Vision questions

[huwbellamy]

Hi all,

it has occurred to me that what we all do is very eye/vision dependent. I am an optometrist (fancy word for ophthalmic optician) and if you have any eye/spectacle/contact lens/vision, etc related queries then feel free to ask. If I don't know the answer I am part of a national forum of Optometrists who probably do. Not looking for business, just might be useful to have someone to ask about eye stuff occasionally.

Huw.

[barkis]

Huw. It's very generous of you to offer advice in your particular sphere of expertise. I would like to ask your opinion on laser corrective procedures. Have they been used over enough time, and on enough subjects to both confirm its usefulness, and in particular , its safety.

Also, is age relevant in the use of these procedures.

Thanks.

Ron.

[Jamie]

Just one thing Ron.

You can forget visual astronomy once you have corrective surgery done mate. (not good for our type of viewing i have heard).

[barkis]

Just one thing Ron.

You can forget visual astronomy once you have corrective surgery done mate. (not good for our type of viewing i have heard).

Then it ends here, I cannot risk being astro blind.

[huwbellamy]

Hi Ron,

laser corrective surgery is still relatively young. Nobody knows what the health of a 90 year old cornea will be like if it has been lasered along the way. Newer procedures with specialist equipment and experienced surgeons are safer from a short term risk point of view but the long term outcomes are unknown.

While high contrast targets are generally unaffected by good laser correction, low contrast targets (such as DSO's) are sometimes more difficult to see. Incidentally, contact lenses can have the same effect i.e: I should be better able to resolve a low contrast image with my specs than my contact lenses.

New "wavefront" laser procedures and contact lenses aim to correct not just short/long/astigmatic sight but also higher order abberations which may actually improve your contrast sensitivity but the jury is still out on the truth there.

There are 3 types of laser correction. PRK carries the least surgical risk but is also the least suitable for higher prescriptions. There can be an extended healing time before vision is stable and there is at least moderate pain for about 2 days after surgery.

Epi-Lasek is the next step in terms of quicker healing and higher prescriptions. Lasik is the procedure of choice for anybody who is long sighted or over -3.00 dioptres short sighted. It is generally pain free and some people have driven home from the clinic. It carries more surgical risk but with the best surgeons you have little to fear.

Costs vary - the corporate clinics employ consultant ophthalmologists and charge about £1500 for bilateral Lasik. A good (top of the field) independent surgeon may charge £4000 for the same procedure. Most patients plump for the former and have good results. On a personal level I would want to know that the person zapping my eyes was as good as could be found.

Age is only relevant from an expected outcome point of view - as a general rule, from 45 years of age onwards a prescription will need to be worn for near vision, this is not going to be corrected by laser treatment. Short sighted folk will therefore be spec free for distance vision until about 45 when near specs are required. Otherwise I have patients in their 20s and 50s who now don't wear specs to drive.

Would I have it done? No - I would hate not having the good vision I enjoy now with specs/CL's. I also don't mind wearing them but there are plenty of people who do.

Sorry about long the windedness but I really got into that. Next.....

[Whippy]

Nice one Huw, I did consider laser surgery a few years back (I am very short sighted!) but I'm glad I didn't in retrospect. Besides I like wearing glasses now, gives me an air of intelligence I clearly haven't got .

Tony..

[Jamie]

gives me an air of intelligence I clearly haven't got

Tony..

I can vouch for that.....

[barkis]

gives me an air of intelligence I clearly haven't got

Tony..

I can vouch for that.....

Och! away wid ye Jamie, yo're the best o pals ye ken. I live near Gretna, so I think I can write in a Scots accent.

[Jamie]

Ye see Tony is a bit of a geezer see....

Got tae keep im on is toes..

[barkis]

Ye see Tony is a bit of a geezer see....

Got tae keep im on is toes..

Can he reach the eyepiece easier then?

Maybe you could call him a Weezer. But, if he's over six foot, hide this message from him.

[Kai]

Ye see Tony is a bit of a geezer see....

Got tae keep im on is toes..

[Whippy]

Ye see Tony is a bit of a geezer see....

Got tae keep im on is toes..

[blakey] I'll get you Butler!! [/blakey]

Tony..

[Greg]

Thanks for the excellent thread and the advice Huw..

I wear the "All day all night" Contact lenses as I am short sighted and at the age where my arms are not long enough any more, so I also have some reading glasses...

I struggle a little at the eyepiece so wear the contact lenses..Although they tend to suffer from glare and "Flaring" Whilst looking at the brighter objects which is a severe inconvenience .

I had considered the laser surgery but decided against it when a colleague of my wife had it done and ended up with ulcers and having to wear dark corrective glasses all the time..

So needless to say I decided against it..

Once again thanks for the advice..

Greg

[barkis]

Huw, I want to thank you for the honest and professional reply you gave. I know whenever I see the ads on TV on laser corrective procedure

they would not lay out the possible drawbacks the way you did. Of course they are trying to sell something, so the small print so to speak, is sowewhat hidden, and besides, they don't have the time. I mostly can get away without them at the eyepiece, but I need the long range seeing part of my bifocals in order to focus my DSLR.

Thanks again HUW, very enlightening.

Ron.

[huwbellamy]

Hi Greg,

Contact lenses are often a source of flare. However, there are several manufacturers of continuous wear contact lenses. Cibavision make "Night and Day" and "Airoptix" - independent studies prove that these suffer more from spherical abberation, etc than Bausch and Lombs "Purevision". There are other brands but as they are new to market I'm not sure about their optical characteristics. It might be worth finding out what sort you wear and asking for a trial of Purevision - take your opticians advice on that though as they may fit differently.

I have astigmatism which means I need specs or contact lenses for a clear image. I prefer my specs for the reason you have given. I am going to find a frame that fits closer to my eyes to help with eye relief - they will probably be horrendous but can be my "observing specs" - I like the idea of looking eccentric and scaring the neighbours.

Spec wearers should ensure their lenses are clean to avoid flare and reflection. Uncoated lenses reflect/scatter approx 10% of incident light while even the cheapest anti-refection coatings reduce this to about 1%. The clearest/hardest and easiest to clean coatings are IKON by Nikon and Alize by Essilor but they are also the most expensive. I wear the cheapest because I change my specs quite frequently and personally I've never had a problem with coating failure. They beed to be cleaned with a proprietory solution or meths with a microfibre cloth.

I'm glad you look intelligent in your specs Tony, I recently asked my wife whether I looked better in specs or without and she chose the specs - charming!

Ron, the adverts on TV are not balanced at all and this has been raised by my governing body and others. The reply was that at the point of supply the judgement on whether to treat or not would be made clinically and all pros and cons explained. See the note above on coatings if you wear specs.

Cheers, Huw.

[geppetto]

Simple question Huw

I have reading glasses and distance glasses but try to get away with

not using either at the scope (more comfortable)

If I did wear my glasses at the scope, which pair should I wear?

Also, going for an eyetest and probably a glasses upgrade shortly.

Should I mention that I use telescopes, is there a more suitable

prescription for that purpose?

Great thread, thanks for taking the trouble mate 8)

[MikeP]

Don't suppose there is anything available to help those of us that are colour blind is there? Red/green in my case.

Mike

[huwbellamy]

Hi Phillip,

I would go without glasses if you don't have a significant level of astigmatism - over 1.00DC in the cyl part of your prescription may be worth wearing a correction for. The Sph part of your prescription refers to the amount of long or short sight but this is taken care of when you focus the scope. You will get less problems with light reflection/scatter and eye relief issues without specs. You should be able to focus an image clearly in distance or reading glasses. If you are going to wear specs then get something close fitting with an anti-reflection coating - no harm mentioning the astronomy to your optician - will likely bring up some relevant lens chat.

Mike, Colour deficient folk can get specially tinted specs or contact lenses from Chromagen - they are quite dark and not legally fit for driving. You wear it in front of one eye to allow alternate monocular viewing - the comparison of the two different shades helps you to identify colours more accurately after a while. Not in general use as of limited benefit and would certainly not help viewing dim objects. It doesn't deteriorate over time and even candidates for the police are allowed a few "fails" in the colour tests.

As a point of interest 1 in 10 men have red/green issues (protanomaly or deutranomaly) compared to 1 in 1000 women - this may explain the wild colours thant men choose for shirts, etc. There is an area on the west coast of scotland that still has a much higher than average rate of colour deficiency due the genes that landed there with nordic people many years ago. Red/green colour problems stem from a lack of lesser number of red and green cone receptors in the retina (we have red, green and blue).

Glad to be of service, Huw. It's still cloudy.

[James]

Huw,

I'm cursed with one good eye (right) and one not so good (left). The left eye is astigmatic (cylinder figure is -2.75) and sphere is +1.25 (short sighted?). The problem is that no optician/prescription ever seems to give me clear views. For example, using just my left eye looking at a crescent moon without glasses the moon is blurred and there are three or four 'copies' of the moon visible around the crescent. With glasses the moon improves slightly with only a couple of fainter moons visible smeared off to one side. Focusing on stars is impossible. With both eyes (glasses or no glasses) the view improves but I suspect thats because my brain just doesn't bother with the nonsense coming into the left eye.

In your opinion (with all relevant waivers attached i.e. I won't sue if I don't like the answer!) am I wasting my time expecting clear sharp views of objects given my apparent prescription i.e. should I stop badgering local opticians?

As an odd side effect I appear to be unable to see stars below mag 5.9 even under the darkest skies yet have extremely good peripheral light sensitivity... :?

[MikeP]

Thanks Huw,

Very interesting, especially the west coast of Scotland bit. Hadn't realised it had anything to do with genes.

Don't suppose anyone is interested in a lovely orange, green and pink tie are they?

Mike

[huwbellamy]

Hi James,

it seems unlikely that your left eye is going to achieve good vision as you have "badgered" opticians to no avail previously. The questions I would ask if I were examining you are:

1. Has it always been that way since childhood - if so it may well be a "lazy" eye (amblyopia). This just means that your brain ignores it because if it didn't your vision with both eyes open would always be hampered by the left eye. Children who are suspected of having a lazy eye are treated by an Orthoptist in a hospital eye clinic setting - usually with specs and a patch over the good eye for about 1 hour per day - this forces your brain to make new nerves that support the affected eye and improve it's sight. This only works up to about age 9, after that no new nerves will be made.

2. Any past history of eye trauma or pathology that is causing the blurred vision.

My guess is the former.

Questions to ask the optician examining you are:

1. Is this a lazy eye? - if so then thats that and what you have is as good as it gets - your left eye prescription will have to be correct for best vision even if it's not your best eye.

2. Is there any eye health issue that could be causing the blur such as early onset cataract? - I think unlikely but worth asking as this can cause images to double or split

The splitting of images/double vision is most likely due to the astigmatism, especially without specs.

Your eyes are more sensitive to light in darker conditions when you use your peripheral vision as the central part of your retina (the macula) has no rod cells. Rods are massively more light sensitive than cone cells and are spread diffusely throughout your peripheral retina. There are lots of cones in the central macula zone - they give excellent resolution and colour perception under bright light. Rods are black and white only. Cones are hopeless in dark conditions while rods are knocked out during daylight and take about 40 minutes to reach full effect if the lights are switched off. This is why averted vision works on faint objects. Dusk is a difficult time visually as your eyes are not getting a full cone or rod response.

For a strange visual feeling - Dark adapt for 30 minutes. Completely cover one eye to seal it against light. Turn the lights on for a few seconds so one eye light adapts. Turn the lights off again and uncover the light adapted eye. It makes you realise how differently a light and dark adapted eye sees and feels odd - the light adapted eye is practically useless in the dark. Amazing. We were dweebs in college.

Huw.

[huwbellamy]

Thanks Mike, I have plenty of nasty ties but have no colour vision defect to blame. I stopped wearing them when I realised I looked like Colin Hunt - the office joker off the Fast Show.

Genes are where it's at. Mums carry the gene but don't have the defect. Boys inheriting the gene do.

Huw.

[James]

Hi James,

it seems unlikely that your left eye is going to achieve good vision as you have "badgered" opticians to no avail previously.

Darn...oh well, I'll lay off the opticians! It started going odd in 1998. The sudden onset was enough to have me referred to a specialist at hospital who had a look the same way the optician did and said there's nothing wrong which was both reassuring and worrying. I'm prone to migraines and one of the triggers are visual stimuli but I've no way of knowing if the eyesight causes the migraines or whether the migraines & eyesight are a symptom of something else!

Regarding lazy eyes my optician did say that glasses were a good idea to stop my left eye becoming lazy as there was evidence my brain was ignoring its input (as it ignores many inputs ).

If glasses aren't going to fix the problem completely I'll just stop whinging. Maybe I should be grateful I can see several moons at once... One of my work colleagues has had his cataracts done over the last 18 months, his joy at being able to see reasonably well again makes me feel bad for complaining about my vision!

James

[huwbellamy]

Hi James,

the migraines may cause 10 to 60 minute binocular visual disturbances but are unlikely to be the fault of your left eye. In addition to my earlier guesses, if your left eye has only been getting astigmatic for 10 years or so and vision with specs is split then I would consider slight keratoconus as a possibility. This is where your cornea is slightly more steeply curved than average (Kerato = cornea, Conus = cone shaped). Only way to establish this is by asking your Optician to examine it. If so then contact lenses may give you better vision as the irregular nature of the astigmatism is better corrected.

It is difficult to say without seeing you but probably worth asking about just to get confirmation. Eye professionals differ in their opinion on keratoconus as some regard mild cases as just higher than average astigmatism. Either way I wouldn't be concerned but perhaps ask at your next visit.

Hope this helps, Huw.

[James]

Hope this helps, Huw.

It does a lot, thank you Huw. After my last test I had a chat with the optician about astronomy/optics and he said next time I came in there were a few things he could check out so I'll raise this one although having just read up a little about it on the internet I'm not sure I want to know! The problems with my left eye came on over 2-3 years then appeared to stabilise for a while but my last test (3 weeks ago) shows a worsening of the astigmatism. Slightly worrying the optician notes that my right eye now displays very slight astigmatism but he made the point that it was at the limit of detectability and he only remarked on it as I was being fussy...

On the assumption that most people aren't interested in my eyesight I'll shut up now but thanks for your input Huw. Its useful to 'speak' to someone who isn't seeing customer number 10 in a long busy day!

James