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 Table of Contents  
ORIGINAL ARTICLE
Year : 2020  |  Volume : 58  |  Issue : 3  |  Page : 159-161

Early results of SubCyclo laser in glaucoma patients visiting a tertiary care hospital in South India: A pilot study


Department of Glaucoma, Sankara Eye Hospital, Coimbatore, Tamil Nadu, India

Date of Submission15-Mar-2020
Date of Acceptance01-May-2020
Date of Web Publication14-Sep-2020

Correspondence Address:
Dr. Surabhi Abbagani
Department of Glaucoma, Sankara Eye Hospital, Sathy Road, Sivanandapuram, Coimbatore - 641 035, Tamil Nadu
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/tjosr.tjosr_21_20

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  Abstract 


Purpose: To study the safety and effectiveness of SubCyclo (subliminal transscleral cyclophotocoagulation [TSCPC] – Vitra 810, Quantel Medical) laser procedure for patients with various subtypes of glaucoma. Methodology: This pilot study was conducted in a tertiary eye care hospital in South India from October 2019 to December 2019. The study included ten eyes of nine patients who were diagnosed with different types of glaucoma and received subliminal TSCPC under local anesthesia. The laser settings were customized based on the patients' intraocular pressure (IOP). The patients were followed up after 1 week, 1 month, and 2 months after the laser procedure. Results: Ten eyes of nine patients were treated with subliminal TSCPC and were followed up 2 months of the procedure. The mean age of the patients was 63.33 years. The mean preoperative IOP was 31 mm Hg, which reduced to 20.7 mmHg 1 week after the procedure. At 1 month, the average IOP was 19.3 and 17.3 mmHg at 2 months. The mean number of antiglaucoma medications used was 3 before the laser intervention, which reduced to 2.8 following the treatment. In our pilot study using SubCyclo laser, we observed a 33.22% drop in the IOP from the baseline after 1 week and 44.19% reduction in IOP at the 2nd month follow-up with a single laser session. Conclusions: This study concludes that a satisfactory decrease in IOP could be achieved by SubCyclo laser procedure in the early postoperative visits with a low-risk profile.

Keywords: Intraocular pressure, refractory glaucoma, SubCyclo


How to cite this article:
Abbagani S, Sasidharan A, Angadi P, Pradeep B. Early results of SubCyclo laser in glaucoma patients visiting a tertiary care hospital in South India: A pilot study. TNOA J Ophthalmic Sci Res 2020;58:159-61

How to cite this URL:
Abbagani S, Sasidharan A, Angadi P, Pradeep B. Early results of SubCyclo laser in glaucoma patients visiting a tertiary care hospital in South India: A pilot study. TNOA J Ophthalmic Sci Res [serial online] 2020 [cited 2020 Sep 21];58:159-61. Available from: http://www.tnoajosr.com/text.asp?2020/58/3/159/294977




  Introduction Top


One of the main causes of irreversible blindness in the world is glaucoma.[1] Initially, when the intraocular pressures (IOPs) are not controlled by medical therapy, surgical interventions (e.g. trabeculectomy with or without antimetabolites and drainage implants) are tried. Minimally invasive glaucoma surgeries (MIGSs) have been documented to have a better safety profile; however, long-term results are yet to be studied.[2] Cyclodestructive procedures such as transscleral cyclophotocoagulation (TSCPC) are performed when both medical and surgical treatments fail to lower the IOP. This procedure, however, is reserved for refractory glaucoma as it can lead to complications such as loss of vision, pain, severe hypotony, and phthisis bulbi.[3] The conventional cyclodestructive procedures lower IOP by destroying of ciliary body epithelium and stroma, thereby decreasing the aqueous production. The new SubCyclo diode (810 nm wavelength) laser is a novel technique that lowers the IOP by nonthermal, photodestruction of the pigmented ciliary body epithelium, as well as increases the uveoscleral outflow.[4] Unlike the continuous-wave TSCPC where a high-intensity laser is used, SubCyclo subliminal technology (Vitra 810, Quantel Medical) finely controls thermal elevation in the target pigmented ciliary body epithelium by delivering energy in consecutive microsecond pulses, with an alternative on and off mechanism. This rest period allows the tissues to cool and prevent coagulative necrosis and collateral damage.

The aim of this pilot study was to evaluate the safety and efficacy of the SubCyclo diode laser in the treatment of different types of glaucoma.


  Methodology Top


This pilot study was conducted in a tertiary care eye hospital in South India from October 2019 to December 2019. The study was conducted in accordance to the Declaration of Helsinki, after obtaining the clearance from the institutional ethical committee. Patients having poor control of IOP (>21 mmHg) on maximal tolerable medical therapy with or without previous filtering surgery were included in the study. Patients diagnosed with primary open angle glaucoma, pseudoexfoliation glaucoma, neovascular glaucoma, pigmentary glaucoma, angle recession glaucoma, and steroid-induced glaucoma were included. Patients who denied consent, who previously underwent TSCPC, who had recent ocular infection, and who had scleral thinning were excluded from the study. Written informed consent was taken from each patient before the procedure.

The SubCyclo laser treatment was performed by a single surgeon under local anesthesia. 3–5 mL of 2% lignocaine hydrochloride 100 mg/5 mL was injected in the peribulbar space. Ciliary body was identified and marked after performing transillumination. Eye speculum is put, and laser is given. The power of laser and the time of laser delivery were customized for each patient. The power ranged from 2000 to 2200 mW, and the duration of laser delivery ranged from 50 to 100 s. The duty cycle was set at 31.3% (“on” time, 0.5 ms; “off” time, 1.1 ms). Therefore, the energy delivered to each eye was tailored for each patient.

The laser probe is a unique needle-like design with a glass ball tip for accurate positioning. The probe is placed perpendicularly over the sclera after identifying and marking the ciliary body (approximately 3 mm behind the limbus) by transillumination. The probe was moved in a painting-like fashion from 10.30 to 2.30 clock hours superiorly and 3.30 to 8.30 clock hours inferiorly, avoiding the 9 and 3 clock positions. In case of the presence of previous functioning filtering bleb, the laser was avoided in that hemisphere. Postoperatively, topical steroids and cycloplegics were given, and all the patients were advised to continue their antiglaucoma medications.

Patients were followed up 1 week, 1 month, and 2 months following the laser. On each visit, best-corrected visual acuity, slit lamp biomicroscopy, IOP measurement by Goldmann applanation tonometer, fundus examination, and number antiglaucoma medications to maintain IOP below 21 mHg were recorded.


  Results Top


Ten eyes of nine patients were treated with subliminal TSCPC. The mean age of the patients was 63.33 years. Three were females and six were males. Our study using the SubCyclo laser with the 31.3% duty cycle showed a 33.22% drop in the IOP from the baseline after 1 week and 44.19% reduction in IOP at the 2nd month follow-up with a single laser session [Table 1].
Table 1: Patient demographics and distribution of glaucoma diagnosis

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The mean IOP dropped significantly (P < 0.05) from baseline 31 and 17.3 mmHg in the 2nd month follow-up.

The mean number of medications was decreased from 3 to 2.8 after treatment.

One eye presented with mydriasis and posterior synechiae after the procedure, and one eye had iritis 1 week after the laser which subsided in the next follow-up visit. None of the patients developed hypotony or other major complications.


  Discussion Top


Treatment modalities for glaucoma include various options, such as medical therapy, laser procedures, MIGS, as well filtering and valve surgeries. SubCyclo laser is an emerging laser procedure which allows energy to be absorbed only in the targeted pigmented tissues, thereby preventing gross structural damage to the cellular structures. The unwanted inflammatory effects and coagulative necrosis induced by the conventional laser diode CPC can be avoided and desired reduction in the IOP can be achieved.

Our prospective study using SubCyclo laser with 31.3% duty cycle showed a significant fall in the IOP from mean 31 mmHg at the baseline to 20.7 mmHg after 1 week, 19.3 mmHg at 1 month, and 17.3 mmHg at the 2nd month of follow-up. On analyzing the results, we observed that there was a rapid fall in IOP by 33.22% at the end of 1st week, which maintained at 1 month follow-up (30.37%) and further reduced by 44.19% at 2nd month of follow-up.

In our study, we had customized the laser settings by giving greater energy and longer treatment duration to the eyes with higher IOP. Therefore, the reduction in IOP was better appreciated in eyes with higher pretreatment IOP than the eyes with lower pretreatment IOP.

A review article by Sanchez et al. proposed the ideal laser parameters using MicroPulse TSCPC (IRIDEX Corp., Mountain View, CA, USA) which works on the same principle as SubCyclo.[5] The reviewed articles allowed the lowering of the laser parameters to a range between 112 and 150 J of total energy, for an IOP reducing effect of around 30% with minimal to no complications. A study by Benhatchi et al. used SubCyclo laser with fixed settings of 2000 W power, treatment duration of 100 s, and duty cycle of 25% for all patients. They noticed that IOP reduction was more significant in the group of patients with an IOP less than 30 mmHg.[6]

This drastic fall in IOP could be attributed to the lack of inflammation induced in the eye due to the SubCyclo laser and uveoscleral outflow when compared to the conventional TSCPC. Benhatchi et al. explained the absence of anatomical changes in the ciliary body and presence of suprachoroidal fluid, detected by ultrasound biomicroscopy following SubCyclo. This confirms the hypothesis that uveoscleral outflow is enhanced following treatment.[6] Another study by Liu et al. proved the increase in the uveoscleral outflow following laser treatment by using tracer particles on monkey eyes.[7]

Traditional TSCPC is not advised for eyes with visual potential and is generally reserved for eyes with refractory glaucomas with painful blind eyes. This was due to severe complications such as vision loss, hypotony, and phthisis bulbi. SubCyclo is a much safer laser as it prevents collateral damage. In our study, we noticed two phakic patients with distorted pupils and posterior synechiae.

The mean number of antiglaucoma medications used was 3 before the laser intervention which reduced to 2.8 following the treatment. None of the patients experienced pain during the procedure or in the immediate postoperative period. This can be explained by the fact that the energy is delivered only during the “on” phase of the laser, therefore reducing the absolute amount of energy.


  Conclusions Top


Subliminal TSCPC has a good safety profile and easy learning curve and is effective in lowering IOP in patients with refractory glaucoma. Longer follow-up period is needed to comment on the long-term effects of treatment, need for retreatment, and rate of late complications. From our study, we can conclude that SubCyclo laser can be tried on patients with different types of glaucoma, who have poor IOP control in spite of medical and surgical intervention, as an alternative to surgical treatment and who are allergic to anti glaucoma medications. Target IOP levels can be achieved by carefully adjusting the laser settings as per the patients' requirements. This noncomparative case series is limited by a small sample size and a short follow-up time.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Quigley HA, Broman AT. The number of people with glaucoma worldwide in 2010 and 2020. Br J Ophthalmol 2006;90:262-7.  Back to cited text no. 1
    
2.
Arriola-Villalobos P, Martínez-de-la-Casa JM, Díaz-Valle D, Fernández-Pérez C, García-Sánchez J, García-Feijoó J. Combined iStent trabecular micro-bypass stent implantation and phacoemulsification for coexistent open-angle glaucoma and cataract: A long-term study. Br J Ophthalmol 2012;96:645-9.  Back to cited text no. 2
    
3.
Schlote T, Derse M, Rassmann K. Efficacy and safety of contact transscleral diode laser cyclo-photocoagulation for advanced glaucoma. J Glaucoma 2001;10:294-301.  Back to cited text no. 3
    
4.
Liu GJ, Mizukawa A, Okisaka S. Mechanism of intraocular pressure decrease after contact transscleral continuous-wave Nd:YAG laser cyclophotocoagulation. Ophthalmic Res 1994;26:65-79.  Back to cited text no. 4
    
5.
Sanchez FG, Peirano-Bonomi JC, Grippo TM. Micropulse transscleral cyclophotocoagulation: A hypothesis for the ideal parameters. Med Hypothesis Discov Innov Ophthalmol 2018;7:94-100.  Back to cited text no. 5
    
6.
Benhatchi N, Bensmail D, Lachkar Y. Benefits of SubCyclo laser therapy guided by high-frequency ultrasound biomicroscopy in patients with refractory glaucoma. J Glaucoma 2019;28:535-9.  Back to cited text no. 6
    
7.
Liu GJ, Mizukawa A, Okisaka S. Mechanism of intraocular pressure decrease after contact transscleral continuous-wave Nd:YAG laser cyclophotocoagulation. Ophthalmic Res 1994;26:65-79.  Back to cited text no. 7
    



 
 
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