Lens Fitting Guide
Rigid gas permeable lenses
CIBA VISION supply a comprehensive range of standard and non-standard gas permeable lenses. The standard range includes the Polycon, K Design, KE Design, and continuous Curve spherical lenses, the Asphericon, Astrocon, Aquila and Persecon aspheric / elliptical geometries. Loan trial sets are available for more complex fits in the following designs: Soper, Woodward, Persecon E and SoftPerm keratoconus designs. In addition to the standard parameters, we also offer centre-distance bifocals, a full range of custom torics, together with practitioner specified lenses. The complete range is available in ten different materials – offering a variety of Dk’s and surface properties to meet patient’s clinical requirements. For details of loan sets and for our comprehensive lens design service please call the Professional Services Department on 01489 775533.
| Polycon II | Fluorocon 30 | Fluorocon 60 | Fluorocon 90 | Fluorocon 151 | |
| Oxygen Permeability† (Dk x 10-11 @ 35°C) |
12 | 35 | 65 | 95 | 151 |
| Shore D Hardness | 87 | 85 | 83 | 81 | 79 |
| Specific Gravity | 1.15 | 1.14 | 1.15 | 1.10 | 1.10 |
| Wetting Angle | 15 | 12.80 | 14.70 | 16 | 42 |
| Refractive Index | 1.473 | 1.470 | 1.473 | 1.450 | 1.471 |
| Handling Tint | Blue | Grey | Blue | Green | Blue |
| HDS | Aquila A | Persecon 92E | Persecon E | Persecon CE | |
| Oxygen Permeability† (Dk x 10-11 @ 35°C) |
58 | 143 | 92 | 8 | 54 |
| Shore D Hardness | 84 | 78 | 81 | 74 | 82 |
| Specific Gravity | 1.16 | 1.16 | 1.10 | 1.19 | 1.07 |
| Wetting Angle | 14.70 | 39 | 16 | 20 | 26 |
| Refractive Index | 1.449 | 1.431 | 1.452 | 1.476 | 1.1465 |
| Handling Tint | Blue | Blue | Blue | Clear or Grey | Blue |
† Modified Fatt
Fitting Procedure
• Full refraction and eye examination
• Keratometry
• Assessment of fit
A Good Fit
• Aligns with the flattest corneal meridian
• Moves freely giving a good tear flow beneath the lens
• Covers the pupil – slight vertical or lateral positioning is acceptable
• Is more comfortable after the tolerance trial
A Flat Fit
• Bears heavily on the central cornea
• Moves very freely
• Decentres markedly
• Can give unstable vision
• Can cause discomfort to the lids
A Steep Fit
• Shows central pooling surrounded by a ring of touch which
restricts tear flow and interferes with corneal metabolism
• Centres well
• Moves little with the blink
• Is uncomfortable on the eye
• Causes little lid sensation
A Tolerance Trial
• Of 30 minutes or more allows a more accurate reassessment of fit and comfort. “Good fit” criteria should still apply
Over-Refract
• To determine the best sphere power. If visual acuity is reduced, check for residual astigmatism
Care System
• Please refer to Lens Care section
Technical Assistance
• For fitting advice and details of our computerised empirical calculation service please provide the patients ‘K’ readings, spectacle prescription and Back Vertex Distance and we will be happy to supply the finished lens specifications
Ordering diagnostic/initial lenses call 0800 336655
• Specify lens type, BOZR, total diameter, back vertex power, cylinder power and axis
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