| SCL Design Factors | Geometric Center Thickness
Lens Diameter
BOZR
Back Surface Design
FOZR
Front Surface Design
Radial Edge Thickness
Edge Design
Material Physical/Mechanical Properties
Material Physiological Properties
Peripheral Junctional Thicknesses if transitions exist. |
| T or F: Material properties are insignificant in soft lens design | false |
| Center Thickness Considerations | Dk/t
Pervaporation prevention
Fitting considerations
Little or no movement |
| Design Considerations Minus Lens Series | Select a material
Practical FOZD
Center thickness for lenses of about -3.00D and greater
Lenses <-3.00D often made thicker and/or with a larger FOZD to improve handling
Lenses >-5.00D may have FOZD decreased to reduce mid-peripheral thickness |
| Design Considerations Plus Lens Series | First junction thickness
Select FOZD. Center thickness reduction by FOZD reduction is limited by vision issues
No degrees of freedom remain. |
| Water Content | Low H2o - 20 to 40%
Med H2o - 41 to 60%
Hi >60% |
| T or F: Corneal respiration is best served by a thick high-water lens. | false |
| It is also called as corneal dehydration | Pervaporation |
| If lens is too thin, corneal dehydration may result to | Due to bulk flow of water through lens and instability of water flow at a surface
Subject to individual variation
Worse with higher water content
Results in corneal dehydration from water loss to air via lens |
| Corneal dehydration produces _____________ which is also known as pervaporation staining | Epithelial Desiccation Staining |
| T or F: High water content lenses loses more water than low water lenses (% of total) on eye. | true |
| SCL Design other Considerations | Centration - vision comfort mechanical
Movement - debris clearance, comfort |
| T or F: For extended wear CLs, cornea’s minimum requirements must be met. | true |
| T or F: In DW CLs, much bigger requirements must be met | false |
| T or F: EW requirements always > DW | true |
