Table of Contents

Locator Record

Title: Vision (VIX_B )
Contact Number: 1-866-441-NCHS
Years of Content: 2001 - 2002
First Published: February, 2005
Revised: NA
Access Constraints: None
Use Constraints: None
Geographic Coverage: National
Subject:Vision
Record Source: NHANES 2001 - 2002
Survey Methodology: NHANES 2001 - 2002 is a stratified multistage probability sample of the civilian non-institutionalized population of the U.S.
Medium: NHANES Web site; SAS transport files

Component Description

The NHANES data will be used to:

  1. measure the prevalence of visual acuity impairment in the U.S. population (visual acuity worse than 20/40);
  2. measure the distribution of refractive error in the U.S. population; and
  3. evaluate functional impairment related to vision.

Eligible Sample

All sample persons aged 12+ years were eligible to participate in the refraction exam. The protocol included: measuring the eyeglass prescription in people who wore glasses for distance; testing the presenting distance visual acuity of sample persons with their usual correction (glasses/contacts or none); obtaining an objective refraction (incorporating also an evaluation of the corneal curvature of the eye); and, for sample persons whose presenting distance acuity was 20/30 or worse, distance visual acuity after objective refraction. In addition, a visual acuity at near was assessed only on persons 50 years and over.

Exclusion Criteria

Participants who were determined to be completely blind or unable to see in both eyes
as well as sample persons with a severe infection (i.e., purulent discharge with redness and inflammation) in one or both eyes were excluded from this exam.

Protocol and Procedure

The vision exam included measurements of:

  1. eyeglass prescription for glasses used to view distant objects,
  2. presenting visual acuity with current correction,
  3. objective refraction,
  4. visual acuity incorporating objective refraction, and
  5. near vision acuity.

Screening questions were asked of all participants age 12 years and older. If the sample person wore eyeglasses to see distant objects, current eyeglass prescription was determined using a lensmeter. Presenting visual acuity was tested with current correction, if any. Objective refraction and corneal curvature data were obtained by averaging three autoretinoscopy measurements. Visual acuity with objective refraction is assessed only on sample persons whose initial, presenting visual acuity was 20/30 or worse. For sample persons aged 50 years and older, near vision was tested with a near vision card and usual reading distance recorded prior to measuring their presenting distance visual acuity.

Protocol and Procedure

Staff

The MEC health technicians conducted the vision examination. These technicians received 8 weeks of training initially, and subsequently underwent updates and remedial training as needed. Technicians referred to the Vision Procedures Manual for specific instructions for the administration of this component.

Data Collection Forms

Two screening questions were completed by the health technician and involved observation of the subject to determine if the medical exclusion criteria apply. The sample person was then asked additional screening questions (e.g. do they wear any distance correction) to determine which measurements in the examination protocol were relevant.

Quality Assurance & Quality Control

A variety of quality control procedures were used to ensure the accurate and reliable collection of vision data. Calibrations of the lensmeter and the autorefractor were performed prior to conducting examinations at each survey location, and weekly thereafter. At regular intervals, NCHS and contractor staffs observed vision examinations conducted in the MEC to evaluate whether appropriate procedures and techniques were being followed. Retraining sessions were conducted with all MEC health technicians to review data collection procedures.

Data Processing and Editing

Automated data collection procedures for the survey were used to collect the vision data. Eyeglass prescription data were captured electronically by the lensmeter, and the objective refraction and visual acuity data were captured by the autorefractor. Both sets of data were then transferred to the survey database system. Visual acuity data values were also captured by the technician and entered directly into the database.

Analytic Notes

Users are encouraged to carefully note the English instructions describing the various variables in the codebook documentation.

Special Notes about this Dataset

This dataset only contains data for the vision examination conducted in the MEC. There is another dataset containing household interview responses to the vision section (VIQ) of the Sample Person Questionnaire. Data from the two datasets can be combined and analyzed using the guidelines provided by NCHS. Note that not all of the same persons appear in the household interview and MEC examination datasets.

References

Codebook and Frequencies

SEQN - Respondent sequence number

Variable Name:
SEQN
SAS Label:
Respondent sequence number
English Text:
Respondent sequence number
Target:
Both males and females 12 YEARS - 150 YEARS

VIQ110 - SP has a severe eye infection?

Variable Name:
VIQ110
SAS Label:
SP has a severe eye infection?
English Text:
Does SP appear to have a severe eye infection in one or both eyes?
English Instructions:
The examiner observes the examinee's eyes for possible infection. If either eye has a sign of infection, the examinee is excluded from the vision component.
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 Yes 3 3
2 No 7045 7048 VIQ130
. Missing 397 7445

VIQ121 - Which eye(s) infected?

Variable Name:
VIQ121
SAS Label:
Which eye(s) infected?
English Text:
if VIQ110 = "Yes" record which eye(s) is/are affected.
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 Right 0 0 End of Section
2 Left 2 2 End of Section
3 Both 1 3 End of Section
. Missing 7442 7445

VIQ130 - Is SP wearing an eye patch?

Variable Name:
VIQ130
SAS Label:
Is SP wearing an eye patch?
English Text:
Is SP wearing an eye patch?
English Instructions:
Although the SP is not excluded from the vision examination because he/she wears an eye patch, the examiner will not conduct the examination on the affected eye.
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 Yes 0 0
2 No 7045 7045 VIQ150
. Missing 400 7445

VIQ141 - Which eye has eye patch?

Variable Name:
VIQ141
SAS Label:
Which eye has eye patch?
English Text:
If VIQ130 = "Yes" record which eye(s) is/are affected.
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 Right 0 0
2 Left 0 0
3 Both 0 0
. Missing 7445 7445

VIQ150 - Glasses/contact lenses for near work?

Variable Name:
VIQ150
SAS Label:
Glasses/contact lenses for near work?
English Text:
Do you wear glasses or contact lenses for reading or near work?
Target:
Both males and females 50 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 Yes 1853 1853
2 No 276 2129 VIXNC1
9 Don't know 1 2130
. Missing 5315 7445

VIQ160 - Glasses/contact lenses available?

Variable Name:
VIQ160
SAS Label:
Glasses/contact lenses available?
English Text:
If VIQ150 = "Yes", record if the examinee brought their near work glasses, contacts, or a combination of glasses and/or contacts to the testing facility.
Target:
Both males and females 50 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 Yes 1642 1642
2 No 211 1853 VIXNC1
. Missing 5592 7445

VIQ170 - Glasses or contacts worn for near test?

Variable Name:
VIQ170
SAS Label:
Glasses or contacts worn for near test?
English Text:
If VIQ160 = "Yes", record whether the examinee wore glasses, contacts, or a combination of glasses and/or contacts for test of near vision.
Target:
Both males and females 50 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 Glasses 1621 1621
2 Contacts 15 1636
3 Both glasses and contact lenses 6 1642
. Missing 5803 7445

VIXNC1 - Line read on near card

Variable Name:
VIXNC1
SAS Label:
Line read on near card
English Text:
The number of the last line the examinee read with one or fewer misses, that is the number of the last line where the examinee read at least four out of the five characters correctly. Line 1 has the largest print: line 5 has the smallest print.
Target:
Both males and females 50 YEARS - 150 YEARS
Hard Edits:
0.0000 to 5.0000
Code or Value Value Description Count Cumulative Skip to Item
0 to 5 Range of Values 2126 2126
8 Could not obtain 4 2130
. Missing 5315 7445

VIXNC2 - Testing distance of near card

Variable Name:
VIXNC2
SAS Label:
Testing distance of near card
English Text:
Record to the nearest inch the distance from the center of the card to the examinee's brow.
English Instructions:
A measuring tape is used to determine the distance. (Rounding rule: Numbers less than 0.5, round down (example 16 1/4 = 16) and numbers equal to or greater than 0.5, round up (13 1/2 = 14, 21 3/4 = 22).)
Target:
Both males and females 50 YEARS - 150 YEARS
Hard Edits:
1.0000 to 36.0000
Code or Value Value Description Count Cumulative Skip to Item
1 to 33 Range of Values 2126 2126
88 Could not obtain 4 2130
. Missing 5315 7445

VIQ180 - Eye surgery for near sightedness?

Variable Name:
VIQ180
SAS Label:
Eye surgery for near sightedness?
English Text:
Have you ever had eye surgery to treat or prevent nearsightedness or myopia?
English Instructions:
The interest is in laser or radial keratotomy (RK) surgeries used to improve nearsightedness. Some other terms to describe this surgery include: PRK, RK, Lasik, Eximer, or Refractive Surgery.
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 Yes 78 78
2 No 6944 7022 VIQ200
9 Don't know 12 7034 VIQ200
. Missing 411 7445

VIQ191 - Which eye(s) surgery - near-sightedness?

Variable Name:
VIQ191
SAS Label:
Which eye(s) surgery - near-sightedness?
English Text:
If VIQ180 = "Yes", record which eye(s) was/were operated on.
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 Right 5 5
2 Left 5 10
3 Both 68 78
. Missing 7367 7445

VIQ200 - Eye surgery for cataracts?

Variable Name:
VIQ200
SAS Label:
Eye surgery for cataracts?
English Text:
Have you ever had eye surgery to treat cataracts?
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 Yes 381 381
2 No 6641 7022 VIQ220
9 Don't know 12 7034 VIQ220
. Missing 411 7445

VIQ211 - Which eye(s) cataract surgery?

Variable Name:
VIQ211
SAS Label:
Which eye(s) cataract surgery?
English Text:
if VIQ200 = "Yes", record which eye(s) was/were operated on for cataracts.
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 Right 64 64
2 Left 47 111
3 Both 268 379
9 Don't know 2 381
. Missing 7064 7445

VIQ220 - Glasses/contact lenses worn for distance

Variable Name:
VIQ220
SAS Label:
Glasses/contact lenses worn for distance
English Text:
Do you wear glasses or contact lenses for distance vision, such as when you watch television?
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 Yes 2980 2980
2 No 4049 7029 VIXOCMT
9 Don't know 5 7034
. Missing 411 7445

VIQ230 - Is distance correction available?

Variable Name:
VIQ230
SAS Label:
Is distance correction available?
English Text:
If VIQ220 = "Yes", record if examinee brought their distance correction to the testing center.
English Instructions:
The SP could be wearing the correction or brought it with them.
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 Yes 2570 2570
2 No 410 2980
. Missing 4465 7445

VIQ240 - Which type? Glasses or contacts?

Variable Name:
VIQ240
SAS Label:
Which type? Glasses or contacts?
English Text:
If VIQ230 = "Yes", record the type of correction (glasses, contacts, or a combination of glasses and contacts) the SP has with them.
English Instructions:
This specifies the type of correction worn by the SP for the presenting VA tests (VIDRVA and VIDLVA).
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 Glasses 2172 2172
2 Contacts 321 2493 VIXOCMT
3 Both glasses and contact lenses 77 2570
. Missing 4875 7445

VIQ250 - Was prescription obtained?

Variable Name:
VIQ250
SAS Label:
Was prescription obtained?
English Text:
Did the examiner capture the prescription of the examinee's lens?
English Instructions:
This pertains to the lens prescription used for viewing distant objects.
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 Yes 2241 2241
2 No 2 2243
. Missing 5202 7445

VIXPRS - Prescription, right sphere

Variable Name:
VIXPRS
SAS Label:
Prescription, right sphere
English Text:
The prescription of the sphere in the right lens used for distance correction.
English Instructions:
For distance eyeglasses only.
Target:
Both males and females 12 YEARS - 150 YEARS
Hard Edits:
-25.0000 to 25.0000
Code or Value Value Description Count Cumulative Skip to Item
-15 to 13.5 Range of Values 2204 2204
88 Could not obtain 39 2243
. Missing 5202 7445

VIXPRC - Prescription, right cylinder

Variable Name:
VIXPRC
SAS Label:
Prescription, right cylinder
English Text:
Prescription of the cylinder in the right lens used for distance correction
English Instructions:
For distance eyeglasses only
Target:
Both males and females 12 YEARS - 150 YEARS
Hard Edits:
-9.9900 to 9.9900
Code or Value Value Description Count Cumulative Skip to Item
0 to 8.5 Range of Values 2204 2204
88 Could not obtain 39 2243
. Missing 5202 7445

VIXPRA - Prescription, right axis

Variable Name:
VIXPRA
SAS Label:
Prescription, right axis
English Text:
Prescription of the axis in the right lens used for distance correction
English Instructions:
For distance eyeglasses only.
Target:
Both males and females 12 YEARS - 150 YEARS
Hard Edits:
0.0000 to 180.0000
Code or Value Value Description Count Cumulative Skip to Item
0 to 180 Range of Values 2204 2204
888 Could not obtain 39 2243
. Missing 5202 7445

VIXPLS - Prescription, left sphere

Variable Name:
VIXPLS
SAS Label:
Prescription, left sphere
English Text:
Prescription of the sphere in the left lens used for distance correction.
English Instructions:
For distance eyeglasses only.
Target:
Both males and females 12 YEARS - 150 YEARS
Hard Edits:
-25.0000 to 25.0000
Code or Value Value Description Count Cumulative Skip to Item
-15.5 to 14.5 Range of Values 2202 2202
88 Could not obtain 41 2243
. Missing 5202 7445

VIXPLC - Prescription, left cylinder

Variable Name:
VIXPLC
SAS Label:
Prescription, left cylinder
English Text:
Prescription of the cylinder in the left lens used for distance correction.
English Instructions:
For distance eyeglasses only.
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 to 9.25 Range of Values 2202 2202
88 Could not obtain 41 2243
. Missing 5202 7445

VIXPLA - Prescription, left axis

Variable Name:
VIXPLA
SAS Label:
Prescription, left axis
English Text:
Prescription of the axis in the left lens used for distance correction.
English Instructions:
For distance eyeglasses only
Target:
Both males and females 12 YEARS - 150 YEARS
Hard Edits:
0.0000 to 180.0000
Code or Value Value Description Count Cumulative Skip to Item
0 to 180 Range of Values 2202 2202
888 Could not obtain 41 2243
. Missing 5202 7445

VIXOCMT - Visual Acuity Comments

Variable Name:
VIXOCMT
SAS Label:
Visual Acuity Comments
English Text:
The examiner can note special circumstances related to a visual acuity test.
English Instructions:
These apply to distance vision tests.
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 Monovision glasses/contacts worn for visual acuity 9 9
2 Cataract contact lenses worn for objective refraction 2 11
3 Contacts worn for objective refraction 9 20
4 Artificial eye 7 27
5 Monovision contacts worn for objective refraction 2 29
6 Contact in right eye only for presenting visual acuity 2 31
7 Contact in left eye only for presenting visual acuity 2 33
. Missing 7412 7445

VIXORSM - OR right sphere, average

Variable Name:
VIXORSM
SAS Label:
OR right sphere, average
English Text:
Spherical dioptric power (averaging three objective refractions) of the examinee's right eye.
Target:
Both males and females 12 YEARS - 150 YEARS
Hard Edits:
-23.0000 to 23.0000
Code or Value Value Description Count Cumulative Skip to Item
-23 to 10.25 Range of Values 6845 6845
88 Could not obtain 166 7011
. Missing 434 7445

VIXORCM - OR right cylinder, average

Variable Name:
VIXORCM
SAS Label:
OR right cylinder, average
English Text:
Cylindrical dioptric power (averaging three objective refractions) of the examinee's right eye
Target:
Both males and females 12 YEARS - 150 YEARS
Hard Edits:
0 to 8
Code or Value Value Description Count Cumulative Skip to Item
0 to 7.75 Range of Values 6845 6845
88 Could not obtain 166 7011
. Missing 434 7445

VIXORAM - OR right axis, average

Variable Name:
VIXORAM
SAS Label:
OR right axis, average
English Text:
Axis of refractive astigmatism (averaging three objective refractions) of the examinee's right eye.
Target:
Both males and females 12 YEARS - 150 YEARS
Hard Edits:
0.0000 to 180.0000
Code or Value Value Description Count Cumulative Skip to Item
0 to 180 Range of Values 6846 6846
888 Could not obtain 165 7011
. Missing 434 7445

VIDORFM - OR right confidence level reading

Variable Name:
VIDORFM
SAS Label:
OR right confidence level reading
English Text:
The confidence level of the objective refraction reading for the right eye (mean of three measures).
English Instructions:
Lower values equate to less confidence in the objective refraction values.
Target:
Both males and females 12 YEARS - 150 YEARS
Hard Edits:
5.0000 to 9.0000
Code or Value Value Description Count Cumulative Skip to Item
5 to 9 Range of Values 6881 6881
. Missing 564 7445

VIXOLSM - OR left sphere, average

Variable Name:
VIXOLSM
SAS Label:
OR left sphere, average
English Text:
Spherical dioptric power (averaging three objective refractions) of the examinee's left eye
Target:
Both males and females 12 YEARS - 150 YEARS
Hard Edits:
-23.0000 to 23.0000
Code or Value Value Description Count Cumulative Skip to Item
-19.25 to 11.75 Range of Values 6787 6787
88 Could not obtain 224 7011
. Missing 434 7445

VIXOLCM - OR left cylinder, average

Variable Name:
VIXOLCM
SAS Label:
OR left cylinder, average
English Text:
Cylindrical dioptric power (averaging three objective refractions) of the examinee's left eye.
Target:
Both males and females 12 YEARS - 150 YEARS
Hard Edits:
0 to 8
Code or Value Value Description Count Cumulative Skip to Item
0 to 8 Range of Values 6787 6787
88 Could not obtain 224 7011
. Missing 434 7445

VIXOLAM - OR left axis, average

Variable Name:
VIXOLAM
SAS Label:
OR left axis, average
English Text:
Axis of refractive astigmatism (averaging three objective refractions) of the examinee's left eye.
Target:
Both males and females 12 YEARS - 150 YEARS
Hard Edits:
0.0000 to 180.0000
Code or Value Value Description Count Cumulative Skip to Item
0 to 180 Range of Values 6787 6787
888 Could not obtain 224 7011
. Missing 434 7445

VIDOLFM - OR left confidence level reading

Variable Name:
VIDOLFM
SAS Label:
OR left confidence level reading
English Text:
The confidence level of the objective refraction reading of the left eye (mean of three measures).
English Instructions:
Lower values equate to less confidence in the objective refraction values.
Target:
Both males and females 12 YEARS - 150 YEARS
Hard Edits:
5.0000 to 9.0000
Code or Value Value Description Count Cumulative Skip to Item
5 to 9 Range of Values 6867 6867
. Missing 578 7445

VIXKRM1 - Right keratometry radius flat curve (mm)

Variable Name:
VIXKRM1
SAS Label:
Right keratometry radius flat curve (mm)
English Text:
Keratometric measure. Radius of corneal curvature (in mm) in the least power meridian of the examinee's right eye.
Target:
Both males and females 12 YEARS - 150 YEARS
Hard Edits:
5.0000 to 10.0000
Code or Value Value Description Count Cumulative Skip to Item
6.51 to 9.68 Range of Values 6969 6969
88 Could not obtain 42 7011
. Missing 434 7445

VIXKRD1 - Right keratometry power flat curve (D)

Variable Name:
VIXKRD1
SAS Label:
Right keratometry power flat curve (D)
English Text:
Keratometric measure. Dioptric power in the least power meridian of the cornea in the examinee's right eye.
Target:
Both males and females 12 YEARS - 150 YEARS
Hard Edits:
33.7500 to 67.5000
Code or Value Value Description Count Cumulative Skip to Item
34.75 to 51.75 Range of Values 6969 6969
88 Could not obtain 42 7011
. Missing 434 7445

VIXKRG1 - Right keratometry axis flat curve (deg)

Variable Name:
VIXKRG1
SAS Label:
Right keratometry axis flat curve (deg)
English Text:
Keratometric measure. Axis of corneal astigmatism (in degrees) in the least power meridian of the examinee's right eye.
Target:
Both males and females 12 YEARS - 150 YEARS
Hard Edits:
0.0000 to 180.0000
Code or Value Value Description Count Cumulative Skip to Item
0 to 180 Range of Values 6969 6969
888 Could not obtain 42 7011
. Missing 434 7445

VIXKRM2 - Right keratometry radius steep curve(mm)

Variable Name:
VIXKRM2
SAS Label:
Right keratometry radius steep curve(mm)
English Text:
Keratometric measure. Radius of corneal curvature (in mm) in the greatest power meridian of the examinee's right eye
Target:
Both males and females 12 YEARS - 150 YEARS
Hard Edits:
5.0000 to 10.0000
Code or Value Value Description Count Cumulative Skip to Item
5.27 to 9.25 Range of Values 6969 6969
88 Could not obtain 42 7011
. Missing 434 7445

VIXKRD2 - Right keratometry power steep curve (D)

Variable Name:
VIXKRD2
SAS Label:
Right keratometry power steep curve (D)
English Text:
Keratometric measure. Dioptric power in the meridian of the cornea with the greatest power in the examinee's right eye.
Target:
Both males and females 12 YEARS - 150 YEARS
Hard Edits:
33.7500 to 67.5000
Code or Value Value Description Count Cumulative Skip to Item
36.5 to 64 Range of Values 6969 6969
88 Could not obtain 42 7011
. Missing 434 7445

VIXKRG2 - Right keratometry axis steep curve (deg)

Variable Name:
VIXKRG2
SAS Label:
Right keratometry axis steep curve (deg)
English Text:
Keratometric measure. Axis of corneal astigmatism (in degrees) in the greatest power meridian of the examinee's right eye.
Target:
Both males and females 12 YEARS - 150 YEARS
Hard Edits:
0.0000 to 180.0000
Code or Value Value Description Count Cumulative Skip to Item
0 to 179 Range of Values 6969 6969
888 Could not obtain 42 7011
. Missing 434 7445

VIXKRMM - Right keratometry radius, average (mm)

Variable Name:
VIXKRMM
SAS Label:
Right keratometry radius, average (mm)
English Text:
Keratometric measure. Radius of corneal curvature (in mm) averaged across meridians in the examinee's right eye.  
Target:
Both males and females 12 YEARS - 150 YEARS
Hard Edits:
5.0000 to 10.0000
Code or Value Value Description Count Cumulative Skip to Item
6.42 to 9.38 Range of Values 6969 6969
88 Could not obtain 42 7011
. Missing 434 7445

VIXKRDM - Right keratometry power, average (D) 

Variable Name:
VIXKRDM
SAS Label:
Right keratometry power, average (D) 
English Text:
Keratometric measure. Dioptric power of the cornea averaged across meridians in the examinee's right eye
Target:
Both males and females 12 YEARS - 150 YEARS
Hard Edits:
33.7500 to 67.5000
Code or Value Value Description Count Cumulative Skip to Item
36 to 52.5 Range of Values 6969 6969
88 Could not obtain 42 7011
. Missing 434 7445

VIXKRCD - Right keratometry cylinder 

Variable Name:
VIXKRCD
SAS Label:
Right keratometry cylinder 
English Text:
Keratometric measure. Difference in dioptric power between meridians of the cornea in the examinee's right eye
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 to 22.75 Range of Values 6969 6969
88 Could not obtain 42 7011
. Missing 434 7445

VIXKRCG - Right keratometry axis, average (deg)

Variable Name:
VIXKRCG
SAS Label:
Right keratometry axis, average (deg)
English Text:
Keratometric measure. Axis of corneal astigmatism (in degrees) in the steepest meridian of the cornea in the examinee's right eye.  
Target:
Both males and females 12 YEARS - 150 YEARS
Hard Edits:
0.0000 to 180.0000
Code or Value Value Description Count Cumulative Skip to Item
0 to 179 Range of Values 6969 6969
888 Could not obtain 42 7011
. Missing 434 7445

VIXKLM1 - Left keratometry radius flat curve (mm)

Variable Name:
VIXKLM1
SAS Label:
Left keratometry radius flat curve (mm)
English Text:
Keratometric measure. Radius of corneal curvature (in mm) in the least power meridian of the examinee's left eye.
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
6.41 to 9.7 Range of Values 6962 6962
88 Could not obtain 49 7011
. Missing 434 7445

VIXKLD1 - Left keratometry power flat curve (D)

Variable Name:
VIXKLD1
SAS Label:
Left keratometry power flat curve (D)
English Text:
Keratometric measure. Dioptric power in the least power meridian of the cornea in the examinee's left eye.
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
34.75 to 52.75 Range of Values 6962 6962
88 Could not obtain 49 7011
. Missing 434 7445

VIXKLG1 - Left keratometry axis flat curve (deg)

Variable Name:
VIXKLG1
SAS Label:
Left keratometry axis flat curve (deg)
English Text:
Keratometric measure. Axis of corneal astigmatism (in degrees) in the least power median of the examinee's left eye.
Target:
Both males and females 12 YEARS - 150 YEARS
Hard Edits:
0.0000 to 180.0000
Code or Value Value Description Count Cumulative Skip to Item
0 to 180 Range of Values 6962 6962
888 Could not obtain 49 7011
. Missing 434 7445

VIXKLM2 - Left keratometry radius steep curve (mm)

Variable Name:
VIXKLM2
SAS Label:
Left keratometry radius steep curve (mm)
English Text:
Keratometric measure. Radius of corneal curvature (in mm) in the greatest power meridian of the examinee's left eye.
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
4.98 to 9.19 Range of Values 6962 6962
88 Could not obtain 49 7011
. Missing 434 7445

VIXKLD2 - Left keratometry power steep curve (D)

Variable Name:
VIXKLD2
SAS Label:
Left keratometry power steep curve (D)
English Text:
Keratometric measure. Dioptric power in the meridian of the cornea with the greatest power in the examinee's left eye.
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
36.75 to 67.75 Range of Values 6962 6962
88 Could not obtain 49 7011
. Missing 434 7445

VIXKLG2 - Left keratometry axis steep curve (deg)

Variable Name:
VIXKLG2
SAS Label:
Left keratometry axis steep curve (deg)
English Text:
Keratometric measure. Axis of corneal astigmatism (in degrees) in the greatest power meridian of the examinee's left eye.
Target:
Both males and females 12 YEARS - 150 YEARS
Hard Edits:
0.0000 to 180.0000
Code or Value Value Description Count Cumulative Skip to Item
0 to 179 Range of Values 6962 6962
888 Could not obtain 49 7011
. Missing 434 7445

VIXKLMM - Left keratometry radius, average (mm) 

Variable Name:
VIXKLMM
SAS Label:
Left keratometry radius, average (mm) 
English Text:
Keratometric measure. Radius of corneal curvature (in mm) averaged across meridians in the examinee's left eye.
Target:
Both males and females 12 YEARS - 150 YEARS
Hard Edits:
5.0000 to 10.0000
Code or Value Value Description Count Cumulative Skip to Item
6.27 to 9.3 Range of Values 6962 6962
88 Could not obtain 49 7011
. Missing 434 7445

VIXKLDM - Left keratometry power, average (D) 

Variable Name:
VIXKLDM
SAS Label:
Left keratometry power, average (D) 
English Text:
Keratometric measure. Dioptric power of the cornea averaged across meridians in the examinee's left eye.
Target:
Both males and females 12 YEARS - 150 YEARS
Hard Edits:
33.7500 to 67.5000
Code or Value Value Description Count Cumulative Skip to Item
36.25 to 53.75 Range of Values 6962 6962
88 Could not obtain 49 7011
. Missing 434 7445

VIXKLCD - Left keratometry cylinder 

Variable Name:
VIXKLCD
SAS Label:
Left keratometry cylinder 
English Text:
Keratometric measure. Difference in dioptric power between meridians of the cornea in the examinee's left eye.
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 to 24.75 Range of Values 6962 6962
88 Could not obtain 49 7011
. Missing 434 7445

VIXKLCG - Left keratometry axis, average (deg)

Variable Name:
VIXKLCG
SAS Label:
Left keratometry axis, average (deg)
English Text:
Keratometric measure. Axis of corneal astigmatism (in degrees) in the steepest meridian of the cornea in the examinee's left eye.
Target:
Both males and females 12 YEARS - 150 YEARS
Hard Edits:
0.0000 to 180.0000
Code or Value Value Description Count Cumulative Skip to Item
0 to 179 Range of Values 6962 6962
888 Could not obtain 49 7011
. Missing 434 7445

VIDRVA - Right visual acuity, presenting

Variable Name:
VIDRVA
SAS Label:
Right visual acuity, presenting
English Text:
The presenting visual acuity of the right eye with usual correction.
English Instructions:
Usual correction could be: eyeglasses, contacts, eyeglasses and contacts, or no correction depending on what the SP wore (or brought with them) to view distant objects on the day they visited the MEC (see VIQ230 and VIQ240).
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
20 20/20 3241 3241
25 20/25 1717 4958
30 20/30 585 5543
40 20/40 348 5891
50 20/50 646 6537
60 20/60 88 6625
80 20/80 93 6718
200 20/200 168 6886
666 20/200+ 96 6982
888 Could not obtain 0 6982
. Missing 463 7445

VIDLVA - Left visual acuity, presenting

Variable Name:
VIDLVA
SAS Label:
Left visual acuity, presenting
English Text:
The presenting visual acuity of the left eye with usual correction.
English Instructions:
Usual correction could be: eyeglasses, contacts, eyeglasses and contacts, or no correction depending on what the SP wore (or brought with them) to view distant objects on the day they visited the MEC (see VIQ230 and VIQ240).
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
20 20/20 3322 3322
25 20/25 1598 4920
30 20/30 644 5564
40 20/40 278 5842
50 20/50 719 6561
60 20/60 79 6640
80 20/80 88 6728
200 20/200 164 6892
666 20/200+ 90 6982
888 Could not obtain 0 6982
. Missing 463 7445

VIDROVA - Right visual acuity, w/ obj. refraction

Variable Name:
VIDROVA
SAS Label:
Right visual acuity, w/ obj. refraction
English Text:
The visual acuity with objective refraction of the right eye.
English Instructions:
This is the visual acuity reported by the SP after the autorefractor inserted what it deemed, based on the objective refraction, to be the most appropriate lens (if any) to allow the eye to see 20/25 or better. This test was only performed on eyes whose presenting visual acuity was 20/30 or worse.
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
25 20/25 1429 1429
30 20/30 95 1524
40 20/40 108 1632
50 20/50 195 1827
60 20/60 14 1841
80 20/80 25 1866
200 20/200 48 1914
666 20/200+ 41 1955
888 Could not obtain 0 1955
. Missing 5490 7445

VIDLOVA - Left visual acuity, w/ obj. refraction

Variable Name:
VIDLOVA
SAS Label:
Left visual acuity, w/ obj. refraction
English Text:
The visual acuity with objective refraction of the left eye.
English Instructions:
This is the visual acuity reported by the SP after the autorefractor inserted what it deemed, based on the objective refraction, to be the most appropriate lens (if any) to allow the eye to see 20/25 or better. This test was only performed on eyes whose presenting visual acuity was 20/30 or worse.
Target:
Both males and females 12 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
25 20/25 1475 1475
30 20/30 89 1564
40 20/40 90 1654
50 20/50 198 1852
60 20/60 15 1867
80 20/80 25 1892
200 20/200 47 1939
666 20/200+ 44 1983
888 Could not obtain 0 1983
. Missing 5462 7445