Influence of Tamponade on Retinal Shift in Eyes Undergoing Vitrectomy for Rhegmatogenous Retinal Detachment: A Comparison of Gas Versus Silicone Oil in a Pakistani Population
Phase: NA
Conditions: Retinal Detachment Rhegmatogenous, Vitrectomy, Retina Disorder
Sponsor: Wardah

 
 
COVER PAGE 
Official Title of Study: 
Influence of Tamponade on Retinal Shift in Eyes Undergoing Vitrectomy for 
Rhegmatogenous Retinal Detachment: A Comparison of Gas versus Silicone Oil in a 
Pakistani Population 
ClinicalTrials.gov Identifier (NCT Number): 
NCTXXXXXXXX (replace with your assigned number) 
Document Date: 
March 26, 2026 
Document Type: 
(e.g., Protocol, Statistical Analysis Plan, Informed Consent, Investigator Brochure, etc.) 
Principal Investigator / Responsible Party: 
Dr. Abdul Sami Memon, Department of Ophthalmology and Visual Sciences, Aga Khan 
University Hospital, Karachi, Pakistan 
Version / Revision: 
(e.g., Version 1.0, March 9, 2026) 
 
 
Influence of Tamponade on Retinal Shift in Eyes Undergoing Vitrectomy for 
Rhegmatogenous Retinal Detachment Using Gas Versus Silicone Oil in the Pakistani 
Population 
 
Principal investigator: 
Dr Abdul Sami Memon 
Assistant professor 
Department of Ophthalmology and Visual Sciences 
AKUH 
abdul.sami@aku.edu 
Resident: 
Dr Wardah Moazzum 
Resident year IV 
Department of Ophthalmology and Visual Sciences 
AKUH 
wardah.moazzum@aku.edu 

INTRODUCTION 
Rhegmatogenous retinal detachment (RRD) has an incidence of 1 in 10,000 per year (1). Pars 
plana vitrectomy (PPV), first introduced by Machemer in 1972, remains one of the most 
effective surgical procedures for treating RRD. The use of intraocular tamponade agents such 
as gas and silicone oil is common. The choice of tamponade may influence postoperative 
outcomes, including the occurrence of retinal shift. 
Retinal shift can cause postoperative metamorphopsia, which is reported in up to 88% of 
patients with macula-off RRD (2). One theory for retinal shift is the residual subretinal fluid 
that displaces the retina due to gravity. Shiragami et al. used fundus autofluorescence (FAF) 
to identify this retinal shift in 2010 (3). The retinal displacement was visualized as 
hyperautofluorescent lines on FAF, later described as retinal vessel printings (RVPs) or RPE 
vessel ghosts (4). 
Fundus autofluorescence (FAF) is a non-invasive imaging technique that provides 
information about the health and function of the retinal pigment epithelium (RPE). 
Hyperautofluorescent lines along the retinal vessels in FAF images indicate previous 
locations of the vessels before retinal displacement. 
Recent studies have suggested a higher incidence of retinal shift in patients treated with gas 
tamponade compared to those treated with silicone oil. Dell'Omo et al. reported that 41.2% of 
patients who received gas tamponade experienced retinal displacement compared to only 
14.3% of those who received silicone oil (5). Similarly, Codenotti et al. found a 71.4% 
incidence of retinal displacement in patients who received gas tamponade, compared to only 
22.2% in those who received silicone oil (6). 
There is currently no local data on the incidence of retinal shift in patients undergoing PPV 
for RRD using different tamponade agents. Postoperative patient dissatisfaction due to visual 
distortion despite anatomical success warrants further investigation into factors contributing 
to retinal shift. 
OBJECTIVE 
To compare the incidence of retinal shift in eyes undergoing vitrectomy for RRD using gas 
versus silicone oil tamponade. 
OPERATIONAL DEFINITIONS 
• Rhegmatogenous Retinal Detachment (RRD): Separation of the neurosensory retina from 
the underlying RPE, associated with subretinal fluid and the presence of at least one full-
thickness retinal break. Diagnosis will be based on clinical examination and confirmed 
intraoperatively. 
• Vitrectomy: Standard 25-gauge pars plana vitrectomy performed as a primary surgical 
intervention for RRD. The surgery includes complete vitrectomy, release of vitreoretinal 
traction, laser photocoagulation or cryotherapy, and fluid-air exchange followed by 
tamponade with either gas or silicone oil. 
• Retinal Vessel Printings (RVPs): Hyperautofluorescent lines visible on FAF imaging, 
corresponding to previous locations of retinal vessels, indicating a shift in retinal position. 
Presence of RVPs is defined as a positive shift, whereas absence indicates no shift. 

• Refractive Error: High myopia is defined as a refractive error greater than -6.00 diopters. 
This will be considered a risk factor for retinal detachment. 
HYPOTHESIS 
Retinal shift following vitrectomy for RRD is influenced by the type of tamponade used (gas 
vs. silicone oil). 
MATERIALS AND METHODS 
Study Design: Randomized controlled trial 
Study Setting: Section of Ophthalmology and Visual Sciences, Department of Surgery, 
Aga Khan University Hospital (AKUH) 
 
Duration of Study: Patients will be recruited after ERC approval and followed up for 
one month postoperatively. The total duration of the study will be one year. 
 
Sample Size: Based on Dell’Omo et al.'s study (41.2% retinal shift in gas, 14.3% in 
silicone oil), with 90% power and 5% alpha, the minimum required sample size is 32. 
However, 80 patients will be included, 40 in each group. 
 
Inclusion Criteria: 
Patients with primary RRD 
Aged between 18 and 85 years 
Undergoing PPV at AKUH 
Exclusion Criteria: 
Eyes undergoing PPV for causes other than RRD 
Previous PPV 
Patients with incomplete reattachment 
Patients lost to follow-up 
Eyes with postoperative findings interfering with FAF, such as ERMs or redetachment 
 
Sampling Technique: Non-probability, consecutive sampling 
 
Randomization: Patients will be randomized into two groups: 
Group A (Gas Tamponade): Eyes undergoing PPV with gas (C3F8 or SF6) 
Group B (Silicone Oil Tamponade): Eyes undergoing PPV with silicone oil (PDMS) 
All surgeries will be performed by vitreoretinal surgeons with at least 10 years of 
experience. FAF will be performed on postoperative day 10 and at one month using 
Heidelberg Spectralis. FAF images will be assessed for vertical retinal displacement. The 
displacement is identified as hyperautofluorescent lines parallel to major retinal vessels 

indicating vertical deviation. The images will be independently evaluated by two trained 
retina specialists masked to the type of tamponade used. 
DATA ANALYSIS 
Data will be analyzed using SPSS version 23.0. For quantitative variables, age will be 
reported as either the mean ± standard deviation or the median with interquartile range, 
depending on the data distribution. Qualitative variables, including gender, side of eye, type 
of tamponade, and presence of retinal displacement, will be presented as frequencies and 
percentages. The incidence of retinal shift between the gas and silicone oil groups will be 
compared using the Chi-square or Fisher's exact test, as appropriate. A stratified analysis will 
be conducted to assess potential effect modifiers such as age, gender, and the extent of 
detachment. Post-stratification comparisons will be made using the Chi-square or Fisher's 
exact test. A p-value of ≤0.05 will be considered statistically significant. 
REFERENCES 
1. Sultan ZN, Agorogiannis EI, Taylor RH, et al. Retinal displacement following 
rhegmatogenous retinal detachment repair. BMJ Open Ophthalmology. 
2020;5:e000478. 
2. Bazvand F, Ghassemi F, Fadakar K, et al. Optical coherence tomography-based 
classification of macular involvement in rhegmatogenous retinal detachment for 
surgical and prognostic considerations. Int Ophthalmol. 2021;41(1):35-42. 
3. Shiragami C, Shiraga F, Nitta E, et al. Retinal displacement after vitrectomy for 
rhegmatogenous retinal detachment: optical coherence tomography and fundus 
autofluorescence study. Ophthalmology. 2010;117(1):86–92. 
4. Lee E, Kim JY, Lee JE, et al. Retinal displacement and metamorphopsia after 
vitrectomy for macula-off retinal detachment. Br J Ophthalmol. 2013;97(10):1297–
1302. 
5. Dell’Omo R, Mura M, Lesnik Oberstein SY, Bijl HM. Incidence of retinal 
displacement after vitrectomy for retinal detachment using different tamponades. 
Invest Ophthalmol Vis Sci. 2017;58(8):4994. 
6. Codenotti M, Iuliano L, Fogliato G, et al. Incidence of retinal displacement after 
simple retinal detachment repair with different tamponades. Retina. 2013;33(2):349–
355. 
7. Casswell AG, Gregor ZJ. Silicone oil removal. I. The effect on the complicated retinal 
detachment. Br J Ophthalmol. 1987;71(12):893–897.