Year : 2000 | Volume
: 48 | Issue : 4 | Page : 295--300
Contact trans-scleral laser cyclophotocoagulation treatment for refractory glaucomas in the Indian population
V Gupta, HC Agarwal
Dr. Rajendra Prasad Centre for Ophthalmic Sciences, New Delhi, India
Dr. Rajendra Prasad Centre for Ophthalmic Sciences, New Delhi
Purpose: This study aimed to evaluate the clinical efficacy of contact diode trans-scleral cyclophotocoagulation (TSCPC) for treatment of refractory glaucomas.
Method: Fifty two eyes of 52 patients, (post-penetrating keratoplasty glaucoma: 16 eyes; adherent leucoma with secondary glaucoma: 8 eyes; aphakic glaucoma: 6 eyes; neovascular glaucoma: 6 eyes; narrow angle glaucoma: 6 eyes; and other secondary glaucomas: 10 eyes) were followed up from 3.5 -18 months (average 12 months) after TSCPC. The treatment parameters using the contact G probe were - energy: 3-4J; area: 40 spots spread over 360°; site: 1.2-1.5 mm posterior to limbus. Retreatments (22 eyes; 42%) were given whenever intraocular pressure (IOP) exceeded 22 mmHg despite maximum tolerable topical therapy.
Results: IOP decreased from a baseline of 44.7 (± 7.3) mmHg to 15 (± 3.7) mmHg at first week and was 15.2 ± (8.2) mmHg at the last follow up. Successful control of IOP (<22mmHg) occurred in 30 (58%) eyes after a single treatment and in 48 (92%) eyes following retreatment. Complications included reduction in visual acuity from light perception (LP) only to no light perception (NLP) in two eyes and phthisis bulbi in one eye.
Conclusion: Contact trans-scleral diode laser cyclophotocoagulation is effective in lowering IOP in eyes with intractable glaucoma with few side effects in Indian subjects.
|How to cite this article:|
Gupta V, Agarwal H C. Contact trans-scleral laser cyclophotocoagulation treatment for refractory glaucomas in the Indian population.Indian J Ophthalmol 2000;48:295-300
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Gupta V, Agarwal H C. Contact trans-scleral laser cyclophotocoagulation treatment for refractory glaucomas in the Indian population. Indian J Ophthalmol [serial online] 2000 [cited 2020 Apr 9 ];48:295-300
Available from: http://www.ijo.in/text.asp?2000/48/4/295/14840
Currently contact diode trans-sderal cyclophotocoagulation (TSCPC) is a widely used alternative to cyclocryotherapy and continuous wave Nd: Yag cyclophotocoagulation due to its better ergonomics and fewer side effects. Histologic studies have shown that diode laser trans-sderal application produces blanching and shrinkage of ciliary processes on gross examination and on light microscopy, ciliary body necrosis with disruption and separation of the ciliary epithelium.[2, 3] This study was carried out in 52 eyes with refractory glaucoma to evaluate the effects of contact diode TSCPC with regard to IOP reduction, and stabilization of visual acuity and to study the possible complications in Indian subjects.
Materials and Methods
Fifty two eyes of 52 patients who underwent TSCPC using diode laser between December 1997 and June 1999 were included in this study. The procedure was recommended to preserve residual vision or relieve pain in patients who had been found refractory to maximum tolerable medical therapy and surgery or alternative laser treatments. However, patients who had previous cyclodestructive procedures were excluded. Only patients with a minimum of three months' follow up were included for analysis.
After explaining the procedure and its potential complications, informed consent was obtained. Patients recruited for the procedure underwent baseline examination including a detailed history and a full ophthalmic examination. The ophthalmic examination consisted of measurement of Snellen visual acuity, slitlamp biomicroscopy, and applanation tonometry. Patients with scarred cornea where applanation tonometry results were fallacious were excluded. Patients were followed up at weekly intervals for one month, monthly intervals till sixth month, and three-monthly thereafter. At each follow-up visit visual acuity, IOP and slitlamp examination findings were recorded.
All TSCPSs were performed under a peribulbar block with anaesthetic mixture of 2% lidocaine hydrochloride and 0.5% bupivicaine except for one 13-year-old boy who was treated under general anaesthesia. A lid speculum was used to separate the eyelids. 4% topical xylocaine drops were instilled to further reduce the pain and with the patient in supine position laser spots were applied 1.2-1.5 mm posterior to the corneoscleral limbus using contact G-Probe (IRIS Medical instruments. Inc., Mountain View, CA). All treatments were performed in the operating room. Treatment was begun at 1.5 W and increased to 2W till a popping sound was heard. This sound indicated tissue disruption and hence the power was reduced to just below the level at which the pop was heard. Treatment consisted of 40 applications of 1.5-2W energy applied for 2 seconds each over 360° of the limbus, thus resulting in power delivery of 3-4J per spot. The same parameters were used for retreatment.
Post-treatment, all patients received topical dexamethasone 0.1% drops four times a day for two weeks. Cycloplegics and nonsteroidal anti-inflammatory eye drops were administered to patients with prolonged inflammation and pain. Six patients complained of moderate to severe pain during the procedure; the pain subsided the following day without any additional treatment. Topical anti-glaucoma medications timolol 0.5%, dipivefrin 0.1% and pilocarpine 2% were started in a stepwise fashion whenever IOP was seen to rise. If adequate IOP control was not achieved by one month after the last laser treatment despite topical antiglaucoma medications, a repeat laser procedure was performed. The retreatment was performed for 360° in a manner similar to the primary treatment. Patients receiving retreatment within one month of the last follow up were excluded from the study.
Overall change in IOP was calculated from comparison between the mean prelaser IOP and that at the last follow up. Wilcoxon sign rank test was used to estimate the difference between the mean IOP values before treatment and at each time period of follow up. Treatment failure was defined as IOP 22 mmHg on two successive visits despite topical anti-glaucoma medications and a maximum of 4 retreatment sessions. Success was defined as IOP < 22 mmHg (with or without topical medication) till the last follow up, so long as not more than 4 retreatments were needed.
There were 24 female and 28 male patients in the study and the mean age was 34 ± 15 years. The mean follow up was 11.9 ± 3.4 months (range 3.5 - 18 months). With time the number of patients reporting to follow up declined and 12 patients completed the 18-month follow up [Table:1]. None of the patients in this study had had previous cyclodestructive procedure in the affected eye.
Based on age the patients were divided into two groups - less than 40 years (26 patients) and more than or equal to 40 years (26 patients). In the later group 6 patients required retreatment, over an average follow up period of 12 months. In the former group, 16 patients needed retreatment and 10 of them needed more than one retreatment.
The mean baseline IOP was 44.7 ± 7.3 mmHg. Twenty eyes had IOP > 44 mmHg and 32 eyes had IOP 44 mmHg; retreatment was needed in 14 eyes with IOP > 44 mmHg and 8 eyes with IOP 44 mmHg (p<0.005).
The IOP was controlled at <22 mmHg in 48 (92%) eyes (with or without treatment) during the first week of follow up. The number of these eyes declined to 42 (80%) in the second week and 39 (75%) in the third week, 33 (63.4%) in the first month and 29 (55.7%) in the second month. All the 12 patients seen at the 18-month follow up had an IOP < 22 mmHg without any anti-glaucoma medication.
The IOP was controlled at < 22 mmHg in 48 eyes (92%). Of these, 28 patients did not require any medication, 16 patients were controlled on topical timolol maleate 0.5% alone and 4 were controlled on combination of topical timolol 0.5% and pilocarpine 2%. The remaining 4 patients whose IOP could not be controlled despite four retreatments were designated as treatment failures [Figure:1]; they were offered alternative surgical treatment.
The most common indication for treatment was post-penetrating keratopasty glaucoma [n =16 (30.7%)] [Table:3].
All patients in this group presented with long-standing graft failure. The next most common indication was adherent leucoma with secondary glaucoma,[n = 8 (15.3%)], followed by 6 (11.5%) each of aphakic, neovascular and narrow angle glaucoma. The miscellaneous group consisted of post-traumatic glaucoma (n=4), silicone oil glaucoma (n=2), fibrous downgrowth (n=2), and pseudophakic glaucoma (n=2). [Table:2] shows the results in each diagnostic group. The mean pretreatment IOP was highest in neovascular glaucoma (51 mmHg), followed closely by the narrow angle glaucoma group (50 mmHg), and adherent leucoma with secondary glaucoma group. (45 mmHg) [Table:2]. However, more patients in the adherent leucoma with secondary glaucoma group (6/8; 75%) required retreatment
In this series 22 eyes (42%) required retreatment two times in 12 eyes, three times in 6 eyes, and four times in 4 eyes. In the remaining 30 eyes treatment was given only once and till the last follow up these 30 eyes had controlled IOP with or without topical therapy. The repeat treatments were given at an average of 2.8 ± 0.9 months after the first treatment. In 18 of the 22 retreated eyes, IOP was <22 mmHg at their last follow up, but in four eyes IOP remained uncontrolled and in all four of them repeat treatments were needed.
Visual acuity did not change in 50 patients; in two patients vision reduced from LP to NLP [Table:3]. This occurred two weeks after cyclodiode photocoagulation, and these patients had an uncontrolled IOP after TSCPC. In 8 patients with NLP the procedure was done only for relief of pain. Postoperatively all patients had relief of pain till their last follow up.
One patient with a large overhanging filtering bleb of previous trabeculectomy with mitomycin-C developed flattening of the bleb at 4-months follow up. We attribute this to the decreased ciliary body function along with the scarring effect of the conjunctival burns in the area surrounding the bleb.
We undertook this study in 52 Indian patients with refractory glaucoma to see the effects of contact transscleral diode laser cyclophotocoagulation. As a referral center we found a large number of patients with an advanced stage of glaucoma and due to the potential risks involved in the drainage implant surgery, TSCPC was considered and evaluated.
Previous histopathological studies have showed that though scleral transmission of energy from diode laser is only marginally less than that of Nd: Yag laser, the diode laser (810 nm) energy is absorbed three times more by melanin in the ciliary body than the Nd: Yag laser (1064 nm). Hence, for a given amount of energy absorption by the ciliary body, less diode laser energy is needed. Moreover, compared to continuos wave Nd: Yag laser the diode laser is small, portable, cheap and hence more ergonomic. However, this study was not designed to compare diode TSCPC with Nd: Yag laser or any other cyclodestructive technique.
Another histopathological study on human cadaver eyes has demonstrated the graded effect of contact diode laser TSCPC on ciliary body-mild whitening of ciliary processes at 2-3J energy; intense whitening of the pars plicata at 4-5J energy; explosive tissue damage at higher than 5J energy. Though we did not titrate the IOP lowering with the energy levels used, we found 3-4 J to be optimum.
The average age of the patients in our study was 34 years ± 15 years. The lower age has been found to adversely affect the success rate of cycloablative procedures. In this study we found that patients younger than 40 years required a significantly higher number of retreatments (p <0.005). The baseline IOP also was found to have a statistically significant effect on the success of treatment; a significantly higher number of patients (14/20) with IOP >44 mmHg required retreatments (p<0.005).
In this study 22 (42%) patients required retreatment despite 360° TSCPC given in the first session to all eyes. Retreatment was done when the IOP could not be reduced <22 mmHg with maximum tolerable medical therapy; this usually occurred at an average of 2.8 ± 1 months after the first treatment.
However, there were a lot of time variations in retreatment; in some patients retreatment was necessary earlier than two months, and some did not need it till 12 months. This individual variation could not be explained by any of the variables such as patient's age, preoperative diagnosis, preoperative IOP or duration of glaucoma. Similar high incidence of retreatment is reported by Bloom et al.
Histologic studies of eyes with failed cyclodiode after a single treatment have been attributed to preservation of some ciliary processes though reversal of laser induced increase in uveoscleral outflow has also been postulated to explain the rise of IOP after failed cyclodiode therapy.
The 92% success rate in this series is comparatively higher than in the Western studies [Table:4]. One possible explanation could be better uptake of diode laser energy by the greater pigment content of ciliary epithelium in the Indian population compared to the Caucasian eyes. However, the effect of 360° treatment as the initial treatment can not be ruled out. Except for Bloom et al and Wong et al other authors [Table:4] have treated 270° or less in the first sitting. We chose to do 360° TSCPC because the patients presenting to us had long-standing intractable glaucoma with very high pretreatment IOP. The high success rate in this study can also be explained by Gaasterland's observation that outflow mechanisms are increasingly damaged and less able to compensate in advanced glaucomas, so that even a small change in inflow can result in a dramatic IOP change. This is well exemplified by our finding of a significant IOP reduction (66%) in all patients with clinical success [Table:2].
None of the patients in this study had visual acuity better than 3/60. Except for two patients, visual acuity remained preserved in all patients till the last follow up, but none of them showed any improvement in visual acuity. Postoperatively no patient complained of pain severe enough to require systemic analgesics. This is in contrast to other cyclodestructive procedures, such as cyclocryotherapy.
No patient developed sympathetic ophthalmia in this series, though one eye (1.92%) developed phthisis bulbi 3 months after a single treatment. This is similar to another published report. The low rate of phthisis following cyclodiode compares favorably with that of cyclocryotherapy (12%) and that following cycloYAG(5%).
Forty applications of cyclodiode over 360° with 3-4 J energy per spot were effective in lowering IOP and relieving pain in refractory glaucoma. But the need for retreatment was high. This study also confirms the relative safety of diode laser cycloablation in Indian patients. We recommend further studies to evaluate the role of cyclodiode in glaucomatous eyes with better visual prognosis.
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