Biomedical subjects

Thasarat S Vajaranant

Publications and source records attributed to Thasarat S Vajaranant.

7 recordsLinked to original sources

PubMed2005

Medulloepithelioma of the ciliary body and optic nerve: clinicopathologic, CT, and MR imaging features.

The definitive diagnosis of medulloepitheliomas of the ciliary body and optic nerve is made by histopathologic examination. Familiarity with rare tumors aids clinicians in accurately diagnosing this rare neoplasm. CT and MR imaging findings can be helpful, especially if the mass is confined in an area of the ciliary body without involvement of the retina. The characteristic findings of cystic changes and possible calcification are suggestive of medulloepithelioma rather than melanoma. The more common and ominous retinoblastoma shares some radiologic features with medulloepithelioma, however, and is thus often a consideration. Clinical diagnosis of medulloepitheliomas of the optic nerve and central nervous system (CNS) is more challenging. The diagnosis is often made by histopathologic examination. Lastly, coexisting CNS tumors and anomalies have been reported in association with intraocular medulloepitheliomas and should be recognized.

Ciliary Body↗

PubMed2004

Relationship of retinal structural and clinical vision parameters to driving performance of diabetic retinopathy patients.

This study identifies clinical vision measures or retinal structural measures associated with the driving performance of diabetic retinopathy patients. Twenty-five licensed drivers with diabetic retinopathy (median age, 53 years; range, 34-72 years) completed clinical tests (visual acuity, letter contrast sensitivity, and Humphrey 30-2 visual fields) and structural examinations (retinal thickness analysis and fundus photograph grading of retinopathy and laser scarring). Driving performance was assessed with an interactive driving simulator and a driving history questionnaire. Increased retinal thickness was significantly correlated with a higher frequency of simulator accidents and near accidents. Laser scar grades significantly correlated with steeper brake-response slopes, increased brake-pressure standard deviation (SD), and longer response times. Subjects with focal laser scars had significantly higher average brake-pedal pressure and brake-pressure SD than subjects without focal laser scars. Retinal thickness and laser scarring correlated with driving simulator performance in subjects with diabetic retinopathy.

Accidents, Traffic↗

PubMed2003

Multifocal electroretinography as a function of age: the importance of normative values for older adults.

PURPOSE: To determine the influence of age on local electroretinographic responses in humans. METHODS: Multifocal electroretinograms (mfERGs) were obtained from 62 normally sighted subjects ranging in age from 21 to 81 years. A stimulus array of 103 scaled hexagons was used to measure electrical signals within a retinal area approximately 46 degrees in diameter. Commonly reported mfERG methods were used to quantify the responses: peak-to-peak amplitudes and implicit times, scalar product amplitude, and amplitude and time scales derived from the algorithm of Hood and Li, published in 1997. RESULTS: Regression analysis showed significant linear relationships of amplitude and timing measures with age. The rates of losses were 10.5% per decade for peak-to-peak amplitude, 11.7% per decade for scalar product amplitude, and 9.5% per decade for a-scale. The rate of amplitude reduction was highest in the central 3 degrees. Age had less influence on implicit time measures. The rates of timing losses were 1.4% per decade for the N1 component and 1.0% per decade for both the P1 component and the t-scale measure. Using predicted interval ranges, the age was calculated at which 50% of the expected values would fall below the lower 95% prediction interval band of younger subjects. CONCLUSIONS: The age-associated mfERG alterations are presented to emphasize the importance of appropriate normative data in interpretation of mfERGs.

Adult↗

PubMed2002

Sequential multifocal electroretinogram findings in a case of Purtscher-like retinopathy.

PURPOSE: To report the multifocal electroretinographic findings of a patient with pancreatitis-associated Purtscher-like retinopathy. DESIGN: Observational case report. METHODS: A 20-year-old man with a history of alcohol abuse and acute pancreatitis underwent multifocal electroretinography (mfERG; 103-scaled hexagons, 8-minute recording time) at 1 week, 4 weeks, and 6 months after the onset of the retinopathy. RESULTS: At 1 week, the patient had extensive cotton- wool spots in the posterior pole bilaterally, and visual acuity was significantly reduced. Both the A-waves and B-waves of the mfERG were depressed in the corresponding areas. At 4 weeks, neither visual acuity nor mfERG showed improvement, although the cotton-wool spots had resolved. Interestingly, at 6 months, visual acuity had improved significantly in the left eye, consistent with increased ratios of mfERG responses for the central area. CONCLUSION: There was no selective reduction of b-waves of the mfERG as anticipated in isolated inner retinal pathology. In this case, both the A-waves and B-waves were reduced, suggesting damage to both outer and inner retinal layers.

Acute Disease↗

PubMed2002

Detection using the multifocal electroretinogram of mosaic retinal dysfunction in carriers of X-linked retinitis pigmentosa.

PURPOSE: To examine whether a mosaic pattern of retinal dysfunction in obligate carriers of X-linked retinitis pigmentosa (XLRP) could be observed in local electroretinographic responses obtained with the multifocal electroretinogram (mfERG). DESIGN: Prospective observational case series. PARTICIPANTS: Five obligate carriers of XLRP (mean age, 53.2 years) were recruited into the study. METHODS: Examination of each subject included a complete ocular examination, Humphrey visual field, standard full-field electroretinogram (ERG), and mfERG testing. For the mfERG, we used a 103-scaled hexagonal stimulus array that subtended a retinal area of approximately 40 in diameter. The amplitudes and implicit times in each location for the mfERG was compared with the corresponding value determined for a group of normally sighted, age-corrected control subjects. MAIN OUTCOME MEASURES: Mapping of 103 local electroretinographic response amplitudes and implicit times within the central 40 with the multifocal electroretinogram. RESULTS: Localized regions of reduced mfERG amplitudes and/or delayed implicit times were found in four of five carriers. In one of these four carriers, a mosaic pattern of mfERG dysfunction was present even in the absence of any clinically apparent retinal changes, retinal sensitivity losses on Humphrey field testing, or abnormal full-field cone ERG responses. However, one carrier with a typical tapetal-like reflex demonstrated no deficit on any functional tests. CONCLUSIONS: The mfERG demonstrated patchy areas of retinal dysfunction in some carriers of XLRP. This mosaic pattern of dysfunction may be observed in some patients with a normal-appearing fundus, normal psychophysical thresholds, and normal amplitude and implicit time full-field ERG cone responses.

Adult↗

PubMed2002

Localized retinal dysfunction in central serous chorioretinopathy as measured using the multifocal electroretinogram.

PURPOSE: To determine the extent of electrophysiologic dysfunction in patients with central serous chorioretinopathy (CSC). DESIGN: Prospective observational case series. PARTICIPANTS: Six patients with unilateral CSC (mean age, 40 years) were recruited into the study. METHODS: Six patients with CSC underwent multifocal electroretinogram (mfERG) testing on both their clinically affected and opposite uninvolved eyes using the VERIS System, with a stimulus array of 103 scaled hexagons. The first positive peak responses were analyzed within six concentric ring annuli centered on the fovea. Amplitudes and implicit times were compared with those of an age-similar control group. MAIN OUTCOME MEASURES: Local electroretinographic response amplitudes and implicit times within the central 40 degrees with the mfERG. RESULTS: All the clinically uninvolved eyes showed mfERG amplitudes and implicit times within the normal range throughout the central 40 degrees of the retina. All six eyes with CSC showed reduced amplitudes and/or delayed implicit times that were limited to the regions of the macula in which clinical changes associated with CSC were apparent. CONCLUSIONS: We observed electroretinographic changes only in the clinically affected eyes, and these were limited to regions with ophthalmoscopically apparent fundus changes. Our findings do not support the conclusion that functional impairment, as measured by the mfERG, in eyes with CSC extends beyond clinically observed fundus changes. We did not observe abnormal mfERG responses in the clinically normal eyes of such patients.

Adult↗

PubMedDate not supplied

Assessing responses of the macula in patients with macular holes using a new system measuring localized visual acuity and the mfERG.

PURPOSE: To evaluate acuity and multifocal electroretinogram (mfERG) responses from the macula in affected and unaffected fellow eyes of patients with macular holes. METHODS: We tested 10 eyes with macular hole and 10 fellow eyes from 11 patients. We measured local visual acuity thresholds at 27 discrete locations within 21 degrees diameter using the Functional Fundus Imaging System (FFIS), a psychophysical system that measures visual acuity as a function of visual field location, and local ERG responses within 45 degrees diameter using the mfERG. RESULTS: In the affected eyes, the mean FFIS visual acuity thresholds were significantly elevated within the central 21 degrees diameter area, compared to a group of control eyes. No significant differences were found between the acuities of the fellow eyes compared to those of the control group. The amplitudes of the first positive peak of the mfERG were reduced in the central 7.8 degrees in affected eyes. In the central 2 degrees , 4 out of 10 affected eyes showed non-measurable ERG signals. The remaining six eyes showed significantly reduced mean amplitudes, but not delayed implicit times, when compared to the control group. For the fellow eyes, the mean amplitudes of the mfERG and implicit times did not differ from the means of the control eyes. CONCLUSIONS: Both local psychophysical and electrophysiological testing demonstrated retinal dysfunction extending beyond the site of the macular holes in some patients (three of the patients had central mfERG amplitudes falling within the normal range).

Aged↗