INITIAL EXPERIENCE WITH TRANSPUPILLARY DIODE LASER PHOTOCOAGULATION FOR RETINAL DISEASES

Abstract

Background

Lasers are an invaluable treatment modality for the management of some retinovascular diseases. One of these lasers is the diode laser which is easy to procure and maintain.

Aim

To review the outcomes of diode laser photocoagulation in patients with a variety of retinal conditions.

Patients & Methods

A retrospective case series of all patients who had retinal laser photocoagulation between July 2012 and June 2014 with the semiconductor infrared diode laser was performed. Demographic and clinical data collected included age, sex, eye involved, visual acuity, diagnosis, associated systemic and ocular diseases, intra and post treatment findings, laser treatment parameters and follow up.

Results

A total of 22 eyes of 15 patients had diode laser treatment during the period under review comprising 8(53.3%) males and 7(46.7%) females with a mean age at presentation of 53.4±8.9 years. The indications for treatment were proliferative diabetic retinopathy in 18(81.8%) eyes of 11 patients, retinal vein occlusion in 2(9.1%) eyes of 2 patients and retinal breaks with lattice in 2(9.1%) eyes of 2 patients with fellow eye retinal detachment. Visual acuity in eyes with diabetic retinopathy improved in 9(50%) eyes, worsened in 3(16.7%) eyes and was unchanged/ stable in 6(33.3%) eyes. Regression of neovascularization was achieved in 2(100%) eyes with retinal vein occlusion. The retina of the 2(100%) eyes with breaks following retinopexy remained attached during the follow up period. The follow up period ranged from 2 days to 2 years with a mean duration of 13.5±15.8 months.

Conclusion

The diode laser is an effective and beneficial treatment modality in the management of proliferative retinopathies and some retinal diseases.

Introduction

In medical practice, the options utilized in the management of diseases include medical, surgical and laser interventions. Laser, an acronym for Light Amplification by Stimulated Emission of Radiation is an invaluable treatment modality in ophthalmology in general and specifically in the treatment of vitreoretinal diseases. It can be delivered via a variety of ways viz: transpupillary either via slit lamp or indirect laser ophthalmoscope, transcleral or endodelivery1,2,3,4. Lasers commonly used in posterior segment eye diseases include the 532nm argon green and 810nm infrared diode5^-5. These both have their merits and demerits making them suitable in different scenarios. The diode laser is compact, cheaper to procure and maintain, has better penetration in hazy media and complaints of seeing bright flashes of light by patients during treatment is much less4,7^-10. However, higher energy levels and longer exposure are required to achieve similar photocoagulation effects with the argon green due to poor absorption. This results in more pain, oedema and greater risk of choroidal haemorrhage4,7^-9. This study is a review of the outcomes of diode laser photocoagulation treatment in patients that had a variety of retinal conditions.

Patients and Methods

A study of patients that had retinal laser photocoagulation between July 2012 and June 2014 with the semiconductor infrared diode laser was performed. The case folders of patients who received treatment with the semiconductor diode laser for a variety of retinal conditions were retrieved from the register for lasers and a retrospective review conducted. Demographic and clinical data collected include age and gender, eye involved, visual acuity, diagnosis, associated systemic and ocular diseases, intra and post treatment findings, laser treatment parameters and follow up. Patients were treated with diode laser photocoagulation system (Nidek Co Ltd. Gamagoro Aichi, Japan) with a transpupillary approach following maximal dilatation with gutt phenylephrine 2.5% or tropicamide 0.5% and topical anaesthesia with gutt tetracaine with the aid of a slitlamp using the Mainster widefield Argon/Diode laser contact lens 160 (Ocular instruments Inc.Bellevue, USA) which was coupled on the corneal with a coupling gel (methylcellulose). Post treatment, patients were prescribed gutt diclofenac sodium three times daily for one week, a nonsteroidal anti-inflammatory eye drop. Patients who had panretinal laser photocoagulation (PRP) for proliferative diabetic retinopathy or ischaemic central retinal vein occlusion were treated with a spot size of 200 micrometer(µm), exposure duration of 0.1-0.2 seconds and power of 300-700milliwatt (mW) with burns being one burn width apart to achieve a moderate intensity grey white reaction. Panretinal laser photocoagulation (PRP) was conducted in 2-3 sittings over 2-3 weeks with about 1500 laser burns delivered. Retinopexy was performed for patients with retinal breaks with moderate intensity contiguous but not overlapping laser burns with a spot size of 200 μm with enough number of burns to surround the break in a double row. Data analysis was performed with the GraphPad Instat Software, Inc. version V2.05a software program. The study was conducted in accordance with regulations concerning the ethical use of human subjects.

Results

A total of 22 eyes of 15 patients had diode laser treatment (DLT) during the period under review comprising 8(53.3%) males and 7(46.7%) females. The mean age at presentation was 53.4±8.9 years (range 31-65 years). The indications for treatment were proliferative diabetic retinopathy in 18(81.8%) eyes of 11 patients, retinal vein occlusion in 2(9.1%) eyes of 2 patients and retinal breaks with lattice in 2(9.1%) eyes of 2 patients with fellow eye retinal detachment. The follow up period ranged from 2 days to 2 years with a mean duration of 13.5±15.8 months. Pain was a universal complaint reported in all patients. Complications such as choroidal or retinal haemorrhages, inadvertent foveal burn or detachment were not recorded in any patient.

In patients with proliferative diabetic retinopathy, associated systemic conditions include hypertension in 9 (81.8%) patients, dyslipidaemia in 1(9.1%) patient and nephropathy in1 (9.1%) patient. Other ocular conditions in the eyes with diabetic retinopathy included lens opacities in 18(100.0%) eyes, hypertensive retinopathy in 8(44.4%) eyes, fibrovascular proliferations in 5(27.8%) eyes, tractional retinal detachment in 3(16.7) eyes and diabetic macular oedema in 5(27.8 %) eyes. The best corrected visual acuity in the eyes with diabetic retinopathy improved in 7(38.9%) eyes and was stable/unchanged in 11(61.1%) eyes. In eyes that had associated diabetic macular oedema, these were treated with intravitreal antivascular endothelial growth factors such as ranibizumab and bevacizumab prior to commencement of PRP. These are presented in Table 1.

Table 1 . Characteristics of patients with proliferative diabetic retinopathy .

No	Age (Year)	Sex	Eye	Pre laser BCVA	Post laser BCVA	Associated Systemic dx	Associated Ocular dx	Adjunct Rx	Outcome	Flw up (mths)
1	50	F	RE	6/18	6/18		Lens opacities, DME	IVT antiVEGF	Stable	54
2	61	M	RELE	CF@1MCF@1M	CF@1MCF@1M	Htn	BES: Lens opacities, FVP, TRD	Nil	StableStable	35
3	65	F	RELE	6/60CF@3m	6/366/24	Htn	BES: Lens opacities, DME, LE: FVP	BES:IVT antiVEGF	ImprovedImproved	17
4	46	M	RELE	6/96/18	6/66/18	Htn,Nephropathy	Lens opacitiesLE: DME	LE: IVT antiVEGF	ImprovedImproved	4
5	49	M	RELE	6/24HM	6/246/18	Htn	BES: Lens opacities LE: FVP, TRD	Nil	stableImproved	12
6	62	F	RELE	CF@1MCF@1.5M	CF@1m6/36	Htn,Dyslipidaemia	BES: Lens opacities RE: FVP, LE: DME	LE: IVT anti VEGF	StableImproved	12
7	54	F	RELE	HM6/36	HM6/24	Htn	BES: Lens opacitiesRE: FVP, TRD,	Nil	Stable Improved	3
8	31	F	LE	6/24	6/24		Lens opacities	Nil	Unchanged	5 days
9	57	F	LE	6/24	6/24	Htn	Lens opacities	Nil	Unchanged	1
10	58	M	RELE	6/606/36	6/606/36	Htn	BES: Lens opacities	Nil	Stable Stable	5
11	45	M	LE	CF@1M	CF@1M	Htn	Lens opacities	Nil	Unchanged	1 week
Key: BCVA=best corrected visual acuity, dx=disease, Rx=treatment, Flw up=follow up, mths=months, M=male, F=female, HM=hand movement, CF=counting fingers, Htn=hypertension, BES= both eyes, RE=right eye, LE=left eye, FVP=fibrovascular proliferation, TRD=tractional retinal detachment, DME=diabetic macula oedema, IVT Anti VEGF= intravitreal anti vascular endothelial growth factor

Predisposing conditions for retinal vascular occlusion were hypertension in the 2 (100%) patients and glaucoma in 1(50%) patient. Visual acuity improved from hand movement to 6/24 in 1(50%) eye following panretinal photocoagulation with adjunct intravitreal ranibizumab, an antivascular endothelial growth factor in 1(50%) eye with associated macula oedema and rubeosis iridis while it remained unchanged in the other patient with associated glaucoma. However, both patients achieved regression of neovascularization following laser photocoagulation as shown in Table 2. Table 2 also shows that the two eyes which had delimiting laser photocoagulation/retinopexy for lattice degeneration with holes in fellow eye retinal detachment have been stable with good chorioretinal adhesion around the breaks within the follow up period which was a maximum of 27 months and no progression to retinal detachment in the eyes.

Table 2 . Characteristics of patients with non diabetic indications for laser.

No	Age(Years)	Sex	Affected eye	Indication	Associated ocular dx	Associated systemic dx	BCVA pre laser	BCVA post laser	Adjunt Rx	Outcome	Follow up (mths)
1	54	F	RE	CRVO with neovascularization on disc and rubeosis iridis	Macula oedema	Htn	CF @1M	6/24	IVT anti VEGF	Improved with regression of neovascularization and macula oedema	17
2	62	M	LE	CRVO with retinal neovascularization	Glaucoma, Hypertensive retinopathy	Htn	HM	HM	Nil	Stabilized with regression of neovascularization	3
3	54	M	LE	Lattice with holes with fellow eye chronic RD	Lens opacities	Htn	6/9	6/9	Nil	Improved with good chorioretinal adhesion reaction of laser burns	27
4	60	M	RE	Pigmented lattice with fellow eye chronic RD	Nil	Nil	6/6	6/6	Nil	Improved with good chorioretinal adhesion reaction of laser burns	3
Key: BCVA= best corrected visual acuity, dx=disease, Rx= treatment, mths= months, M=male, F=female, CRVO=central retinal vein occlusion, RD=retinal detachment, HM=hand movement, CF=counting fingers, Htn=hypertension, RE=right eye, LE=left eye, IVT Anti VEGF= intravitreal anti vascular endothelial growth factor

Discussion

The availability of the diode laser for the management of some retinovascular conditions such as proliferative diabetic retinopathy has greatly enhanced service delivery to patients, obviating the need to make referrals to facilities mostly located outside the state. This is important as many patients referred for management outside the state usually hesitate, delay or fail to follow through on those appointments stating financial costs and logistics as their reasons. This obviously impacts negatively on their ocular health and prognosis. Although pain was a universal complaint reported in all patients, the procedure did not have to be discontinued nor local anaesthesia such as peribulbar, subtenon, subconjunctiva or retrobulbar anaesthesia administered to any patient.

The most common indication for the use of laser in this study was diabetic retinopathy in 81.8% eyes. Previous studies have also reported diabetic retinopathy as the most common indication for laser4,5,6,7. This is likely associated with the rising incidence of diabetes mellitus in the population with increasing modernization and adoption of western and sedentary lifestyle, dietary changes to refined and processed foods and proliferation of fast food outlets11,12. This figure would have been higher if cases with diabetic macular oedema were treated with grid or focal laser. Systemic conditions which worsen diabetic retinopathy found were co-existing hypertension (81.8%), hyperlipidaemia(9.1%) and nephropathy(9.1%). Eyes with tractional retinal detachment had laser photocoagulation applied to flat portions of the retina to reduce the risk for further detachment while awaiting vitreoretinal surgical intervention.

In eyes with proliferative diabetic retinopathy, those with associated diabetic macular oedema had adjunctive treatment with intravitreal antivascular endothelial growth factors such as ranibizumab and bevacizumab prior to commencement of PRP. This was performed to reduce the risk of increasing macula oedema, a possible complication of panretinal photocoagulation which can further worsen vision in these eyes13. The presence of diabetic macula oedema in these eyes would also have had a negative impact on the vision of these eyes. The advent in the use of antivascular endothelial growth factors for diabetic macula oedema was responsible for the non usage of focal or grid laser as a treatment modality of diabetic macular oedema14. The various treatment modalities have their merits and demerits. While use of intravitreal antivascular endothelial growth factors has the advantage of not causing any structural damage to the retinal nerve fibre layer, these are more expensive and often require multiple injections with a possible risk of endophthamitis which though minimal, could lead to visual loss14. In addition, use of intra ocular steroids could result in steroid induced glaucoma or cataract in phakic eyes. On the contrary, though lasers are relatively less expensive, there could be inadvertent foveal burns, visual field defects, retinal fibrosis and the scars from the procedure could sometimes extend with the passage of time to the fovea resulting in permanent visual loss14. Furthermore, there is also a small risk of choroidal neovascular membrane formation in laser scars which would again require treatment to prevent visual loss.

Both patients with central retinal vein occlusion had uncontrolled hypertension, a systemic risk factor for retinal vascular occlusion while one also had poorly controlled glaucoma, a known ocular risk factor for vascular occlusion15^-17. These conditions are largely modifiable for which adequate patient education would improve compliance to decrease insults to the retinal vasculature. Although, regression of neovascularization following panretinal laser photocoagulation occurred in the 2(100%) eyes, vision improved in only 1(50%) eye. This was in the eye with associated macular oedema treated with intravitreal bevacizumab. The prognosis following retinal vascular occlusion is dependent on many factors including presence and duration of macula oedema, degree of retinal ischaemia and presence of complications such as neovascular glaucoma18. The risk of neovascularization is increased in eyes with ischaemic retinal vein occlusion with areas of capillary non perfusion/drop out on fundus fluorescein angiography; further worsening of vision occurring when neovascular glaucoma develops. This usually occurs about three months after the vascular occlusion hence commonly referred to as 100 day glaucoma19.

The risk of fellow eye retinal detachment in eyes with lattice degeneration or retinal holes is further increased. Studies have shown this risk can be minimized, but not completely eliminated with the use of delimiting laser photocoagulation for adequate retinopexy20. In the absence of laser, cryotherapy can be utilized but would require other forms of anaesthesia such as retrobulbar anaesthesia for adequate pain control and is associated with increased pigment dispersion. It also produces inflammation, exudation and delayed adherence for adequate chorioretinal adhesion in contrast with laser retinopexy21,22.

In conclusion, the infrared diode laser is an effective, beneficial and suitable laser treatment option in the management of proliferative retinopathies and some retinal diseases.