SLT: A New Option for Pseudoexfoliative Glaucoma
MADHU NAGAR, MS OPHTH, FRCS OPHTH (ED)
Pseudoexfoliation syndrome (PXFS) is a disease characterized by the accumulation of abnormal fibrillar extracellular material in ocular structures. When, however, this syndrome is associated with increased intraocular pressure (IOP) and optic nerve damage it is known as pseudoexfoliative glaucoma (PXFG).
Reports on the rate of glaucoma development amongst PXFS sufferers vary in the literature. In 2002, a report by Puska and co-workers reported a conversion rate of 3.2% PXFS cases per year to PXFG.1 Elsewhere, a team led by Jeng found that, in patients with PXFS, the probability of developing glaucoma was 44% after 15 years2 whilst a study by Grodum, et al., found 55.1% of PXFS patients went on to develop glaucoma after a mean of 8.7 years.3 In the Early Manifest Glaucoma Trial, the risk of glaucomatous progression over a six-year period was found to be 2.2 times higher in PXFG patients, compared with non PXFG sufferers.4
The labile nature of IOP, and the high diurnal IOP fluctuations experienced by sufferers, makes exfoliative glaucoma one of the most difficult forms of open-angle glaucoma to manage.
Current management techniques include:
- Regular follow-up of patients (including those with normal IOPs and optic discs).
- Early use of topical anti-glaucoma medications.
- Surgical treatment (including laser trabeculoplasty and filtration surgery) in patients resistant to medical therapy.
Argon laser trabeculoplasty (ALT) has been used to treat PXFG patients with excellent initial success, however, many studies have shown that there are risks involved with this procedure: post-treatment increase in IOP, coagulative damage and scarring to the trabecular meshwork, and it may also limit the efficacy of further non-surgical therapy. Thus, the number of users of ALT has been dwindling in recent years. Selective laser trabeculoplasty (SLT), on the other hand, has been shown in studies to be equally efficacious to ALT in reducing IOP, but this procedure is without the side effects that are more commonly seen with ALT, such as thermal damage to the trabecular meshwork.
Proving the point
To better evaluate the response to SLT in eyes with PXFG, a retrospective chart review of patients who underwent SLT from January 2000 to December 2005 was performed (571 eyes in total). Of those, 24 eyes of 21 patients (11 male, 10 female; mean age 72 years) had either PXFS or PXFG and were available for analysis.
Figure 1 |
Of the 21 patients treated, three received SLT treatment in both eyes, whilst the remaining 18 patients were treated in one eye. 17 eyes in total underwent 180° SLT treatment and seven underwent 360° SLT treatment (average laser power used was 0.7 mJs). Mean follow-up was 36 months.
Figure 2 |
Over the follow-up period, IOP decreased by 43% from a mean preoperative level of 28.3 mmHg to a mean postoperative level of 16.1 mmHg (Figure 1). Of the patients included in this review, 67% responded well to SLT treatment and achieved the targeted IOP, 11% were non-responders i.e. no noticeable reduction in IOP, and 22% responded to SLT but the effect diminished over time, thus these patients were labelled failures (Figure 2).
Figure 3a |
The number of anti-glaucoma medications used prior to SLT ranged from four medications in one patient (5%) to no medications in 12 patients (57%). Twenty-three percent of patients were receiving one medication. Medical treatment was either washed off prior to SLT or after SLT and at the last follow-up visit, the number of patients on no medications had improved to 66% (n=14), with 19% on one medication (n=4). One patient still required four medications to control pressure, however, overall, there was a 49% reduction in the number of medications required between the preoperative exam and the final follow-up exam (Figure 3 a, b & c).
Exercise caution to avoid risks
Figure 3b |
Overall, I sincerely believe that SLT is the best primary therapy for this aggressive form of glaucoma simply because PXFG sufferers usually have significantly high IOPs and SLT is typically able to reduce IOP to a sufficient level in these eyes.
Figure 3c |
Admittedly, there have been reports of temporary, paradoxical increases in IOP following SLT therapy. Harasymowycz and co-workers, for example, reported on four cases of eyes with heavily pigmented trabecular meshwork, three of them with pigmentary glaucoma, in whom SLT treatment induced a marked and sustained elevation in IOP, despite the administration of brimonidine 0.2% immediately before the procedure. As a result, three of the four required trabeculectomy because of uncontrolled IOP.5 Similar cases of a temporary paradoxical IOP rise after SLT in eyes with heavily pigmented angles have also been recently reported, even at low energy radiation in the absence of steroid treatment, and persisted for 12 weeks after treatment.6
Table 1: SLT adverse effects |
It is therefore advisable not perform 360° treatment in one session but in two sessions at least two weeks apart or to perform 180° SLT treatment instead.
In short... |
I sincerely believe that SLT presents an excellent treatment option for PXFG patients. It takes the treatment out of the hands of the patient and puts it into the hands of the skilled surgeon, which affords several advantages, primarily compliance. Furthermore, in the right patient, it is associated with a low risk of postoperative complications and side effects (Table 1).
Acknowledgements
I would like to say a special thank you to my colleagues, Mr Bharat Kapoor, Mr Rahul Yadav and Mr Nimish Shah, who made the retrospective review of case notes possible.
Madhu Nagar MS Ophth, FRCS Ophth (Ed) |
Author
Madhu Nagar MS Ophth, FRCS Ophth (Ed) is a consultant ophthalmologist and glaucoma specialist at Clayton Eye Centre, Mid Yorkshire Hospital Trust, Wakefield, UK. She may be reached by E-mail: madhunagar@hotmail.com
References
1. P.M. Puska. J. Glaucoma 2002;11(6):517-524.
2. S.M. Jeng, et al. J. Glaucoma 2007;16(1):117-121.
3. K. Grodum, et al. Ophthalmology 2005;112(3):386-390.
4. A. Heijl, et al. Arch. Ophthalmol. 2002;120:1268-1279.
5. P.J. Harasymowycz. Am. J. Ophthalmol. 2005;139:1110.
6. S. Van de Veire, et al. Bull. Soc. Belge. Ophtalmol. 2006;(299):5-10.
|
|
