use , Child , Child, Preschool , Female , Healthy Volunteers , Humans , Hydroxychloroquine/adverse effects , Hydroxychloroquine/therapeutic use , Lupus Erythematosus, Systemic/drug therapy , Male , Photic Stimulation , Retina/drug effects , Young AdultSubject(s)
Sclera , Sclerostomy , Humans , Microsurgery/methods , Sclera/surgery , Sclerostomy/methods , Suture Techniques , Vitrectomy/methodsABSTRACT
Retinitis pigmentosa (RP) is a devastating form of retinal degeneration, with significant social and professional consequences. Molecular genetic information is invaluable for an accurate clinical diagnosis of RP due to its high genetic and clinical heterogeneity. Using a gene capture panel that covers 163 of the currently known retinal disease genes, including 48 RP genes, we performed a comprehensive molecular screening in a collection of 123 RP unsettled probands from a wide variety of ethnic backgrounds, including 113 unrelated simplex and 10 autosomal recessive RP (arRP) cases. As a result, 61 mutations were identified in 45 probands, including 38 novel pathogenic alleles. Interestingly, we observed that phenotype and genotype were not in full agreement in 21 probands. Among them, eight probands were clinically reassessed, resulting in refinement of clinical diagnoses for six of these patients. Finally, recessive mutations in CLN3 were identified in five retinal degeneration patients, including four RP probands and one cone-rod dystrophy patient, suggesting that CLN3 is a novel non-syndromic retinal disease gene. Collectively, our results underscore that, due to the high molecular and clinical heterogeneity of RP, comprehensive screening of all retinal disease genes is effective in identifying novel pathogenic mutations and provides an opportunity to discover new genotype-phenotype correlations. Information gained from this genetic screening will directly aid in patient diagnosis, prognosis, and treatment, as well as allowing appropriate family planning and counseling.
Subject(s)
Genetic Association Studies , High-Throughput Nucleotide Sequencing , Membrane Glycoproteins/genetics , Molecular Chaperones/genetics , Retinitis Pigmentosa/diagnosis , Retinitis Pigmentosa/genetics , Alleles , Computational Biology , Exons , Genes, Recessive , Genetic Testing , Genotype , Humans , Membrane Glycoproteins/metabolism , Molecular Chaperones/metabolism , Mutation , Pedigree , Phenotype , Polymorphism, Single Nucleotide , Reproducibility of Results , Sequence Analysis, DNAABSTRACT
BACKGROUND: Leber congenital amaurosis (LCA) and juvenile retinitis pigmentosa (RP) are inherited retinal diseases that cause early onset severe visual impairment. An accurate molecular diagnosis can refine the clinical diagnosis and allow gene specific treatments. METHODS: We developed a capture panel that enriches the exonic DNA of 163 known retinal disease genes. Using this panel, we performed targeted next generation sequencing (NGS) for a large cohort of 179 unrelated and prescreened patients with the clinical diagnosis of LCA or juvenile RP. Systematic NGS data analysis, Sanger sequencing validation, and segregation analysis were utilised to identify the pathogenic mutations. Patients were revisited to examine the potential phenotypic ambiguity at the time of initial diagnosis. RESULTS: Pathogenic mutations for 72 patients (40%) were identified, including 45 novel mutations. Of these 72 patients, 58 carried mutations in known LCA or juvenile RP genes and exhibited corresponding phenotypes, while 14 carried mutations in retinal disease genes that were not consistent with their initial clinical diagnosis. We revisited patients in the latter case and found that homozygous mutations in PRPH2 can cause LCA/juvenile RP. Guided by the molecular diagnosis, we reclassified the clinical diagnosis in two patients. CONCLUSIONS: We have identified a novel gene and a large number of novel mutations that are associated with LCA/juvenile RP. Our results highlight the importance of molecular diagnosis as an integral part of clinical diagnosis.
Subject(s)
High-Throughput Nucleotide Sequencing , Leber Congenital Amaurosis/diagnosis , Retinitis Pigmentosa/diagnosis , Alleles , Amino Acid Sequence , Base Sequence , Exome , Female , Genotype , Humans , Leber Congenital Amaurosis/genetics , Mutation , Pedigree , Polymorphism, Single Nucleotide , Reproducibility of Results , Retinitis Pigmentosa/genetics , Sensitivity and SpecificityABSTRACT
Purpose: Clinical OCT angiography (OCTA) of the retinal microvasculature offers a quantitative correlate to systemic disease burden and treatment efficacy in sickle cell disease (SCD). The purpose of this study was to use the higher resolution of adaptive optics scanning light ophthalmoscopy (AOSLO) to elucidate OCTA features of parafoveal microvascular compromise identified in SCD patients. Design: Case series of 11 SCD patients and 1 unaffected control. Participants: A total of 11 eyes of 11 SCD patients (mean age, 33 years; range, 23-44; 8 female, 3 male) and 1 eye of a 34-year-old unaffected control. Methods: Ten sequential 3 × 3 mm parafoveal OCTA full vascular slab scans were obtained per eye using a commercial spectral domain OCT system (Avanti RTVue-XR; Optovue). These were used to identify areas of compromised perfusion near the foveal avascular zone (FAZ), designated as regions of interest (ROIs). Immediately thereafter, AOSLO imaging was performed on these ROIs to examine the cellular details of abnormal perfusion. Each participant was imaged at a single cross-sectional time point. Additionally, 2 of the SCD patients were imaged prospectively 2 months after initial imaging to study compromised capillary segments across time and with treatment. Main Outcome Measures: Detection and characterization of parafoveal perfusion abnormalities identified using OCTA and resolved using AOSLO imaging. Results: We found evidence of abnormal blood flow on OCTA and AOSLO imaging among all 11 SCD patients with diverse systemic and ocular histories. Adaptive optics scanning light ophthalmoscopy imaging revealed a spectrum of phenomena, including capillaries with intermittent blood flow, blood cell stasis, and sites of thrombus formation. Adaptive optics scanning light ophthalmoscopy imaging was able to resolve single sickled red blood cells, rouleaux formations, and blood cell-vessel wall interactions. OCT angiography and AOSLO imaging were sensitive enough to document improved retinal perfusion in an SCD patient 2 months after initiation of oral hydroxyurea therapy. Conclusions: Adaptive optics scanning light ophthalmoscopy imaging was able to reveal the cellular details of perfusion abnormalities detected using clinical OCTA. The synergy between these clinical and laboratory imaging modalities presents a promising avenue in the management of SCD through the development of noninvasive ocular biomarkers to prognosticate progression and measure the response to systemic treatment.
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PURPOSE: To describe a case of Epstein-Barr virus (EBV)-associated acute retinal necrosis (ARN) in an immunocompetent patient and to summarize the clinical features of published molecularly confirmed EBV-ARN cases. METHODS: Case report and literature review. RESULTS: An 83-year-old immunocompetent woman with unilateral ARN presented with visual acuity of light perception. Oral valacyclovir was started. One week later, vitrectomy was conducted for worsening inflammation. Intraoperatively, a severe confluent necrotizing retinitis and occlusive vasculitis involving all four quadrants of posterior and peripheral retina were noted. Vitreous polymerase chain reaction was exclusively positive for EBV. Other autoimmune, infective, and hematological work-up was negative. The retinitis resolved 3 months later, but with significant macular and generalized retinal atrophy, visual acuity remained light perception. From the literature, there are four EBV-ARN cases (six eyes) diagnosed based on polymerase chain reaction or fluorescence in-situ hybridization of vitreous or retinal samples. All patients were immunocompromised or on immunosuppressive treatment. Presenting visual acuity was light perception or worse in 3/6 eyes. Three patients received systemic acyclovir-based therapy. Vitrectomy was performed in 4/6 eyes between 4 and 8 weeks from disease onset. All cases had involvement of the posterior and peripheral retina. Retinal detachment occurred in 2/6 eyes, and final visual acuity was no light perception in 3/6 eyes. CONCLUSION: This case expands the clinical spectrum of EBV-ARN to include infection in immunocompetent hosts. Epstein-Barr virus-ARN seems to be characterized by a global peripheral and posterior fulminant retinitis, with adverse visual acuity outcomes despite systemic acyclovir-based therapy. The benefits of adjunctive intravitreal foscarnet, systemic steroids, and early vitrectomy may warrant further investigation.
Subject(s)
Epstein-Barr Virus Infections , Immunocompetence , Retinal Necrosis Syndrome, Acute , Acyclovir/therapeutic use , Aged, 80 and over , Antiviral Agents/therapeutic use , Epstein-Barr Virus Infections/complications , Epstein-Barr Virus Infections/drug therapy , Epstein-Barr Virus Infections/immunology , Female , Humans , Retinal Necrosis Syndrome, Acute/drug therapy , Retinal Necrosis Syndrome, Acute/immunology , Retinal Necrosis Syndrome, Acute/virologyABSTRACT
A long-standing question in the field of vision research is whether scalp-recorded EEG activity contains sufficient information to identify stimulus chromaticity. Recent multivariate work suggests that it is possible to decode which chromaticity an observer is viewing from the multielectrode pattern of EEG activity. There is debate, however, about whether the claimed effects of stimulus chromaticity on visual evoked potentials (VEPs) are instead caused by unequal stimulus luminances, which are achromatic differences. Here, we tested whether stimulus chromaticity could be decoded when potential confounds with luminance were minimized by (1) equating chromatic stimuli in luminance using heterochromatic flicker photometry for each observer and (2) independently varying the chromaticity and luminance of target stimuli, enabling us to test whether the pattern for a given chromaticity generalized across wide variations in luminance. We also tested whether luminance variations can be decoded from the topography of voltage across the scalp. In Experiment 1, we presented two chromaticities (appearing red and green) at three luminance levels during separate trials. In Experiment 2, we presented four chromaticities (appearing red, orange, yellow, and green) at two luminance levels. Using a pattern classifier and the multielectrode pattern of EEG activity, we were able to accurately decode the chromaticity and luminance level of each stimulus. Furthermore, we were able to decode stimulus chromaticity when we trained the classifier on chromaticities presented at one luminance level and tested at a different luminance level. Thus, EEG topography contains robust information regarding stimulus chromaticity, despite large variations in stimulus luminance.
Subject(s)
Color Perception/physiology , Contrast Sensitivity/physiology , Electroencephalography , Evoked Potentials, Visual/physiology , Pattern Recognition, Automated , Adolescent , Adult , Electroencephalography/methods , Female , Humans , Male , Pattern Recognition, Automated/methods , Young AdultABSTRACT
PURPOSE: To describe the clinical course and surgical outcome of a patient with full-thickness macular hole recurrence after aflibercept injections for wet age-related macular degeneration. METHODS: Case report with spectral domain optical coherence tomography retinal imaging. RESULTS: An 84-year-old patient, with a successfully closed full-thickness macular hole by vitrectomy and internal limiting membrane (ILM) peel 4 years ago in the right eye, developed neovascular age-related macular degeneration (AMD) of the same eye. After 6 intravitreal aflibercept injections, visual acuity was 20/50, with minimal subretinal fluid (SRF). Four days after the seventh aflibercept injection, visual acuity decreased to 20/200. Spectral domain optical coherence tomography demonstrated a reopened full-thickness macular hole of diameter 430 µm, associated with a reduction in pigment epithelial detachment height, increase in SRF, and an epiretinal membrane (ERM). A 23-gauge pars plana vitrectomy with indocyanine green-assisted removal of residual ILM and ERM, and sulfur hexafluoride (SF6) 20% tamponade was performed. At 1 month postoperatively, the full-thickness macular hole was successfully closed and visual acuity improved to 20/80. CONCLUSION: In wet AMD eyes with previously closed macular holes, hole reopening may occur as a rare complication of aflibercept therapy.
Subject(s)
Receptors, Vascular Endothelial Growth Factor/administration & dosage , Recombinant Fusion Proteins/administration & dosage , Retinal Perforations/surgery , Visual Acuity , Vitrectomy/methods , Wet Macular Degeneration/drug therapy , Aged, 80 and over , Angiogenesis Inhibitors/administration & dosage , Angiogenesis Inhibitors/adverse effects , Humans , Male , Receptors, Vascular Endothelial Growth Factor/antagonists & inhibitors , Recombinant Fusion Proteins/adverse effects , Retinal Perforations/diagnosis , Retinal Perforations/etiology , Retrospective Studies , Tomography, Optical Coherence , Wet Macular Degeneration/diagnosisABSTRACT
PURPOSE: To report a rare case of spontaneous vitreous and intraretinal hemorrhage in a patient with juvenile X-linked retinoschisis which was managed conservatively. METHODS: Single patient case report. INTRODUCTION: Juvenile X-linked retinoschisis (JXLR) most often occurs as a result of a genetic defect in the retinoschisin (RS1) gene, causing a separation between the ganglion cell layer and the nerve fiber layer. Spontaneous vitreous hemorrhage has been reported as an uncommon secondary consequence of JXLR. We present a case of spontaneous vitreous and diffuse macular intraretinal hemorrhages in a patient with JXLR which resolved with medical management alone. RESULTS: A 23-year-old man with a history of juvenile X-linked retinoschisis presented to the ophthalmic emergency room complaining of acute onset of floaters in his right eye. On examination, the patient was found to have a new vitreous hemorrhage with diffuse intraretinal hemorrhages in his right eye, without new retinal tears or detachment. SD-OCT demonstrated multifocal pockets of subretinal fluid. The genetic testing panel revealed a hemizygous mutation in the RS-1 gene. He was managed conservatively on oral acetazolamide, with the resolution of the subretinal fluid and with both visual and symptomatic improvement. CONCLUSIONS: Spontaneous vitreous hemorrhage may rarely occur in patients with JXLR, even in the absence of acute retinal tear or detachment. This case demonstrates an atypical presentation of vitreous hemorrhage with diffuse intraretinal hemorrhage and new multifocal areas of subretinal fluid which improved without surgical intervention. Good outcomes may be achieved in these patients with conservative management alone, even in atypical presentations.
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PURPOSE: To assess the associations and predictive value of spectral-domain (SD) OCT inner and outer retinal structural parameters and visual acuity (VA) outcomes in macular edema (ME) secondary to central retinal vein occlusion (CRVO). DESIGN: Retrospective, longitudinal cohort study. PARTICIPANTS: Eighty-four patients with ME secondary to CRVO receiving pro re nata anti-vascular endothelial growth factor (VEGF) therapy at 3 tertiary-level retina referral centers. METHODS: In all participants, VA, demographic and clinical parameters, and SD OCT images from baseline, 3 months, and 12 months were reviewed. Spectral-domain OCT-based morphologic features in the 1500-µm foveal zone were analyzed by masked graders for disorganization of the retinal inner layers (DRIL), ellipsoid zone (EZ) and external limiting membrane disruption, cone outer segment tip (COST) visibility, cysts, subretinal and intraretinal fluid, and epiretinal membranes. MAIN OUTCOME MEASURES: Spectral-domain OCT-based retinal structural parameters and VA outcomes. RESULTS: In multivariate analyses adjusting for baseline VA, worsening VA over 1 year was associated with 1-year increases in DRIL (point estimate, 0.06 per 100 µm; P < 0.001) and EZ disruption (0.07 per 100 µm; P = 0.023), but decreased COST visibility (-0.09 per 100 µm; P = 0.018). A 3-month increase in DRIL (0.05 per 100 µm; P = 0.003) and EZ disruption (0.10 per 100 µm; P < 0.001) were the only factors predicting VA worsening over 1 year, after controlling for baseline VA. A multivariate model including 3-month evolution in DRIL, EZ disruption, and VA accounted for 86.3% of variability in 1-year VA change. Absolute differences between predicted and actual 1-year VA were within 2 lines in 80.9%. When DRIL increased by 250 µm or more over 3 months, no eyes showed VA improvement of 1 line or more in 1 year. When EZ disruption decreased by 250 µm or more over 3 months, no eyes worsened by 1 line or more over 1 year. CONCLUSIONS: Early recovery over 3 months in both DRIL and EZ parameters are key drivers of 1-year VA outcomes. Predictive models incorporating 3-month changes in DRIL and EZ disruption support their usefulness as potential robust determinants of future VA.
Subject(s)
Fluorescein Angiography/methods , Macular Edema/etiology , Retina/pathology , Retinal Vein Occlusion/diagnosis , Tomography, Optical Coherence/methods , Visual Acuity , Aged , Female , Follow-Up Studies , Fundus Oculi , Humans , Macular Edema/diagnosis , Macular Edema/physiopathology , Male , Prognosis , Retinal Vein Occlusion/complications , Retinal Vein Occlusion/physiopathology , Retrospective StudiesABSTRACT
Basic color terms used in Mandarin Chinese have been controversial since first discussed by Berlin and Kay in 1969. Previous studies showed much inconsistency on what should be considered as basic color terms in Mandarin Chinese. In the present study, we investigated categories of color rather than merely the color terms used by Taiwanese native Mandarin speakers. Using samples conforming to the Berlin and Kay survey, various colors were chosen from a collection of Natural Color System (NCS) colored papers and mounted on a piece of neutral gray card. The card was then mounted on a touch-screen, under D65 illumination. Thirty-two single-character color related Mandarin terms were selected from a Chinese character database according to frequency of use. Participants were required to select the color sample that matched the term by pressing a virtual button on the touch screen. The results show that certain terms can be directly correlated to basic color terms in English, comparable with the results of Berlin and Kay's original study and those that followed. However, some terms, such as Mo ( ink), Tie ( iron), and Cai (vegetable), show a wide spread of term maps and inconsistent use among subjects. Principle component analysis (PCA) procedures were used to analysis the commodity of data among subjects. The findings suggest that the basic color categories among Mandarin Chinese speakers are similar to those found in the World Color Survey (WCS), but are represented by wide-spread and inconsistent color terms among speakers.
Subject(s)
Color Perception , Color , Linguistics , Reading , Adult , Humans , Pattern Recognition, Visual , Principal Component Analysis , Young AdultABSTRACT
PURPOSE: We report the case of a patient with cavernous sinus syndrome associated with biopsy-confirmed metastasis from colorectal cancer. OBSERVATIONS: A patient known for laryngeal carcinoma and metastatic colorectal carcinoma presented with symptoms of left trigeminal neuralgia and progressive, near-complete ophthalmoplegia. Magnetic resonance imaging (MRI) revealed a mass in the left cavernous sinus, extending into Meckel's cave with perineural spread along the mandibular branch of the left trigeminal nerve. A transsphenoidal biopsy was performed and demonstrated metastatic colon adenocarcinoma. We review the existing literature on colorectal cancer associated cavernous sinus syndrome. CONCLUSIONS AND IMPORTANCE: Cavernous sinus metastasis from colorectal cancer is exceedingly rare. We report the second case of this entity with histopathologic confirmation, and the first case with concurrent perineural spread involving the trigeminal nerve. Cavernous sinus metastasis may represent a poor prognostic factor in colorectal cancer.
ABSTRACT
Bietti's crystalline dystrophy (BCD) is a rare, autosomal recessive retinal degenerative disease associated with mutations in CYP4V2. In this study, we describe the genetic and clinical findings in 19 unrelated BCD patients recruited from five international retinal dystrophy clinics. Patients underwent ophthalmic examinations and were screened for CYP4V2 mutations by Sanger sequencing and quantitative polymerase chain reaction (qPCR) copy number variation screening. Eight CYP4V2 mutations were found in 10/19 patients, including three patients in whom only monoallelic mutations were detected. Four novel mutations were identified: c.604G>A; p.(Glu202Lys), c.242C>G; p.(Thr81Arg), c.604+4A>G; p.(?), and c.1249dup; p.(Thr417Asnfs*2). In addition, we identified a heterozygous paternally inherited genomic deletion of at least 3.8 Mb, encompassing the complete CYP4V2 gene and several other genes, which is novel. Clinically, patients demonstrated phenotypic variability, predominantly showing choroidal sclerosis, attenuated vessels, and crystalline deposits of varying degrees of severity. To our knowledge, our study reports the first heterozygous CYP4V2 deletion and hence a novel mutational mechanism underlying BCD. Our results emphasize the importance of copy number screening in BCD. Finally, the identification of CYP4V2-negative patients with indistinguishable phenotypes from CYP4V2-positive patients might suggest the presence of mutations outside the coding regions of CYP4V2, or locus heterogeneity, which is unreported so far.
ABSTRACT
This study investigated two aspects of visual sensitivity to a change in light level. The first experiment examined the time course of sensitivity to a small amplitude 1-s contrast pedestal presented on a 163-td pedestal within a 115-td surround. The largest contrast pedestal was an 8% contrast change that changed the steady pedestal threshold by only 0.03 log unit. Thresholds increased by 0.6 log unit or more at both onset and offset, with a return to baseline within 100 ms. The increment and decrement thresholds showed different time courses. Increment thresholds were raised before pedestal onset and decrement thresholds were raised before pedestal offset. These data were interpreted to show that increment thresholds measured at onset and offset of a contrast pedestal accessed on-pathways and decrement thresholds accessed off-pathways. In the second experiment, we examined the time course of sensitivity using a Crawford paradigm. Observers were dark-adapted and sensitivity was measured before, during, and after a 0.5-s, 68-td pulse. Test stimuli were slightly biased in chromaticity and the observer reported the presence and the hue appearance of the test, allowing separate estimates of detection and hue identification. Thresholds increased during the pulse but showed only a minimal overshoot. The test sensitivity for detection was poorer than for hue identification in the dark, but detection and identification were similar during the pulse. These data suggest that thresholds during sizable luminance pulses are determined in the PC-pathway.
Subject(s)
Adaptation, Ocular/physiology , Lighting , Visual Perception/physiology , Contrast Sensitivity/physiology , Humans , Sensory Thresholds/physiologyABSTRACT
Eukaryotic microalgae and cyanobacteria have recently reemerged as promising organisms in the effort to develop sustainable options for production of food and fuel. However, substantial discrepancies consistently arise between laboratory and outdoor cultivation, and gains demonstrated using laboratory technologies have not paralleled gains observed in field demonstrations. For these reasons, a low-maintenance system and process for research-scale outdoor cultivation of a variety of both freshwater and marine microalgae and cyanobacteria was developed. Nine genera were evaluated in the system, demonstrating cultivation of both laboratory model and commercial-production organisms. Hundreds to thousands of grams of dry biomass could be produced in a single growth cycle, suitable for a variety of uses including inoculum generation, protein production, and biofuel applications. Following testing in outdoor stock-ponds, Scenedesmus and Nannochloropsis were grown semi-continuously in an 8000 L airlift-driven raceway, yielding in total over 8 kg of dry biomass for each strain.