To investigate intraretinal changes after successful cataract surgery in patients with previous pars plana vitrectomy (PPV) and indocyanine green–assisted peeling of epiretinal membrane and internal limiting membrane (ILM).
Prospective nonrandomized controlled clinical study.
Twenty eyes of 20 patients with cataract with previous 23-gauge PPV and ILM peeling (PPV group) and 15 consecutive eyes with senile cataract with a healthy macula (control group) were included. Best-corrected visual acuity (BCVA), spectral-domain optical coherence tomography (OCT), infrared fundus imaging, and biomicroscopy were performed at baseline and at week 1, month 1, and month 3 after cataract surgery. OCT raster scans were further analyzed regarding the central millimeter thickness (CMMT), area of retinal thickening size on the topographic map, and changes in retinal structural morphology.
The baseline mean visual acuity in the PPV group was 0.3 ± 0.18 Snellen lines, which improved significantly to 0.85 ± 0.18 ( P < .05) 3 months after cataract surgery. CMMT was 393 (± 44) μm at baseline and increased to 408 (± 47) μm at month 3 ( P < .05). One patient was not seen at the final visit, so data of 19 patients was used. In the PPV group, 8 of 19 patients (42%) developed an increase in CMMT more than 35 μm 1 month after cataract surgery; 5 of these 8 patients (26%) developed macular edema with cyst formation. Three months after surgery, the area of retinal thickening was significantly larger in most patients compared with baseline values. No cystoid macular edema was observed in the control group.
This study provides evidence that patients with previous PPV and membrane and ILM peeling often develop macular edema after successful cataract surgery.
Although improvements in surgical technique have made cataract surgery an increasingly safe procedure, pseudophakic cystoid macular edema (PCME)/Irvine-Gass syndrome remains one of the most common unexpected causes of poor postoperative visual acuity. The reported incidence varies from 3% to up to 60%, depending on the diagnostic method (optical coherence tomography [OCT], angiography, or clinical examination) and surgical method used. The incidence of angiographic cystoid macular edema (CME) after intracapsular cataract extraction is significantly higher compared with extracapsular cataract extraction.
Irvine-Gass syndrome was first described in 1953 by Irvine and usually manifests 1 to 3 months postoperatively, causing visual impairment and corresponding metamorphopsia and retinal thickening attributable to serous exudation from incompetent intraretinal capillaries into the outer plexiform layer of Henle. Most patients recover spontaneously (up to 80%) with full restoration of visual function by 3 months to 12 months postoperatively. In a small minority of patients CME persists, accompanied by visual impairment despite systemic and topical treatment (nonsteroidal anti-inflammatory drugs [NSAIDs] and corticosteroids).
The pathogenesis of this syndrome is still not completely understood. However, it is known that complicated surgery (eg, posterior capsule rupture, vitreous loss, vitreous prolapse through wound, iris trauma), diabetic retinopathy, uveitis, or preexisting epiretinal membrane are predisposing factors. Various theories have been proposed for the origin of PCME, including inflammation with the release of mediators, such as prostaglandins and leukotrienes, vascular instability, vitreomacular traction, ocular hypotony, and ultraviolet light damage. To date, there is only sparse literature on the development of the PCME in vitrectomized eyes.
Recently, a new generation of OCT devices relying on spectral-domain technology (SD OCT) has been introduced and allows for higher-resolution imaging. Based on this technology we can identify variable changes at the retinal surface, such as retinal thickening with cyst formation, swelling in the inner and outer nuclear layers, and subretinal fluid. The introduction of an eye-tracking mode has allowed better insight into the development of retinal morphologic changes.
The aim of this study was to investigate the incidence and structural morphology of PCME after successful uncomplicated cataract surgery in patients with previous pars plana vitrectomy (PPV) and indocyanine green–assisted peeling of an epiretinal membrane and the internal limiting membrane (ILM).
Patients and Methods
This is a prospective nonrandomized controlled clinical study. Following a standardized ophthalmologic examination, including Snellen visual acuity, dilated pupil ophthalmoscopy, and OCT imaging, 20 eyes of 20 consecutive patients meeting the inclusion criteria were entered in this observational prospective controlled clinical study.
For inclusion, patients had to have a visually compromising cataract with previous PPV and indocyanine green–assisted peeling of a macular pucker and the ILM. Exclusion criteria were a history of branch retinal vein occlusion, central retinal vein occlusion, wet macular degeneration, diabetic retinopathy, uveitis, or other inflammatory eye disease. Fifteen eyes without any retinal disease or previous ocular surgery and with senile cataract were included as controls.
All examinations were conducted at the Department of Ophthalmology, Medical University of Vienna, Austria. Best-corrected visual acuity (BCVA) and Spectralis SD OCT (Eye Explorer software version 4.0; Heidelberg Engineering Inc, Dossenheim, Germany) examinations and biomicroscopy were performed at baseline, week 1, month 1, and month 3. The central millimeter thickness (CMMT), central point thickness (CPT), and the retinal volume (RV) in the central millimeter of the ETDRS grid were assessed in OCT. The area of retinal thickening was defined as the area with more than 350 μm retinal thickening size on the topographic map. All planimetric measurements were performed using ImageJ (National Institutes of Health, Bethesda, Maryland, USA).
Surgeries were performed between September 1, 2009 and February 28, 2011 by 2 experienced surgeons (M.G., S.S.) using a standardized, small-incision phacoemulsification technique. All surgeries were performed using the Oertli OS3 Base Module VC830100 phacoemulsification machine (Oertli Instrumente AG, Berneck, Switzerland). A 2.4-mm temporal, single-plane, self-sealing limbocorneal incision was created. The anterior chamber was filled with a viscoelastic substance and a continuous curvilinear capsulorrhexis was created to attain a symmetrical 360-degree rhexis-IOL overlap. After the phacoemulsification and the in-the-bag IOL implantation, viscoelastic substance was removed from the capsular bag and anterior chamber by irrigation and aspiration. Surgical complications such as posterior capsule rupture, vitreous loss, and prolapse through the wound or iris trauma were exclusion criteria. Postoperative treatment consisted of topical combination dexamethasone/gentamicin eye drops 4 times a day and dexamethasone/gentamicin ointment (Dexagenta drops/ointment; Croma Pharma, Leobendorf, Austria) at night for 4 weeks. One week after surgery, patients with an increase of CMMT also received topical ketorolac-trometamol (Acular; Pharm – Allergan, Ettlingen, Germany). Acular is an NSAID preventing the synthesis of prostaglandins through inhibiting the cyclooxygenase. At month 1, patients with macular edema received topical ketorolac-trimetamol and prednisolone trimethylacetate (Ultracortenol; Ciba Vision, Vienna, Austria) eye drops 3 times daily until the month 3 follow-up time. At month 1, patients with macular edema and significant vision decrease also received oral prednisolone 100 mg/day for 5 days. In case of persistent edema at month 3 follow-up time, an injection of intravitreal triamcinolone (4 mg) was applied.
Spectral-Domain OCT Imaging
The Spectralis SD OCT device combines high-resolution cross-sectional OCT imaging of the retina with the ability to perform angiography and infrared examinations using the same device. The scanning speed is ∼40 000 A-scans per second. The scans are registered on the fundus using the simultaneously acquired scanning laser ophthalmoscope images. The main advantage of this technology is the improved signal-to-noise ratio and the ability to do follow-up examinations at exactly the same position.
Macular raster scans were performed after pupil dilation to image the foveal region using the follow up function during the entire study.
To detect differences in CPT and CMMT between the groups, we used an independent-samples t test and a paired t test, respectively. A P value of less than .05 was considered statistically significant. Statistical analysis was performed by SPSS 17.0 software (SPSS Inc, Chicago, Illinois, USA).
The study patients were aged 69 ± 5 years (mean ± standard deviation [SD]) and 65 ± 10 years in the PPV and control group, respectively. Fourteen patients in the PPV group and 3 in the control group were female. Nineteen of 20 patients were followed up until month 3; 1 patient was not seen at the final visit because of illness. The mean period from PPV to cataract surgery was 11.5 months (range, 4-16 months). The duration of phacoemulsification and surgery, respectively, were 42.7 ± 11.9 sec and 12.1 ± 3 min for the PPV group and 32.3 ± 16.3 sec and 13.7 ± 4 min for the control group. No clinical flare or cellular reaction was observed in any patient at the 1-month postoperative visit.
The baseline mean ± SD BCVA was 0.3 ± 0.18 Snellen lines, which improved significantly to 0.85 ± 0.18 at 3 months after cataract surgery. Mean (± SD) CMMT was 393 (± 44) μm at baseline and increased significantly to 408 (± 47) μm at month 3 ( P < .05). In the PPV group 8 (46%) patients developed an increase of CMMT more than 35 μm 1 month after cataract surgery.
Three months after surgery, the area of retinal thickening (ART) was significantly greater in most patients compared with baseline values ( P < .05). Mean (± SD) area of retinal thickening was 29 608 ± 17 312 pixels (pix) 2 at baseline and increased significantly to 35 908 ± 17 637 pix 2 at 3 months ( P ≤ .001). Original data for all measurements are presented in the Table . Figure 1 presents the BCVA, retinal thickness, and size of area of retinal thickening over the 3-month follow-up time.
|Baseline||1 Week||1 Month||3 Months|
|RV (mm 3 )||0.31||0.03||0.3||0.25||0.36||0.31||0.03||0.31||0.25||0.37||0.34||0.06||0.35||0.25||0.44||0.32||0.04||0.32||0.25||0.38|
|ART (pix 2 )||29 608||17 312||25 388||6065||77 204||32 425||17 746||29 980||7607||79 493||39 415||19 209||45 110||9668||85 595||35 908||17 637||31 593||11 845||85 381|