Table of Contents

Locator Record

Title: Vision (VIX )
Contact Number: 1-866-441-NCHS
Years of Content: 1999 - 2000
First Published: June, 2002
Revised: February, 2005
Access Constraints: None
Use Constraints: None
Geographic Coverage: National
Subject:Vision
Record Source: NHANES 1999 - 2000
Survey Methodology: NHANES 1999 - 2000 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.

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

Examination Protocol

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 was recorded prior to measuring their presenting distance visual acuity.

Survey 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 2 2
2 No 6450 6452 VIQ130
. Missing 306 6758

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 1 1 End of Section
2 Left 0 1 End of Section
3 Both 1 2 End of Section
. Missing 6756 6758

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 6450 6450 VIQ150
. Missing 308 6758

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 6758 6758

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 1743 1743
2 No 269 2012 VIXNC1
9 Don't know 2 2014
. Missing 4744 6758

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 1551 1551
2 No 192 1743 VIXNC1
. Missing 5015 6758

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 1529 1529
2 Contacts 14 1543
3 Both glasses and contact lenses 8 1551
. Missing 5207 6758

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 1989 1989
8 Could not obtain 25 2014
. Missing 4744 6758

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
5 to 34 Range of Values 1996 1996
88 Could not obtain 18 2014
. Missing 4744 6758

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 51 51
2 No 6378 6429 VIQ200
9 Don't know 9 6438 VIQ200
. Missing 320 6758

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 7 7
2 Left 5 12
3 Both 39 51
. Missing 6707 6758

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 338 338
2 No 6093 6431 VIQ220
9 Don't know 7 6438 VIQ220
. Missing 320 6758

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 55 55
2 Left 55 110
3 Both 225 335
9 Don't know 3 338
. Missing 6420 6758

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 2607 2607
2 No 3827 6434 VIXOCMT
9 Don't know 4 6438
. Missing 320 6758

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 2238 2238
2 No 369 2607
. Missing 4151 6758

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 1904 1904
2 Contacts 263 2167 VIXOCMT
3 Both glasses and contact lenses 71 2238
. Missing 4520 6758

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 1956 1956
2 No 8 1964
. Missing 4794 6758

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
-14.25 to 12.75 Range of Values 1919 1919
88 Could not obtain 46 1965
. Missing 4793 6758

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 6.75 Range of Values 1919 1919
88 Could not obtain 46 1965
. Missing 4793 6758

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 1919 1919
888 Could not obtain 46 1965
. Missing 4793 6758

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
-14.75 to 12.5 Range of Values 1920 1920
88 Could not obtain 45 1965
. Missing 4793 6758

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 10.5 Range of Values 1920 1920
88 Could not obtain 45 1965
. Missing 4793 6758

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 1920 1920
888 Could not obtain 45 1965
. Missing 4793 6758

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 2 2
2 Cataract contact lenses worn for objective refraction 7 9
3 Contacts worn for objective refraction 0 9
4 Artificial eye 3 12
5 Monovision contacts worn for objective refraction 1 13
6 Contact in right eye only for presenting visual acuity 1 14
7 Contact in left eye only for presenting visual acuity 3 17
. Missing 6741 6758

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
-22.5 to 20.5 Range of Values 6256 6256
88 Could not obtain 144 6400
. Missing 358 6758

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 8 Range of Values 6256 6256
88 Could not obtain 144 6400
. Missing 358 6758

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 6256 6256
888 Could not obtain 144 6400
. Missing 358 6758

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 6266 6266
. Missing 492 6758

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
-22.5 to 11 Range of Values 6235 6235
88 Could not obtain 165 6400
. Missing 358 6758

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 7.5 Range of Values 6235 6235
88 Could not obtain 165 6400
. Missing 358 6758

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 6235 6235
888 Could not obtain 165 6400
. Missing 358 6758

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 6285 6285
. Missing 473 6758

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
5.5 to 9.8 Range of Values 6339 6339
88 Could not obtain 61 6400
. Missing 358 6758

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
34.5 to 61.25 Range of Values 6339 6339
88 Could not obtain 61 6400
. Missing 358 6758

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 6339 6339
888 Could not obtain 61 6400
. Missing 358 6758

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
5.29 to 9.11 Range of Values 6339 6339
88 Could not obtain 61 6400
. Missing 358 6758

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
37 to 63.75 Range of Values 6339 6339
88 Could not obtain 61 6400
. Missing 358 6758

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 180 Range of Values 6339 6339
888 Could not obtain 61 6400
. Missing 358 6758

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
5.48 to 9.23 Range of Values 6339 6339
88 Could not obtain 61 6400
. Missing 358 6758

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
36.5 to 61.5 Range of Values 6339 6339
88 Could not obtain 61 6400
. Missing 358 6758

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
-4.5 to 24.5 Range of Values 6339 6339
88 Could not obtain 61 6400
. Missing 358 6758

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 180 Range of Values 6339 6339
888 Could not obtain 61 6400
. Missing 358 6758

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
5.45 to 10.09 Range of Values 6346 6346
88 Could not obtain 54 6400
. Missing 358 6758

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
33.5 to 62 Range of Values 6346 6346
88 Could not obtain 54 6400
. Missing 358 6758

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 6346 6346
888 Could not obtain 54 6400
. Missing 358 6758

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
5.1 to 9.42 Range of Values 6346 6346
88 Could not obtain 54 6400
. Missing 358 6758

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
35.75 to 66.25 Range of Values 6346 6346
88 Could not obtain 54 6400
. Missing 358 6758

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 180 Range of Values 6346 6346
888 Could not obtain 54 6400
. Missing 358 6758

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
5.41 to 9.68 Range of Values 6346 6346
88 Could not obtain 54 6400
. Missing 358 6758

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
34.75 to 62.5 Range of Values 6346 6346
88 Could not obtain 54 6400
. Missing 358 6758

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
-4.75 to 23.5 Range of Values 6346 6346
88 Could not obtain 54 6400
. Missing 358 6758

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 180 Range of Values 6346 6346
888 Could not obtain 54 6400
. Missing 358 6758

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 2928 2928
25 20/25 1552 4480
30 20/30 533 5013
40 20/40 294 5307
50 20/50 601 5908
60 20/60 96 6004
80 20/80 103 6107
200 20/200 140 6247
666 20/200+ 109 6356
888 Could not obtain 0 6356
. Missing 402 6758

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 2952 2952
25 20/25 1525 4477
30 20/30 553 5030
40 20/40 294 5324
50 20/50 611 5935
60 20/60 82 6017
80 20/80 106 6123
200 20/200 127 6250
666 20/200+ 112 6362
888 Could not obtain 0 6362
. Missing 396 6758

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 1315 1315
30 20/30 93 1408
40 20/40 76 1484
50 20/50 187 1671
60 20/60 14 1685
80 20/80 21 1706
200 20/200 47 1753
666 20/200+ 43 1796
888 Could not obtain 0 1796
. Missing 4962 6758

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 1317 1317
30 20/30 108 1425
40 20/40 77 1502
50 20/50 195 1697
60 20/60 14 1711
80 20/80 24 1735
200 20/200 45 1780
666 20/200+ 34 1814
888 Could not obtain 0 1814
. Missing 4944 6758