Cold Balanced Salt Eye Solution use during Phacoemulsification prevents Postop Macular Thickening
Cystoid macular edema (CME) following cataract surgery is a common and well recognized complication. CME may also occur in patients who do not present any risk factors, such as diabetic retinopathy and other retinal pathologies. The exact pathomechanism is not known and is likely to be multifactorial; however, surgical trauma to the iris, ciliary body, and lens epithelial cells causes release of phospholipids, and thereby release of prostaglandins or other inflammatory mediators.
The role played by cytokines, prostaglandins, and thromboxane in the inflammatory response in the anterior chamber after cataract surgery is well known. The inflammatory mediators stimulate the breakdown of the blood–retinal barrier, resulting in the accumulation of intraretinal fluid, leading to macular thickening and edema. Topical non-steroidal anti-inflammatory drugs (NSAIDs) are usually designed to prevent CME after cataract surgery in patients at risk, not to treat inflammation of the posterior segment of the eye.
Meduri et al performed a study to evaluate the role of intraoperative cold irrigating eye balanced salt solution (BSS) in influencing the central retinal thickness and, therefore, in preventing the possible development of postoperative CME (increase in retinal thickness of at least 10% from baseline caused by multiple pseudocysts in the macula). This could be useful in understanding how to eliminate a modifiable risk factor for complications during phacoemulsification cataract surgery.
In this prospective, single-center study, 100 eyes of 50 patients (26 males and 24 females) were evaluated with spectral domain optical coherence tomography (SD-OCT) before and after phacoemulsification for senile cataract.
The baseline ophthalmic examination performed preoperatively included slit-lamp evaluation, intraocular pressure (IOP), fundus examination, and a volumetric assessment of the central retinal using the "fast macular volume" preset.
All patients were pretreated 3 days prior to the surgery with antiseptic solution, 1% sodium hypochlorite bid to the periorbital skin, and 0.3% ofloxacin 1 gtt tid. Patients had instilled one drop of topical tropicamide and phenylephrine (0.28 mg/5.4 mg) 20 minutes before surgery.
Eyes were randomly divided into two groups based on the irrigating solution used during surgery: Group 1, 50 eyes received intraoperative irrigating solution at room temperature (~20.0±0.1°C); and Group 2, 50 fellow eyes received cold intraoperative irrigating solution (2.7±0.1°C). Changes in central macular thickness (CMT) were evaluated in both groups by SD-OCT macular raster scan for the nine Early Treatment of Diabetic Retinopathy Study (ETDRS) subfields and total macular volume, performed pre-surgery, and 1 and 4 weeks post-surgery.
After the surgery, each patient was treated for 4 weeks qid with artificial tears with a combination of cortisone and antibiotics (betamethasone 2 mg/mL, chloramphenicol 5 mg/mL) gtt and bromfenac 0.9 mg/mL gtt tid. None of the patients had any intraoperative complications.
RESULTS:
- No statistically significant differences were observed between the two groups in preoperative parameters such as axial length, anterior chamber depth, IOP, BCVA, or endothelial cell count.
- Despite there being no significant differences in variables between the two groups preoperatively, significant increases in CMT were observed at 1 week after surgery in both groups (p=0.02 and p=0.03, respectively), as well as in total macular volume (p< 0.0001 and p=0.02, respectively).
- Inter-subgroup analysis showed a significant reduction in CMT (p=0.03) and total macular volume (p=0.001) at 1 week post-surgery in Group 2 compared to Group 1, whereas no significant differences were observed at 4 weeks.
- At 1 and 4 weeks after surgery, there was a significant change in BCVA in both groups (p< 0.0001), whereas no significant differences were observed at 1 and 4 weeks between the two groups.
- There were significant decrease in the endothelial cell count in both groups after surgery, but the decrease was significantly higher in Group 1 (p <0.0001).
The most frequent postoperative complication of cataract surgery is CME, which, in most cases, evolves to a spontaneous resolution. In many cases after cataract surgery, it is possible to detect a subclinical increase in macular thickness; usually, a higher incidence of edema occurs 4–6 weeks after the phacoemulsification, with a recovery to baseline values around 6 months after surgery. However, visual loss can affect a few patients.
The damage caused by the light, the vitreoretinal traction, the timing, and the energy of the phacoemulsification, and, above all, the increased levels of cytokines, prostaglandins, and thromboxane, may be linked to the fluid retention, thus influencing the progression of the edema.
The findings showed a beneficial role of the cooled BSS during cataract surgery, reducing the inflammatory reaction and, consequently, the breakdown of the blood– retinal barrier that may lead to macular edema However, at 4 weeks no significant changes in CMT were observed in either group. This could also be related to the reduced inflammation as an effect of the anti-inflammatory treatment with bromfenac throughout the follow-up period. Although an increased CMT was observed in both groups, no cases of CME were recognized 4 weeks post phacoemulsification.
Moreover, after surgery, there was a significant reduction in the endothelial cell count in eyes that received a room temperature BSS, suggesting the induction of damage in corneal cells during phacoemulsification; in contrast, reduced surgical stress using cooled BSS during phacoemulsification was demonstrated by our previous clinical findings.
This prospective randomized study opened up new perspectives for the use of the cooled irrigating eye solution during phacoemulsification in preventing the possible development of postoperative macular thickening. This clinical evidence shows that the use of a cold irrigating eye solution plays a protective role on the macula, and thus the development of CME in eyes undergoing cataract surgery.
However, although authors achieved encouraging results with this low-cost procedure, the study presents a few limitations, such as the small number of eyes, short follow-up, and the procedures being performed by a single surgeon. A longer randomized clinical study is necessary to confirm the validity of this investigation. Nevertheless, this study may pave the way towards the easy diffusion of this user-friendly technique.
Source: Meduri et al; Clinical Ophthalmology 2021:15 2519–2526
