1st. Are the eyelids swollen, hypertrophied or faulty in form, position or movements. Faults as thus indicated may imply any one of a great variety of disorders which should be followed out to their accurate diagnosis. It may be bruises, lacerations, punctures, parasites, conjunctivitis, keratitis, dropsy, anæmia, hepatic or intestinal parasitism, nephritis, paresis, entropion, ectropion, etc.
2d. Inspect the cilia as regards form, size and direction. Absence or wrong direction may imply disease of the Meibomian glands, infective inflammation, demodex or other acarian infesting, or turning in or out in inflammatory conditions.
3d. See that the lachrymal puncta are open and that there is no overdistension of the sac. The overflow of tears and the swelling of the caruncle and of the area beneath it will often indicate such trouble. In its turn it may imply inflammation of the duct, and obstruction by the tenacious muco-purulent product, or it may imply merely obstruction of its lower end by a dried scab. This last may be seen in the horse, on the floor of the false nostril at the line of junction of the skin and mucosa, and in the ass, higher up on the inner side of the ala nasi. In exceptional cases it may be desirable to pass a stilet through the canal from the puncta downward or from below upward to determine whether it is pervious.
4th. Determine the vascularity of the conjunctiva. When free from pigment as it habitually is in pigs and birds this is easily done, while in animals like the horse, in which the bulbar portion, which covers the sclerotic, is largely pigmented, we can scrutinize only the pigment free parts. In health there should be only a few, fine, pink vessels which move with the mucosa when pressed aside on the bulb. In congestion the surface may appear brick red, and the vessels are irregular, large, tortuous and are seen to anastomose at frequent intervals. These move on the bulb when pressed. The congestion is usually deepest on the palpebral mucosa and in the cul de sac, and may be whitened for an instant by pressure through the eyelid. To expose the conjunctiva the right fore finger and thumb may be pressed on the upper and lower lids respectively of the left eye, and the left finger and thumb for the right, allowing them to slide backward above and below the eyeball. Another method is to seize the cilia and edge of the upper eyelid between the finger and thumb, and draw it downward and outward from the bulb, and then deftly invert it over the tip of the finger. In the old the unpigmented conjunctiva may appear yellow from the presence of subconjunctival fat, or this may appear at any age from hepatic disease (distomatosis) or icterus. It is swollen, or dropsical in anæmia, distomatosis, etc.
5th. Examine the ciliary vessels whether they are congested or not. These are distinguished from the conjunctival vessels in that they radiate in straight lines outward from the margin of the transparent cornea and do not move on the sclerotic under pressure. They are enlarged and very red in congestion of the ciliary circle and in iritis. In eyes devoid of pigment over the sclerotic, there is usually a circular, narrow, white zone between the congested area and the margin of the transparent cornea.
6th. Examine the Membrana Nictitans. See that its free margin is uniformly smooth, even, and thin and that there is no swelling, congestion nor morbid growth on any part of the structure.
7th. See if the transparent cornea is perfectly and uniformly smooth, transparent and glistening and if it reflects clear, erect images of all objects in front of it. The image of a round object which shows any irregularity in the curvature of its margin implies a deviation from an uniform curvature of the cornea: the image narrows in the direction of the smaller arc and broadens in the direction of the larger one (see keratoscopy, and corneal astigmatism).
8th. A foreign body on or in the cornea may be recognized in a good light, but better and more certainly under focal oblique illumination (see this heading).
9th. A corneal ulcer may be similarly recognized. It is made more strikingly manifest by instilling into the lower cul de sac a drop of a solution of fluorescin and rubbing it over the eye by moving the eyelids with the finger. This will stain the whole cornea. If now the excess of stain is washed away by a few drops of boric acid, the healthy part of the cornea is cleared up and the ulcer retains a bright yellowish green tint.
10th. Opacity or Floating objects in the aqueous humor (flocculi of lymph, pus, pigment, blood, worms) are always to be looked for. They may be detected by placing the eye in a favorable light. They may be still more clearly shown under focal illumination (see below).