Draize et al described a scale of weighted scores for grading the severity of ocular lesions in rabbits following exposure to a chemical agent. This is based on a modification of the scoring system of Friedenwald et al.
Protocol:
(1) 0.1 mL of material is instilled into the conjunctival sac.
(2) Readings are taken at 1, 24 and 48 hours after instillation. If residual injury is present, then a reading at 96 hours is also taken.
(3) The cornea, iris and conjunctivae are evaluated and scored separately.
Cornea
|
Parameter |
Finding |
Points |
|---|---|---|
|
opacity - degree of density |
none |
0 |
|
|
scattered or diffuse area; details of iris are clearly visible |
1 |
|
|
easily discernible translucent areas; details of iris slightly obscured |
2 |
|
|
opalescent areas, no details of iris visible, size of pupil barely discernible |
3 |
|
|
opaque; iris invisible |
4 |
|
area of cornea involved |
none |
0 |
|
|
1-25% |
1 |
|
|
26-50% |
2 |
|
|
51-75% |
3 |
|
|
76-100% |
4 |
after Table 6, page 387
where:
• The opacity reading is taken at the most dense area.
• Area involved originally stated: (1) one quarter (or less) but not zero; (2) greater than one quarter - less than one-half; (3) greater than one-half less than three quarters; (4) greater than three quarters up to whole area; note that exactly 50% involvement not covered.
cornea score =
= (opacity points) * (area of cornea involved points) * 5
Interpretation:
• minimum score: 0
• maximum score: 80
Iris
|
Finding |
Points |
|---|---|
|
no change from normal |
0 |
|
iris still reacts to light (sluggish response is positive) any or all of the following or any combination • folds above normal • congestion • swelling • circumcorneal injection |
1 |
|
any or all of the following • no reaction to light • hemorrhage • gross destruction |
2 |
after Table 6, page 387
iris score =
= (iris points) * 5
Interpretation:
• minimum score: 0
• maximum score: 10
Conjunctivae
|
Parameter |
Finding |
Points |
|---|---|---|
|
redness |
normal |
0 |
|
|
vessels definitely injected above normal |
1 |
|
|
more diffuse, deeper crimson red, individual vessels not easily discernible |
2 |
|
|
diffuse beefy red |
3 |
|
chemosis |
normal |
0 |
|
|
any swelling above normal, including the nictitating membrane |
1 |
|
|
obvious swelling with partial eversion of lids |
2 |
|
|
swelling with lids about half closed |
3 |
|
|
swelling with lids about half closed to completely closed |
4 |
|
discharge |
normal |
0 |
|
|
any amount different from normal (does not include the small amount observed in inner canthus of normal animals) |
1 |
|
|
discharge with moistening of the lids and hairs just adjacent to the lids |
2 |
|
|
discharge with moistening of the lids and considerable area around the eyes |
3 |
after Table 6, page 387
where:
• redness refers to palpebral conjunctivae only (The palpebral conjunctiva covers the posterior surface of the eyelid).
conjunctivae score =
= ((redness points) + (chemosis points) + (discharge points)) * 2
Interpretation:
• minimum score: 0
• maximum score: 20
Total Score
total score =
= (corneal score) + (iris score) + (conjunctivae score)
Interpretation:
• minimum score: 0
• maximum score: 110
• The higher the score, the more severe the reaction.
Purpose: To use the method of Draize et al to evaluate the ocular irritation caused by instilling a chemical compound into the conjunctival sac of a rabbit.
Specialty: Toxicology, Emergency Medicine, Critical Care, Ophthalmology
Objective: severity, prognosis, stage, adverse effects
ICD-10: T26.9,
