Street Smarts

Contact Lenses 101

By Dan Beck, OD Leland, N.C.

Contact lens wearers comprise a major portion of most optometric practices. Given this fact, it’s amazing how little hands-on experience optometric students get in working with these patients during their school training. Oh sure, the schools will thoroughly review the mathematics of back toric and bi-toric RGPs, but that knowledge is rarely, if ever, needed in real practice. Since soft contact lenses are about 95% of the lenses worn and sold in this country, let’s concentrate on them. Here are a few basic contact lens tips that will help keep your patients happy.

1) Don’t forget about the vertex distance.

This is about as basic as it gets, yet I still see many contact lens scripts, and new patients, where this rule was completely ignored. Any spectacle prescription that’s over 5.00D must be adjusted in the contact lens prescription. A -7.00 in eyeglasses is about a -6.50 in contact lenses. Conversely, a +7.00 in eyeglasses is about a +7.50 in contact lenses. Many patients don’t complain because they’re young and can accommodate despite the extra power, but that’s not good patient care and it really becomes an issue as patients get older.

2) In toric contact lenses, less is more.

It has always baffled me that doctors will ignore a couple steps of cylinder and put a patient in a spherical lens, but will fully correct the cylinder when they decide to use a toric lens. If a patient has -1.25 cylinder in their eyeglasses, correcting -.75 in the contact lenses will generally give the best results. In addition, the more cylinder you put into a toric lens, the less it can rotate before blur occurs.

3) Bifocal contact lens wearers will never see as clearly as they would with their eyeglasses.

Don’t believe the hype about these lenses. I don’t care what the contact lens reps tell you. The very nature of simultaneous vision lenses, which is what all soft bifocal contact lenses are, is that the distance and near correction are both in front of the eye at the same time. No matter how well the patient is fitted and corrected, there will always be overlap of distance focal length into near and vice versa.

You have to thoroughly explain to presbyopic patients BEFORE you attempt to fit them with bifocal contact lenses that their vision will be different than with their eyeglasses. You can have happy bifocal contact lens wearers — as long as they’re told in advance that they’ll be giving up some clarity to enjoy the benefits of contact lenses. If you explain this, you’ll have less complaints and repeat visits.

Following a few basic rules will help make contact lens fitting fun and rewarding. nOD