Topographical spatial summation in glaucoma.

PURPOSE: Stimulus luminance (L) and area (A) are related by the equation L x A(k)=constant. The authors evaluated the k value at 66 positions of the central visual field in patients with glaucoma, to modify L and A simultaneously in order to examine advanced glaucomas with a bigger dynamic range. METHODS: The luminance limitation of a computer screen with automatic photometric control was compensated for by increasing the stimulus area in the range between 0 and 17 dB, using the k topographic values previously calculated on normal subjects. Four initial series of 21, 12, 10, and 10 glaucomas were sequentially examined with the Octopus 311 in which the stimulus size cannot be freely changed during the examination, and with the experimental method (Pulsar-SAP) modifying stimulus sizes to equal the results. k Final estimation was verified in 60 new cases. RESULTS: k values increase progressively with defect deepness. Values higher than those of the normal population with equivalent topographic differences were obtained. Correlation between indices was as follows: MD: r=0.94 (p<0.0001); square root of the loss of variance (sLV): r=0.93 (p<0.0001). Frequency of local defects was similar in both procedures. Average topographic differences between thresholds were usually less than 1 dB. The average threshold difference favored Pulsar-SAP by 0.45 dB at those points where the average threshold of both examinations was less than 18 dB and 0.37 dB where such average was higher than or equal to 18 dB. CONCLUSIONS: k value is higher in patients with glaucoma than in normal subjects, although the topographic features are similar. It is feasible to design a scale combining stimulus luminance and sizes to use screens with relative low brightness as surfaces for visual field examination.

[Diagnostic capability of PULSAR, FDT y HRT-II in glaucoma suspects]. / Capacidad diagnóstica del HRT-II y de las perimetrías TOP, PULSAR y FDT en pacientes sospechosos de sufrir glaucoma.

PURPOSE: To determine the diagnostic capability of PULSAR-T30W, FDT-Threshold-N30 and HRT-II in glaucoma suspects. METHODS: Forty-seven eyes from 47 referred glaucoma suspects (GS) were examined twice with each technique. Cases with TOP-WW-MD>6dB were excluded. Results were compared with those of 70 eyes from 70 normal controls (C). RESULTS: Mean MD value using TOP-WW in the GS group (0.96dB. sd=1.7) was not significantly different from C (0.8dB. sd=1.77) (p>0.05). Disc area in GS group (2.12 mm(2). sd=0.34) was significantly greater than in C (1.97 mm2. sd=0.45) (p<0.01). For 95.7% specificity, PULSAR-sLV showed the highest sensitivity of 30.9% in individual examinations. The highest reproducible sensitivity in the two examinations was obtained using HRT-II maximum contour elevation (23.4%) and reference height (23.4%), and was 14.9% for various indices after correcting for the influence of disc area (cup area, cup/disc area ratio, maximum contour depression and mean RNFL thickness). Reproducible sensitivity of the perimetric indices was: PULSAR-MD=8.5%, PULSAR-sLV=17%, FDT-MD=6.4%, FDT-PSD=4.3%. The association of perimetric and HRT-II indices achieved high sensitivity but low diagnostic reproducibility. CONCLUSIONS: The most effective indices were maximum contour elevation, reference height and PULSAR-sLV, although the inclusion of the optic nerve head assessment in the selection of the GS sample may have favored the HRT-II results.

Diagnostic accuracy and reproducibility of tendency oriented perimetry in glaucoma.

PURPOSE: To evaluate the diagnostic capability of tendency oriented perimetry (TOP) in glaucoma. METHODS: A): The diagnostic accuracy of mean defect (MD), square-root of the loss variance (s LV), and number of pathologic points (NPP) was calculated in 295 normal and 414 glaucoma eyes (179 early, 112 moderate, and 123 advanced) examined with TOP. B): Threshold fluctuation (F) and its relationship with the loss variance (LV) was measured in 34 normal and 33 glaucoma eyes (mean MD=3 dB; SD=3.9) for TOP and for full-threshold perimetry (FT). C): Twenty-eight eyes with stable glaucoma (mean MD=9.5 dB; SD=7.2) were examined six times to quantify LV error. D): TOP and FT were tested with the simulation program PeriSim using different behavior models. RESULTS: A): The best diagnostic index in early glaucoma (MD<6dB) was sLV (specificity=90.2%, sensitivity=84.9). The three indices had similar precision in moderate and severe glaucoma. B): Threshold fluctuation and sLV were better correlated in TOP (r=0.72, p<0.01) than in FT (r=0.62, p<0.01). For normal subjects, in FT the incidence of F<2 dB was 8.82% and s LV<1.5 dB 5.88%. The same frequencies in TOP were 67.65% and 55.88%. C): Averaging six examinations reduced the sLV val ue by 22%. D): The threshold estimation error increased 1 dB in TOP in relation to FT for the same patient's behavior, but the error in TOP was lower than i n FT when the worst behavior was modeled. CONCLUSIONS: TOP is a good discriminator between glaucoma and normality. Perimetry results overestimate the real sLV value. TOP's high diagnostic ability is probably associated to the algorithm design and to less contaminating influences during the examination.

[Spatial summation: its topography in the central visual field]. / Topografía de la sumación espacial en el campo visual central.

PURPOSE: Luminance (L) and area (A) of the stimulus are related by the equation LxAk=constant. We evaluated the k value in 66 positions of the central visual field. METHODS: Ten eyes of 10 healthy subjects were examined for conventional luminous thresholds at 66 positions of the central visual field with the TOP strategy using Goldmann sizes 4, 3.5, 3, 2.5 and 1.9 in the PULSAR perimeter. RESULTS: The k value increased in a lineal manner from the centre towards the periphery (slope=0.01 per degree, average k=0.616, r=0.98, p<0.01) but with unequal slopes at the different meridians. In the inferior hemi-fields it was higher (k=0.657) than in the superior hemi-fields (k=0.574). The k value at the supero-nasal hemifields is quite similar to that found at the paracentral region, and maximum at the temporal inferior region. CONCLUSIONS: Spatial summation in the central visual field has specific values for different positions.

[Nomogram for ocular hypertension progression risk based on the ocular hypertension treatment study]. / Nomograma de riesgo de progreso de hipertensión ocular basado en el ocular hypertension treatment study.

INTRODUCTION: A practical nomogram has been designed in order to present the results obtained from the Ocular Hypertension Study (Gordon et al. Arch Ophthalmol 2002; 120: 714-720), where the relation between intraocular pressure (IOP) and corneal thickness becomes apparent, involving the risk of evolution from ocular hypertension into glaucoma within a 6 year period. MATERIAL AND METHODS: We used a multiple logarithmic regression for the nine parameters shown in figure 1 of the above mentioned paper. RESULTS: A correlation coefficient of 0.91 (p<0.001) permits to establish the following equation: Probability of evolution (%) = 13539.5 x (1.1385IOP) x (0.9818(CORNEAL THICKNESS)). This implies that a variation of 10 microns on corneal thickness leads to an IOP's modification of 1.5 mmHg in the same sense. From these data, we designed the nomogram included in this paper. CONCLUSIONS: IOP and pachymetry together allow an estimation of the risk of evolution from ocular hypertension into glaucoma in a graphical practical way. From this indirect estimation, the influence of corneal thickness on IOP's measure seems to be much higher than previously estimated.

Influence of the "fatigue effect" on the mean deviation measurement in perimetry.

PURPOSE: To quantify the influence of the reduction of the threshold during perimetric study on the mean deviation (MD). METHODS: One hundred-57 eyes of 94 patients with ocular hypertension and glaucoma and 123 eyes of 62 normal patients were explored using the Humphrey perimeter with a Delphi program specially modified to make 12 consecutive measurements of the MD. RESULTS: Hypertension and glaucoma population: during the test, which lasted 13.88 +/- 1.25 minutes, the estimated MD showed a tendency to decrease by 2.9 dB on average from the beginning to the end of the exploration. This diminution was more important in patients with deeper defects, in whom the average was near 6 dB (Normal population: 13.26 +/- 2.91 minutes; mean decrease 2.22 dB). It was found that, in fact, this reduction is related to age (p < 0.01) and not to the level of the glaucomatous defect. CONCLUSIONS: Age, through a "fatigue effect", influences the measured depth of the glaucomatous defect. Since in a conventional exploration the thresholds of the points are obtained from the whole test, we can estimate that the "fatigue effect" influences the MD to the extent of approximately half (1.45-1.11 dB), with respect to the numbers indicated above.

[Update on glaucoma diagnosis and follow-up]. / Estado actual del diagnóstico y control evolutivo del glaucoma.

PURPOSE: To compare the different methods proposed for glaucoma diagnosis and follow-up. METHODS: Review of those papers that have published the sensitivity and specificity of the different methods, as well as simultaneous comparative studies of several of these methods, especially those that used patients in the initial stages of the disease. RESULTS: After analyzing the sensitivity and specificity results of the proposed techniques, we have found no evidence that blue-yellow perimetry (SWAP), nerve fibers photography, laser polarimetry (GDx), electrophysiological techniques or optic nerve head topography have better diagnosis abilities than white-white perimetry. This last technique evolves with the others, giving new criteria and strategies with higher precision. The different comparative results of the anatomical and functional procedures do not coincide and do not allow one to establish definite conclusions. CONCLUSIONS: The most promising expectations are nowadays on temporal phenomena (FDT, Flicker, PULSAR), new methods for analyzing optic nerve topography results and the value of the loss variance (LV) on TOP perimetry. The worst results correspond to blue-yellow perimetry and GDx.

[White-on-white, blue-on-yellow and blue-on-blue perimetry in normal subjects]. / Perimetrías blanco-blanco, azul-amarillo y azul-azul en sujetos normales.

PURPOSE: To compare blue-on-blue differential contrast perimetry (BB), in accordance with E. Land "Retinex" theory, with white-on-white (WW) and blue-on-yellow (BY) perimetries on normal subjects. METHODS: An Octopus 101 perimeter was modified for BB perimetry, using a 4cd/m2 background and stimulus Goldmann size V. Fifty healthy subjects (10 per decade, from 20 to 70 years) were examined twice with each type of perimetry (WW, BB, BY) using the TOP strategy. RESULTS: The results obtained with WW, BY and BB perimetry were respectively: Reduction of sensitivity per year: 0.13, 0.27 and 0.13 dB; correlation coefficient (r) of threshold with age (and error of estimation of Y over X): -0.63 (2.24 dB), -0.70 (3.77 dB) and -0.80 (1.32 dB); threshold fluctuation: 2.21, 3.03 and 2.03 dB; percentage of points deviated more than 5dB from the expected value for the patient age: 8.1, 16.0 and 4.2%. CONCLUSIONS: Perimetric results are more stable with BB strategy than with the other two types of perimetry. BY perimetry gives the worst results: threshold reduction with age is twice higher, individual fluctuation is 50% higher and points away from the mean value are much more frequent. Overlapping between blue and yellow filters is minimal in Octopus. Therefore, an absolute threshold is examined, which is much more unstable than WW or BB differential thresholds.

[Initial findings with pulsar perimetry in patients with ocular hypertension]. / Primeros hallazgos con perimetría pulsar en pacientes hipertensos oculares.

PURPOSE: To evaluate our first results with Pulsar perimetry in patients with ocular hypertension and compare them with normal individuals. METHODS: We studied 34 eyes of patients with ocular hypertension and normal G1 Octopus perimetry (mean age: 57.29 S.D. 10.55) and 41 eyes of normal individuals (mean age: 48.34 S.D. 13.71). A complete ophthalmologic examination, including Dr. González de la Rosa's Pulsar perimetry with TOP strategy, was performed for all patients. EXCLUSION CRITERIA: visual acuity <0.8, refractive defect 3 spheric dp or 1.5 astigmatic dp, pupil size <3 mm, ocular surgery or pathologies, non-controlled diabetes or neurological diseases. They all had previous perimetric experience. Results were analyzed with student t - test. RESULTS: For normal individuals, mean sensitivity (MS) for Pulsar perimetry was 21,25 src (spatial resolution and contrast units) with an S.D. of 2,70. Mean defect (MD) was 0,93 src S.D. 1,80 and loss variance (LV) was 6,11 src S.D. 4,30. For patients with ocular hypertension: MS was 18,65 src S.D. 2,79; MD was 2,73 src S.D. 2,30 and LV was 8,46 src S.D. 5,01. LV differences between the two groups were statistically significant (p<0.05) with 95% confidence limits of (-4.49; -0.20), and MS and MD differences, highly significant (p<0.01), with 99% confidence limits of (+0.92; +4.28;) and (-3.05; -0.54) respectively. CONCLUSIONS: Pulsar perimetry may have greater sensibility for the detection of early defects in patients with ocular hypertension than conventional perimetry.

[Topographic classification of glaucomatous visual fields]. / Clasificación topográfica del campo visual glaucomatoso.

PURPOSE: To propose a classification of glaucoma visual fields based on affected ganglion cells axons on their way through the optic nerve head. MATERIAL AND METHOD: 255 Octopus 1-2-3 visual fields from glaucoma patients and glaucoma suspected patients were analyzed. Determination coefficients (r(2)) between the 10 points closest to the blind spot and the 73 reminding ones were calculated by linear regression. RESULTS: Significant correlation was found (r(2)>0.33) with very distant points sensitivity related to the ones closer to the optic disc due to the fibers path. Seven areas could be defined by this method: three of them are not affected or latterly affected by the disease: S1 and I1 corresponding to the upper and lower papillo-macular bundle and T, located on the temporal aspect of the blind spot. Areas S2 and L2 correspond to the nasal and para-central upper and lower sensitivities. Areas S3 and I3 are in the border of upper and lower nasal fields where axons enter the optic disc at the apical portion. CONCLUSIONS: There is a relationship between the anatomical arrangement of ganglion cells axons on their way to the optic nerve and topography of glaucoma defects which may justify this proposed classification.

[Development of an automatic discrimination system for glaucomatous visual fields based on neuro-fuzzy nets]. / Desarrollo de un sistema automático de discriminación del campo visual glaucomatoso basado en un clasificador neuro-fuzzy.

PURPOSE: To provide a useful tool in the diagnosis of glaucoma by developing an automatic system for visual field classification based on neuro-fuzzy rules. METHOD: A total of 212 visual fields (OCTOPUS 123 program G1X), from 198 patients, were analysed: 61 normal (controls) and 151 with glaucomatous damage (49% with incipient damage, 29.1% with moderate damage, and 21.9% advanced). Inclusion criteria for glaucomatous patients were: Visual acuity >0.5, IOP < 20 mm Hg (with treatment), refraction <5 Dp and previous perimetric experience. EXCLUSION CRITERIA: miotics, other ocular pathologies which could interfere with visual field examination, and for control subjects: visual acuity >0.5, no ocular pathologies and refraction < 5 Dp. A neuro-fuzzy classifier (NEFCLASS) is a system consisting in a series of fuzzy rules, obtained after a learning process, which attempts to assign to each piece of data input its corresponding output. Initially, the characteristics of each data input are established (input units). Then, based on previous knowledge, a set of rules are defined, and finally, the learning process allows the optimisation of the classifier parameters to generate an output. RESULTS: Input units were defined by using the mean defects calculated at specific areas of the visual field; five rules were then created which generated sensitivity and specificity values of 96.0% and 93.4% respectively. CONCLUSIONS: The use of neuro-fuzzy rules for visual field classification in normal vs glaucomatous can provide results which can match the quality of those obtained with other techniques such as discriminatory analysis or neural networks.

Population dynamics and stock assessment for Octopus maya (Cephalopoda: Octopodidae) fishery in the Campeche Bank, Gulf of Mexico.

The octopus (Octopus maya) is one of the most important fish resources in the Mexican Gulf of Mexico with a mean annual yield of 9000 ton, and a reasonable number of jobs created; O. maya represents 80% of the total octopus catch, followed by Octopus vulgaris. There are two artisanal fleets based on Octopus maya and a middle-size fleet that covers both species. Catch-at-length structured data from the artisanal fleets, for the 1994 season (August 1st to December 15th) were used to analyze the O. maya population dynamics and stock and to estimate the current level of exploitation. Von Bertalanffy growth parameters were: L infinity = 252 mm, mantle length; K = 1.4 year-1; oscillation parameters C = 1.0, WP = 0.6; and tz = 0.842 years. A rough estimate of natural mortality was M = 2.2, total mortality from catch curve Z = 8.77, and exploitation rate F/Z = 0.75. This last value suggests an intensive exploitation, even when yield per recruit analysis indicates both fleets may increase the minimum legal size on about 10% to increase yields. The length-based VPA also shows that the stock is being exploited under its maximum acceptable biological limit. These apparently contradictory results are explained by biological and behavioral characteristics of this species. Because most females die after reproduction, a new gross estimation of natural mortality was computed as M = 3.3. The new estimate of exploitation rate was F/Z = 0.57. This new value coincides with results from the length-VPA and the Thompson and Bell methods, the former suggesting that a reduction of 20% in fishing mortality may provide larger yields. This fishery resource is fully exploited and current management measures must be revised to sustain and probably optimize yields.

[Pulsar perimetry. A review and new results]. / Pulsarperimetrie. Überblick und neue Ergebnisse.

We present a review and update on Pulsar perimetry, which combines temporal frequency, contrast and spatial frequency stimuli. The effects of age, visual acuity, and learning on results are described. Data on threshold fluctuation, signal-to-noise ratio, and the possibility of reducing noise with filtering techniques are provided. We describe its dynamic range and the possibility of compensating for profound defects. Finally, we show the results obtained in normal patients and in those with ocular hypertension or initial glaucoma, as well as an analysis of glaucoma progression.

[Variability and reproducibility of 3 methods for measuring the thickness of the nerve fiber layer]. / Variabilidad interindividual y reproducibilidad de tres métodos de medida del espesor de la capa de fibras nerviosas.

OBJECTIVE: To estimate the variability and reproducibility of confocal tomography (HRT), scanning laser polarimetry (GDx) and optical coherence tomography (OCT-Cirrus) to determine the thickness of the layer of ganglion fibers. METHOD: A total of 75 normal eyes were examined twice. Inter-individual variability was analyzed after standardizing the results. The coefficient of variation was used to measure the variability between tests, and the Pearson coefficient was used to analyze the correlation between variables. RESULTS: The inter-individual variability was similar in GDx (8.9%) and OCT (11.1%), but very high in HRT (30.0%). No instrument detected significant changes with age. The coefficient of variation of the total thickness between the examinations of the same subject was significantly lower (P<.05) in GDx (1.4) than in OCT (2.0), but very high in HRT (6.4). The same was true when analyzing the upper fibers (GDx=1.8, OCT=2.9, HRT = 6.6), but not with the lower ones, where the only significant differences were observed with HRT (GDx = 2.2, OCT = 2.7, HRT = 7.0). Among the results of OCT and GDx, there was a significant correlation when comparing the first (r=0.46, P<.0001) and second examinations (r=0.52, P<.0001). However there was no significant relationship between the data provided by HRT for the two remaining instruments (P>.05). CONCLUSIONS: There is a wide variation in the inter-individual and inter-test measurement of the thickness of the of nerve fibers layers using HRT. GDx has, in this respect, slight advantages over OCT.

Variability between experts in defining the edge and area of the optic nerve head.

OBJECTIVE: Estimation of the error rate in the subjective determination of the optic nerve head edge and area. METHOD: 1) 169 images of optic nerve disc were evaluated by five experts for the defining of the edges in 8 positions (every 45°). 2) The estimated areas of 26 cases were compared with the measurements of the Cirrus Optical Coherence Tomography (OCT-Cirrus). RESULTS: 1) The mean variation of the estimated radius was ±5.2%, with no significant differences between sectors. Specific differences were found between the 5 experts (P <.001), each one compared with the others. 2) The disc area measured by the OCT-Cirros was 1.78 mm² (SD =0.27). The results corresponding to the experts who detected smaller areas were better correlated to the area detected by the OCT-Cirrus (r=0.77-0.88) than the results corresponding to larger areas (r =0.61-0.69) (P <.05 in extreme cases). CONCLUSIONS: There are specific patterns in each expert for defining the disc edges and involve 20% variation in the estimation of the optic nerve area. The experts who detected smaller areas have a higher agreement with the objective method used. A web tool is proposed for self-assessment and training in this task.

[Comparing the ranges of defect measured with standard white on white and Pulsar perimetries]. / Comparación del rango de medida de defectos entre la perimetría estándar blanco/blanco y la perimetría Pulsar.

OBJECTIVES: Normal thresholds on Pulsar perimetry fall faster than those of standard perimetry in the peripheral visual field. Two related studies were performed. Firstly, the frequency distributions of glaucoma defects on standard automated perimetry (SAP) and the relationship of the centre and periphery (Study A) were studied first, followed by an attempt to establish the limits of pulsar perimetry (Study B). MATERIAL AND METHOD: A: frequency of defects was calculated in 78.663 SAP perimetries (G1-TOP, Octopus 1-2-3, Haag-Streit). Study B: 204 eyes with mean defect (MD-SAP) lower than 9 dB were examined 8.92 ± 4.19 times with SAP (TOP-32, Octopus 311) and temporal modulation perimetry (T30W, Pulsar Perimeter, Haag-Streit). RESULTS: Study A: 50.7% of the SAP examinations showed MD values lower than 9 dB and 32.7% bellow 6 dB. The MD correlation of the central 20° with the MD of the most peripheral points was r=0.933. Study B: in cases with MD-TOP-32 lower than 6 dB, SAP had the maximum possibility of detecting defect in 0.02% of points and Pulsar in 0.29%. In subjects with MD-TOP-32 between 6 and 9 dB frequencies were 0.38% in SAP and 3.5% in Pulsar (5.1% for eccentricities higher than 20°). CONCLUSIONS: Pulsar allows detecting defects, without range limitations, in the initial half of SAP frequencies expected on glaucoma patients. In order to study the progression of deeper defects the examination should focus on the central points, where the dynamic range of both systems is more equivalent.