Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of laser optics technologist II-VI (NASDAQ:IIVI) sank 12% today after its full-year guidance missed Wall Street expectations.

So what: II-VI's third-quarter results -- EPS of $0.25 on revenue of $145.2 million -- were just slightly below estimates, but downbeat guidance for the rest of the year reinforces concerns over slowing growth going forward. In fact, management blamed the weak outlook on softening demand across several of its business segments, giving investors little hope for a near-term turnaround. 

Now what: Management now sees full-year EPS of $0.84-0.89 on revenue of $550 million-$555 million, well below the consensus of $0.93 and $563.7 million. "We have experienced some cyclical softening in the optical communication market addressed primarily by our Near-Infrared Optics segment," CEO Francis Kramer cautioned. "In the Military and Materials segment, PRM continues to be affected by the start-up of its new rare earth product line. ... Demand for selenium and tellurium products continues to be low and, therefore, the pricing environment is a challenge." Of course, with the stock hitting a new 52-week low today and trading at a forward P/E of about 12, much of those headwinds might already be baked into the price.

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Fool contributor Brian Pacampara has no position in any stocks mentioned. The Motley Fool recommends II-VI. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.