Blue-on-yellow perimetry can predict the development of glaucomatous visual field loss

Detection of visual field defects in pre-perimetric glaucoma using fundus-oriented small-target perimetry

PURPOSE

To evaluate the usefulness of automated fundus-oriented small-target perimetry in detecting glaucomatous visual field abnormalities.

MATERIALS AND METHODS

One eye from each of 60 normal, 37 pre-perimetric glaucoma (PPG) and 29 early stage of primary open-angle glaucoma (POAG) persons were included. The new perimeter had two monitors, one for a campimeter and the other for the examiner's operation. A test area within the central 15° was set in the fundus image. The target size was 2.9 min in diameter, and the distance between the two adjacent targets was 60 min. The rate of negative response (RNR) among the age-matched controls, PPG and POAG were compared. The relationship between the RNR and age of the normal or standard automated perimetry (SAP) global indices in PPG and POAG was examined. The areas under the receiver-operating characteristic curve (AROC) to discriminate PPG or POAG versus normal were determined.

RESULTS

The RNR increased significantly with age in normal and differed significantly (P < 0.001) among control (1.8 ± 1.3 %), PPG (9.2 ± 10.4 %) and POAG (21.2 ± 14.3 %). Significant correlation was found between the RNR and SAP global indices. The AROC was 0.89 for PPG and 0.95 for POAG.

CONCLUSION

Fundus-oriented small-target perimetry is useful in detecting visual field abnormalities in PPG.

Retinal neuropathy precedes vasculopathy in diabetes: a function-based opportunity for early treatment intervention?

Diabetes, now at epidemic levels, can have devastating effects on the eye and vision. Treatments of the ocular complications are currently focused on relatively advanced stages and are limited to the slowing down of the progressive sight-threatening retinal vasculopathy (diabetic retinopathy). Tiny signals from the neural retina have been shown to reveal early diabetic neuropathy prior to vascular retinopathy. These signals, in a clinical test format, are predictive, by precise retinal location, of impending vasculopathy in the retina within a year, including sight-threatening oedema. The discovery opens possibilities for the future development of treatments to prevent the onset of retinopathy and the more sight-threatening retinal oedema and changes patient management strategies.

GDx VCC measurements and blue-on-yellow perimetry in ocular hypertension

The aim of this work was to investigate the correlation between scanning laser polarimetry with variable corneal compensation (GDx VCC) parameters and blue-on-yellow perimetry (B/YP) indices in ocular hypertension (OHT). One eye each of 52 patients with OHT (with a normal visual field, a normal optic nerve, and an untreated IOP > 21 mmHg) was chosen. All patients were examined with the Octopus 101 automated perimetry dG2 program using the dynamic/normal strategy (white-on-white perimetry, W/WP), with the dG2 program using the dynamic strategy/BY method (blue-on-yellow perimetry, B/YP), and with GDx VCC. Seven of the 52 OHT patients had both B/YP visual field loss and retinal nerve fiber layer (RNFL) defects with the GDx VCC measurements, and four patients demonstrated regions of B/YP visual field defects with corresponding RNFL defects on GDx VCC examination. A mild significant correlation was found between B/YP mean sensitivity (MS) and the superior average (R (2) =0.138, p = 0.049). No significant correlation was found between the W/WP indices and GDx VCC parameters. B/YP MS correlated with the superior average of GDx VCC in OHT patients. The findings brought up the possibility of using both techniques for clinical examination to yield converging data.

Learning curve and fatigue effect of flicker defined form perimetry

PURPOSE

To evaluate the learning curve and fatigue effect of flicker defined form (FDF) perimetry.

DESIGN

Prospective cross-sectional study.

MATERIAL AND METHODS

One hundred forty-one eyes of 75 healthy subjects were included in the study. Every subject was measured 3 times on 3 different days within 3 months. Differences among the tests were analyzed for mean sensitivity (MS), mean deviation (MD), pattern standard deviation (PSD), reliability indices, test duration, and test points <5% and <0.5% in 75 right eyes on the basis of linear mixed models for repeated measurements. To assess the effect of fatigue, differences of MS, MD, and PSD values between 66 left and right eyes were evaluated regarding alterations between these 3 examinations.

RESULTS

After 3 test sessions, significant improvements were found in MS and MD among all 3 tests (P ≤ .01), and in PSD between test 1 and test 3 (P = .02). Test duration decreased significantly between tests 1 and 3 (P = .01); fixation-loss errors decreased significantly between tests 2 and 3 and between tests 1 and 3 (P = .02, respectively). Test points with p < 0.5% decreased significantly between tests 1 and 2 (P = .04) and 1 and 3 (P = .01) When comparing both eyes, MS, MD, and PSD were significantly better in first than in second eyes examined.

CONCLUSIONS

There exist significant learning and fatigue effects for repeated flicker defined form perimetry. For good and reliable results on FDF perimetry, at least 3 tests should be performed in an individual. Between the tests of both eyes, a rest should be offered.

Variability in short-wavelength automated perimetry among peri- or postmenopausal women: a dependence on phyto-oestrogen consumption?

PURPOSE

To determine whether the hill of vision for Short-Wavelength Automated Perimetry (SWAP) is shallower for women who consume phyto-oestrogen-rich foods than for women who do not.

METHODS

Visual field data were compared for two groups of healthy amenorrhoeic women 48-69 years-old with normal vision and not using hormone replacement: (1) 24 subjects who reported consuming soy and/or flax products and (2) 20 subjects who reported not consuming these products. Two types of 24-2 visual fields were measured: (1) Full Threshold SWAP and (2) a white-on-white (W/W) field obtained using a Swedish Interactive Threshold Algorithm (SITA Standard).

RESULTS

The reduction of SWAP sensitivity from the centre of the field (4 loci, mean eccentricity = 4.2°) to the periphery (20 loci, mean eccentricity = 21.9°) was less for soy/flax consumers than for nonconsumers, both with age-referencing (mean difference = 1.7 dB, p = 0.018) and without (p = 0.012). Corresponding distinctions existed for the SWAP - W/W difference, and there was minimal effect for W/W fields alone. The peripheral age-referenced SWAP sensitivities averaged 2.5 dB higher for consumers than nonconsumers (p = 0.022).

CONCLUSION

The between-group distinctions are consistent with the possibility (derived from the women's health literature) that phyto-oestrogens may counteract a decline of short-wavelength-sensitive cone-mediated response among postmenopausal women. These results suggest another potential application for SWAP outside its original intended purpose as a glaucoma test. Future studies should assess whether phyto-oestrogen consumption is most beneficial for women who are sufficiently young and/or not too far beyond menopause.

The role of standard automated perimetry and newer functional methods for glaucoma diagnosis and follow-up

Automated perimetry has become the mainstream for assessment of functional glaucomatous loss and progressive damage. Recent improvements with the Swedish interactive thresholding algorithm (SITA) strategy and the guided progression analysis (GPA) have further settled standard achromatic perimetry (SAP) as the preferred method for diagnosis and follow-up of functional loss. Although SAP is still considered the gold standard, function-specific perimetry may offer advantages for early diagnosis. Frequency doubling technology (FDT) and short-wavelength automated perimetry (SWAP) have been shown to be helpful, especially when SAP is normal and there is a suspicion of glaucoma. Studies using rarebit perimetry have also shown promising results. Studies have observed that each test identifies a different subset of eyes, and combining the tests may improve sensitivity. Nevertheless, the more sophisticated analyses do not reduce the importance of a correct interpretation of the test results.

Blue-on-yellow perimetry and corneal thickness in patients with ocular hypertension

AIM

To evaluate the frequency of blue-on-yellow perimetry (B/YP) deficits in ocular hypertension (OHT) patients and to correlate these findings with central corneal thickness (CCT), and to investigate the influence of age, refraction and gender on the B/YP results in OHT patients.

METHODS

The B/YP and CCT were checked respectively in 72 OHT patients with normal white-on-white perimetry(W/WP) and normal optic nerve head. The B/YP was tested by Octopus 101 automated perimetry using G2 strategy, while the CCT was checked with DGH-550 ultrasound pachymeter. All patients were chosen randomly one eye for statistical analysis, a binary regression model was used to determine the independent contribution of variables included in the model, and the differences of the intraocular pressure (IOP), CCT, age, refraction and gender between the normal B/YP group and abnormal B/YP group were compared.

RESULTS

Forty-nine out of 72 patients with OHT showed normal B/YP results, whereas 23 of 72 patients(31.9%) demonstrated abnormal B/YP results. CCT showed a correlation with the B/YP results (B=-0.038, SE=0.019, P=0.044), whereas none of the IOP, age, refraction and gender was found to be correlated with the B/YP results. The mean CCT in OHT patients with abnormal B/YP group was lower than that with normal B/YP group (t=2.066, P=0.043).There was a significant positive correlation between IOP and CCT (R(2)=0.513, P=0.000).

CONCLUSION

The mean CCT in OHT patients with abnormal B/YP results was lower than that with normal B/YP results. There was a significant positive correlation between IOP and CCT in OHT patients. The age, refraction and gender didn't influence the B/YP results in OHT patients.

Relation between blue-on-yellow perimetry and optical coherence tomography in normal tension glaucoma

OBJECTIVE

To assess the relation between blue-on-yellow perimetry (B/YP) indices and optical coherence tomography (OCT) parameters in normal tension glaucoma (NTG) patients and to investigate the diagnostic ability of B/YP and OCT in discriminating NTG from normal eyes.

DESIGN

Cross-sectional study.

PARTICIPANTS

Eighty normal subjects (80 eyes) and 80 NTG patients (80 eyes) were enrolled in the study.

METHODS

All patients underwent white-on-white perimetry, B/YP, and OCT measurement. The correlation between B/YP indices and OCT parameters was analyzed. The area of the receiver operating characteristic (ROC) curve was calculated to discriminate NTG patients from normal subjects.

RESULTS

A highly significant correlation was found between B/YP mean deviation (MD) and average thickness of the retinal nerve fibre layer (r2 = 0.707, p = 0.000), and a moderately significant correlation was found between B/YP MD and temporal average (r2 = 0.437, p = 0.010) in the early NTG patients. A mildly or moderately significant correlation was found between B/YP MD and average thickness, inferior average, temporal average, superior maximum, and maximum-minimum (r2 = 0.212-0.498, p = 0.001-0.048) in the moderate or late NTG patients. The area under the ROC curve at the B/YP MD was 0.896, and the 3 OCT parameters with the widest area under the curve were average thickness (0.957), inferior average (0.932), and superior average (0.913). Average thickness showed the highest sensitivity (93%) with specificities at 90% and 80%.

CONCLUSIONS

The significant correlation between B/YP indices and OCT parameters in NTG patients suggests that the 2 tests detect similar areas or amounts of NTG damage and could be used for NTG early diagnosis.

Effect of yellow-tinted intraocular lenses on short-wavelength automated perimetry

PURPOSE

To investigate the effect of yellow-tinted intraocular lenses (IOLs) on short-wavelength automated perimetry (SWAP).

DESIGN

Cross-sectional observation study.

METHODS

Twenty-two patients who had implantation of yellow-tinted IOLs (AcrySof SN60AT or SN60WF; Alcon Laboratories) in 1 eye and nontinted IOLs (AcrySof SA60AT) in the other eye were included in the study. Standard automated perimetry (SAP) and SWAP were performed. The results for the mean deviation (MD), pattern standard deviation (PSD), and glaucoma hemifield test results were compared intra-individually.

RESULTS

There was no statistically significant difference between the IOLs on the SAP (MD, PSD; P = .851, P = .388, respectively). However, a significant difference was observed between the IOLs on the SWAP (MD, PSD; P = .033, P = .033, respectively). The glaucoma hemifield test did not show significant differences in the SAP (P = .083). However, the SWAP showed significant differences (P = .003).

CONCLUSIONS

The yellow-tinted IOLs may affect the results of the SWAP; therefore, caution is needed in interpreting the results of the SWAP in eyes with implanted yellow-tinted IOLs.

Mild learning effect of short-wavelength automated perimetry using SITA program

PURPOSE

To evaluate the learning effect at Short-wavelength Automated Perimetry (SWAP) using the Swedish Interactive Threshold Algorithm (SITA) program over the central 24 degrees on patients with ocular hypertension experienced with standard automated perimetry.

METHODS

Twenty-seven patients underwent 5 SITA SWAP tests at intervals of 5+/-2 days in a randomized eye. Learning effect was defined as an improvement in results for duration, perimetric indices, foveal sensitivity, Glaucoma Hemifield Test, number of points with a P<5% and <1% in the total, and pattern deviation maps, total, central, paracentral, peripheral, and quadrant sensitivity.

RESULTS

Learning effect was shown for foveal sensitivity (P=0.006, analysis of variance), which was significantly different only between the first (23.0 dB+/-4.1 dB) and the last test (24.7 dB+/-3.8 dB, P=0.003, t test) and was not affected by any demographic or ophthalmic characteristics of the population. All the other parameters did not show any significant learning effect.

CONCLUSIONS

SITA SWAP is affected by a small learning effect interfering only with the first test, as opposite to full-threshold SWAP program, which previously showed severe learning artefacts. This fact may induce reconsideration of the clinical utilization of SWAP for the early diagnosis of glaucoma.

Correlation between blue-on-yellow perimetry and scanning laser polarimetry with variable corneal compensation measurements in primary open-angle glaucoma

OBJECTIVE

To investigate the correlation between blue-on-yellow perimetry (B/YP) indices and scanning laser polarimetry with variable corneal compensation (GDx VCC) parameters in primary open-angle glaucoma (POAG) patients, and to evaluate whether the two tests can detect similar glaucomatous damage.

METHODS

One eye each of 86 patients with POAG was chosen. All patients were examined with the Octopus 101 automated perimetry dG2 program using the dynamic strategy/normal method (white-onwhite perimetry, W/WP), with the dG2 program using the dynamic strategy/BY method (blue-on-yellow perimetry, B/YP), and with GDx VCC. Findings were analyzed by using Pearson's correlation analysis.

RESULTS

Of the 42 early glaucoma patients, 28 had both B/YP visual field loss and retinal nerve fiber layer (RNFL) defects detected by the GDx VCC measurements, and in 85.7% (24/28) of patients the regions of B/YP visual field defects corresponded to the RNFL defects detected by GDx VCC. All moderate and late glaucoma patients had both B/YP visual field loss and RNFL defects detected by GDx VCC, and in 95.5% (42/44) the regions of B/YP visual field defects corresponded to the RNFL defects detected by GDx VCC. A statistically significant correlation was found between B/YP mean sensitivity (MS) and the temporal-superior-nasal-inferior-temporal (TSNIT) average (r2>0.191, P>0.047) in the early glaucoma group, but no significant correlation was found between the W/WP indices and GDx VCC parameters. In the moderate to late glaucoma group, a low or moderate, but significant, correlation was found between B/YP MS and GDx VCC parameters (r2>0.286-0.405, P>0.001-0.01), with the most correlative parameter with B/YP MS being the TSNIT average. A low but significant correlation was also found between the B/YP mean defect (MD) and TSNIT average, superior average, inferior average, and nerve fiber indicator (NFI) (r2>0.188-0.271, P>0.013-0.044), and a low or moderate significant correlation was also found between the W/WP MS and MD and the GDx VCC parameters.

CONCLUSION

The presence of significant correlations between some B/YP indices and the GDx VCC parameters in glaucoma patients suggests that the two tests can detect similar areas and amounts of glaucomatous damage. These findings raise the possibility that both techniques can be used in clinical examinations to yield convergent data.

[Functional glaucoma diagnosis]

Achromatic perimetry is the gold standard in glaucoma diagnosis for detecting functional defects from glaucomatous optic neuropathy. Because achromatic perimetry is only able to detect scotomas after loss of up to 30-40% of retinal ganglion cells, early diagnosis using this method is rarely possible. Therefore, a lot of new perimetric procedures have been developed in recent years to detect new scotomas at a very early stage. This review summarizes the theoretical background of retinal ganglion cells in order to better understand the theoretical approaches of new perimetric methods. In addition, the most important commercial perimetric devices currently available are presented.

Diagnostic tools for glaucoma detection and management

Early diagnosis of glaucoma is critical to prevent permanent structural damage and irreversible vision loss. Detection of glaucoma typically relies on examination of structural damage to the optic nerve combined with measurements of visual function. To aid the clinician in evaluation of visual function and structure, computer-based devices such as confocal scanning laser ophthalmoscopy, scanning laser polarimetry, and optical coherence tomography provide quantitative assessments of structural damage, and visual function testing includes standard automated perimetry as well as selective techniques, including short-wavelength automated perimetry and frequency-doubling technology perimetry are available. This article will review current literature on diagnostic modalities available for glaucoma with emphasis on the best evidence available in the literature to support their use in clinical practice.

Comparing the full-threshold and Swedish interactive thresholding algorithms for short-wavelength automated perimetry

PURPOSE

To compare the Swedish interactive thresholding algorithm (SITA) with the full-threshold (FT) strategy for short-wavelength automated perimetry (SWAP).

METHODS

One eye of 286 patients with glaucomatous optic neuropathy (GON) and 289 age-matched participants without GON from the Diagnostic Innovations in Glaucoma Study (DIGS) and the African Descent and Glaucoma Evaluation Study (ADAGES) were classified with optic disc stereophotographs taken within 6 months of visual field testing, conducted within a 3-month period. Six parameters were derived per test, including pattern standard deviation (PSD) and the number of pattern deviation plot (PDP) points triggered at <1%. Receiver-operating characteristic (ROC) analysis equated the tests for specificity (80%, 90%, and 95%). Sensitivities of parameters with the highest area under the curve (AUC) and STATPAC (Carl Zeiss Meditec, Inc., Dublin, CA) PSD were compared. Agreement, severity, and test duration between algorithms were assessed.

RESULTS

Sensitivities were not different between algorithms using PSD. With PDP <1%, SWAP-FT was more sensitive (35%) than SWAP-SITA (29%) at 95% specificity (P<0.05). Sensitivity and specificity using the STATPAC PSD at 95% (P<5%) and 99.5% (P<0.05%) was similar between algorithms. Severity correlated significantly between algorithms (P<0.001), although there was bias for SWAP-SITA to suggest more severe loss. SWAP-SITA required significantly less test time than did SWAP-FT (P<0.001). Mean differences in PSD, PDP <1%, and MD between algorithms were not clinically significant.

CONCLUSIONS

Both algorithms performed similarly when equated for specificity. The reduced test duration makes SWAP-SITA the better choice. Testing with both algorithms within a short period is recommended for confirmation of results when switching from FT to SITA.

Visual function-specific perimetry to identify glaucomatous visual loss using three different definitions of visual field abnormality

PURPOSE

To compare the most recent versions of standard automated perimetry (SAP), short-wavelength automated perimetry (SWAP), and frequency-doubling technology (FDT) using three definitions of visual field (VF) abnormality: single-test abnormality, abnormality confirmed by the same test, and abnormality confirmed by a different test.

METHODS

Data obtained from one eye of each of 174 patients with glaucoma and 164 age-matched healthy control subjects from the Diagnostic Innovations in Glaucoma Study and African Descent and Glaucoma Evaluation Study were included, based on the appearance of the optic disc on stereophotographs. Each participant had two reliable 24-2 SAP-SITA, SWAP-SITA, and Matrix FDT tests. Receiver operating characteristic (ROC) curves were generated for the PSD of each test to equate the tests at 90% and 95% specificity. SAP, SWAP, and FDT were compared under each definition of VF abnormality by assessing the sensitivities, the agreement between tests and the overlap in deficit location at these set specificities. The tests were also compared using the machine-derived PSD.

RESULTS

At a set specificity of 95%, single-test sensitivities of 30% (SAP), 29% (SWAP), and 28% (FDT) were observed (all P > 0.05). Sensitivities ranged from 24% to 27% (all P > 0.05) when same-test confirmation was used and from 20% to 23% (all P > 0.05) when different-test confirmation was used. SAP/SAP sensitivity was higher than all different-test combinations (all P < 0.05), and SWAP/FDT sensitivity was lower than all same-test combinations (all P < 0.05).

CONCLUSIONS

Confirming VF abnormality is important and optimal when an abnormal SAP is confirmed by a subsequent SAP or SWAP test.

Update on the pattern electroretinogram in glaucoma

PURPOSE

To review the efficacy of the pattern electroretinogram (PERG) in early diagnosis of glaucoma.

METHODS

Stimulation parameters of check size and temporal frequency are considered. Analyses of various peaks (P50, N95, the N95/P50) and Fourier steady-state are considered. The relation to visual field defects is explored.

RESULTS

The PERG is markedly alterated in glaucoma. It shows amplitude reductions in (still) normal areas of the visual field. Optical imaging on the retina needs to be optimal. Higher temporal frequency (>10 reversals/s) improves the sensitivity to detect glaucoma compared with transient stimulation. The ratio between the amplitudes to 0.8 degrees checks and to 16 degrees checks, "PERG ratio," exploits a check size-specific reduction in early glaucoma and reduces variability. Longitudinal studies suggest that the PERG can indicate incipient glaucoma damage before evidence from the visual field.

CONCLUSIONS

The PERG is a demanding electrophysiological technique that can serve as a sensitive biomarker for retinal ganglion cell function. With appropriate paradigms, PERG assists in identifying those patients with elevated interocular pressure in whom glaucoma damage is incipient before visual field changes occur.

Rarebit perimetry and frequency doubling technology in patients with ocular hypertension

PURPOSE

To test the capability of rarebit perimetry (RP), a recent non-conventional perimetric technique, in detecting early functional damage in subjects with ocular hypertension (OHT) and to compare RP findings with those obtained by frequency-doubling technology (FDT) perimetry.

METHODS

Thirty patients with OHT were matched with 30 healthy subjects. All were tested with RP and FDT. Frequency-doubling technology mean deviation (MD) and pattern standard deviation (PSD), as well as RP mean hit rate (MHR), of the two groups were analyzed. The agreement between the two techniques was tested by Kappa analysis.

RESULTS

In the OHT group the mean (SD) FDT MD was 0.5 (2.1), the mean (SD) FDT PSD was 4.2 (1.6), and the mean (SD) RP MHR was 81.4 (6.7). In the control group, corresponding values were mean (SD) FDT MD 1.1 (1.4), mean (SD) FDT PSD 3.0 (0.3), mean (SD) RP MHR 96.2 (2.0). The differences between the two groups were not significant for the studied indexes. Eleven (36.6%) out of the 30 OHT eyes had abnormal RP results; 12 (40.0%) eyes had abnormal FDT results. Five (16.6%) eyes had abnormal RP and FDT findings. Only 1 eye (3.3%) in the control group had abnormal RP results and 3 eyes (10.0%) had abnormal FDT results. RP and FDT showed a moderate agreement (Kappa=0.43; 95% CI: 0.42 to 0.51).

CONCLUSIONS

RP and FDT showed VF defects not shown in standard automated perimetry in the OHT group. This may be indicative of an increased risk in developing glaucoma, even if a gold standard for detecting subtle defects is not currently available. RP has the additional advantage of not requiring any expensive device to be used. The poor agreement between these techniques in identifying eyes with early damage warrants further investigations. Large longitudinal studies are needed before defining the role of RP in early glaucoma diagnosis.

Influence of learning effect on blue-on-yellow perimetry

PURPOSE

Some studies have found that a significant blue-on-yellow perimetry (B/YP) learning effect exists in patients with ocular hypertension (OHT) or open-angle glaucoma who were experienced in standard automated perimetry. However, very little is known about the B/YP learning effect in normal subjects and patients without previous white-on-white perimetry (W/WP) experience. Meanwhile, it is unclear whether the B/YP learning effect is influenced by age and refraction.

METHODS

Twenty healthy subjects, 26 OHT and 14 primary open angle glaucoma (POAG) patients, underwent three full-threshold B/YP tests at intervals of 7 to 21 days. Of the 60 subjects, 38 had no previous W/WP experiences, 22 had previous W/WP experiences for at least two times. The parameters investigated to detect a learning effect were the perimetric indices and the test duration (TD).

RESULTS

Learning effects were demonstrated for mean deviation (MD), pattern standard deviation (PSD), short-term fluctuation (SF), and TD. Significant differences were found between the MD, PSD, SF, and TD of the first test and those of the second and third tests (p<0.05). However, no difference was found between those parameters of the second and third tests. No statistically significant differences were noted in terms of MD1st-2nd, MD1st-3rd, PSD1st-2nd, PSD1st-3rd, TD1st-2nd, and TD1st-3rd between the group with W/WP experience and the group without previous W/WP experience (p>0.05). No statistically significant differences were noted in terms of those parameters among the normal subjects and the patients with OHT or POAG (p>0.05). No significant difference was found in the B/YP learning effect among various age groups (p>0.05) and among various refraction groups (p>0.05).

CONCLUSIONS

A significant learning effect was observed between the first and the second or third tests and the perimetric indices appeared improved at full-threshold B/YP. The previous W/WP experience and the subject age and refraction did not influence the B/YP learning effect. This above all should be taken into account when considering the clinical use of this test to avoid erroneous diagnostic conclusions.

The photopic negative response of the blue-on-yellow flash-electroretinogram in glaucomas and normal subjects

The photopic negative response of the flash-electroretinogram driven by the middle- and long-wavelength cones has been shown to be reduced in non-human primates with experimental glaucoma and in human patients with glaucoma. The photopic negative response for the blue-sensitive response has been studied using a blue-green silent-substitution-technique on a red background. The aim of this study was to re-evaluate the value of the photopic negative response of the blue-sensitive pathway in glaucoma using a conventional flash-electroretinogram. In 37 eyes of 37 controls (age: 53 +/- 13.6 years) and 37 eyes of 37 patients with open-angle glaucoma of different perimetric visual field defects (age: 58.3 +/- 10 years; MD: 11.7 +/- 6.7 dB) of the Erlangen glaucoma registry Ganzfeld flash-electroretinograms (LKC, UTAS 3000) were recorded using blue Xenon-flashes of increasing photopic luminance (0.013, 0.018, 0.030, and 0.052 cd s/m(2); 440 nm) on a bright yellow background (238 cd/m(2); 550 nm) after 2 min of light adaptation. Amplitudes and implicit times of the photopic negative response and of L&M-cone- and S-cone-driven b-waves were compared between glaucomas and controls for all flash energies (unpaired t-test). The amplitudes of the photopic negative response were significantly reduced in glaucoma patients for all flash energies (P < 0.001). The implicit times of L&M-cone-driven b-wave (0.013, 0.018, 0.030, and 0.052 cd s/m(2)) and S-cone-driven b-wave (0.030 and 0.052 cd s/m(2)) were significantly prolonged in glaucoma patients (P < 0.05). The changes in these implicit times, however, are very small (1.5 ms or less). The other measures did not differ significantly. The amplitude of the photopic negative response and the implicit times of the L&M-cone and S-cone b-wave in the same responses of the blue-on-yellow flash-electroretinogram are potentially useful in the evaluation of inner-retinal function in glaucoma.

Short-wavelength automated perimetry and frequency-doubling technology perimetry in glaucoma

Standard automated perimetry (SAP) is today still the clinical standard for the management of glaucoma and its progression, though it has been shown that it may detect the disease only after the death of a high number of retinal ganglion cells (RGCs). A number of "unconventional" perimetries have recently been evaluated by several clinical studies which showed their ability to identify the earliest glaucoma changes; the most promising of these techniques are short-wavelength automated perimetry (SWAP) and frequency-doubling technology perimetry (FDT). The applicability of these techniques is still limited by a number of factors: the limited economic resources allocated to perimetry; the paucity of well-conducted, prospective longitudinal studies showing the superiority of SWAP and FDT over SAP; and the lack of a consensus on the criteria to define test abnormality with these techniques. The aim of this article is to review the rationale, the limits, and the potentiality of SWAP and FDT for glaucoma management and to summarize the tasks required to improve the clinical usefulness of these two instruments in the future.

Early detection of glaucoma by means of a novel 3D computer-automated visual field test

PURPOSE

A recently devised 3D computer-automated threshold Amsler grid test was used to identify early and distinctive defects in people with suspected glaucoma. Further, the location, shape and depth of these field defects were characterised. Finally, the visual fields were compared with those obtained by standard automated perimetry.

PATIENTS AND METHODS

Glaucoma suspects were defined as those having elevated intraocular pressure (>21 mm Hg) or cup-to-disc ratio of >0.5. 33 patients and 66 eyes with risk factors for glaucoma were examined. 15 patients and 23 eyes with no risk factors were tested as controls. The recently developed 3D computer-automated threshold Amsler grid test was used. The test exhibits a grid on a computer screen at a preselected greyscale and angular resolution, and allows patients to trace those areas on the grid that are missing in their visual field using a touch screen. The 5-minute test required that the patients repeatedly outline scotomas on a touch screen with varied displays of contrast while maintaining their gaze on a central fixation marker. A 3D depiction of the visual field defects was then obtained that was further characterised by the location, shape and depth of the scotomas. The exam was repeated three times per eye. The results were compared to Humphrey visual field tests (ie, achromatic standard or SITA standard 30-2 or 24-2).

RESULTS

In this pilot study 79% of the eyes tested in the glaucoma-suspect group repeatedly demonstrated visual field loss with the 3D perimetry. The 3D depictions of visual field loss associated with these risk factors were all characteristic of or compatible with glaucoma. 71% of the eyes demonstrated arcuate defects or a nasal step. Constricted visual fields were shown in 29% of the eyes. No visual field changes were detected in the control group.

CONCLUSIONS

The 3D computer-automated threshold Amsler grid test may demonstrate visual field abnormalities characteristic of glaucoma in glaucoma suspects with normal achromatic Humphrey visual field testing. This test may be used as a screening tool for the early detection of glaucoma.

Open angle glaucoma effects on preattentive visual search efficiency for flicker, motion displacement and orientation pop-out tasks

BACKGROUND/AIM

Preattentive visual search (PAVS) describes rapid and efficient retinal and neural processing capable of immediate target detection in the visual field. Damage to the nerve fibre layer or visual pathway might reduce the efficiency with which the visual system performs such analysis. The purpose of this study was to test the hypothesis that patients with glaucoma are impaired on parallel search tasks, and that this would serve to distinguish glaucoma in early cases.

METHODS

Three groups of observers (glaucoma patients, suspect and normal individuals) were examined, using computer-generated flicker, orientation, and vertical motion displacement targets to assess PAVS efficiency. The task required rapid and accurate localisation of a singularity embedded in a field of 119 homogeneous distractors on either the left or right-hand side of a computer monitor. All subjects also completed a choice reaction time (CRT) task.

RESULTS

Independent sample T tests revealed PAVS efficiency to be significantly impaired in the glaucoma group compared with both normal and suspect individuals. Performance was impaired in all types of glaucoma tested. Analysis between normal and suspect individuals revealed a significant difference only for motion displacement response times. Similar analysis using a PAVS/CRT index confirmed the glaucoma findings but also showed statistically significant differences between suspect and normal individuals across all target types.

CONCLUSIONS

A test of PAVS efficiency appears capable of differentiating early glaucoma from both normal and suspect cases. Analysis incorporating a PAVS/CRT index enhances the diagnostic capacity to differentiate normal from suspect cases.

The loss of visual function in glaucoma

This article reviews innovative techniques for assessing the visual field and for examining glaucoma patients for evidence of visual field progression. The authors discuss the algorithms for assessing change in visual fields used in each of several multicenter studies sponsored by the National Eye Institute. The authors also give a brief review of 2 currently available alternatives to standard automated perimetry. Both are visual function specific tests that attempt to evaluate a subpopulation of retinal ganglion cells. Shortwavelength automated perimetry isolates the small bistratified (blue-yellow) ganglion cells, and Frequency Doubling Technology Perimetry tests functions that should be primarily handled by the magnocellular ganglion cells. These new perimetric procedures are promising as improvements over standard automated perimetry; however, there is still no agreed upon method for determination of glaucomatous visual field progression.

Frequency Doubling Perimetry and Short-Wavelength Automated Perimetry to Detect Early Glaucoma

PURPOSE

To compare the ability of short-wavelength automated perimetry (SWAP) and frequency doubling perimetry (FDP) to detect early glaucoma damage.

DESIGN

Prospective case-control study using a comparative case series.

PARTICIPANTS

Forty-two patients with preperimetric glaucomatous optic nerve damage and a normal standard achromatic perimetry (SAP) in 1 eye, but with contralateral SAP abnormalities, and 35 normals.

METHODS

Forty-two patients and 35 normals underwent SWAP and FDP (Humphrey 24-2; Carl Zeiss Meditec, Inc., Dublin, CA). Correlations of mean deviation (MD) and pattern standard deviation (PSD) of the 2 groups were calculated. The number of defects at P<0.05 and P<0.01 on total deviation (TD) and pattern deviation (PD) plots were compared. Diagnostic precision and agreement on location of abnormalities were determined.

MAIN OUTCOME MEASURES

Correlations and comparisons of global indices between SWAP and FDP: MD, PSD, TD, and PD abnormal number of points.

RESULTS

Significant correlations in the glaucoma group were found between SWAP and FDP for MD (r = 0.54; P<0.008) and PSD (r = 0.49; P<0.001). Defects on the TD and PD plots were detected more frequently by FDP in the glaucoma group, although they were significant only for PD at P<0.01 (P = 0.024). Areas under receiver operator characteristic curves for MD of SWAP and PSD of FDP were 0.74 and 0.67, respectively (P = 0.37). Using defined defect criteria, FDP had a significantly higher sensitivity (72% vs. 54%; P = 0.02) and similar specificity (53% vs. 44%; P = 0.12) compared with SWAP. Agreement on defect location was moderate (kappa, 0.46). Testing time for SWAP was longer than for FDP in both glaucomatous and normal eyes (P<0.001).

CONCLUSIONS

Short-wavelength automated perimetry and FDP showed similar ability to detect visual dysfunction in patients with preperimetric glaucoma. Long-term follow-up is required to define their role in predicting subsequent SAP defects.

Selective perimetry in glaucoma diagnosis

PURPOSE OF REVIEW

Selective perimetry evaluates visual function by using visual stimuli that attempt to target specific subpopulations of retinal ganglion cells, which is designed to improve sensitivity to detect glaucomatous functional loss. This paper reviews recent studies that have assessed the characteristics of new strategies/programs of selective perimetry.

RECENT FINDINGS

Selective perimetry is usually compared against an existing standard technique--standard automated perimetry. Recent studies did not consider standard automated perimetry results as part of inclusion/exclusion criteria, avoiding selection bias and permitting fair comparisons between perimetry techniques. Furthermore, the Swedish Interactive Threshold Algorithm is replacing Full-Threshold as the standard automated perimetry gold-standard strategy, and comparisons of the diagnostic performance of function-specific perimetry may be influenced by which standard automated perimetry technique is used as the reference. These factors may impact our perception about the role of selective perimetry in glaucoma management.

SUMMARY

The lack of a perfect gold-standard diagnostic test for glaucoma limits the interpretation of results from cross-sectional studies evaluating visual field tests. Nevertheless, evidence suggests that visual dysfunction in eyes with early glaucoma varies significantly between individuals and no single technique is superior to the others in all patients. A multimodal functional assessment may be more effective in detecting/quantifying visual impairment associated with early glaucoma.

Influence of clinical factors on blue-on-yellow perimetry for diabetic patients without retinopathy: comparison with white-on-white perimetry

PURPOSE

To investigate the influence of clinical factors (duration of diabetes mellitus, fasting blood sugar level, fructosamine concentration, and hemoglobin A1c) on blue-on-yellow (B-on-Y) perimetry compared with white-on-white (W-on-W) perimetry for diabetics without retinopathy.

METHODS

Both B-on-Y perimetry and W-on-W perimetry were performed for 33 diabetics without retinopathy. Thirty-three subjects with healthy eyes served as age-matched controls.

RESULTS

For both diabetic patients and controls, mean deviation (MD) and corrected pattern SD of perimetry showed no difference irrespective of B-on-Y or W-on-W perimetry. For diabetics, MD of B-on-Y perimetry decreased in proportion to the morbid period with diabetes mellitus, with the same being true with deterioration of the clinical factors. Multiple regression analysis disclosed no differences in MD of clinical factors for W-on-W perimetry, despite the duration of diabetes mellitus exerting a significant influence on MD of B-on-Y perimetry.

CONCLUSION

Even at the premorbid stage of diabetic retinopathy, longer duration of diabetes mellitus and longer persistence of poorly controlled diabetes mellitus are associated with an insidious progress of dysfunction in the retinal blue cone system.

Relationship between short wavelength perimetry and central corneal thickness values in ocular hypertensive subjects

PURPOSE

To evaluate the results of short wavelength perimetry (SWAP) of ocular hypertensive (OHT) patients and correlate these findings with central corneal thickness (CCT) measurements.

METHODS

Thirty-seven OHT patients with a mean age of 50.2+/-8.2 (SD) years and 30 control subjects with a mean age of 50.3+/-8.5 (SD) years were included in this study. A questionnaire was applied to patients to evaluate the demographic risk factors that may predict glaucoma development. After a detailed ophthalmologic examination, achromatic and short wavelength perimetries and ultrasonic pachymetry were performed and the results were compared between the two groups with Student t test and Mann-Whitney U test. A p value<0.05 is considered as statistically significant.

RESULTS

Mean CCT was higher in the OHT group (right eye; 558.13+/-28.39 microm and left eye; 558.94+/-27.30 microm) when compared with the control subjects (524.66+/-30.53 microm and 525.86+/-30.46 microm, respectively) (p<0.01). A significant positive correlation was found between CCT measurements and intraocular pressure (r=0.5, p<0.001). Four right eyes (10.8%) and five left eyes (13.5%) of OHT patients had defects in SWAP. OHT patients with SWAP abnormalities had significantly lower CCT measurements in right (527.25+/-17.34 microm) and left eye (528.80+/-13.60 microm) when compared with OHT patients without SWAP defects (561.87+/-27.29 microm and 563.65+/-25.92 microm, respectively) (p<0.05). Significant correlations were found between CCT and SWAP MD, PSD, and CPSD (p<0.05).

CONCLUSIONS

OHT patients with SWAP abnormalities had significantly lower CCT measurements than those without. CCT is considered as a risk factor for the development of glaucomatous damage in OHT patients.

Learning Effect of Short-wavelength Automated Perimetry in Patients With Ocular Hypertension

AIM

To evaluate the learning effect of short-wavelength automated perimetry (SWAP) on a group of patients with ocular hypertension experienced with standard automated perimetry (SAP).

METHODS

Thirty patients with ocular hypertension underwent 5 full-threshold SWAP tests at intervals of 7+/-2 days. The parameters investigated to detect a learning effect were duration, the perimetric indices, and the number of points with a P of <5% and 1% in the total and pattern deviation maps. Differences in learning effect were also evaluated by comparing the sensitivities of central, paracentral, and peripheral areas, hemifields and quadrants.

RESULTS

Learning effects were demonstrated for mean defect (P<0.0001, analysis of variance), duration (P=0.0001), the number of points with P<5% in the pattern deviation map (P=0.003), and short fluctuations (P=0.03). The effect was greater in the peripheral than in central areas (P=0.04). Mean defect was the most sensitive parameter, for which the learning effect was statistically significant between the first and the fifth test.

CONCLUSIONS

The results of this study demonstrate a significant learning effect at full-threshold SWAP. This may limit the efficacy of this kind of perimetry in detecting early glaucoma, and should therefore be carefully considered when creating normative databases for new SWAP strategies.

Long-term effects of tibolone on ocular functions in postmenopausal women

Hormone replacement therapy has been widely used for the prevention of postmenopausal osteoporosis and treatment of climacteric symptoms for many years, but its effect on ocular functions remains unclear. The aim of the study was to evaluate the long-term effects of tibolone on ocular functions in postmenopausal women. A total of 77 healthy women with at least 1 year of spontaneous menopause were enrolled in the study. Forty women were treated with tibolone for 6 months and 37 women were left untreated. All these patients underwent ophthalmic examination including visual acuity, intraocular pressure (IOP), tear functions, blue-on-yellow and white-on-white Humphrey visual field (HVF), visual evoked potentials (VEP) and electroretinography (ERG). There were significant differences in mean deviation of blue-on-yellow HVF, and oscillatory potentials (O1, O2, and O4) in the ERGs of the chronic tibolone users and the control (P < 0.0001, P = 0.001, P < 0.0001 and 0.05, respectively). However, no significant differences were observed in visual acuity, IOP, tear functions, white-on-white HVF and VEP. We concluded that, although tibolone had no effects on visual acuity, IOP, tear functions and VEP, it might cause some early adverse effects on the electrophysiologic and structural characteristics of the retina, which are detected by these sensitive assays. Randomized placebo-controlled studies with larger groups are needed in future research.

Detecting early functional damage in glaucoma suspect and ocular hypertensive patients with the multifocal VEP technique

PURPOSE

To determine whether the multifocal visual evoked potential (mfVEP) technique can detect early functional damage in ocular hypertensive (OHT) and glaucoma suspect (GS) patients with normal standard achromatic automated perimetry (SAP) results.

PATIENTS AND METHODS

Twenty-five GS patients (25 eyes), 25 patients with OHT (25 eyes), and 50 normal controls (50 eyes) were enrolled in this study. All GS, OHT and normal control eyes had normal SAP as defined by a pattern standard deviation and mean deviation within the 95% confidence interval and a glaucoma hemifield test within normal limits on the Humphrey visual field 24-2 program. Eyes with GS had optic disc changes consistent with glaucoma with or without raised intraocular pressure (IOP), and eyes with OHT showed no evidence of glaucomatous optic neuropathy and IOPs >or=22 mm Hg. Monocular mfVEPs were obtained from both eyes of each subject using a pattern-reversal dartboard array with 60 sectors. The entire display had a radius of 22.3 degrees. The mfVEPs, for each eye, were defined as abnormal when either the monocular or interocular probability plot had a cluster of 3 or more contiguous points with P<0.05 and at least 2 of these points with P<0.01.

RESULTS

The mfVEP results were abnormal in 4% of the eyes from normal subjects. Abnormal mfVEPs were detected in 20% of the eyes of GS patients and 16% of the eyes of OHT patients. Significantly more mfVEP abnormalities were detected in GS patients than in normal controls. However, there was no significant difference in mfVEP results between OHT patients and normal controls.

CONCLUSIONS

The mfVEP technique can detect visual field deficits in a minority of eyes with glaucomatous optic disks and normal SAP results.

Normal age-related sensitivity loss for a variety of visual functions throughout the visual field

PURPOSE

The purpose of this study is to compare the rate of age-related decline, the magnitude of practice effects, and test-retest variability among normal subjects using six different tests of visual function.

METHODS

One hundred normal subjects aged between 20 and 85 were enrolled in the study. Six visual field test procedures were used consisting of standard automated perimetry (SAP), short wavelength automated perimetry (SWAP), temporal modulation perimetry (TMP), frequency-doubling technology perimetry (FDT), detection acuity perimetry (DAP),and resolution acuity perimetry (RAP). To facilitate direct comparison, the results for each test were divided by that test's estimated dynamic range.

RESULTS

Of the three tests used clinically most commonly, SWAP exhibited the greatest aging and practice effects and test-retest variability followed by FDT with SAP exhibiting the least. RAP was the most variable test followed by TMP.

CONCLUSIONS

These results should be taken into account when evaluating glaucomatous loss using different functional tests and when comparing the performance, predictive power, and speed of detection of the different tests.

Humphrey matrix frequency doubling technology perimetry and optical coherence tomography measurement of the retinal nerve fiber layer thickness in both normal and ocular hypertensive subjects

PURPOSE

The purpose of this study was to determine by means of the Humphrey Matrix frequency doubling technology (FDT) perimetry and the optical coherence tomography (OCT) retinal nerve fiber layer (RNFL) thickness measurement whether functional and/or structural differences exist between normal and ocular hypertensive (OHT) subjects.

PATIENTS AND METHODS

One eye of 60 consecutive normal individuals and 60 OHT subjects was enrolled in this prospective observational comparative case series study. All subjects were examined at either the Ophthalmology Clinic, University of Chieti-Pescara, Chieti, Italy or the Department of Ophthalmology, S. Maria della Misericordia Hospital, Udine, Italy. All subjects underwent a full ophthalmic examination, including visual acuity, slit-lamp biomicroscopy, central corneal thickness ultrasound pachymetry measurement, achromatic automated perimetry, Matrix FDT perimetry, stereoscopic optic nerve head photography, and OCT. Matrix FDT perimetry mean deviation (MD), pattern standard deviation, glaucoma hemifield test, and 12 OCT RNFL thickness parameters were examined. Student t test, Bonferroni correction for multiple comparisons and receiver operator characteristics curve areas (AUROCs) were used to find any discrimination function between healthy and OHT eyes. Sensitivities at 83% and 92% specificities were reported.

RESULTS

The FDT MD scores ranged from -1.10 to +3.80 decibels (db) in normal individuals and from -4.75 to +3.20 db in OHT subjects. The comparison between the average MD in the 2 groups showed a statistically significant difference (P=0.024). OCT showed a statistically significant difference between the 2 groups when examining the ratio between the inferior and the superior mean RNFL thickness (P=0.004). For OCT, the parameter with the largest AUROC for discriminating between healthy and hypertensive eyes was the ratio between the mean inferior and superior RNFL thickness (AUROC=0.85, sensitivity=75% at specificity=83%, sensitivity=67% at specificity=92%). For Matrix FDT perimetry, the parameter with the largest AUROC was MD (AUROC=0.78, sensitivity=67% at specificity=83%, sensitivity=58% at specificity=92%).

CONCLUSIONS

Our results suggest that OHT eyes having a normal achromatic automated perimetry and a normal clinical disc appearance cannot be differentiated from normal eyes using conventional OCT parameters. When analyzing the ratio between inferior and superior average RNFL thickness, however, a significant difference is evident between healthy and hypertensive eyes. Using Matrix FDT perimetry, a significant difference in MD seems to exist between these 2 groups of eyes. The AUROCs confirm that OCT Iavg/Savg and Matrix FDT MD show the greatest sensitivity and specificity among the examined OCT and Matrix FDT parameters.

Effect of the AcrySof Natural intraocular lens on blue–yellow perimetry

PURPOSE

To assess the differences in blue-yellow perimetry values in patients with an AcrySof Natural intraocular lens (IOL) in 1 eye and a conventional AcrySof IOL in the fellow eye.

SETTING

Cataract and glaucoma clinics of a medical school associated with a public hospital in Brazil.

METHODS

Forty-six patients had bilateral phacoemulsification and implantation of an AcrySof SN60AT IOL (Alcon) in 1 eye and an MA30AC IOL (Alcon) in the fellow eye. Blue-yellow perimetry was performed in both eyes, and the data were analyzed in blinded fashion using the Mann-Whitney U test.

RESULTS

No statistically significant differences were observed in short-wavelength automated perimetry (SWAP) values between the 2 IOLs.

CONCLUSION

There was no interference by the yellow filter of the AcrySof Natural IOL in blue-yellow perception as determined by SWAP.

Diagnostic sensitivity of fast blue-yellow and standard automated perimetry in early glaucoma: a comparison between different test programs

PURPOSE

To compare the ability of Fast Swedish interactive threshold algorithm (SITA) short-wavelength automated perimetry (SWAP), lengthier full-threshold SWAP, and standard automated perimetry (SAP) using the SITA Fast program to detect early glaucomatous visual field loss.

DESIGN

Cross-sectional prospective study of perimetric diagnostic sensitivity as defined by reference limits determined in the same healthy participants for all 3 test programs.

PARTICIPANTS

One hundred one patients with ocular hypertension, or suspect or early manifest glaucoma.

METHODS

One eye of each patient was tested with 2 blue-yellow perimetric programs: the SITA and full-threshold SWAP and the SAP SITA Fast program.

MAIN OUTCOME MEASURES

Glaucomatous visual field loss, defined as number of significantly depressed test point locations or the number of clusters of such test points.

RESULTS

No significant difference in number of significantly depressed test point locations between the 3 programs could be detected, neither at the P<5% limit nor at the P<2% limit. The difference in number of points depressed below the fifth percentile was 0.5 between full-threshold SWAP and SITA SWAP, 1.09 between full-threshold SWAP and SAP, and 1.04 between SITA SWAP and SAP. The number of eyes showing clusters of significantly depressed points also was similar with the 3 test programs: full-threshold SWAP identified clusters in 66 eyes, SITA SWAP identified clusters in 67 eyes, and SITA Fast SAP identified clusters in 65 eyes. Average test time was 12.0 minutes using full-threshold SWAP, 4.1 minutes with SITA SWAP, and 3.5 with SITA Fast.

CONCLUSIONS

The SITA SWAP identified at least as much glaucomatous visual field loss as the older full-threshold SWAP, although test time was considerably reduced. Conventional SAP using SITA Fast was not significantly less sensitive than either of the 2 SWAP programs.

Visual-Evoked Response, Pattern Electroretinogram, and Psychophysical Magnocellular Thresholds in Glaucoma, Optic Atrophy, and Dyslexia

PURPOSE

The purpose of this study is to compare visual-evoked response (VEP) pattern electroretinogram (PERG) and psychophysical thresholds to the same stimulus, designed to be optimal for the magnocellular system, in suspects and patients with early glaucoma, patients with optic nerve disease, dyslexic children, and age-matched controls.

METHODS

Stimuli were low spatial frequency sinusoidal luminance profile gratings abruptly phase reversing at 7.14 Hz. Electrophysiological recordings were made at 50%, 30%, 20%, 10%, and 5% contrast. Threshold was the lowest contrast evoking a clear response at the stimulus frequency. Three independent judges scored the traces. Psychophysical thresholds were obtained by ascending and descending method of limits. VEPs and PERGs to International Society for Clinical Electrophysiology of Vision (ISCEV) standards and to increasing spatial frequencies were obtained as parvocellular specific controls. Patients were diagnosed independently by the referring professionals.

RESULTS

Parvocellular-specific responses were normal, except in cases with explicable visual acuity loss. The judges scores correlated highly (> 0.9). VEPs and PERGs correlated highly and each correlated less well with psychophysics in normals, glaucoma, and dyslexia but the opposite occurred in optic nerve disease. VEPs had the lowest normal values and least variance (all adults < 5%, children < 10%, PERGs < 20%). In glaucoma, VEP magnocellular deficits occurred in 85% of recently diagnosed positive cases, 48% of high-risk suspects, 39% of low-risk suspects, and ocular hypertensives. Approximately 28% of dyslexics had VEP magnocellular deficits. PERG losses were less frequent. There was a clear dichotomy and low correlations between psychophysics and electrophysiology both within and between groups. Psychophysical threshold elevations were absent in all glaucoma groups, often large in optic atrophy and small (2.5%) but highly significant in dyslexia.

CONCLUSION

Contrast thresholds to magnocellular-specific stimuli are consistent in cortex and retina. VEPs are more reliable. Psychophysics seems to tap different mechanisms. VEPs are very sensitive to early glaucoma. The lack of VEP loss in dyslexia suggests the other losses are artifactual. Further research is needed to see if stimuli even more like the frequency-doubling technology are more useful clinically.