Letter contrast sensitivity validation

Contrast sensitivity (CS) is an important tool for evaluating functional vision. The Ocular Technology Group-International Vision Suite computerised letter CS test can evaluate multiple spatial frequencies, assessing the entire CS function. This clinical study validated the letter and sinusoidal CS methods by determining their repeatability using multiple spatial frequency settings and different lighting conditions.

The single-arm, prospective study compared the repeatability of CS measurements at two separate visits using three methods: computerised letter CS, computerised sinusoidal CS (M&S Technologies) and printed sinusoidal CS (VectorVision). Measurements were performed under photopic (without glare) or mesopic (with or without glare) conditions. Repeatability was assessed in 20 participants by comparing the mean and 95% CI of the difference between the measurements.

Test variance was significantly lower for letter CS compared with the M&S or VectorVision instruments at most spatial frequencies. Letter CS measurements had a substantially lower precision-to-tolerance ratio compared with the M&S or VectorVision and required the smallest estimated sample size to achieve a precision-to-tolerance ratio of 0.25.

Overall, the computerised letter method for assessing CS function was highly repeatable and had significantly lower test variance when compared with either of the sinusoidal instruments.