M. Gonzalez de la Rosa

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.

Combined spatial, contrast, and temporal functions perimetry in mild glaucoma and ocular hypertension

PURPOSE To evaluate the diagnostic ability of a new perimetric procedure in glaucoma. METHODS Pulsar perimeter shows white circular sinusoidal grating patterns with decreasing amplitude, 5 in diameter, 500 msec in duration in 66 locations. The stimuli scale combines spatial resolution and contrast. The stimuli were shown with centrifugal wave motion at 8 cyl/deg (K6W) or pulse at 30 Hz (T30W). Fifty-six normal eyes and 82 eyes with ocular hypertension and mild glaucoma were included. These 82 cases were classified into four levels of diagnostic certainty, from 0 (ocular hypertension) to 3 (mild glaucoma). RESULTS Mean examination time was 3:49 min. Specificity was 96.4% (T30W) and 94.6% (K6W). Sensitivities for levels 0 and 3 were 34.5% to 100% (T30W) and 24.1% to 75% (K6W). The receiver operating characteristic (ROC) curve areas for T30W at levels 1, 2, and 3 were 0.88, 0.94, and 0.99. The ROC areas for K6W were 0.83, 0.91, and 0.97. There was good correlation between both Pulsar perimetries (r=0.88), but it was lower with conventional perimetry (r=0.58 for T30W and r=0.59 for K6W). CONCLUSIONS The novel Pulsar T30W perimetry may be helpful for the study of mild glaucoma and ocular hypertension. (Eur J Ophthalmol 2004; 14: 514-22).

Detection of visual-field deterioration by Glaucoma Progression Analysis and Threshold Noiseless Trend programs

Background: To compare the ability of Glaucoma Progression Analysis (GPA) and Threshold Noiseless Trend (TNT) programs to detect visual-field deterioration. Methods: Patients with open-angle glaucoma followed for a minimum of 2 years and a minimum of seven reliable visual fields were included. Progression was assessed subjectively by four masked glaucoma experts, and compared with GPA and TNT results. Each case was judged to be stable, deteriorated or suspicious of deterioration Results: A total of 56 eyes of 42 patients were followed with a mean of 7.8 (SD 1.0) tests over an average of 5.5 (1.04) years. Interobserver agreement to detect progression was good (mean kappa = 0.57). Progression was detected in 10–19 eyes by the experts, in six by GPA and in 24 by TNT. Using the consensus expert opinion as the gold standard (four clinicians detected progression), the GPA sensitivity and specificity were 75% and 83%, respectively, while the TNT sensitivity and specificity was 100% and 77%, respectively. Conclusion: TNT showed greater concordance with the experts than GPA in the detection of visual-field deterioration. GPA showed a high specificity but lower sensitivity, mainly detecting cases of high focality and pronounced mean defect slopes.

Long-Term Fluctuation of Standard Automatic Perimetry, Pulsar Perimetry and Frequency-Doubling Technology in Early Glaucoma Diagnosis

Purpose: Analyze the stability and accuracy of 3 perimetric techniques. Methods: A total of 104 stable eyes (65 subjects) with ocular hypertension and early glaucoma [group G, mean defect = 1.08 dB, SD = 2.0, in standard TOP automatic perimetry (SAP)] were examined 5 times during 18 months using: (a) SAP; (b) Pulsar temporal modulation perimetry (T30W), and (c) frequency-doubling technology (FDT N30). Ninety eyes from 90 normal controls were compared with the first set of examinations of group G. Results: The learning effect was minimal in the 3 techniques but higher in Pulsar (1.0 src, p < 0.05) than in SAP and FDT (0.4 dB). Long-term fluctuation (F) was significantly higher in FDT (3.1 dB, SD = 1.4, p < 0.0001) than in SAP (2.3 dB, SD = 1.1) and in Pulsar (1.9 src, SD = 0.7). Pulsar and FDT reduce F when increasing the number of examinations. F seems equivalent in SAP and FDT and lower in Pulsar, considering small-scale differences of the 3 perimeters. Conclusions: A slight learning effect would be expected on FDT and SAP in patients with previous experience with SAP. The stability and sensitivity of Pulsar is greater than on the other 2 systems. For early diagnosis of glaucoma it is essential to prove the reproducibility and coincidence of perimetric results.

Detection of morphological and functional progression in initial glaucoma

Background To observe the prospective follow-up results of functional and morphological data in patients with early, moderate and suspected glaucoma. Methods Eyes (n=156; average mean defect (MD)=2.2 dB) were examined every 3 months for an average of 3.6 years. Progression was estimated using regression analysis of the indices rim area and Glaucoma Probability Score of the Heidelberg retinal tomograph, mean thickness of the fibre layer using laser polarimetry with corneal compensation, MDs of standard, Pulsar and frequency doubling technology perimetries, and the threshold noiseless trend (TNT) program for the standard and Pulsar perimetries. Results TNT showed more than twice the diagnostic capacity of other methods. The maximum diagnostic sensitivity was obtained with TNT Pulsar. This procedure indicated progression in 40% of cases after seven examinations, and presented the lowest number of cases of progression not confirmed in two consecutive examinations. Most of the progressions of initial glaucoma were diffuse, without changes in the lens or loss of visual acuity. Heidelberg retinal tomograph and laser polarimetry made few diagnoses of progression. The diagnostic agreement between different methods was low, but higher between functional than morphological procedures. Conclusion Functional indices, especially Pulsar, showed better detection of progression than morphological indices.

Variabilidad entre expertos al delimitar el borde y área papilar

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.

Specificity of the Program Threshold Noiseless Trend for Perimetric Progression Analysis

Purpose: To evaluate the specificity of the Threshold Noiseless Trend program (TNT), designed to measure progression in visual fields, using four procedures. Materials and Methods: A. In 63 eyes with ocular hypertension, whose last examination showed no perimetric or morphological defects, we performed a mean of 7.70 ± 1.71 follow-up examinations during 2.2 ± 0.6 years. B. In 81 glaucomatous eyes examined twice with a bracketing strategy (Octopus 1-2-3 perimeter), we calculated mean threshold value and long-term fluctuation. We simulated 12 different visual fields, adding a random component to simulate an equivalent fluctuation of amplitude. C. Seventy-two glaucomatous eyes, with and without progression, were examined 7.76 ± 1.25 times during 4.88 ± 1.39 years using the Humphrey-Sita Standard strategy. Visual field tests were randomly disordered and analyzed using TNT. D. 1221 eyes were examined 7.19 ± 3.5 times during 3.50 ± 1.45 years (10,407 visual fields) using TOP-G1 program. We detected progression in 204 eyes using TNT. They were re-evaluated after random disordering of visual field tests. Results: The four procedures indicated specificity ≥ 95% as from the seventh examination; this reduced to 90% in experiment C with six examinations, and in experiments A and C with five examinations. Conclusions: The specificity of TNT may be considered to be over 95% with a large number of examinations, and 90–100% with fewer examinations. At least five examinations are required for a basic interpretation of progression, and preferably more than six to guarantee the specificity of the result.

Topographical spatial summation in glaucoma

PURPOSE Stimulus luminance (L) and area (A) are related by the equation LxAk=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.

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.

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.