Some years back one of our members posted this:
Take this to your next eye exam.
BULLSEYE SHOOTERS' GUIDE FOR THE EYECARE PROFESSIONAL
Dear Colleague,
My name is Norman H. Wong, O.D. and I am a member of the California Optometric Association and the American Optometric Association. I am also a veteran, a life-member of the NRA and a competitive bullseye shooter. Bullseye shooters are a wonderful group of individuals with critical visual needs. Please put aside any political views against firearms, if any, and treat the bullseye shooter as you would any other patient. The patient had asked for permission to bring his/her firearm(s) to the office for the eye examination and will demonstrate that the firearm is unloaded and safe. If the patient was denied, sighting parts of the pistol(s) were brought instead. Take a moment to review these important steps before and during your eye examination. Besides your routine health tests of the eyes, I have emphasized a few areas of concern. Your kind attention to details would be most appreciated.
EYE EXAMINATION
1. CASE HISTORY: A thorough case history revealing any medical problems which
may relate to eye health and vision stability is essential. Note all medications
taken, including over-the-counter medications and advise of possible visual side
affects.
2. DOMINANCE: Review and confirm eye dominance and hand dominance.
3. REFRACTION: Your best effort is needed to obtain the most accurate results.
After you obtain your best distance Rx, see if the patient is sensitive to 0.12
diopter steps. Please double check vertex distances especially for higher
powers. Check to see if the patient's line of sight is "continually" centered
through the phoropter lenses. Do not reduce the full strength of the
prescription even if there was a large change from the previous examination
results. Small prescriptions such as +0.25, -0.25 diopter sphere and +0.25,
-0.25 diopter cylinder, even if obliquely orientated, may be significant.
4. RED DOT SCOPES: Normally, the best lens for the red dot scope viewing would
be the best distance prescription. Demonstrate this lens while the patient looks
at the red dot while holding out the scope. Because the red dot in the scope is
not focused at "optical infinity" (it is closer), try a +0.12 or a +0.25 diopter
lens over the best distance prescription to see if the dot becomes even clearer.
If possible, judgment would be best if the patient can view at a distance
greater than the standard 20 feet and with outdoor lighting. If the dot is
distorted, use the phoropter once again to verify cylindrical power and axis as
the patient holds the pistol (or scope only) in front of the phoropter. Final
results may be demonstrated with trial lenses. If after all lens possibilities
have been demonstrated and the red dot never became clear and round, then a
careful determination of ocular health involvement needs to be assessed.
5. IRON SIGHTS: We are concern with three separate entities, the clarity of the
front sight, the clarity of the rear sight and the relative blurriness of the
bullseye. These three positions cannot be focused simultaneously with just a
lens. The rear sight is separated from the front sight by about 6 3/4 inches in
most standard 1911 .45 caliber pistols. Measure the EXACT distance from the
patient's shooting eye to the rear of the front sight while he/she is in the
proper stance. Write this down for the patient's record. Set this distance for
the reading card on the rod of the phoropter. Find the best lens for this
position and then try 0.12 diopter higher and 0.12 diopter lower and note if the
patient responds to this small change. Presbyopic patients will give good
responses. For the pre-presbyopes, low power lenses may allow for a more stable
focus. Younger patients under 35 years of age may benefit from a minimal plus
power for a steadier focus, or perhaps none at all.
The patient needs to know the best plus lens because there are specialty type
shooting glasses with interchangeable lenses. The two popular ones are Knobloch
Optik and Neostyle Champion systems which include lenses, occluders, apertures
and side blinders. There are a number of lenses available with these systems
(+0.50, +0.75, +1.00, +1.25, +1.50). The base lens (patient's distance
prescription) can be custom made at the optical lab to incorporate into this
system. This interchangeability allows for a quick change when different powers
are needed for various shooting distances and lighting conditions. Personally,
my best lens for the front iron sight stays the same under day and night
lighting situations. In my case and in many other patients', we prefer a
dedicated pair of shooting glasses for the iron sights, which may also be
helpful as a computer Rx and for other hobbies at a similar working distance.
Next, have the patient view this best lens with the pistol in hand at a distance
greater than 20 feet, and if possible, outdoors at 25 and 50 yards. Majority of
offices may have limitations. Depending upon a few factors such as arm length
and pupil size, typical lenses that work best are +0.50, +0.75 and +1.00 diopter
over the best distance prescription but also try +0.37, +0.62 and +0.87 diopter
lenses even though these are uncommon powers. You may be surprised how sensitive
some shooter's eyes may be. In my case, +0.75 diopter is my ideal lens. A +0.62
diopter lens blurs the rear sight and a +0.87 diopter lens blurs the bullseye
too much. Experienced shooters would know that the distance bullseye will be out
of focus. As different lenses are tried, this will allow the patient to compare
the relative blurriness to the bull. Stress that front iron sight clarity is
more important than the bull clarity. Most shooters know that an adjustable
aperture will then help clear the bullseye.
l. When too much emphasis is given to the bull clarity, then the rear sight clarity
will be compromised. The patient will always shoot better if the front and rear
sights are perfectly clear and aligned while the bull is blurred rather than if
the bull is clear and the sights cannot be seen well enough for proper
alignment. Always use the lowest plus power lens to achieve this goal.
As a quick reference guide, here are the focal lengths of the powers discussed:
+0.37 diopter: 2.66 meters
+0.50 diopter: 2 meters
+0.62 diopter: 1.6 meter
+0.75 diopter: 1.33 meter
+0.87 diopter: 1.14 meter
+1.00 diopter: 1 meter
Lens determination by focal lengths alone may cause erroneous results. This
should be used only as a starting point.
6. BINOCULARITY: Advise the patient if there are any binocular problems which
may affect focusing stability. Most shooters occlude one eye but some shoot with
both eyes open and suppresses the non-dominant eye. Hyperopic patients who are
esophoric may have more of a difficult time if eyeglasses are not worn. Again,
low power lenses need to be prescribed if the patient desires clear and stable
focus.
7. CORNEA: Carefully inspect for any corneal defects including beginning signs
of keratoconus. Note and advise the patient of any old scars and dystrophies
along the visual axis which may compromise the focus of the red dot. Check
corneal curvatures with the keratometer or use corneal topography for
irregularities. Check the tear film and advise of any possibility of dry eyes
which may cause unstable focus. Recommend dry eye therapy as needed. Use of
ocular lubricants may be beneficial before and during shooting.
8. LASIK and RADIAL KERATOTOMY: Foreign matter introduced in the interface and
other complications during LASIK procedure may or may not affect vision. Advise
accordingly. Irregular astigmatism may result from radial keratotomy and distort
the red dot. Frequently, we will have an undercorrection or an overcorrection
after surgery and the full lens prescription needs to be given.
9. CONTACT LENSES: Patients correctable to 20/20 or better frequently see only
20/25, 20/30 or worse with contact lenses. This may be due to small uncorrected
astigmatism, contact lens surface deposits, or desiccation of the soft lens
material. Contact lens lubricants may help when used before and during a match.
A shift in vision may be noted when toric contact lenses rotate. These minor
problems may be acceptable to the patient.
10. PUPILS: Note if the patient's pupil is unusually small or large. A small
pupil will allow for a longer depth of focus but may cause more symptoms with
lenticular opacities. A wide pupil will cause a short depth of focus and will
make our job a little more challenging to find the best lens possible. As the
amount of ambient light changes throughout the day, the pupil size will also
change and may give different sighting appearances. Inspect the iris for
colobomas and for trans-illumination defects which may cause diplopia and glare.
11. CRYSTALLINE LENS: Note and advise the patient of any lenticular opacities
which may affect the viewing of the sights. Commonly seen opacities may not
affect the non-shooters but will affect the shooters' clarity of the red dot or
iron sights. Senior patients who have had intra-ocular implants need to be
closely inspected for signs of posterior capsular opacities.
12. MACULA: Closely inspect the macular area for any signs of defects including
ARMD. Use of Amsler Grid may be helpful.
EYEGLASS SELECTION
1. LENSES: Review past lens types and materials used. Discuss what has worked
and what has not. Review ABBE VALUE of various lens materials and possible
distortions especially in higher powers. Polycarbonate is the only FDA approved
safety material that is widely used today and is always recommended as the first
choice. Other materials may be used ONLY with the patient's understanding that
they are not approved safety materials. If needed, the patient may be required
to sign a waiver of responsibility. Many patients choose to have a dedicated
pair of shooting glasses which should be polycarbonate and then other materials
may be used for their dress eyeglasses. Note that Knobloch Optik and Neostyle
Champion lenses come only in CR-39 plastic. When writing up the lab order,
request for "exact power required" and reject lenses that are not exact even
though they fall at the limits of the ANSI standards of power, +0.12 and -0.12
diopter.
2. EYEGLASS FRAMES: Frames should not be too small and flimsy such as rimless.
Safety frames following ANSI standards would be best. Wrap-around style frames
may require steeper base curve lenses which may cause distortions. Some sports
frames which have a one piece curved front shield may have inserts which will
allow for the patient's prescription lenses. These goggle type frames have no
adjustability, important with moderate to high prescriptions. Being that there
are four surfaces, fogging and cleaning may be a problem.
3. MULTI FOCAL HEIGHT MEASUREMENTS: Have the patient demonstrate their head
posture while at their "shooting stance" as you take the proper height
measurements. Extreme diligence needs to taken so that the line of sight is not
impeded by the near or intermediate portion of the lens. When measured
correctly, there should be no restrictions with bifocal, trifocal and
progressive lenses. Verify that the measurement taken with the shooting stance
is also compatible with the patient's normal daily use.
4. ANTI-REFLECTION COATINGS and ULTRAVIOLET COATINGS: Discuss the advantages of
AR coatings which will reduce glare as well as reflections and UV coatings for
blocking harmful UV rays of the sun.
5. TINTS: Kalichrome (yellow) enhances contrast but offers very little shading
and may be helpful in low light settings. PLS 530 (orange) and PLS 540
(orange-brown) are tints which block all wavelengths above their stated levels.
I have found that it is best for the patients to view tint samples and have them
report what is most comfortable. Transitions photochromic lenses lighten and
darken with the amount of direct sunlight and its usage is very convenient.
Avoid "fashion tints" which have no protective qualities. If possible, loaning
samples for the patient to view at the range would be most helpful.
I am constantly learning more of the bullseye shooter's needs as I continue to
participate in this rewarding sport and have been revising and adding onto this
list. I will, from time to time, update this list as needed. Bullseye shooters
are intelligent, honest, law-abiding citizens with much character. You now also
have a very happy patient and we invite you, your family and friends to join us
and see what BULLSEYE SHOOTING is all about.
Regards,
Norman H. Wong, O.D.
Haywire
MBTV
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