Jayanti Chaudhary, B. Optom, F. Optom

Optometrist, Dr Shroff’s Charity Eye Hospital, New Delhi

Visual Field Analyzer is one of the essential factors for assessing the functional changes in glaucoma assessment. Visual field is generally used for disease staging, monitoring the disease progression especially in glaucoma and correlation with the patient’s quality of life. ^(1-4)

The 24-2 SITA-Standard test pattern in Humphrey Field Analyzer (HFA) is widely used in standard clinical setting to detect the glaucomatous visual field defects. This system focuses on testing particular areas in Retinal Nerve Fiber Layer (RNFL) which are mostly affected in glaucoma.^(3,5,6) It is often assumed that glaucomatous visual field defects affect in the peripheral field, however, in clinical scenario, significant defects within central part of the visual field (with or without involving macula) were reported to be indicating of advanced glaucoma.^(7-10) If the visual field loss occurs centrally (towards fixation), it impacts patient’s functional vision to a greater extent.⁽¹¹⁾

In a busy clinic, it is time consuming process to perform two test grids, the 24-2 and 10-2 at the same clinical visit. The 24-2 test grid consists of 54 testing points which is relevant for detecting glaucomatous visual field defects, the “peripheral” whereas 10-2 consists of 68 testing points which have been proposed to map out central visual field defects.⁽¹²⁾ To overcome this hurdle, the 24-2C was commercially introduced on the Humphrey Field Analyzer in early 2019. 24-2 takes approximately 6-8 minutes, and 10-2 takes 8-10 minutes, whereas, 24-2C adds 30 seconds to the testing time for an additional 10 points centrally (Figure 2).^(13,14) The 24-2C combines the speed of SITA–Faster (the newest additional strategy of HFA 3, which takes about two-thirds of the time required by SITA Fast)^(12,15) with an additional 10 points incorporated into the 24-2 grid to increase sensitivity to central field defects.⁽¹⁴⁾

Figure 1: Testing time of different strategies, ranging in minutes (mean ± std.dev) (Source: Zeiss manual).

The additional points were described to have been chosen from common areas affected in glaucoma. The arrangement of these points is not in a symmetric way, so a typical ‘hemifield’ test which is known as GHT is not available for evaluating defects here.⁽¹³⁾

Figure 2: Arrangement of Central 10 New points (Source: Zeiss HVF3 manual).

In addition to a typical sensitivity, which provides information about central visual field defects and probability score, the overall test provides a mean deviation and pattern standard deviation.

Global results, i.e. mean deviation (MD), pattern standard deviation (PSD), and Glaucoma Hemi field Test (GHT), are used to identify presence of glaucomatous visual field defects and disease progression. It was reported that no significant difference found in these indices between 24-2 and 24-2C.⁽¹³⁾

Figure 3: Field layout of 24-2.  

Figure 4 : Field layout of 24-2C.

Figure 5: Field layout of 10-2.

CONCLUSION

As mentioned earlier, the 24-2C adds approximately 30 seconds to the testing time for an additional 10 points centrally⁽¹³⁾, however, there are no apparent differences between 24-2 and 24-2C in their ability to stage or identify cases of glaucomatous field loss as well as the presence of central field defects are often flagged. The 24-2 (Figure 3) test grids were similar to those of 24-2C (Figure 4) test grid but centrally, the 24-2C (Figure 4) grid showed more cluster of defects than the 24-2 (Figure 3) grid.^(13,14)

References

1)  Yeoun Sook Chun, Kyung Rim Sung, Chan Kee Park ,Hwang Ki Kim et. al; Vision-related quality of life according to location of visual field loss in patients with glaucoma. Acta Ophthalmol. 2019 Aug; 97(5):e772-e779.

2) Yamazaki Y, Sugisaki K, Araie M, Murata H et al ;Relationship between Vision-Related Quality of Life and Central 10 of the Binocular Integrated Visual Field in Advanced Glaucoma. Sci Rep. 2019 Oct 18;9(1):14990.

3) Nouri-Mahdavi; Selecting visual field tests and assessing visual field deterioration in glaucoma. K. Can J Ophthalmol. 2014 Dec; 49(6):497-505.

4) Tomairek RH, Aboud SA, Hassan M, Mohamed AH ; Studying the role of 10-2 visual field test in different stages of glaucoma.  Eur J Ophthalmol 2019; 30:706–713.

5) Heijl A, Asman P;Pitfalls of automated perimetry in glaucoma diagnosis.CurrOpin Ophthalmol. 1995 Apr;6(2):46-51.

6)  Wu Z, Medeiros FA, Weinreb RN, Zangwill LM; Performance of the 10-2 and 24-2 visual field tests for detecting central visual field abnormalities in glaucoma.  Am J Ophthalmol 2018; 196:10–17.

7) Blumberg DM, De Moraes CG, Prager AJ, Yu Q et al; Association Between Undetected 10-2 Visual Field Damage and Vision-Related Quality of Life in Patients With Glaucoma .JAMA Ophthalmol. 2017 Jul 1;135(7):742-747.

8) Sullivan-Mee M, Karin Tran MT, Pensyl D, et al; Prevalence, features, and severity of glaucomatous visual field loss measured with the 10-2 achromatic threshold visual field test.  Am J Ophthalmol 2016; 168:40–51

9) Traynis I, De Moraes CG, Raza AS, et al; Prevalence and nature of early glaucomatous defects in the central 10 degrees of the visual field. JAMA Ophthalmol 2014;132(3):291–297.

10) Hood DC, Nguyen M, Ehrlich AC, et al; A test of a model of glaucomatous damage of the macula with high-density perimetry: implications for the locations of visual field test points.   Transl Vis Sci Technol 2014;3(3):5.

11) Joon Mo Kim; Haksu Kyung; SeongHee Shim; Parham Azarbod et al; Location of intial visual field defects in glaucoma and their modes of deterioration. Investigative Ophthalmology & Visual Science December 2015, Vol.56, 7956-7962.

12) Zeiss.com/meditec/int/c/zeiss-hfa3.html

13) Jack Phu Michael Kalloniatis ;  Ability of 24-2C and 24-2 Grids to Identify Central Visual Field Defects and Structure-Function Concordance in Glaucoma and Suspects.Am J Ophthalmol. 2020 Nov;219:317-331.

14)Lavanya R, Riyazuddin M, Dasari S, Puttaiah NK, et al; A Comparison of the Visual Field Parameters of SITA Faster and SITA Standard Strategies in Glaucoma. J Glaucoma. 2020 Sep;29(9):783-788.

15) Anders Heijl, Vincent Michael Patella, Luke X Chong, Aiko Iwase ; A New SITA Perimetric Threshold Testing Algorithm: Construction and a multicenter clinical study. Am J Ophthalmol.2019 Feb; 198: 154-165.