Aqueous humor dynamics in uveitis: a comparative study in hypertensive uveitis

Abstract

Purpose : Comparison of the aqueous humor parameters in patients with recurrent idiopathic anterior uveitis with healthy controls.

Methods : Patients with a history of idiopathic recurrent anterior uveitis (≥3 attacks) with or without raised IOP (> 21 mmHg) were enrolled. All patients were quiescent at the time of enrolment. Normal healthy subjects with no ocular problems and IOP < 21mmHg at screening formed the control group. Exclusion criteria were patients with active intraocular inflammation, patients with other forms of secondary glaucoma, patients who previously had intraocular or laser surgery, those on systemic medication which can affect aqueous humor production and uveoscleral outflow and those with a history of allergy to fluorescein. Before study measurements, subjects were washed out of all hypotensive medications in the study eye for 4 weeks.
Aqueous humor dynamics were assessed by digital Shiøtz tonography, fluorophotometry, and pneumatonometry. Uveoscleral outflow was calculated using Goldmann’s equation with an assumed episcleral venous pressure of 10 mmHg.

Results : Thirty-two healthy volunteers, 32 patients with uveitis with normal IOP and 26 cases with hypertensive uveitis were recruited. The participants’ characteristics are shown in Table 1.

The mean tonographic outflow facility (C) in hypertensive uveitis cases was 0.20±0.14 µl/min/mmHg. This was significantly lower than controls (0.23±0.09 µl/min/mmHg, p=0.03) as well normotensives with uveitis (0.26±0.13 µl/min/mmHg, p=0.05). However, the aqueous flow rate (Ft) was similar across all groups (2.2± 0.72 µl/min, 2.1± 0.89 µl/min, and 2.5±0.88 µl/min). Additionally, the uveoscleral outflow (Fu) was comparable between all groups (Table 2).

Conclusions : 1. Aqueous humor production is not significantly affected by several attacks (≥3) of uveitis in eyes with or without raised IOP.
2. The cause of raised IOP in hypertensive uveitis is related to the reduction in trabecular outflow.
3. As none of the eyes were actively inflamed at the time of the study, cells and debris obstruction of the trabecular meshwork is unlikely.
4. One can assume that repeated episodes of uveitis and perhaps previous exposure to topical corticosteroids lead to permanent structural alteration of the trabecular meshwork in those eyes with hypertensive uveitis.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.

 

Tabel 1. Participants characteristics

 

Table 2. Aqueous humor dynamics parameters