Real world outcomes of selective laser trabeculoplasty as primary treatment for glaucoma in Enugu Nigeria: a retrospective study

Abstract

Background

Selective Laser Trabeculoplasty (SLT) is a non-invasive procedure for managing open-angle glaucoma by reducing intraocular pressure (IOP). While effective as a primary treatment in various populations, data on its efficacy in sub-Saharan Africa, particularly Nigeria, are limited. This study evaluates SLT as a primary treatment for open-angle glaucoma in Enugu, Nigeria, addressing a regional gap in real-world outcomes.

Methods

A retrospective chart review was conducted on 93 eyes of 50 patients who underwent SLT as primary treatment at The Eye Specialists Hospital, Enugu, Nigeria, between 2019 and 2021. Patients with open-angle glaucoma (primary, juvenile, or normal-tension) and a minimum 3-month follow-up were included. Kaplan Meier analysis was used to assess survival rates of SLT alone and SLT with additional treatment therapy overtime. Success was defined as an IOP reduction of ≥ 3 mmHg without additional intervention or ≥ 20% from baseline IOP. Data were analyzed using SPSS version 26, with statistical significance set at p < 0.05.

Results

Mean baseline IOP was 17.0 ± 5.1 mmHg. Post-SLT, mean IOP decreased to 12.6 ± 3.3 mmHg (25% reduction) at 3 months, 12.3 ± 3.0 mmHg (25%) at 6 months, 11.9 ± 3.1 mmHg (25%) at 12 months, 12.3 ± 2.9 mmHg (22%) at 24 months, and 13.9 ± 3.3 mmHg (21%) at 36 months (all p < 0.05). Eyes with higher baseline IOP showed greater reductions up to 24 months. The number of antiglaucoma medications increased from 0 at baseline to 0.6 ± 1.0 at 12 months and 1.5 ± 0.9 at 36 months (p < 0.001). Success rates for SLT alone (without additional therapy) were 86% at 3 months, 83% at 6 months, 67% at 12 months, 54% at 24 months, and 43% at 36 months. Success rates for SLT with additional therapy were 87% at 3 months, 84% at 6 months, 80% at 12 months, and 64% at 36 months.

Conclusion

SLT is an effective primary treatment for reducing IOP in Nigerian patients with open-angle glaucoma, particularly those with higher baseline IOP, with minimal need for additional medications or surgery over 36 months. These findings support SLT’s role in resource-limited settings, though prospective studies are needed to confirm long-term outcomes.

Background

Glaucoma is a progressive, multifactorial disease characterized by damage to the optic nerve, often associated with elevated intraocular pressure (IOP) [1]. After glaucoma diagnosis, the clinician is mostly concerned with lowering the IOP to safe limits where further damage is averted using available treatment options [2, 3]. The Treatment option adopted is usually one which would efficiently reduce the IOP with maximal safety considering the severity, type and age of patient amidst other factors [4].

The use of topical medication has traditionally remained first-line treatment option in many countries including the United States of America despite recent advances in laser and surgical techniques in glaucoma management [5]. However, issues of poor adherence, cost, unavailability of drugs and side effects has persistently plagued the effective use of medical therapy in glaucoma management especially in developing countries [6].

Laser trabeculoplasty introduced more than 20years ago featured the use of argon laser trabeculoplasty which produced lower IOPs and better visual fields compared to fellow eyes first treated with topical medication in the Glaucoma Laser Trial [7, 8]. Selective laser trabeculoplasty (SLT) got introduced in 1995 and has been found to produce better IOP outcomes with less damage to the trabecular meshwork and fewer side effects [9, 10]. SLT is an advanced laser procedure often used for managing primary open-angle glaucoma (POAG) [11]. It is a non-invasive technique that selectively targets the trabecular meshwork to improve aqueous humor outflow reducing IOP, which is essential in halting glaucoma progression [12, 13].

The efficacy of SLT in lowering intraocular pressure has been found to range from 6.9 to 38.9% among patients with open angle glaucoma [10, 14, 15]. Recent large clinical trials compare the effectiveness of SLT as first-line treatment option for glaucoma compared to topical medications and have found better outcomes with SLT [16, 17]. Gus-Gazzard and his colleagues reported findings of the Laser in Glaucoma and Ocular Hypertension (LiGHT) trial [16], a multicenter randomized controlled trial comparing selective laser trabeculoplasty to topical medication as a first-line treatment for ocular hypertension and open angle glaucoma. It was found that glaucoma progression occurred in a lower proportion of those who has SLT first compared to those who had topical anti-glaucoma medications first. Furthermore, over 36months, IOP control was better in the laser-first group and the overall cost of treatment was lower in the laser group with lower number of medications required. Hence the LiGHT study results support and strongly advocates for the use of SLT as primary treatment for POAG and ocular hypertension. Over two-third (68.2%) of participants in the LiGHT trial were European whites hence it may be argued that the findings can be generalized only among such patients. Existing literature on SLT in African-derived people have also reported mean IOP reductions at 12 months ranging from 30 to 40% [14, 18–20], with 80% -90% of patients maintaining IOP reduction of 20% 1 year after treatment.

SLT is gaining acceptance as a primary treatment in glaucoma however barriers to its widespread use such as initial cost of procedure, equipment availability and training deficiencies may hinder implementation [21]. Few published Studies in Nigeria have assessed the efficacy of selective laser trabeculoplasty as first line treatment in glaucoma management. To the best of our knowledge no published study on the subject exist in south eastern Nigeria which has been found to have a high burden of glaucoma in the country [22]. This is however the first clinical study in south eastern Nigeria exploring the use of SLT in treatment-naïve eyes of glaucoma patients. The objective of this study is to assess the efficacy of SLT as primary treatment in clinical care of black patients with glaucoma in south east Nigeria using data collected from patients’ medical records.

Methods

Study design and setting

This retrospective chart review evaluated the efficacy of Selective Laser Trabeculoplasty (SLT) as a primary treatment for open-angle glaucoma in patients treated at The Eye Specialists Hospital, Enugu, Nigeria, from 2019 to 2021. The study aimed to assess SLT’s efficacy in reducing intraocular pressure (IOP).

Study participants

Eligible patients’ case notes were retrieved from hospital laser records for data collection. Inclusion criteria encompassed patients with open-angle glaucoma, including primary open-angle glaucoma (POAG), juvenile open-angle glaucoma (JOAG), or normal-tension glaucoma (NTG), with a minimum follow-up of three months. The sample size of 93 eyes from 50 patients was determined by the availability of complete medical records that met the study criteria within the study period. All eyes were treatment-naïve eyes. Patients with less than three months of follow-up were excluded. Baseline characteristics included age, sex, glaucoma severity (assessed using mean deviation on automated Humphrey visual field), SLT treatment details. Severity of glaucoma was classified using Humphrey mean deviation values as mild (-0.01 to -6.00), moderate (-6.01 to -12.00), severe (-12.01 and worse) [23, 24]. Baseline IOP was taken as the last IOP measurement before SLT.

Intervention

SLT was performed using a Q-switched, frequency-doubled 532 nm Nd: YAG laser (Selecta Duet, Lumenis, Israel) with a 400 μm spot size and 3-nanosecond pulse duration. The protocol involved 100–120 applications across 360° of the trabecular meshwork of the anterior chamber angle, with 25–30 spots per quadrant at an energy level of 0.8–1.2 mJ. Patients received a pretreatment drop of Brimonidine or Apraclonidine 0.2%.

Outcome measures

Primary outcomes were changes in IOP and the number of antiglaucoma medications post-SLT. Secondary outcomes included treatment success rates over time and additional glaucoma procedures post-SLT. Outcomes were assessed at 3, 6, 9, 12, 18, 24, and 36 months, using time windows of ± 1–2 weeks due to the retrospective design. Success was defined as either: (1) IOP reduction of ≥ 3 mmHg without additional interventions or (2) IOP reduction of ≥ 20% from baseline. Intraocular pressure at each visit was done using the Gatt Applanation tonometer (GAT).

Statistical analysis

Data were analyzed using the Statistical Package for Social Sciences (SPSS) software version 26.0 (SPSS, Inc., Chicago, IL, USA). Continuous variables were summarized as means and standard deviations, and categorical variables as frequencies and percentages. Group comparisons used Student’s T-test for continuous data. Survival analysis was done using the Kaplan Meier survival function. Statistical significance was set at P < 0.05. Due to the retrospective nature of the study, IOP measurements were not standardized across patients, and no formal power calculation was performed to determine the sample size, as it was based on available records.

Ethical considerations

Ethical approval was obtained from the Ethical Committee of the College of Medicine, University of Nigeria Teaching Hospital (UNTH), Ituku-Ozalla Enugu (Reference number: UNTH/HREC/2024/04/951). The Committee waived the requirement for informed consent due to the retrospective nature of the study, which utilized existing medical records. No personal identifiers of participants were collected or included in the analysis. The study adhered to good clinical practice guidelines and the principles of the Declaration of Helsinki.

Results

Baseline characteristics

A total of 93 eyes from 50 patients (24 males [48%], 26 females [52%]) were included, with a mean age of 51.8 ± 16.5 years (range: 12–82 years). Forty-six (96%) of the patients were of igbo ethnicity. All eyes had a minimum follow-up of 3 months. Diagnoses included primary open-angle glaucoma (POAG; 49 eyes [53%]), normal-tension glaucoma (NTG; 38 eyes [40%]), and juvenile open-angle glaucoma (JOAG; 6 eyes [7%]). Glaucoma severity was mild to moderate in 84 eyes (90%) and advanced in 9 eyes (10%). (Table 1).

Table 1.

Baseline characteristics of patients which had SLT

Characteristic	N (%)
Mean age (SD) years	51.8(16.5)
Sex, n (%)
Male	24(48%)
Female	26(52%)
Ethnicity
Igbo	48(96%)
Others	2(4%)
Diagnosis, n (%)
POAG	49(53%)
NTG	38(40%)
JOAG	6(7%)
Glaucoma severity, n (%)
Mild-moderate	84(90%)
Advanced	9(10%)

Intraocular pressure changes over time

The mean baseline IOP in 93 eyes was 17.0 ± 5.1mmHg (range: 12.0–40.0 mmHg). Post-SLT, mean IOP decreased significantly at all time points (P < 0.05). At 3, 6, 12, 24, and 36 months, mean IOP values were 12.6 ± 3.3 mmHg (93 eyes, 25% reduction), 12.3 ± 3.0 mmHg (75 eyes, 25%), 11.9 ± 3.1 mmHg (66 eyes, 25%), 12.3 ± 2.9 mmHg (23eyes, 22%), and 13.9 ± 3.3 mmHg (14eyes, 21%), respectively. (Table 2)

Table 2.

Intraocular pressure changes over time

Time	N	Mean IOP (mmHg) ± SD (median)	Mean IOP Drop ± SD	Mean % IOP Drop ± SD	P-value
Pre-treatment	93	17.0 ± 5.1 (16.0)	-	-	-
3 months	93	12.6 ± 3.3 (12.0)	4.3 ± 4.0	25.1 ± 12.8	< 0.001*
6 months	75	12.3 ± 3.0 (12.0)	4.9 ± 4.1	25.3 ± 18.6	< 0.001*
12 months	66	11.9 ± 3.1 (12.0)	4.9 ± 4.9	25.4 ± 16.9	< 0.001*
24 months	23	12.3 ± 2.9 (13.0)	3.9 ± 3.4	22.0 ± 18.7	< 0.001*
36 months	14	13.9 ± 3.3 (14.0)	3.6 ± 3.0	21.3 ± 17.4	0.016*

*P-value < 0.05 was considered significant

Sub-analysis showed baseline IOP was significantly higher in eyes with advanced glaucoma (9 eyes; 21.1 ± 10.6 mmHg) than in mild-moderate glaucoma (84 eyes; 16.5 ± 4.2 mmHg; P = 0.010). Both groups showed significant IOP reductions at 3 and 12 months and 24 months though advanced glaucoma eyes had a lower mean IOP (10.7 ± 2.1 mmHg) compared to mild-moderate (12.1 ± 3.1 mmHg; P = 0.008) at 12months and 24 months (10.4 ± 2.5mmHg vs. 12.7 ± 2.9mmHg). All of those with advanced glaucoma were lost to follow up at 36months.

Antiglaucoma medication use

At baseline all eyes were not on any antiglaucoma medications. Post-SLT, the mean number of medications increased significantly (P < 0.05): 0.2 ± 0.5 (range: 0–2) at 3 months, 0.3 ± 0.7 (range: 0–2) at 6 months, 0.6 ± 1.0 (range: 0–2) at 12 months, 1.2 ± 0.8(range: 0–2) at 24 months, and 1.5 ± 0.9 (range: 0–3) at 36 months (Table 3).

Table 3.

Mean number of antiglaucoma medications over time

Time	Number of eyes	Mean ± SD (Median)	Range	P-value
Baseline	93	0.0 ± 0.0
3 months	93	0.2 ± 0.5 (0.0)	0–2	< 0.001
6 months	75	0.3 ± 0.7 (0.0)	0–2	< 0.001*
12 months	66	0.6 ± 1.0 (0.0)	0–2	< 0.001*
24 months	23	1.2 ± 0.8 (1.0)	0–2	< 0.001*
36 months	14	1.5 ± 0.9 (1.0)	0–3	0.002*

*p < 0.05 statistically significant

Success rates

Kaplan-Meier survival analysis estimated cumulative success rates based on IOP reduction ≥ 20% from baseline with and without additional therapy (SLT alone). Success rates for SLT alone (without additional therapy) were 86% at 3 months, 83% at 6 months, 67% at 12 months, 54% at 24 months, and 43% at 36 months. Success rates for SLT with additional therapy were 87% at 3 months, 84% at 6 months, 80% at 12 months, and 64% at 36 months. Figure 1 illustrates the survival curve over time.

Fig. 1.

Kaplan-Meier survival curve showing success rates of SLT alone and SLT with additional intervention

The mean difference in pressure drop between right and left eyes in those with bilateral SLT was − 1.4mmHg ± 3.6 (SD), correlation coefficient = -0.24. Right eyes only of those with bilateral SLT was combined with only eyes of those who had SLT on one eye to compare between individuals the average pressure drop difference, average pressure drop difference was − 2.8mmHg ± 2.2(SD), correlation coefficient = 0.71.

Additional glaucoma procedures

During follow-up, 13 eyes (14%) received repeat SLT, and 1 eye (1%) underwent trabeculectomy after 12 months post-SLT.

Discussion

This study, the first to evaluate Selective Laser Trabeculoplasty (SLT) as a primary treatment for open-angle glaucoma in southeastern Nigeria, demonstrates its effectiveness in reducing intraocular pressure (IOP) over 36 months. The mean IOP decreased from 17.0 ± 5.1 mmHg at baseline to 11.9 ± 3.1 mmHg at 12 months (25% reduction) and 13.9 ± 3.3 mmHg at 36 months (21% reduction), with all reductions statistically significant (P < 0.05). Success rates for SLT alone (without additional therapy) were 86% at 3 months, 83% at 6 months, 67% at 12 months, 54% at 24 months, and 43% at 36 months. Success rates for SLT with additional therapy were 87% at 3 months, 84% at 6 months, 80% at 12 months, and 64% at 36 months. The need for antiglaucoma medications increased from 0 at baseline to 1.5 ± 0.9 at 36 months, and only approximately14% of eyes required repeat SLT, with 1% needing trabeculectomy.

The IOP reductions observed in this study are consistent with, but slightly lower than, those reported in other African and African-derived populations. The West Indies Glaucoma Laser Study (WIGLS) reported a 12-month IOP drop of 6.4–8.5 mmHg among Afro-Caribbeans with higher baseline IOP (20.9–26.8 mmHg) [18]. Similarly, a prospective study in Egypt found a 7.4 mmHg reduction with a baseline IOP of 26.8 mmHg [25, 26], and Melamed et al. reported a 7.7 mmHg drop [15]. A South African retrospective study with a baseline IOP of 27.07 mmHg achieved a 13-mmHg reduction [24, 27]. The lower baseline IOP in our study (17.0 mmHg) likely explains the smaller reductions, as higher pre-treatment IOP is associated with greater SLT efficacy [25, 27, 28]. In contrast, a Western Nigerian study with a baseline IOP of 15.4 mmHg reported smaller reductions (3.5 mmHg at 3 months (22.7%) and 2.8 mmHg at 6 months (18.1%) [26, 29], suggesting regional variations in response.

The increase in antiglaucoma medication use (0.6 ± 1.1 at 12 months, 1.5 ± 0.9 at 36 months) aligns with findings from Goosen et al., who reported a rise from 0 to 1.7 medications at 12 months with a higher baseline IOP (27.07 mmHg) [24, 27]. The lower medication use in our study may reflect the milder baseline IOP, reducing the need for aggressive supplementation. Success rate in our study (54% at 24 months) is comparable to the findings of Weinand et al. (50% failure at 24 months) [28, 30] and Bovell et al. [29, 31], though our high loss to follow-up (85% at 36 months) may affect long-term estimates. A randomized controlled trial using SLT and 0.5% timolol for treatment of glaucoma in Tanzania reported lower estimates of success in the SLT group as 61% success rate was observed at 1year while in the Timolol group, success rate at one year was almost half of that SLT (31%) [30, 31]. This study recorded a similar success rate of 67% at one year (without additional intervention) and 80.0% with additional therapy. This suggests that SLT with additional intervention may increase success rates overtime. The low rate of additional procedures (13.9% repeat SLT, 1.1% trabeculectomy) supports SLT’s role as a sustainable primary treatment, consistent with the LiGHT trial’s findings of reduced surgical needs [16].

SLT’s effectiveness in this Nigerian population, particularly for patients with higher baseline IOP, supports its use as a primary treatment in resource-limited settings. The minimal need for additional procedures and moderate increase in medication use suggest SLT can reduce treatment burden compared to lifelong topical therapy, which is often plagued by cost, availability, and adherence issues in sub-Saharan Africa [6, 21]. The ability to repeat SLT without permanent trabecular meshwork damage [13] further enhances its suitability for low-resource settings, where access to incisional surgery is limited [22, 31]. These findings advocate for increased adoption of SLT in Nigeria, particularly in regions with high glaucoma prevalence.

Obtaining and maintaining selective laser trabeculoplasty devices in Sub-Saharan Africa calls for concern as cost of acquiring the machine is relatively high discouraging intending users who may not afford initial cost requirements. The machines are usually sourced from the producing company’s representatives who require payment of about 70–80% of the total machine cost before delivery. On maintaining the machines and access to repair assistance, these representatives are not usually able to provide such services and there’s generally a dearth in ophthalmic devices technicians on this side of the world hence these machines are flown back to the manufacturers who may take about 6 months to get the machines fixed leaving the owners and users handicapped until the return of the machine.

This study has several limitations. The retrospective design led to significant loss to follow-up (85% at 36 months), potentially introducing bias in long-term success rate estimates. IOP measurements were not standardized across patients or time points, as they were not taken at consistent times of day or by the same examiner, which may affect reliability. The absence of a formal power calculation, due to the retrospective reliance on available records, limits the ability to assess statistical power. The sample size (93 eyes of 50 patients) is comparable to similar studies [20, 26, 29], but a larger, prospective study could provide more robust data. Additionally, the study did not assess visual field progression or quality of life, limiting its scope to IOP outcomes.

The authors also acknowledge the existence of major unquantifiable bias resulting from potential selection bias arising from significant loss to follow up after 3months. For example, only about 15% of the population at baseline were available at last follow up (36months) introducing some form of bias in that the IOPs of these 15% of eyes were still compared to the baseline of which 85% of its constituents were already lost to follow up. In the comparison of subgroups, after 12months, most of the participants in the mild-moderate glaucoma group were already lost to follow up hence no reliable comparisons could be made with the very little counts in one group. This unquantifiable bias was also occurred as potential selection bias in number of medications recorded on repeated attendances. Some patients who receive SLT are based on referrals and once they get the procedures done and they get their first and likely second follow up visit are most likely to return to their main place of care hence are lost to follow up. Others who feel better relief from their symptoms or get better IOPs at initial visit may decide to pause further visits. Hence not much can be done to ensure sustainability in follow up in this center.

Future research should focus on prospective, randomized controlled trials in southeastern Nigeria to confirm SLT’s efficacy and assess long-term outcomes, including visual field preservation and patient quality of life. Standardizing IOP measurements and reducing loss to follow-up through better patient retention strategies could enhance reliability. Exploring the cost-effectiveness of SLT in Nigeria, as suggested by the LiGHT trial [16], could further support its integration into national glaucoma management protocols. Studies comparing SLT with topical medications in this population would also clarify its role as a first-line treatment.

Conclusion

Selective Laser Trabeculoplasty (SLT) is an effective primary treatment for open-angle glaucoma in Nigerian patients, achieving significant intraocular pressure (IOP) reductions over 36 months, particularly in eyes with higher baseline IOP. With a cumulative success rate of 72.3% at 12 months and minimal need for additional medications or surgery, SLT offers a sustainable option for glaucoma management in resource-limited settings like southeastern Nigeria. These findings support its integration into local treatment protocols to address the high burden of glaucoma.

Abbreviations

IOP

Intraocular Pressure

JOAG

Juvenile Open-Angle Glaucoma

LiGHT

Laser in Glaucoma and Ocular Hypertension

NTG

Normal-Tension Glaucoma

NSAIDs

Non-Steroidal Anti-Inflammatory Drugs

POAG

Primary Open-Angle Glaucoma

SD

Standard Deviation

SLT

Selective Laser Trabeculoplasty

SPSS

Statistical Package for the Social Sciences

UNTH

University of Nigeria Teaching Hospital

WIGLS

West Indies Glaucoma Laser Study

Author contributions

All authors contributed to the study’s conception and design. Data collection and analysis were performed by N.N. K, S.O, C.O, N.U. and O. J. S. The manuscript was drafted by N.K and S.O and all authors reviewed and approved the final manuscript. The corresponding author is N. N.K.

Funding

Not applicable.

Data availability

The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.

Declarations

Ethics approval and consent to participate

Ethical approval was obtained from the Ethical Committee of the College of Medicine, University of Nigeria Teaching Hospital (UNTH), Ituku-Ozalla Enugu (Reference number: UNTH/HREC/2024/04/951). The Committee waived the requirement for informed consent due to the retrospective nature of the study, which utilized existing medical records. No personal identifiers of participants were collected or included in the analysis. The study adhered to good clinical practice guidelines and the principles of the Declaration of Helsinki.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.