A STUDY OF AQUEOUS-HUMOR DYNAMICS IN KERATOCONUS

Clinical observations suggest that patients with keratoconus have lowe r intraocular pressures, on average, than normal subjects. Our purpose was to determine whether differences in aqueous production and outflo w facility could account for differences in intraocular pressure betwe en a group of patients with keratoconus and a group of normal, age-mat ched control subjects. Aqueous humor dynamics were determined by the u se of fluorophotometry in one eye of seven patients with keratoconus a nd ten age-matched normal subjects. Intraocular pressure was measured by applanation tonometry. Keratoconus patients had a statistically sig nificant lower mean intraocular pressure than normal control subjects (11 . 3 +/- 1 . 6 mmHg vs. 16 . 6 +/- 2 . 8 mmHg, P = 0 . 0004). The d ifference in mean intraocular pressure remained significant even after correcting for possible errors in applanation tonometry due to thin c orneal stroma. There was no difference in mean aqueous humor flow rate s in the keratoconus patients as compared to controls (2 . 29 +/- 0 . 53 mu l min(-1) vs. 2 . 21 +/- 0 . 48 mu min(-1), P = 0 . 73). The mea n apparent outflow facility was 0 . 21 +/- 0 . 07 mu l min(-1) mmHg(-1 ) for keratoconus patients compared to 0 . 14 +/- 0 . 03 mu l min(-1) mmHg(-1) for controls (P = 0 . 02). Lower mean intraocular pressure in keratoconus patients appears to be due to increased outflow facility as compared to normal subjects. (C) 1996 Academic Press Limited