Rigid lens centration: Effects of lens design and material density

Two lens features of relevance to the control of rigid lens dynamics are material density and lens design. The effect of these two features on lens centration was investigated for two subject groups (four subjects with high riding lenses and four subjects with low riding lenses). Each subject was fit with 12 different lenses- six designs in each of two materials. The settled vertical lens position for a five blink cycle was assessed in every case. Overall, there was a statistically significant inter-subject effect of the measurements (p<0.001) and a significant difference in lens position between the two groups (p<0.001), For subjects with low riding lenses, lens material changes improved lens centration, but changes in lens thickness were relatively ineffective. An increase in lens diameter caused a lowering of the settled lens position for both groups. In general, all corrective strategies were less effective for high riding lenses then for low riding lenses