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- Compensation for red-green contrast loss in anomalous trichromats. [Journal Article]
- J Vis 2014; 14(13)
For anomalous trichromats, threshold contrasts for color differences captured by the L and M cones and their anomalous analogs are much higher than for normal trichromats. The greater spectral overlap of the cone sensitivities reduces chromatic contrast both at and above threshold. But above threshold, adaptively nonlinear processing might compensate for the chromatically impoverished photoreceptor inputs. Ratios of sensitivity for threshold variations and for color appearance along the two cardinal axes of MacLeod-Boynton chromaticity space were calculated for three groups: normals (N = 15), deuteranomals (N = 9), and protanomals (N = 5). Using a four-alternative forced choice (4AFC) task, threshold sensitivity was measured in four color-directions along the two cardinal axes. For the same participants, we reconstructed perceptual color spaces for the positions of 25 hues using multidimensional scaling (MDS). From the reconstructed color spaces we extracted "color difference ratios," defined as ratios for the size of perceived color differences along the L/(L + M) axis relative to those along the S/(L + M) axis, analogous to "sensitivity ratios" extracted from the 4AFC task. In the 4AFC task, sensitivity ratios were 38% of normal for deuteranomals and 19% of normal for protanomals. Yet, in the MDS results, color difference ratios were 86% of normal for deuteranomals and 67% of normal for protanomals. Thus, the contraction along the L/(L + M) axis shown in the perceptual color spaces of anomalous trichromats is far smaller than predicted by their reduced sensitivity, suggesting that an adaptive adjustment of postreceptoral gain may magnify the cone signals of anomalous trichromats to exploit the range of available postreceptoral neural signals.
- Vision-Related Quality-of-Life Assessment Using NEI VFQ-25 in Patients After Boston Keratoprosthesis Implantation. [JOURNAL ARTICLE]
- Cornea 2014 Nov 19.
The aim of this study was to determine the impact of Boston keratoprosthesis (KPro) implantation on patient-reported visual function using the National Eye Institute Visual Function Questionnaire 25 (NEI VFQ-25).This is a prospective study of patients undergoing implantation of Boston KPro. The NEI VFQ-25 was used to assess vision-related quality of life preoperatively and postoperatively at 3 and 6 months and yearly thereafter. Baseline scores were compared with postoperative scores using paired t test. Stratified analysis was performed to compare results by visual acuity of the contralateral eye.Twenty-four patients were included. Mean baseline NEI VFQ-25 overall score was 44.6. At the first follow-up time point, mean overall score was 70.0, representing a statistically significant change from baseline (P < 0.001). Breakdown of subcategories within VFQ-25 showed significant improvement in general vision, near and distance activities, social functioning, mental health, role difficulties, dependency, color vision, and peripheral vision (P < 0.05). This improvement was also observed when comparing baseline scores with postoperative scores at average follow-up of 16 months. Although a greater change in scores was observed in patients who had poor vision in the contralateral eye, patients with vision better than 20/200 in the nonsurgical eye showed statistically significant improvement in overall scores and subscale scores compared with baseline.The quality of life of patients who underwent KPro significantly improved postoperatively compared with their preoperative status. These results did not change when stratifying by visual acuity of the contralateral eye.
- Alouatta Trichromatic Color Vision: Cone Spectra and Physiological Responses Studied with Microspectrophotometry and Single Unit Retinal Electrophysiology. [JOURNAL ARTICLE]
- PLoS One 2014; 9(11):e113321.
The howler monkeys (Alouatta sp.) are the only New World primates to exhibit routine trichromacy. Both males and females have three cone photopigments. However, in contrast to Old World monkeys, Alouatta has a locus control region upstream of each opsin gene on the X-chromosome and this might influence the retinal organization underlying its color vision. Post-mortem microspectrophotometry (MSP) was performed on the retinae of two male Alouatta to obtain rod and cone spectral sensitivities. The MSP data were consistent with only a single opsin being expressed in each cone and electrophysiological data were consistent with this primate expressing full trichromacy. To study the physiological organization of the retina underlying Alouatta trichromacy, we recorded from retinal ganglion cells of the same animals used for MSP measurements with a variety of achromatic and chromatic stimulus protocols. We found MC cells and PC cells in the Alouatta retina with similar properties to those previously found in the retina of other trichromatic primates. MC cells showed strong phasic responses to luminance changes and little response to chromatic pulses. PC cells showed strong tonic response to chromatic changes and small tonic response to luminance changes. Responses to other stimulus protocols (flicker photometry; changing the relative phase of red and green modulated lights; temporal modulation transfer functions) were also similar to those recorded in other trichromatic primates. MC cells also showed a pronounced frequency double response to chromatic modulation, and with luminance modulation response saturation accompanied by a phase advance between 10-20 Hz, characteristic of a contrast gain mechanism. This indicates a very similar retinal organization to Old-World monkeys. Cone-specific opsin expression in the presence of a locus control region for each opsin may call into question the hypothesis that this region exclusively controls opsin expression.
- Ophthalmological features of Parkinson disease. [Journal Article]
- Med Sci Monit 2014.:2243-9.
Background The aim of this study was to determine the type and frequency of ophthalmologic changes occurring in patients with Parkinson disease (PD). Material and Methods One hundred consecutive patients (196 eyes) with idiopathic PD and a control group consisting of 100 healthy patients (196 eyes) matched for age and sex underwent a complete ophthalmological examination of both eyes, including assessment of patient medical history, dry eye questionare, and visual hallucinations questionnaire, distance and near best corrected visual acuity (DBCVA, NBCVA), color vision, distance photopic contrast sensitivity, near point of convergence, slit lamp examination of the eye anterior segment, tear film osmolarity and breakup time, aqueous tear production, and intraocular pressure, as well as fundus examination and evaluation of the perimacular retinal thickness (RT) and peripapillary retinal nerve fiber layer (RNFL) thickness. Results In the eyes of PD patients DBCVA, NBCVA, contrast sensitivity, and color discrimination were significantly reduced. We also detected increased frequency of convergence insufficiency, seborrhoic blepharitis, meibomian gland disease (MGD), dry eye syndrome, nuclear and posterior subcapsular cataract, and glaucoma (p<0.05). However, intraocular pressure (IOP) was significantly lower in the PD group compared to controls. The frequency of visual hallucinations, age-related macular degeneration (ARMD), and other ophthalmological diseases, as well as RT and RNFL thickness, did not significantly differ between investigated groups. Conclusions Clinicians need to be aware of the association between PD and ophthalmological changes. Restoration of good-quality vision has a great impact on PD patients' quality of life, reduction of costs of treatment and care, and rehabilitation.
- High-speed odor transduction and pulse tracking by insect olfactory receptor neurons. [JOURNAL ARTICLE]
- Proc Natl Acad Sci U S A 2014 Nov 10.
Sensory systems encode both the static quality of a stimulus (e.g., color or shape) and its kinetics (e.g., speed and direction). The limits with which stimulus kinetics can be resolved are well understood in vision, audition, and somatosensation. However, the maximum temporal resolution of olfactory systems has not been accurately determined. Here, we probe the limits of temporal resolution in insect olfaction by delivering high frequency odor pulses and measuring sensory responses in the antennae. We show that transduction times and pulse tracking capabilities of olfactory receptor neurons are faster than previously reported. Once an odorant arrives at the boundary layer of the antenna, odor transduction can occur within less than 2 ms and fluctuating odor stimuli can be resolved at frequencies more than 100 Hz. Thus, insect olfactory receptor neurons can track stimuli of very short duration, as occur when their antennae encounter narrow filaments in an odor plume. These results provide a new upper bound to the kinetics of odor tracking in insect olfactory receptor neurons and to the latency of initial transduction events in olfaction.
- Bilateral subinternal limiting membrane hemorrhage in benzene toxicity. [Journal Article]
- Retin Cases Brief Rep 2014; 8(4):276-8.
To report the clinical and spectral domain optical coherence tomography findings in a patient with bilateral central vision loss and a history of exposure to polyamides.The clinical presentation of the patient was documented with color fundus photographs and spectral domain optical coherence tomography. The patient was a 20-year-old male factory worker with no medical history who was initially admitted for workup of hematologic malignancy due to petechiae and fevers.Optical coherence tomography revealed bilateral hemorrhages in the subinternal limiting membrane space resembling Valsalva retinopathy. Complete blood count revealed pancytopenia and marked thrombocytopenia.Heavy exposure to benzene, a byproduct of the polyamide-curing process, is known to cause aplastic anemia. Accompanying thrombocytopenia may increase the risk of spontaneous subinternal limiting membrane hemorrhage.
- Bilateral perifoveal macular ischemia in sarcoidosis. [Journal Article]
- Retin Cases Brief Rep 2014; 8(3):212-4.
To represent and evaluate the findings of bilateral perifoveal macular ischemia in a patient with biopsy-proven, multiorgan involved sarcoidosis.Case report. A 55-year-old man, with a medical history of pulmonary disease, experienced reduced vision bilaterally. General ocular examination, fundus color photographs, fluorescence angiography, and high-resolution spectral domain optical coherence tomography were performed in both eyes.The patient's visual acuity was 20/200 in the right eye and 20/30 in the left eye with normal intraocular pressure and anterior segment. Fundus examination showed symmetric changes with the loss of transparency in macular and small intraretinal hemorrhages in both eyes. Fluorescence angiography demonstrated markedly enlarged avascular zone while optical coherence tomography revealed marked cystic change in the macula bilaterally. A series of blood test was conducted without a specific diagnosis. A lung biopsy confirmed the diagnosis of pulmonary sarcoidosis, and a magnetic resonance imaging of his brain revealed neurosarcoidosis.Bilateral perifoveal ischemia, formerly one of the three idiopathic macular telangiectasia diseases, is rare and usually suggests a systemic etiology. It is not unexpected that sarcoidosis, a multisystem, chronic inflammatory disorder, may affect retinal vessels and be associated with this peculiar form of ischemia and edema.
- Central serous chorioretinopathy after trabeculectomy in a patient with microphthalmos and congenital rubella syndrome. [Journal Article]
- Retin Cases Brief Rep 2014; 8(2):153-6.
To describe a case of central serous chorioretinopathy after trabeculectomy surgery in an eye with microphthalmos in the setting of congenital rubella syndrome.A Case report with color fundus photographs, fluorescein angiography, and spectral domain optical coherence tomography.A 46-year-old African American man, with a history of congenital heart disease and bilateral hearing loss, developed persistent vision loss in the left eye after trabeculectomy surgery. Ocular examination revealed bilateral salt-and-pepper retinopathy and a serous detachment in the macula of the left eye. Fluorescein angiography showed an early "smoke-stack" pattern of hyperfluorescence with progressive filling of the subretinal space consistent with central serous chorioretinopathy. Spectral domain optical coherence tomography documented both size and extent of the serous retinal detachment and showed several pigment epithelial detachments. B-scan ultrasonography confirmed the serous retinal detachment on the left but showed no evidence of posterior eye wall thickening or of retrobulbar fluid. An A-scan revealed an axial length of 21.8 mm on the right and 19.7 mm on left eye, confirming microphthalmos and supporting the suspected diagnosis of congenital rubella syndrome.Although uncommon, central serous chorioretinopathy can occur in anatomically small eyes after trabeculectomy surgery.
- Dark adaptation abnormalities and recovery in acute thioridazine toxicity. [Journal Article]
- Retin Cases Brief Rep 2014; 8(1):45-9.
To document acute thioridazine toxicity from the symptoms only, through the development of ophthalmoscopic signs and recovery of dark adaptation and electroretinogram responses. These findings support the thesis that visual loss is metabolic and reversible if diagnosed early.Case Report.A case is presented of acute thioridazine toxicity with documentation of the development of symptoms before any ophthalmoscopic evidence of toxicity. This case uniquely shows the time course of dark adaptation, showing both delay in adaptation and elevated final threshold, it includes full electrophysiologic studies from within the first weeks of symptoms and regular follow-up demonstrating marked recovery of dark adaptation in terms of both delay and final threshold, a nearly normal electroretinography and normal color vision within 10 months.Our findings give support to the thesis that functional visual disturbance is primarily metabolic and reversible if detected early in the course of toxicity.
- Successful treatment of choroidal neovascularization secondary to persistent placoid maculopathy with intravitreal bevacizumab. [Journal Article]
- Retin Cases Brief Rep 2014; 8(1):37-40.
To report a case of posterior placoid maculopathy with secondary choroidal neovascularization that responded favorably to repeat intravitreal injections of bevacizumab with long-term follow-up.Patient data from all clinic visits were reviewed. These include visual acuity measurements and clinical examination findings, optical coherence tomography, color fundus photography, and fluorescein angiography images from the initial visit and follow-up encounters.This patient showed clear evidence of active leakage from choroidal neovascularization on presentation that promptly resolved with treatment. After his initial course of injections, all evidence of active exudation disappeared from his optical coherence tomography scans. However, when treatment was extended beyond 8 weeks, choroidal neovascularization leakage returned. In addition, the patient developed subretinal fibrosis in one eye despite regular treatments. Nevertheless, visual acuity has remained excellent through his most recent encounter.Persistent placoid maculopathy is an exceedingly rare clinical entity. In their original descriptive series, Golchet et al revealed that 9 of the 12 eyes went on to develop poor vision from complications of choroidal neovascularization. There is currently only one case in the literature that describes the use of anti-vascular endothelial growth factor medications in the treatment of persistent placoid maculopathy with promising results. This case adds supporting evidence for this treatment modality and highlights the need for continued follow-up and treatment till 18 months from presentation.