How should initial fit inform soft contact lens prescribing

- A double-masked randomised trial of contact lenses fit over time was conducted.
- Silicone hydrogel and HEMA contact lens fit was evaluated at 5, 10, 20 min and 8 h.
- Soft lens initial fit 10-20 min after lens insertion is predictive of 8 h wear.
- Lenses with poor movement on blink/push-up after ≥10 min after insertion should be rejected.

PurposeTo investigate how initial HEMA and silicone-hydrogel (SiHy) contact lens fit on insertion, which informs prescribing decisions, reflect end of day fit.MethodsThirty participants (aged 22.9 ± 4.9 years) were fitted contralaterally with HEMA and SiHy contact lenses. Corneal topography and tear break-up time were assessed pre-lens wear. Centration, lag, post-blink movement during up-gaze and push-up recovery speed were recorded after 5,10,20 min and 8 h of contact lens wear by a digital slit-lamp biomicroscope camera, along with reported comfort. Lens fit metrics were analysed using bespoke software.ResultsComfort and centration were similar with the HEMA and SiHy lenses (p > 0.05), but comfort decreased with time (p < 0.01) whereas centration remained stable (F = 0.036, p = 0.991). Movement-on-blink and lag were greater with the HEMA than the SiHy lens (p < 0.01), but movement-on-blink decreased with time after insertion (F = 22.423, p < 0.001) whereas lag remained stable (F = 1.967, p = 0.129). Push-up recovery speed was similar with the HEMA and the SiHy lens 5-20 min after insertion (p > 0.05), but was slower with SiHy after 8 h wear (p = 0.016). Lens movement on blink and push-up recovery speed was predictive of the movement after 8 h of wear after 10-20 min SiHy wear, but after 5 to 20 min of HEMA lens wear.ConclusionsA HEMA or SiHy contact lens with poor movement on blink/push-up after at least 10 min after insertion should be rejected.