WHAT IS PNT?
Pneumatic Trabeculoplasty is a new, safe, non-invasive procedure which
has been clinically demonstrated (1-6) to further reduce elevated
Intraocular Pressure (IOP) in patients already undergoing pharmaceutical
treatments (beta-blockers, prostaglandins, adrenergics, etc) and have not
been able to achieve their ‘target IOP’ values. PNT can also be used in
the newly diagnosed patients who has yet to undergo pharmaceutical
THE PNT PROCEDURE
PNT uses a specially designed, patented, sterile, disposable PNT suction
ring. The PNT ring is applied to the patient’s eye and connected to a
vacuum controller which has been specifically designed to deliver a
vacuum of approximately 21 inches of Hg for a duration of one minute. A
PNT treatment involves 2 applications with a rest period of 5 minutes
between each application. The treatment is repeated after one week and
then on average, every three months unless a physician determines
otherwise. PNT appears to act on the trabecular meshwork resulting in an
increase in the facility of aqueous outflow (2).
MECHANISM of ACTION
Although the mechanism of action has not been fully elucidated there is
evidence that the site of action is the trabecular meshwork. The
mechanism may involve a transient stretching of the zonules which results
in a change in the trabecular meshwork. Marchini and co-workers recently
reported on their study (2), which included UBM scans on patients pre-
and post PNT, and concluded that “the UBM analysis seemed to confirm a
possible improvement due to PNT treatment of the aqueous outflow
through the trabecular meshwork, without widening of the uveoscleral
Several clinical studies have demonstrated the effectiveness of PNT to
reduce elevated IOP. Bucci. et. al (1) performed a study in which the
primary goal was to demonstrate the ability of PNT to reduce elevated IOP
in patients diagnosed with Primary Open Angle Glaucoma (POAG) or
Ocular Hypertension (OHT). Thirty-seven patients were enrolled in the
study, their glaucoma medication discontinued and a sufficient washout
period employed prior to their first PNT treatment.
There were 10 patient withdrawals during the trial 4 of which were for
reasons not attributable to the PNT procedure (i.e. increase pressure in
untreated eye during first 30 days of the trial). Twenty-seven patients
(73%) completed the trial. Maximum improvement was achieved
approximately 60-90 days following PNT treatment and was approximately
4 mm Hg. 40-60% of patients achieved an IOP reduction of 20% or more
during the trial. No serious adverse side effects were observed during
Offermann and Augustin (4) have reported on the IOP reduction
achieved following addition of PNT to patients with POAG who were
poorly controlled with Latanoprost. Baseline intraocular pressure (IOP)
ranged between 18 to 24 mmHg. 20 eyes were treated with PNT on day
0, 7, 90 and 120. Comprehensive visual assessments were performed
on Day 1, 1 month and 3 months after treatment.
Treatment group mean IOP at baseline was 20.15 mm Hg and was
reduced to 16.5 mm Hg on Day 120 (-3.65 mm Hg; -18.1%). They
concluded that PNT seems to be a safe and effective treatment to
decrease IOP in patients suffering from POAG.
Calabria and co-workers (5) have reported on a study, carried out in
Ghana, involving 42 patients (82 glaucomatous eyes) with significantly
elevated IOP. The aim of the study was to determine the efficacy and
safety of PNT alone to lower IOP in African patients with POAG. They
reported 87.8% of the eyes exhibited an IOP lowering following PNT with
73% of the eyes experiencing a decrease of greater than 15%.
Decreases of greater that 15% are considered efficacious according to
the European Guidelines for Glaucoma. In their conclusions they stated
that, “Moreover, the lack of side effects, except for transient
subconjunctival hyperemia and subconjunctival haemorrhage, makes
PNT safe and easy to perform …”.
Marchini (2,3) and co-workers have reported on a prospective study in
which they determined the IOP lowering effect of PNT in patients not
adequately controlled on anti-glaucoma medication. In this study, 14
patients remained on their drug therapy and PNT was added to their
treatment algorithm. The mean starting IOP was 22 ± 1.8 mm Hg. A
statistically significant reduction of greater than -15%, with a maximum
on day 8, was observed for the entire study. They also reported that
UBM analysis did not show any significant changes after the PNT
treatments from the baseline, either on anterior chamber depth (ACD)
or angle width (SCPA).
Changes were noted in the CBT and uveal reflectivity under the scleral
tissue probably due to compression induced by the suction ring. They
concluded that the data was consistent with a mechanism of action
involving increased outflow via the trabecular meshwork.
(1) M.G. Bucci, M. Centofanti, F. Oddone, M. Parravano, C. Balacco Gabrieli, J. Pecori-Giraldi, A. Librando, E. Paone, I.D. Bores, Pilot study to
evaluate the efficacy and safety of pneumatic trabeculoplasty in glaucoma and ocular hypertension, Eur. J.Ophthal. 2005; 15 (3)
(2) Ceruti, P., Marraffa, M., Morbio, R., Bertoldo, G., Marchini, G., Efficacy of Pneumatic Trabeculoplasty in Primary Open Angle Glaucoma,
Invest. Ophthal. Vis. Sci. 2006; (47)
(3) Ceruti, P., Marchini, G., "La PneumoTrabeculoPlastica nel trattamento del POAG" (Pneumatic Trabeculoplasty in the Treatment of POAG),
presented at the 4th International Congress of the Italian Society of Ophthalmology, Rome, Italy, 2006.
(4) Offermann, I., Augustin, AJ, "Pneumatische Trabekuloplastik (PNT) bei primärem Offen winkel glaukom" (Pneumatic Trabeculoplasty (PNT)
in Primary Open Angle Glaucoma), presented at the 19th Congress of German Ophthalmic Surgeons (DOC), Nuremberg, Germany, 2006
(5) Prigione G., Hesse, A. Lester, M., Rolando, M., Calabria, G., Safety and Efficacy of Pneumatic Trabeculoplasty in African Population, Invest.
Ophthal. Vis. Sci.; 2006 (47)
6) G. Avalos-Urzua, L.D. Bores, J.T. LiVecchi, Pneumatic Trabeculoplasty: A New Method To Treat Primary Open-Angle Glaucoma and Reduce
the Number of Concomitant Medications, Ann Ophthalmol, 2005; 37 (1) pg. 37-46
Avalos and LiVecchi (6) have
reported on their study of 177
patients performed to determine
the effectiveness of PNT to lower
IOP. They also evaluated the
reduction in drug utilization
required to control IOP as a
secondary endpoint. 177
patients (320) eyes were treated
and the trial duration was 6
months. At the end of the trial
patients were allowed to continue
with PNT if they had exhibited a
positive response. They
reported no serious side effects
to vision and no changes in the
visual field or optic nerve head.
Statistically significant decreases
in both IOP and drug utilization
were observed in this trial. They
concluded that PNT can be used
effectively in the therapeutic
treatment of glaucoma patients.
Bores (6) reported on his study involving 172 patients to confirm the
effectiveness of PNT in reducing/controlling IOP while reducing the
number of drugs needed to maintain the pressure within a range
considered to be clinically acceptable. He also reported a strong shift to
less medications in his study.
In summary, the clinical experience to date with PNT is excellent.
Approximately 75% of patients will exhibit an IOP reduction following PNT.
The duration of IOP reduction is, on average, 3-4 months, at which time
the procedure can be repeated. The side effect profile is consistent with
that expected to occur with the use of a topical anesthetic and a plastic
ring on the ocular surface. The most common side effects in the clinical
trials were subconjunctival hyperemia and subconjunctival hemorrhage.
Side effects were found to generally resolve without medical intervention.
For complete prescribing instructions please refer to the ‘Instructions for