The purpose of our study is to utilize AS-OCT to analyze the anterior segment morphological changes in the early postoperative period of patients who will undergo PPV with silicone oil injection.

1. Type of the study: A prospective comparative study.

2. Study Setting: Assiut university hospital.

3. Study subjects:

   1. Inclusion criteria:

      Patients suffering from different vitreo-retinal disorders (rhegmatogenous retinal detachment, diabetic vitreous hemorrhage, diabetic tractional retinal detachment) with either preserved crystalline lens or previous cataract surgery (at least 3 months prior to PPV) will be recruited

   2. Exclusion criteria:

      Patient with previous history of ocular trauma, co-existing glaucoma, co-existing anterior uveitis, complicated cataract surgery, IOL-related complications, previous vitreo-retinal surgery, visually significant cataract (necessitating combined phacoemulsification with PPV and SO) and significant corneal opacity will be excluded. If any significant post-PPV complication develops, patient will be excluded from the study.

   3. Sample Size Calculation:

      Thirty eyes (30 patients) will undergo PPV with SO tamponade and AS-OCT analysis prior to surgery and 1 week post-operatively to achieve study power of 80% with 0.05 significance.

      4 -Study tools (in detail, e.g., lab methods, instruments, steps, chemicals, …): All participants underwent best-corrected visual acuity (BCVA) by Snellen's chart, Slit lamp assessment of the anterior segment, dilated fundus examination, intra-ocular pressure (IOP) measurement by calibrated Goldmann Applanation Tonometer (GAT). Baseline Ophthalmic ultrasound and Axial length measurement will be obtained.

      Anterior segment OCT (AS-OCT) protocol All eyes will be examined by AS-OCT (Nidek RS-3000 Advance, Tokyo, Japan) 1-2 days prior to vitreo-retinal surgery and one week after surgery by single experienced physician. Poor fixation or poor image signal (less than 3/10) will exclude the patient from the study.

      Anterior segment OCT (AS-OCT) parameters The following anterior segment parameters will be evaluated; central and peripheral anterior chamber depth (cACD, pACD), anterior chamber angle (ACA) and central corneal thickness (CCT).

      5 -Research outcome measures:

   1. Primary (main):

      Mean change in central anterior chamber depth after PPV with SO tamponade.

   2. Secondary (subsidiary):

Mean change in peripheral anterior chamber depth, mean change in anterior chamber angle and mean change anterior chamber angle entry area.

Inclusion Criteria:

Patients suffering from different vitreo-retinal disorders (rhegmatogenous retinal detachment, diabetic vitreous hemorrhage, diabetic tractional retinal detachment) with either preserved crystalline lens or previous cataract surgery (at least 3 months prior to PPV) will be recruited

Exclusion Criteria:

Patient with previous history of ocular trauma, co-existing glaucoma, co-existing anterior uveitis, complicated cataract surgery, IOL-related complications, previous vitreo-retinal surgery, visually significant cataract (necessitating combined phacoemulsification with PPV and SO) and significant corneal opacity will be excluded. If any significant post-PPV complication develops, patient will be excluded from the study.