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

Comparison of ZETA Fast (PTS) (Optopol Technology) and Humphrey SITA Fast (SFA) (Carl Zeiss Meditec) Perimetric Strategies

Purpose

To compare two threshold strategies for visual field assessment, ZETA Fast (Optopol Technology) and Humphrey SITA Fast (Carl Zeiss Meditec), in controls and subjects with glaucoma. Patients and Methods. A prospective case-control study was carried out in which the clinical practice study included 26 controls and 26 glaucoma subjects. Testing for each strategy was monocular. Quantitative comparisons of mean deviation (MD), pattern standard deviation (PSD), visual field index (VFI), and test duration were made using two one-sided t-tests and Wilcoxon signed-rank tests. Confusion matrices were constructed to assess Optopol's detection as a proxy for Zeiss's detection of early glaucomatous defects. Receiver operating characteristic (ROC) curves were used to assess MD and PSD's discriminability.

Results

The difference in MD values (Optopol-Zeiss) was within the margin for controls (difference = 0.36, p=0.06), but not for glaucomatous subjects (difference = 2.16, p=1.0). The Optopol strategy took longer than the Zeiss strategy in both controls (difference = 23 seconds, p=0.001) and glaucomatous subjects (difference = 49 seconds, p < 0.001). PSD values were higher and VFI values were lower from Optopol in glaucomatous subjects (p < 0.001 and p=0.002). Optopol was 92% sensitive in capturing early glaucomatous defects with MD <−2 when compared to Zeiss (p < 0.001). ROC analysis shows Optopol yields higher discriminability than Zeiss for MD/PSD indices.

Conclusions

Both strategies enable effective identification of glaucomatous defects within 6 minutes; they also offer high sensitivity with a high correlation in global indices between the two strategies. The Optopol strategy is an alternative to the Zeiss counterpart with the limitation of a marginally longer testing protocol but a higher sensitivity of detecting glaucomatous defects.

Should clinical automated perimetry be considered for routine functional assessment of early/intermediate age-related macular degeneration (AMD)? A systematic review of current literature

Purpose

There is growing interest in functional testing for early/intermediate age‐related macular degeneration (iAMD). However, systematic evaluation of existing clinical functional tests is lacking. This systematic review examines evidence for using clinical automated perimetry in routine assessment of early/iAMD.

Recent findings

PubMed, Web of Science Core Collection, and Embase were searched from inception to October 2020 to answer, is there evidence of visual field defects in early/iAMD, and if so, are early/iAMD visual field defects linked to real‐world patient outcomes? Articles using clinical automated perimetry (commercially accessible and non‐modified devices/protocols) were included. Microperimetry was excluded as this has yet to be incorporated into clinical guidelines. The primary outcome was global visual field indices including mean deviation (MD), pattern standard deviation (PSD), mean sensitivity (MS) and frequency of defects. The secondary outcome was any real‐world patient outcome including quality of life and/or activities of daily living indices. Twenty‐six studies were eligible for inclusion and all studies were observational. There was consistent evidence of worsened MD, PSD, MS and frequency of defects for early/iAMD compared to normal eyes under photopic, low‐photopic and scotopic conditions. Meta‐analysis of studies using standard automated perimetry (SAP) under photopic conditions revealed worsened MD (−1.52dB [−2.27, −0.78 dB]) and MS (−1.47dB [−2, −0.94 dB]) in early/iAMD compared to normal eyes, representing large statistical effect sizes but non‐clinically meaningful reductions. There was insufficient data for meta‐analyses regarding other clinical automated perimetry protocols. Only one study assessed a real‐world patient outcome (on‐road driving performance), with no significant link to visual field outcomes in early/iAMD.

Summary

Significant reduction of global visual field indices is present in early/iAMD, but not clinically meaningful using SAP under photopic conditions. Translational relevance of visual field outcomes to patient outcomes in early/iAMD remains unclear. Thus, SAP under photopic conditions is unlikely to be useful for routine assessment of early/iAMD.

Choosing two points to add to the 24-2 pattern to better describe macular visual field damage due to glaucoma

BACKGROUND/AIMS

A recent study has shown that the paracentral upper visual field in the macular region is often affected in glaucoma and suggested that two test locations within the central 10° should be added to the Humphrey 24-2 visual field test pattern to detect such damage. This study employed data collected using a different visual field test pattern to determine whether the same two-test locations are supported as the most informative regarding visual field loss.

METHODS

A data set of 62 patients with glaucoma and 48 controls had visual field assessments on the Medmont perimeter M700 (Central Threshold or Glaucoma test). Twelve 24-2 locations within central 10° of visual field were derived by interpolation of the nearest neighbours of the Medmont data. The remaining 24 Medmont locations in the central 10° of the glaucomatous set were labelled as abnormal if their thresholds fell outside the lower 5th centile of the age-corrected values for the same location from the control group. All possible pairs of the 24 locations were then assessed for diagnostic power by counting the number of patients that had 0, 1 or 2 abnormal locations in a pair.

RESULTS

Overwhelmingly, pairs of locations in the superior macular region were more often abnormal than pairs in the inferior. About 50 pairs of locations had equivalent ability to detect damage, with the best pair having 74% of patients with at least one of the locations as abnormal, and 52% both.

CONCLUSIONS

Adding a pair of locations to the superior macular region of the Humphrey Visual Field 24-2 pattern increases the number of abnormal locations identified in individuals with glaucoma.

The effect of hypercapnia on the sensitivity to flicker defined stimuli

BACKGROUND/AIMS

To investigate the effect of increased CO2 levels on flicker defined stimuli.

METHODS

The sensitivity of two flicker defined tasks was measured in nine healthy, trained observers using the Flicker Defined Form (FDF) stimulus of the Heidelberg Edge Perimeter (HEP; Heidelberg Engineering) and Frequency Doubling Technology (FDT) stimulus of the Matrix perimeter (Carl Zeiss Meditec) during normoxia and 15% hypercapnia (end-tidal CO2 increased by 15% relative to baseline). HEP-FDF and Matrix-FDT sensitivities were analysed for the global field, superior and inferior hemifields and at specific matched eccentricities, using repeated measures analysis of variance. The main effect of hypercapnia on flicker sensitivity was analysed using regression models.

RESULTS

Higher flicker sensitivity outcomes with increasing CO2 values were found for HEP-FDF and Matrix-FDT with a statistically significant main effect for HEP-FDF global, superior and inferior hemifields (p<0.01 for all) as well as 6°, 18°, 12° and 24° eccentricities (p=0.03, 0.04, 0.01, 0.05, respectively). When comparing mean sensitivity values between normocapnia and hypercapnia conditions, no statistically significantly different results were found for HEP-FDF and Matrix-FDT (p>0.05).

CONCLUSIONS

As CO2 levels were increased in healthy young individuals, there was an associated increase in visual sensitivity that was only significant for HEP-FDF stimuli, highlighting the different mechanisms involved in processing each of HEP-FDF and Matrix-FDT stimuli. Mean visual sensitivity outcomes were found to be similar for normocapnia and hypercapnia suggesting that a capability to compensate for a mild and stable increase in systemic CO2 levels may exist.

Analysis of glistenings in hydrophobic acrylic intraocular lenses on visual performance

AIM

To assess patients' visual performance with glistenings in one piece soft hydrophobic acrylic intraocular lenses (IOLs) (Alcon) 2 years postoperatively.

METHODS

This cross section trial included 120 eyes with one piece IOL at 2 years postoperatively. Glistening was classified in 4 groups, ranging from 0 (none) to 3 (most evident) according to their severity in IOLs optics observed under a slit lamp. All eyes underwent a uncorrected and best-corrected visual acuity evaluation (UCVA and BCVA, LogMAR scale), a complete clinical examination, a contrast sensitivity (CS) evaluation by F.A.C.T chart, and a visual field test by Humphrey Field Analyzer ‖ (HFA). One-way ANOVA was used for quantitative data, while Pearson χ (2) test was used for qualitative data to analyze the visual function of 4 glistening groups.

RESULTS

Totally 120 eyes were enrolled with 30 eyes in each glistening group. There was no statistical correlation between glistening grades and patients' age, IOLs power, postoperative UCVA and BCVA (P>0.05). Quantificationally, CS values among each group were not statistically different. However, qualitative analysis showed there were more eyes in grade 3 group than in grade 0 group having abnormally declined CS at high spatial frequency (10% vs 36.7% at 18 cpd, P=0.029; 6.7% vs 26.7% at 12 cpd, P=0.013). Mean deviation (MD) of the visual field test was -2.14±2.31, -1.97±2.23, -3.02±3.17, -4.12±3.38 in group 0 to 3 respectively. There was a significant decrease in the most serious glistenings group (P =0.018).

CONCLUSION

Glistenings may potentially have an impact on contrast sensitivity at high spatial frequency and MD in visual field test.

Comparison of global indices and test duration between two visual field analyzers: Octopus 300 and Topcon SBP-3000

PURPOSE

To compare the global indices and test duration as measured by Octopus 300 and Topcon SBP-3000 perimeters. To our knowledge, this is the first study performed in this way.

METHODS

Eighty eyes of 40 glaucomatous and ocular hypertensive patients with previous perimetric experience had visual field tests with Octopus 300 (TOP strategy) and TOPCON SBP-3000. All pairs of tests were performed randomly on separate days, but within 1 month of each other. Taking into account reliability factors of both perimetric examinations, 54 eyes of thirty patients were eligible. Only one eye from each patient was considered. Mean sensitivity (MS), mean defect (MD), loss of variance (sLV-Octopus- and LV -Topcon-) and test duration times were considered.

RESULTS

A significant difference was found between the global indices and duration times of the Octopus and the Topcon perimeters (p < 0.05; Wilcoxon test). Moderate degrees of correlation were obtained for MS (Spearman's rho = 0.635; p < 0.001) and MD (Spearman's rho = 0.592; p = 0.001) measurements. There was no correlation between sLV and LV (Spearman's rho = 0.181; p = 0.337). Agreements between pairs of global indices were low as measured by concordance correlation coefficient.

CONCLUSION

Global indices measured by the Octopus and Topcon perimeters are significantly different, so direct comparison of the measured values is not reliable. Because of the poor association and agreement between values obtained by these two perimeters, indirect comparison is also inadvisable.

Mild systemic hypoxia and photopic visual field sensitivity

PURPOSE

Flickering stimuli increase the metabolic demand of the retina, making it a sensitive perimetric stimulus to the early onset of retinal disease. We determine whether flickering stimuli are a sensitive indicator of vision deficits resulting from acute, mild systemic hypoxia when compared to standard static perimetry.

METHODS

Static and flicker visual perimetry were performed in 14 healthy young participants while breathing 12% oxygen (hypoxia) under photopic illumination. The hypoxia visual field data were compared with the field data measured during normoxia. Absolute sensitivities (in dB) were analysed in seven concentric rings at 1°, 3°, 6°, 10°, 15°, 22° and 30° eccentricities as well as mean defect (MD) and pattern defect (PD) were calculated. Preliminary data are reported for mesopic light levels.

RESULTS

Under photopic illumination, flicker and static visual field sensitivities at all eccentricities were not significantly different between hypoxia and normoxia conditions. The mean defect and pattern defect were not significantly different for either test between the two oxygenation conditions.

CONCLUSION

Although flicker stimulation increases cellular metabolism, flicker photopic visual field impairment is not detected during mild hypoxia. These findings contrast with electrophysiological flicker tests in young participants that show impairment at photopic illumination during the same levels of mild hypoxia. Potential mechanisms contributing to the difference between the visual fields and electrophysiological flicker tests including variability in perimetric data, neuronal adaptation and vascular autoregulation are considered. The data have implications for the use of visual perimetry in the detection of ischaemic/hypoxic retinal disorders under photopic and mesopic light levels.

Persons with age-related maculopathy risk genotypes and clinically normal eyes have reduced mesopic vision

PURPOSE

To determine whether participants with normal visual acuity, no ophthalmoscopically signs of age-related maculopathy (ARM) in both eyes, and who are carriers of the CFH, LOC387715, and HRTA1 high-risk genotypes (gene-positive) have impaired rod- and cone-mediated mesopic visual function compared with persons who do not carry the risk genotypes (gene-negative).

METHODS

Fifty-three Caucasian study participants (mean 55.8 ± 6.1) were genotyped for CFH, LOC387715/ARMS2, and HRTA1 polymorphisms. Single-nucleotide polymorphisms were genotyped in the CFH (rs380390), LOC387715/ARMS2 (rs10490924), and HTRA1 (rs11200638) genes using optimized gene-expression assays. The critical fusion frequency (CFF) mediated by cones alone (long-, middle-, and short-wavelength sensitive cones, LMS) and by the combined activities of cones and rods (LMSR) were determined. The stimuli were generated using a four-primary photostimulator that provides independent control of the photoreceptor excitation under mesopic light levels. Visual function was further assessed using standard clinical tests, flicker perimetry, and microperimetry.

RESULTS

The mesopic CFF mediated by rods and cones (LMSR) was significantly reduced in gene-positive compared to gene-negative participants after correction for age (P = 0.03). Cone-mediated CFF (LMS) was not significantly different between gene-positive and -negative participants. There were no significant associations between flicker perimetry and microperimetry and genotype.

CONCLUSIONS

This is the first study to relate ARM risk genotypes with mesopic visual function in clinically normal persons. These preliminary results could become of clinical importance because mesopic vision may be used as a biomarker to document subclinical retinal changes in persons with risk genotypes and to determine whether those persons progress into manifest disease.