When we do cataract surgery, we remove a relatively thick human, crystalline lens and we replace it with a thin, man-made lens implant (IOL: intra-ocular lens). Because the human lens is about 4 mm thick while the IOL is just 1 mm thin, the vitreous will shift after cataract surgery. Most of our cataract patients are elderly, over the age of 60, and this also corresponds to the age where they develop normal, physiologic posterior vitreous detachments (PVD).
We tell people that everyone who lives long enough will get cataracts and that cataract surgery is the most commonly performed surgery in the USA. But we must also remember that all people who live long enough will also develop a PVD in each eye. Vitreo-macular traction (VMT) is when there are strong, persistent attachments to the macula, preventing a full posterior vitreous detachment (PVD).
With VMT, the fundoscopic exam can appear totally normal. It is very difficult to detect VMT with simple an examination of the retina using the indirect ophthalmoscope, the direct ophthalmoscope, or binocular slit-lamp fundoscopy with condensing lenses. If you do not do a pre-operative OCT (Ocular Coherence Tomography) testing on cataract patients, you will likely not be able to detect VMT before cataract surgery .
The VMT patients have partial liquefaction of vitreous but only partial separation of the vitreous face from the macula can develop VMT. The VMT can be a transient situation and once the PVD is complete, it may largely resolve. But if the VMT is persistent it can lead to other maculopathies such as macular pucker and macular hole. The danger of cataract surgery in the setting of VMT is that the shift of the vitreous after replacing the 4 mm thick crystalline lens with the 1 mm thin IOL, can lead to a sudden PVD which may have enough force to cause a full-thickness macular hole, cystoid macular edema, and poor vision for our patients. With cystoid macular edema the vision could drop to 20/100 to 20/200 and with a full-thickness macular hole it would drop to 20/400 or worse.
If you see VMT on the OCT exam at the cataract consultation, refer the patient to a trusted vitreo-retinal colleague first and delay the cataract surgery. The treatment of VMT is typically one of three options:
- Observation. Follow the OCT scans serially every few months and monitor the patient. Once the PVD is complete, there is a good chance that the VMT will be resolved and the patient can then have cataract surgery. If the PVD progression produces a macular hole, then a pars plana vitretcomy may be required for repair.
- Injection of lytic agents. Medications like ocriplasmin can help complete the PVD and resolve the VMT. There may be side effects from the ocriplasmin such as induced weakness of zonular structures and the success rate is not perfect.
- Pars plana vitrectomy. Surgery can be performed to complete the PVD and release the traction on the macula. The surgery is largely successful with a low rate of complications. The primary complication is that vitrectomy can increase the rate of cataract progression, but since we are planning cataract surgery anyway, this is not much of an issue.
Wait until the VMT is resolved, either spontaneously or through intervention, before proceeding with cataract surgery. You will be much happier and so will your patients.
Here is a video of cataract surgery in a patient with a prior pars plana vitrectomy.