The College of Optometrists

I hope you can help me before next Wednesday as my exams are next Thursday and Friday! I have only just discovered this forum! I have been reading about tobacco dust and can't quite picture how you look for it, i.e. what techniques do you use? Do you use the slit lamp alone or with a Volk lens? What illumination angle,etc? I have looked in Kanski,etc but I'm still not sure.

Thank you in advance,

Sara

Looking through the slit lamp:

Tobacco Dust is retinal pigment cells loose in the anterior vitreous and are like dark brown speckles

While 'floater' look whispy and white

What you do is make the room very dark The pupil is previously dilated Low magnification, then increase mag as you get a decent picture.

tiny slit at an angle of abt 20 degrees either side of the observation tubes (which are straight on)

Get the patient to look up and down three times to stir up the vitreous

Then look beyond the crystaline lens (so push the slitlamp forwards towards the px). You will see anything that is in the anterior part of the vitreous moving about (it should be clear and you see nothing. In older people you will see floaters as whispy while shapes.

Check its colour - if brown speckly dots floating about, sometimes like a trail of smoke = you have seen it!

there is something to read at: http://www.optometry.co.uk/files/ff576747a2e412712385e953ccd5176d_Hammond19990312.pdf

=steve

Hi Steve,

Thank you so much for you reply. PLease could you help clarify another matter for me concerning contact lenses-again preferably before next wednesday!:) What is the diffference between ionic and ionic contact lenses? I know that four groups that exist but can't find a good source of information that explains this. Thank you.

Sara Powell

How long does tobacco dust remain in the anterior vitreous for??

Hi again

the point is that you can divide problems basically into

stable problems - like dry eye and problems that get worse like retinal detatchment

We can assume that serious problems always get worse.

So once you see tobacco dust - you know that the pigment has gone from the retinal pigment layer into the vitreous (obviously via a break or a hole.

And it will slowly get worse - so over time as the break increases - you will see more tobacco dust as well as other signs.

Contact Lenses the ionic coated lenses resist soiling. THe non-ionic lenses are really obsolete and only used in certain circumstances - for example bandage lenses. But even there = I think they are obsolete. Silicon based lenses have overtaken all this.