RGP fitting guide

Parameters
Fitting advice
Multifocal
Fluorescein Pattern

First contact lens choice

Orbiflex / Boriflex

  • Total diameter: = corneal diameter – 2.00 mm
  • Base curve:
    • SA: r0 = Kflat (rcfl)
    • S2A: rO = Kflat (rcfl)
    •  S3S:
      • ( rcfl – rcst) ≤ 0.30 mm -> rO = rcfl – 0.05
      • (rcfl – rcst) ≤ 0.40 mm -> rO = rcfl – 0.10
      • (rcfl – rcst) ≤ 0.50 mm -> rO = rcfl – 0.15
  • Flattening:
    • SA:  eccentricity (En) = eccentricity of the cornea at 30° rounded up to the next 1/10
    • S2A:
      • 1st zone: eccentricity (En) = eccentricity of the cornea at 30° rounded up to the next 1/10
      • 2nd zone: begin with (−) Standard
    • S3S: begin with (−) Standard

Toriflex

  • Total diameter: = standard 9.50 mm
  • Bitoric Geometry (BT): 
    • If astigmatism with the rule (WTR) flat K @ 0° ± 30°
      • r0fl = rcfl – 0.05 / r0st = rcst + 0.05
      • F’afl = Sph − 0.25 dpt
      • F’ast = Sph + (-Cyl) + 0.25 dpt
    • If astigmatism against the rule (ATR) flat K @ 90° ± 30°
      • r0fl = rcfl + 0.05 / r0st = rcst – 0.05
      • F’afl = Sph+ 0.25 dpt
      • F’ast = Sph + (-Cyl) – 0.25 dpt
    • If astigmatism oblique flat K @ 135° ± 15°/ 45° ± 15°
      • r0fl = rcfl / r0st = rcst
      • F’afl = Sph
      • F’ast = Sph + (-Cyl)
  • Fronttoric prismatic (TP):
    • r0 = rcfl – 0.05
    • F’v: SphCL = Sph − 0.25 dpt / CylCL = (-Cyl) + ((rcfl-rcst)*5) / A°CL = A° glasses

Progress of the adaptation

Insert trial lens for a minimum duration of 30 minutes. Ask patient to focus to the floor to minimise the foreign body sensation.

  1. Evaluation of the subjective comfort.
  2. Over-refraction
  3. Slit lamp examination:
  • Dynamic evaluation with diffuse illumination: – Eye in primary gaze and blinking normally. – Movement (speed) and position after blink and during eye movements:
    • Vertical movement
    • Horizontal movement
    • Centration
    • A good fitting lens will be evenly centred on the cornea (±0.5 mm)
    • The movement should be pronounced but not too big (1-2 mm)
  • Static evaluation with fluoroscopy:

Evaluation when patient is looking straight ahead and the lens is centred on the cornea without impact of the eyelids on the lens: Evaluation of the tear film thickness under the lens Tearfilm< 10μm = no florescein is visible

a) central optic zone with alignment fluorescein pattern

b) inter-peripheral zone with small amount of fluorescein

c) peripheral zone with a band of increased fluorescein how will be needed for a good tear film exchange

fluorescein pattern zones

Fitting guide for Toriflex:

The optimal fluorescein pattern shows a small fluor lake in the centre and a larger fluor ring in the periphery (env. 0.75 mm).

Vertical movement should be around 1 mm. In case of too much movement, decrease both central back curves (r0fl and r0st) with -0.10 mm. In case of low riders increase both central back curves (r0fl and r0st) with +0.10 mm or in case the upper lid is pushing the lens down, increase the total diameter ØT.

In case of high riders, decrease total diameter ØT

For Toriflex TP only: In case of instable stabilisation and/or high riders, increase the prism to 2.0 cm/m. Attention: the stabilisation prism induce an optical prism. This should be adjusted on both eyes.

Fitting guide for multifocal

Determine if the vision is alternate (change of optic zones by translation) or simultaneous (change of optic zones by visual cortex selection)

  • Alternate vision: reading zone in periphery (most of the cases)
  • Simultaneous vision: reading zone in centre


RequirementsBf BifocalSp Simple progressive
Addition < 1.75 dpt
Addition ≥ 1.75 dpt
Priority in distance vision
Priority in near visiondominant eyenon dominant eye
Good contrast

  • Distance vision depends on centering, near vision on the movement (translation).
  • For a good translation a movement from 1 to 2 mm is needed. It is affected by rO and ØT.
  • The fluoroscopy must show good optic zone alignment.


Bf centre nearBf centre distanceSp centre nearSp centre distance
Dominant eye2.253.752.504.00
Non dominant eye2.753.253.003.50
Undefined2.503.502.753.75

Fluorescein pattern to evaluate the fitting


Examination

Fluor image

Alignment / Good Fit

  • Central position – lens periphery is not extend beyond limbal area
  • Smooth movement – lid lifts lens with blink, lens then falls slowly
  • Good vision
  • Central and mid-peripheral alignment
  • Good edge clearance (approx 0.50mm wide)

good_fit_rgp

Loose / Flat Fit

  • Excessive and rapid movement upon blink
  • Arcuate dropping between blinks
  • Central touch can be observed
  • Excessive edge clearance
  • May produce a positive over refraction
  • Lens is unstable and decentres
  • If lens drops may show inferior arcuate pooling
  • Order steeper base curve

flat_fit_rgp

Tight / Steep Fit

  • Central position
  • Little movement with blink
  • Central pooling
  • Mid-peripheral touch
  • Thin band of edge clearance
  • May produce a negative over refraction
  • Order flatter base curve

steep_fit_rgp