visual acuity vs prescription

Hi,

While browsing the web recently I came across following acuity to prescription strength table:

—.50 D 20/50
—1.00 D 20/100
—2.00 D 20/200
—3.00 D 20/300
—4.00 D 20/400
—5.00 D 20/500
—6.00 D 20/600
—7.00 D 20/700
—8.00 D 20/800
—9.00 D 20/900
—10.00 D 20/1000

Which made me wonder about the accuracy of my prescription. My prescription is -1.5 in both eyes with astigmatism of -0.5 and -0.75 respectively. However during my last eye exam I could read the 20/50 and 20/80 lines with my respective stronger and weaker eyes. The Dr wrote it down on my result sheet.

Could my poor vision be due to some factor that a regular eye test can not detect, but is still corrected with a stronger than necessary prescription?

[John C Hagan]

I would not put much stock in your "finding" on the web. I doubt if it has any basis in fact. Plus a patient with normal eyes and a RX of -2.00 will see 20/20 at 18 inches and the visual acuity will continue to change out to 20 feet.

JCH III MD

[teszler]

I'm a 42 year-old generally healthy woman residing in Europe, with bilateral moderate nearsightedness (-5.5 and -5). I happened to see my doctor at the time when I was just suffering from an eye irritation with increased lacrimation. She diagnosed an eye infection and prescribed local antibiotic drops. At the same time she gave me a visual acuity test (for which I had scheduled the appointment in the first place so as to order a new pair of glasses) and the result was a very disappointing: -6.5 (aggravated) myopia. I was wondering if I can rely on this result, or better have the Snellen test repeated in a week or two when the infection will have subsided? Is it OK to give a prescription for new glasses at the time of conjunctivitis anyway? Thank you, C.Teszler      

[John C Hagan III, MD, FACS, FAAO]

I generally do not do glasses tests in an infected eye. Better repeat after the infection has cleared.
JCH MD

[Cerys3112]

if my prescription is -3.25 and -3.50, what would my visual acuity be? need to know this before applying for a job in the rescue sector!
C Lewis

[John C Hagan III, MD, FACS, FAAO]

It is not possible to tell from a glasses RX what the vision is. Just like looking at a pair of shoes you can't tell how tall the person is.

Assuming you have a eye free of disease your distance vision without glasses is likely 20/200 or worse. Your near vision without glasses is likely 20/20.

Since this important call your "eye doctor" and find out.  If you need to see better for a career in rescue then see an eye MD ophthalmologist and discuss refractive lasik surgery.  Find one near you at www.aao.org

JCH MD