Exudative retinal detachment is a disease in which fluid accumulates in the subretinal space due to extensive damage to the retina and/or choriocapillary endothelial cells and retinal pigment epithelium (RPE) cells. Exudative retinal detachment is a common manifestation of the late stage of certain ocular diseases, such as Coats disease, central serous chorioretinopathy, exudative age-related macular degeneration, familial exudative vitreoretinopathy, Vogt-Koyanagi-Harada disease, uveitis, scleritis, and ocular tumors [1-3]. In addition, it may occur rarely after vitrectomy, endolaser photocoagulation, scleral buckling, cryotherapy, glaucoma filtration surgery, and cataract surgery [4].

Exudative retinal detachment is a relatively rare postoperative complication after vitrectomy, and the specific mechanism has not been established. Previous studies have reported that endolaser photocoagulation can cause exudative retinal detachment, but no imaging evidence, including optical coherence tomography (OCT), has been published [4-6]. Both cases in this report demonstrate a characteristic subretinal fluid (SRF) distribution with foveal sparing, which was not seen in previous reports. Herein, we describe two cases of exudative retinal detachment with characteristic distribution of SRF on OCT after vitrectomy for proliferative diabetic retinopathy (PDR). This study was approved by the Institutional Review Board of Seoul National University Bundang Hospital (B-2306-834-701) and adhered to the tenets of the Declaration of Helsinki.

Case I

A 54-year-old woman presented with acute loss of visual acuity in her right eye. Fundus photography and B-scan revealed grade 3 vitreous hemorrhage (VH) without signs of retinal detachment (Fig. 1A). She was treated with pars plana vitrectomy combined with endolaser photocoagulation (power 200 mW, pulse duration 0.2 second, spot size 200 μm, 1,805 shots) and cataract surgery for 70 minutes. No tractional membrane or iatrogenic retinal tears were found pre- or intraoperatively.

Fig. 1. (A-D) Images of case 1. (A) Fundus photograph and B-scan at the initial visit. Fundus photography and B-scan reveal grade 3 vitreous hemorrhage without retinal detachment. (B) Fundus photograph and optical coherence tomography (OCT) at postoperative (postop) 4 days. Fundus photography reveals intense laser spots with narrow spacing and a suspected choroidal detachment inferotemporally. The vertical section of OCT shows subretinal fluid (SRF) in the superior and inferior regions of the fovea, sparing the foveal center, and macular edema (ME). On the horizontal section of OCT, SRF is not observed. (C) Fundus photograph and OCT 13 days postop. Fundus photography reveals that the laser burns have changed into scars with a resolution of choroidal detachment. OCT shows complete resolution of SRF with persistent ME at the fovea. (D) Fundus photograph and OCT 40 days postop. Fundus photography reveals laser scars. OCT shows improved ME. (E-G) Images of case 2. (E) Fundus photograph and B-scan at initial visit. Fundus photography and B-scan reveal grade 3 vitreous hemorrhage without retinal detachment. (F) Fundus photograph and OCT 5 days postop. Fundus photography reveals excessive laser burns with minimal spacing. The vertical section of OCT shows SRF in the inferior and superior regions of the fovea, but not the foveal center. SRF is not observed on the horizontal section image of OCT. (G) Fundus photograph and OCT 12 days postop. Fundus photography reveals laser scars. OCT shows resolution of the SRF.

On postoperative day 4, intraocular pressure (IOP) was normal (12 mmHg), and no significant inflammation was observed in the anterior chamber or anterior vitreous.

Fundus photography revealed intense laser spots with narrow spacing, and choroidal detachment was suspected inferotemporally. The vertical section of spectral domain OCT (Spectralis OCT; Heidelberg Engineering) showed SRF in the superior and inferior regions of the fovea, while sparing the foveal center (Fig. 1B). The patient was followed with observation based on a diagnosis of exudative retinal detachment. There was no change in eye drop regimen or frequency of administration, and no additional treatment such as oral steroids. 9 days later, the laser burns changed into to scars with a resolution of choroidal detachment. OCT showed complete resolution of the SRF with persistent macular edema at the fovea (Fig. 1C). She received repeated injections of intravitreal bevacizumab (Avastin^®, 1.25 mg/0.05 mL; Genentech Inc.), and macular edema improved (Fig. 1D).

Case II

A 66-year-old man reported a sudden decrease in visual acuity in the right eye. Fundus photography and B-scan revealed grade 3 VH without retinal detachment (Fig. 1E). He underwent pars plana vitrectomy and endolaser photocoagulation (power 200 mW, pulse duration 0.2 second, spot size 200 μm, 2,021 shots) for 45 minutes. No tractional membrane or iatrogenic retinal tears were identified during pre- and intraoperative assessments.

IOP was within normal range at 9 mmHg, and no significant intraocular inflammation was observed on postoperative day 5. Fundus photography revealed excessive laser burns with minimal spacing between them. On the vertical section of OCT, the SRF was mainly distributed in the inferior and superior regions of the fovea, suggesting exudative retinal detachment (Fig. 1F). On follow-up OCT 7 days later, without changes in eye drop regimen, frequency of administration, or additional treatment, SRF resolved spontaneously (Fig. 1G).

Adhesion between the retina and RPE relied on the complex anatomical structure of the neurosensory retina, RPE, and photoreceptor outer segment as well as pressure acting on the subretinal space via the retina and RPE. In addition, hydrostatic pressure, osmotic pressure, and active transport through the RPE are involved [7,8]. Three conditions, a source of fluid pressure, a defect in the blood-retinal barrier (BRB), and an area of impaired fluid transport beyond the site of leakage, are necessary for exudative retinal detachment [9].

In our cases, no problems were encountered during surgery, and postoperative fundus examination showed no hidden retinal tears, which made it possible to exclude rhegmatogenous retinal detachment. Tractional retinal detachment can also be distinguished by no tractional membrane preoperatively and intraoperatively. Based on this, we considered it exudative retinal detachment and performed shortterm observation to assess improvement. Subsequently, as SRF resolved without treatment, the diagnosis of exudative retinal detachment was confirmed. Exudative retinal detachment after vitrectomy can occur due to excessive endolaser photocoagulation or cryotherapy, intra- or postoperative hypotony, severe postoperative intraocular inflammation, and long operation time [1,4,10]. The operation time was appropriate, and intraoperative infusion pressure was well maintained at 30 mmHg. Although sutureless pars plana vitrectomy was performed, postoperative IOP was normal without leakage at the sclerotomy site. However, as illustrated in the figures, fundus photographs taken on the 4th and 5th days postoperative show narrow and excessively white laser burns. This appearance is attributed to the surgeon’s limited experience at that time, where the laser probe was positioned too close to the retina during the procedure. Therefore, the authors considered excessive endolaser photocoagulation as the cause of exudative retinal detachment, and reviewed these cases.

The cause of exudative retinal detachment after endolaser photocoagulation remains unclear. However, defects in the BRB and inflammatory response due to damage to the retinal pigment cells are considered to be the main cause [6]. Excessive laser photocoagulation exceeds the energy absorption capacity of the RPE, thereby disrupting the BRB, producing liquid exudation, and causing choroidal inflammation. Endolaser photocoagulation promotes an intraocular inflammatory response that stimulates the production of immune cells such as leukocytes, lymphocytes, and macrophages, as well as interleukin (IL)-1β, IL-6, tumor necrosis factor-α, and histamine. As vascular permeability increases, fluid leaks into the subretinal space, resulting in serous retinal detachment [4,11,12].

Shin et al. [4] and Lee et al. [5] reported cases of macular serous retinal detachment after vitrectomy and endolaser photocoagulation in patients with PDR. Shin et al. [4] suggested that excessive endolaser photocoagulation may be the cause of serous retinal detachment. Lee et al. [5] assumed that due to uncontrolled diabetes, inflammatory mediators in the vitreous cavity increased before surgery, making the patient highly susceptible to serous retinal detachment. In that report, endolaser photocoagulation triggered serous retinal detachment, with increased osmolarity due to chronic kidney disease and the use of phenylephrine to lower blood pressure during surgery, directly stimulating vasoconstriction. In both our cases, diabetes was relatively well controlled, and phenylephrine was not injected to control blood pressure before or during surgery. The case 1 had mild chronic kidney disease and the case 2 did not.

As a distinguishing feature from previous studies, we present a characteristic distribution of SRF on OCT. Both cases presented with SRF in the superior and inferior regions of the fovea, sparing the center and horizontal parts of the fovea. The characteristic distribution of SRF in these cases suggests that it may not have originated from the foveal center, but rather from the extrafoveal region, particularly the superior and inferior regions close to the laser burns. In addition, the SRF was more distributed in the inferior region of the fovea than in the superior region, which is speculated to be the result of the higher laser energy delivered to the inferior peripheral retina, as identified on short-term postoperative fundus photography. These findings suggest that intense endolaser photocoagulation could be associated with the occurrence of SRF, supporting the hypothesis that excessive endolaser photocoagulation during vitrectomy can cause exudative retinal detachment.

This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. RS-2023-00210974).

The authors declare no conflicts of interest relevant to this article.

Conception (S.H.S., M.S.K.); Design (M.S.K.); Data acquisition (S.H.S.); Interpretation (S.H.S., M.S.K.); Writing (S.H.S., M.S.K.); Review (M.S.K.); Final approval of the article (All authors)