Assessment of the quality of glaucoma referral letters based on a survey of glaucoma specialists and a glaucoma guideline.

OBJECTIVE: To assess the quality of glaucoma referral letters and to report on the results of a survey of glaucoma specialists about referral letter content. DESIGN: Cross-sectional study. PARTICIPANTS: A survey of 135 glaucoma specialists and audit of 200 consecutive referral letters to a tertiary glaucoma unit. METHODS: An online questionnaire was sent to members of the Canadian and American Glaucoma Societies asking what they considered the most important data to be included in a glaucoma referral. Consecutive referral letters to a tertiary glaucoma unit were assessed for legibility and content on the basis of the survey results and information items in current guidelines. MAIN OUTCOME MEASURES: Survey outcome and proportion of included content items in referral letters. RESULTS: The survey revealed that the top 5 most important data that glaucoma specialists would like to be included in a referral letter for progressive glaucoma were serial visual fields (VFs), current glaucoma therapy, current intraocular pressure (IOP), maximum IOP, and serial disc imaging. These items often were omitted in the referral letters audited. A total of 200 referral letters were assessed, 46% from ophthalmologists, 42% from optometrists, 10% from family practitioners, and 2% from other sources. Reasons for referral were diagnosis of glaucoma (37%), unstable glaucoma (25%), angle assessment (17%), and others (21%). Some 26% of the referral letters were deemed illegible (18% from ophthalmologists vs. 6% from optometrists; P< 0.01). Degree of urgency was mentioned in 27% of referrals. Optometrists were more likely than ophthalmologists to provide visual acuity (VA), IOP, refraction, and VFs (P< 0.01 for each). Some 24% of referrals for progression included more than 10 of the 14 information points suggested by the Canadian glaucoma guidelines, and 34% included fewer than 8 of the 14 points. CONCLUSIONS: Referral letters frequently did not include important information, with 34% of referral letters deemed substandard. Optometrist referrals were better than ophthalmologist referrals in terms of content and legibility. A checklist of clinical details for referring physicians is suggested, which includes maximum and current IOP, disc evaluation, serial VFs, and serial disc imaging.

Evaluation of the Performance of a 3D-Printed Smartphone-Based Retinal Imaging Device as a Screening Tool for Retinal Pathology in Mozambique.

Low-income countries carry approximately 90% of the global burden of visual impairment, and up to 80% of this could be prevented or cured. However, there are only a few studies on the prevalence of retinal disease in these countries. Easier access to retinal information would allow differential diagnosis and promote strategies to improve eye health, which are currently scarce. This pilot study aims to evaluate the functionality and usability of a tele-retinography system for the detection of retinal pathology, based on a low-cost portable retinal scanner, manufactured with 3D printing and controlled by a mobile phone with an application designed ad hoc. The study was conducted at the Manhiça Rural Hospital in Mozambique. General practitioners, with no specific knowledge of ophthalmology or previous use of retinography, performed digital retinographies on 104 hospitalized patients. The retinographies were acquired in video format, uploaded to a web platform, and reviewed centrally by two ophthalmologists, analyzing the image quality and the presence of retinal lesions. In our sample there was a high proportion of exudates and hemorrhages-8% and 4%, respectively. In addition, the presence of lesions was studied in patients with known underlying risk factors for retinal disease, such as HIV, diabetes, and/or hypertension. Our tele-retinography system based on a smartphone coupled with a simple and low-cost 3D printed device is easy to use by healthcare personnel without specialized ophthalmological knowledge and could be applied for the screening and initial diagnosis of retinal pathology.

Predictors of selective laser trabeculoplasty success in open angle glaucoma or ocular hypertension: does baseline tonography have a predictive role?

BACKGROUND: The determinants of success of selective laser trabeculoplasty (SLT) in treatment-naïve patients with open angle glaucoma (OAG) and ocular hypertension (OHT) have not been understood fully. Therefore, we have conducted this study to explore the predictors of success. METHODS: This is a retrospective review of a pre-existing database of patients who had received primary SLT at St Thomas' Hospital, London, UK. Patients with OAG and OHT who had received primary 360° SLT treatment and had reliable baseline tonographic outflow facility (TOF) with minimum of 1 year of follow-up were included. Univariate and multivariate analyses were performed to find the determinants of success. RESULTS: One hundred and seventy-four patients between August 2006 and February 2010 had received primary 360° SLT treatment and had baseline TOF measurement. Of these, 72 subjects fulfilled the eligibility criteria. In multivariate regression analysis, the only variable associated with success was baseline intraocular pressure (IOP) (R2=0.32, beta=-0.51, p<0.001, 95% CI -2.02 to -0.74). CONCLUSION: To our knowledge, this is the only study investigating the pretreatment TOF (measured with electronic Shiøtz tonography) and IOP as determinants of success 12 month's post-360° SLT in treatment-naïve patients with OAG and OHT. This study demonstrated that pretreatment IOP (and not TOF) is the only determinant of success after primary SLT therapy.

Comparison of Short-term Postoperative Hypotony Rates of 23-gauge vs 25-gauge Needles in Formation of the Scleral Tract for Baerveldt Tube Insertion into the Anterior Chamber.

INTRODUCTION: To compare the early postoperative hypotony rates and intraocular pressure (IOP) in two groups of eyes using either 23-gauge (23G) or 25-gauge (25G) needle in the creation of the anterior chamber entry tract for Baerveldt tube. The primary outcome measure was incidence of hypotony, and secondary outcome measures included comparison of mean IOP and other early complications. MATERIALS AND METHODS: Ours was a retrospective case review of consecutive patients who underwent 350 mm2 Baerveldt implantation in two units over a 2-year period. Data including IOP and complications were collected at 1 day, 1 week, and 1 month following surgery from patients' notes. Statistical analysis between groups was determined using the unpaired 2-tailed f-test for continuous variables and chi-squared test for categorical variables. Statistical significance was defined at the 0.05 level. RESULTS: A total of 58 eyes of 58 patients were included in this study. Preoperative mean IOP in the 25G group was significantly higher (26.4 ± 6.8 mm Hg) when compared with the 23G group (21.6 ± 4.0 mm Hg) (p = 0.002). The mean postoperative IOP remained significantly higher in the 25G group at day 1 (p=0.004), week 1 (p = 0.008), but not at month 1 (p = 0.744). Four patients in the 23G group had hypotony within 1 month postsurgery compared with no cases in the 25G group (chi-squared test p = 0.038). CONCLUSION: There was a significantly higher risk of early hypotony and lower IOP in the larger 23G group at days 1 and 7, although the IOP was similar in both groups by 1 month. CLINICAL SIGNIFICANCE: After all glaucoma drainage device (GDD) tube implantation, regardless of which needle is used to create the tract, the entry site should always be checked with 2% fluorescein drop and 10.0 nylon suture is used with or without autologous Tenon's tissue to close any leakage.How to cite this article: Lim KS, Garg A, Cheng J, Muthusamy K, Beltran-Agullo L, Barton K. Comparison of Short-term Postoperative Hypotony Rates of 23-gauge vs 25-gauge Needles in Formation of the Scleral Tract for Baerveldt Tube Insertion into the Anterior Chamber. J Curr Glaucoma Pract 2018;12(1):36-39.

Effect of phacoemulsification on facility of outflow.

PURPOSE: Phacoemulsification has been shown to reduce intraocular pressure (IOP). The mechanism of action is thought to be via increased trabecular outflow facility. However, studies on the relationship between phacoemulsification and outflow facility have been inconsistent. This study intended to examine the change in electronic Schiotz tonographic outflow facility (TOF) and IOP measurements following phacoemulsification. METHODS: Patients who were due to undergo a standard clear corneal incision phacoemulsification with intraocular lens (IOL) implantation, at St Thomas' Hospital, were invited to participate in this study. IOP was measured using Goldmann's applanation tonometer, and TOF was measured by electronic Schiotz tonography at baseline and at 3, 6 and 12 months postoperatively. RESULTS: Forty-one patients were recruited. Tonography data for 27 patients were reliable and available at all time points. Eleven cases had primary open angle glaucoma and cataract, while 16 patients had cataract only. Mean IOP reduced at every time point postoperatively significantly compared with baseline. TOF improved significantly after cataract extraction at all time points (baseline of 0.14±0.06 vs 0.18±0.09 at 3 months, P=0.02 and 0.20±0.09 at 6 months, P=0.003, 0.17±0.07 µL/min mmHg at 12 months, P=0.04). Five contralateral eyes of patients with cataracts only who did not have any intraocular surgery during the follow-up period were used as comparison. Their IOP and TOF did not change significantly at any postoperative visits. CONCLUSION: This is the first study using electronic Schiotz tonography with documented anterior chamber depth and gonioscopy after modern cataract surgery (CS) with phacoemulsification and IOL implantation. We demonstrated that phacoemulsification increases TOF and this fully accounts for the IOP reduction following CS. ISTCRN REGISTRATION NUMBER: ISRCTN04247738.

Twenty-four hour intraocular pressure monitoring with the SENSIMED Triggerfish contact lens: effect of body posture during sleep.

PURPOSE: To determine the difference in relative intraocular pressure (IOP) measured by the SENSIMED Triggerfish (TF) contact lens in flat compared with 30° head-up sleeping positions in patients with progressive primary open-angle glaucoma or normotensive glaucoma, based on recent or recurrent disc haemorrhage. DESIGN: Prospective, randomised, cross-over, open-label comparative study. METHODS: IOP was monitored for 24 hours using TF on two separate sessions. Patients were randomly assigned to sleep flat one night and 30° head-up the other. Outputs in arbitrary units were obtained. Sleep and wake periods were defined as 22:00-6:00 and 8:00-22:00, respectively. Mean TF values during sleep and wake periods and wake-sleep and sleep-wake slopes were calculated for each session. TF output signals were compared between positions. RESULTS: Twelve subjects completed the study. Significant mean positive slopes were noted during the sleep period for both positions (p<0.01). No significant differences in the TF mean values were observed between positions (p=0.51). Six (54%) subjects had mean TF values significantly higher during the flat supine session, while four (36%) subjects had higher values during the head-up session. A significant increase in Goldmann IOP (p=0.001) and TF (p=0.02) measurements were observed after 24 hours of TF wear ('drift phenomenon'). CONCLUSIONS: Sleep position affects IOP as measured by TF in some patients with progressive glaucoma. The upward drift in TF output detected in >50% of the subjects requires further investigation to establish whether the increased output values over time are an artefact induced by the TF or a real change in IOP. TRIAL REGISTRATION NUMBER: NCT01351779.

Aqueous outflow facility after phacoemulsification with or without goniosynechialysis in primary angle closure: a randomised controlled study.

BACKGROUND: Goniosynechialysis (GSL) to remove peripheral anterior synechiae (PAS) alongside standard cataract surgery has potential theoretical advantages, Published randomised trials, however, have not shown conclusive functional benefits and aqueous outflow changes following GSL are unknown. This study aimed to compare electronic Shiøtz tonographic aqueous outflow facility (TOF) following phacoemulsification with or without GSL in patients with primary angle closure (PAC) and PAC glaucoma. Secondary outcomes were changes in intraocular pressure (IOP) and use of glaucoma medications. METHODS: Prospective randomised pilot study of 26 patients on glaucoma medication, with ≥90° PAS and significant lens opacity. Patients were randomised 1:1 to receive phacoemulsification with intraocular lens (IOL) implantation only (phaco) or phacoemulsification with IOL plus GSL (phaco-GSL). RESULTS: Fourteen patients were randomised to phaco-GSL and 12 to phaco alone. TOF increased with phaco-GSL from 0.099±0.07 µL/min/mm Hg to 0.194±0.07, µL/min/mm Hg, p=0.0006, while the phaco group showed no significant change. IOP reduced in both groups, but reduced significantly more following phaco-GSL (46.0%) compared with phaco alone (27.6%, p=0.04). Medication use and extent of PAS only reduced with phaco-GSL, from 0.923±0.86 to 0.384±0.18 medications, p=0.0279, and from 249.2±83.4 to 110.8±53.9° PAS, 6 months postoperatively. No serious adverse events occurred in either group. CONCLUSIONS: Eyes randomised to both surgical groups had similar and good outcomes at 6 months in this pilot study. However, only eyes undergoing GSL combined with standard phacoemulsification had significantly increased TOF, reduced glaucoma medication dependence and PAS postoperatively. GSL should therefore be considered in such patients. TRIAL REGISTRATION NUMBER: NCT00719290, Results.

Flow Test to Predict Early Hypotony and Hypertensive Phase After Ahmed Glaucoma Valve (AGV) Surgical Implantation.

PURPOSE: To assess the validity of a preimplantation flow test to predict early hypotony [intraocular pressure (IOP)≤5 mm Hg on 2 consecutive visits and hypertensive phase (HP) (IOP>21 mm Hg) after Ahmed Glaucoma Valve (AGV) implantation. PATIENTS AND METHODS: Prospective interventional study on patients receiving an AGV. A preimplantation flow test using a gravity-driven reservoir and an open manometer was performed on all AGVs. Opening pressure (OP) and closing pressure (CP) were defined as the pressure at which fluid was seen to flow or stop flowing through the AGV, respectively. OP and CP were measured twice per AGV. Patients were followed for 12 weeks. RESULTS: In total, 20 eyes from 19 patients were enrolled. At 12 weeks the mean IOP decreased from 29.2±9.1 to 16.8±5.2 mm Hg (P<0.01). The mean AGV OP was 17.5±5.4 mm Hg and the mean CP was 6.7±2.3 mm Hg. Early (within 2 wk postoperative) HP occurred in 37% and hypotony in 16% of cases. An 18 mm Hg cutoff for the OP gave a sensitivity of 0.71, specificity of 0.83, positive predictive value of 0.71, and negative predictive value of 0.83 for predicting an early HP. A 7 mm Hg cutoff for the CP yielded a sensitivity of 1.0, specificity of 0.38, positive predictive value of 0.23, and negative predictive value of 1.0 for predicting hypotony. CONCLUSIONS: Preoperative OP and CP may predict early hypotony or HP and may be used as a guide as to which AGV valves to discard before implantation surgery.

Priming the Ahmed Glaucoma Valve: pressure required and effect of overpriming.

PURPOSE: To determine the pressure required to prime an Ahmed Glaucoma Valve (AGV) and determine whether the valve can be damaged by "over-priming pressure." METHODS: Three AGVs, a syringe pump, and a manometer were used to assess priming pressure. Balanced salt solution was pumped through the AGV tube at increasing pressures until a jet of fluid was seen to eject from the AGV, as per manufacturer instructions. This was repeated 3 times for 3 different virgin AGVs giving the "priming pressure." A second experiment used the same experimental set up to determine the "over-priming pressure" on 3 other AGVs. Fluid was pumped through the AGV at increasing pressures until evidence of damage was seen. The valve function was assessed before and after the "over-priming" stress test. Valve function was determined by the closing pressure, which is the pressure at which the valve closes and fluid was no longer seen passing through the valve. RESULTS: The priming pressure in the 3 AGVs was 2844, 3154, and 3051 mm Hg (mean, 3017±158 mm Hg). The maximum pressure generated using the syringe pump was 10,860, 10,343, and 10,860 mm Hg (mean, 10,688±299 mm Hg). No damage was observed in the valve mechanism. AGV closing pressure before the "over-priming" stress test was 8, 6, and 13 mm Hg and after the stress test was 6, 7, and 13 mm Hg. CONCLUSION: This study demonstrates that the priming pressure is consistent at around 3000 mm Hg. In addition, over-priming is not likely to damage or disturb the closing pressure.

Comparison of visual recovery following ex-PRESS versus trabeculectomy: results of a prospective randomized controlled trial.

PURPOSE: To compare the rate of visual recovery after Ex-PRESS implantation versus standard trabeculectomy. PATIENTS AND METHODS: Subjects enrolled in a prospective randomized controlled trial comparing Ex-PRESS to trabeculectomy were analyzed for postoperative changes in visual acuity (VA). Risk factors for visual loss (split fixation, cup-disc ratio, intraocular pressure, visual field mean deviation, and hypotony) were evaluated. RESULTS: Sixty-four subjects were enrolled (33 Ex-PRESS, 31 trabeculectomy). There was no significant difference in mean logMAR VA between groups at baseline or any study visit. VA was significantly reduced up to week 2 following surgery in both the groups. However, by month 1, VA in the Ex-PRESS group was no longer significantly different from baseline (P=0.23) and remained nonsignificant at subsequent visits up to 6 months. In the trabeculectomy group, VA remained significantly lower than baseline at each study visit. At 6 months, 47% of the trabeculectomy eyes compared with 16% of the Ex-PRESS eyes had lost ≥2 Snellen lines (P=0.01). Reasons for VA loss included cataract, central retinal vein occlusion, and diabetic retinopathy, however, in a significant number of cases no cause could be determined. None of the risk factors evaluated were associated with vision loss. CONCLUSIONS: Although there was no difference in mean VA between the Ex-PRESS and trabeculectomy groups at any time point, trabeculectomy eyes were more likely to lose ≥2 Snellen lines. In addition, VA recovered faster in the Ex-PRESS group.

The effect of selective laser trabeculoplasty on aqueous humor dynamics in patients with ocular hypertension and primary open-angle glaucoma.

PURPOSE: To investigate the effect of primary selective laser trabeculoplasty (SLT) on outflow facility and aqueous flow rate in patients with primary open-angle glaucoma or ocular hypertension. METHODS: Eighteen eyes (9 with ocular hypertension and 9 with primary open-angle glaucoma) were included in this prospective noncontrolled study. Patients with intraocular pressures (IOPs)>21 to 35 mm Hg were treated with 360-degree SLT after a baseline measurement of IOP, tonographic outflow facility, and morning aqueous humor production. Electronic Schiøtz tonography was used to measure the outflow facility. The aqueous flow rate was measured by fluorophotometry, and a pneumotonometer was used to measure the IOP. All measurements were repeated at least 3 months after the laser therapy. Paired Student t tests were used to compare aqueous dynamics parameters before and after treatment. RESULTS: The mean age of the study population was 56.7 ± 12.4 years. The IOP decreased significantly (21%) from 24.0 ± 3.0 to 18.9 ± 2.7 mm Hg (P<0.001), whereas tonographic outflow facility increased significantly (55.5%) from 0.09 ± 0.05 to 0.14 ± 0.08 µL/min/mm Hg (P=0.003) 3 months after laser treatment. No statistically significant changes in the production of aqueous humor were found (P=0.46). CONCLUSIONS: Our results show that SLT lowers the IOP by increasing the outflow through the trabecular meshwork, but it has no significant effect on the aqueous flow rate.

Preimplantation Flow Testing of Ahmed Glaucoma Valve and the Early Postoperative Clinical Outcome.

PURPOSE: The Ahmed glaucoma valve (AGV) implant is designed to prevent early postoperative hypotony. There is evidence of variation in hypotony rates in clinical trials which may be due to surgical technique variation, entry site leakage or valve defects from 'over priming'. We describe a simple preimplantation gravity driven test to assess valve function after priming that may reduce hypotony rates. MATERIALS AND METHODS: Retrospective case note review. An in vivo flow test of AGVs, based on the gravity driven test was introduced prior to implantation. The onset and offset of flow through the valve was measured by altering the height of a bottle of balanced saline solution. We rejected the AGV, if there was fluid still flowing at 10 cm (7 mm Hg) or if there was no flow at 17 cm of water (12 mm Hg). The AGV implantation surgery was without mitomycin C, with a 25G needle entry tract, a corneal or scleral patch graft tube cover and without intracameral viscoelastic. RESULTS: Twenty Ahmed valves were implanted in 16 patients between July 2008 and October 2009. Test failure resulted in four AGV being rejected. The mean preoperative pressure was 29 mm Hg (range, 10-57 mm Hg) and the intraocular pressure (IOP) at 7 days postoperatively was 15 mm Hg (range, 3-52 mm Hg). Hypotony, defined as an IOP of less than 5 mm Hg on two consecutive assessments, was present in two eyes (10%). CONCLUSION: In vivo flow testing is an important safety check for the AGV. There are also other mechanisms after implantation that can cause an unexpected high or low IOP. How to cite this article: Jones E, Alaghband P, Cheng J, Beltran-Agullo L, Lim KS. Preimplantation Flow Testing of Ahmed Glaucoma Valve and the Early Postoperative Clinical Outcome. J Current Glau Prac 2013;7(1):1-5.

Intraocular pressure monitoring post intravitreal steroids: a systematic review.

The use of intravitreal (IVT) corticosteroids for treatment of posterior segment diseases has increased significantly over the last decade. A commonly recognized complication of IVT steroids is secondary ocular hypertension (OHT) that can occur immediately secondary to direct intraocular volume increase or weeks to months later as a result of increased outflow resistance. We performed a meta-analysis and found 32% (95% confidence interval, 28.2-36.3) of individuals developed OHT following 4 mg IVT triamcinolone, 66% (50.2-78.8) and 79% (72.2-84.5) following 0.59 and 2.1 mg fluocinolone implant, respectively, and 11% (6.4-17.9) and 15% (9.2-24.3) following 0.35 and 0.7 mg dexamethasone implant, respectively. Risk factors included pre-existing glaucoma, higher baseline intraocular pressure (IOP), younger age, OHT following previous injection, uveitis, higher steroid dosage, and fluocinolone implant. Most cases of OHT can be controlled medically; up to 45% following fluocinolone implant require surgery, however. We suggest a protocol to monitor IOP after IVT steroid injection/implantation that includes checking IOP within 30 minutes after injection, followed by 1 week after IVT triamcinolone and 2 weeks after implant insertion, then every 2 weeks for the first month and monthly for up to 6 months after IVT triamcinolone and dexamethasone implantation and 9 months after fluocinolone implantation.

Comparative human aqueous dynamics study between black and white subjects with glaucoma.

PURPOSE: To compare the baseline aqueous humor dynamics in white Caucasians and patients of African origin with previously untreated primary open-angle glaucoma (POAG) or ocular hypertension (OHT). METHODS: Ninety-one participants were enrolled in this prospective, observational controlled study: 34 black subjects with POAG or OHT, 32 white Caucasian participants with POAG or OHT, and 12 black and 13 white healthy volunteers as the controls. All aqueous humor parameters were taken between 9 AM and 12 noon on the same day. Intraocular pressure (IOP) was measured by pneumatonometer; morning aqueous humor flow rate was measured by fluorophotometry and trabecular outflow facility by electronic Schiøtz tonography. Uveoscleral outflow was calculated by using Goldmann's equation with assumed episcleral venous pressure of 8, 9, 10, and 11 mm Hg. Differences among groups were analyzed with parametric and nonparametric tests and the relationship between aqueous dynamics parameters were evaluated with linear regression analyses. RESULTS: The POAG/OHT groups had similar IOP (white, 24.6 ± 3.0 mm Hg; black, 24.3 ± 4.0 mm Hg; comparison by Holm's sequential Bonferroni method (HBonf): P(HBonf) = 0.51), outflow facility (white, 0.13 ± 0.09 µL/min/mm Hg; black, 0.13 ± 0.07 µL/min/mm Hg; P(HBonf) = 0.87), aqueous flow (white, 2.36 ± 0.63 µL/min; black, 2.35 ± 0.53 µL/min; P(HBonf) = 0.95), and uveoscleral outflow (white, 0.42 ± 1.59 µL/min; black, 0.58 ± 1.17 µL/min; P(HBonf) = 1.78). POAG/OHT groups had significantly higher IOP and lower outflow facility than their healthy counterparts (P < 0.01). Black participants had significant thinner corneas (540 ± 37 µm vs. 564 ± 36 µm) than those of white participants (P = 0.002). CONCLUSIONS: The aqueous humor dynamics of black African and white Caucasian patients with POAG or OHT have no significant differences. However, the significantly thinner corneas of the black patients may be masking potential differences in outflow facility and IOP measurements between the racial groups.

Effect of primary selective laser trabeculoplasty on tonographic outflow facility: a randomised clinical trial.

PURPOSE: To investigate the effect of 180° versus 360° primary selective laser trabeculoplasty (SLT) on tonographic outflow facility and intraocular pressure (IOP). DESIGN: Prospective, single masked randomised clinical trial. PARTICIPANTS: Patients with untreated primary open angle glaucoma or ocular hypertension both with IOP > 21-35 mmHg. METHODS: 40 patients randomly treated with 180° or 360° SLT after baseline tonographic outflow facility (electronic Schiøtz tonography) and IOP measurements were repeated after 1 month. One eye from each patient was randomly selected for analysis. Eight untreated eyes were included as a control group. MAIN OUTCOME MEASURES: Tonographic outflow facility and IOP difference. Responders were defined as having at least a 20% reduction in IOP. RESULTS: Three patients were excluded due to poor tonography. There were 18 eyes in the 180° group and 19 eyes in the 360° group. Tonographic outflow facility increased significantly (180° p = 0.003, 360° p = 0.005) and IOP decreased significantly (180° and 360° p < 0.001) from baseline. There were no significant differences between the two groups as regards the increase in tonographic outflow facility (180° group 37.5%, 360° group 41%, p = 0.23) and decrease in IOP (180° group 24%, 360° group 35%, p = 0.35). There were similar number of responders in 180° group (72%) as compared to 360° group (89.5%, p = 0.23). Tonographic outflow facility and IOP did not change significantly from baseline in the control group (tonographic outflow facility: 8% increase p = 0.48, IOP: 4% decrease p = 0.33). CONCLUSIONS: Primary SLT significantly increased the tonographic outflow facility and decreased IOP in patients with primary open angle glaucoma and ocular hypertension but no statistically significant differences were found between the 360° and 180° groups. The level of IOP reduction due to primary SLT treatment could not be explained by the increase in tonographic outflow facility alone. Clinical trial registration ISRCTN66330584, Current Controlled Trials. 1/11/2006.