PURPOSE: This rule sets forth procedures to
evaluate visual disability.
(1) Compensable disability for loss of vision
should be based on that proportional part of the compensation provided by law
for loss of use or loss of function of one (1) or of both eyes which expresses
the percentage loss of visual efficiency of the individual.
(A) Visual acuity as used in this rule means
the best acuity obtainable at twenty feet fourteen inches (20'14") without the
use of ophthalmic lenses, except that corrective lenses shall be used for
natural presbyopia and other conditions clearly not the result of
injury.
(B) Visual efficiency is
defined as that degree or percentage of competence of the eye to accomplish its
physiologic function.
(C) Loss of
binocular single vision is equivalent to the loss of use of one (1)
eye.
(D) The reduction in visual
acuity to 20/200 (6/60 where the metric system is used) or a reduction in
visual efficiency to ten percent (10%) or less constitutes industrial
blindness.
(E) When both eyes are
involved in a permanent visual disability, the efficiency of the coordinate
function of both eyes should be determined on the basis of permanent partial
disability of the body as a whole.
(2) There are three (3) elements of vision,
each of which has an interdependent and coordinate relation to full visual
efficiency. These coordinate factors are acuteness of vision (central visual
acuity), field of vision and muscle function. Although these factors do not
possess an equal degree of importance, no act of vision is perfect without the
coordinate action of all. Other functions, though secondary and dependent, are
recognized as important, such as, for instance, depth perception, stereoscopic
vision, fusion sense, color perception, adaptation to light and dark and
accommodation. These secondary functions are inherently dependent on the status
of the three (3) primary coordinate functions of vision and they also depend
upon the condition of the central nervous system.
(3) In order to determine the various degrees
of visual efficiency, a) normal or maximum, and b) minimum limits for each
coordinate function must be established, that is, the one hundred percent
(100%) point and the zero percent (0%) point.
(A) The maximum efficiency for each of these
is established by existing and accepted standards.
1. Central visual acuity. The ability to
recognize letters or characters with subtend an angle of five (5) minutes, each
unit part of which subtends a one (1) minute angle, is accepted as standard.
Therefore a 20/20 (6/6 metric) Snellen is employed as the maximum acuity of
central vision or one hundred percent (100%) acuity.
2. Field vision. A visual field having an
area which extends from the point of fixation outward eighty-five degrees
(85°), down and out eighty-five degrees (85°), down sixty-five degrees
(65°), down and in fifty degrees (50°), inward sixty degrees (60°),
in and up fifty-five degrees (55°), upward forty-five degrees (45°),
and up and out fifty-five degrees (55°) is accepted as one hundred percent
(100%) industrial visual field efficiency.
3. Muscle function. A maximum normal muscle
function is present when binocular single vision is present in all parts of the
field of binocular fixation or when there is no limitation of motion in either
eye.
(B) The minimum
limit or the zero percent (0%) of each of the coordinate functions of vision is
established as that degree of deficiency which reduces vision to a state of
uselessness.
1. Central visual acuity.
Experience, experiment and authoritative opinion establish that a distance
central visual acuity of 20/200 Snellen and a near central visual acuity of
14/140 is the accepted threshold of industrial blindness.
2. Field of vision. The minimum limit for
this function is established as a concentric central contraction of the visual
field to five degrees (5°). This degree of contraction of the visual field
reduces the visual efficiency to zero (0).
3. Muscle function. The minimum limit for
this function is established by the presence of diplopia in all parts of the
motor field, the loss of binocular single vision or inability to rotate the eye
to any point of fixation in the normal motor field. These conditions constitute
zero visual efficiency.
TABLE NO. 1
Percentage Loss of Visual Efficiency Corresponding to
Snellen Notations for Distant and for Near Vision for Measurable Range of
Quantitative Visual Acuity Using 20/200 = 100% Loss
|
Snellen Notation at 20 feet or 6 m
|
Snellen at 14 inches
|
Percentage of Visual Efficiency
Retained
|
Percentage of Visual Efficiency Loss
|
|
20/20
|
14/14
|
100.0
|
0.0
|
|
20/25
|
14/17.5
|
94.0
|
6.0
|
|
20/30
|
14/21
|
88.0
|
12.0
|
|
20/35
|
14/24.5
|
82.4
|
17.6
|
|
20/40
|
14/28
|
77.4
|
22.6
|
|
20/45
|
14/31.5
|
72.8
|
27.2
|
|
20/50
|
14/35
|
68.1
|
31.9
|
|
20/60
|
14/42
|
60.0
|
40.0
|
|
20/70
|
14/49
|
52.5
|
47.5
|
|
20/80
|
14/56
|
46.4
|
53.6
|
|
20/90
|
14/63
|
41.2
|
58.8
|
|
20/100
|
14/70
|
35.9
|
64.1
|
|
20/120
|
14/84
|
27.8
|
72.2
|
|
20/140
|
14/98
|
20.2
|
79.8
|
|
20/160
|
14/112
|
13.0
|
87.0
|
|
20/180
|
14/126
|
6.0
|
94.0
|
|
20/200
|
14/140
|
0.0
|
100.0
|
(4) Visual acuity shall be measured both for
distance and for near, using the Snellen notation, each eye being measured
separately. Central visual acuity for distance shall be measured at a test
distance of twenty feet (20') or six meters (6 m). Central visual acuity for
near shall be measured at a test distance of fourteen inches (14") or
thirty-five centimeter (35 cm). The best central visual acuity obtainable
without the use of ophthalmic lenses shall be used in determining the degree of
visual efficiency, except when natural presbyopia or other conditions clearly
not the result of injury exist; then it is permissible to measure the visual
acuity both for distance and near with correction. As an example, a high myopia
with a vision without correction of 20/200 or less in each eye should be
measured with the best corrective lenses, using the best vision of the
uninjured eye as a standard. The practical difficulties of fitting, expense of
and tolerance of wearing contact lenses are too great at the present time to
favor the use of other than regular ophthalmic lenses to determine the best
corrected vision. Having determined the best visual acuity for twenty feet
fourteen inches (20'14"), the visual efficiency is ascertained by the weighted
values assigned for central visual acuity at twenty feet (20') and central
acuity at fourteen inches (14"). A one-fold value is given the distance vision
and a twofold value is given for near vision. As an example: best visual acuity
twenty feet (20'), 20/40; best visual acuity fourteen inches (14"), 14/35.
Reference to Table No. 1 shows 20/40 equals 77.4 retained visual acuity and
14/35 equals 68.1 retained visual acuity. Thus the visual acuity efficiency for
one eye would be ((77.4 × 1) plus (68.1 × 2)) divided by 3 equals
.712 or 71.2% visual acuity efficiency (or a 28.8% loss).
(5) The extent of the field of vision shall
be determined by the use of the usual perimetric test methods, a white target
being employed which subtends a one degree (1°) angle under illumination of
not less than seven (7) footcandles and the result plotted on an ordinary
visual field chart as shown on Figure No. 1.
(A) Normal Field. A visual field having an
area which extends from the point of fixation outward eighty-five degrees
(85°), down and temporally eighty-five degrees (85°), down sixty-five
degrees (65°), down and nasally fifty degrees (50°), nasally sixty
degrees (60°), up and nasally fifty-five degrees (55°), up forty-five
degrees (45°), up and temporally fifty-five degrees (55°), giving a
total of five hundred (500) is established as a normal field of
vision.
(B) An Abnormal Field. The
amount of radial contraction in the eight (8) field sectors, measured in their
principal meridians, shall be determined. The sum in degrees of the eight (8)
principal radii of the visual field (which normally is five hundred (500)) will
give the visual field efficiency of one (1) eye in percent when divided by
5.00.
Click
here to view image
Example: The following represent the findings in an abnormal
field of vision in one (1) eye
|
Upward
|
40 degrees
|
|
Up and Out
|
40 degrees
|
|
Outward
|
70 degrees
|
|
Down and Out
|
60 degrees
|
|
Down
|
50 degrees
|
|
Down and In
|
50 degrees
|
|
In
|
45 degrees
|
|
Up and In
|
35 degrees
|
|
TOTAL
|
390 5.00 78%
|
which is the field of vision efficiency of the affected eye.
(See Field of Vision Chart).
(6) Muscle function shall be measured in all
parts of the motor field, recognized methods being used for testing. A maximum
normal extraocular muscle function is present when there is absence of diplopia
(double vision) in all parts of the field of binocular fixation. Where diplopia
is present, it shall be plotted on the motor field chart. This chart is divided
into twenty (20) rectangles twenty by twenty-five degrees (20°
×
25°) in size, as shown in Figure No. 2.
Click
here to view image
Motor field chart at 40 inches is approximately 40 inches
square, and the 20 rectangles measure 8 inches by 10 inches.
The partial loss of muscle function due to diplopia is that
proportional area which shows diplopia, as indicated on the plotted chart,
compared with the entire motor field area. It shall be measured without
corrective lenses, red glass or prism. For example, to determine the motor
field efficiency of the eyes, assume the motor field chart shows a diplopia in
eight (8) out of twenty (20) rectangles of the entire field. By referring to
the Motor Field Chart, Figure No. 2 and Table No. 2, it is found that a loss of
8/20 gives a forty percent (40%) motor field loss or an efficiency of sixty
percent (60%).
TABLE NO. 2
Loss in Muscle Function
|
|
Loss
|
Retained
|
|
1/20
|
=
|
5%
|
95%
|
|
2/20
|
=
|
10%
|
90%
|
|
3/20
|
=
|
15%
|
85%
|
|
4/20
|
=
|
20%
|
80%
|
|
5/20
|
=
|
25%
|
75%
|
|
6/20
|
=
|
30%
|
70%
|
|
7/20
|
=
|
35%
|
65%
|
|
8/20
|
=
|
40%
|
60%
|
|
9/20
|
=
|
45%
|
55%
|
|
10/20
|
=
|
50%
|
50%
|
|
11/20
|
=
|
55%
|
45%
|
|
12/20
|
=
|
60%
|
40%
|
|
13/20
|
=
|
65%
|
35%
|
|
14/20
|
=
|
70%
|
30%
|
|
15/20
|
=
|
75%
|
25%
|
|
16/20
|
=
|
80%
|
20%
|
|
17/20
|
=
|
85%
|
15%
|
|
18/20
|
=
|
90%
|
10%
|
|
19/20
|
=
|
95%
|
5%
|
|
20/20
|
=
|
100%
|
0%
|
(7)
The industrial visual efficiency of one (1) eye is determined by obtaining the
product of the computed coordinate efficiency values of central visual acuity
of field vision and of muscle function. Thus, if central visual acuity
efficiency is forty percent (40%), visual field efficiency is eighty-one
percent (81%) and the muscle function efficiency is one hundred percent (100%),
the resultant visual efficiency of the eye will be 0.40 × 0.81 ×
1.00 equal 32.4% (a loss of 67.6%). Should the motor efficiency be reduced
fifty percent (50%) in the example given, the visual efficiency would be 0.40
× 0.81 × 0.50 equal 16.2% (a loss of 83.3%).
(8) It is a fact, established by common
experience, that visual efficiency is by no means reduced to one-half (1/2) by
the complete loss of one (1) eye, the vision in the fellow eye remaining
normal; and it is also a fact that a permanent visual disability, total or
partial, involving both eyes is not equivalent to the sum of the visual
disabilities computed separately for each eye. Hence, the necessity arises to
give a weighted average when a permanent binocular disability is present. For
the complete loss of the sight of one (1) eye, the Missouri Workers'
Compensation Law allows one hundred forty (140) weeks; when there is permanent
partial loss in both eyes, the disability evaluation is on the basis of four
hundred (400) weeks (disability to the body as a whole). It should be noted
that when an employee has sustained a permanent partial disability involving
both eyes and a part of this disability is due to a loss in the binocular motor
fields (determined by the area of diplopia), the loss of motor field efficiency
is used only in computing the loss in the less efficient of the two (2) eyes.
Therefore, the estimation of visual efficiency in the more efficient of the two
(2) eyes is determined by using only the factors of central visual acuity and
the field of vision efficiency. The formula for computing binocular visual
efficiency loss in weeks is as follows: To the loss of visual efficiency of the
poorer eye in weeks (based on the percentage of value of one (1) eye in weeks,
one hundred and forty (140) being the basis) add the loss of visual efficiency
of the second eye in weeks (based on the percentage of the difference between
the value of one (1) eye in weeks and the value of both eyes in weeks, that is,
four hundred (400) less one hundred forty (140) or two hundred sixty (260)
weeks). For examples: poorer eye (right eye), seventy-five percent (75%) loss,
140 ×.75 = 105 weeks; second eye (left eye), five percent (5%) loss, 260
×.05 = 13 weeks; binocular visual efficiency, loss one hundred eighteen
(118) weeks.
(9) Certain types of
ocular disturbance are not included in the foregoing computations and these may
result in disabilities, the value of which cannot be accurately measured by any
scientific method available. Among them are disturbance of accommodation, of
color vision, of adaptation to light and dark, metamorphopsia, entropion,
ectropion, lagophthalmos, epiphora and muscle disturbances not included under
diplopia. For such disabilities, additional compensation shall be allowed, but
in no case shall such additional compensation make the total for loss in
industrial visual efficiency greater than that provided by law for the total
loss of the sight of one (1) eye when only one (1) eye is involved and that for
permanent partial disability of the body as a whole when both eyes are
involved.
(A) Compensation for loss in
industrial visual efficiency, as provided for previously in this rule, does not
include compensation for any cosmetic defect, for mental or physical suffering,
for cost of medical attention or for time lost from gainful occupation during
the period of treatment previous to final computation of compensation as
provided for in the following subsections. Additional compensation should be
allowed for the various losses hereinafter enumerated.
(B) Defects of form or structure of the eye,
congenital or developmental in origin, such as regular astigmatism, myopia,
hyperopia and presbyopia will not in themselves be regarded as traumatic in
origin.
(C) Irregular astigmatism
may be due to corneal scars, inflammation, injury or operation and is
compensable if it is.
(D) Combined
ratings of disabilities of the same eye shall not exceed the amount for total
loss of sight of that eye. However, any cosmetic defect shall be noted in the
report.
(E) Although no scientific
deductions can as yet be made as a basis for determining disabilities arising
from those secondary ocular defect not included in the foregoing computations
in the three (3) primary and coordinate factors of vision, experience and sound
judgment, as expressed in the following table, give a yardstick for estimating
losses due to so-called secondary ocular disabilities.
(F) Compensable disability shall not be
computed until all adequate and reasonable operations and treatment known to
medical science have been offered to correct the defect. Final examination on
which compensation is to be based shall not be made until at least three (3)
months shall have elapsed after all visible evidences of inflammation have
disappeared, except in cases of disturbance of extrinsic ocular muscles, optic
nerve atrophy, sympathetic ophthalmia, traumatic cataract and paralysis of
accommodation; in such cases at least twelve (12) months and preferably not
more than sixteen (16) months shall intervene before the examination shall be
made on which final compensable disability is to be computed.
(G) In cases of additional loss in visual
efficiency when it is known by the examining physician that there was present a
pre-existing subnormal vision, compensable disability shall be based on the
loss incurred as a result of eye injury or occupational condition specifically
responsible for the additional loss. In cases in which there exists no record
or no adequate and positive evidence of preexisting subnormal vision, it shall
be assumed that the visual efficiency prior to any injury was one hundred
percent (100%) or at least equal to the visual efficiency of the uninjured eye.
TABLE NO. 3
TYPES OF OCULAR INJURY NOT INCLUDED IN THE DISTURBANCE
OF COORDINATE FACTORS
(The percentages are for unilateral losses unless otherwise
noted)
|
Disability
|
Approximate Rating Not to Exceed
|
|
Traumatic Cataract:
|
|
|
When a traumatic cataract has been successfully
treated by surgical or medical methods, the best visual acuity for that eye
with ophthalmic lenses shall be measured. Fifty percent (50%) of this best
visual acuity efficiency with an ophthalmic lens shall represent the central
visual acuity efficiency of the eye for rating purposes.
|
|
Dislocation of Lens-Traumatic:
|
|
|
Partial-Withhold rating for 12 months; then rate as
visual loss plus 50% (not to exceed 100%).
|
|
Total-The loss shall be 100% unless the lens has
been successfully removed by surgery or has been absorbed. When the lens has
been successfully removed by surgery or has been absorbed, the eye shall be
rated as an eye where a traumatic cataract has been removed. See: "Traumatic
Cataract" preceding.
|
|
Ptosis
|
|
Loss is visual efficiency Loss
|
|
Iridectomy-Traumatic or surgical
resulting
|
With photophobia or dazzling
|
30%
|
|
Scotoma-Traumatic
|
If not centrally located
|
10%
|
|
Paralysis of Accommodation
|
Unilateral
*Bilateral
|
20%
See footnote
|
|
Eye Brow (complete loss of)
|
Unilateral
*Bilateral
|
10%
See footnote
|
|
Eye Lashes (complete loss of)
|
Unilateral
*Bilateral
|
10%
See footnote
|
|
Symble-pharon (also limited muscle
function)
|
Unilateral
*Bilateral
|
10%
See footnote
|
|
Ectropion or Entropion
|
Unilateral
*Bilateral
|
10%
See footnote
|
|
Lagophthalmus
*Bilateral
|
Unilateral
See footnote
|
10%
|
|
Epiphora
*Bilateral
|
Unilateral
See footnote
|
10%
|
* In the event of bilateral disabilities due to paralysis of
accommodation, loss of eye brows, loss of eye lashes, symblepharon, ectropion,
entripion, lagophthalmus or epiphora, the percentage of unilateral loss in the
poorer eye shall be taken of 140 weeks and to that shall be added the
percentage of unilateral loss in the better eye taken of 260 weeks. (See
section (9) for computation of binocular visual efficiency).
(10) When an employee, who has a
permanent partial visual disability whether from a compensable injury or
otherwise, subsequently receives a compensable injury resulting in additional
permanent partial visual disability, the examining doctor shall then determine,
as nearly as possible, the permanent disability caused by the last injury and
set forth that percentage loss in his/her report. The employer is liable only
for the visual loss due to the second injury, taken alone, and the Second
Injury Fund is liable for additional disability if it is in excess of the mere
sum of all the disabilities.
(11)
In each case of eye injury resulting in any degree of permanent disability, the
employer and insurer shall file Form 9-A, Physician's Report on Eye Injuries,
completed in all the detail the form asks for, as promptly as possible. If the
Form 9-A shows final estimation of the visual disabilities, it may be used as a
basis for computing the compensation due the injured worker.
Notes
8 CSR 50-5.020
AUTHORITY:
section 287.650, RSMo 1986.* Original
rule filed Dec. 23, 1953, effective Jan. 3, 1954. Amended: Filed Nov. 1, 1956,
effective Nov. 12, 1956. Amended: Filed June 19, 1958, effective June 30, 1958.
Amended: Filed Sept. 4, 1963, effective Sept. 15,
1963.
AUTHORITY: section
287.650, RSMo 1986.* Original
rule filed Dec. 23, 1953, effective Jan. 3, 1954. Amended: Filed Nov. 1, 1956,
effective Nov. 12, 1956. Amended: Filed June 19, 1958, effective June 30, 1958.
Amended: Filed Sept. 4, 1963, effective Sept. 15, 1963.
