FP1825 : Subthreshold micropulse yellow laser in the treatment of Central serous chorioretinopathy

Dr.Vignesh T P

Micropulse yellow laser in the treatment of central serous chorioretinopathy

 Introduction

Central serous chorioretinopathy(CSCR) is a disease,characterized by serous retinal detachment involving the macula and is associated with serous retinal pigment epithelial detachments. It is usually seen in young and middle aged individuals and affects predominantly males.¹ The exact etiology is not very clear ,however this condition is associated with type A personality² , any form of steroid use for various other diseases³ as well as in conditions like Cushing’s syndrome where there is endogenous hypercortisolism.⁴In CSCR ,serous macular detachment occurs  due to focal breakdown of outer blood retinal barrier seen as leaks in fundus fluorescein angiography(FFA).¹The  primary pathology is thought to lie in the choroids and choroidal hyperpermeability was demonstrated by Indocyanine green angiography(ICGA) ,under the areas of outer blood retinal breakdown⁵ and may occur because of choroidal venous stasis,choroidal  ischemia and choroidal inflammation.⁶

CSCR is usually self-limiting and it resolves spontaneously in majority of individuals within 3 months. The treatment is indicated only when the condition does not resolve beyond 3 months or when the individual needs early visual rehabilitation within 3 months. Laser photocoagulation is generally used to treat CSCR and laser is directedto the area of leakage, results in resolution of serous macular detachment as well as improvement in visual acuity. However collateral damage can occur in conventional laser photocoagulation,even though the laser is directed at the retinal pigment epithelium(RPE) due to temperature rise which spreads ,resulting in damage to overlying neurosensory retina as well as adjacent healthy RPE, resulting in complication of scotoma ,especially in acute cases with sub/juxta foveal leak and chronic cases with large ,diffuse leaks. Choroidal neovascularistion can also occur in 5-7% of cases treated with conventional laser photocoagulation.

Subthreshold micropulse diode infrared laser is a safer alternative,wherein the endpoint after laser application is invisible and there is no temperature rise, thereby preventing collateral damage. Several studies have demonstrated the safety and efficacy of subthreshold micropulse diode laser in the treatment of acute as well as chronic CSCR. Solid state yellow laser(577nm) was recently introduced which can be delivered by continuous wave as well as micropulse mode. It has properties similar to infrared laser. We wanted to study the efficacy of subthreshold micropulse yellow laser in the treatment of CSCR.

Material and methods

Patients diagnosed to have CSCR with a duration of more than 3 months or recurrent cases of CSCR were included in the study, after obtaining informed consent. All the study subjects, underwent best corrected visual acuity measurement by Snellen’s visual acuity chart, a thorough anterior segment examination by slit lamp and a complete posterior segment examination by 90 D slit lamp biomicoscopy and indirect ophthalmoscopy. They also underwent fundus fluorescein angiography and spectral domain optical coherence tomography by Topcon 3D system. Subjects underwent the subthreshold micropulse yellow laser with Iridex IQ 577 nm system . A spot size of 100 µ, duration of 200 ms and a duty cycle of 5 % was set for all the subjects. First test burns in the micropulse setting, were given in the inferonasal quadrant to produce a visible burn and then the power required to produce a subthreshold burn was calculated by reducing the power by 50 % from the power required to produce visible burn. The area of leak or ooze was then treated with contiguous subthreshold invisible burns.

The follow-up visits were scheduled at 1,3 and 6 months.OCT was repeated at all the follow-up visits. If significant fluid was still,persisting at 3^rdmonth visit,then FFA was repeated and if leak was found to be persisting, then the treatment was repeated.

Results

Twelve eyes of 12 patients were included in the study and all study subjects were males. The mean age of the study subjects was 40.17 years. The mean duration of CSCR was 3.5 months, ranging from 1to 12 months.Out of 12 patients, 5 patients had 1 previous episode and 1 patient had 3 previous episodes. Four patients gave history of previous treatment out of 12 patients and 3 out of the 4 patients gave history of one previous focal laser treatment and one patient gave history of 3 previous focal laser treatment.

Visual acuity was converted into logMar for analysis. Wilcoxon sign rank test was used to find out the significant difference in visual acuity between each visit compared to baseline. P-value less than 0.05 considered as statistically significant. The p-value shows that there is a significant difference in VA between baseline visual acuity and 1^st month (p-value = 0.016), 3^rd month (p-value = 0.016) & 6^th month (p-value = 0.011).

Foveal subretinal fluid level was measured at baseline and at each follow-up visit.Wilcoxon sign rank test was used to find out the significant difference in SRF between each visits compared to baseline. The p-value shows that there is a significant difference in SRF between baseline and 1^st month (p-value = 0.002), 3^rd month (p-value = 0.002) & 6^th month (p-value = 0.002).

Ten out of 12 eyes(83.3%) had a complete resolution of SRF at the end of 12 months and only 1 patient required repeat laser at the 3^rd month visit with decrease in SRF at the 6^th month follow-up.

Discussion

Our study has shown a beneficial effect of subthreshold micropulse yellow laser in the treatment of CSCR with a statistically significant improvement in visual acuity as well as subfoveal fluid level from baseline to every follow-up visit and there were no side effects. Few studies have shown the efficacy and safety of subthreshold micropulse yellow laser in the treatment of chronic CSCR.^7-11Two studies have compared photodynamic therapy (PDT) with subthreshold micropulse laser in the treatment of CSCR , one study compared withlow-fluence PDT¹² and another study compared with half-dose verteporfin,¹³ both studies revealed that subthreshold micropulse yellow laser comparable to PDT in efficacy , in the resolution of CSCR. The cost of subthreshold micropulse yellow laser is a fraction of the cost of PDT making it a very affordable option for most of the patients. However, prospective, randomized, and comparative large-scale studies are needed to evaluate the efficacy and safety of this treatment.

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