An observational study with prospective enrollment, compliant with the tenets of the Declaration of Helsinki.
Patients were consecutively recruited from those referred between January 2019 and January 2021 at the Eyecare Clinic, Brescia, Italy. All research and measurements adhered to the tenets of the Declaration of Helsinki, the project has been approved by our review board and written informed consent was obtained for each participant. At enrolment, each patient underwent a detailed anamnesis collection including demographic parameters and medical history with special attention to glaucoma medications, prior medical, prior laser or surgical therapies. A full ophthalmic examination including logMAR best-corrected visual acuity (BCVA) assessment, slit-lamp examination of the anterior segment including indirect gonioscopy of the angle with a Goldmann goniolens, IOP measurement by Goldmann applanation tonometry, fundus examination was performed. After pupil dilation, obtained with 1% tropicamide solution, a detailed examination of the lens and retinal periphery were completed. In particular, the examiner search for pigment deposition on corneal endothelium, peripupillary or mid-peripheral iris defects visualized directly or upon retroillumination, exfoliation material on the anterior lens capsule. Any fundus signs attributable to retinal vascular disorders or ocular ischemic syndrome were excluded. Anterior chamber angle (ACA) was considered open if pigmented trabecular meshwork was clearly visible in all quadrants. Clinical evaluation of pathological aspects of ACA, with special attention to peripheral anterior synechiae or pigmented Schwalbe line, was performed. Baseline examination also included instrumental examinations performed by an experienced examiner (LT). Ultrasound biomicroscopy (UBM) examination (using 50 MHz Aviso S, Quantel Medical, Clermont-Ferrand, France) was performed for qualitative confirmation of open ACA, iris root insertion and ciliary bodies anomalies evaluation (Figure 1). A measurement of thickness of the retina nerve fiber layer (RNFL) using Spectralis (HRA + OCT, software version. 184.108.40.206, Heidelberg Engineering, Germany) was performed. A collection of Mean deviation (MD) values, derived from the most recent visual field examination using the 24-2 Swedish interactive threshold Algorithm (SITA) with a Humphrey Field Analyzer 3 (Carl Zeiss Meditec AG, Jena, Germany) was done. Visual field tests older than 2 months respect to the baseline or performed with another instrument were rejected and a new test was performed at baseline consultation.
Inclusion criteria were:
- Open angle eyes established with gonioscopy or ultrasound biomicroscope (UBM) examination
- Eyes with POAG under treatment with one or more medications
- Patients willing to control IOP without medical therapy, due to side effect of medical therapy
Exclusion criteria were:
- eyes with angle closure glaucoma
- eyes with secondary open angle glaucoma or end-stage glaucoma
- history of prior glaucoma laser or surgical treatment
All laser MLT procedure were performed by one experienced ophthalmologist to all eyes under topical anesthesia (1-2 drop of Chlorhydrate D'oxybuprocaine, Novesina ® 1.6 mg/0.4 ml, Théa Laboratories, Clermont-Ferrand, France). A Goldmann three-mirror goniolens (Volk Optical Inc., Mentor, OH,USA) was adjusted on the cornea, in order to allow the ophthalmologist to see the trabecular meshwork (TM). A 577 wave-length laser IRIDEX IQ 577® Laser Systems (Iridex Corporation, Mountain View, CA, USA) was used to apply 300 consecutive spots of laser, with a diameter of 300 microns per spot, a power of 1000 mW, in a time of 300 msec per spot with 15% duty cycle over the full 360° of the TM. No space was left between spots.
After treatment, patients were not prescribed any anti-inflammatory drops post-laser and were instructed to continue the ongoing medical therapy before MLT for one week and to suspend one eye-drop afterwards until the following consultation. Follow-up consultations were scheduled at 1, 6, 12, 18 and 24 months. At baseline and at each consultation, data were collected on IOP (measured by Goldmann applanation tonometry), logMAR BCVA assessment, local and systemic side effects, number of eye-drops in use (for quantifying the number of glaucoma eyedrops, topical fixed combination medications were considered 2 medications and other topical glaucoma medications were assigned 1 medication). At each postoperative consultation, if the IOP was normal (lower than 20 mmHg), the patients still using eye-drops were instructed to stop them. If IOP was not normal a retreatment with MLT was performed prior a written informed consent obtained for each participant.
The primary outcome was to verify the efficacy of MLT in leading the eye to normal IOP values without medical therapy at 12 and 24 months after treatment.
The secondary outcomes were:
- Verify the IOP change in time after treatment, by reporting the IOP values at 1, 6, 12, 18 and 24 months
- Verify the rate of retreatments at 1, 6, 12, 18 and 24 months
- Verify the change in medical therapy at 1, 6, 12, 18 and 24 months, compared to the preoperative therapy.
- Verify the change in side effects. The side effects that were looked for were:
- local (stinging, redness, itching; changes in eyelid skin color, blurred vision, IOP spikes, hypotony, bleeding, choroidal detachment);
- neurological (depression; loss of memory, drowsiness);
- cardiovascular (low or high blood pressure; fatigue, irregular heart rate).
Study parameters were described by means of descriptive statistics: absolute and relative frequencies for qualitative parameters (gender, eye, lens status) and mean value, standard deviation for quantitative parameters (age, number of ocular hypotensive medications, MD, RNFL thickness).
Mean IOP changes were compared with baseline and during follow-up by analysis of variance as a mix effect with repeated measures model (ANOVA). It was analyzed the statistical significance in IOP values comparing:
the preoperative value and the 1-month value, the preoperative value and the 24-month value, the 1-month value and the 12-month value, the 1-month value and the 24-month value. BCVA mean changes, mean number of glaucoma medications were compared using paired samples t-test. Statistical analyses were performed by using SAS software version 9.4 (SAS Institute, Cary, NC, USA). Data were assumed significant if p < 0.05.