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Pamela A Sample

Publications and source records attributed to Pamela A Sample.

At least 19 recordsLinked to original sources
PubMed2004

Frequency doubling technology perimetry abnormalities as predictors of glaucomatous visual field loss.

PURPOSE: To determine whether frequency doubling technology (FDT) perimetry results predict glaucomatous visual field defects, as assessed by standard automated perimetry (SAP), in a glaucoma suspect population. DESIGN: Longitudinal observational study. METHODS: The study included 105 eyes of 105 glaucoma suspect patients, with a mean follow-up time of 41 +/- 17 months. Glaucoma suspects had either intraocular pressure (IOP) higher than or equal to 23 mm Hg or glaucomatous optic neuropathy by stereophotograph assessment. All patients had normal SAP visual fields at baseline. A baseline FDT test was performed within 3 months of the normal SAP examination. Several baseline FDT parameters and other variables (age, gender, IOP, central corneal thickness, SAP visual field indices, and stereophotograph assessment) were investigated by univariate and multivariate Cox proportional hazards models to obtain hazard ratios (HR) and identify factors that predicted which patients had SAP glaucomatous visual field loss during follow-up. RESULTS: Seventeen patients (16%) developed repeatable SAP visual field abnormality during follow-up. An abnormal FDT examination at baseline predicted the development of SAP visual field conversion in both univariate (HR = 3.17; 95% confidence interval [CI] = 1.22-8.25; P =.018) and multivariate models (Adjusted HR = 3.68; 95% CI = 1.06-12.8; P =.04). The analysis of FDT examinations during follow-up revealed that in 59% of converters the FDT abnormalities preceded SAP visual field loss by as much as 4 years. Also, the initial development of glaucomatous visual field loss as measured by SAP occurred in regions that had previously demonstrated abnormalities on FDT testing. CONCLUSION: Functional abnormalities detected by FDT perimetry were predictive of the future onset and location of SAP visual field loss among glaucoma suspect patients.

Aged↗
PubMed2004

Using unsupervised learning with variational bayesian mixture of factor analysis to identify patterns of glaucomatous visual field defects.

PURPOSE: To determine whether an unsupervised machine learning classifier can identify patterns of visual field loss in standard visual fields consistent with typical patterns learned by decades of human experience. METHODS: Standard perimetry thresholds for 52 locations plus age from one eye of each of 156 patients with glaucomatous optic neuropathy (GON) and 189 eyes of healthy subjects were clustered with an unsupervised machine classifier, variational Bayesian mixture of factor analysis (vbMFA). RESULTS: The vbMFA formed five distinct clusters. Cluster 5 held 186 of 189 fields from normal eyes plus 46 from eyes with GON. These fields were then judged within normal limits by several traditional methods. Each of the other four clusters could be described by the pattern of loss found within it. Cluster 1 (71 GON + 3 normal optic discs) included early, localized defects. A purely diffuse component was rare. Cluster 2 (26 GON) exhibited primarily deep superior hemifield defects, and cluster 3 (10 GON) held deep inferior hemifield defects only or in combination with lesser superior field defects. Cluster 4 (6 GON) showed deep defects in both hemifields. In other words, visual fields within a given cluster had similar patterns of loss that differed from the predominant pattern found in other clusters. The classifier separated the data based solely on the patterns of loss within the fields, without being guided by the diagnosis, placing 98.4% of the healthy eyes within the same cluster and spreading 70.5% of the eyes with GON across the other four clusters, in good agreement with a glaucoma expert and pattern standard deviation. CONCLUSIONS: Without training-based diagnosis (unsupervised learning), the vbMFA identified four important patterns of field loss in eyes with GON in a manner consistent with years of clinical experience.

Algorithms↗
PubMed2004

Confocal scanning laser ophthalmoscopy classifiers and stereophotograph evaluation for prediction of visual field abnormalities in glaucoma-suspect eyes.

PURPOSE: To determine whether Heidelberg Retina Tomograph (HRT; Heidelberg Engineering, Dossenheim, Germany) classification techniques and investigational support vector machine (SVM) analyses can detect optic disc abnormalities in glaucoma-suspect eyes before the development of visual field abnormalities. METHODS: Glaucoma-suspect eyes (n = 226) were classified as converts or nonconverts based on the development of repeatable (either two or three consecutive) standard automated perimetry (SAP)-detected abnormalities over the course of the study (mean follow-up, approximately 4.5 years). Hazard ratios for development of SAP abnormalities were calculated based on baseline classification results, follow-up time, and end point status (convert, nonconvert). Classification techniques applied were HRT classification (HRTC), Moorfields Regression Analysis, forward-selection optimized SVM (SVM fwd) and backward elimination-optimized SVM (SVM back) analysis of HRT data, and stereophotograph assessment. RESULTS: Univariate analyses indicated that all classification techniques were predictors of the development of two repeatable abnormal SAP results, with hazards ratios (95% confidence interval [CI]) ranging from 1.32 (1.00-1.75) for HRTC to 2.0 (1.48-2.76) for stereophotograph assessment (all P < or = 0.05). Only SVM (SVM fwd and SVM back) analysis of HRT data and stereophotograph assessment were univariate predictors of the development of three repeatable abnormal SAP results, with hazard ratios (95% CI) ranging from 1.73 (1.16-2.82) for SVM fwd to 1.82 (1.19-3.12) for SVM back (both P < 0.007). Multivariate analyses including each classification technique individually in a model with age, baseline SAP pattern standard deviation [PSD], and baseline IOP indicated that all classification techniques except HRTC (P = 0.06) were predictors of the development of two repeatable abnormal SAP results with hazards ratios ranging from 1.30 (0.99, 1.73) for HRTC to 1.90 (1.37, 2.69) for stereophotograph assessment. Only SVM (SVM fwd and SVM back) analysis of HRT data and stereophotograph assessment were significant predictors of the development of three repeatable abnormal SAP results in multivariate analyses; hazard ratios of 1.57 (1.03, 2.59) and 1.70 (1.18, 2.51), respectively. SAP PSD was a significant predictor of two repeatable abnormal SAP results in multivariate models with all classification techniques, with hazard ratios ranging from 3.31 (1.39, 7.89) to 4.70 (2.02, 10.93) per 1-dB increase. CONCLUSIONS: HRT classifications techniques and stereophotograph assessment can detect optic disc topography abnormalities in glaucoma-suspect eyes before the development of SAP abnormalities. These data support strongly the importance of optic disc examination for early glaucoma diagnosis.

Adult↗
PubMed2003

Increased detection rate of glaucomatous visual field damage with locally condensed grids: a comparison between fundus-oriented perimetry and conventional visual field examination.

OBJECTIVE: To compare detection rates of glaucomatous visual field defects (VFDs) between the conventional 6 degrees x 6 degrees stimulus grid and locally condensed target arrangements in morphologically suspicious regions. METHODS: A total of 66 eyes of 66 patients with glaucoma or patients suspected of having glaucoma (34 females and 32 males; age range, 14-85 years) were enrolled in this study. Individual, local target condensation was realized by fundus-oriented perimetry (FOP) using a campimeter and compared with the results of conventional automated perimetry (CAP), obtained with the Humphrey Field Analyzer (30-2 grid). RESULTS: Twenty-three of the 66 patients showed normal findings with both methods; 27 had concordantly pathological results. In 15 patients we obtained normal findings with CAP, whereas FOP revealed early glaucomatous VFDs. Only one patient showed VFDs with CAP, whereas FOP results were normal. Scotoma detection rates significantly differed between the 2 methods (P<.001, sign test). Test duration with FOP was more than doubled compared with CAP. When considering only FOP points coinciding with the 6 degrees spacing of the 30-2 grid, there was no longer a significant difference between FOP and CAP (P>.25, sign test). This indicated that the target pattern, rather than the perimetric device, was most relevant for detecting glaucomatous VFDs. Follow-up throughout a series of 3 subsequent sessions at 6-month intervals revealed repeatable results in more than two thirds of all eyes for both FOP and CAP. CONCLUSIONS: Fundus-oriented perimetry that uses individually condensed test grids significantly increases the detection rate of glaucomatous VFDs in morphologically conspicuous areas compared with CAP using equidistant (6 degrees x 6 degrees) target arrangements. Repeatability is comparable between both methods.

Adolescent↗
PubMed2003

Corneal thickness measurements and visual function abnormalities in ocular hypertensive patients.

PURPOSE: It has been suggested that a considerable subset of patients currently classified as having ocular hypertension may have thicker than average corneas that result in an overestimation of the true intraocular pressure (IOP). As a consequence, ocular hypertension patients with greater corneal thickness may be at a lower risk for functional damage, such as that detected by short-wavelength automated perimetry (SWAP). The purpose of this study was to evaluate the frequency of SWAP deficits in ocular hypertension patients and to correlate these findings with corneal thickness measurements in the same patients. DESIGN: Cross-sectional observational study. METHODS: Sixty-eight ocular hypertension patients with normal optic disks and 63 normal subjects were included in the study. All participants underwent standard automated perimetry (SAP), SWAP, and central corneal thickness measurements using ultrasound pachymeter. Central corneal thickness measurements in ocular hypertension patients with abnormal visual field test results were compared with central corneal thickness measurements in ocular hypertension patients with normal visual field results. In addition, central corneal thickness measurements in ocular hypertension patients were compared with central corneal thickness measurements in normal subjects. RESULTS: Sixteen of 68 patients with ocular hypertension (24%) demonstrated SWAP abnormalities, whereas four of 68 (6%) showed a deficit on SAP. The mean central corneal thickness in ocular hypertension patients with abnormal SWAP results was significantly lower than the mean central corneal thickness in ocular hypertension patients with normal SWAP results (545 +/- 25 microm vs 572 +/- 35 microm; P =.006). The mean central corneal thickness in the normal group was 557 +/- 33 microm. The mean central corneal thickness in ocular hypertension patients with normal SWAP results was significantly higher than in normal subjects (P =.02). There was no significant difference between mean central corneal thickness in normal subjects and in ocular hypertension patients with abnormal SWAP results (P =.19). CONCLUSIONS: The patients classified as having ocular hypertension but with visual field loss detected by SWAP had significantly lower central corneal thickness measurements than the ocular hypertension patients with normal visual field results. These results suggest that central corneal thickness should be taken into account when assessing risk for the development of glaucomatous damage among ocular hypertension patients.

Aged↗
PubMed2003

Structure and function evaluation (SAFE): II. Comparison of optic disk and visual field characteristics.

PURPOSE: To evaluate the relationship between glaucomatous structural damage to the optic nerve and development of visual field loss with standard automated perimetry (SAP) and short wavelength automated perimetry (SWAP). DESIGN: Cohort study. METHODS: Patients with elevated intraocular pressure and normal SAP visual fields were enrolled in this prospective study. Stereo optic disk photographs, SAP, and SWAP visual fields were obtained annually over a period of 4 or more years. Trained readers evaluated baseline and follow-up optic disk photographs for evidence of glaucomatous damage. Standard automated perimetry and SWAP examinations were evaluated according to previously validated criteria for development of confirmed visual field changes. RESULTS: Two-hundred ninety-five subjects (479 eyes) were enrolled. Following masked assessment of stereo photographs by an optic disk reading center, 272 of the 479 eyes were judged to have glaucomatous optic neuropathy at the time of study entry. Depending on the criteria employed, approximately 10% to 17.5% of all eyes developed confirmed visual field loss for SAP (conversions). Of the conversions, 75% to 80% had baseline glaucomatous optic disk damage, whereas normal and glaucomatous optic disks were equally divided (50%) among the nonconversion eyes. This difference was statistically significant (P <.003). Depending on the criteria employed, 4% to 12% of the eyes had confirmed SWAP deficits at baseline, and 4% to 8% developed confirmed SWAP defects at a follow-up examination. There was a greater percentage of eyes with a glaucomatous optic neuropathy in the group with SWAP deficits (75%-100%) than for those eyes in which SWAP remained normal (45%-60%). Some of these differences were statistically significant (P <.05). CONCLUSIONS: A strong relationship exists between glaucomatous optic disk damage at study entry and the subsequent development of a confirmed glaucomatous SAP visual field defect. A higher percentage of glaucomatous optic disks were also found in patients with SWAP deficits at baseline and in those who later developed SWAP deficits. These findings support the premise that a glaucomatous optic disk is predictive of the subsequent development of glaucomatous visual field loss.

Follow-Up Studies↗
PubMed2003

Corneal thickness as a risk factor for visual field loss in patients with preperimetric glaucomatous optic neuropathy.

PURPOSE: To determine whether central corneal thickness (CCT) is a risk factor for visual field loss development among patients diagnosed with preperimetric glaucomatous optic neuropathy (GON). DESIGN: Observational cohort study. METHODS: The study included 98 eyes of 98 patients with GON, with a mean follow-up time of 4.3 +/- 2.7 years. Diagnosis of GON was based on masked assessment of optic disk stereophotographs. All patients had normal standard automated perimetry visual fields at baseline. Criteria for visual field abnormality were derived from a prior study. Several clinical factors (CCT, intraocular pressure, vertical cup-to-disk ratio, refraction, age, gender, family history of glaucoma, high blood pressure, cardiovascular disease, and migraine) were investigated to ascertain whether there is an association with development of repeatable visual field loss. Cox proportional hazards models were used to obtain hazard ratios (HR) and identify factors that predicted which individuals developed glaucomatous visual field loss during the follow-up period. RESULTS: Thirty-four patients (35%) developed repeatable visual field abnormality during follow-up. In multivariate analysis, risk factors that predicted the development of visual field loss were a thinner CCT (adjusted HR = 1.62/40 microm thinner; P =.023; 95% confidence interval [CI]: 1.07-2.45), higher baseline intraocular pressure (adjusted HR = 1.07/mm Hg; P =.022; 95% CI: 1.01-1.14), and larger baseline vertical cup-to-disk ratio (adjusted HR = 1.63/0.1 larger; P =.009; 95% CI: 1.13-2.35). The mean +/- standard deviation CCT of GON patients who developed visual field loss was 543 +/- 36 microm compared with 565 +/- 35 microm of those who did not develop visual field abnormalities (P =.005, Student t test). CONCLUSIONS: Central corneal thickness is a risk factor for development of visual field loss among patients diagnosed with preperimetric GON. It is important to consider CCT when establishing target intraocular pressure of patients with GON.

Cohort Studies↗
PubMed2003

Relationship of optic disk topography and visual function in patients with large cup-to-disk ratios.

PURPOSE: To determine if topographic differences exist between large cup-to-disk ratio (C/D) eyes with standard achromatic automated perimetry (SAP) abnormalities and those with only short-wavelength automated perimetry (SWAP) abnormalities. DESIGN: Cross-sectional study. METHODS: The setting was a referral university-based clinical practice. We selected one eye of 72 patients with a vertical C/D of at least 0.8 by ophthalmoscopy. Patients performed SWAP, SAP, and confocal scanning laser ophthalmoscopy. We compared optic disk topography in eyes with and without visual field abnormalities and controlled for the influence of disk area. RESULTS: Disk area was a confounder of many topographic measures. After controlling for disk area, eyes with abnormal SAP had differences in rim volume, cup shape, rim area, retinal nerve fiber layer thickness, and retinal nerve fiber layer cross-sectional area when compared with eyes with normal SAP (P <.05). Rim volume and rim area were different in the SWAP comparison (P <.05). CONCLUSIONS: Investigators should control for disk area when evaluating topographic measures by confocal scanning laser ophthalmoscopy. In eyes with a large C/D, optic disk topography is more glaucomatous in eyes with SAP abnormalities than in those with only SWAP abnormalities. Eyes with large C/D and only SWAP abnormalities may have fewer glaucomatous optic disk changes than such eyes with SAP abnormalities. This indicates that SWAP is likely to correspond to abnormalities in optic disk topography at an earlier stage of glaucomatous optic neuropathy than SAP. Therefore, clinicians should consider SWAP testing in glaucoma suspects to detect glaucomatous visual field loss at an earlier stage of structural loss.

Adult↗
PubMed2003

Evaluating several sources of variability for standard and SWAP visual fields in glaucoma patients, suspects, and normals.

PURPOSE: To quantify factors affecting test-retest variability of threshold measurements over a series of 3 serial visual fields (VF). DESIGN: Prospective comparative observational study. PARTICIPANTS: Forty-one normals, 10 suspects and 35 stable glaucoma patients. METHODS: All subjects performed 3 standard and 3 short-wavelength automated perimetry (SWAP) VFs. At each VF location, severity (defined as age-corrected total deviation) and test-retest variability (TRV), defined as the standard deviation of 3 serial threshold values, were calculated. A multiple regression model (constructed separately for standard VF and SWAP) incorporated 13 factors: severity, location, eccentricity, study group, diagnosis, superior versus inferior hemifield, nasal versus temporal hemifield, one-versus-two thresholds, age, mean pupil size, pupil size variability, between-subject variation, and residual variation. MAIN OUTCOME MEASURES: Variability in threshold sensitivity VF values. RESULTS: Mean TRV (+/- standard deviation) for normal, suspect and glaucoma eyes, respectively, was: 1.28 +/- 0.87, 1.53 +/- 1.04 and 2.20 +/- 1.79 dB for standard VF, and 1.87 +/- 1.35, 1.86 +/- 1.24 and 2.68 +/- 1.85 dB for SWAP. The contribution of each factor to the model for standard VF and SWAP (SWAP in parentheses) were: severity 15.5% (6.9%); location 2.7% (4.1%); eccentricity 1.1% (0.64%); diagnosis 2.9% (5.9%); "superior versus inferior" hemifield 0.17% (1.7%); "nasal versus temporal" hemifield 0.06% (0.02%); one-versus-two thresholds 0.04% (0.16%); age 0.1% (0.06%); mean pupil size 0.59% (0.1%); pupil size variability 3.2% (2.8%); between-subject 8.0% (13.5%) and residual variation 61.0% (66.6%). Excluding between-subject and residual variation, the 11-factor model was able to account for less than one third of the variability seen in both standard VF and SWAP. CONCLUSIONS: Severity of defect and between subject variation exerted the largest effect on TRV. However, even if all 11 factors could be adjusted for, it would reduce the magnitude of TRV by only 30%. More work is needed to reduce the remaining variability inherent in psychophysical testing and to better understand the intrinsic physiological variability present both in healthy and diseased eyes. It is possible that a larger number of VFs used for the calculation of TRV might further reduce the magnitude of the remaining variability found in this study.

Adult↗
PubMed2003

Corneal thickness measurements and frequency doubling technology perimetry abnormalities in ocular hypertensive eyes.

OBJECTIVE: It has been suggested that some patients currently diagnosed with ocular hypertension (OHT) may have thicker than average corneas that result in an overestimation of their true intraocular pressure. Consequently, patients with OHT with greater corneal thickness may be at a lower risk for functional glaucomatous damage, including visual field loss measured with frequency doubling technology (FDT) perimetry. The purpose of this study was to evaluate the frequency of FDT perimetry deficits in patients with OHT and to correlate these findings with central corneal thickness (CCT) measurements. DESIGN: Observational case control study. PARTICIPANTS AND CONTROLS: Sixty-five patients with OHT with normal optic discs and normal standard achromatic automated perimetry (SAP) visual fields and 52 normal control subjects. METHODS: All participants underwent SAP, FDT perimetry, and CCT measurements using ultrasound pachymetry. MAIN OUTCOME MEASURES: CCT measurements in patients with OHT with abnormal repeatable FDT test results were compared with CCT measurements in patients with OHT with normal FDT results. In addition, CCT measurements in patients with OHT were compared with CCT measurements in normal control subjects. RESULTS: Fourteen of 65 patients with OHT (21.5%) demonstrated repeatable FDT abnormalities. The mean CCT of patients with OHT with abnormal FDT results was significantly lower than the mean CCT of patients with OHT with normal FDT results (542+/-35 microm versus 575+/-35 microm; P = 0.003). The mean CCT in the normal control group was 556+/-36 microm. The mean CCT in patients with OHT with normal FDT results was significantly higher than in normal subjects (P = 0.008). No statistically significant difference was found between mean CCT in normal subjects and in patients with OHT with abnormal FDT results (P = 0.18). CONCLUSIONS: Patients currently diagnosed with OHT, but with visual field loss detected by FDT perimetry, had significantly lower CCT measurements than patients with OHT with normal FDT results. These findings suggest that patients with OHT with thinner corneas are more likely to develop early glaucomatous functional damage and that CCT measurements should be taken into account when assessing risk for the development of glaucoma among OHT subjects.

Case-Control Studies↗
PubMed2003

Retinal nerve fiber layer thickness measured with optical coherence tomography is related to visual function in glaucomatous eyes.

PURPOSE: To determine the relationship between areas of glaucomatous retinal nerve fiber layer thinning identified by optical coherence tomography and areas of decreased visual field sensitivity identified by standard automated perimetry in glaucomatous eyes. DESIGN: Retrospective observational case series. PARTICIPANTS: Forty-three patients with glaucomatous optic neuropathy identified by optic disc stereo photographs and standard automated perimetry mean deviations >-8 dB were included. METHODS: Participants were imaged with optical coherence tomography within 6 months of reliable standard automated perimetry testing. MAIN OUTCOME MEASURES: The location and number of optical coherence tomography clock hour retinal nerve fiber layer thickness measures outside normal limits were compared with the location and number of standard automated perimetry visual field zones outside normal limits. Further, the relationship between the deviation from normal optical coherence tomography-measured retinal nerve fiber layer thickness at each clock hour and the average pattern deviation in each visual field zone was examined by using linear regression (R(2)). RESULTS: The retinal nerve fiber layer areas most frequently outside normal limits were the inferior and inferior temporal regions. The least sensitive visual field zones were in the superior hemifield. Linear regression results (R(2)) showed that deviation from the normal retinal nerve fiber layer thickness at optical coherence tomography clock hour positions 6 o'clock, 7 o'clock, and 8 o'clock (inferior and inferior temporal) was best correlated with standard automated perimetry pattern deviation in visual field zones corresponding to the superior arcuate and nasal step regions (R(2) range, 0.34-0.57). These associations were much stronger than those between clock hour position 6 o'clock and the visual field zone corresponding to the inferior nasal step region (R(2) = 0.01). CONCLUSIONS: Localized retinal nerve fiber layer thinning, measured by optical coherence tomography, is topographically related to decreased localized standard automated perimetry sensitivity in glaucoma patients.

Adult↗
PubMed2003

Short-wavelength automated perimetry.

Short-wavelength automated perimetry (SWAP) is a visual field test designed to assess the short-wavelength sensitive color system by isolating the blue-yellow pathway. SWAP is a powerful clinical tool able to detect visual field deficits 3 to 5 years before standard automated perimetry (white-on-white) in most glaucoma patients, and progression of visual field defects up to 3 years earlier. SWAP deficits are predictive of the onset and location of future visual field loss, and they correlate well with structural damage associated with glaucoma. The main disadvantage of SWAP remains the longer testing time required. In the clinic, it is recommended that SWAP be performed on patients who are at higher risk for glaucoma. Although SWAP was originally developed to detect visual loss in glaucoma patients, it is also useful for patients with diabetic retinopathy and maculopathy, optic neuropathies, vision loss associated with HIV, migraine, and multiple sclerosis. More sensitive psychophysical tests of visual function, such as SWAP, can significantly shorten clinical trials and aid in the validation of new therapeutic approaches.

Color Perception↗
PubMed2002

The structure-function relationship in eyes with glaucomatous visual field loss that crosses the horizontal meridian.

OBJECTIVE: To evaluate the relationship between visual field loss and glaucomatous optic discs in eyes in which field loss spreads across the horizontal meridian. SUBJECTS AND METHODS: Ninety-six patients with glaucoma (9 advanced, 60 moderate, and 27 early) with 2 successive abnormal fields were included. Standard achromatic automated perimetry defects were identified with a nerve fiber bundle map to identify abnormal sectors. Crossover was present if the superior and inferior sectors at the horizontal meridian (nasal, central, or temporal) were both abnormal. Optic disc damage was assessed by masked grading of simultaneous stereophotographs. RESULTS: Only 30% (29) of glaucomatous eyes showed crossover, and only 2 of those eyes had early loss. The most frequent pattern of visual field loss (41% of eyes) was single hemifield damage with defects in contiguous sectors. Regardless of the pattern or severity of visual loss, most eyes (66 [69%] of 96) had both superior and inferior optic disc damage. CONCLUSIONS: Early glaucomatous visual field loss rarely crosses the horizontal meridian, but defects in both hemifields at the horizontal meridian are more common in more advanced field loss. In 26 (90%) of 29 eyes with crossover, it could be explained by changes at the optic nerve head.

Adult↗
PubMed2002

Structure and function evaluation (SAFE): I. criteria for glaucomatous visual field loss using standard automated perimetry (SAP) and short wavelength automated perimetry (SWAP).

PURPOSE: To develop criteria for detecting glaucomatous visual field loss for standard automated perimetry (SAP) and short wavelength automated perimetry (SWAP). DESIGN: Longitudinal observational study. METHODS: Three populations were evaluated: (1) 348 normal subjects (348 eyes) were tested to develop normative databases and statistical analysis packages for SAP and SWAP. (2) An independent group of 47 normal subjects (94 eyes) with 4 years of longitudinal follow-up was evaluated to determine specificity of different criteria. (3) A group of 298 patients (479 eyes) with elevated intraocular pressure and normal baseline SAP visual fields were evaluated to determine the sensitivity of different criteria for detecting early glaucomatous visual field loss. RESULTS: Six criteria demonstrated high specificity for correctly identifying eyes with normal visual fields (98%-100%) for both SAP and SWAP: (1) a pattern standard deviation (PSD) worse than the normal 1% level, (2) a glaucoma hemifield test (GHT) "outside normal limits," (3) one hemifield cluster worse than the normal 1% level, (4) two hemifield clusters worse than the normal 5% level, (5) four abnormal (P <.05) locations, (6) five abnormal locations (P <.05) on the pattern deviation probability plot. For all criteria, confirmation on a second visual field was required for high specificity. The GHT "outside normal limits," two hemifield clusters worse than the normal 5% level and four abnormal (P <.05) test locations on the pattern deviation probability plot provided the highest percentages of conversion from a normal to a glaucomatous visual field. CONCLUSIONS: Criteria based on the GHT, GHT hemifield clusters, and the pattern deviation probability plot provide high sensitivity and specificity for detecting early glaucomatous visual field changes.

Adolescent↗
PubMed2002

Progression of visual field loss in untreated glaucoma patients and glaucoma suspects in St. Lucia, West Indies.

PURPOSE: A 1986-1987 survey found 8.8% prevalence of open-angle glaucoma in the black population of St. Lucia, West Indies. This follow-up study assessed visual field loss progression in untreated glaucoma patients and glaucoma suspects 10 years later. DESIGN: Cohort study. METHODS: Subjects were 205 glaucoma patients and suspects; 1987 data included age, sex, visual acuity, and visual fields measured by automated threshold perimetry (Humphrey C 30-2 test), and 1997 data included intraocular pressure, visual acuity, and visual fields measured by the same test. Exclusion criteria included field unreliability, field improvement due to vision improvement, nonglaucomatous vision deterioration, glaucoma treatment since 1988, and scoring of a visual field as end stage in 1987. Visual fields were scored by algorithms for the Advanced Glaucoma Intervention Study (AGIS) and Collaborative Initial Glaucoma Treatment Study (CIGTS). RESULTS: By AGIS criteria, 55% of 146 right eyes and 52% of 141 left eyes showed progression of visual field loss. In linear regressions, progression severity was unassociated with sex, intraocular pressure, or baseline visual field score, but was positively associated with age (P <.001, right; P =.002, left). The cumulative probability of reaching end stage in 10 years in at least one eye was approximately 16% by AGIS criteria. By CIGTS criteria, 73% of 146 right eyes and 72% of 141 left eyes progressed. CONCLUSIONS: These data provide a unique opportunity to study progression of untreated glaucoma. The percentage of eyes showing visual field loss progression and the percentage reaching end stage were considerably higher than in studies of visual field progression in treated eyes.

Adult↗
PubMed2002

Infrequent confirmation of visual field progression.

OBJECTIVE: To evaluate the effects of the repeatability criteria on the detection of change in visual fields by six progression algorithms used in standard automated perimetry. DESIGN: Retrospective, observational case series PARTICIPANTS: Fifty-one glaucoma patients, each with multiple visual fields performed between May 1990 and December 1998, were included. METHODS: Each patient's set of visual fields were analyzed using the glaucoma change probability, the Early Manifest Glaucoma Trial (EMGT) algorithm, a modified glaucoma change probability score, a modified EMGT score, the Advanced Glaucoma Intervention Study algorithm, and the Collaborative Initial Glaucoma Treatment Study algorithm. MAIN OUTCOME MEASURES: The effects of repeatability on the detection of field change, the level of agreement among algorithms, as well as the number of eyes identified as changed with each algorithm, were assessed. RESULTS: Mean follow-up was 34 months (range, 12-87 months). The average percentage of eyes with change based on three consecutive follow-up fields was 8.2% (4.0%-12.5%). However, of those showing change on the initial follow-up, this change from baseline was observed in subsequent examinations on average in 23% (18%-33%), depending on the algorithm. When change was based on just one field, four of the six algorithms noted a significantly greater number of eyes with change. The algorithms, however, did not differ significantly when confirmation of field change required two versus three consecutive follow-up visual fields. CONCLUSIONS: Although current algorithms may help identify change, there are inconsistencies among them. We found that requiring repeatable change from baseline significantly reduces the number of changed eyes identified with each subsequent follow-up field. Identification and confirmation of change in visual fields plays an important role in helping to identify true glaucoma progression; however, the specific methods to do so have yet to be determined.

Adult↗
PubMed2002

Comparison of machine learning and traditional classifiers in glaucoma diagnosis.

Glaucoma is a progressive optic neuropathy with characteristic structural changes in the optic nerve head reflected in the visual field. The visual-field sensitivity test is commonly used in a clinical setting to evaluate glaucoma. Standard automated perimetry (SAP) is a common computerized visual-field test whose output is amenable to machine learning. We compared the performance of a number of machine learning algorithms with STATPAC indexes mean deviation, pattern standard deviation, and corrected pattern standard deviation. The machine learning algorithms studied included multilayer perceptron (MLP), support vector machine (SVM), and linear (LDA) and quadratic discriminant analysis (QDA), Parzen window, mixture of Gaussian (MOG), and mixture of generalized Gaussian (MGG). MLP and SVM are classifiers that work directly on the decision boundary and fall under the discriminative paradigm. Generative classifiers, which first model the data probability density and then perform classification via Bayes' rule, usually give deeper insight into the structure of the data space. We have applied MOG, MGG, LDA, QDA, and Parzen window to the classification of glaucoma from SAP. Performance of the various classifiers was compared by the areas under their receiver operating characteristic curves and by sensitivities (true-positive rates) at chosen specificities (true-negative rates). The machine-learning-type classifiers showed improved performance over the best indexes from STATPAC. Forward-selection and backward-elimination methodology further improved the classification rate and also has the potential to reduce testing time by diminishing the number of visual-field location measurements.

Artificial Intelligence↗