Comparison of visual field sensitivities between the Medmont automated perimeter and the Humphrey field analyser

Background: Two commonly used perimeters in Australia and in many parts of Asia are the Humphrey field analyser II (HFA) and the Medmont automated perimeter (MAP). Each device maps the incremental light threshold of the visual field and describes the sensitivity at each point in ‘decibels’ (dB); however, these values are not interchangeable between devices. This study was designed to compare directly the sensitivity values of HFA and MAP visual fields. Methods: Sixty‐three subjects who had suspected glaucoma, ocular hypertension or glaucoma, or were normal controls were recruited selectively. One eye from each patient was tested with the MAP and HFA in random order on the same day. Corresponding points between the two tests were identified and their sensitivities were compared. Results: Sensitivities between MAP and HFA were strongly correlated (r² = 0.45; P < 0.0001), with the relationship between them being described by the linear equation: MAP = 0.75*(HFA) ? 0.87. On average, across the entire field MAP sensitivities were 7.4 dB (standard deviation 4.6 dB) lower than HFA. However, this relationship was modified by eccentricity and field sensitivity loss. Conclusion: Visual field sensitivities for MAP and HFA may be related by a linear relationship. Theoretical and clinical predictions that this difference may be on average approximately 5 dB have been confirmed.     

Comparison of local differential luminance sensitivity (dls) between Oculus Twinfield Perimeter and Humphrey Field Analyzer 630 (HFA I) in normal volunteers of varying ages]

PURPOSE: Purpose of this study was to compare age-corrected normal values of differential luminance sensitivity (dls) of the Oculus Twinfield Perimeter with those of the Humphrey Field Analyzer 630 (HFA I). Furthermore, naso-temporal and superior-inferior asymmetries in the central visual field were analyzed. METHODS: 72 ophthalmologically normal volunteers, 12 per decade, were examined with both perimeters using a 4-2 dB bracketing strategy with two reversals for threshold estimation. A biometric model, which fits a hill of vision to the data, was developed. The age-related hills, created by the model, were compared between the instruments and analyzed for asymmetries. RESULTS: The normal dls values for the Twinfield perimeter were about 1.5 dB above those of the HFA I. The shape of the hill in regard to slope in corresponding locations did not differ substantially. The decline of local differential luminance sensitivity showed a nonlinear correlation to age: it remained almost constant up to the 4th decade, with a steeper decline beyond that age. A naso-temporal as well as a superior-inferior asymmetry was found. Along the vertical meridian, the slope of the hill was steeper in the superior part than in the inferior. At an excentricity of 20 degrees we found a superior-inferior difference of 2.1 dB for the HFA and of 1.8 dB for the Twinfield perimeter benefitting the inferior meridian. Along the horizontal meridian there was a distinct difference in regard to the shape of the hill. The sensitivity was greater in the temporal half of the visual field than in the nasal. At an excentricity of 30 degrees, the difference was about 2.75 dB for the HFA and 2.5 dB for the Twinfield perimeter. These asymmetries seem to appear in all age groups. Unfortunately, the exact influence of age on the appearing asymmetries cannot be quantified by the used model. CONCLUSION: The normal dls values benefit the Twinfield for about 1.5 dB compared to the HFA. There seems to be a critical age of about 40 - 50 years, beyond which a decline of dls becomes manifest.     

A comparison of perimetric results with the Medmont and Humphrey perimeters

BACKGROUND: The Humphrey field analyser (HFA), Humphrey-Zeiss frequency doubling perimeter, and the Medmont automated perimeter (MAP) are three commonly used automated perimeters with threshold achromatic methodologies. Visual field loss may be detected earlier with strategies that target cell lines with reduced redundancy or which suffer selective damage. METHOD: To compare these three perimeters, 63 subjects who were glaucoma suspects, ocular hypertensives, glaucoma patients, or normal controls were recruited selectively. All subjects underwent testing using MAP central threshold, MAP flicker perimetry, HFA full threshold, HFA SITA perimetry, HFA short wavelength perimetry (SWAP), and frequency doubling perimetry (FDP). After visual field testing, equivalent tests were compared: MAP central threshold with HFA full threshold and HFA SITA perimetry; Medmont flicker perimetry with HFA SWAP and FDP. RESULTS: On analysis of the MAP central threshold a kappa statistic and an area under the receiver operator curve (AUC) of 0.90 and 0.94, respectively, were found compared with HFA full threshold strategies, and 0.87 and 0.92 respectively, compared with HFA SITA. For MAP flicker a kappa statistic and an AUC of 0.65 and 0.81, respectively, were found compared with HFA SWAP and 0.87 and 0.96, respectively, compared with FDP. A quadrant analysis and comparison of mean defect between tests was also highly significant. CONCLUSION: Medmont and Humphrey perimeters correlated well; both may be used for clinical and research purposes with similar confidence.     

Comparison of imo and Humphrey field analyzer perimeters in glaucomatous eyes

AIM: To compare the imo perimeter, a new portable head-mounted perimeter unit that enables both eyes to be examined quickly and simultaneously, with the Humphrey field analyzer (HFA) perimeter to investigate correlations and their diagnostic ability in glaucomatous eyes. METHODS: The performance of the equipment in 128 glaucomatous eyes and 40 normal eyes were tested. We investigated the correlations of mean deviation, pattern standard deviation, visual field index, and the sensitivity. RESULTS: Measurements of mean deviation (r=0.886, P<0.001), pattern standard deviation (r=0.814, P<0.001), and visual field index (r=0.871, P<0.001) in both perimeters were strongly and positively correlated. The sensitivities in the imo perimeter were 80.5% for mean deviation, 81.2% for pattern standard deviation, and 80.5% in visual field index; those in the HFA were 63.3% for mean deviation, 74.5% for pattern standard deviation, and 80.5% for visual field index. Both perimeters demonstrated high diagnostic ability. CONCLUSION: The parameters by the imo and HFA in glaucomatous eyes show strong positive correlations with favorable sensitivity, specificity, and diagnostic ability. However, the difference between imo and HFA results increases with the increase in visual field disturbance.     

Between-algorithm, between-individual differences in normal perimetric sensitivity: full threshold, FASTPAC, and SITA. Swedish Interactive Threshold algorithm

PURPOSE: To determine the between-algorithm differences in perimetric sensitivity for the Swedish Interactive Threshold algorithm (SITA) Standard, SITA Fast, FASTPAC, and Full Threshold algorithms; to determine the between-subject, between-algorithm differences in the magnitude of the normal variation in sensitivity. METHODS: The sample comprised 50 normal subjects (mean age, 52.9 +/- 18.5 years) experienced in automated perimetry. One randomly assigned eye was examined at three visits with Program 30-2 of the Humphrey Field Analyzer (HFA). The first visit was a familiarization session. A two-period crossover design with order randomization within visits was used over the second and third visits. SITA Standard, SITA Fast, and HFA 640 Full Threshold were administered during one visit. FASTPAC and HFA 750 Full Threshold were administered during the remaining visit. RESULTS: Group mean Mean Sensitivity was 0.8 dB higher for SITA Standard than for Full Threshold (P < 0.001) and 1.3 dB higher for SITA Fast than for Full Threshold (P < 0.001). A similar trend was found between SITA and FASTPAC. The group mean Mean Sensitivity for SITA Fast was 0.5 dB higher than for SITA Standard (P < 0.001). The pointwise between-algorithm difference in sensitivity was similar for all algorithms. The pointwise between-algorithm, between-subject variability was lower for SITA. The examination durations for SITA Fast and SITA Standard were half those for FASTPAC and Full Threshold; SITA Fast was 41% that of SITA Standard (P < 0.001). CONCLUSIONS: SITA produced marginally higher mean mean sensitivity compared with that of existing algorithms and markedly reduced examination duration. The reduced between-subject variability of SITA should result in narrower confidence limits for definition of normality.     

Threshold equivalence between perimeters

To determine equivalence between perimeters, 49 eyes of 35 subjects underwent static threshold testing of the central 30 degrees twice on each of three automated perimeters and twice by manual kinetic threshold testing with the Goldmann perimeter. The Octopus-Humphrey difference was 3.3 dB (2.3 dB in the upper two rows for programs 32 and 30-2). The Dicon-Octopus difference was 3.5 dB and the Dicon-Humphrey, 6.5 dB. The I4e stimulus of the Goldmann perimeter was equivalent to 17.1 dB, 13.6 dB, and 10.8 dB on the Humphrey, Octopus, and Dicon perimeters, respectively. The III4e stimulus of the Goldmann perimeter, used for visual impairment determination, was roughly equivalent to 7 to 10 dB, 4 to 7 dB, and 0 to 6 dB on the Humphrey, Octopus, and Dicon perimeters, respectively. The prediction when converting from one instrument to another was only 10% less reliable than the ability of a perimeter to predict the values on a second examination with the same perimeter. Validity of the conversion formulas was confirmed by the age-corrected normal values available for the Octopus, Humphrey, and Goldmann perimeters.     

Agreement in the detection of chiasmal and postchiasmal visual field defects between imo binocular random single-eye test and Humphrey monocular test

Purpose

To compare the ability of imo binocular random single-eye test (BRSET) to detect visual field (VF) defects due to chiasmal and postchiasmal lesions (C/PCLs) with a Humphrey Field Analyzer (HFA) monocular test.

Study design

Prospective multicenter study

Methods

This study enrolled 40 patients with C/PCLs and measured their VFs using both imo BRSET and HFA monocular test. The VFs were classified into three groups using the cluster criterion: 1) bitemporal group, 2) homonymous group, and 3) others. The agreement and correlation of VF results between imo and HFA were analyzed using the Bland–Altman plot and Spearman correlation coefficient.

Results

The VFs of 34 patients were analyzed and classified. There were 13 patients in the bitemporal, 6 in the homonymous, and 15 in the others group. BRSET showed a significantly shorter test duration than HFA. The imo systematically yielded a lower sensitivity than HFA. The average sensitivity at each test location correlated well between the perimeters in all groups, with the correlation coefficients ranging from 0.89 to 0.98. Bland–Altman plots showed wider limits of agreement in the affected quadrants compared to the unaffected quadrants in the bitemporal and homonymous groups. The fixation loss rate did not differ between the perimeters, but there were significant differences in the false positive and false negative rates between perimeters.

Conclusion

BRSET detected VF defects due to C/PCLs as accurately as the HFA monocular test with a shorter test duration.

     

A comparison of global indices between the Medmont Automated Perimeter and the Humphrey Field Analyzer

BACKGROUND: Two commonly used perimeters in Australia are the Humphrey Field Analyzer II (HFA) and the Medmont Automated Perimeter (MAP). Each device describes the visual field in terms of numerical values called global indices; however, these values are not interchangeable between devices. This study was designed to directly compare the global indices of HFA and MAP visual fields. METHODS: 63 subjects who had suspected glaucoma, ocular hypertension or glaucoma, or were normal controls were recruited selectively. Each patient was tested with the MAP and HFA. Global indices were then compared between tests. These included mean deviation (MD) and pattern standard deviation (PSD) from the HFA and average defect (AD) and pattern defect (PD) from the MAP. RESULTS: The MD and PSD results were strongly correlated with the AD and PD results, respectively. The relationship between them could be described in terms of two polynomial equations: AD = 0.94+1.31(MD)+0.02(MD)(2) and PD = 2.21(PSD)-0.05(PSD)(2)-0.006. These non-linear relationships may be the result of differences in testing method (test stimulus spectrum, number of testing locations or background luminance) or differences in the way each global index was calculated. CONCLUSION: The AD and PD results obtained from the MAP may be substituted for the MD and PSD results from the HFA after appropriate conversion.     

Evaluation of threshold estimation and learning effect of two perimetric strategies, SITA Fast and CLIP, in damaged visual fields

PURPOSE: The threshold estimation, learning effect, and between-algorithm differences of the Fast Swedish Interactive Thresholding Algorithm (SITA Fast), of the Humphrey Field Analyzer (HFA), and the Continuous Light Increment Perimetry (CLIP) strategy of the Oculus Twinfield perimeter were evaluated in damaged visual fields. METHODS: Twenty-one glaucomatous patients with damaged visual fields (MD worse than -8 dB) underwent Oculus Full Threshold (FT), Humphrey FT, SITA Fast, and CLIP 30-2 perimetric examinations. All the tests were repeated in a second session at least 3 days later. The point-wise differences in absolute sensitivity and of the total deviation plot values between FT and fast algorithms, between fast algorithms and the learning effect were evaluated (Wilcoxon test and Bland-Altman analysis). RESULTS: The average point-wise sensitivity difference between SITA Fast and HFA FT strategy (0.84 dB) was significantly lower than that found between CLIP and Oculus FT strategy (1.71 dB). Between-algorithm point-wise differences of the total deviation plot values of the fast strategies were not significantly different. Learning effect for SITA Fast (0.67 dB) was higher than that found for CLIP (0.39 dB). Test time for SITA (367+/-71 sec) and CLIP (453+/-98 sec) were about 55% and 35%, respectively, shorter (p<0.001) than those found with FT algorithms. The acceptance for fast algorithms and particularly for CLIP was significantly better. CONCLUSIONS: The two fast strategies, even though using very different algorithms, showed good threshold estimation compared to FT strategies with a consistent time saving in damaged visual fields.     

The clinical efficacy of a topical dorzolamide in the management of cystoid macular edema in patients with retinitis pigmentosa

Background

Cystoid macular edema (CME) is one of the common complications of retinitis pigmentosa (RP), and is responsible for patient complications such as blurred and reduced visual acuity and for subsequent atrophic changes in the fovea. The objective of this work was to evaluate the clinical efficacy of a topical dorzolamide (a carbonic anhydrase inhibitor) in CME associated with RP.

Methods

Sixteen eyes of nine patients with CME secondary to typical forms of RP were included in the study. Baseline visual acuity, visual field, and optical coherence tomography (OCT) measurements were obtained for all patients. All patients used 1% dorzolamide three times daily in each eye. Patients underwent follow-up exams at 1, 3, and 6?months after treatment. The response to treatment was monitored by visual acuity and visual field measurement testing using the Humphrey Field Analyzer (HFA: the central 10-2 Program); in addition, foveal thickness was measured by OCT. Evaluation of macular sensitivity calculated by HFA as the average of 12 central points.

Results

Thirteen (81.3%) of 16 eyes showed a clear decrease in retinal thickness after treatment. Evaluation of macular sensitivity, calculated by HFA as the average of 12 central points (with the exception of foveal point data, showed an improvement of more than 1.0?dB in nine (56.3%) of 16 eyes. Moreover, both the mean deviation value and macular sensitivity were significantly improved. No severe side-effects were seen in any of the patients examined.

Conclusions

The results demonstrated that a topical dorzolamide is effective for the treatment of CME in patients with RP, and that the positive treatment effects last for up to 6?months.     

The effect of background intensity on the components of fluctuation as determined by threshold-related automated perimetry

We studied the effect of various background intensities on the components of fluctuation by testing 20 healthy subjects on the Humphrey Field Analyzer. Our results show little difference in the total fluctuation between two low photopic background intensities similar to those commonly used on commercial perimeters 3.02 dB for 31.5 apostilbs (asb) and 2.77 dB for 3.15 asb. However, an increase in total fluctuation (3.74 dB for 0.315 asb and 4.24 dB for 0.0315 asb) as well as in its short-term, long-term heterogeneous, and inter-individual components was seen at mesopic background intensities as compared with the low photopic range. This study suggests that in healthy individuals, little difference exists in the fluctuation resulting from differences in background intensities commonly used on commercial perimeters, whereas mesopic illumination may increase the variability of threshold responses.     

Prospective randomized comparative study of frequency doubling perimetry vs standard automated perimetry in patients with glaucoma

AIM: To compare frequency doubling perimetry (FDP) versus standard automated perimetry in glaucoma. To evaluate the reproducibility of both methods. PATIENTS AND METHODS: All the patients were tested (full threshold test) twice with both FDP (N-30) and Humphrey Field Analyzer II model 750 (HFA) (30-2 procedures) in random sequence, within one day. The parameters mean deviation (MD), pattern standard deviation (PSD) and measured thresholds per quadrant and center areas were evaluated for FDP/HFA comparison in 45 glaucoma patients. The same parameters were used for testing the reproducibility of FDP (n = 46) and HFA (N = 39). Additionally, the center and each quadrant area were checked for any deviation in the total deviation probability plots. For statistical analysis Kappa coefficients and Bland/Altman plots were used. RESULTS: An average MD (FDP vs HFA) of -7.3 +/- 5.8 dB vs -8.9 +/- 7.6 dB and PSD of 6.9 +/- 2.4 dB vs 6.5 +/- 3.6 dB were found. Kappa coefficients denote marginal accordance (kappa: 0.11-0.38) for area deviations. In a total of 225 areas HFA detected 191 deviations and FDP 165. HFA measured more negative deviation compared with FDP in the case of MD < -15 dB. The reproducibility was 0.98 (MD) and 0.92 (PSD) for FDP and 0.98 (MD) and 0.95 (PSD) for HFA (95% confidence interval). CONCLUSIONS: There was great conformity between FDP and HFA in glaucoma patients. HFA detected more deviations in the total deviation probability plots than FDP. There was a high reproducibility of both methods. FDP is an appropriate tool for detecting visual field loss in glaucoma patients.     

A comparison of cupola-free perimetry with conventional perimetry: preliminary results

In the comparison of ten normal and two pathological visual fields, excellent agreement was found between examinations made with Octopus perimeters (types 201 and 500) and a prototype version of a new cupola-free perimeter (CFPP). The examination of a single glaucomatous visual field, however, exhibited an elevated mean defect value with the prototype instrument in comparison with Octopus 201 examinations of the same visual field. Although this difference may be easily explained by long-term fluctuation effects, further investigations based on a broader empirical basis will be required. Based on the results of this preliminary work the following remarks can be made with respect to the cupola-free perimeter: provided that the zero point of the dB scale is chosen appropriately, ie, with a stimulus luminance of about 4,000 asb used as the 0 dB level, the same differential light sensitivity (DLS) values for normal visual fields can be obtained with the CFPP as with all Octopus models (201, 500, 2000). Within the limits of measurement error, the same decrease of DLS was found with the CFPP as obtained using the other perimeters for test locations (of the G1 program), ranging from the center out to an eccentricity of 30 degrees. Thus it appears that the normal values as used in the other Octopus perimeters can also be utilized in this cupola-free instrument within this range.     

Formulas for conversion between Octopus and Humphrey threshold values and indices

Background: Comparing the results in a patient tested with two different automated perimeters can be difficult. The purpose of this study is to derive and test formulas for conversion between threshold values of every single test location and indices measured with Octopus and Humphrey perimeters. Methods: We tested 50 eyes of 27 patients with program G1 of the Octopus perimeter and program 24-2 of the Humphrey Field Analyzer. All pairs of tests were performed on separate days but within 1 month of each other. Twelve eyes had normal visual fields, and 38 eyes had mild to moderate glaucomatous defects. Thirty-three eyes were chosen to determine empirically prediction equations for each test location and for each of the global indices, while the 17 remaining eyes were used to test the validity of the predictions. Results: The mean absolute difference (i.e. the mean of the absolute values of the differences) between the predicted and the actual Octopus thresholds was 4.2±1.6 dB. The mean absolute difference between the predicted and the actual Humphrey thresholds was 5.7±1.6 dB. These differences were lower than the mean expected 5th to 95th percentile range of long-term fluctuation (10.3±2 dB for the Octopus fields and 9.2±2.2 dB for the Humphrey fields). Conclusion: Conversion formulas between Octopus and Humphrey formats can be used, with a known error of the estimate, to compare the perimetric results of the patients tested with the two instruments.Presented in part at the Association for Research in Vision and Ophthalmology meeting, Sarasota, Florida, 6 May 1993 The authors have no proprietary interest in the software described herein     

Comparing retinal sensitivities on blue-on-yellow and green-on-yellow perimetry in glaucoma suspects

Purpose:To compare the retinal sensitivities between the blue-on-yellow perimetry (BYP)/short-wavelength automated perimetry (SWAP) and green-on-yellow perimetry (GYP) among patients with and without nuclear sclerosis among glaucoma suspects.Methods:After ophthalmic examination, patients were subjected to two perimetric tests: BYP and GYP. The visual field (VF) parameters were compared between the two perimeters (p < 0.05 was considered significant).Results:Fifty-five eyes of 39 patients with a mean age of 60.53 ± 9.70 years were included in the study. Twenty-one eyes had clear lens or pseudophakia. Twenty-six eyes had lower grades of nuclear sclerosis (NO2NC2, NO3NC3) and eight eyes had higher grades of cataract (NO4NC4, NO5NC5). The mean retinal sensitivity (RS) in BYP was 22.08 ± 5.02 (dB) and in GYP was 23.84 ± 5.50 (dB) (p = 0.08). The mean defect in BYP was -2.56 ± 4.40 (dB) and in GYP was -3.24 ± 5.05 (dB), pattern standard deviation (PSD) in BYP was 3.65 ± 1.91 (dB) and in GYP was 3.83 ± 1.99 (dB), and foveal threshold (FT) was 24.20 ± 4.32 (dB) in BYP and 28.10 ± 4.50 (dB) in GYP. The two perimeters showed good agreement by the Bland–Altman plot for all parameters. Fourteen eyes showed perimetric changes suggestive of glaucoma by BYP. In these, GYP had a sensitivity of 92.86% (95% CI of 66.13% to 99.82%) and specificity of 95.12% (95% CI of 83.47% to 99.40%).Conclusion:BYP and GYP show good agreement. They are comparable in clear media as well as in different grades of nuclear sclerosis. GYP showed good sensitivity and specificity compared to BYP.     

Visual loss and perimetric sensitivity in eyes with retinitis pigmentosa

Purpose

To investigate the various perimetric parameters that best predict reduction of best-corrected visual acuity (BCVA) to worse than 0.5 in the near future in eyes with retinitis pigmentosa (RP).

Methods

The most recent records obtained by Humphrey Field Analyzer (HFA) central 10-2 perimetry were studied for the right eyes of 123 patients (60 men and 63 women) with typical RP. The correlation between various parameters of perimetric sensitivity and BCVA was retrospectively studied. The receiver operating characteristic (ROC) curves were used to find the best parameter to discriminate eyes with BCVA ≥0.5 from those with BCVA <0.5.

Results

Spearman rank correlation coefficients with logMAR BCVA were the highest for the foveal threshold (FT) and mean sensitivity of the test points within 1.4° of the fixation point (MS1.4). The ROC curve analysis revealed that the area under the curve was the largest for the MS1.4 among all the perimetric parameters for discriminating eyes with BCVA ≥0.5 from those with BCVA <0.5. The cutoff value of 30 dB showed 100 % specificity and 57 % sensitivity.

Conclusions

The risk of vision decreasing below 0.5 in the near future may be predicted when the mean sensitivity within 1.4° of the fixation point in the HFA 10-2 reaches 30 dB in eyes with RP.     

Predicting glaucomatous sensitivity loss using perimetric color saturation test

PURPOSE: To predict future glaucomatous sensitivity loss using a perimetric color saturation test (PCST) that measures the color saturation discrimination threshold for six hues (red, yellow, green, green-blue, blue, and purple) at 9 degrees in horizontal and 3 degrees in vertical extrafoveal points. METHODS: This new test was carried out on 31 patients (31 eyes) with early glaucoma or ocular hypertension. The sensitivity loss at the four points approximately 9.5 degrees apart from the fixation point was prospectively evaluated annually for 3 years using the Humphrey Field Analyzer (HFA) program central 30-2. The initial results of PCST and the total deviation (TD) in the follow-up HFA results were compared. RESULTS: Twenty-seven patients (27 eyes) were followed up for 3 years. The color saturation threshold for six hues was correlated with the TD of HFA results at 108 points in the 27 eyes. The TD was -4 dB or better at the baseline measurement in 91 out of the 108 points. The averaged TD in the second and the third year in the follow-up period decreased below -4 dB in 10 of these 91 points, which were categorized as progression points in relation to the 81 nonprogression points. In the initial PCST, only the saturation threshold for purple was higher in the progression points when compared with the nonprogression points (P=.0004, Mann-Whitney U-test). CONCLUSION: Future sensitivity loss is most likely at the points where the threshold of color saturation discrimination is increased for purple in eyes with early glaucoma or ocular hypertension.     

Macular automatic fundus perimetry threshold versus standard perimetry threshold

PURPOSE: To evaluate if retinal sensitivity threshold obtained with an automatic fundus perimeter may be compared with a standard perimeter retinal threshold. METHODS: Automatic full-threshold fundus perimetry (microperimetry) of the macular area (10 degrees grid, 37 stimulated points) was quantified with a new automatic fundus perimeter (MP1 microperimeter) in nine normal subjects (18 eyes). Retinal threshold was also quantified using an identical grid projected with a standard Octopus 101 perimeter. RESULTS: Mean threshold registered by MP1 microperimeter was 19.7+/-0.8 dB (range 16-20 dB; 4.38+/-0.96 asb, range 4-10 asb) versus 33.1+/-1.7 dB (range 27-38 dB; 0.53+/-0.22 asb, range 0.16-2 asb) obtained with Octopus perimeter. Mean SD of intraindividual variation was 0.74 dB in MP1 and 1.51 dB in Octopus. No statistically significant differences were documented between right and left eye with both instruments (p=0.64). No reliable mathematical relationship between retinal thresholds could be obtained with the two perimeters. CONCLUSIONS: Fundus perimetry is a precise, functional fundus-related technique which allows threshold determination at selected retinal points even if fixation is unstable and visual acuity is low. This is beyond the possibility of any static standard perimetry. Normal threshold values obtained with MP1 automatic microperimeter cannot be currently compared with those obtained with standard Octopus perimeter.     

Comparison of the frequency doubling technology screening algorithm and the Humphrey 24-2 SITA-FAST in a large eye screening

Purpose: To compare the Frequency Doubling Technology (FDT) C20‐1 screening algorithm and the Humphrey Field Analyser II (HFA) 24?2 SITA‐FAST in a large eye screening. Methods: In a non‐randomized, prospective, free eye screening, the FDT Screening Protocol (C20‐1 Screening Algorithm) was administered to 574 attendees (422 men and 152 women, average age 64, range 17?89 years) of the 1998 Veterans of Foreign Wars (VFW) Convention in San Antonio, Texas. Individuals who failed the FDT (two or more misses out of 17 locations) immediately underwent white‐on‐white threshold visual field perimetry (HFA 24‐2, SITA‐FAST). Humphrey visual field analysis included STATPAC and masked evaluations by three glaucoma specialists. Results: Approximately one‐tenth of the VFW conference attendees voluntarily presented themselves for screening. Among these 574 volunteers, 69 (12%) failed the FDT and underwent HFA analysis. Eighty‐one per cent (56/69) of these FDT failures had abnormal HFA Glaucoma Hemifield Tests. Eighty‐eight per cent (61/69) were judged to have nerve fibre type visual field loss on HFA by at least two of three masked examiners. A positive correlation existed between the number of FDT locations missed and the HFA mean deviation (r = 0.5, P = 0.0001). A similar association was observed when FDT and HFA results were analysed by quadrant (r = 0.5, P < 0.0001). Conclusion: There was a low false positive rate and a good positive predictive value comparing the FDT screening algorithm to the HFA 24?2 SITA‐FAST in this study. This supports the potential use of FDT as an economical screening device.     

Anatomy of a supergroup: does a criterion of normal perimetric performance generate a supernormal population?

PURPOSE: To interpret individual results from automated perimeters, a normative database must be developed. Typically, a set of criteria determines those subjects that may be included in the database. This study examined whether a criterion of normal performance on an established perimeter generates a subgroup with supernormal perimetric performance. METHODS: The right-eye perimetric results of 100 subjects were analyzed. Subjects had visual acuities of 6/12 or better, no history of eye disease, and normal slit lamp biomicroscopic and ophthalmoscopic examinations. Subjects performed test-retest visual field examinations on a Humphrey Field Analyzer (HFA) 24-2 test (Zeiss Humphrey Systems, Dublin, CA), and on a custom frequency-doubling (FD) perimeter with targets spaced in the same 24-2 pattern. RESULTS: Test-retest correlation (Spearman rank correlation coefficients, rs) for mean defect (MD) and pattern SD (PSD) were 0.65 and 0.40 (HFA), and 0.82 and 0.39 (FD perimeter). Three subjects with HFA MDs in the lower 5% had similarly low MDs on retest, whereas no subject was common between the test and retest for the lower 5% of HFA PSD. Correlation between the HFA and FD test results were 0.41 (MD) and 0.05 (PSD). Based on these correlations, the bias introduced into perimetric probability limits were determined, by using Monte Carlo simulations. CONCLUSIONS: Although a criterion of a normal MD may produce a subpopulation with supernormal perimetric performance, a criterion of a normal PSD is less likely to do so. Also, a criterion on one test type is less likely to create a supernormal group on a different test type. The bias introduced into perimetric probability limits is small.