The incidence of PCME is reported to be between 0.1 and 3.8% in the literature8, however the incidence is higher when OCT is used.2 Notably though, the definition of PCME differs between the studies: some researchers define PCME as the 10% increase of CFT or intraretinal cysts appearrance9, while other researchers describe PCME as a 10% increase in CFT over previous PCME, along with a reduction in BCVA.10 In our study we described PCME as visual impairment or new onset metamorphopsia, associated with the presence of CME in fundus examination and OCT imaging such Yonekawa and Kim described in their study.1
In our study, the incidence of PCME was found as 3.1% (two eyes). Kusbeci et al. found 5.5% of cases with PCME, and an increase in CFT at 1 week, 1 month, 3 months and 6 months in their prospective study.11 According to the results of our study, the values of CFT on postoperative first and third months, were statistically significantly higher from preoperative values. Although PCME was seen on first month visits in our both cases, the retinal thicknesses did not return preoperative values on third month. This result shows that the normalization of posterior segment takes long time after phacoemulsification.
In our study, we aimed to query the effect of vitreomacular adhesion on existence of macular edema. The CFT of the eyes with VMA was thicker than non-VMA group on first month visit. This result confirmed our hypothesis. Duker et al. defined vitreomacular adhesion as perifoveal vitreous detachment with remaining vitreomacular attachment and unperturbed foveal morphologic features.7 This condition appears with OCT and is nearly always a result of vitreous aging. However in our study, the VMA group was younger than non-VMA group.
The etiology of PCME is thought to be inflammatory mediators which rise in the aqueous and vitreous humors, causing increased vascular permeability: destroyed retinal barrier leads fluids to extend to the fovea and causes macular edema.2 The changes in choroidal thickness after uneventful cataract surgery is a topic of interest. Previous studies have reported the changes in the choroid after successful cataract surgery. Odrobina and Lauda Ńska-Olszewska measured the choroidal thickness of the operated eye and fellow eye of the 28 patients who underwent uneventful cataract surgery and found that the average choroidal thickness of the operated eye, was statistically significantly lower than the fellow eye.12 The authors concluded that lower blood flow in operated eye may lead to PCME, however the effect of decreased blood flow on PCME is controversial. There are several studies demonstrating choroidal thickening after phacoemulsification cataract surgery.4,13 Falcao et al14, showed that there was no change in choroid in patients without retinal pathology after cataract surgery. Similarly in our study, we did not find any change in total choroidal thickness.
Ohsugi et al.demonstrated that after phacoemulsification of 100 eyes, IOP was significantly reduced at the postoperative 3 weeks, 3 months, and 6 months; CFT, SFCT were significantly increased and both CFT and SFCT were found to be inversely correlated with IOP increase.15 In our study, there was no statistically significant difference between the IOP values; the stability of IOP may be the cause of the constant values of total choroidal thickness.
Analysis of choroidal vascular layers as SCVL and LCVL has been a common method to clarify the effects of systemic and ocular disorders.16,17 The strength of our study was to investigate the two vascular layers of choroid after uneventful cataract surgery. In patients with vitreomacular adhesion, the LCVL was found to be thicker one week after cataract surgery. The thickening of large vessel layer continued on first and third month. We conclude that this change should be a result of tractional effect on choriocapillaris during surgery. Choriocapillaris layer might be pulled anteriorly by vitreous after completing phacoemulsification of lenticular fragments and the LCVL might be relatively thicker in the patients with VMA.
In our study, two eyes had PCME one month after phacoemulsification and both of these had vitreomacular adhesion. Vitreomacular adhesion, which is an early stage of vitreomacular traction, may have a mechanical effect on macula and induce macular edema. Copete et al. investigated the relationship among the existence of vitreoretinal interface abnormalities and the PCME formation after cataract operation.18 The researchers stated that VMA or vitreomacular traction detected by SD-OCT was not connected to the development of PCME and that the only factor associated with PCME was found to be the existence of nonsurgical ERM.18 On the contrary, with this study, we showed that the eyes having vitreomacular adhesion have higher risk of PCME after cataract surgery.
Anastasilakis et al. investigated the potential correlation between PCME incidence and vitreoretinal interface status, and found no significant relationship, however they found that the incidence of PCME was higher in patients with attached posterior vitreous.19 The authors concluded that intact vitreoretinal interface on macula may promote the transmission of the phaco energy.19 In our study, two patients with PCME had VMA and we concluded that the phaco energy may facilitate the traction on the areas of VMA and causes PCME.
Limitations
Limitations of our study include the small number of patients and not counting on the phacoemulsification time and power. On the other hand, the strengths of this study were evaluating the different layers of choroid before and after phacoemulsification, investigating nearly all components of posterior segment before and after operation, and the fact that all operations were performed by the same experienced surgeon.