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Philip P Chen

Publications and source records attributed to Philip P Chen.

16 recordsLinked to original sources
PubMed2006

A multicenter, retrospective pilot study of resource use and costs associated with severity of disease in glaucoma.

OBJECTIVE: To examine resource consumption and the direct costs of treating glaucoma at different disease severity levels. DESIGN: Observational, retrospective cohort study based on medical record review. PARTICIPANTS: One hundred fifty-one records of patients with primary open-angle or normal-tension glaucoma, glaucoma suspect, or ocular hypertension (age > or =18 years) were randomly selected from 12 sites in the United States and stratified according to severity based on International Classification of Diseases, Ninth Revision, Clinical Modification codes. Patients had to have been followed up for a minimum of 5 years. Patients with concomitant ocular disease likely to affect glaucoma treatment-related resource consumption were excluded. METHODS: Glaucoma severity was assessed and assigned using a 6-stage glaucoma staging system, modified from the Bascom Palmer (Hodapp-Anderson-Parrish) system. Clinical and resource use data were collected from the medical record review. Resource consumption for low-vision care and vision rehabilitation was estimated for patients with end-stage disease based on specialist surveys. For each stage of disease, publicly available economic data were then applied to assign resource valuation and estimate patient-level direct costs from the payer perspective. MAIN OUTCOME MEASURES: Average annual resource use and estimated total annual direct cost of treatment were calculated at the patient level and stratified by stage of disease. Direct costs by specific resource types, including ophthalmology visits, glaucoma surgeries, medications, visual field examinations, and other glaucoma services, were also assessed. RESULTS: Direct ophthalmology-related resource use, including ophthalmology visits, glaucoma surgeries, and medication use, increased as disease severity worsened. Average direct cost of treatment ranged from $623 per patient per year for glaucoma suspects or patients with early-stage disease to $2511 per patient per year for patients with end-stage disease. Medication costs composed the largest proportion of total direct cost for all stages of disease (range, 24%-61%). CONCLUSIONS: The study results suggest that resource use and direct cost of glaucoma management increase with worsening disease severity. Based on these findings, a glaucoma treatment that delays the progression of disease could have the potential to significantly reduce the health economic burden of this chronic disease over many years.

Adult↗
PubMed2006

Prediction of visual field defects on standard automated perimetry by screening C-20-1 frequency doubling technology perimetry.

PURPOSE: To determine if perimetric defects, initially seen with C-20-1 frequency doubling technology (FDT) in eyes with normal standard automated perimetry (SAP), will subsequently develop on standard automated perimetry. METHODS: Review of patients considered high-risk glaucoma suspects (GS) or with ocular hypertension (OHT), who underwent one C-20-1 FDT in 1997 or 1998. An abnormal frequency doubling technology was defined in two ways, as having either at least one, or at least two abnormal locations. An abnormal standard automated perimetry was defined as fulfilling two of three modified Anderson criteria for abnormality on two consecutive tests and at final standard automated perimetry. RESULTS: Of 63 eyes (50 patients), 18 (28.6%) had >or=1 FDT defects, and 12 (19.0%) had >or=2 defects. After follow-up of 62 +/- 26 months, an abnormal standard automated perimetry developed in 5 eyes (28%) with frequency doubling technology defects at 22 +/- 13 months (28% of eyes with >or=1 defect and 42% of eyes with >or=2 FDT defects), and in 4 of 45 eyes (9%) with normal frequency doubling technology at 32 +/- 30 months. Kaplan-Meier survival analysis revealed the risk of an abnormal standard automated perimetry at 5 years with or=1 defects, and >or=2 defects, was 10.3%, 11.8%, 30.6%, and 46.4% respectively (P = 0.060 for >or=1 defects compared with no defects; P = 0.002 for >or=2 defects compared with <or=1 defect). CONCLUSIONS: Abnormal results on C-20-1 frequency doubling technology perimetry predicted glaucomatous visual field loss on standard automated perimetry in some patients in this patient population, though a relatively high false positive rate was noted. Abnormality on C-20-1 frequency doubling technology warrants close observation, and further prospective evaluation is warranted.

Aged↗
PubMed2005

Predicting subsequent visual field loss in glaucomatous subjects with disc hemorrhage using retinal nerve fiber layer polarimetry.

PURPOSE: To predict progression of visual field loss after an episode of disc hemorrhage in glaucoma patients on the basis of retinal nerve fiber layer (RNFL) GDx polarimetry measurements analyzed by wavelet-Fourier analysis (WFA). METHODS: Retrospective GDx data from 16 subjects (10 progressors and 6 non-progressors based on visual fields) obtained near the time of disc hemorrhage were analyzed to predict which patients would have visual field progression. Polarimetry scans throughout a follow-up period (31 months average) were also analyzed to compare field progression to RNFL thickness change after the hemorrhage. Mean RNFL thickness inferred from the polarimetry data at sixteen 22.5 degrees sectors at distances of 1.6, 1.7, and 1.8 disc diameters were used. Data were analyzed by applying to appropriate regions of disc hemorrhage patients a structural analysis (WFA) we had developed previously. A linear discriminant function (Fischer) was produced and a leave-one-out method using separate training and test data was used to assure validity of the results. RESULTS: Patients who subsequently progressed were successfully predicted with moderate success (sensitivity / specificity was 0.77 / 0.88 with ROC area = 0.858). A separate analysis comparing pre- and post-hemorrhage RNFL sector thickness revealed clear evidence of RNFL thinning at the inferior and superior sectors before progression of visual field. The thinning of RNFL thickness was not restricted to regions corresponding to the location of the hemorrhage. CONCLUSION: Wavelet-Fourier analysis can differentiate progressors from non-progressors with moderate accuracy. Comparison to a prior study of this same cohort emphasizes that relatively small regions must be considered (as opposed to larger quadrants) to see these significant changes in RNFL.

Aged↗
PubMed2004

Learning effect among perimetric novices with screening C-20-1 frequency doubling technology perimetry.

PURPOSE: To investigate whether perimetric novices without glaucoma demonstrate a learning effect using screening-mode frequency doubling technology perimetry. DESIGN: Prospective observational study. METHODS: The study included 101 healthy subjects who had never undergone automated perimetry and who were administered the C-20-1 version of the frequency doubling technology. Subjects who returned an abnormal or unreliable test were retested until a normal result was obtained. RESULTS: Ninety-seven subjects (96%) returned a normal examination after one test, and 99 (98%) did so after two tests. Two subjects had abnormal initial tests, and two others had unreliable tests. These four subjects required repeat (up to four) testings to return a normal test. CONCLUSIONS: A small percentage of perimetric novices will demonstrate a learning effect using C-20-1 perimetry, but this mode has high specificity appropriate for glaucoma screening.

Adolescent↗
PubMed2004

Central corneal pachymetry and visual field progression in patients with open-angle glaucoma.

PURPOSE: To investigate the association between corneal pachymetry and visual field progression in patients with chronic open-angle glaucoma. DESIGN: Retrospective case-control study. PARTICIPANTS: Eighty-eight patients with primary open-angle glaucoma, pseudoexfoliative glaucoma, pigmentary glaucoma, or normal-tension glaucoma, followed for an average of 8 years, who had visual field loss and progression as defined by modified Anderson criteria. Cases with progression were matched for race, diagnosis, and age at pachymetry with controls who did not have progression. METHODS: Progression was defined by use of the modified Anderson criteria. Central corneal thickness (CCT) was determined by ultrasound pachymetry. MAIN OUTCOME MEASURES: Visual field progression and corneal pachymetry. RESULTS: The mean CCT in patients with visual field progression was significantly lower than the mean CCT in patients who did not progress (529+/-36 mum vs. 547+/-35 mum; P = 0.02). Those with thinner CCT were more likely to progress than those with thicker CCT as identified by Cox proportional hazards regression analysis (P = 0.01; hazard ratio, 1.44 for a 40-mum thinner CCT; 95% confidence interval, 1.12-1.80), and CCT was the only risk factor identified to be significantly associated with visual field progression. CONCLUSIONS: In this case-control patient population, visual field progression in patients with open-angle glaucoma was significantly associated with thinner CCT.

Adult↗
PubMed2004

Risk and risk factors for blindness from glaucoma.

PURPOSE OF REVIEW: Estimates of blindness from glaucoma and risk factors for blindness remain of interest for all ophthalmologists. RECENT FINDINGS: Long-term retrospective studies of patients with open-angle glaucoma in developed countries have noted that progression to bilateral blindness among treated patients is relatively uncommon. Risk factors for development of blindness include advanced visual field loss at presentation and noncompliance with the treatment regimen. Age is a risk factor in some studies. Many of those with blindness are blind at presentation. Untreated rates of blindness are higher. Population-based studies of glaucoma in developing countries have highlighted the obstacles to prevention of blindness in such settings, with astonishingly high rates of blindness noted. SUMMARY: The risk of blindness from glaucoma is very high among patients in developing countries, the vast majority of whom do not know they are afflicted. When considering all glaucoma worldwide, the greatest risk factor for blindness is almost certainly being an average citizen of a developing country. Among those with open-angle glaucoma in developed countries, more advanced visual field loss at presentation and noncompliance are risk factors for development of blindness, as well as advanced age. Effective public education about glaucoma and targeted screening of those most likely to have glaucoma are necessary if the number of blind from glaucoma is to be reduced worldwide. Better treatment options for those in developing countries must also be developed.

Blindness↗
PubMed2004

Test-retest variability in glaucoma patients tested with C-20-1 screening-mode frequency doubling technology perimetry.

PURPOSE: To investigate test-retest variability in glaucoma patients tested with C-20-1 (screening) Frequency Doubling Technology (FDT) perimetry. METHODS: Thirty-one glaucoma patients with a range of visual field defects (17 with mild, 11 with moderate, and 3 with severe defects by AGIS classification) and experienced in standard automated perimetry but not FDT perimetry were prospectively recruited. The C-20-1 screening mode of FDT was consecutively administered three times. Concordance between tests for each patient was measured by presence and severity of defects for each test location. Learning and/or fatigue effects were also evaluated using FDT test scores in which number and severity of defects was graded. RESULTS: Agreement between FDT test locations averaged 88% for any defect, but only 51% for severity of defect. Although the mean test score increased slightly over the three tests, subjects did not demonstrate a statistically significant change in test score across the three testings (P = 0.975). Among 17 patients with early glaucoma (AGIS score 1-5), two returned a normal initial FDT test, and four returned a normal second FDT test. CONCLUSIONS: Using C-20-1 FDT, concordance between tests at a given test location was high for the presence of any defect, which would be important in glaucoma screening, but was only fair for severity of defect. Six of 17 patients with early glaucoma returned normal tests during testing. This group of glaucoma patients with perimetric experience did not demonstrate a significant learning or fatigue effect with FDT screening perimetry.

Aged↗
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↗