Effects of ophthalmic vehicles on the stability of the precorneal film

Semiquantitative interference study of fatty layer of precorneal film

Reflecting colours from the fatty layer of the precorneal film have been studied using mat filter (grease-proof paper, parchment paper, tracing paper) in front of the slit lamp mirror, maximally open light slit in a half-lit room, and magnification x 15. The palpebral fissure was narrowed until occurrence of red interference colour (2000 A). In 206 normal eyes the fatty layer was 102 +/- 3nm (+/- SEM), or about 0.1 micron, independent of age, sex and BUT (break up time). Maximum on awakening. Coefficient of variation 12.7 per cent. An increased fatty layer was noticed in cases of blepharitis (129 +/- 8 nm), in 91 per cent wearing hard contact lenses and 73 per cent wearing soft contact lenses. The fatty layer was likewise seen to be augmented in patients with acute infectious conjunctivitis (193 +/- 3 nm), chronic infectious conjunctivitis (164 +/- 7 nm), and in all states complicated by bacterial infection. The fatty layer is normal in allergic and chronic simple conjunctivitis. Silicone oil was found to effect reduction of the fatty layer.

Treatment of keratoconjunctivitis sicca with liquid paraffin or polyvinyl alcohol in double-blind trial

Twenty-two eyes affected with keratoconjunctivitis sicca have been subjected to double trials using the double-blind randomized cross-over technique. Polyvinyl alcohol in a 5% concentration improved the condition whereas liquid paraffin aggravated it, as estimated subjectively, and by the measurement of the break up time of the corneal film, and, finally, by the scoring of rose bengal vital staining of exposed cornea and conjunctiva. The conclusion is drawn that oil is contraindicated in keratoconjunctivitis sicca, and that rose bengal scoring (modified Bijsterveld method) is a valuable aid in control of the sicca syndrome.

Outflow of tears and its influence on tear secretion and break up time (B.U.T.)

Schirmer's test shows that a retarded outflow of tears causes reduction of the tear secretion. The B.U.T. is independent of the outflow of tears in patients with epiphora (119 eyes with mechanical obstruction, functional obstruction, or normal passage). Mucomimetics prolong the B.U.T. and retard the outflow of tears, whereas ointments reduce both the B.U.T. and the outflow (74 eyes). The B.U.T. becomes reduced when tears are absorbed by filter paper in Schirmer's test, but remains uninfluenced by filter paper inserted in the fornix. The B.U.T. is a valuable clinical test. It is the resultant of many different factors (tear volume, mucus, fat, etc.).