in 1908 , george coats   described an ocular entity characterized by unilateral retinal vascular abnormalities and retinal exudation usually in boys . coats disease is associated with excessive production of yellowish intraretinal and subretinal exudates   and can cause retinal detachment and severe visual loss . proposed the most recent classification with the following stages : stage 1 , telangiectasia only ; stage 2 , telangiectasia and exudation ( 2a , extrafoveal exudation ; 2b , foveal exudation ) ; stage 3 , exudative retinal detachment ( 3a , subtotal ; 3b , total ) ; stage 4 , total detachment and secondary glaucoma ; and stage 5 , advanced end - stage disease . multiple modalities have been employed to treat coats disease , including diathermy , laser photocoagulation , cryotherapy , subretinal fluid drainage , scleral buckling surgery , pars plana vitrectomy , and intravitreal anti - vascular endothelial growth factor ( vegf ) therapy [ 68 ] . first reported selective photocoagulation and young coats patients responded quickly to laser treatment . in advanced cases with serous retinal detachment , laser photocoagulation may not be able to reach the vessels , leading to persistence of subretinal fluid and necessitating multiple courses of treatment . eyes with advanced coats disease and total retinal detachment may require pars plana vitrectomy with internal or external drainage of subretinal fluid , laser photocoagulation , and silicone oil tamponade . the purpose of this retrospective study was to assess the effectiveness of endolaser photocoagulation by a two - port pars plana nonvitrectomy approach for treating coats disease with moderate - to - severe serous retinal detachment . medical records of 24 patients ( 25 eyes ) with stage 3 coats disease diagnosed from december 2012 to may 2014 at a single center were reviewed . all of them presented with serous or total retinal detachment that could not be reached by regular laser photocoagulation and thus undertook minimally invasive operations of endolaser photocoagulation . some cases were treated combined with drainage of the subretinal fluid , intravitreal triamcinolone injection or anti - vegf injection . clinical information , including birth history , age , gender , family history , medical history , and systemic and other ocular anomalies , was assessed . all patients routinely underwent indirect ophthalmoscopy . wide - angle retina photography ( retcam ; clarity medical systems , pleasanton , ca , usa ) was performed in patients younger than 5  years and fundus photography ( optos 200tx ; optos , dunfermline , scotland , uk ) was performed in older cooperative patients . two 23- or 25-gauge incisions were made 3  mm posterior to the corneal limbus and the retina was examined . the surgical procedure commenced with the examine of the retinal vessels , followed by laser directly on the entire network of telangiectatic vessels and the injection of viscoelastics afterwards to minimize vitreous traction at the side ports ( figs .  1 and 2 ) . telangiectasias were ablated with a 532-nm green endolaser ; the power was adjusted according to the retinal reaction to laser spots . 1illustration of the surgical procedure of a 4-year - old boy with stage 3a coats disease ( os ) . 2drainage of subretinal fluid of a 2-year - old boy with stage 3b coats disease ( os ) illustration of the surgical procedure of a 4-year - old boy with stage 3a coats disease ( os ) . bottom right anti - vascular endothelial growth factor ( vegf ) injection drainage of subretinal fluid of a 2-year - old boy with stage 3b coats disease ( os ) additional treatments such as intravitreal triamcinolone or anti - vegf injection and further surgery were performed based on findings of fundus fluorescein angiography , conditions during endolaser photocoagulation , and postoperative outcomes . therapeutic effects were determined according to the patients visual acuity , intraocular pressure , fundus and abnormal vascular changes . all the patients were born at full term or late preterm , with a birth weight above 2,500  g. none had a related family history . the study population comprised 23 boys ( 95.83  % ) and one girl ( 4.17  % ) ; patient age ranged from 2 to 17  years ( mean , 6.21  years ) . patients were divided into three groups according to the severity of the disease and previous treatment regimens and the data are presented in table  1.table 1patient informationgrouppatienteyegenderage at presentation ( years)follow - up duration ( months)a1osm3182odm2163odm8144odm17145oum3156osm1177osm568odm549odm31b1osm13182osm9173odm5164osm9165odm2146osm3127odm648osm549odm9310odm6311odm92c1osm4202oum3153osm2114odm445osf63 group a ( nine eyes ) received laser photocoagulation and/or cryopexy before , however , the treatment above could not stop the vascular abnormalities , thus these patients received the endolaser . group b ( 11 eyes ) was initiated with endolaser treatment regimen due to the presence of serous retinal detachment . patients in group c ( five eyes ) were in stage 3b , received external drainage of subretinal fluid plus non - vitrectomized vitrectomy . additionally , triamcinolone and anti - vegf were injected according to the condition of abnormal vessels . visual acuity , intraocular pressure , eye position , slit - lamp microscope , indirect ophthalmoscope , and color fundus imaging were followed up ( average , 10.08  months , range , 120  months ) . at the end of the follow - up period , 24 ( 96  % ) eyes had the retina reattached , telangiectasias were resolved , and no severe complications occurred . in groups regular laser therapy under indirect ophthalmoscopy was barely effective on the abnormal vessels with exudative retinal detachment and serous retinal detachment and endolaser could shorten the period of recovery . the average sessions to full treatment of active telangiectasia and retinal reattachment was 4  months ( range , 110  months ) ; only one ( 4.17  % ) eye progressed to retinal detachment due to lack of follow - up . each eye received 15 sessions of treatments ( average , 1.96 times ) ( table  2 ) . increased intraocular pressure in one ( 4.17  % ) eye after surgery was controlled with eye drops.table 2patient treatmentsgrouppatientrange of exudation ( quadrant)treatments ( sessions)a122242332434544621743821923b14122133144154164274184192210411141c142245343442542 seven and 17 eyes required subsequent intravitreal triamcinolone and anti - vegf injections , respectively . these injections were not associated with endophthalmitis or systemically observed complications . among the 17 patients who would cooperate with visual examination , five ( 29.41  % ) had improved visual acuity at the end of the treatment session . because of recurrence of miliary aneurysms , two ( 22.22  % ) eyes in group a and two ( 18.18  % ) eyes in group b had consecutive regular laser ablation at 1 to 6  months ( average , 2.25  months ) afterward the endolaser treatment . most exudation was absorbed with a flat retina until the last follow - up ( fig . the five patients in group c who presented with total retinal detachment , undertook drainage of the subretinal fluid combined with anti - vegf injection , received two - port endolaser ablation and regular laser or other treatments afterwards ( fig . 4 ) . among them , one eye developed fibrosis in the peripheral retina 4  months after endolaser treatment , so three - port pars plana vitrectomy was performed and the retina finally reattached after three sessions without obvious telangiectasia and the exudation absorption . 3fundus views of a 2-year - old boy with stage 3a coats disease ( od ) . 4fundus views of a 3-year - old boy with stage 3b coats disease ( od ) . bottom right view at 2  months after supplementary laser fundus views of a 2-year - old boy with stage 3a coats disease ( od ) . right postoperative view at 13  months fundus views of a 3-year - old boy with stage 3b coats disease ( od ) . the overall aims of treatment in mild disease are ablation of abnormal retinal vasculature , preservation of vision , and prevention of retinal detachment . in advanced cases , , we performed the two - port endolaser with the help with noncontact wide - angle viewing system and fluorescein fundus angiography to guarantee the treatment . schefler et al .   showed that 50  % of the patients with coats disease can retain useful vision with aggressive repetitive diode laser therapy even if the disease is advanced at presentation . the difference in outcomes can be explained by the disease severity : the present study included patients with stage 3 coats disease with local or total exudative retinal detachment . according to our experience , this stage is considered less responsive to laser therapy under indirect ophthalmoscopy and the prognosis is worse than those of stages 1 and 2 . further , exudation in the macular area took longer to absorb than peripheral retinal exudation and vision of eyes with macular exudation was not satisfactory in the study . in this study kranias and krebs   reported successful management of advanced coats disease with pars plana vitrectomy and air  fluid exchange . susskind et al . used ppv , including a modified technique of exocryotherapy applied after fluid  air exchange to reduce associated side effects and improve the rehabilitation process of advanced coats disease patients . in the present study , stage 3b coats disease was treated by subretinal fluid drainage , endolaser photocoagulation , and anti - vegf injection . cryotherapy and silicone oil tamponade was not performed to avoid the damage to the eyeball and the need for secondary surgeries . in two cases , endolaser photocoagulation the other patients underwent the procedure 1  week after drainage . to our knowledge , this is the first time the two - port pars plana nonvitrectomy approach for treating coats disease has been reported in the literature . first , it resolves the problem associated with laser ablation in eyes with serous retinal detachment where telangiectasias can not be reached by regular laser ablation . we applied a laser directly to telangiectasia within the retina without targeting the rpe to create thermal injury . second , it is non - vitrectomized and is much less invasive than three - port pars plana vitrectomy . third , when combined with peripheral retinal examination , the procedure could be more thorough and efficient , so the number of treatment sessions could be reduced . to minimize vitreous traction at the side ports , injection of viscoelastics was performed afterwards and turned out to be an effective measure . reported that carefully selected treatment can anatomically stabilize eyes or improve coats disease in 76  % of the cases . the present treatment yielded better results : 96  % of the eyes showed retinal reattachment and no active telangiectasias . bevacizumab and ranibizumab should be used cautiously in patients with coats disease to avoid vitreoretinal fibrosis and tractional retinal detachment . a taiwanese study   showed that cryotherapy combined with intravitreal bevacizumab injection in severe cases of exudative retinal detachment carries the risk of vitreoretinal fibrosis and tractional retinal detachment . in the present study , only one eye developed vitreoretinal fibrosis 4  months after anti - vegf injection , which was in group c and the fibrosis might be connected with the serious disease or the treatments received . extended serial follow - up is important to evaluate the safety of this treatment and usage of anti - vegf injection . endolaser photocoagulation by two - port pars plana nonvitrectomy is a safe and effective approach in treating advanced coats disease with serous retinal detachment this research was supported by the national natural science foundation project of china ( 81070760 , 81271045 ) . all authors certify that they have no financial interests ( such as personal or professional relationships , affiliations , knowledge or beliefs ) in the subject matter or materials discussed in this manuscript .
backgroundto evaluate the effectiveness of endolaser photocoagulation by a two - port pars plana nonvitrectomy approach for treating coats disease with shallow exudative retinal detachment.methodsthis study included 24 patients ( 23 boys with an age range of 217  years , and one girl , age 6  years ) with stage 3 coats disease ( 25 eyes ) from december 2012 and may 2014 at a single center . 
 all of the 25 eyes were complicated with serous or total retinal detachment and received none - vitrectomized endolaser : two ( 23- or 25-gauge ) incisions were routinely made 3  mm posterior to the corneal limbus and a laser was applied directly on the abnormal blood vessels . 
 additional treatments included subretinal fluid drainage ( five eyes ) , intravitreal triamcinolone injection ( seven eyes ) , and intravitreal anti - vascular endothelial growth factor ( vegf ) injection ( 17 eyes ) . 
 best - corrected visual acuity , intraocular pressure , and fundus and abnormal vascular changes were recorded to determine therapeutic effects.resultstwenty-four out of the 25 treated eyes ( 96  % ) had retina reattached . 
 the number of treatment sessions differed case by case ( 15 sessions , average 1.96 ) and the time to full treatment of retinal reattachment was 4  months in average . 
 one patient ( 4  % ) presented with retinal redetachment . 
 five ( 20  % ) eyes received further laser treatment with indirect ophthalmoscope and four eyes ( 16  % ) presented with total retinal detachment at their first visits received consecutive treatments . at the end of the follow - up period ( mean , 10.08  months ) , telangiectasias of 24 ( 96  % ) eyes were resolved and no severe complications occurred.conclusionsendolaser photocoagulation by a two - port pars plana nonvitrectomy approach is an effective treatment for advanced coats disease with serous retinal detachment . 
 the long - term safety of the approach needs further investigation .