Retinal Data Documentation

Data Information and Documentation

During the Year 10 visit retinal photographs were take on 2824 participants (2470 from the original CHS cohort and 354 from the African-American cohort). Photographs were taken of one eye, selected by the participant’s CHS identification number: right eye was chosen for even identification numbers and left eye for odd identification numbers. If the eye selected was unable to be photographed with adequate quality (e.g. missing eye, inability to dilate to at least 4 mm, inability to fixate adequately for proper photographic field definition, or media opacities preventing a reasonably clear view of the retina), the other eye was photographed. The data are contained in record 77 of the CHS database and values were obtained from light box grading and image analysis (see below for variable lists). Interview data collected at the time of the photograph are contained in record 74 of the database.

Light box grading variables

Photographic Quality

Focus
1 = Good
2 = Fair
3 = Borderline
4 = Inadequate
8 = Cannot grade

Field Definition
1 = Good
2 = Fair
3 = Poor
4 = Can’t grade

Haze (No/Yes)
Dust/Dirt (No/Yes)
Lashes (No/Yes)
Arc (No/Yes)
Uneven illum/macula (No/Yes)
Uneven illum/edge (No/Yes)
Uneven illum/disc zone (No/Yes)
Total blink (No/Yes)
Other artifact (No/Yes)
Disc obscured or missing (No/Yes)
Macula obscured or missing (No/Yes)

Gradability
1 = Gradable
2 = Impaired
3 = Ungradable

Arteriolar Changes

Disc Arterial Abnormalities
0 = None
1 = Questionable
2 = Definite, 1 or 2 vessels
3 = Severe, 3 or more vessels
8 = Cannot grade

Zone A Arterial Abnormalities
0 = None
1 = Questionable
2 = Definite, 1 or 2 vessels
3 = Severe, 3 or more vessels
8 = Cannot grade

Generalized Narrowing of Arterioles
0 = None
1 = Questionable
2 = Definite, 1 or 2 vessels
3 = Severe, 3 or more vessels
8 = Cannot grade

Focal Narrowing of Arterioles, Quadrants ST, SN, IN, IT
0 = None
1 = Questionable
2 = Mild, ½ DD total length
3 = Moderate, less than 2DD total length
4 = Severe, 2 or more DD total length
8 = Cannot grade

Sheathing of Arterioles, Quadrants ST, SN, IN, IT
0 = None
1 = Questionable
2 = Mild, less than ½ DD total length
3 = Moderate, less than 2DD total length
4 = Severe, 2 or more DD total length
8 = Cannot grade

Changes in A/V Crossings, Quadrants ST, SN, IN, IT
0 = None
1 = Questionable
2 = Definite, less than Std. 9
3 = Severe, 9 or more Std.
8 = Cannot grade

Lesions of Diabetic Retinopathy

Number of Microaneurysms
0 = None
1 = Questionable
2 = 1 Ma
3 = 2 Ma’s
4 = 3 Ma’s
5 = 4 Ma’s
6 = 5 or more Ma’s
8 = Cannot grade

Number of Retinal Hemorrhages
0 = None
1 = Questionable
2 = 1 RH
3 = 2 or more RH’s
8 = Cannot grade

Type of Retinal Hemorrhage
0 = None
1 = Questionable
2 = Flame hemorrhage only
3 = Blot hemorrhage only
4 = Blot and flame hemorrhages
8 = Cannot grade

Hemorrhages/Microaneurysms
0 = None
1 = Questionable
2 = Definite
3 = ³ Std. Photo #1 in all 4 quadrants
4 = ³ Std. Photo #2A
5 = ³ Std. Photo #2A in 2 or 3 quadrants
6 = ³ Std. Photo #2A in all 4 quadrants
8 = Cannot grade

Hard Exudate
0 = None
1 = Questionable
2 = Definite
8 = Cannot grade

Soft Exudate
0 = None
1 = Questionable
2 = Definite
8 = Cannot grade

IRMA (intraretinal microvascular abnormalities)
0 = None
1 = Questionable
2 = Definite
3 = Definite in all 4 quadrants
4 = ³ Std. Photo #8A
8 = Cannot grade

Venous Beading
0 = None
1 = Questionable
2 = Definite
3 = Definite in 2 or more quadrants
8 = Cannot grade

NVD (new vessels on the disc)
0 = None
1 = Questionable
2 = < Std. #10A
3 = ³ Std. #10A
8 = Cannot grade

NVE (new vessels elsewhere)
0 = None
1 = Questionable
2 = < ½ DA
3 = ³ ½ DA
8 = Cannot grade

VH/PRH (vitreous hemorrhage and/or preretinal hemorrhage)
0 = None
1 = Questionable
2 = < 1 DA
3 = ³ 1 DA
8 = Cannot grade

FP (fibroproliferants)
0 = None
1 = Questionable
2 = Definite
8 = Cannot grade

Macular Edema
0 = None
1 = Questionable
2 = Present, inferred from HE/other
3 = CSME, inferred from HE/other
4 = Center involved, inferred from HE/other
8 = Cannot grade

Laser Photocoagulation
0 = None
1 = Questionable
2 = Focal Rx only
3 = Scatter and/or local Rx
4 = Focal and scatter Rx
8 = Cannot grade

Diabetic Retinal Level

Retinal level is classified by 15 categories. Supporting evidence for the chosen classification was also recorded, indicated by code numbers. Up to five supporting evidence codes were possible, however no CHS participant had more than three recorded. The retinal levels and supporting evidence codes are below.

Other Ocular Lesions

All ocular lesion variables are coded as follows:
0 = No
1 = Questionable
2 = Yes

The variables are:

• Central artery occlusion
• Branch artery occlusion
• Central vein occlusion
• Branch vein occlusion
• Hollenhorst plaque
• Asteroid hyalosis
• Lg cup/disc ratio
• RH within disc margin
• Peripapillary atrophy
• Papillary swelling
• Other disc abnormality
• Glial/vitreous thickening
• Medullated nerve fibers
• Cellophane reflex
• Surface wrinkling retinopathy with or without tension lines
• Any drusen present in photo
• Soft drusen within 2 DD’s of macula
• RPE depigmentation
• Hyperpigmentation
• SSR detachment
• Subretinal hemorrhage
• Subretinal fibrous
• Geographic atrophy
• Chorioretinal scars
• Nevus
• Retinal detachment
• Other ocular lesions

Calculated Variables

The following variables are calculated from the light box grading variables.

Retinopathy
Retinopathy is a yes/no summary variable defined based on the value of the retinal level.

No= Retinal level of 10
Yes= Retinal level above 10 but less than 90

Focal Narrowing
Focal narrowing is a yes/no summary variable defined from the values of the arteriole focal narrowing by quadrants (ST, SN, IN, IT). At least two quadrants must have valid values for the summary variable to be defined. A response of mild, moderate or severe (2 or higher) in any of the four quadrants is considered definite focal narrowing. In the absence of definite focal narrowing, a response of questionable in any of the four quadrants is considered questionable. No focal narrowing is defined from a response of none in at least two quadrants. Questionable has been pooled with none.

No= None in at least two quadrants, or questionable in any quadrant in the absence of any positive quadrant
Yes= Mild, moderate or severe in any quadrant

A/V Nicking
A/V Nicking is a yes/no summary variable defined from the values of the changes in A/V crossing in four quadrants (ST, SN, IN, IT). The algorithm for defining A/V Nicking is the same as that for Focal Narrowing, except that either the ST or IT quadrant must be negative (along with at least one other quadrant) for A/V Nicking to be negative.

No= None in at least two quadrants (one of which is ST or IT), or questionable in any quadrant in the absence of any positive quadrant
Yes= Definite or severe in any quadrant

Image Analysis Variables

Image analysis was used to obtain arteriole, vein, branch and arteriolar equivalent measurements. These values are summarized by the five calculated variables which are below.

• Central retinal arteriolar equivalent, trunk (CRAE_T)
• Calculated from the arteriole measurements using the algorithm below.
• Central retinal arteriolar equivalent, branch (CRAE_B)
• Calculated from the arteriole equivalent measurements using the algorithm below.
• Central retinal venous equivalent (CRVE)
• Calculated from the vein measurements using the algorithm below.

The above three variables are calculated using the following algorithm:

Measurements are combined according to the Parr formula in pairs according to size. The largest and smallest measurements are combined, then the next largest and next smallest are combined, and so forth until all meausurements have been used. With each new set of values the process is repeated until a final value is obtained. The Parr formulas are below; c is the combined value, a is the smaller value and b is the larger value.

For arteriole (CRAE_T and CRAE_B) measurements:
c = (0.87*a2 + 1.01*b2 -0.22*a*b - 10.76)1/2

For venule (CRVE) measurements:
c = (0.72*a2 + 0.91*b2 + 450.05)1/2

A/V ratio, trunk (AV_RATIO_T)
· values are the ratio of central retinal arteriolar equivalent, trunk, to central retinal venous equivalent

A/V ratio, branch (AV_RATIO_B)
· values are the ratio of central retinal arteriolar equivalent, branch, to central retinal venous equivalent