SSR 07-01p: Titles II and XVI: Evaluating Visual Field Loss Using Automated Static Threshold Perimetry

Effective/Publication Date: 07/31/2007 Federal Register Vol. 72, No. 146, page 41796

POLICY INTERPRETATION RULING

PURPOSE:

To clarify how we use automated static threshold

perimetry to evaluate visual field loss.

CITATIONS (AUTHORITY):

Sections 205(a) , 216(i)(1) , 221 , 223(d) , 1614(a) , 1631(d) , and 1633 of the Social Security Act (Act), as

amended; Regulations No. 4, subpart P, sections 404.1520 , 404.1525 , 404.1526 , 404.1581 ,

and 2.00A, 2.03, 102.00A, and 102.03 of appendix 1 ; and

Regulations No.16, subpart I, sections 416.920 , 416.924 , 416.925 , 416.926 , and 416.981 .

PERTINENT HISTORY:

The Act provides for a finding of blindness based on

visual field loss when the widest diameter of the visual

field in the better eye subtends an angle no greater than

20 degrees. Even when visual field loss does not result in

blindness, it may nevertheless be disabling. In sections

2.00A6 and 102.00A6 of the Listing of Impairments in

appendix 1 to subpart P of part 404 (the listings) we

provide that when we need to measure the extent of visual

field loss, we will use visual field measurements obtained

with an automated static threshold perimetry test that

satisfies our requirements. [1]

Automated static threshold perimetry measures the

retina's sensitivity to light at predetermined locations in

the visual field. While the individual focuses on a

specific point, called the point of fixation , stimuli are

presented in random order at each of the predetermined

locations within the visual field. The size of the stimulus

and the locations tested remain constant, but the intensity

(brightness) of the stimulus is varied in order to

determine the level at which the individual sees the

stimulus. The intensity level where the individual sees the

stimulus is referred to as the threshold . The threshold for

each point tested is reported in decibels (dB).

ermined

locations within the visual field. The size of the stimulus

and the locations tested remain constant, but the intensity

(brightness) of the stimulus is varied in order to

determine the level at which the individual sees the

stimulus. The intensity level where the individual sees the

stimulus is referred to as the threshold . The threshold for

each point tested is reported in decibels (dB).

The results of automated static threshold perimetry

are reported on standard charts. (See Exhibits 1 and 2 at

the end of this ruling for examples of standard charts that

may be found in case records.) These charts:

- Identify the perimeter that was used to perform the

test;

- Provide identifying information about the test, such

as the date of the test, the type of test used, the size

and color of the stimulus, and the background illumination;

- Provide the mean deviation (MD); [2] and

- Contain a printout that shows the threshold, in dB,

for each of the locations tested. We refer to this

printout, examples of which are shown below, as the dB

printout.

Identify the perimeter that was used to perform the

test;

Provide identifying information about the test, such

as the date of the test, the type of test used, the size

and color of the stimulus, and the background illumination;

Provide the mean deviation (MD); [2] and

Contain a printout that shows the threshold, in dB,

for each of the locations tested. We refer to this

printout, examples of which are shown below, as the dB

printout.

In this Ruling we explain:

- How to use the information in the standard charts

produced as part of automated static threshold perimetry to

determine whether the visual field test satisfies our

requirements. To illustrate this, we refer to standard

charts produced by the Humphrey Field Analyzer. We refer

only to the Humphrey Field Analyzer because it is the

perimeter most widely used in the United States.

- How to use the MD to determine whether the

individual has visual field loss.

as part of automated static threshold perimetry to

determine whether the visual field test satisfies our

requirements. To illustrate this, we refer to standard

charts produced by the Humphrey Field Analyzer. We refer

only to the Humphrey Field Analyzer because it is the

perimeter most widely used in the United States.

- How to use the MD to determine whether the

individual has visual field loss.

- Our process for determining whether the test results show

statutory blindness based on visual field

loss. [3]

- How to evaluate cases in which severe visual field

loss has not resulted in statutory blindness.

How to use the information in the standard charts

produced as part of automated static threshold perimetry to

determine whether the visual field test satisfies our

requirements. To illustrate this, we refer to standard

charts produced by the Humphrey Field Analyzer. We refer

only to the Humphrey Field Analyzer because it is the

perimeter most widely used in the United States.

How to use the MD to determine whether the

individual has visual field loss.

Our process for determining whether the test results show

statutory blindness based on visual field

loss. [3]

How to evaluate cases in which severe visual field

loss has not resulted in statutory blindness.

POLICY INTERPRETATION:

We use the following process to evaluate automated

static threshold perimetry.

Step 1—Is the automated static threshold perimetry test

acceptable?

We consider an automated static threshold perimetry

test to be acceptable when it meets all of the following

requirements:

- The test is performed on a perimeter that satisfies

all of the requirements in sections 2.00A6a(ii) and

102.00A6a(ii) of the listings; [4]

- The test uses a white size III Goldmann stimulus and

a 31.5 apostilb (asb) [5] (10 candela (cd)/m²) white

background; [6]

- The points tested are no more than 6 degrees apart

horizontally or vertically; and

en it meets all of the following

requirements:

- The test is performed on a perimeter that satisfies

all of the requirements in sections 2.00A6a(ii) and

102.00A6a(ii) of the listings; [4]

- The test uses a white size III Goldmann stimulus and

a 31.5 apostilb (asb) [5] (10 candela (cd)/m²) white

background; [6]

- The points tested are no more than 6 degrees apart

horizontally or vertically; and

- The test measures the central 24 to 30 degrees of

the visual field; that is, the area measuring 24 to 30

degrees around the point of fixation.

The test is performed on a perimeter that satisfies

all of the requirements in sections 2.00A6a(ii) and

102.00A6a(ii) of the listings; [4]

The test uses a white size III Goldmann stimulus and

a 31.5 apostilb (asb) [5] (10 candela (cd)/m²) white

background; [6]

The points tested are no more than 6 degrees apart

horizontally or vertically; and

The test measures the central 24 to 30 degrees of

the visual field; that is, the area measuring 24 to 30

degrees around the point of fixation.

The Humphrey Field Analyzer central 30-2 threshold

test (HFA 30-2) and central 24-2 threshold test (HFA 24-2)

are tests that can meet these criteria. The HFA 30-2 tests

76 points in the central 30 degrees of the visual field.

The HFA 24-2 tests 54 points in the central 24 to 30

degrees of the visual field. For both of these tests, the

tested points are spaced in an equidistant grid pattern,

with each point 6 degrees apart horizontally or vertically

from any adjacent point. Therefore, we consider the HFA 30-2

and the HFA 24-2 to be acceptable tests when performed

using a size III white stimulus on a 31.5 asb white

background.

The following examples of dB printouts illustrate the

grid patterns used for the HFA 30-2 and the HFA 24-2 and

provide information for interpreting the test results.

Example 1—An HFA 30-2 dB printout for the right eye

Example 2—An HFA 30-2 dB printout for the left eye

Example 3—An HFA 24-2 dB printout for the right eye

n performed

using a size III white stimulus on a 31.5 asb white

background.

The following examples of dB printouts illustrate the

grid patterns used for the HFA 30-2 and the HFA 24-2 and

provide information for interpreting the test results.

Example 1—An HFA 30-2 dB printout for the right eye

Example 2—An HFA 30-2 dB printout for the left eye

Example 3—An HFA 24-2 dB printout for the right eye

Example 4—An HFA 24-2 dB printout for the left eye

We will not use automated static threshold perimetry

test results to evaluate the visual field loss if the test

was not performed using all of our requirements; for

example, a stimulus other than a size III stimulus was

used, or the stimulus was not white.

Step 2—Are the test results reliable?

Each perimeter manufacturer will identify factors that

are used to determine whether the test results are

reliable.

For the Humphrey Field Analyzer, the reliability

factors are fixation losses , false positive errors , and false negative errors . Information about these factors is

at the top of the chart (see Exhibits 1 and 2). The test

results are not reliable for evaluating visual field loss

if the fixation losses exceed 20 percent, or if the false

positive errors or false negative errors exceed 33 percent.

Even when the reliability factors are within the

manufacturer's specifications, we will not use the test

results to evaluate visual field loss if there is other

information in the case file that suggests that the results

are not valid; for example, the test results are

inconsistent with the clinical findings or the individual's

daily activities.

Step 3—Does the individual have visual field loss?

For acceptable tests performed on a Humphrey Field

Analyzer, an MD equal to or greater than -5 dB (for

example, -4.39, -2.58, or 0) indicates that the visual

field is normal. An MD less than -5 dB (for example, -5.5,

-8.85, or -11.18) indicates the individual has visual field

loss.

Step 4—Do the test results show statutory blindness based

on visual field loss?

individual have visual field loss?

For acceptable tests performed on a Humphrey Field

Analyzer, an MD equal to or greater than -5 dB (for

example, -4.39, -2.58, or 0) indicates that the visual

field is normal. An MD less than -5 dB (for example, -5.5,

-8.85, or -11.18) indicates the individual has visual field

loss.

Step 4—Do the test results show statutory blindness based

on visual field loss?

In automated static threshold perimetry, the intensity

of the stimulus varies. We measure the extent of visual

field loss by determining the portion of the visual field

in which the individual can see a white III4e stimulus. The

“III” refers to the standard Goldmann test stimulus size

III. The “4e” refers to the standard Goldmann filters used

to determine the intensity of the stimulus. Therefore, a

determination is needed as to the dB threshold level that

corresponds to a 4e intensity for the particular perimeter

being used. Points that are at this dB threshold level or

above are considered seeing points because they are the

same intensity or dimmer than a 4e stimulus. Points that

are below this dB threshold level are considered non-seeing

points because they are brighter than a 4e stimulus.

For acceptable tests performed on a Humphrey Field

Analyzer, a 10 dB threshold is equivalent to a 4e

intensity. Therefore, for these tests we consider any point

with a threshold of 10 dB or higher to be a seeing point;

we consider any point with a threshold of less than 10 dB

to be a non-seeing point (see sections 2.00A6a(vii) and

102.00A6a(vii) of the listings).

After we determine the dB threshold that is comparable

to a 4e stimulus, we use the dB printout to determine

whether the widest diameter of the field is less than or

equal to 20 degrees. The diameter must go through the point

of fixation.

seeing point;

we consider any point with a threshold of less than 10 dB

to be a non-seeing point (see sections 2.00A6a(vii) and

102.00A6a(vii) of the listings).

After we determine the dB threshold that is comparable

to a 4e stimulus, we use the dB printout to determine

whether the widest diameter of the field is less than or

equal to 20 degrees. The diameter must go through the point

of fixation.

To determine whether the widest diameter is greater

than 20 degrees, we may map the visual field on a copy of

the dB printout by drawing a line, which we refer to as a pseudoisopter , midway between the seeing and non-seeing

points. [7] For example, for acceptable tests performed on a

Humphrey Field Analyzer, we draw the pseudoisopter between

any two adjacent tested points when one threshold is 10 dB

or greater and the other threshold is less than 10 dB. If

any number at the outermost edge of the field is a seeing

point, we draw the pseudoisopter on the edge of the field

at that point. If more than one number is shown for a

particular point, we use the higher number to determine

whether the point is a seeing point. We include the map of

the visual field in the case record.

The pseudoisopter(s) differentiates the seeing area of

the visual field from the non-seeing area. We consider the

pseudoisopter itself to be part of the seeing area.

We determine whether the widest diameter is greater

than 20 degrees by using the hash marks on the horizontal

(x-) and vertical (y-) axes of the Humphrey Field Analyzer

dB printout or by calculating the distance between the

points. As shown above, for the HFA 30-2 and the HFA 24-2,

each hash mark covers a distance of 10 degrees, and the

degrees are divided evenly between the hash marks.

Additionally, each tested point on a dB printout from an

HFA 30-2 or an HFA 24-2 is 6 degrees apart horizontally or

vertically from any adjacent tested point. The four tested

points immediately surrounding the point of fixation are

each 3 degrees horizontally and vertically from the point

of fixation

h mark covers a distance of 10 degrees, and the

degrees are divided evenly between the hash marks.

Additionally, each tested point on a dB printout from an

HFA 30-2 or an HFA 24-2 is 6 degrees apart horizontally or

vertically from any adjacent tested point. The four tested

points immediately surrounding the point of fixation are

each 3 degrees horizontally and vertically from the point

of fixation. Any tested point adjacent to an axis is 3

degrees from that axis.

When we measure the widest diameter of the visual

field, we subtract the length of any scotoma (non-seeing

area), other than the “normal” blind

spot, [8] from the overall

length of any diameter on which it falls. (On some Humphrey

Field Analyzer dB printouts, the normal blind spot is

identified by a small triangle, as shown in Example 1.) As

previously noted, we consider the pseudoisopter to be a

seeing area and do not subtract it from the overall length

of the diameter.

We will determine that the individual has statutory

blindness if the widest diameter in the better eye is less

than or equal to 20 degrees, this finding is consistent

with the other evidence in the case record, and for title

II, a medically determinable impairment that could result

in the visual field loss has been identified.

Examples of how we determine whether the individual has

statutory blindness based on visual field loss.

Example 5—An HFA 30-2 dB printout for the right eye

To measure the widest diameter, we create a

pseudoisopter by drawing a line midway between points with

a threshold of 10 dB and higher and adjacent points with a

threshold less than 10 dB, or by drawing the pseudoisopter

on the edge of the tested area when the thresholds at the

outermost points are 10 dB or higher. As all of the

outermost points on the dB printout above are 10 dB or

higher, we draw the pseudoisopter delineating the outer

edge of the visual field around the tested area.

points with

a threshold of 10 dB and higher and adjacent points with a

threshold less than 10 dB, or by drawing the pseudoisopter

on the edge of the tested area when the thresholds at the

outermost points are 10 dB or higher. As all of the

outermost points on the dB printout above are 10 dB or

higher, we draw the pseudoisopter delineating the outer

edge of the visual field around the tested area.

After determining the outer edge of the seeing area as

shown on the dB printout, we need to determine whether

there are any scotomata; that is, blind spots. If so, we

map the scotomata as we do not consider them when we

determine whether the widest diameter of the visual field

is greater than 20 degrees. A scotoma is illustrated below.

As all of the thresholds in the lower left quadrant of

this dB printout are higher than 10 dB, we consider this

entire quadrant to be a seeing area. Any diameter that is

drawn through this quadrant will be at least 30 degrees

long. Therefore, without calculating the actual length of

the widest diameter shown on the dB printout, we can

determine that the widest diameter of this visual field

must be greater than 20 degrees and that this individual

does not have statutory blindness based on visual field loss.

Although we did not need to calculate the widest

diameter for this example, the widest diameter shown on

this dB printout is 54 degrees on both axes. On the y-axis,

the diameter extends from the top of the dB printout to the

bottom of the dB printout, which is 60 degrees in length.

However, there is a segment of the y-axis that is in the

scotoma, the segment from 6 degrees to 12

degrees. [9] This

segment is 6 degrees long (calculated on the y-axis by

adding the 3 degrees above the non-seeing point to the 3

degrees below it). We subtract the 6 degrees from the 60

degrees for a total diameter of 54 degrees.

tout to the

bottom of the dB printout, which is 60 degrees in length.

However, there is a segment of the y-axis that is in the

scotoma, the segment from 6 degrees to 12

degrees. [9] This

segment is 6 degrees long (calculated on the y-axis by

adding the 3 degrees above the non-seeing point to the 3

degrees below it). We subtract the 6 degrees from the 60

degrees for a total diameter of 54 degrees.

On the x-axis, the diameter extends from one side of

the dB printout to the other side of the dB printout, which

is 60 degrees in length. However, there is a segment of the

x-axis that is in the scotoma, the segment from 12 degrees

to 18 degrees. [10] This segment is 6 degrees long. We subtract

the 6 degrees from the 60 degrees for a diameter of 54

degrees.

Example 6—An HFA 30-2 dB printout for the left eye

To measure the widest diameter, we create a

pseudoisopter by drawing a line midway between points with

a threshold of 10 dB and higher and adjacent points with a

threshold less than 10 dB.

The widest diameter is 24 degrees on the y-axis. We

can determine that the individual does not have statutory

blindness based on visual field loss because the widest

diameter is greater than 20 degrees.

Example 7—An HFA 24-2 dB printout for the right eye

To measure the widest diameter, we create a

pseudoisopter by drawing a line midway between points with

a threshold of 10 dB or higher and adjacent points with a

threshold less than 10 dB.

The widest diameter is shown below.

The widest diameter is on a diagonal; therefore, we calculate its length

as the hypotenuse of a right

triangle. [11] The widest diameter extends from the point in the field that is 6

degrees above and 12 degrees to the left of the point of fixation,

through the point of fixation, to the point in the field that is 3

degrees below and 6 degrees to the right of the point of fixation.

These two points are 9 degrees apart vertically and 18 degrees apart

horizontally, as shown below.

18 degrees

9 degrees

angle. [11] The widest diameter extends from the point in the field that is 6

degrees above and 12 degrees to the left of the point of fixation,

through the point of fixation, to the point in the field that is 3

degrees below and 6 degrees to the right of the point of fixation.

These two points are 9 degrees apart vertically and 18 degrees apart

horizontally, as shown below.

18 degrees

9 degrees

To measure the widest diameter, we apply the formula

for calculating the length of the hypotenuse of a right

triangle as follows: 9² + 18² = 81 + 324 = 405. The widest

diameter is the square root of 405, or 20.12 degrees, which

we round to 20 degrees. [12] Assuming that this is the individual's better eye, that the field shown

is consistent with the other evidence in file, and for a title II claim,

that there is a medically determinable impairment that could cause this

field loss, we will find that the individual has statutory blindness.

Step 5—How do we evaluate severe visual field loss that has

not resulted in statutory blindness?

If the individual's visual disorder has resulted in severe visual field

loss but has not resulted in statutory blindness, we will consider

whether the visual disorder meets listing 2.03B or 102.03B. A visual

disorder meets listing 2.03B or 102.03B when the MD for the better eye,

measured with an HFA 30-2, is -22 dB or

worse. [13] If the visual

disorder does not meet a listing, we will determine whether the visual

disorder medically equals a listing or, if not, assess the limitations

imposed by the visual disorder.

Exhibit 1—Standard Chart from an HFA 30-2

Exhibit 2—Standard Chart from an HFA 24-2

EFFECTIVE DATE:

This Ruling is effective upon publication in the Federal Register .

CROSS-REFERENCES:

Program Operations Manual System DI 34001.012 and DI

34005.102; Special Senses and Speech – Adult, Program

Policy Online 104167188, Special Senses and Speech – Child,

Program Policy Online 734761857.

isorder.

Exhibit 1—Standard Chart from an HFA 30-2

Exhibit 2—Standard Chart from an HFA 24-2

EFFECTIVE DATE:

This Ruling is effective upon publication in the Federal Register .

CROSS-REFERENCES:

Program Operations Manual System DI 34001.012 and DI

34005.102; Special Senses and Speech – Adult, Program

Policy Online 104167188, Special Senses and Speech – Child,

Program Policy Online 734761857.

[1] Our rules provide that in addition to automated static threshold

perimetry we can use comparable visual field measurements obtained with

kinetic perimetry, such as Goldmann perimetry. Because we allow for

different types of testing, our listings provide comparable criteria

that can be used with the different types of test results. Accordingly,

only one type of testing is needed to evaluate visual field loss under

our listings.

[2] The MD represents the average elevation or depression of the

individual's visual field when compared to a normal field. This

measurement is expressed in dB.

[3] We developed our process to enable us to apply the results of automated

static threshold perimetry to the standard for statutory blindness.

Health care providers do not use our process in their clinical practices

or for treatment purposes.

[4] As of the effective date of this ruling, all models of the Humphrey

Field Analyzer satisfy these requirements.

[5] An apostilb is a unit of luminance.

[6] The background color is not shown on the standard charts produced by the

Humphrey Field Analyzer. However, as of the effective date of this

ruling, the Humphrey Field Analyzer always uses a white background if a

white stimulus is used.

s.

[4] As of the effective date of this ruling, all models of the Humphrey

Field Analyzer satisfy these requirements.

[5] An apostilb is a unit of luminance.

[6] The background color is not shown on the standard charts produced by the

Humphrey Field Analyzer. However, as of the effective date of this

ruling, the Humphrey Field Analyzer always uses a white background if a

white stimulus is used.

[7] A pseudoisopter is similar to an isopter drawn as part of kinetic visual

field testing. Drawing a pseudoisopter assists in determining the

location of the widest diameter of the visual field and whether that

diameter is 20 degrees or less. However, we do not always need to draw

a pseudoisopter to determine whether the widest diameter is 20 degrees

or less. For example, if the only seeing points on the dB printout are

the four locations around the point of fixation, we can determine that

the widest diameter of the visual field is less than 20 degrees without

drawing a pseudoisopter. If all the points in an entire quadrant of the

dB printout are seeing points, we can determine that the widest diameter

is greater than 20 degrees.

[8] The normal blind spot is usually located 15.5 degrees temporal to

fixation (to the right for the right eye, to the left for the left eye)

and 1.5 degrees below the horizontal meridian. It is approximately 5.5

degrees in width and 7.5 degrees in length.

[9] We would not deduct the segments of the y-axis from the point of

fixation to 6 degrees or from -6 to -12 degrees because those segments

are part of the pseudoisopter and we consider the pseudoisopter to be a

seeing area.

[10] This segment includes the “normal” blind spot, which is

usually not deducted from the visual field. However, because the area

around the “normal” blind spot is part of the non-seeing

area, the “normal” blind spot is no longer considered

“normal” and we include it as part of the scotoma.

ecause those segments

are part of the pseudoisopter and we consider the pseudoisopter to be a

seeing area.

[10] This segment includes the “normal” blind spot, which is

usually not deducted from the visual field. However, because the area

around the “normal” blind spot is part of the non-seeing

area, the “normal” blind spot is no longer considered

“normal” and we include it as part of the scotoma.

[11] The formula for calculating the length of the hypotenuse of a right

triangle is a² + b² = c², where a and b represent the

vertical and

horizontal distances between two points and c represents the diagonal

distance between two points.

[12] When determining the widest diameter of the visual field, follow the

normal rules for rounding to the nearest whole number; that is, round

decimals below 0.5 down to the lower whole number and round decimals 0.5

and above up to the higher whole number.

[13] An HFA 24-2 cannot be used to determine if the visual disorder meets or

medically equals listing 2.03B or 102.03B because the criterion in those

listings was calculated using an HFA 30-2. An MD calculated using an

HFA 24-2 cannot be substituted for an MD calculated using an HFA 30-2.