Impact of soft contact lens power on lens fit

Purpose To determine if a wider range of soft contact lens (SCL) can be more efficiently applied for fitting. This study evaluates whether altering spherical power by up to ±2.00 diopters (DS) within a single material and design changes on-eye fitting characteristics. Methods Prospective, randomised, cross-over, Open-label study was conducted. Each participant received either spherical Exact-Rx (current prescription) or Test lenses lens (±2.00DS to Exact-Rx; avoiding sign reversal) or toric Exact-Rx/Test lenses according to their refractive needs. After ≥15 min settling, centration (x/y decentration), corneal coverage, blink-induced movement, up-gaze and horizontal lag, push-up test, best-corrected distance visual acuity (BCVA, logMAR), and comfort, 1–10 scale and Visual Analogue Scale (VAS), were measured. Forced-choice lens preference was recorded. Right-eye data were analysed (paired t -tests or Wilcoxon signed-rank tests; α =0.05). Results A total of 30 adults (18–60 years, 31 ± 10 years, 50% female, OSDI 20.85 ± 14.80) were fitted with single vision SCL on two separate visits; Exact-RX and Test lenses respectively. Fit metrics in-invariant between Exact-Rx and Test lenses. Both lens types showed 360° corneal coverage in primary gaze with near-zero mean decentration (0.01 mm and 0.02 mm horizontally and vertically respectively); blink movement showed no difference (mean 0.37 ± 0.12 mm; p = 1.00). Horizontal lag did not differ (mean difference in percent 0.67 ± 2.54%; p = 0.157; mean difference in mm 0.00 ± 0.32 mm; p = 0.573), push-up test scores were similar (Exact-Rx −0.37 ± 0.49 vs Test −0.33 ± 0.48; p = 0.317). BCVA was comparable (−0.13 ± 0.08 vs −0.14 ± 0.07; p = 1.00). Comfort and forced choice favoured Exact-Rx on both scales ( p ≤ 0.005). Conclusions For somofilcon-A daily-disposable silicone hydrogel lenses, with a fixed base curve and diameter, changing spherical power by up to ±2.00DS shows no statistically significant difference in SCL fitting characteristics. Eye Care Professionals (ECPs) may optimise fit using available diagnostic powers from the same lens family and subsequently finalise the sphere power without re-fitting.