Hi, my name’s Martin Conway. I head up professional services at Contamac
Limited here in the UK, and today I’d like to take you through a basic gas
permeable contact lens fit. Fitting GP lenses for the novice fitter can be
quite a daunting prospect, so I thought today I'd show you some
shortcuts - tips and tricks - that I’ve gathered over the past 35 years.
Selection of the first lens is normally dictated by the manufacturer, and they
normally refer you to K readings or in this case, we have quite a sophisticated
piece of software that will actually suggest the first lens that we should try.
And what I'd like to show you today - this particular piece of software is
suggesting that we start with an 8.10 base curve and I'll just show you that
we can't rely on software alone, we really have to look through the slit lamp
and look at the fluorescein pattern and that's what I'll take you through today.
This is the medmont image of the suggested first lens and if you look at
the top right-hand corner of the screen now you can see that the flattest K lies
along 180 and measures 8.08 millimeter and the steepest K lies
along 90 at 7.93.
That means that we're dealing with a very small amount
of "with the rule" astigmatism - probably the most difficult to fit with
a spherical lens. It's suggesting we should start with an 8.10 and let's
see now what happens when we put that lens on the eye and see how it compares
with this suggested picture.
So here's our 8.10 lens on the eye and we can immediately see that this is nothing
like the suggested image the lens is clearly loose, we have an excess of clearance
top and bottom and with the blink the lens wants to rotate around
the axis rather than across the centre. Clearly, this lens isn't going to be
comfortable and we'll need to tighten it.
So here we have our 8.00 base curve lens on the eye and immediately we can see an
improvement in the picture. Less clearance top and bottom and the lens is
centring better, however, it still prefers to rotate around the apex of the
cornea rather than across it as we can see at this section here. So better but
still not as we'd like so we'll steepen it a fraction. This time we'll be
going to a 7.90.
And here is the steepest lens of all that we've used so far - 7.90
base curve and immediate that we can see that movement is better
moving across the apex of the cornea however, there's a hint of fluorescein
underneath the central part of the lens. Also the edge clearance along the
horizontal is not ideal but this lens is slightly on the tight side so we'll
probably this time have to have a lens made somewhere between the 7.90 and the
8.00 of the fitting set so our next lens will be ordered as a 7.95.
So let's look at this 7.95 on the eye.
Immediately the picture looks better. You've got a nice band of clearance
around the edge of the lens.
The lens is moving across the apex nice and slowly with the blink and at last I
think we can safely say that this lens is going to be more comfortable than the
others and it's going to centre better. So this will be our final lens this 7.95
Well I hope these few clips have been useful and they certainly taught us not
to rely solely on software. Knowledge of fluorescein patterns and more
importantly, in my case, I think, movement of the lens of key components of a successful fit.
When it comes to putting lenses in the patient most of the textbooks
will tell us to actually put the lens directly on to centre, but this
can be quite intimidating for a patient, especially a new patient, and so what I'd
like to share with you now is another technique of actually putting the lenses
in from the whites of the eye.
OK, lens is nicely wetted so if you
like to look down for me Sophie I'm going to lift the lid up, you keep
looking down I'm going to place the lens deliberately at 12 o'clock and if
you now look at my hand I'm going to hold the lens in place with the lid. If you
look up and onto the lens and then I look down and I've retained the upper
lid so the patient still cannot feel the lens. I'll gently let go of the lid and
if you have a slow blink you'll feel the edge of the lens. If it starts to
irritate look down into your lap until it becomes more comfortable. Much more
pleasant experience for the patient, and for the practitioner you don't have to
chase lost lenses around the eye.
Let's look at some tips for when the patient comes to put the lenses in.
So what I normally like to do, rather
than have the patient try to put the lens on to the center of the cornea and
fail and end up chasing the lens around the eye. What I like to do is get the
patient to put them on at the six o'clock position and then maneuver them
into position under control using the lid.
Here the lens is put in below the cornea
and using the sharp edge of the lid we gently push the lens
up into place. The lens is nicely into position and under control at all time.
We should never let the patient leave the practice without being shown how to
retrieve a lost lens should the lens become dislodged during wear or upon
insertion. So what we'll show now is the lens being deliberately put in
off-center in the upper fornix and the patient is then instructed in how to retrieve it
and replace it.
So here you see a lens being
deliberately placed into the upper fornix,
she is then instructed on how to move the lens around through the lid into the
lower fornix, and then pushed back into place using the lower lid as before
Thank you very much for watching. I hope you found these few tips useful. If you
have any suggestions or comments please feel free to contact us and if you have
any ideas for any future videos then please also get in touch