Double Endotamponade With Perfluorodecalin and Silicone Oil in Retinal Detachment Surgery.

Purpose: to assess the efficacy and safety of double tamponade versus silicone oil tamponade.

Design: parallel-group study with balanced \[1:1\] stratified block randomization. Eligible participants are all adults aged 18 or over with first diagnosed rhegmatogenous total retinal detachment with retinal breaks located both in upper and lower retina. Also investigators include those patients with total retinal detachment with proliferative vitreoretinopathy (PVR) in which it is impossible to remove epiretinal membranes completely during the surgery (with arbitrary retinal breaks localization). Exclusion criteria are severe concomitant eye pathologies (glaucoma, diabetic retinopathy, macular hole, traumas etc) and eye length more than 27mm.

Patients are randomized in two groups (test group and control group).

In the test group patients undergo subtotal vitrectomy, epiretinal membrane removal, perfluorodecalin (PFD) tamponade, retinal photocoagulation. After that the surgeon replaces ½ of PFD volume by "conventional" SO (with density less than one of water). The result is vitreous cavity (VC) filled in a half with PFD and in another half - with SO. In the control group patients undergo subtotal vitrectomy, epiretinal membrane removal, PFD tamponade, retinal photocoagulation and PFD-SO exchange, so the result is VC filled with "conventional" or heavy SO, depending on predominant retinal breaks location. 30 days after the surgery in both groups tamponing agents are removed from VC and VC is filled with sulfur hexafluoride gas (SF6) which dissolves during 1 month. Follow-up is at least 12 months.

Along with standard examinations, after SF6 gas dissolution investigators perform spectral optical coherence tomography (OCT) and microperimetry. With OCT investigators measure thickness of retinal inner and outer nuclear layers. With microperimetry investigators determine light sensitivity in 12° and 4° zones from the fixation point.

Outcome measures: reattachment rate, best corrected visual acuity (BCVA), intraocular pressure (IOP), thicknesses of inner and outer nuclear layers according to the OCT, light sensitivity according to microperimetry, the rate of cataract formation in phakic eyes and the rate of tamponing agents emulsification.

For final analysis each group will include 145 participants.

OCT, microperimetry data and visual acuity will be compared between the groups using Student's t-test; proportions will be compared using exact Fisher's test.

The investigators include in the study all successive patients operated by the same surgeon. The study takes place in the S.N. Fyodorov "Eye Microsurgery" Federal State Institution located in Moscow, Russian Federation.

Patients are randomized in two groups with stratified block randomization. Strata were defined by combination of two binary prognostic factors: duration of retinal detachment (less than 3 months and ≥ 3 months) and PVR (present/absent).

Early interim analysis will be performed in order to reveal possible adverse effect of long-term PFD tamponade. For interim report success will mean the rate of post-surgical BCVA \>/= 20.200. Groups sizes for interim analysis will be 35 patients in each group. For interim analysis the investigators choose group sizes able to reveal 30% absolute difference in functional success rate with one-sided test (to detect possible toxicity of double tamponade for the retina) having power of 0.8 and significance level of p=0.05. In the final analysis success will mean retinal reattachment.

For final analysis each group will include 145 participants, so that the investigators are able to detect 15% difference in reattachment rate with power of 0.8 and significance level of p=0.05. Group sizes were computed with exact Fisher's test function in G\*Power 3.1.7 software (Erdfelder, Faul, \& Buchner).

OCT is performed with Cirrus HD-OCT system (Zeiss Meditec Inc). Microperimetry is performed with MP-1 microperimeter (Nidek). All the examinations are assessed by one ophthalmologist.

The allocation concealment is implemented with the help of a third party, who stores the randomization list and prepares envelopes containing directions what method of tamponade to employ in each particular patient. Patients are blind to the method of tamponade.

Eligibility Criteria:
Inclusion Criteria:

Adults aged 18 or over with firstly diagnosed rhegmatogenous total retinal detachment:

1. with retinal breaks located both in upper and lower retina; OR
2. with PVR which was impossible to remove completely during the surgery.

Exclusion Criteria:

1. severe concomitant eye pathologies (glaucoma, diabetic retinopathy, macular hole, traumas); OR
2. eye length more than 27mm.