Scleral Lens Case Studies: Keratoconus

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Scleral Lens Case Studies: Keratoconus
Case Study A: Patient: LN
Female
Age:32
History: This 32 year old Caucasian female was diagnosed in 2010 with keratoconus in both eyes. The left eye
shows the keratoconus to be more advanced. She has tried numerous RGP lenses over the past few years with little
success. She wore soft lenses in 2010 but her vision was poor.
Topography
OD: OS:
Plan
Right Eye: SSF 13
RADIUS
8.23
8.43
8.70
12.80
14.40
SAG
Rx: -4.75/-1.25 X 180°
DIAMETER
8.60
12.00
13.80
14.80
15.60
4.1339mm
C.T.: 0.40
Left Eye: SSF 7
RADIUS
7.18
7.38
8.70
12.80
14.40
SAG
Rx: -12.50/-1.50 X 180°
DIAMETER
8.60
12.00
13.80
14.80
15.60
4.7173mm
C.T.: 0.40
Fitting regular 9.8 diameter hard lenses seemed to be very unstable especially on the LEFT eye so the decision was
made to go the scleral lens route.
The above lenses were fitted.
Result
Good clearance but with some bearing on the limbus (o.u). This bearing also had an effect on corneal function as the
patient presented limbal hyperaemia after 2 hours of wear.
The sagittal depths of the above lenses showed good corneal clearance but showed inadequate limbal clearance
under both lenses due to the landing zone coming in too flat over the limbus.
The Zeiss Visante OCT showed good clearance but the bearing of the lens on the limbal zone is clearly visible.
Making the 13.8 & 14.8mm diameter curves steeper and blending the 2 zones over this area would create less touch.
Another option is to increase the diameter of these two zones in order to move the clearance over the limbus.
In the two OCT images above, we can see the sharp transition area between the 13.8 & 14.8 diameter curves. This
could also influence a good fit and therefore the introduction of an aspheric landing zone was needed. We did the
above adjustments to the lenses manually but still the hyperaemia persisted.
Larger lenses were then fitted to both eyes with the following parameters:
Right Eye: SWH 11
RADIUS
8.40
7.6556
8.45
13.25 x 14.25
14.55
Rx: -4.25
DIAMETER
8.90
10.80
13.80
16.50
17.50
C.T.: 0.38
Left Eye: SWH 7 (mod)
RADIUS
7.30
7.212
8.40
13.25 x 14.25
14.55
Rx: -11.50/-1.50 X 168°
DIAMETER
8.90
11.10
13.80
16.50
17.50
C.T.: 0.38
The larger 17.5mm diameter lenses are an improvement to the previous lenses and sit well over the limbus with no
evidence of hyperaemia.
As seen in the 16.5 diameter zone we decided on a toric curve for better fit on the sclera. “Observation of most scleral
patients so far show more blanching in the horizontal area over the sclera than in the vertical and a toric curve makes
much more sense to insure a good aligned fit with the sclera in 360 ̊. Studies have shown that the sclera is flatter
nasally and the temporal sclera steeper than the inferior sclera.” – Van der Worp – 2009
The above OCT images show a much more acceptable landing zone and good clearance. The larger overall diameter
lenses are not giving any hyperaemia in the limbal area even after a few hours of wear.
Slit Lamp Observations
FIGURE1: Shows an impression ring after lens removal. It is of no
consequence as there is no scleral blanching when the lens is in situ. Limbal
staining is slightly visible horizontally. As explained before, to alleviate staining,
increase limbal clearance through steepening the landing zone in the 16.5
diameter and blending the transition between the 13.8 and 16.5 diameter zone.
Limbal pressure can also be alleviated by increasing the optic zone slightly.
FIGURE 2: Right scleral lens showing good clearance over
the centre of the cornea.
FIGURE 3: Left Scleral lens showing good clearance over
the centre of the left cornea with a thinning in the clearance
visible at the position of the cone.
FIGURE 4: Right scleral lens still showing a small amount of
clearance over the limbus. We need to aim for clearance of
about 100 microns over the limbus.
FIGURE 5: Left scleral lens showing clearance over the limbal area.
Observing the scleral lens in different gaze positions
FIGURE 6: Right scleral lens showing no blanching in down gaze.
FIGURE 7: Left scleral lens showing no blanching on down gaze.
FIGURE 8: Right scleral lens showing a small amount of blanching on
the landing zone. If the bigger veins are observed, there is no blanching.
This part of the lens needs to be made steeper.
FIGURE 9: Left scleral lens showing no blanching on left gaze.
The patient wears the lenses for up to 12 hours per day very comfortably.
Our patient is very happy with the comfort and presents with a very satisfactory V.A of the following:
Right: 6/7.5 +2
Left: 6/7.5 -2
Case Study B: Patient: KB
Female
Age:21
History. This patient is a black female of 21 years old. She presented with keratoconus at the age of 10 with hydrops,
leading to scaring on the left cornea. There was only light perception in her left eye and a corneal transplant was done
in 2004.The best vision with a spectacle correction is:
Right: 6/12
Left: 6/9
Topography
OD:
OS:
Examination
Conventional hard lenses did not stay on the left eye and were forced out on the blink. The corneal graft on the left
eye also posed a challenge to obtain a good RGP fit. A regular post-surgery RGP was an option for the left eye but
since patient comfort was of high priority, a scleral lens was fitted.
Plan
The first lenses fitted had the following parameters:
Right Eye: SSF 11
RADIUS
7.84
8.04
8.70
12.85
14.50
SAG
Rx: -0.25
DIAMETER
8.60
12.00
13.80
14.80
15.60
4.3125mm
C.T.: 0.40
Left Eye: SSF 6.5
RADIUS
7.10
7.30
8.70
12.85
14.50
SAG
Rx: -5.00
DIAMETER
8.60
12.00
13.80
14.80
15.60
4.7173mm
C.T.: 0.40
Result
Figures 1 and 2 (following page) both show good clearance. 200-300 microns is adequate clearance even though the
Visante OCT shows a bit less than 200 microns.
Vision was very good with these lenses:RIGHT: 6/7.5+1
LEFT: 6/7.5+3
FIGURE1
FIGURE 2
The patient complained of discomfort in the left eye after wearing the lenses for a while. On examination I found that
the inferior edge of the lens was pressing the bottom eyelid inward causing the discomfort. This was not apparent in
the right eye.
A decision was made to fit a larger lens in the left eye to overcome the discomfort.
A SWH 17.5mm diameter lens was fitted on the left eye with the following parameters:
Left Eye: SWH 4
RADIUS
7.30
6.6586
8.45
13.25
14.50
SAG @ 13.80
Rx: -4.75
DIAMETER
8.60
11.10
13.80
16.50
17.50
4.300mm
C.T.: 0.38
FIGURE 3
The Visante OCT shows better clearance over the central cornea in Figure 3 and the patient finds more comfort with
the bigger lens diameter. There is no longer bottom lid irritation as there is now less lid influence on the larger lens.
Slit Lamp Observations
Right Eye
Image 1: Showing good clearance over the cornea but with some
touch on the limbus superior nasally.
Image 2:Central corneal clearance can be seen using the thin slit
(parallel-piped) on your slit-lamp without a blue light. The clearance is about 200microns in the centre over the cornea and still
sufficient for optimal corneal health. It is easy to see how the
clearance increases towards the limbus.
Image 3: Now showing good clearance of the limbus.
Image 4: Still showing a decrease in clearance superior nasally.
Left Eye
Image 5: The borders of the corneal graft are clearly visible
without the lens.
Image 6: Good clearance over the centre of the cornea.
Image 7: Showing good clearance over most of the cornea
except for the superior limbus. This touch over the limbus could
be due to upper lid pressure on the lens and is only visible in the straight-ahead gaze.
Image 8: On downward gaze the pressure disappears and
therefore it is so important to examine the clearance in all
directions of gaze.
Image 9: Even in the upward gaze there is sufficient clearance over the limbus.
Image 10: The decrease in clearance over the superior limbus in
straight-ahead gaze is once again visible using the parallel-piped
setting.
The patient presented very good vision and she is very happy with the comfort:
R: 6/6
L: 6/6-2
As seen from the Visante OCT scans, the sag can be increased more to insure even more clearance over the cornea.
An extra pair of lenses were made for the patient where the sagittal depth was increased by 91.2 microns OD &
100microns OS. This was to insure that the lenses maintain a clearance over the cornea and the graft of the left eye
even after a few hours of wear.
Final Conclusion
Scleral lenses can be a very successful option for a variety of patients. These lenses could help post-corneal
graft patients, keratoconics, irregular corneas, post-traumatic corneas and even children with very high refractive
errors. Comfort is really one of the most spectacular benefits of scleral lenses and many keratoconus sufferers
would prefer these lenses if they had a choice after trying normal RGPs versus scleral lenses.
A study has also found that 69 per cent of patients who were referred for keratoplasty could be successfully fitted
with contact lenses without surgery (Smiddy et al 1988) and if your patient could choose which lens to do this
with, I can guarantee that the scleral lenses, manufactured by the Contact Lens Laboratory of South Africa, would
be the patient’s as well as the optometrist’s lens of choice.
OPTOMETRIST:
Lizelle Dorfling-Smith
B.Optom (RAU)
CAS (Boston) Advanced Contact Lenses
Email: [email protected]