The Ophthalmic Examination as It Pertains to General Ocular Toxicology: Basic and Advanced Techniques and Species-Associated Findings - Ocular Pharmacology and Toxicology - page 149

Table 2
Criteria used for a modified Hackett-McDonald scoring system [ 10 ]

Conjunctival congestion

0 ¼ Normal. May appear blanched to reddish pink without perilimbal injection (except at 12:00 and

6:00 o'clock positions) with vessels of the palpebral and bulbar conjunctiva easily observed.

1 ¼ A flushed, reddish color predominantly confined to the palpebral conjunctiva with some

perilimbal injection but primarily confined to the lower and upper parts of the eye from the
4:00, 7:00, 11:00, and 1:00 o'clock positions.

2 ¼ Bright red color of the palpebral conjunctiva with accompanying perilimbal injection covering at

least 75 % of the circumference of the perilimbal region.

3 ¼ Dark, beefy red color with congestion of both the bulbar and the palpebral conjunctiva along with

pronounced perilimbal injection and the presence of petechia on the conjunctiva. The petechia
generally predominate along the nictitating membrane and the upper palpebral conjunctiva.

Conjunctival swelling (there are five divisions from 0 to 4)

0 ¼ Normal or no swelling of the conjunctival tissue.

1 ¼ Swelling above normal without eversion of the lids (can be easily ascertained by noting that the

upper and lower eyelids are positioned as in the normal eye); swelling generally starts in the
lower cul-de-sac near the inner canthus, which needs slit lamp examination.

2 ¼ Swelling with misalignment of the normal approximation of the lower and upper eyelids;

primarily confined to the upper eyelid so that in the initial stages the misapproximation of the
eyelids begins by partial eversion of the upper eyelid. In this stage, swelling is confined generally
to the upper eyelid, although it exists in the lower cul-de-sac (observed best with the slit lamp).

3 ¼ Swelling definite with partial eversion of the upper and lower eyelids essentially equivalent. This

can be easily ascertained by looking at the animal head-on and noticing the positioning of the
eyelids; if the eye margins do not meet, eversion has occurred.

4 ¼ Eversion of the upper eyelid is pronounced with less pronounced eversion of the lower eyelid. It is

difficult to retract the lids and observe the perilimbal region.

Conjunctival discharge —Discharge is defined as a whitish-gray precipitate, which should not be confused
with the small amount of clear, inspissated, mucoid material that can be formed in the medial canthus
of a substantial number of rabbit eyes. This material can be removed with a cotton swab before the
animals are used.

0 ¼ Normal. No discharge.

1 ¼ Discharge above normal and present on the inner portion of the eye but not on the lids or hairs of

the eyelids. One can ignore the small amount that is in the inner and outer canthus if it has not
been removed prior to starting the study.

2 ¼ Discharge is abundant, easily observed, and has collected on the lids and around the hairs of the

eyelids.

3 ¼ Discharge has been flowing over the eyelids so as to wet the hairs substantially on the skin around

the eye.

Aqueous flare —The intensity of the Tyndall phenomenon is scored by comparing the normal Tyndall
effect observed when the slit lamp beam passes through the lens with that seen in the anterior chamber.
The presence of aqueous flare is presumptive evidence of breakdown of the blood-aqueous barrier.

0 ¼ The absence of visible light beam in the anterior chamber (no Tyndall effect).

(continued)