Commentary: Refractive outcomes of a single step and a two-step approach for silicone oil removal and cataract surgery.

Poly dimethyl siloxane (silicone oil) has remained a very useful internal tamponading agent for repairing complex retinal detachments. Despite the extensive list of complications described with the long-term use of this agent,[1] its use has not diminished, thanks to the inability to find better agents. Hence, surgeons always attempt to remove the oil at the earliest opportunity. Removal of oil is a major step in the overall management of the eye. In addition to removing the oil, it involves

Reducing the risk of recurrence of retinal detachment following the oil removal by appropriate maneuvers.

Managing epimacular membranes that often coexist

Managing secondary glaucoma that may coexist

Managing coexisting cataract.

Managing the lens in a phakic eye with silicone oil poses specific challenges. The May 2009 issue of IJO carried an article addressing the issue of refractive outcome after a single-step versus two-step approach for managing silicone oil filled eyes with cataract.[2]

While managing a phakic eye with silicone oil, one may face the following permutations and combinations.

Lens: Clear/nuclear sclerosis/posterior subcapsular cataract (PSCC)/combination of nuclear sclerosis and PSCC

Effect of lens haze on the visual function (estimate): None/minimal/moderate/severe

Stability of the lens: Stable/significant zonular dehiscence

State of silicone oil: Clear/minimal emulsification/severe emulsification

Retinal status: Attached retina totally/peripheral Retinal detachment (RD) with no visible break/peripheral RD with visible break/difficult to assess retinal status well (due to cataract or emulsification or both)

Intra ocular pressure: Normal/high/low but not too low (around 8 mm/hg)/very low (<8 mm/hg).

The management would dependent on all of the above factors.

Following surgery, the concerns one faces are as follows:

The risk of recurrent retinal detachment

The risk of profuse hypotony

The risk of persistent glaucoma

The risk of improper refractive correction.

In terms of functionality, the first three have more grave consequences than the improper refractive correction. However, for a patient who has good visual recovery and stable and good anatomical result from the retinal reattachment surgery, improper refractive outcome could be an important and annoying negative outcome.

From the retinologist's point of view, if one sees a stable retina following silicone oil removal with normal intra ocular pressure (IOP), the job is considered well done, even if the patient requires corrective glasses much more than expected. This article puts this issue in the perspective forcing the retinologist to rethink on the priorities and include poor refractive outcome as an important undesirable outcome in addition to the more complicated issues alluded to above.

Getting an accurate and reliable axial length measurement is the key issue in intra ocular lens (IOL) power calculation and this is thwarted by the presence of silicone oil. Ultrasound biometry (with adjustment of the speed of sound in vitreous cavity to 987 m/s) has been shown to be reasonably accurate with both 1,000 and 5,000 cst silicone oil. A deviation in final refraction of within two diopters was found in 72.4%.[3] This study has shown that error was more in eyes with greater axial length. Several studies have shown that the IOL master is more accurate in measuring axial length compared with the ultrasound-based A scan measurement in silicone oil filled eyes.[456] However, dense cataracts and poor fixation by patient can pose problems in getting accurate measurements even with IOL master. Poor fixation may not be an uncommon association in the circumstances of a silicone filled eye.

Considering the above, the following may be an acceptable approach when planning silicone oil removal with cataract surgery.

Measure axial length with IOL master when available and possible. If measurements are possible, one can proceed with combined surgery

If good measurements are possible and repeatable with ultrasound biometry, and if they correlate with known information (pre-op refractive error/fellow eye status, etc.), one can proceed with planned combined surgery

In known cases of high myopia (a not uncommon association with retinal detachments needing silicone oil tamponade), and where axial length measurements are not possible with both IOL master and ultrasound biometry, the following approach is reasonable:

Where the lens opacity is not very dense (one should be able to judge the retinal status intraoperatively after removal of oil, as well as do additional procedures, such as membrane peeling, endolaser, etc.), it is best to do the cataract surgery a few weeks after removal of oil

Where the cataract is dense and does not permit much of posterior segment surgery, it is best to remove the cataract, remove the oil, and perform additional posterior segment maneuvers as needed, but not place the IOL. One can keep the pupil mobile by using tropicamide or cyclopentolate once a day and at the earliest opportunity place a secondary IOL based on postoperative measurements for IOL power calculation. In most cases, one is only able to place the IOL in the sulcus since the capsular bag might not be open. On occasions, one may come across very highly myopic eyes that may become emmetropic or slightly myopic in the aphakic state and may not need IOL implantation. They may of course need early Yag capsulotomy since posterior capsule opacification will occur very fast in the absence of the IOL.

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Conflicts of interest

There are no conflicts of interest.