Abstract
Purpose: :
To estimate the risk of chronic late hypotony in eyes with uveitic glaucoma implanted with the Baerveldt 350 implant and to identify preoperative factors associated with chronic late hypotony.
Methods: :
Prospective clinical series of 50 consecutive first eyes with uveitic glaucoma implanted by one ophthalmologist (KB) with the Baerveldt 350 implant during a 5 year period (1 Apr 2000 – 1 Apr 2005). Excluded: 1 NLP before surgery, 4 second eyes, 12 Juvenile Idiopathic Arthritis eyes implanted with 8 Baerveldt 250 and 4 single plate Molteno implants. End–points: IOP, number of glaucoma medications, procedures to control IOP (either for high or low IOP), severe complications. Chronic hypotony was defined as IOP < 6mmHg without glaucoma medications on the last two consecutive visits (at least 6 months after implantation).
Results: :
50 patients (mean age 50 yrs, range 14 – 83, SD 17 years) were followed for at least 6 postoperative months (mean 28 ± SD 14 months). The mean ± SD preoperative IOP was 28.0±7.3 mmHg on 3.0±1.0 glaucoma medications (68% on acetazolamide) reducing to 12.5mmHg on 0.6±0.9 glaucoma medications at last follow–up. 42/50 (84%) were controlled (28 or 56% without glaucoma medication and 14 or 28% with medication). 1 was uncontrolled and 2 required further surgery for high IOP (aqueous misdirection). Chronic hypotony occurred in 5 eyes (10%), of whom 2 did not require further surgery (mild hypotony), 2 were corrected by tube ligation and in 1 case the tube was removed for intractable hypotony . Logistic regression for race, gender, eye, age, duration of follow–up, type of uveitis, preoperative IOP, preoperative glaucoma medications, suggested an association between chronic late hypotony and preoperative (low) IOP (p=0.018) and (young) age at implantation (p=0.046).
Conclusions: :
Smaller surface area aqueous shunts are often advised in uveitic glaucoma because of concerns that low aqueous production may lead to chronic hypotony. However, many eyes with uveitic glaucoma fail to achieve satisfactory IOP control with smaller surface area devices because of recurrent inflammation and an elevated healing tendency. In this study 10% of eyes developed chronic late hypotony, no suprachoroidal haemorrhages were sustained, and 84% were controlled within the normal range, mostly without glaucoma medication. The risk of hypotony was highest in younger uveitics with lower preoperative IOP, independent of the type of uveitis, and especially in those controlled within the normal range on glaucoma medication before surgery. It is likely that patients fitting this profile would be better suited to smaller surface area devices.
Keywords: intraocular pressure