Biomedical subjects

P A Sample

Publications and source records attributed to P A Sample.

At least 37 records · Page 2Linked to original sources

PubMed1998

Patterns of optic disk damage in patients with early focal visual field loss.

PURPOSE: To study the patterns of structural damage of the optic disk in patients with early focal visual field loss using a confocal scanning laser ophthalmoscope. METHODS: Thirty-nine subjects with repeatable early focal visual field loss were included. The Heidelberg Retina Tomograph (Heidelberg Engineering, Heidelberg, Germany) was used to obtain topographic optic disk measurements. For analysis of structural damage, the topographic measurements were divided into 36 10-degree sectors. Sector analysis was performed using sector rim area to sector disk area ratio. Patients were assigned to one of three groups based on the measurement of the optic disk damage: (1) diffuse disk damage; (2) focal disk damage; or (3) no detectable disk damage. RESULTS: Approximately half of the patients with early focal glaucomatous visual field loss showed diffuse optic disk damage, one quarter to one third had focal damage, and one sixth had no detectable damage. Optic disk area was smallest in the no-detectable-damage group (1.71 + 0.19 mm2), followed by the focal-damage group (2.06 + 0.54 mm2), and was largest in the diffuse damage group (2.29 + 0.48 mm2; P = .22). CONCLUSION: In patients with early focal glaucomatous visual field loss, observable optic disk damage can be diffuse, focal, or undetectable. The Heidelberg Retina Tomograph may be capable of detecting different patterns of diffuse or focal structural damage.

Adult↗

PubMed1998

Mapping structural to functional damage in glaucoma with standard automated perimetry and confocal scanning laser ophthalmoscopy.

PURPOSE: To develop a quantitative method for analysis of the topographic relationship between structural and functional damage in patients with glaucoma. METHODS: We studied 26 patients with primary open-angle glaucoma, focal optic disk damage, and focal visual field loss. The visual field was evaluated with automated perimetry, and the optic disk topography was assessed with a confocal scanning laser ophthalmoscope. Topographic measurements were calculated in 10-degree sectors and compared with a normative database (n=52). The topographic relationship of structural damage and functional loss was analyzed. RESULTS: Rim area ratio was defined as the ratio of rim area in each 10-degree sector divided by the total rim area. This ratio resulted in the identification of one (46%) or more (54%) clusters of optic disk sectors as outside normal limits in all 26 patients (12 and 14 patients, respectively). Twenty-two patients (84%) with superior hemifield sensitivity loss tended to have inferior rim defects, and vice versa. Nasal visual field defects close to the horizontal midline were matched with damaged rim areas close to the vertical midline. CONCLUSIONS: This mapping method allows an objective and quantitative evaluation of the optic disk and visual field in patients with glaucoma and focal damage. Although the topographic relationship between structure and function is characterized by considerable interindividual variability, the identification of certain patterns may be useful to aid in the evaluation of glaucomatous damage.

Adult↗

PubMed1998

Visual dysfunction in HIV-positive patients without infectious retinopathy.

Persons with HIV disease are susceptible to various manifestations of retinal damage, such as infectious retinopathies (e.g., cytomegalovirus [CMV] retinitis and toxoplasmosis) and noninfectious complications (microangiopathic infarctions or cotton-wool spots [CWS]); CWS being quite common in AIDS patients. Until recently, little research focused on noninfectious ocular pathology in HIV disease. These disorders may all affect normal functioning of the visual system while funduscopic examination results appear normal. A review of the psychophysical changes, color and contrast sensitivity, peripheral visual function, electrophysiologic and morphologic changes, the relationship of vision loss and neuropsychological changes, postretinal damage, and imaging capabilities cast important new light on quality of life issues and vision function for all HIV/AIDS patients regardless of CD4 count, other measures of wellness, or treatment protocols. Entopic perimetry, a low-cost psychophysical technique screening test, allows sensitive and specific identification of very peripheral areas of visual field loss. The authors recommend its implementation and use by primary care providers, particularly for early detection of retinal damage when funduscopic examination results may appear normal.

Acquired Immunodeficiency Syndrome↗

PubMed1998

Detection of early glaucomatous structural damage with confocal scanning laser tomography.

PURPOSE: The authors determine which optic disc topographic parameters obtained by the Heidelberg Retina Tomograph (HRT, Heidelberg Engineering, Heidelberg, Germany) are most useful in detecting individuals with early glaucomatous visual field loss. METHODS: Ninety-nine eyes of 49 healthy individuals and 50 age-matched individuals with early glaucomatous visual field loss were included. Three images were obtained and the mean topography image was created and used in the analyses. The HRT discriminant analysis function (software version 2.01) was applied and compared to the Fisher linear discriminant function developed in this population. Analysis was repeated after stratifying by disc area (< 2 mm2 or 2-3 mm2). RESULTS: There were statistically significant differences between the healthy and glaucomatous groups for all optic disc topographic parameters (p < 0.05) measured. These differences remained after the analysis was repeated controlling for disc size, except for height variation contour. Applying the HRT discriminant function to this study population resulted in sensitivity and specificity of 62% and 94%, respectively. The sensitivity was 83% while specificity remained high (91%) for larger disc sizes. Using this data, additional discriminant functions that differentiated similarly between the two groups were found. The best formula used cup-shape measure (third moment), rim area, height variation contour, and retinal nerve fiber layer thickness and had a sensitivity and specificity of 78% and 88%, respectively. CONCLUSIONS: Several different discriminant analysis formulas are capable of detecting early glaucomatous visual field loss in a comparable manner. The characteristics of the study population are likely to influence the discriminating power of these various formulas.

Adult↗

PubMed1997

Short-wavelength automated perimetry and motion automated perimetry in patients with glaucoma.

OBJECTIVE: To compare short-wavelength automated perimetry (SWAP), a test favoring the detection of the target by the parvocellular pathways of vision, with motion automated perimetry (MAP), a test favoring detection by the magnocellular pathways, in the same eyes. PARTICIPANT: Thirty-three individuals in whom glaucoma was suspected (glaucoma suspects) and 17 patients with primary open-angle glaucoma were compared with 30 age-matched normal control subjects. INTERVENTIONS: Short-wavelength automated perimetry was done with the usual protocol (program 24-2). Motion coherence thresholds were measured with 14 random do targets that covered the 24-2 field area. Short-wavelength automated perimetry test locations corresponding to each of the 14 motion automated perimetry locations were averaged to compare 14 locations for each text. RESULTS: Short-wavelength automated perimetry and motion automated perimetry were correlated by visual field location (whole field r = -0.40, P < .001), especially in the superior field (r = -0.45, P < .001). Overlap for defective locations was present in 16 (94%) of the 17 eyes with glaucoma, although in the glaucoma suspect eyes each test showed the earliest deficit in a percentage of individuals with overlap in only 3 (21%) of the 14 eyes. An analysis of variance showed a significant effect of diagnosis for both tests (SWAP and MAP, P < .001); the eyes of patients with glaucoma were significantly different from those of the normal controls. The results for glaucoma suspects were significantly different on SWAP only in the superior temporal field (Tukey-Kramer test). CONCLUSIONS: Both tests successfully identified eyes with glaucoma and a percentage of the glaucoma suspect eyes; both were correlated by field location. These results suggest that damage due to glaucoma is nonselective for either the parvocellular or the magnocellular ganglion cell axons, that there may be individual differences in which type of ganglion cell shows damage first, and that when standard visual field loss is present the results of SWAP and MAP are defective.

Glaucoma, Open-Angle↗

PubMed1997

Analysis of visual dysfunctions in HIV-positive patients without retinitis.

PURPOSE: To investigate visual dysfunctions in ophthalmoscopically normal human immunodeficiency virus (HIV)-positive patients and to correlate the results to the stage of HIV disease and neuropsychological status. METHODS: Fifty-one randomly selected eyes (26 right, 25 left) of 51 HIV-positive patients with visual acuity measurements of 20/20 or better and no ophthalmoscopically detectable disorders were prospectively examined using achromatic and short-wavelength automated perimetry, color vision testing, and contrast sensitivity testing. CD4+ T-lymphocyte count, presence of systemic infection, hemoglobin, hematocrit, serum beta 2-microglobulin levels, and results of neuropsychological testing were also analyzed. RESULTS: On achromatic automated perimetry, 21.6% (11/51) of patients performed abnormally according to the mean defect and 27.5% (14/51) according to the Glaucoma Hemifield Test; 29.4% (15/51) performed abnormally on short-wave-length automated perimetry according to the mean defect and 23.5% (12/51) according to the Glaucoma Hemifield Test. On contrast sensitivity, 5.9% (3/51) of patients performed abnormally in the 1.5-cycles per degree (cpd) line, 2.0% (2/51) in the 3-cpd line, 23.5% (12/51) in the 6-cpd line, 25.5% (13/51) in the 12-cpd line, and 33.3% (17/51) in the 18-cpd line. On the Farnsworth-Munsell 100-hue test, 29.4% (15/51) of patients performed abnormally. After correction for multiple correlations, two statistically significant correlations were found: sum of log contrast sensitivity with achromatic automated perimetry and sum of log contrast sensitivity with the Farnsworth-Munsell 100-hue test. CONCLUSIONS: A significant percentage of HIV-positive patients with visual acuity of 20/20 or better and no ophthalmologic evidence of retinitis performed abnormally on visual psychophysical tests. The severity of visual dysfunction was not correlated with the stage of HIV infection or the degree of neuropsychological dysfunction.

Adult↗

PubMed1997

Mapping structural damage of the optic disk to visual field defect in glaucoma.

PURPOSE: To evaluate the relation between the location of focal visual field defects and optic disk damage in eyes with glaucoma by short-wavelength automated perimetery and confocal scanning laser ophthalmoscopy. METHODS: In 14 patients (14 eyes) with open-angle glaucoma, focal optic disk damage, and focal visual field loss, we obtain visual fields with short-wave-length automated perimetry. The short-wavelength automated perimetry visual field was divided into 21 zones, representing retinal nerve fiber layer arcuate bundles. Test points were compared with a normative database. The optic disk was assessed with a confocal scanning laser ophthalmoscope. Optic disk measurements were calculated in 10-degree sectors and compared with a normative database using a new measure, the rim area ratio, which adjusts for individual differences in disk size. RESULTS: The mean number (+/-SD) of damaged visual field zones was 3.9 (+/-1.9), and the mean number of damaged rim sectors was 5.0 (+/-2.9). Focal defects on the optic disk and on short-wavelength automated perimetry were topographically related with specific damaged visual field zones corresponding to specific damaged rim sectors. CONCLUSIONS: In patients with open-angle glaucoma with focal optic disk damage and focal visual field loss, defects in optic disk and short-wavelength automated perimetry are topographically related. The rim area ratio can be used to identify focal optic nerve defects.

Adult↗

PubMed1997

Asymmetries in the normal short-wavelength visual field: implications for short-wavelength automated perimetry.

PURPOSE: To quantify short-wavelength sensitivity in normal eyes by hemifield location, eccentricity, and age. METHODS: We measured achromatic and short-wavelength thresholds across visual fields covering a radius of 21 degrees of visual angle in 115 normal eyes in subjects aged 17 to 77 years and out to 30 degrees of eccentricity in an additional 57 eyes in subjects aged 22 to 80 years. RESULTS: Results indicated significantly greater sensitivity for the inferior visual field compared with the superior field (P = .001). The amount of asymmetry increased with eccentricity (P = .001) but not with age (P = .357). A temporonasal field asymmetry was noted at the most eccentric points of the 30-degree field (P = .001) but not at 21 degrees (P = .821). CONCLUSIONS: In addition to increasing our understanding of normal retinal function, these results have implications for basic research in comparison with results of studies using different retinal locations to assess short-wavelength sensitivity and for clinical practice, where short-wavelength sensitivity is used to diagnose and manage a number of diseases, including glaucoma, diabetic retinopathy, and acquired immunodeficiency syndrome (AIDS)-related vision loss.

Adolescent↗

PubMed1997

Motion perception thresholds in areas of glaucomatous visual field loss.

This study examined whether one can differentiate between areas of known visual field loss and areas of known relative field sparing in eyes with primary open angle glaucoma using motion coherence thresholds. Two visual field locations from patients with primary open angle glaucoma (n = 14), which differed significantly in sensitivity, were selected for presentation of a motion stimulus. In the area of visual field loss mean threshold was 17.4 +/- 4.1 dB (1.74 +/- 0.41 log units relative to the brightest stimulus). In the area of relative field sparing mean threshold was 27.0 +/- 3.6 dB (2.70 +/- 0.36 log units). Motion coherence thresholds were significantly poorer for the area of visual field loss compared to the area of relative field sparing (P < 0.0032, two-tailed paired t-test). This result suggests that a perimetric type motion test should be evaluated for early detection of glaucoma.

Glaucoma, Open-Angle↗

PubMed1997

Perimetric motion thresholds are elevated in glaucoma suspects and glaucoma patients.

The purpose of this study was to determine if a clinically feasible perimetric motion test utilizing random-dot kinematograms could identify glaucomatous visual field defects. Using a staircase procedure, an automated perimetric motion test and a larger foveally presented target were given to normal (n = 30), glaucoma suspects (n = 31) and primary open-angle glaucoma patients (n = 19). Motion thresholds at specific locations throughout the whole visual field were significantly elevated in glaucoma patients (P < or = 0.001). Perimetric motion testing identified 84.2% of the primary open-angle glaucoma patients and 25.8% of the glaucoma suspects as abnormal. A larger foveal stimulus was unable to distinguish between the different subject groups (P < or = 0.185). Perimetric motion thresholds were significantly correlated with Humphrey standard visual field thresholds in the glaucoma and glaucoma-suspect patients (P < or = 0.0002).

Age Factors↗

PubMed1996

Effectiveness of entoptic perimetry for locating peripheral scotomas caused by cytomegalovirus retinitis.

OBJECTIVE: To determine the the effectiveness of random particle motion, presented on a computer monitor, as a noninvasive test for detecting cytomegalovirus retinitis. DESIGN: A prospective masked study in which patients were asked to trace out any disturbances on a transparency placed over a computer monitor that displayed continuous random particle motion, while the patient fixated on a central spot (entoptic perimetry). SETTING: The Acquired Immunodeficiency Syndrome Ocular Research Unit at the University of California, San Diego, in La Jolla. PATIENTS: Twenty-two men with cytomegalovirus retinitis who were positive for human immunodeficiency virus, 11 men without cytomegalovirus retinitis who were positive for human immunodeficiency virus, and eight men who were negative for human immunodeficiency virus. INTERVENTION: None. MEASUREMENTS: Sensitivities and specificities were used to compare the results of entoptic perimetry with fundus photographs. RESULTS: Entoptic perimetry demonstrated a 95% sensitivity and a 95% specificity in detection of cytomegalovirus retinitis. CONCLUSION: Entoptic perimetry may be an effective and inexpensive screening test for cytomegalovirus retinitis in hospitals and community clinics.

AIDS-Related Opportunistic Infections↗

PubMed1996

Optic nerve head topography in ocular hypertensive eyes using confocal scanning laser ophthalmoscopy.

PURPOSE: To compare measurements of optic nerve topography of ocular hypertensive patients with those of normal subjects and primary open-angle glaucoma patients. METHODS: Three age-matched study groups of 46 ocular hypertensive patients, 46 primary open-angle glaucoma patients, and 46 normal subjects were recruited from patients and volunteers of a glaucoma referral practice. Optic nerve topography was measured using a confocal scanning laser tomograph, the Heidelberg Retina Tomograph. The following optic nerve parameters were evaluated: disk area, cup/disk area ratio, cup shape, height in contour, rim area, rim volume, maximum cup depth, cup area, cup volume, retinal height, and retinal cross-section area. For this cross-sectional study, analysis of variance was used to evaluate overall differences among the three subject groups and the Tukey-Kramer multiple comparison test to evaluate differences between the means of two groups. RESULTS: Statistically significant differences among study groups were found for all topographic optic nerve parameters evaluated. Despite considerable overlap in optic nerve parameter measurements among the study groups, mean values of ocular hypertensive eyes were intermediate between those for normal and primary open-angle glaucoma eyes. Statistically significant differences were found between ocular hypertensive and glaucomatous eyes for all optic nerve parameters measured, and between ocular hypertensive and normal eyes for disk area, height in contour, rim area, and rim volume. CONCLUSIONS: In age-matched groups, mean measurements of certain topographic optic nerve parameters of ocular hypertensive eyes differ from those of normal and glaucomatous eyes.

Cross-Sectional Studies↗

PubMed1996

Visual field loss in HIV-positive patients without infectious retinopathy.

PURPOSE: To determine the extent of vision loss in a cross-sectional study of HIV-positive individuals who had no infectious retinopathy. METHODS: Visual field loss was determined by computerized achromatic automated perimetry and short-wavelength automated perimetry in both eyes in 65 HIV-positive individuals without infectious retinopathy and in one randomly selected eye each in 57 age-matched normal controls. Results were analyzed using the global index of mean defect and the Glaucoma Hemifield Test, and significance was determined through analysis of variance, chi-square, and Tukey-Kramer tests. RESULTS: We found that HIV-positive patients, compared with age-matched HIV-negative controls, demonstrated significant (at least P < .01) localized defects as well as an increased mean defect. The HIV-positive patients also had a significantly greater number of defective points, especially on short-wavelength automated perimetry, even while ophthalmoscopic examination and fundus photographs suggested that the retinas were normal. CONCLUSIONS: There is a significant loss of visual function in HIV-positive individuals that is not the result of infectious retinopathies. The finding by short-wavelength perimetry of more severe defects suggests that the vision defects are not caused by attentional or other suprachiasmatic problems because the neurologic difficulty of both achromatic and short-wavelength perimetry is similar. The effects of this vision loss on the daily living and occupational tasks of this population require further study.

Adult↗

PubMed1996

Pattern electroretinograms and visual evoked potentials in HIV infection: evidence of asymptomatic retinal and postretinal impairment in the absence of infectious retinopathy.

Retinal microangiopathy associated with HIV infection is usually asymptomatic and escapes detection unless funduscopic examination is performed when evanescent cotton-wool spots are present. The aim of this study was to assess retinal and optic nerve/retrochiasmal function in HIV infection by means of electrophysiologic techniques that are sensitive to the detection of subclinical visual impairment. We studied transient and steady state pattern electroretinograms grams (PERGs) and pattern-reversal visual evoked potentials (PVEPs) in 21 HIV-negative controls and 33 HIV-positive subjects (16 with CD4 > or = 200/mL and 17 with CD4 < 200/mL) without visual symptoms or infectious retinopathy. HIV-positive subjects with CD4 > or = 200/mL had reduced amplitude of the transient PERG P1 potential, but no other latency or amplitude abnormalities. The HIV-positive group with CD4 < 200/mL had reduced P1 transient PERG amplitude, as well as latency delay of the transient PVEP. These findings suggest that HIV infection is associated with subclinical retinopathy and that, when severe immunosuppression occurs, both retinopathy and optic nerve/retrochiasmal dysfunction are present. Transient PERGs are more sensitive measures of visual system disease in HIV infection than are steady state responses.

Adolescent↗

PubMed1996

Optimum parameters for short-wavelength automated perimetry.

PURPOSE: To determine the optimum parameters for short-wavelength automated perimetry (SWAP) and to recommend these for standardization of the procedure. METHODS: We used a variety of stimulus and background configurations to determine the optimum background spectral distribution and luminance, and the optimum target spectral distribution, maximum luminance, and duration. We measured threshold versus intensity curves to determine which combination provided (a) the greatest isolation of the short-wavelength sensitive mechanisms and (b) the largest dynamic range for perimetry. We also evaluated the effect of lens absorption and cataract on these two factors. RESULTS: A broad-band yellow background at 100 candela/m2 with a narrow-band 440-nm (27-nm half-bandwidth), 1.8 degrees diameter (Goldmann size V) stimulus presented for 200 ms was optimum at all retinal eccentricities. Specific recommendations for how to modify existing perimeters are given. CONCLUSION: Agreement regarding the optimum parameters for SWAP should lead to standardization of the test that will facilitate comparison of results from different centers. Normative data can be collected at several sites and incorporated into statistical analysis packages currently available with various perimeters. This will greatly improve the clinical utility of this test.

Aged↗

PubMed1995

Association between quantitative nerve fiber layer measurement and visual field loss in glaucoma.

PURPOSE: To evaluate the association between quantitative nerve fiber layer measurements and visual field loss in patients with primary open-angle glaucoma. METHODS: Quantitative retinal nerve fiber layer measurements were obtained in 53 patients with primary open-angle glaucoma by using confocal scanning laser ophthalmoscopy (cross-section area) and confocal scanning laser polarimetry (retardation ratio). For each eye, three images were obtained with each instrument. An image that was the mean of those three was created and used in all analyses. We investigated the association between global, regional, and hemifield differences in retinal nerve fiber layer measurements and visual field loss with linear regression techniques. RESULTS: The retardation ratio decreased with increasing mean visual field loss, measured both globally and regionally; R2 (the amount of variation explained by the model) ranged from 8% to 21%. Retinal nerve fiber layer cross-section area was not significantly associated with global measures of visual field loss. The inferior visual field mean deviation increased with decreasing superior retinal nerve fiber layer cross-section area (R2 = 8.2%, P = .04); superior visual field mean deviation was not associated with inferior retinal nerve fiber layer cross-section area (R2 = 2.6%, P = .25). Hemifield differences in visual field mean deviation increased with increasing hemifield differences in retinal nerve fiber layer cross-section area (R2 = 20.0%, P < .001), but not with retardation ratio (R2 = 0.9%, P = .48). CONCLUSIONS: Quantitative measures of the retinal nerve fiber layer using both confocal scanning laser ophthalmoscopy and confocal scanning laser polarimetry were correlated with visual field loss in glaucoma patients.

Aged↗

PubMed1995

Comparison of high-pass resolution perimetry and standard automated perimetry in glaucoma.

PURPOSE: We sought to ascertain whether high-pass resolution perimetry would provide results comparable to those of standard perimetry. METHODS: Thirty-four eyes with primary open-angle glaucoma, 37 eyes suspected of having glaucoma, and 36 normal control eyes were matched for age and lens density. We controlled for refraction, pupil size, and learning effects. Standard and ring visual fields were obtained with the Humphrey perimeter and the Frisén ring perimeter, respectively. Each test was judged according to the Glaucoma Hemifield Test (a statistical visual field analysis method) to be outside normal limits (abnormal) or not outside normal limits (normal or borderline). RESULTS: Under these conditions, both tests identified 19 of 34 (56%) glaucoma eyes as outside normal limits. High-pass resolution perimetry determined that 34 of 36 (94%) normal eyes were not outside normal limits; standard perimetry determined that all 36 normal eyes were not outside normal limits. High-pass resolution perimetry determined 12 of 37 (32%) eyes that were glaucoma suspects were outside normal limits; standard perimetry determined three of the 37 (8%) glaucoma suspect eyes were outside normal limits. Overall agreement between the two tests was 65%. CONCLUSION: With the Glaucoma Hemifield Test, high-pass resolution perimetry was comparable to standard perimetry in sensitivity and specificity, and identified a slightly higher percentage of patients at risk for glaucoma as abnormal. These results suggest that high-pass resolution perimetry should continue to be explored as an alternative to standard perimetry for the diagnosis and treatment of glaucoma.

Female↗

PubMed1994

Short-wavelength automated perimetry without lens density testing.

Three experiments determined whether an estimate of localized short-wavelength visual field loss could provide enough specificity and sensitivity for glaucoma diagnosis, without correcting the fields for lens density. We used 100 normal, 53 glaucoma suspect, and 95 glaucoma eyes (or a subset of these, where noted). The first two experiments showed that lens density has a diffuse effect on the visual field, which is more linear than the effect of age. The third experiment showed that, with the glaucoma hemifield test, comparable results were obtained for short-wavelength fields either corrected or uncorrected for lens density (sensitivities of 81% and 76% and specificities of 82% and 90%, respectively). We conclude that it is possible to eliminate the lens density measurement with this approach, thereby reducing test time by 40 minutes. This should improve substantially the clinical utility of short-wavelength automated perimetry.

Adult↗