diabetic vitrectomy

DIABETIC VITREORETINAL (VR) SUGERY-

Robert Machemer [1970] introduced pars plana vitrectomy (PPV) .Original indications for pars plana vitrectomy in diabetic retinopathy include: (1) persistent vitreous hemorrhage, (2) tractive detachment of the macula, (3) combined tractional and rhegmatogenous retinal detachment, and (4) progressive fibrovascular proliferation despite panretinal photocoagulation (PRP) [Ho et al., 1992].

CURRENT INDICATIONS FOR DIABETIC VR SURGERY –

The patient should be a controlled diabetic on regular medication.

MEDIA OPACITIES

• Non-clearing Hemorrhage - (Vitreous, Subhyaloid, Premacular) is the commonest indication. In these cases adequate panretinal photocoagulation (PRP) is not possible due to hemorrhage.

TRACTION

• Tractional retilnal detachment (TRD) threatening / involving macula must be treated urgently with VR surgery.
• Combined TRD & rhegmatogenous retinal detachment (RRD) even if macula is not involved because subretinal fluid is likely to spread quickly to involve macula.
• Macular edema associated with taut  persistently attached post hyaloid  (vitreo-macular traction syndrome)

OTHER INDICATIONS

• Ghost cell / hemolytic glaucoma
• Anterior hyaloid fibro-vascular proliferation
• Epiretinal membrane

AIM OF VITREORETINAL SURGERY IN DIABETES -

First and foremost aim of diabetic VR surgery is restoration of vision by achieving clear ocular media, restoring normal anatomy, relieving traction, reattachment of macula, complete vitreous removal. Second aim is to halt progression of PDR-  prevent further neovascularization by removal of vitreous gel thus  removing the scaffold along which fibrovascular tissue can proliferate, relief of traction on retinal vessels may also improve blood flow within these vessels and reduce leakage. In addition, unrestricted circulation of fluid in the vitreous cavity after vitrectomy seems to improve the oxygen supply to the inner retina and prevents accumulation of vasoactive cytokines in the retina. Intraoperative endolaser coagulation may reduce rates of postoperative vitreous hemorrhage ^[6] & may stabilize the proliferative process.

COMPLICATIONS OF VITREORETINAL SURGERY –

1.  Vitreous hemorrhage – in approx 10–20% of patients. It is common with very severe and active retinopathy at the time of surgery. Bleeding can occur immediately postoperatively or several months post surgery from ischaemically driven entry site neovascularization.

2. Retinal tears and holes may be caused by a) instrument passing through the sclerotomies, b) related to posterior vitreous detachment generation or c) iatrogenic from instrument and tissue trauma during dissection.

3. Raised IOP following vitrectomy may be caused by:

● Over-expansion of intraocular gas used as a tamponade in the first few postoperative days;

● Ghost cell (‘old’ red blood cells) or steroid-induced glaucoma;

● Silicone oil-induced glaucoma caused by-a) intraoperative overfill b) early glaucoma- oil entering the anterior chamber or blocking the pupil, c) late silicone oil-induced glaucoma due to blockage of the trabecular meshwork by emulsified oil in the anterior chamber;

       ● Rubeotic vessel occluding trabecular meshwork.

4. Cataracts – silicone oil induced, lens touch by instrument.

5. Corneal epithelial problems related to diabetic corneal disease due to use of wide angle

6. Re-detachment

7. Proliferative vitreoretinopathy (PVR)

8. Macular pucker

9. Cystoid macular edema

10. Endophthalmitis

11. Pthisis