Results of the Pinhole Test Correlate with Hybrid Contact Lens Visual Acuity in Patients with Visual Impairment due to Corneal Diseases

Abstract

Introduction. Trial rigid lens fitting is considered the best approach to determine whether the correction of residual defocus and irregular astigmatism might improve the visual acuity in patients with corneal disorders including keratoconus. This study aimed to analyze the correlation between hybrid lenses and pinhole visual acuity (VA). Methods. Patients undergoing hybrid contact lens fitting at the Hygeia Clinic, Poland, were included. The VA of each patient was assessed as decimal Snellen fractions under the following conditions: (i) uncorrected VA, (ii) VA with spherocylindrical correction (i.e., corrected distance VA), (iii) VA with a single 1.2 mm pinhole occluder, and (iv) VA with the best-fitted hybrid contact lens. Pearson’s correlation coefficient r was used to assess correlations among variables. Results. This study involved 29 eyes of 19 patients, mainly with advanced keratoconus. The uncorrected VA was 0.11 ± 0.10. The pinhole test provided significantly improved VA over corrected distance VA (0.51 ± 0.29 vs. 0.31 ± 0.20, respectively; p < 0.0001 ). Similarly, the fitted hybrid contact lenses provided improved VA over corrected distance VA (0.66 ± 0.26 vs. 0.31 ± 0.20, respectively; p < 0.0001 ). The pinhole VA was strongly correlated with the hybrid contact lens VA (r = 0.8135; 95% CI: 0.61–0.92; p < 0.0001 ). The improvement in the pinhole test over corrected distance VA was moderately correlated with the improvement with the fitted lens over corrected distance VA (r = 0.6269; 95% confidence interval (CI): 0.32–0.80; p = 0.0005 ). Conclusions. A significant improvement in VA with the pinhole test is a simple predictor of general improvement with hybrid contact lenses. The pinhole test should be used in patients with corneal diseases such as keratoconus to determine whether optical aberrations associated with the disease cause their visual impairment.

Applications of the pinhole effect in clinical vision science

“…59 In another study, the pinhole test was considered as a simple predictor of improvement with hybrid contact lenses (rigid center surrounded by a soft lens skirt). 27 The improvement in VA with the pinhole test was correlated positively with VA with a hybrid contact lens in patients with keratoconus and other corneal diseases and was better than with spherocylindrical correction. 27 Finally, the pinhole test may be used to identify a poor refraction, for example, if the spectacle-corrected VA is 6/7.5 and the pinhole improves this to 6/6, perhaps astigmatism may have been missed.…”

“…58 The pinhole test has also been shown useful in estimating the potential improvement over spherocylindrical correction with hybrid contact lenses in keratoconus and other corneal diseases. 27 Although the pinhole test is used often in clinical practice, it has not been described extensively. 59,60 Kumar et al found that the improvement in the pinhole test is correlated with the magnitude of spherical equivalent refraction (Spearman r = 0.68, P < .001) and concluded that the pinhole occlusion is a valid gauge of refractive error in Rapid Assessment of Avoidable Blindness surveys.…”

“…58 The pinhole test has also been shown useful in estimating the potential improvement over spherocylindrical correction with hybrid contact lenses in keratoconus and other corneal diseases. 27…”