Ophthalmology & Optometry/Prisms


QUESTION: I am 62 yrs old, active, and have worn glasses since 5th grade.  I get regular eye exams from a local eye center with several ophthalmologists and optometrists.  I have seen one specific ophthalmologist every year for over 10 years. I get refracted there by an optometrist every other year.
My current prescription is:

RT  -3.75     +1.25  080          +2.25  n/a
LT  -2.50     +1.25  120          +2.25  N/A

My 2011 exam showed minimal change so I kept the same "no-line" Crizal lenses.  

I have had dry eyes for several years, plugs, and use eye drops.  They are moderately dry.  I use drops 1-3 times a day and it helps some.

For about a year, I was having trouble seeing, to the extent I would remove my glasses in the house.  My opthamologist said that I had some clouding of the lens consistent with the aging process, but not enough to need surgery. He said that wold improve my nearsightedness and weaken my farsightedness.   I asked several questions and got curt replies.  He said that I had to make a separate appointment with their optometrist to have my vision checked. So, I opted to go to an optometrist that had his own private practice for an opinion.

My previous scripts were  written by different optometrists who worked this particular eye center.  I took my scripts with me.  The new optometrist checked my eyes and recommended prisms.  He determined this by using something to create a double image over one eye and asked me to tell him when the images were in line either vertically or horizontally.  He did this many times.  He checked my glasses and they did not have prisms.  He called my ophthalmologist and verified that neither the 2009 nor the 2011 scripts had prisms.

I needed to leave my Silhouette frames with him and did not have an old spare with me.  I returned the next day with my 2007 glasses.  I told the optician that I could see better with these glasses.  I usually use them for gardening, tree trimming, etc.  She checked them and they had prisms!  She did some additional measurement and had to turn my head back and forth.

Here are my questions:

1.  Can a  person go from needing prisms to not needing them and then go back to needing them?

2.  Is there an underlying medical condition that I should be concerned about?

3. Is there another test for prisms?

Thanks for your help.

ANSWER: It is slightly unusual to have and then *not have* the need for prism. Prism displaces the image, effectively 'moving' the world for you, so the muscles in your eyes don't have to strain as much.  There are two ways to measure the need for prism, one is to use a paddle and alternatively occlude the right then the left eye, while you're looking at a target. If the target jumps to the side when they switch eyes, they would use a prism bar to neurtralize the movement.  See the video linked below...
The other way is the more common way, which you described.
The need for prism is generally nothing to be concerned about, unless it changes dramatically.
Good Luck!

---------- FOLLOW-UP ----------

QUESTION: Thank you for the prompt answer.  Two more questions . .

You said that I should not be concerned unless it "changed dramatically".

What would constitute a dramatic change?  I do not know what my new prescription is. But my Dr said he was going to back off his prism measurement slightly to see how I will tolerate it.

If is a significant change, what possible medical conditions might be causing this?  

Thanks again.

The concern for the need for prism is that it indicates to us that you have a hard time focusing both eyes on the same target in 3D space for a period of time. Sometimes this is from an physiological muscle weakness (if it's been present for a while, or slightly changes over time).  There are other things that can change how your eyes align themselves, causing a muscle/nerve weakness, that are more sinister.  More scary and serious things (although very rare) would include thyroid disease, stroke, infection, and inflammation.  These things are typically more progressive, changing (worsening) over time.
It doesn't sound like your has dramatically changed or progressed, but, if you are in doubt have a conversation with you doctor about it!

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John M. Dovie, OD, FAAO


As a residency-trained Fellow of the American Academy of Optometry I am able to answer most questions regarding eye and vision health. Anything is welcome, ranging from dry or allergy eyes, bifocal contact lenses, or thoughts on LASIK surgery. As I am not a surgeon, detail-oriented surgical-related questions may be better answered by an ophthalmologist.


Selected to participate in the PCO residency program in Philadelphia at The Eye Institute, where I worked OD and MD specialists gaining invaluable experience in various clinics including glaucoma, cornea and cataract, oculo-plastics, retinal disease, neuro-ophthalmic disease, primary care, emergency medicine, and special populations. Have practiced and trained in numerous settings including hospital, academic, retail and private practice. I earned my Fellowship in the American Academy of Optometry (FAAO). There are currently only about 3000 active fellows worldwide, and there are only about 70 Fellows in the state of Virginia. I currently own and operate my own optometric practice/clinic.

American Academy of Optometry, American Optometric Association (Contact Lens/Cornea Section member since 2001), Southwest Virginia Optometric Association, Virginia Tech Alumni Association

“Nyctalopia as the Presenting Sign of Vitamin A Deficiency: A Late Complication of Gastric Bypass Surgery.” Clinical Case Study Poster presented at The American Academy of Optometry Denver, Colorado, December 2006, co-authored with Bradley Lane, OD.
“The Importance of Considering Paranasal Sinus Mucocele as a Differential Diagnosis in Diplopia.” Clinical Case Study Poster presented at The American Academy of Optometry San Diego, California, December 2005, co-authored with Kelly Malloy, OD, FAAO and Cherie Farkash, OD.
“Acute Onset of Halos and Glare: Bilateral Keratitis—An Atypical Presentation of Amiodarone Keratopathy.” Clinical Case Study Poster presented at The American Academy of Optometry Tampa, Florida December 2004. Also Presented to New Jersey Academy of Optometry, Neptune, New Jersey March 2005.
“The Opportunity for an Optometrist to Save a Life.” Clinical Case Study and Grand Rounds Presentation presented at The Pennsylvania College of Optometry, Philadelphia, Pennsylvania, September 2004.
“Corneal whorls cause wonder.” Clinical Challenges Quiz, co-authored with Andrew Gurwood, OD, FAAO, Review of Optometry. Published 10/15/2006.
“Acute onset of halos and glare: bilateral corneal epithelial edema with cystic eruptions--atypical presentation of amiodarone keratopathy.” Co-authored with Andrew Gurwood, OD, FAAO. Published February, 2006, Optometry.
“Pondering the posterior polka-dots.” Clinical Challenges Quiz, co-authored with Andrew Gurwood, OD, FAAO, Review of Optometry. Published 5/15/2005.
Professional Involvement:
“AION: Amiodarone-Induced or Anterior Ischemic Optic Neuropathy?” Participated as a peer-review referee for Expert Review of Ophthalmology (London, UK); refereed 10/2006.

Bachelor of Science, Cum Laude, Virginia Tech. Bachelor of Science, Pennsylvania College of Optometry. Doctorate (OD), Pennsylvania College of Optometry Residency, Pennsylvania College of Optometry Fellow of the American Academy of Optometry

Awards and Honors
Winner, First Place, "Best Beside Manner" by Our Health Magazine: 2012, 2013, 2014 Winner, First Place, "Best Eye Doctor" by The Roanoke Times: 2013, 2014 Recognized as a Fellow of the American Academy of Optometry, December, 2006 Recipient of the Onofrey G. Rybachok Memorial Scholarship, 2000-2001 Member: The Golden Key International Honor Society Member: The National Biological Honor Society Member: The National Honor Society Eagle Scout awarded 1994

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