I'd like to spend this column going over a few mid-cap companies that I really like. Three in particular stand out as solid, long-term wealth-creators for investors, in my opinion.

Long-time readers of this column will know of my affinity for investment themes. Two investment themes that I like very much are the eye care business and the pet care business. No matter what happens to the economy, people still need to feed and vaccinate their pets, and everyone needs to be able to see correctly.

I've always had an affinity for VCA Antech (NASDAQ/WOOF). This company operates the largest network of freestanding veterinary hospitals and veterinary-exclusive clinical laboratories in the country. Based in Los Angeles, the company operates as Veterinary Centers of America Inc., offering a full range of medical and surgical services for small and companion animals. The company's veterinary diagnostic laboratory network serves all 50 states, providing sophisticated testing and consulting services to other small veterinarians.

Another favorite is Luxottica Group (NYSE/LUX). This Italian company operates nearly 5,500 optical retail stores mainly in North America and the Asia-Pacific region, selling premium eye glasses brands. The company's brands include"Ray-Ban, Vogue, Persol, Arnette and REVO and licenses Bvlgari, Chanel, Donna Karan, Prada, Ralph Lauren, and Versace. Retail distribution is done through the company's own subsidiaries that include LensCrafters Inc., Sunglass Hut International Inc., and O.P.S.M. Group Limited.

Finally, another mid-cap company that's proven itself as a solid wealth creator is Daktronics Inc. (NASDAQ/DAKT). This company is in the business of manufacturing and installing display screens. The company makes everything from large, computer- programmed scoreboards that are installed in large sports stadiums, to road signs and ticker tapes. The company is based in Brookings, South Dakota, and is considered to be one of the best in the scoreboard/signage business.

All three of these mid-cap companies have been written about in this column before. These companies have all the traits I usually look for in an equity investment. Even though these stocks have appreciated considerably over the last several years, I still think they make for a welcome addition to any long-term, speculative portfolio.