http://www.dailymotion.com/video/x15ytai

Background:

Silicone oil tamponade of vitreous cavity (VC) is widely used in the surgery of retinal detachments. Tamponade quality determines anatomical outcome. For a variety of reasons it is practically impossible to create an ideal tamponade with silicone oil. “Conventional” silicone oil floats upwards in the vitreous cavity. This results in a good tamponade of the upper retina, but leaves the lower retina without an effective tamponade. On the contrary, heavy silicone oil sinks and provides less effective support of the upper retina.

Another group of heavier substances, the perfluorocarbon liquids (PFCL), have gained an important role in vitreoretinal surgery. PFCL are recommended to be removed at the end of surgical operation. The fixed notion that long-term use of PFCL is dangerous for the retina is based upon experimental reports. Meanwhile, some experimentaland clinical data show no retinal degeneration with PFCL left in vitreous cavity for several weeks.

In this study double endotamponade with perfluorodecalin (PFD) and silicone oil was performed. The VC was filled for 50% of its volume with PFD and for 50% with silicone oil.

Advantages:

Patients did not need to maintain any posture since PFD provides support to the inferior retina and silicone oil — to the superior retina.

The purpose of this study was to evaluate safety of VC double tamponade during 30 days period.

Materials & Methods:

Experimental study.

A combination of silicone oil and PFD was injected in VC of right eyes of 10 rabbits after vitreous removal. Tamponade substances remained in VC for 30 days. During that period slit lamp examinations, clinical blood analysis and biochemical blood analysis were performed. Then rabbits were sacrificed and histological examination of the retina was performed. Retinal structure was compared between operated and fellow eyes.

Clinical study.

Inclusion criteria were: total retinal detachment with retinal breaks located in both upper and lower retina. Patients with severe concomitant eye pathologies (glaucoma, diabetic retinopathy, traumas etc.) were excluded from the study. All patients underwent subtotal vitrectomy, epiretinal membrane removal, PFCL tamponade and retinal photocoagulation. Patients were randomized in two groups. In a study group the VC was filled for 50% of its volume with PFD and for 50% with “conventional” silicone oil. In a control group surgery was finished with “conventional” or heavy silicone oil tamponade, depending on predominant retinal breaks location. 1 month after the surgery in both groups we removed tamponade agents from VC and filled it with SF6. Groups characteristics are shown in Table 1. All differences between groups were statistically insignificant.

Table 1: Characteristics of the patients

Parameters Study group
(n=26) Control group
(n=20)
Age, years (mean±SD, range) 53.5±13.7 (35–67) 54.6±11.3 (29–63)
Sex, m/f 11/15 12/8
BCVA (50, 25, 75 percentiles) 0.02 (Light projection –0.06) 0.04 (Light projection –0.08)
Detachment duration, months (mean±SD) 3.02±2.08 2.83±1.46
Eyes phakic/pseudophakic 16/10 9/11

 

Along with standard examinations including bio microscopy, indirect ophthalmoscopy, ultrasound examination etc., after SF6 gas dissolution we performed spectral optical coherence tomography (OCT) and microperimetry. According to the OCT we measured thickness of retinal inner and outer nuclear layers. Mean difference in thicknesses between operated and fellow eyes was compared between the study group and the control group.

According to microperimetry we determined light sensitivity in 12° and 4° zones from the fixation point.

Results:

Experimental study.

All rabbits showed no signs of eye inflammation, the retinal architecture was intact. Tamponade substances’ emulsification was observed in 1 eye (10%) 24 days after surgery.

Clinical study.

Anatomic success difference between groups was statistically insignificant but there was a trend to better anatomic outcome in the study group (Table 2). In control group there were fewer cases of post-surgical cataract and tamponing agents’ emulsification (p>0.05).

Table 2: Surgery outcome

Parameter Study group (n=26) Control group (n=20)
Anatomic success 1 month after surgery 21 (81%) 13 (65%)
Visual acuity (mean±SD) 0.17±0.15 0.19±0.14
Phacoemulsification (cases/phakic eyes) 12/16 (75%) 5/9 (56%)
Tamponing agents emulsification 5/26 0/20

 

All differences are statistically insignificant.

Table 3 contains OCT data analysis. It hasn’t revealed statistically significant differences between the study group and the control group. In both groups there was statistically significant thinning of nuclear layers compared to fellow eye (p < 0.05).

Table 3: Difference in nuclear layers’ thickness between operated and fellow eyes after surgery (µm, mean ± SD)

Layer Study group Control group
Inner nuclear layer 5.25±2.16* 4.17±2.02*
Outer nuclear layer 2.07±0.78* 2.05±0.92*

 

In microperimetry analysis we found no significant differences between the groups (Table 5). In both groups treated eyes had lower average light sensitivity in 4° area from the fixation point compared to that in 12° area (p<0.05, Table 4). This can be explained by the fact that foveal area lacks vessels and thus suffers more from hypoxia in retinal detachments.

Table 4: Decrease in light sensitivity (compared to fellow eye) after tamponade removal according to microperimetry, dB

Area Study group Control group
4° area 7.0±3.2 6.8±3.9
12° area 10.1±1.1 11.2±2.0

 

Differences between groups are insignificant.

Additionally we compared light sensitivity in upper and lower vessel arcade areas in test group (double tamponade) looking for possible differences in retinal areas contacted with PFCL and silicone oil. We found no decrease in light sensitivity in lower vessel arcade area (9.4±2.9 dB) compared to upper vessel arcade area (9.0±4.1 dB), which suggests there is no adverse effect of PFCL on retina.

Discussion:

Double tamponade technique allows increasing quality of VC tamponade by decreasing untamponaded volume in VC and unsupported area of retina. Double tamponade shows a trend to better anatomic success of surgery of complicated retinal detachments with retinal breaks localized both in upper and lower retina.

Take Home Message:

30-days double tamponade with PFD and silicone oil is safe. This was confirmed during experiment and by clinical analyses of retinal structure and functional outcome using OCT and microperimetry.