easy way to fit soft contact lens

1. Soft contact lens fitting
Md. Nooruz Zaman
M.Optom, (FIACLE), (PhD)

2. Factors which affects lens fit
 Modulus of elasticity
 Manufacturing method
 Water content
 Keratometric readings
 Lid tonus
 Tear film

3. Fitting steps
 History
 Initial eye examination-SLE
 Refraction, 4:1
 Keratometry
 HVID
 Other tests like tear film, sensitivity,PAH etc
 Selection of trial lens

4. The parametrs of lens is
selected on following
 BC
 Power
 Diameter
 Types of lens

5. Steps for calculations
 K in mm
 Add 1mm to mean k
 Power-
1. transpose to minus cyl
2. Sph. equivalent
3. VDC for more than 4 D
 Diameter- HVID+2mm (13 to 14.5mm)

6. Evaluation of Fit
 Patients comfort response
- Fairly comfortable – probably good fit
- Uncomfortable - predicts loose
fit(excess movement)
- Very comfortable – May be steep or tight
(immobile)

7. Corneal coverage
Slit lamp, diffuse illumination,
- eye in primary position, lens should show
full corneal coverage about 1 to 2mm
beyond limbus
- Full coverage (1 -2mm) – Ideal
- Greater than 2 mm – lens too large
- Corneal exposure – lens too small

8. Lens centration
 Equally centered in all distance beyond
limbus in all directions.
 Centered in all position – ideal
 Decentered with corneal exposure in any
position of gaze- steep or loose, dia may
be small.

9. Movement
 Patient asked to look straight in primary
gaze and asked to blink normally.
 Movement is estimated in diffuse light and
moderate to high magnification with
blink.
 0.2 – 0.4 mm ---- ideal

10. Push up test
 Patients looks straight and examiner pushes
the lens up vertically through the pressure of
lid
 40-60% IDEAL
 Easy displacement- smooth recovery – ideal
fit
 Resistence to displacement – may not
recenter – tight fit
 Easy displacement- Erratic recovery – Loose fit

11. Lens Lag
 Patient asked to loo up and lens move
down slightly –Lag
 1 to 1.5 mm - Ideal

12. Edge Alignment
 Edge of the lens is observed with
reference to the conjunctiva.
 If the edge is sliding smoothly and aligning
with conjunctiva is the ideal.
 If indent on cornea- tight or steep
 If it stands off - loose

13. Other responses
 Vision before and After blink-
- If ideal vision will remain same and clear
- If vision clears with blink – steep
- If vision gets blur with blink- flat fit
 Keratometry and retinoscopy with the lens on
the eye can also be performed. Clarity of
mires is observed
 If clears with blink-steep
 If blurs- flat

14.  Alter the lens if ideal fit is not achieved
 Fitting can be changed on
- BC
- Dia
- Thickness
- Rule of thumb- 0.3mm change in the base
curve = 0.5 mm change in Diameter

15. Over refraction
 Refraction over trial lens
 Algebraically add power
 Note- aditional power needed should be
less than 4D
 If cyl required –fit toric

16. Final Order
 BC
 Power
 Diameter
 Water content
 Tint
 Material
 Manufacturer