Silicon hydrogel lenses

[Dave_W]

Hi

Seems like a long 18 months since I last (and first!) posted, what with having had Intacs surgery and all, but I was hoping I could get some advice on something (relatively) unrelated.

I've been having real problems with blepharitis this year (and getting very sore, red eyes most of the time), and was wondering if a move to silicon hydrogel lenses might help? I currently wear high water content soft lenses and I don't think they're helping matters much, as it feels like they suck what water there is out of my eye! Add in Sahara desert style air conditioning in work and it makes life a bit uncomfortable at the moment.

Has anyone had any practical experience of SHG lenses or got a view on them? My hospital optometrist didn't seem too keen to look at them as an option and doesn't do sclerals either, which seem to have worked wonders for many people on the forum.

Many thanks in advance for any replies.

Dave

[jayuk]

Dave

I know this may sound strange, but have you tried using a lubricant drops in the eye before or when there in your eye?....

J

[GarethB]

Dave,

In addition to what Jayuk mentions, soft lenses have a lower oxygen permeability than RGP lenses.

I am lead to beleive silicone hydrogel is the material used to make soft lenses and a thicker version of this is used in making the Kerasoft lens which has an even lower oxygen permeability because of its thickness.

In the first instance I would go wuith Jayuks suggestion. I use Systane which is recomened to be used by first removing your lenses. Once the drops are in, you can puit the lenses straight back in again. These drops form a thin gel film over the cornea so helping 'lock' moisture into the cornea and reducing the effect of the soft lens drawing the water out of your cornea.

Hope this helps.

Regards

Gareth

[Dave_W]

Thanks for the replies guys. I used to use wetting drops (Refresh) and was thinking about buying shares in the company, given the amount I used to spend on their products, before I had all my tear ducts plugged a couple of years ago. I also bought some Systane in the last couple of days, after reading Gareth's recommendations, but obviously early days yet.

I found that the Refresh drops provided temporary relief at best, as the humidity at work is under 25% (I tested it!), which is significantly less than H&S guidelines which suggest 40% as a minimum. I know several people at work, with normal tear production, who don't wear contacts because their eyes feel dry as a result. The only suggestion I got from our H&S people was to put cups of water and plants round my desk, but I found it hard to believe that would make any difference in a huge open plan office.

It was at this point that I decided to have all my tear ducts plugged, which resulted in tears running down my cheeks most of the time - a pound for every time someone asked me what I was upset about! - but at least my eyes were moist and stopped them getting sore. It also meant I didn't need to use wetting drops either.

However, the irritation has got gradually worse over the last three or four months, to the extent that I daren't go into a pub or anywhere where there is smoke in the atmosphere or even air conditioning like cinemas. It feels different to 'just' dry eyes, more like my eyes reacting to having the lenses in and I wonder if all the various ointments I've been prescribed over the last few months have resulted in the preservatives getting into the lenses and are now causing more irritation. I've asked for some new soft lenses, just to be on the safe side, which I should get this week.

Clearly it is probably just the blepharitis flare ups that have caused the problem, and I certainly have less tears streaming down my cheeks at the moment, which have led to the conjunctiva getting inflamed. If this is the case, then it's hopefully just a question of time and rigid adherence to the eyelid cleaning regime, healthy living, etc.

But, and this is the reason for the original post, the other thing that might help is improving the amount of oxygen getting to my eyes. It's something I've been thinking about for a while, as I've had optometrists express concern about blood vessels growing into my corneas in times past. However, I can't tolerate a lens with any rigidity - 'tight fitting eyelids' apparently! - so have been stuck with soft lenses. I've had SHG lenses suggested to me on the grounds of increased permeability, in comparison to soft lenses at least, hence my interest.

I probably should explain that I have Pellucid Marginal Dystrophy, so my cone is off centre and I'm fortunate that the distortion across my line of sight is fairly minimal, in my right eye at least and the left is much improved since the Intacs were put in, hence my vision is excellent with soft lenses (if you discount the 'ghosting' and flares from lights!).

Reading back over this, I'm very aware that this problem seems trivial compared to the issues some members of the forum are facing, so my
thanks again for the replies - it's really appreciated.

Dave

[GarethB]

Dave,

On the plant front and cups of watre you will be surprised at the difference it can make to the immediate area.

I always have a glass of water by me at work and there are a couple of plants next to me resembling baby palm trees. Most the time my eyes are quite comfortable but I do notice the effects of the air con and dry air if i move to the next desk 2 feet away.

The average humidity by my desk is 35% and in the lab it can be as low as 20%.

On the Systane front, I got best resulst by initially using them every two hours and goung without lenses at lunch time. I did this for a couple of weeks by which time I started to notice an improvement. Then gradually I reduced the drops to every three hours, then four hours and so on. Most of the time I just use the drops morning and night.

Systane is slight more viscous than most other eye droips I have tried so have a chance to work their majic on the cornea rather than being washed away in the first couple of blinks.

[Lynn White]

OKay... some corrections needed here!!

"Normal" soft lenses are hydrogels and their oxygen transmissibility is dependent on thickness and water content.. so you can't say definitively that all soft lenses are more or less oxygen transmissible than RGP's.

Silicon hydrogels are stiffer than normal softs so do have the advantage that they can often give better vision (as they don't mould to the eye as much) but they can there fore sometimes be "felt" more than normal eyes if you are sensitive.. (I can't wear 'em myself for that reason!) The difference here is the inclusion of silicon in the polymer.

They are so permeable to oxygen that they are routinely used for extended wear.. ie sleeping in.

They are definitely worth trying and perhaps you might consider the Bausch and Lomb Purevision version. These lenses have aberration control - in other words, enhanced optics that reduce natural visual distortions of the eye, so they may help the flare and ghosting.

Lynn

[GarethB]

Lynn,

Now I am slightly confused, the Kerasoft lenses I hope to collect in January are Silicone Hydrogel?

The concern with fitting them to me I was told by the optom was that they have a lower oxygen permeability than an RGP lens. This they felt would put the graft at risk should it suffer oxygen starvation.

Just wanting to make sure I am understanding things correctly.

[Andrew MacLean]

I only had my kerasoft lens for a very short time before the oxygen issue became critical and I had to stop wearing it. I wonder whether this was as much to do with the fit as it had to do with the material.

Andrew

[Lynn White]

Hmmm...

Well Kerasoft have only just started to be produced in a silicon hydrogel material - before they were a normal hydrogel. Thickness is often the issue here and the fact that any soft lens covers a much larger area than an RGP, in fact oxygen can get around the edges of the lens whereas with a soft, and indeed a scleral, the oxygen has to go through the lens (or indeed a fenestration hole, if one is put through)

However, before I say anything else, I'll check out about the Kerasoft and silicon hydrogel some more and get back to you!

[Dave_W]

Andrew - I totally agree about the fit issue. It's why I can't wear RPGs, as they 'balance' on the cone and either dig into my cornea or get flicked out by my eyelid. This was a major issue for my left eye particularly, as the lens had to be tiny to stay in place for any length of time. This may have changed now that I've had Intacs put in, which has resulted in the cone, well more 'beer belly' bulge with PMD, being almost flattened, i.e. close to normal curvature.

However, I was recommended SHGs a year or so ago, mainly for the potential to reduce the flares but also the improved permeability, but they didn't make them in high enough powers for my prescription at the time. I understand that they've recently begun producing SHGs in higher powers and that it might be possible for them to work for me now.

I did try an SHG lens in my right eye (it was only half a diopter out) at the time, but as that's my good eye, it really wasn't what I wanted at the time (being used to almost perfect vision bar the flares). It seemed to be OK in terms of tolerance though, even if I only had it in for 15 minutes or so. That said, I can't stand rigid lenses for more than a few minutes and although I could 'feel' the lens, it wasn't irritating per se, and, to be honest, I'm willing to give anything a go at the moment even if it ends up not working out.

Lynn - thanks for the information and the recommendation. The key thing for me is whether they go to a high enough power, so I may be limited in choice. I think the optometrist at Sheffield mentioned something about Johnson and Johnson lenses being the ones that went high enough, but I've been wrong before!

I'm popping into see a local optician tomorrow to discuss options and whether SHGs would be suitable for me. I'll post the outcome and any interesting information on this thread.

Gareth - thanks for the info on the plants. Good to know it can make some difference and it's a case of anything that will make things easier, so will get on to the people at work to see if I can have a couple of plants put into my pod. Was talking to my team in work yesterday about this and they were making jokes about having to cut their way through the jungle to find me You might as well keep a sense of humour about these things!