M&S Smart System Contrast Sensitivity Measurements Compared With Standard Visual Function Measurements in Primary Open-Angle Glaucoma Patients

Abstract

Purpose: To evaluate the nature and extent of letter contrast sensitivity (CS) deficits in glaucoma patients using a commercially available computer-based system (M&S Smart System II) and to compare the letter CS measurements to standard clinical measures of visual function.

Methods: Ninety-four subjects with primary open-angle glaucoma participated. Each subject underwent visual acuity, letter CS, and standard automated perimetry testing (Humphrey SITA 24-2). All subjects had a best-corrected visual acuity (BCVA) of 0.3 log MAR (20/40 Snellen equivalent) or better and reliable standard automated perimetry (fixation losses, false positives, and false negatives <33%). CS functions were estimated from the letter CS and BCVA measurements. The area under the CS function (AUCSF), which is a combined index of CS and BCVA, was derived and analyzed.

Results: The mean (± SD) BCVA was 0.08±0.10 log MAR (∼20/25 Snellen equivalent), the mean CS was 1.38±0.17, and the mean Humphrey Visual Field mean deviation (HVF MD) was -7.22±8.10 dB. Letter CS and HVF MD correlated significantly (r=0.51, P<0.001). BCVA correlated significantly with letter CS (r=-0.22, P=0.03), but not with HVF MD (r=-0.12, P=0.26). A subset of the subject sample (∼20%) had moderate to no field loss (≤-6 dB MD) and minimal to no BCVA loss (≤0.3 log MAR), but had poor letter CS. AUCSF was correlated significantly with HVF MD (r=0.46, P<0.001).

Conclusions: The present study is the first to evaluate letter CS in glaucoma using the digital M&S Smart System II display. Letter CS correlated significantly with standard HVF MD measurements, suggesting that letter CS may provide a useful adjunct test of visual function for glaucoma patients. In addition, the significant correlation between HVF MD and the combined index of CS and BCVA (AUCSF) suggests that this measure may also be useful for quantifying visual dysfunction in glaucoma patients.

Figure 1

HVF MD as a function of log letter CS. Data are shown for subjects who have a HVF MD loss less than 6 dB (triangles) and for subjects who have a HVF MD loss greater than 6 dB (squares) in panel A. The lines represent linear regression fits to the data as described in the text. Panel B replots the data in A for subjects separated into four groups. The lines in B represent linear regression fits to the data with slopes constrained to zero, as described in the text. The gray region in both panels represents the normal range based on previous data.

Figure 2

Estimated CSFs are shown for subjects who have a HVF MD loss less than 6 dB (triangles) and for subjects who have a HVF MD loss greater than 6 dB (squares) in panel A. The CSFs were derived from a previous model, as described in the text. Panel B shows the CSFs for subjects divided into four groups based on their HVF MD values.

Figure 3

HVF MD as a function of AUCSF. Conventions are as in Fig. 1.