Performance standards for toric soft contact lenses.
OBJECTIVE
To simplify the clinical assessment of toric soft contact lens (TSCL) on-eye behavior by establishing a set of standard clinical evaluation techniques. The likely performance range expected among the TSCL wearing population was determined for a series of lens designs and acceptable performance standards indicated for each variable.


METHODS
Four prism-ballast, two peri-ballast and one dynamic stabilization TSCL designs were each worn by groups of 20 subjects in a nondispensing study. After 20 min of lens wear, lenses were assessed, in right eyes only, for subjective comfort (100-point scale), lens mislocation (degrees deviation from vertical) and rotational recovery after deliberate 30 degrees mislocation (degrees/10 blinks). The percentage of lenses orienting within +/-10 degrees of target orientation (zero rotation) and the variability of orientation (standard deviation of mislocation) were also calculated for each lens group.


RESULTS
Based on partitioning of the data distributions for each variable, performance was designated as excellent, acceptable or poor. Corresponding performance cut-offs were determined at > or =90, 89 to 80, and <80 for subjective comfort, < or =+/-6 degrees , +/-7 degrees to 10 degrees , and >+/-10 degrees for mislocation, >10 degrees /10 blinks, 10 degrees to 6 degrees /10 blinks, and <6 degrees /10 blinks for rotational recovery. For groups of wearers the appropriate cut-offs were > or =90%, 89 to 70%, and <70% of lenses orienting within +/-10 degrees of target orientation and <+/-6 degrees , +/-6 degrees to 10 degrees , and >+/-10 degrees for variability of orientation.


CONCLUSIONS
Techniques suitable for the evaluation of TSCL clinical performance have been described and guidelines for the assessment of such lenses established. In the process, we have identified potential performance differences that may relate to variations in TSCL design.
Tan
Jacqueline
J
Institute for Eye Research, School of Optometry and Vision Science, The University of New South Wales, Sydney, New South Wales, Australia.
Papas
Eric
E
Carnt
Nicole
N
Jalbert
Isabelle
I
Skotnitsky
Cheryl
C
Shiobara
Maki
M
Lum
Edward
E
Holden
Brien
B
D000328:Adult; D003263:Contact Lenses, Hydrophilic / Q000592:standards*; D004867:Equipment Design; D005069:Evaluation Studies as Topic; D017408:Guidelines as Topic; D006801:Humans; D008875:Middle Aged