Naked Science Forum
Life Sciences => Physiology & Medicine => Topic started by: bezoar on 24/07/2003 06:23:21
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I have a friend who recently started having the symptom of flashing lights in his peripheral vision, with the subsequent development of a large floater. The ophthalmologist told him that the retina shrinks with age and tugs at the retina, causing the sensation of flashing lights. Sometimes the retina tears slightly and has to be lasered. He says it is more common in nearsighted people. Why? And does having laser surgery for vision correction decrease the odds of developing this tugging at your retina?
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Hi Bezoar
sorry this has taken a little while to get round to, I've been busy...
Anyway, what you have outlined below is correct. The vitreous humour which fills the eyeball can shrink with age and become 'detached', pulling on, and potentially tearing, the retina as it goes. The patient usually complains of abrupt onset of new floaters and often one large, troublesome, floater in particular. If a blood vessel is involved then the person may also complain of seeing a flurry of new floaters characteristically described as "like black rain" and indicating that a vitreous haemorrhage has occurred. Vitreous detachments are more common amongst myopes (the short-sighted) because their eyeballs are frequently more elliptical (rugby-ball shaped) than spherical. This mis-shaping of the eye-ball makes detachment more likely.
A vitreous detachment requires careful monitoring and can precipitate retinal detachment and tearing which is usually heralded by 'flashing lights' seen in the periphery.
If retinal lesions do occur the offending portion of retina can be 'tacked' in place by burning it with a laser, or freezing (cryoretinopexy). Whilst this obliterates the small piece of the retina involved, more crucially it stops the detachment spreading. It may also be necessary to apply silicon sponge splints to the back of the eyeball. These are sutured in place and serve to indent the eyeball at the point of detachment helping to re-establish adhesion between the retina and the back of the eye. If deemed necessary, usually because the central (macula) field of vision is threatened, the vitreous is removed surgically and replaced with either silicon oil (intraocular silicon oil tamponade) or gas eg perfluoropropane. This is called pneumatic retinopexy.
Hope this helps,
Chris
"I never forget a face, but in your case I'll make an exception"
- Groucho Marx
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Thanks Chris,
I think that does answer my question. I assume the placement of the silicon sponges behind the retina is the scleral buckle procedure, which wreaks havoc with your vision afterwards.
The friend had the sensation of flashing lights, followed by the creation of a large brown floater which partially occludes his vision at times. I thought perhaps the brown color indicated hemorrhage. He is, by the way, extremely myopic. And if the problem is more common in myopics due to the shape of the eyeball, then the laser surgery to correct your eyesight wouldn't change the shape of the eyeball, thus logically, the problem would persist.
I had no idea the vitreous could be completely replaced. I guess that would be for a tear or partial detachment that is dangerously close to the macula. What effect does that have on the visual acuity? And would air not be resorbed over time?
Bezoar
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Sorry I forgot to add the answer to your final question about laser correction of vision. Quite right. They laser the cornea to alter the refractive index to compensate for short sight. Laser therapy for retinal disease (e.g. in diabetes) or retinopexy for a retinal tear is directed at an entirely different bit of the eye.
The gas is not air, it's an organic molecule (C3F8).
Chris
"I never forget a face, but in your case I'll make an exception"
- Groucho Marx
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Thanks Chris,
Knew I could count on your medical knowledge for the answer. Did you have any thoughts for the "Heart Problems in a Newborn?" I had to tap my daughter's brain for some answers. The guy sounds like he could use some information.
Bezoar