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Biomedical subjects

Philip P Chen

Publications and source records attributed to Philip P Chen.

9 recordsLinked to original sources
PubMed2003

Scanning laser polarimetry and detection of progression after optic disc hemorrhage in patients with glaucoma.

OBJECTIVE: To examine retinal nerve fiber layer changes with scanning laser polarimetry (SLP) in the eyes of patients with glaucoma and optic disc hemorrhage. METHODS: Automated perimetry and SLP were performed in 17 eyes of 17 patients identified prospectively with optic disc hemorrhage. Criteria for visual field progression were based on decreased sensitivity seen at 3 adjacent points on the total deviation plot. Progression on SLP images was defined as a 15% or more decrease in the average thickness of the affected quadrant (superior or inferior), a 25% or more reduction in the affected quadrant ratio, an increase in the nerve fiber analyzer number of 10 or more (GDx Nerve Fiber Analyzer; Laser Diagnostic Technologies), or any change on Serial Analysis of the SLP images. MAIN OUTCOME MEASURES: Visual field progression and SLP image progression. RESULTS: The mean follow-up was 31 months (minimum, 12 months). Of the 17 eyes, 10 (59%) had visual field progression. No significant change was seen on SLP images for either the total group or the group with visual field progression. Five eyes (29%) showed progression on SLP images, 3 of which also showed visual field progression. Ten eyes showed progression on SLP images that was not confirmed on subsequent imaging. CONCLUSIONS: In eyes with visual field progression after optic disc hemorrhage, a significant change in the SLP image was not seen. Fluctuation of SLP results in patients with glaucoma necessitates confirmation of progression seen on SLP images.

Aged↗
PubMed2003

Intraocular pressure in patients with human immunodeficiency virus and treated with highly active antiretroviral therapy.

PURPOSE: To compare the intraocular pressure (IOP) of patients infected with human immunodeficiency virus (HIV) and treated with highly active antiretroviral therapy (HAART) to a control group and to determine whether HAART reverses the previously reported reduction in IOP associated with HIV infection. DESIGN: Retrospective case control study. METHODS: Review of patients with HIV infection on HAART compared with a matched control group. RESULTS: Among 64 patients and 56 control subjects, no significant difference in IOP was found (P =.520), nor was correlation noted between IOP and either CD4+ T-lymphocyte counts, or viral load. CONCLUSION: When HIV infection is treated with HAART, IOP is not significantly different from that of control subjects.

Adult↗
PubMed2003

Blindness in patients with treated open-angle glaucoma.

PURPOSE: To investigate blindness in patients with treated open-angle glaucoma (OAG) and risk factors for blindness. DESIGN: Retrospective observational case series. PARTICIPANTS: One hundred eighty-six patients seen between April and November 2000 at the University of Washington Medical Center Eye Clinic, diagnosed in 1975 or later, and treated for at least 2 years for OAG. METHODS: Chart review with evaluation of visual acuity and visual field. Kaplan-Meier survival analysis was used to estimate the risk of blindness in one and both eyes. Variables considered to be possible risk factors for blindness were evaluated using chi-square test, t test, and Cox proportional hazards regression analysis. MAIN OUTCOME MEASURES: Blindness, defined as visual acuity of 20/200 or worse, and/or continuous constriction of the visual field to 20 degrees or less in all four quadrants with a size III4e Goldmann stimulus or the equivalent on automated perimetry, allowing a higher threshold level on one point in one quadrant on automated perimetry. RESULTS: The mean duration of disease was 10.2 +/- 4.9 years. Twelve patients were blind in at least one eye from OAG at diagnosis. Nineteen other patients became blind in at least one eye from OAG, and three patients became bilaterally blind from OAG. The Kaplan-Meier estimate for blindness at 15 years in one eye was 14.6%, and in both eyes was 6.4%. Noncompliance with the treatment regimen (P = 0.016) and worse initial visual field loss (P < 0.0001) were significantly associated with development of blindness. Nonwhite race was associated with blindness (P = 0.014) when all blindness, including that found at diagnosis, was considered in the analysis. CONCLUSIONS: Bilateral blindness from chronic OAG was uncommon in this population of treated patients diagnosed in 1975 or later. Of patients with a blind eye, 39% were blind at diagnosis, and worse visual field loss at diagnosis and noncompliance were associated with development of blindness.

Blindness↗
PubMed2003

Intraocular pressure in a Somali population living in the United States.

PURPOSE: Intraocular pressure is a risk factor for the development of glaucomatous optic neuropathy. With few exceptions, higher mean intraocular pressure and greater prevalences of glaucoma have been reported for individuals of African origin. This study was performed to compare the mean intraocular pressure of a group of ethnic East Africans living in the United States with that of Caucasians living in the same community. PATIENTS AND METHODS: Retrospective comparison of Somali patients 30 years of age or greater with age- and gender-matched Caucasian control subjects. All patients were seen in the same clinic in Seattle, Washington, between July 1996 and March 1998. Patients were excluded for conditions or medications affecting intraocular pressure and for a diagnosis of glaucoma. Mean intraocular pressure of the two populations was compared using an independent sample two-tailed t test. RESULTS: Following exclusions and defined age limits, 57 Somali patients and 57 Caucasian control subjects were included in the final analysis. Mean age of Somalis was 48.5 +/- 12.2 years versus 48.1 +/- 11.3 years for control subjects (P = 0.84). The mean intraocular pressure of Somalis was 13.76 +/- 3.63 mm Hg versus 13.94 +/- 2.78 mm Hg for control subjects (P = 0.77). CONCLUSION: Some populations of African origin may not have higher mean intraocular pressures compared with non-African populations. Consideration of ethnic and racial origins more specific than "African" should be given when evaluating intraocular pressure in individual patients.

Adult↗
PubMed2002

Learning effects among perimetric novices in frequency doubling technology perimetry.

PURPOSE: To investigate learning effects, including improvements in reliability indices, in frequency doubling technology (FDT) perimetry in subjects without glaucoma who have not undergone previous automated perimetry. DESIGN: Prospective consecutive case series. PARTICIPANTS: Eighty-one normal subjects. METHODS: Normal subjects were recruited from the University of Washington Eye Clinic who had no history of automated visual field testing. All eyes underwent complete ophthalmic examination. The C-20-5 screening mode of FDT perimetry (Zeiss-Humphrey, San Leandro, CA) was performed after appropriate instruction, including a demonstration of the frequency doubling phenomenon. If any abnormal areas were identified or there were greater than 33% fixation losses or false-positive results, then the test was readministered up to three times or until a normal result was returned. MAIN OUTCOME MEASURES: Normal FDT test. RESULTS: The mean age was 54.8 years (range, 19-94). Sixty-nine subjects (85.2%) returned a normal test after a single test administration. Nine subjects (11.1%) required two administrations, and two subjects (2.5%) required three or more administrations to return a normal test. One subject still tested unreliably after four tests. The number or severity of abnormal locations did not predict the number of trials necessary to overcome learning effects. Fixation loss was the most common reliability problem. Subjects who demonstrated learning effects did not differ significantly in age, visual acuity, refraction, or test time from those who did not. CONCLUSIONS: Some perimetric novices demonstrate learning effects in C-20-5 screening-mode FDT perimetry. Learning effects in FDT perimetry must be considered during screening for glaucoma or other ocular disease.

Adult↗
PubMed2002

Correlation of visual field progression between eyes in patients with open-angle glaucoma.

PURPOSE: To investigate the correlation of visual field progression between eyes in patients with chronic forms of open-angle glaucoma (OAG) and to determine risk factors for progression. DESIGN: Retrospective observational case series. PARTICIPANTS: One hundred fifty-two patients seen between April and November 2000 undergoing bilateral treatment for at least 2 years for OAG and who were followed with standard automated perimetry at the University of Washington Medical Center Eye Clinic. METHODS: Visual field progression was defined using criteria modified from Anderson and Advanced Glaucoma Intervention Study (AGIS) scoring. Progression from a normal to an abnormal visual field required abnormality of two of three criteria (glaucoma hemifield test, corrected pattern standard deviation, and total deviation plot abnormality) on at least two consecutive fields. For abnormal visual fields, criteria for progression were modified from Anderson and were based on worsening observed at three adjacent points on the total deviation plot on at least two consecutive fields. Another definition of progression was a change in AGIS score of four or more points. MAIN OUTCOME MEASURES: Visual field progression. RESULTS: The mean follow-up period was 7.5 +/- 3.6 years. Fifty-four patients (35.5%) showed progression of the more severely affected of the two eyes (worse eye), and 37 patients (24.3%) had progression in the less affected fellow (better) eye. Among these patients, 24 (15.8%) had bilateral progression (44% and 65% of worse and better eyes with progression, respectively). The between-eye correlation for progression was statistically significant (chi-square with Yates' continuity correction; chi = 16.7, P = 0.00004; R = 0.348, P = 0.00001). The Kaplan-Meier estimates at 10 years for progression in the worse eye, the better eye, and both eyes was 44%, 33%, and 21%, respectively. CONCLUSIONS: Between-eye correlation of visual field progression in patients with chronic OAG was statistically and clinically significant. Patient-specific factors may play an important role in visual field progression in OAG. Documented progression of visual field loss in one eye may prompt the physician to consider reducing the target intraocular pressure in both eyes.

Chronic Disease↗
PubMedDate not supplied

Reproducibility of retinal nerve fiber layer thickness measurements using scanning laser polarimetry in pseudophakic eyes.

OBJECTIVE: To assess the reproducibility of retinal nerve fiber layer measurements in pseudophakic normal and glaucomatous eyes using scanning laser polarimetry (GDx, Laser Diagnostic Technologies, Inc., San Diego, CA). PATIENTS AND METHODS: Normal and glaucomatous patients with polymethylmethacrylate posterior chamber intraocular lenses that satisfied entry criteria underwent imaging by two experienced operators. Eyes with posterior capsule opacification or vision less than 20/30 were excluded. Baseline images (mean pixel SD less than 8 mm) were obtained on 3 separate days within a 7-week period. Reproducibility, defined as the pooled within eye variance of these 3 measurements and the coefficient of variation for 12 retardation parameters generated by GDx software were calculated. RESULTS: Eighteen eyes (11 glaucoma, 7 normal) of 15 patients (7 female, 8 male) were enrolled (mean age 78 +/- 6 years). Among glaucomatous eyes, the average mean deviation and corrected pattern standard deviation using achromatic automated perimetry (Zeiss-Humphrey, Dublin, CA) was -3.8 +/- 1.5 dB (range, -1.89 to -5.04 dB) and 4.9 +/- 3.3 dB (range 0 to 11.05 dB), respectively. Coefficient of variation was 10% or less for all retardation parameters except ellipse modulation (20.2%) and neural network number (12.4%). Glaucomatous and normal eyes had similar variability for 8 of 12 (66.7%) retardation parameters. Inferior ratio, ellipse modulation, and superior ratio were significantly less variable in glaucomatous eyes (P = 0.007, 0.02, and 0.04 respectively) than normal eyes. Superior integral was more variable in glaucomatous eyes (P = 0.03). CONCLUSION: Retardation measurements may be obtained in pseudophakic eyes with acceptable reproducibility. Normal eyes and eyes with mild glaucomatous damage have similar variability for most retardation parameters.

Aged↗
PubMedDate not supplied

Topographic mapping of glaucomatous visual field defects to scanning laser polarimetry of the peripapillary nerve fiber layer.

BACKGROUND AND OBJECTIVE: To map retinal sensitivity values within glaucomatous visual field defects (VFD) to corresponding values of scanning laser polarimetry (SLP) of the peripapillary retinal nerve fiber layer using the Wirtschafter disc sector classification. METHODS: Eyes with glaucomatous VFD (N = 28) underwent SLP and Humphrey automated perimetry. The Wirtschafter disc sector classification was used to obtain SLP values corresponding to VFD. The average and modulated SLP values were calculated and correlated with VFD. RESULTS: No significant correlation was found between retinal sensitivity and the Wirtschafter disc sector SLP values, using average values (P =.904) or modulated values (P =.409). CONCLUSION: Despite use of modulation parameters customized to correspond with the Wirtschafter disc sector classification, topographic mapping of retinal sensitivity levels within glaucomatous VFD to corresponding SLP values was not possible in this group of glaucomatous eyes.

Aged↗