Limited transscleral cyclophotocoagulation for silicone oil-induced glaucoma in eyes with good visual potential

Abstract

BACKGROUND

Silicone oil-induced glaucoma is a complex form of secondary glaucoma that develops after vitreoretinal surgery and is often refractory to conventional treatment. The role of limited transscleral cyclophotocoagulation (TSCPC) in eyes with preserved visual potential remains inadequately defined.

AIM

To evaluate the outcomes of limited TSCPC in patients with silicone oil-induced glaucoma and good visual potential.

METHODS

This retrospective study included eyes with visual acuity better than 20/400 and refractory silicone oil-induced glaucoma treated with limited TSCPC (180° treatment, 16-18 laser applications) between 2015 to 2019. Primary outcome measures were visual acuity and intraocular pressure (IOP). Visual acuity success was defined as maintenance of baseline acuity or loss of fewer than two lines. Qualified IOP success was defined as an IOP > 5 mmHg and ≤ 21 mmHg with anti-glaucoma medications (AGMs). Secondary outcomes included the number of AGMs required and treatment-related complications.

RESULTS

Twelve patients (12 eyes) were included, of which three eyes had silicone oil in situ at the time of TSCPC. The median age at presentation was 28.3 years, and the median interval from silicone oil removal (n = 9) to TSCPC was 3.4 months. The median follow-up duration was 21.5 months. Stable or improved visual acuity was observed in 75% of eyes. Median IOP significantly decreased from 29.5 mmHg to 17 mmHg at 3 months and 16 mmHg at 1 year. The median number of AGMs decreased from four to two within 1 year. Mean percentage IOP reduction was 66.7% at 3 months and 46.7% at 6 months and was maintained up to 2 years. Repeat surgery for IOP control was required in 50% of cases. No major adverse events, including hypotony, phthisis bulbi, or severe inflammation, were observed.

CONCLUSION

Limited TSCPC appears to be a moderately effective and safe option for IOP control in patients with silicone oil-induced glaucoma and preserved visual potential, supporting its role as a possible treatment strategy in this challenging condition.

Key Words: Transscleral cyclophotocoagulation; Silicone oil induced glaucoma; Limited transscleral cyclophotocoagulation; Refractory glaucoma; Post vitreoretinal surgery

Core Tip: Silicone oil-induced glaucoma is a challenging secondary glaucoma with limited surgical options, particularly in eyes with preserved visual potential. This study evaluated limited transscleral cyclophotocoagulation (TSCPC) as a minimally invasive treatment approach in this subset of patients. Limited TSCPC provided moderate intraocular pressure control, reduced anti-glaucoma medication burden, and preserved visual acuity in most eyes, with a favorable safety profile. However, the need for repeat interventions underscores the refractory nature of the disease. Limited TSCPC may represent a useful adjunctive treatment option when conventional surgical approaches are not feasible and warrants further evaluation in larger controlled studies.

INTRODUCTION

Silicone oil-associated glaucoma is a relatively common complication following pars plana vitrectomy with silicone oil tamponade, with reported incidence ranging from approximately 2% to more than 50%, depending on factors such as tamponade duration, emulsification, and pre-existing ocular conditions[1,2]. Multiple mechanisms contribute to postoperative elevation of intraocular pressure (IOP), including aphakia, pre-existing glaucoma, scleral buckle placement, neovascular glaucoma, pupillary block, uveitis, peripheral anterior synechiae, steroid response, and mechanical obstruction by lens remnants, residual oil, or pigment dispersion[3,4].

Management typically begins with medical therapy; however, refractory cases often require surgical intervention. Silicone oil removal (SOR) achieves IOP control in approximately 45%-62% of cases, although outcomes depend on the extent of trabecular meshwork damage. Trabeculectomy has demonstrated limited success in this setting, with reported success rates of approximately 15%-50% at 1 year, largely due conjunctival scarring, subconjunctival silicone oil droplets, and postoperative inflammation[3,4]. In contrast, glaucoma drainage devices have shown more consistent outcomes, with success ranging from 62% to 80% over 12-24 months[1,5,6]. Transscleral cyclophotocoagulation (TSCPC) has demonstrated variable success rates of approximately 44%-82% and is generally reserved for refractory cases, often requiring repeat treatments[4,7,8]. Emerging procedures, including Ex-PRESS shunt implantation[9] and minimally invasive glaucoma surgeries such as gonioscopy-assisted transluminal trabeculotomy[10], have shown promising early results but require further validation.

Limited TSCPC, involving 16-18 laser applications over 180°, represents a less invasive alternative that lowers IOP by reducing aqueous humor production. This study evaluates the effectiveness of limited TSCPC in eyes with moderate to good visual potential, including eyes after SOR and those with retained silicone oil. By limiting laser energy delivery, this approach aims to minimize complications such as hypotony and severe inflammation while providing effective IOP control in patients with complex retinal surgical histories[11,12].

MATERIALS AND METHODS

Study design

This retrospective study was conducted at the L V Prasad Eye Institute, Hyderabad, India, after approval by the Institutional Review Board. Medical records of patients diagnosed with silicone oil-induced glaucoma, with or without prior SOR, were reviewed. Inclusion criteria were best-corrected visual acuity of at least 20/400 [logarithm of the minimum angle of resolution (logMAR) < 1.3], IOP > 21 mmHg despite maximal medical therapy, and treatment with limited TSCPC between January 2015 and December 2019. Patients with visual acuity worse than 20/400 and those with less than 2 months of postoperative follow-up were excluded.

Principle and technique of TSCPC

An 810-nm semiconductor diode laser system (OcuLight^® SL; IRIDEX Corporation, Mountain View, CA, United States) coupled with a G-probe was used for TSCPC. The G-probe was positioned at the limbus to direct laser energy posteriorly toward the ciliary body. Laser energy is absorbed by melanin within the pigmented epithelium of the ciliary processes, resulting in coagulative necrosis of the ciliary epithelium and stroma, thereby reducing aqueous humor production[11].

All procedures were performed under peribulbar anesthesia with placement of a lid speculum. Laser power was initiated at 1200 milliwatts (mW) and increased in increments of 100-200 mW up to a maximum of 2500 mW. If an audible “pop”, suggestive of intraocular uveal micro-explosion, was heard, the power was reduced by 100 mW and treatment was continued at the lower setting. Laser duration was fixed at 2000 milliseconds per application. A total of 16-18 laser applications were delivered over the inferior 180° of the ciliary body while avoiding the 3 o’clock and 9 o’clock meridians.

Data collection and outcome measures

Collected data included patient age, sex, associated ocular conditions, indications for retinal surgery, dates of retinal surgery and SOR (when applicable), prior glaucoma surgeries, logMAR visual acuity, IOP measured by Goldmann applanation tonometry, lens status, vertical cup-to-disc ratio, and the number of anti-glaucoma medications (AGMs). Additional data included the date of TSCPC, postoperative complications, and the need for subsequent glaucoma interventions. Macular optical coherence tomography was performed when clinically indicated.

Postoperative assessments were conducted at 1 month, 3 months, 6 months, 1 year, and 2 years after TSCPC and included evaluation of visual acuity, IOP, and AGM use. Visual acuity success was defined as stable vision (within one line of baseline) or improvement of more than two lines during follow-up. Qualified IOP success was defined as an IOP > 5 mmHg and ≤ 21 mmHg with the use of topical AGMs. Because complete medication-free IOP control is often unrealistic in this patient population, success was defined as qualified (cumulative) success[13]. Secondary outcome measures included the number of AGMs and postoperative complications. Eyes that failed to meet success criteria, required additional glaucoma surgery, or developed severe complications such as phthisis bulbi or loss of light perception were classified as failures.

Statistical analysis

Statistical analysis was performed using STATA software version 14 (StataCorp, College Station, TX, United States). Owing to the small sample size, continuous variables are presented using median and interquartile range. A mixed-effects model with a random intercept at the eye level was used to account for repeated measurements over time and intra-subject correlation in analyses of visual acuity, IOP and AGM use. Given the limited sample size, analyses were primarily descriptive and intended to characterize temporal trends rather than establish definitive inferential conclusions. The mixed-effects framework also enabled inclusion of all available observations despite variability in follow-up duration, thereby accommodating unbalanced repeated measures without imputation, as missing data were minimal. Categorical variables are presented as proportions. A two-sided P value < 0.05 was considered statistically significant. For pairwise comparisons across follow-up visits, a Bonferroni-adjusted P value < 0.007 was considered statistically significant.

RESULTS

Over a 5-year period, 12 eyes from 12 patients met the inclusion criteria for limited TSCPC for refractory silicone oil-induced glaucoma (Table 1). Demographic and clinical characteristics are summarized in Table 2. The median age at presentation was 28.3 years [interquartile range (IQR): 15-34 years], and most patients were male (83%). Lens status included aphakia in 8 eyes, pseudophakia in 3 eyes, and phakic in 1 eye. Nine patients had previously undergone SOR, whereas 3 eyes retained intraocular silicone oil. Among eyes that underwent SOR, the median time between SOR to TSCPC was 3.4 months. The median follow-up duration was 21.5 months (IQR: 14.2-31.6 months). In the 3 eyes with retained silicone oil, the median duration from silicone oil injection to TSCPC was 18 months (IQR: 5-97 months).

Table 1 Details of the 12 patients undergoing limited transscleral cyclophotocoagulation.

Pt. no	Age, sex	One-eyed status	Lens status, silicone oil status	IOP pre in mmHg	IOP LFU in mmHg	Vision pre as logMAR	Vision LFU as logMAR	AGM pre	AGM LFU	Repeat surgery for IOP	Visual success	IOP success
1	19, M	Yes	Aphakic, SOR	30	10	1.2	1.3	2	5	Yes	Yes	No
2	14, F	Yes	Aphakic, SO in situ	48	17	1.2	1.2	1	2	Yes	Yes	No
3	10, M	No	Aphakic, SO in situ	18	32	1.0	2.2	4	3	No	No	No
4	31, M	No	Aphakic, SO in situ	48	17	1.3	1.8	5	1	Yes	No	No
5	15, M	No	Phakic, SOR	16	16	1.2	1.2	3	2	No	Yes	Yes
6	53, M	Yes	Pseudophakic, SOR	40	14	0.6	0.7	4	1	No	Yes	Yes
7	20, M	Yes	Aphakic, SOR	29	4	1.1	0.9	5	2	Yes	Yes	No
8	38, M	No	Pseudophakic, SOR	17	50	1.3	1.5	4	5	No	No	No
9	37, M	No	Pseudophakic, SO in situ	15	17	0.6	0.7	5	0	No	Yes	Yes
10	33, M	Yes	Aphakic, SOR	32	25	1.0	0.7	5	2	Yes	Yes	Yes
11	34, M	No	Aphakic, SOR	26	19	0.6	0.6	4	2	No	Yes	Yes
12	29, F	No	Aphakic, SOR	58	26	1.3	1.1	6	5	Yes	Yes	No

AGM: Anti-glaucoma medication; F: Female; IOP: Intraocular pressure; LFU: Last follow up; LogMAR: Logarithm of the minimum angle of resolution; M: Male; Pt. no: Patient number; SO: Silicone oil; SOR: Silicon oil removal.

Table 2 Demographic and clinical details, n (%).

Parameter	Value
Median age at TSCPC in years	28.3 (15-34)
Sex as male: Female	10:2
One-eyed patients	5 (41.7)
Eyes with prior SOR	9 (75)
Non-glaucoma intraocular surgeries	2 (1-2)
Duration between VR surgery and high IOP in months	4.8 (3.8-11.1)
Pre-operative glaucoma surgery	2 (16.7) both AGV
Lens status as Phakic: Pseudophakic: Aphakic	1:3:8
Interval between SOI and TSCPC in months, n = 12	9 (5-19)
Interval between SOI and TSCPC in months, n = 3 without SOR	18 (5-97)
Interval between SOI and TSCPC in months, n = 9 with SOR	7 (5-12)
Duration between VR surgery and SOR in months, n = 9	3 (2.1-3.9)
Interval between SOR and TSCPC in months, n = 9	3.4 (2.3-5.5)
Pre-operative vision as logMAR	1.06 (0.6-1.2)
Pre-operative IOP in mmHg	29.5 (17-40)
Pre-operative CDR	0.8 (0.5-0.9)
Pre-operative AGM	4 (3-5)
Follow-up duration in months	21.5 (14.2-31.6)

Data are presented as n (%) or median (interquartile range). AGM: Anti-glaucoma medication; AGV: Ahmed glaucoma valve; CDR: Cup-to-disc ratio; IOP: Intraocular pressure; IQR: Interquartile range; LogMAR: Logarithm of the minimum angle of resolution; SOI: Silicone oil injection; SOR: Silicone oil removal; TSCPC: Transscleral cyclophotocoagulation; VR: Vitreoretinal.

Visual acuity

The median baseline logMAR visual acuity was 1.06 (IQR: 0.6-1.2). At final follow-up, visual acuity success was achieved in 75% (9/12) of eyes; visual acuity remained stable in 3 eyes and improved by more than one line in 6 eyes (Figure 1). Changes in visual acuity following TSCPC are summarized in Table 3. Three patients (cases 3, cases 4, and cases 8) experienced loss of more than two lines of vision secondary to uncontrolled IOP and were classified as failures. Among the 9 eyes with visual acuity success, 5 eyes (case 1, cases 2, cases 7, cases 10 and cases 12) required repeat surgical intervention for IOP control. Pairwise comparisons demonstrated no statistically significant change in visual acuity over the follow-up period.

Figure 1 Trend in visual acuity and intraocular pressure following limited transscleral cyclophotocoagulation. Black line, right Y-axis: Visual acuity; Blue line, left Y-axis: Intraocular pressure. IOP: Intraocular pressure; LogMAR: Logarithm of the minimum angle of resolution.

Table 3 Trend of change of visual acuity, intraocular pressure and anti-glaucoma medication after transscleral cyclophotocoagulation, mean ± SE.

Timepoint	Vision as logMAR	IOP in mmHg	Number of AGMs
Pre-operative	1.03 ± 0.10	31.4 ± 3.0	4.0 ± 0.4
Day 1	1.15 ± 0.10	18.4 ± 3.1	2.6 ± 0.4
Week 1	0.93 ± 0.12	18.7 ± 3.8	2.6 ± 0.5
Week 5	0.95 ± 0.10	20.3 ± 3.1	2.4 ± 0.4
Month 3	1.14 ± 0.11	21.2 ± 3.6	2.8 ± 0.5
Month 6	1.02 ± 0.11	23.8 ± 3.2	3.1 ± 0.5
Year 1	1.21 ± 0.11	18.8 ± 3.4	2.2 ± 0.5
Year 2	1.16 ± 0.11	23.5 ± 3.4	2.9 ± 0.5

AGM: Anti-glaucoma medication; IOP: Intraocular pressure; LogMAR: Logarithm of minimum angle of resolution.

IOP

Median IOP decreased from 29.5 mmHg (IQR: 17-40 mmHg) at baseline to 17 mmHg (IQR: 10-30 mmHg) at 3 months and to 16 mmHg (IQR: 13-25 mmHg) at 1 year. Trends in IOP reduction following TSCPC are shown in Figure 1 and Table 3. Compared with baseline, IOP was significantly reduced at multiple postoperative time points, including postoperative day 1, week 1, week 5, and year 1, while postoperative IOP values remained comparable across follow-up visits. The probability of qualified IOP success following limited TSCPC was 66.7% ± 13.6% at 3 months and 46.7% ± 15.4% at 6 months, with this effect maintained up to 2 years.

AGMs

The median number of AGMs decreased from 4 (IQR: 3-5) preoperatively to 2 (IQR: 1.3-3) at 1 year. Trends in AGM use before and after TSCPC are summarized in Table 3. The number of AGMs was significantly reduced at several postoperative time points, including postoperative day 1, week 5, and year 1, compared with baseline values, while postoperative medication requirements remained similar over time.

Complications and failure

Minor complications were infrequent and included isolated cases of intercalary staphyloma, adherent leucoma, pigment dispersion (including deposition on the lens and near the optic disc), limbal stem cell deficiency, and peripheral anterior synechiae. Most eyes did not develop identifiable complications. No major adverse events, including hypotony, phthisis bulbi, or severe inflammation, were observed.

Visual acuity failure occurred in 3 patients, whereas IOP failure was observed in 7 eyes at final follow-up. Six patients required repeat surgery for IOP control. Of these, 3 underwent repeat TSCPC, with 1 eye subsequently achieving IOP control with a single AGM. The remaining 3 eyes underwent Ahmed glaucoma valve implantation at 29 months, 6 months, and 3 months after TSCPC, respectively, and all were classified as failures at final follow-up. These findings underscore the refractory nature of silicone oil-induced glaucoma.

Subgroup analysis comparing eyes with prior SOR (n = 9) and eyes with retained silicone oil (non-SOR, n = 3) demonstrated comparable postoperative IOP outcomes between groups, with median IOP stabilizing at 17 mmHg in both. The success rate was 44.4% in the SOR group and 33.3% in the non-SOR group. Median IOP reduction showed substantial variability in both groups. AGM requirements decreased in both cohorts, with a greater reduction observed in the non-SOR group. Visual outcomes were generally more stable or improved in the SOR group, whereas greater variability was noted in the non-SOR group. Repeat surgical interventions were more frequently required among failures in the SOR group.

DISCUSSION

Managing silicone oil-induced glaucoma remains a significant clinical challenge[2]. In the present study, limited TSCPC demonstrated moderate efficacy in controlling IOP in eyes with silicone oil-induced glaucoma and preserved visual potential. Qualified IOP success was achieved in 46.7% of eyes at 6 months and maintained up to 2 years. Median IOP decreased from 29.5 mmHg preoperatively to 16 mmHg at 1 year, accompanied by a reduction in AGMs from a median of 4 to 2. Visual acuity was maintained or improved in 75% of eyes, and no major vision-threatening complications were observed. However, 50% of eyes required repeat surgical intervention for IOP control, underscoring the complex and refractory nature of this condition.

In most cases, IOP decreases following SOR[14]. However, persistent elevation of IOP may occur because of trabecular meshwork scarring or retained silicone oil droplets. In eyes at high risk for recurrent retinal detachment, silicone oil is often retained in situ[15]. In our cohort, 75% of eyes had undergone prior SOR, whereas 25% retained silicone oil at the time of treatment. Although comparable postoperative IOP reduction was observed in both groups, differences in outcomes likely reflect heterogeneity in the underlying mechanisms of glaucoma. Eyes in the SOR group may represent chronic trabecular dysfunction following prior surgical intervention, whereas eyes with retained silicone oil may have persistent mechanical obstruction or inflammatory mechanisms contributing to IOP elevation[3,16]. The slightly higher success rate observed in the SOR group should be interpreted cautiously because of the small sample size. Overall, these findings emphasize the complex pathophysiology of silicone oil–induced glaucoma and highlight the need for larger stratified studies to better define outcomes in these subgroups. Kaplan-Meier survival curves for the overall cohort (Figure 2A) and subgroup analyses according to prior SOR status (Figure 2B) are presented.

Figure 2 Kaplan-Meier analyses of qualified intraocular pressure success. A: Probability of qualified intraocular pressure success over time in the entire cohort, with numbers at risk displayed below the curve. Kaplan-Meier analysis demonstrated qualified intraocular pressure success rates of approximately 45%-50% at 1-2 years, declining to approximately 20%-25% at longer follow-up; B: Comparison of qualified intraocular pressure success between eyes with prior silicone oil removal and eyes with retained silicone oil. Subgroup analysis demonstrated a steeper early decline in intraocular pressure success in the non-silicone oil removal group, with an early success rate of approximately 33%, compared with 70%-75% in the silicone oil removal group. PriorSOR: Prior silicon oil removal.

Conventional conjunctival-based glaucoma procedures, including trabeculectomy and glaucoma drainage device implantation, are often complicated by conjunctival scarring, chronic inflammation, and subconjunctival silicone oil droplets, all of which increase the risk of surgical failure. Singh et al[5] reported trabeculectomy success rates of 47% at 3 months and 36.9% at 1 year following silicone oil-related glaucoma. These rates are lower than those observed with limited TSCPC in our series, wherein success rates were 66.7% at 3 months and 46.7% at 1 year.

Glaucoma drainage devices generally provide higher success rates than trabeculectomy or TSCPC after SOR. In our cohort, 3 eyes underwent valve implantation following TSCPC, and all were ultimately classified as failures. Implantation of large drainage devices may also be technically challenging in these eyes. Gupta et al[6] reported a 48% complication rate associated with larger implants, including sight-threatening complications in 22% of cases. In a separate study of eyes with retained silicone oil[17], Ahmed glaucoma valve implantation achieved a 70% success rate in 47 eyes but was associated with a 36% complication rate. Reported complications included hypotony (8%), motility disturbances (8%), tube-corneal touch (6%), retinal detachment (2%), and plate exposure (2%). Silicone oil-related complications, including tube blockage and migration of oil into the subconjunctival space, also contributed to surgical failure. The presence of retained silicone oil was identified as a significant risk factor for AGV failure (risk ratio = 3.43; P = 0.04)[17]. Consequently, glaucoma drainage devices may be less desirable in eyes with retained intraocular silicone oil.

Limited TSCPC offers several practical advantages. It is minimally invasive, technically straightforward, associated with rapid postoperative recovery, and feasible even in eyes with scarred conjunctiva or retained silicone oil. The procedure may also be safely repeated when necessary. In contrast, conventional TSCPC involving treatment of all four quadrants carries a higher risk of hypotony, phthisis bulbi, and permanent visual loss[8], and is therefore generally reserved for eyes with poor visual potential. In our series, limited TSCPC involving 180° with 16-18 laser applications resulted in no cases of hypotony or phthisis, supporting its safety profile in eyes with useful vision.

Rotchford et al[12] evaluated limited TSCPC in 43 eyes with baseline visual acuity better than 20/60, including 5 eyes with silicone oil-induced glaucoma. In that study, 30.6% of patients experienced loss of more than two lines of visual acuity, primarily because of glaucoma progression. Among the 5 eyes with silicone oil-induced glaucoma, 3 (60%) lost more than two lines in vision. In comparison, only 25% (3/12) of eyes in our series experienced a similar degree of visual decline. Notably, 5 eyes in our cohort represented the patients’ only seeing eyes, highlighting the limited availability of long-term visual outcome data in such high-risk cases and emphasizing the clinical relevance of our findings.

This study has several limitations. First, the sample size was small (n = 12), reflecting the rarity of silicone oil-induced glaucoma in eyes with preserved visual potential, thereby limiting statistical power and generalizability. Second, the retrospective design, heterogeneity of the cohort (including eyes with and without SOR and varying lens status), and variable follow-up durations limit interpretation of outcomes. Finally, this was a single-arm observational study without direct comparison to alternative interventions such as Ahmed glaucoma valve implantation, repeat SOR, or medical therapy alone. Therefore, the findings should be interpreted cautiously. Larger prospective controlled studies are needed to validate these results and establish the comparative effectiveness of limited TSCPC in this challenging clinical setting.

CONCLUSION

Given the challenges and potential complications associated with conventional surgical approaches, limited TSCPC appears to be a viable treatment option for refractory silicone oil-induced glaucoma, including eyes with retained intraocular silicone oil, with the goal of preserving useful vision. Following SOR, glaucoma drainage implants may still be considered a primary surgical option because of their relatively favorable success rates. However, in cases of implant failure or when conventional surgery is not feasible, limited TSCPC may serve as a safe and effective adjunctive, temporizing, or secondary intervention.