University of Missouri-St. Louis
School of Optometry
Laboratory Program Optometry 553
Contact Lenses I
Fitting Rigid Corneal Contact Lenses
During this session, interns should familiarize themselves with the techniques of hygiene and care, insertion, removal and recentering of lenses. A videotape showing patients fit with different base curves and corresponding fluorescein patterns will be viewed. Interns will attempt to achieve a successful fit on their partners. If time permits, they should fit their partners with lenses of different base curves to determine what effect the lens base curve has on the physical fit and ocular refraction.
Materials
Diagnostic contact lens set and accessories – cleaning, soaking and wetting solutions, irrigating solution, fluorescein strips, Burton Lamps and Biomicroscope.
Procedures
Base Curve Selection
Corneal Cylinder Fit
0.00-0.50D 0.50D-0.75D flatter than low K
0.75-1.00D 0.25D-0.50D flatter than low K
1.25D-1.50D "K" to 0.25D flatter than low K
1.75-2.00D 0.25D steeper than low K
2.25-2.50D 0.50D steeper than low K
2.75-3.00D 0.50D-0.75D steeper than low K
Lens Design
Tetracurve Design Tricurve Design
SCR/W = BCR + 0.8mm/.2mm-.3mm SCR/W = BCR + 1mm/.3mm
ICR/W = SCR + 1.0mm/.2mm PCR/W = SCR + 2mm/.3mm
PCR/W = ICR + 1.4mm/.2mm
Place lenses on both eyes and allow 15 minutes for tearing to subside before evaluating the fit.
Burton Lamp Evaluation
Is the overall pattern toric in shape? If so, is it with the rule, against the rule or oblique astigmatism? Indicate by drawing.
Slit Lamp Evaluation
Over-Refraction
Determine by retinoscopy, the ametropia uncorrected by the contact lens in situ. Record the sphere, cylinder and axis indicated in the phoropter. Remove the cylinder and subjectively determine the best sphere.
All data should be entered on the evaluation sheet provided.
Each student must demonstrate proficiency in handling, inserting, removing and centering of lenses before proceeding to designing and ordering lenses for his or her partner. In addition, complete the predicted over-refraction and Rx sections of the exercise to turn in with the completed fit and order form one week after the last fitting lab. *This order will not actually be ordered for y our partner.