This is a controversial topic in ophthalmology and the choice is often based on the worries about the risks related to the surgery, first of all endophtalmitis. The real fact is that  the choice should be driven by the general conditions of the patient taking into account age, cardiovascular risks, anaestesia risks and so on, coming at the extreme ( and not so extreme as demonstrated from several doctors worldwide ) consideration of operate simultaneously both eyes. Of course preoperative and postoperative care must be precise in case of existing conditions of the retina ( diabetes, CME, vascular conditions ) and of the whole eye ( uveitis, corneal diseases, et al. ) applying the most adequate surgical technique.

I agree with Dr. Maimone. In addition, decision which eye will be operated is individual depending on aforementioned factors and also eligibility of patient for two surgeries, in other case the best eye will be operated to restore a vision improving quality of life

Generally speaking, patients are wary about being operated in the better seeing eye.

My routine practice is to start with the worse BCVA eye regardless of the visual potential.

If the patient is not oriented about the co-morbidities he's suffering from in this eye he should be educated thoroughly about his condition, and a detailed informed consent should be collected, specifically mentioning the expected results.

In our experience patients' fear the most from the operation itself as much as or even more than their concern about their postoperative vision potential. Still it is much easier for them to accept the fact that it is their weaker eye that will be operated upon.

Following the surgery, patients realize that their fears were exaggerated, especially if the outcome is worth it (at least they have to have minor improvement, otherwise surgery is not indicated for them in the first place). Now they become much more confident into venturing into the more concerning fellow eye.

Of course this is a psychological approach more than a medical one. Nonetheless, other factors such as mentioned in Dr. Maimone's reply have to be taken into consideration.

I think there is no absolute rule to operate on better or worse eye. Choice to operate vary from case to case. There are patient factors, associated disease factors, surgeon  confidence about the result of surgery particularly to handle complications in these cases. All these factors are well said by the expert above.

In my practice, I perform about 80% Immediately Sequential Bilateral Cataract Surgery (ISBCS). Not coincidentally I see many patients who have "always, or for a very long time" had poor vision in one eye. They invariably come in seeking surgery in the good eye, which is getting a cataract.

I examine both eyes carefully, and then decide if the bad eye is truly amblyopic, or just has some uncorrected high anisometropia, or perhaps a macular scar or some other unfixable problem. I advise that patient about the generally excellent prognosis for the good eye, and then advise them of my best estimate of potential gain for the bad eye. Sometimes it means stating that they will regain peripheral vision, but the macular scar will result in an uncorrectable central scooter, and I explain what that means. But sometimes it means that the bad eye had really never undergone any serious attempt at optical correction with a contact lens, or anything else, and that despite their current cataract, it may actually have reasonable visual potential.

I believe it is detrimental to try to give the patient any accurate guesstimate, so I merely say that i am unsure how good their bad eye will be, but i am reasonably sure that i can make it better than it ever was before.

I always advise them to undergo ISBCS astray would generally not appreciate great benefit from an operation on only their bad eye. Such surgery will still leave them with preference for the goodbye, and they will usually say they are not much better than preop. 

So, we proceed with ISBCS. I let the patient choose which eye to do first. many want to do the worse eye first, as a sort of practice. Some want to do the good eye first, and then only bother with the bad eye after everything has gone well with the good eye - sort of a bonus. Most don't care which eye we do first as they are both being done the same day anyway.

Doing this, it has truly amazed me how much better amblyopic eyes are 1 month after surgery. i have done many eyes which were given prognoses of never better than 20/200, which achieved 20/40 , or better vision.  These patients are generally extremely happy.

The most difficult of these patients are those with small macular scars. Despite clear and repeated prep explanations, many of them repeatedly ask afterwards why that eye was not fixed as well as the other one, and want to know what went wrong with the surgery. Eventually, they understand.

In general ISBCS has probably benefitted this group of patients more than any other. many of them would have never undergone surgery on the bad eye otherwise, and attain surprisingly excellent results.

The visual potential and nature of the pathology of the worse eye is important. if there is a pathology with no chance to be treated (e.g,CNV scar in macula) performing surgery on the worse eye does not help that much.

i thinks the eye which will give optimum vision after surgery, should be operated first  

I totally agree with Rahmatnejad. If there is pathology already detected which has worst prognosis then it is no point to operate in worst eye first. But whatever is the case maybe if patient needs help with treatment where you need good view of the retina and cataracts are blocking your view then after you give patient good vision in good eye you should immediately proceed to operate in the worst eye also. 

In developing countries, patients are wary of surgery and have to often pay for the procedure. Operating on an eye which has poor prognosis may make the patient disheartened and it could be a waste of time and money. Operating on the good eye will make the patient mobile and improve his confidence. (However, the patient may then never come for surgery in the other eye).

Absolutely it depends on individual factors as pathologies, estimated improvement,costs, resources and availability of surgeons. If we can improve the worse eye a little bit we start with the worse eye or do sequential bilateral cataractsurgery (worse eye first). Last but not least the patient makes the decision hopefully based on our advice. 

The noted surgeon Dr Abhay Vasavada in a guest editorial for the EyeWorld journal of the APACRS (September 2016) has written:" ISBCS has been a matter of great controversy. In more developed countries surgeons are looking at this option. But in other parts of the world it may not be relevant. Potential endophthalmitis remains a major safety concern. We are also striving to achieve the goal of consistency in meeting our targeted refraction and visual outcomes." [my edit] The bottom line is that ISBCS remains a topic of concern specially with medico-legal issues (law suits) becoming common.