Comparison of 10-2 and 24-2C Test Grids for Identifying Central Visual Field Defects in Glaucoma and Suspect Patients
Phu J, Kalloniatis M1
Industry support: None
ABSTRACT SUMMARY
A single-center, prospective, cross-sectional study recruited 188 individuals who met the criteria for a diagnosis of either glaucoma (n = 131) or high-risk glaucoma suspect (n = 57). The patients underwent visual field testing with the 10-2 (Swedish interactive thresholding algorithm [SITA] fast) and 24-2C (SITA faster) grids on the Humphrey Field Analyzer (Carl Zeiss Meditec) in random order, followed by macular OCT imaging for ganglion cell analysis (GCA). The first aim of the study was to compare the reported conventional visual field indices between the two testing patterns. The second aim was to analyze the ability of each testing pattern to localize structural changes detected on a corresponding GCA map.
STUDY IN BRIEF
A single-center, prospective, cross-sectional study compared the ability of the 10-2 and newer 24-2C test grids to identify central visual field defects in glaucoma patients and glaucoma suspects. Both grids demonstrated proportionally similar amounts of central visual field loss, but the 10-2 seemed to be more useful for comprehensively characterizing the central field defect and predicting central visual function.
WHY IT MATTERS
The central visual field may be affected early in the course of certain glaucoma phenotypes,2,3 and the 24-2 test grid may not adequately describe central visual loss.4 Administering both a 24-2 and a 10-2 test grid is typically impractical in a busy clinical practice. The 24-2C test grid can serve as a catchall method for examining the central and peripheral fields.
When using the cluster criterion of at least two contiguous points of central visual field loss, the 10-2 grid demonstrated an increased tendency to identify more instances of cluster deficits, especially in the glaucoma cohort. The 10-2 test grid also identified a greater proportion of defective test locations in all patients compared to the 24-2C grid. The conventional visual field indices of mean deviation (MD), pattern standard deviation, and mean central sensitivity were similar between both grids in most cases, but the greater variability between the two grids in the global indices was more pronounced in patients with severe loss.
In the structure-function analysis where the 10-2 or 24-2C grid was superimposed on the GCA scan, the 10-2 grid demonstrated higher instances of concordance of structural and functional deficits. Given the thresholding algorithms of each grid, the 10-2, on average, took a longer time to administer than the 24-2C (201 vs 154 seconds).
DISCUSSION
Why is it important to test the central visual field during glaucoma evaluations?
Identifying central vision loss is vital not only for staging and management but also for appreciating the effect that loss can have on a patient’s quality of life and ability to perform daily activities.2 The 10-2 grid has a higher testing density in the central 20º, so it can better characterize central visual loss. This information allows clinicians to individualize management plans for a patient that may necessitate task-specific visual rehabilitation strategies.3
Can the 24-2C grid be used to detect central visual field loss? Can this grid replace the 10-2?
Phu and Kalloniatis found similar results with the 10-2 and 24-2C grids with regard to the average sensitivity in the central testing locations and the pattern. Specifically, the results were similar on the central mean sensitivity index. On average, both grids should therefore yield similar levels of visual function. It is important to note that the 24-2C has the 10 extra central locations derived from the 10-2 grid but with sparse test locations. When compared to the 10-2, the 24-2C did not meet the cluster criterion of at least two contiguous points. Lastly, the current study demonstrated that, overall, the proportions of central test locations showing a deficit were similar with the 10-2 and 24-2C grids.1 Based on these findings, the new 24-2C protocol cannot entirely replace the 10-2 protocol,4 but the former can be useful for detecting central visual field loss in glaucoma.
How can a busy clinical practice incorporate both testing strategies into glaucoma evaluations? Which test grid should be used during routine glaucoma evaluations?
Depending on the patient’s glaucoma phenotype, both central and peripheral vision tests may provide useful information such as characterizing complementary regions of testing.3 That said, simultaneously performing both grids in a busy clinical practice may be impractical, and the frequency of testing in a calendar year may be limited by reimbursement models.
Phu and Kalloniatis demonstrated that the 24-2C grid pattern can test the complementary regions and highlight central vision involvement similarly to the 10-2 grid pattern. The advantage afforded by the 24-2C grid compared to the 10-2 grid lies in the duration of the administered test1; a 24-2C protocol thus may be a great option for routine glaucoma management. The 10-2 grid may be better reserved for patients with advanced disease and those for whom macular OCT imaging suggests central involvement.
The Effect of Transitioning From SITA Standard to SITA Faster on Visual Field Performance
Pham AT, Ramulu PY, Boland MV, Yohannan J5
Industry support: M.V.B., personal fees from Carl Zeiss Meditec
ABSTRACT SUMMARY
A single-center, retrospective, longitudinal study analyzed 421 individuals with glaucoma or suspected glaucoma who underwent automated perimetry testing during routine clinical care over a 2-year period in the following sequence: SITA standard, SITA standard, SITA faster. The primary aim of the study was to investigate the effect of testing sequence on MD change between the first two examinations and the last two examinations. The secondary aim was to determine the effect of this testing sequence on other visual field parameters. The disease severity for each eye (N = 766 eyes) was determined by MD value: mild, better than -6 dB (n = 488); moderate, between -6 and -12 dB (n = 139); and severe, less than -12 dB (n = 139).
STUDY IN BRIEF
A single-center, retrospective, longitudinal study assessed the effect of transitioning from Swedish interactive thresholding algorithm (SITA) standard to SITA faster on the visual field performance of glaucomatous eyes. The algorithms’ performance was similar in eyes with mild disease. Eyes with moderate or severe glaucoma, however, generally performed better on SITA faster tests, which could conceal disease progression.
WHY IT MATTERS
To address testing bottlenecks in a clinical practice and current recommendations that visual field testing be frequent,7 a faster testing strategy for automated perimetry6 has been deployed in clinical practice. This study found that transitioning to the SITA faster test was associated with shorter test durations, a higher rate of false-positive errors, and improved visual field performance in eyes with moderate or advanced glaucoma. Transitioning to the SITA faster algorithm in patients with late-stage disease requires careful consideration because it may hinder clinical decision-making.
The change in MD was found to be statistically different between the standard-standard and standard-faster sequences. The former was associated with an average MD change of -0.30 dB, whereas the latter demonstrated an average positive MD change of +0.23 dB. The difference in MD change was found to be statistically higher in the standard-faster sequence for moderate (+0.99 dB) and severe (+1.54 dB) glaucoma, but there was no statistical difference in the mild or suspect glaucoma groups.
The average rate of false-positive errors was 2.00% higher with the SITA faster sequence, but the false-positive rate for advanced glaucoma was 2.08% lower than for mild glaucoma. The average test duration was 203.14 seconds shorter with the faster testing pattern compared to the standard examination.
DISCUSSION
What challenges can occur when transitioning from SITA standard to SITA faster testing?
Pham and colleagues demonstrated that changing strategies did not significantly affect MD values in eyes with mild disease. In eyes with moderate or advanced glaucoma, however, MD values improved when SITA faster testing was performed in longitudinal settings. This testing strategy may therefore conceal disease progression in patients with moderate to advanced glaucoma.
Is SITA faster testing reliable compared to SITA standard testing?
The study found higher rates of false-positive errors in patients undergoing SITA faster versus SITA standard testing. The higher rates can be attributed to the difference in starting stimulus intensity and the shorter time between unseen and new stimuli.6 Both create a more difficult testing situation that may incline patients to respond when uncertain. Because a high rate of false-positive errors can lead to an underestimation of sensitivity loss in glaucoma, the results should be used with caution. Pham and colleagues, however, found the rate of false-positive errors to be comparable between the two algorithms at later stages of glaucoma. The transition from SITA standard to SITA faster and increases in MD were determined to be independent of false-positive errors.5
How should clinicians implement the transition to SITA faster? Is it appropriate to continue with SITA standard testing in any scenario?
Logistical bottlenecks in perimetry testing can occur in a busy clinical practice, both from the patient’s and the clinician’s perspective. A shorter testing algorithm can reduce the burden of testing while adhering to the testing frequency currently recommended.7 The average duration of SITA standard, SITA fast, and SITA faster tests is approximately 7, 4, and 3 minutes, respectively.5 In previous studies, SITA faster was found to be nearly identical to SITA fast with regard to MD and visual field indices.6 Based on the results of the current study,5 a transition from SITA standard to SITA faster for patients with moderate or advanced glaucoma requires careful consideration because, as mentioned earlier, the SITA faster algorithm may obscure the detection of disease progression and hinder clinical decision-making.8
1. Phu J, Kalloniatis M. Comparison of 10-2 and 24-2C test grids for identifying central visual field defects in glaucoma and suspect patients. Ophthalmology. 2021;128(10):1405-1416.
2. Blumberg DM, De Moraes CG, Prager AJ, et al. Association between undetected 10-2 visual field damage and vision-related quality of life in patients with glaucoma. JAMA Ophthalmol. 2017;135(7):742-747.
3. Traynis I, De Moraes CG, Raza AS, Liebmann JM, Ritch R, Hood DC. Prevalence and nature of early glaucomatous defects in the central 10° of the visual field. JAMA Ophthalmol. 2014;132(3):291-297.
4. De Moraes CG, Hood DC, Thenappan A, et al. 24-2 visual fields miss central defects shown on 10-2 tests in glaucoma suspects, ocular hypertensives, and early glaucoma. Ophthalmology. 2017;124(10):1449-1456.
5. Pham AT, Ramulu PY, Boland MV, Yohannan J. The effect of transitioning from SITA standard to SITA faster on visual field performance. Ophthalmology. 2021;128(10):1417-1425.
6. Heijl A, Patella VM, Chong LX, et al. A new SITA perimetric threshold testing algorithm: construction and a multicenter clinical study. Am J Ophthalmol. 2019;198:154-165.
7. Nouri-Mahdavi K, Zarei R, Caprioli J. Influence of visual field testing frequency on detection of glaucoma progression with trend analyses. Arch Ophthalmol. 2011;129(12):1521-1527.
8. Phu J, Khuu SK, Agar A, Kalloniatis M. Clinical evaluation of Swedish interactive thresholding algorithm-faster compared with Swedish interactive thresholding algorithm-standard in normal subjects, glaucoma suspects, and patients with glaucoma. Am J Ophthalmol. 2019;208:251-264.
