spectacle blur after removing RGP lenses

[dineshk]

hi,

i wear rosek lenses and also switch to glasses for few days
rosek lenses provide be good vision & r comfortable for 6 hrs.
but after removing lenses my vision gets blurred for at least 2 days.

searched for reasons for this and found, my lens fitting could be tight
or should try soft lenses.

can anyone suggest me contact lenses to reduce spectacle blur after removing them.

[GrandPaClanger]

Hi Dinesh
Unfortunately it is impossible to answer your question on a forum. All I would say is that 6 hours is not a particularly long wear time so there could well be something wrong with the fit. I notice from your previous post that you have had CXL as well.
Go get the lenses checked out by your fitter. Better save than sorry.

Ian.

[GarethB]

My hospital when I was on RGP lenses always said RGP's should only be worn for a maximum of 8 hours. I did get to the point that I could only wear these types of lenses for one hour despite the lens fit being considered very good, so it isn't a sinmlpe of case of saying the lens fit needs changing.

The reason the vison is blurred afterwards is partly the brain having to readjst to the blurs again, but any lens type puts a small amount of weight on the cornea, simply because there is no such thing as a weightless lens. Plus optopetrists when fitting RGP lenses strive to get what they call a three point touch on the cornea which for KC is always a compromise, so even an ideal fit can to some extent push the cornea flatter or squeeze it slightly. Then there are the old school optometrisist that still insist on tight RGP lenses that push the cornea flatter.

When I changed to soft lenses four years agao, my corneas went through a period of demoulding, my right cornea went steeper while my left went flatter, just beacuse of the optimum lens fit that could be obtained.

Because soft lenses fit differently, this peice on Contact Lenses for Keratoconus is completly wrong!

They are designed to be thicker than regular soft lenses so they retain a rigid shape to some extent. For this reason they compress the central cornea and partially trap a tear pool, as with rigid corneal lenses. In effect, they are rigid lenses made from hydrogel materials, and they do appear to be giving a reasonable visual result with some types of keratoconus. One of the problems is that an end point in the fitting process may not be easily or quickly reached. Another is that hydrogel lenses require more attention to cleaning and storage procedures than rigid lenses. There is no reason why their use should not be investigated, but they are not replacing rigid lenses as the mainstream contact lens option for keratoconus.

There is NO COMPRESSION of the central cornea (KC Committee, can you please up date this as has been requested by myself a couple of years ago?)

The outer edge of the lens drapes over the outer margins of the cornea and is about as thin as a regular soft lens, but the central area is thicker and the ring you see on these lenses is the transition from lens skirt to optical zone. Lens fitting when I have it checked at my hospital takes no longer than an RGP fitting and lens care is easier and cheaper than the RGP lenses, My vision with soft lenses is far better than RGP lenses and I wear them all my waking hours so nolonger bother with glasses, infact I have had no need for them in the past four years I have been on soft lenses.

There are no guarentees soft lenses will work for you and there are other lens options. The only way you will know is by trying different lenses because as many of us with KC have found, there are quite a few exceptions to what the perceived rules are!

[Lynn White]

Hi Everyone...

This is an intersting dicussion becasue actually, spectacle blur from GP lenses can affect anyone wearing them, even those with normal corneas. In other words, its not just something that just affects people with KC. Older optometrists will remember this was part of our daily discussions with patients wearing these lesnes. Its mostly fogrgotten about nowadays as most of the normal population wear soft lenses (around 95%). In keratoconus, its also slightly overlooked in keratoconus, because most people with KC have such poor vision with spectacles they don't even bother with them.

So what is the issue?

RGP lenses are rigid - that is part of their definition. Most RGPs do not fit exactly in alignment with the corneal shape and the rigidity does exert some pressure on the cornea, causing a moulding efect. The more out of alignment with the shape of the eye, the more moulding effect lenses have - and, of course, this property is exploited in the science of Ortho-Keratology which relies on the fitting of progressively flatter lenses onto the cornea to change the shape so that peopel can see without lenses altogether. This is not a permanent effect - in Ortho-K, lenses have to worn a few times a week to keep the cornea reshaped.

This is a well researched effect and in fact, if you have normal eyes and are going fopr refractive surgery, RGP lenses have to left out for up to 2 months, or until the refraction has stabilised, before the surgery can be done. If you want to look at research paper, look at the one written by Tsai et al in 2004.

People with KC have even more issues, though, because the corena is up to 60% softer than normal, so is reshaped more easily. This does not necessarily mean the fit is wrong.

DINESH
The main demoulding chnages take place in the first few days, which is why it takes a couple of days for your vision to clear up.

Quick and easy solution: Get your eyes tested IMMEDIATELY after removing your RGP lenses. This will give you spectacles that you can see through straight after taking out your lenses. If you want to leave your lenses out for a few days, then your present glasses will take over after 2 days.

SOFT LENSES
Soft lenses for keratoconus have come a long way on the last few years. Older designs did indeed try to match the corneal shape and this could cause moulding. However, modern designs are much thinner and flexible and tend to be much more like normal soft lenses. Lenses are also now manufactured in silicon hydrogel as well as hydrogel and many many patients with KC world wide now wear these lenses. I have patients at all stages of keratoconus in soft lenses.

However, the interesting thing about the statement "One of the problems is that an end point in the fitting process may not be easily or quickly reached" is not to do with soft lenses per se but to the fact that patients are usually swapping from rigid lenses TO soft lenses and the whole aspect of spectacle blur/demoulding means the cornea can take several weeks or even months (depending on how many years you have been in RGPs) to settle down and stabilise.

My advice is always, start with soft lesnes and work your way up to more comlpex rigid lenses simply becasue it is much easier to go from soft to RGP than the other way around because of spectacle blur.

Lynn

[dineshk]

thanks lynn
your reply has given me some hope.
will consult my dr soon