|Year : 2013 | Volume
| Issue : 1 | Page : 8-13
Outcome of transpupillary diode laser photocoagulation for retinal diseases
Olukorede O Adenuga, Nanbam G Bupwatda
Department of Ophthalmology, Jos University Teaching Hospital, Jos, Plateau State, Nigeria
|Date of Web Publication||18-Oct-2013|
Olukorede O Adenuga
Department of Ophthalmology, Jos University Teaching Hospital, Jos - 930001, Plateau State
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Background: Diode lasers have been used in ophthalmic practice for several years. They are useful in the management of vasoproliferative retinopathies and have been shown to be comparable in efficacy to the argon laser.
Aim: To report on the outcome of transpupillary diode laser treatment for retinal diseases.
Patients and Methods: A retrospective study carried out using the case files of patients that had retinal diode laser photocoagulation between June 2011 and May 2012 at the Jos University Teaching Hospital, Jos, Nigeria. Information retrieved included patients' age, sex, diagnosis, indication for retinal laser photocoagulation, prelaser and postlaser visual acuity (VA), best corrected VA, and operative complications.
Results: A total of 31 eyes of 21 patients had transpupillary retinal laser photocoagulation during the study period. The commonest indication for retinal laser photocoagulation was proliferative diabetic retinopathy (PDR), and this was seen in 16 eyes (52%). Six eyes (19%) had both PDR and clinically significant macular edema (CSMO), while 3 eyes had CSMO only. Other indications were retinal vein occlusion (RVO) with secondary neovascularization (four eyes), proliferative sickle cell retinopathy (one eye), and traumatic retinal tear (one eye). Following laser therapy in those with diabetic retinopathy, VA improved by at least a line in 6 eyes, remained the same in 13 eyes, and deteriorated in 2 eyes. Neovascular regression was observed in 13 eyes and resolution of macular edema in 3 eyes. In the eyes with RVO, neovascular regression was observed in two eyes.
Conclusion: Transpupillary diode laser photocoagulation was beneficial in the treatment of retinal diseases. Fibrovascular proliferation with significant fibrous tissue component was, however, associated with poor response to laser treatment in proliferative retinopathies.
Keywords: Diode laser, panretinal photocoagulation, proliferative diabetic retinopathy
|How to cite this article:|
Adenuga OO, Bupwatda NG. Outcome of transpupillary diode laser photocoagulation for retinal diseases. Ann Nigerian Med 2013;7:8-13
| Introduction|| |
Semiconductor diode lasers have been employed in ophthalmic therapy since 1988.  They are compact, affordable, economical, and easy to maintain. , Hence, they are a favoured option for ophthalmologists purchasing new platforms particularly in developing countries. , The infrared emission wavelength (790-840 nm) has the biophysical advantages of less scattering and good transmission through media opacities and nuclear sclerotic cataract, together with negligible absorption within macular xanthophyll. , However, it is not as effectively absorbed, with only 20% absorption of infrared wavelength (800 nm) compared with 95% absorption of blue wavelength (514 nm).  Therefore, higher energy levels and longer exposure are required to achieve similar photocoagulation effects.  This results in greater patient discomfort. 
Retinal laser photocoagulation is effective in the management of retinal breaks and vasoproliferative retinopathies like proliferative diabetic retinopathy (PDR), ischemic central or branch retinal vein occlusion (RVO) and retinopathy of prematurity.  The department commenced retinal laser photocoagulation for retinal diseases following the installation of a NIDEK 3300 diode laser machine (NIDEK Co. Ltd, Japan) in the eye clinic in May 2011. Herein is a review of the cases that had transpupillary diode laser photocoagulation over a period of 1 year.
| Patients and Methods|| |
A retrospective study of 31 eyes of 21 patients that had retinal laser photocoagulation between June 2011 and May 2012 was carried out. The case files of the patients were identified from the ophthalmology clinic register. Patients' age, sex, findings on ocular examination, and diagnosis were documented. Examination included visual acuity (VA) assessment with refraction, slitlamp examination, intraocular pressure measurement and dilated fundoscopy. Fundus examination involved slitlamp biomicroscopy with the Mainster wide field laser lens (Ocular instruments, USA) and color retinal photography with the Opto angiocam ADS 1.3 FA (Opto Electronica S/A, Sao Paulo, Brazil). These were done at baseline, at 4 weeks and at 3 monthly intervals postlaser treatment [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9] and [Figure 10]. Examination findings at the last follow-up visit were then compared with the findings at baseline. Patients that were not seen at or after 3 months following laser treatment, those that did not complete the treatment sessions, and those that were unable to receive adequate laser photocoagulation were excluded from the analysis of treatment outcome. The presence of neovascularization of the disc, neovascularization elsewhere, preretinal hemorrhage, vitreous hemorrhage, fibrous proliferans, tractional retinal detachment, and clinically significant macular edema (CSMO) as defined in the Early Treatment Diabetic Retinopathy Study,  were recorded at baseline and at subsequent evaluations.
|Figure 1: Inferior hemiretinal vein occlusion, fibrovascular proliferation developed later on the disc|
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|Figure 2: Same eye in figure 1 showing residual glial tissue inferiorly 3 months after PRP. New vessels regressed with treatment|
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|Figure 3: Fibrovascular proliferation on the disc with vitreous hemorrhage in PDR|
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|Figure 4: Same eye in figure 3 at 3 months following PRP. Disc neovascularization regressed with residual fibrous bands|
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|Figure 6: Same eye in figure 5 at 3 months after PRP. Disc neovsacularization is regressing and pre-macular hemorrhage resolving. VA however remained poor as a result of maculopathy|
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|Figure 7: Diabetic maculopathy with hard exudate involving the fovea, yet to resolve 3 months after grid laser photocoagulation. VA remained unchanged at 6/60 after treatment|
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|Figure 9: Same eye in figure 8 showing choroidal ruptures involving the macular with a macular hole|
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|Figure 10: Pre-retinal hemorrhage occurring following PRP for PDR. Supplemetal laser treatment was given with complete regression of residual neovascularization|
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The patients had topical amethocaine eye drop with or without subtenon 2% xylocaine injection. The mode of delivery was transpupillary, through well-dilated pupils with the aid of a slitlamp and a Mainster wide field contact lens which was coupled on to the cornea. For PDR and neovascularization following central RVO, panretinal laser photocoagulation (PRP) was done, while a local scatter photocoagulation was carried out for proliferative sickle cell retinopathy (SCR) and branch RVO. Treatment variables for both were a spot size of 250 micrometer (μm), exposure duration of 0.1 seconds and power of 800-1000 milliwatt (mW). For grid laser photocoagulation for CSMO, the spot size was 100 μm, exposure time 0.1 seconds and power of 500mW. PRP was conducted in 2-3 sittings over 2-3 weeks with 1500-3000 laser burns delivered, while grid photocoagulation was completed in one sitting. For the retinal break, laser retinopexy was done with burns of spot size 250 μm and of moderate intensity, with enough number of burns to surround the break in a double row. Mild analgesics were prescribed after each session.
Follow-up period ranged from 3 months to 1 year. All demographic and clinical data were recorded on predesigned data collection sheet and then entered into the computer. Data analysis was performed with Epi-info program (2004 version 3.2.2). Ethical approval for the study was obtained from the research and ethical committee of the hospital.
| Results|| |
A total of 31 eyes of 21 patients had retinal laser photocoagulation during the study period. There were 11 females and 10 males. Mean age was 50.8 years (range: 15-70 years, standard deviation 14.7). Fifteen (71%) of the patients were diabetic. A total of 18 eyes (58%) had topical anesthesia only, while 13 eyes (42%) had subtenon's anesthesia.
The commonest indication for laser treatment [Figure 11] was PDR (52%). A total of 25 eyes in all had diabetic retinopathy (3 CSMO, 16 PDR, and 6 PDR with CSMO). The RVOs comprised of three central vein occlusions and one hemiretinal vein occlusion. All had retinal neovascularization. One of the eyes with central RVO had associated neovascular glaucoma as evidenced by iris and anterior chamber angle neovascularization with raised intraocular pressure. The eye with the hemiretinal vein occlusion also had macular edema. There was one case of proliferative SCR and a case of traumatic retinal tear.
PRP was done in 19 eyes, grid photocoagulation in 3 eyes, PRP with grid photocoagulation in 6 eyes, local scatter photocoagulation in 1 eye, local scatter photocoagulation with grid photocoagulation in 1 eye, and laser retinopexy in 1 eye. In one patient with bilateral severe PDR, adequate laser treatment could not be given and she had to be referred to a vitreoretinal specialist. Another patient with diabetic nephropathy and bilateral PDR with CSMO died before she could be evaluated at 3 months postlaser therapy. Both were, therefore, excluded from the analysis of treatment outcome.
Partial or complete regression of new vessels was achieved in 13 (72%) of the remaining 18 eyes with PDR. Five eyes had persistent new vessels despite additional laser treatment. Supplemental treatment involved retinal laser photocoagulation between previous laser scars. Resolution of macula edema was documented in three of the six eyes with CSMO that had grid laser photocoagulation.
In the eyes with RVO, neovascular regression was achieved in three eyes that completed laser treatment. There was an initial regression of iris and anterior chamber angle neovascularization in the case of neovascular glaucoma, but a recurrence was observed at 4 weeks. The patient, however, declined further laser treatment and was thus excluded from the analysis of visual outcome.
Baseline and posttreatment best corrected visual acuity (BCVA) for the diabetic patients is shown in [Table 1] and [Table 2]. [Table 3] compares the visual outcome in diabetic eyes in this study with the study by Shrestha et al.  In the 21 eyes available for review at or after 3 months, BCVA improved in 6 eyes (28.5%), remained unchanged in 13 eyes (62%), and deteriorated in 2 eyes (9.5%). Four eyes of two patients were not available for review at 3 months. The causes of poor visual outcome were premacular hemorrhage, diabetic maculopathy, macular hole, and preretinal fibrosis. Three eyes with RVO had a baseline BCVA of 6/60 or less, while one had a BCVA of 6/18. Following laser therapy, the visual acuities remained unchanged in three eyes and improved in the eye with the hemiretinal vein occlusion from 6/60 to 6/24.
|Table 1: Baseline and post-treatment visual acuity for diabetic patients|
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|Table 2: Distribution of pre-laser and post-laser best corrected visual acuity in diabetic eyes|
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|Table 3: A comparison of pre-laser and post-laser best corrected visual acuity in diabetic eyes with study by Shrestha et al.|
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The baseline BCVA of 6/12 in the eye with SCR remained unchanged after treatment, with complete neovascular regression at 3 months. The eye with the traumatic retinal tear also had choroidal ruptures involving the macula and a macular hole [Figure 8] and [Figure 9]. The break was successfully sealed with the retina remaining attached at 1 year postlaser retinopexy. The BCVA of 6/60 improved by a line to 6/36. Baseline and posttreatment BCVA in the nondiabetic eyes is shown in [Table 4].
There were no complications encountered during laser treatment. However, one patient developed a macular hole following successful PRP and one patient with PDR had a fresh preretinal hemorrhage from persistent new vessels [Figure 10].
| Discussion|| |
Laser photocoagulation is a crucial therapy for numerous retinal diseases and the diode laser has been found to be comparable in its efficacy to the argon laser in the treatment of CSMO  and PDR. , The indications for retinal diode laser photocoagulation in this series are similar to reports of other authors, , with diabetic retinopathy (PDR and CSMO) being the leading indication. Diabetes is the commonest cause of retinal vascular disease,  with the prevalence of diabetic retinopathy increasing with duration of the disease.  It usually develops between 10 and 20 years after onset of diabetes, and develops faster when diabetes is untreated or uncontrolled.  In the present study, all the diabetic patients had type 2 diabetes. Shrestha et al.,  in a study on the visual outcome of laser treatment in diabetic retinopathy also reported a similar finding.
RVO is the second most common retinal vascular disease after diabetic retinopathy.  It was the second leading indication for laser photocoagulation after diabetic retinopathy in this series. Similarly, Mchugh et al.,  reported it as the second indication for laser photocoagulation after diabetic retinopathy, while Mahmoud et al.,  reported it as the fourth. In RVO, VA at the time of presentation is a strong indicator of the ultimate quality of the patient's vision.  In the Central Vein Occlusion Study, a randomized trial of the use of laser treatment for central RVO, 65% of patients' eyes maintained 20/40 vision or better if acuity at the time of presentation was 20/40 or better; but only 1% achieved this level if acuity was initially 20/200 or worse. , In this series, VA improved in one eye from less than 6/60 to 6/24, while the VA remained unchanged in the eye with the pretreatment VA of 6/18.
In the present study BCVA improved in 28.5%, remained unchanged in 62%, and deteriorated in 9.5% of eyes with diabetic retinopathy. This contrasts with the study by Shrestha et al.,  in which BCVA improved in 52.5%, remained static in 35% and deteriorated in 12.5% of eyes following laser treatment. This difference in outcome may be due to the fact that up to 64% of eyes in their study had a baseline BCVA of at least 6/18, whereas only 24% of eyes in this study had a BCVA of 6/18 or better. Visual acuity at baseline has been shown to play a significant role in determining post-PRP VA at 1 year. , Majority of the eyes with diabetic retinopathy with poor VA at baseline still had poor VA as at the last follow-up in our study. The causes of poor visual outcome were premacular hemorrhage, diabetic maculopathy, macular hole, and preretinal fibrosis. Other studies , identified vitreous hemorrhage, progression of lens opacities, chronic macular edema, preretinal hemorrhage, preretinal fibrosis at the macula, and neovascular glaucoma as the main causes of visual loss following PRP in eyes with PDR.
Partial or complete regression of neovascularization was achieved in 72% of eyes with PDR and complete regression in 50% of eyes with RVO. In the study by Mchugh et al.,  regression of neovascularization was obtained in 81% of eyes with PDR and also in 81% of all cases of RVO. All the diabetic eyes in which we failed to achieve neovascular regression had significant elements of fibrous tissue proliferation. Mahmoud  reported three cases of PDR with persistent neovascularization following adequate initial and supplemental PRP, and recommended liberal supplemental laser treatment for nonregressing neovascularization. In this series, resolution of macula edema occurred in 50% of eyes with CSMO that had grid laser photocoagulation. Similarly, Shrestha et al.,  reported an improvement in maculopathy in 52% of eyes that had laser treatment for diabetic maculopathy.
A limitation of this study is the lack of fundus fluorescein angiography (FFA). This could not be done as sodium fluorescein injection is not readily available in our environment. FFA would have been helpful in diagnosis, determining if laser treatment is indicated or not, and also for subsequent monitoring of postlaser therapy.
| Conclusion|| |
PDR and CSMO were the most common indications for diode laser photocoagulation in our center. Significant fibrous tissue component in eyes with fibrovascular proliferation was associated with poor response to laser treatment. Our results have, however, further demonstrated the beneficial effects of diode laser photocoagulation in the management of retinal vascular diseases.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10], [Figure 11]
[Table 1], [Table 2], [Table 3], [Table 4]