Last year, all three indexes slipped into a bear market. They haven't quite made it into bull territory yet, but they've since recovered a lot of ground. The S&P 500, for example, has climbed about 14% since the start of the year.

Of course, stocks across industries are leading indexes higher. And some companies even are outperforming. Importantly, certain stocks with momentum make great buying opportunities today. That's because their bright long-term prospects mean they could climb much higher over time. Let's check out two top healthcare stocks that have defied the bear market -- and that could supercharge your portfolio over the long haul.

1. CRISPR Therapeutics

CRISPR Therapeutics (CRSP 0.59%) is at the start of what could be a big growth story. The company specializes in CRISPR/Cas9 gene editing. This involves cutting DNA in a particular area to allow a natural repair process to take over. It's a technique CRISPR is applying to treat genetic diseases.

The biotech company and partner Vertex Pharmaceuticals recently submitted a candidate using this technology for regulatory approval. Exa-cel is designed as a one-time curative treatment for blood disorders sickle cell disease and beta thalassemia. The U.S. Food and Drug Administration plans to decide on the sickle cell indication in December and on beta thalassemia in March of next year.

A potential regulatory nod could be huge for CRISPR. Exa-cel would become the company's first product. So, an approval would represent product revenue and a vote of confidence for CRISPR's technology. The company also has a pipeline of other candidates that rely on gene editing. And one of those -- an immuno-oncology candidate known as CTX-110 -- is involved in a trial that could support regulatory approval.

Even considering the gains so far this year, CRISPR stock could go a lot farther over time. That's as product revenue starts rolling in -- and as the company licenses its innovative technology to others. It's already licensed its gene-editing technique to Vertex for Vertex's type 1 diabetes program. So, over time, others also may see this as a valuable development tool.

2. Intuitive Surgical

Intuitive Surgical (ISRG 0.34%) is the global leader in robotic surgery. And we're talking about a growing market. At a compound annual growth rate of more than 16%, the global robotic surgery market is expected to reach $18 billion by 2027, according to Markets and Markets.

It's very likely Intuitive will maintain its leadership. For two reasons. First, surgical robots are million-dollar investments. So, healthcare facilities are unlikely to switch if they're satisfied with the product they've already bought or leased. Second, most surgeons train on Intuitive's flagship Da Vinci system. They probably will want to stick with this system they know well.

There's another reason to like Intuitive. And it has to do with the company's revenue model. Intuitive actually generates more revenue from selling instruments and accessories than it does from selling its robots. These are elements that must be replaced for each procedure. This is positive because it means every robot sold represents recurrent revenue.

Finally, Intuitive itself is optimistic about its own business. A sign of that? In the third quarter of last year, the company bought back $1 billion of common stock. If Intuitive is investing in itself, we can be sure it sees a bright future ahead. And that's another reason to believe that this top stock can keep on performing.