Short answer: single vision lenses correct one distance (near or far) and suit most prescriptions under 40; bifocals correct two distances with a visible line dividing them and remain popular for their lower price and predictable fit; progressives correct a full range from distance to near with no visible line, at a higher price point, and are the modern standard recommendation for presbyopia once budget allows.
A single vision lens corrects one field of vision — either distance (for myopia/nearsightedness) or near (for hyperopia or reading), ground to a uniform power across the entire lens. This covers the large majority of prescriptions, particularly for wearers under about 40 who haven't yet developed presbyopia (the age-related loss of near-focusing ability that typically begins in the mid-40s). Single vision is the simplest, most affordable, and most forgiving lens type to fit — there's no adaptation period, and any frame shape works without constraint.
Bifocal lenses combine a distance correction in the main lens body with a smaller reading segment (usually visible as a line in the lower portion of the lens), giving the wearer two discrete focusing zones. They remain a meaningful part of the lens market because they're less expensive than progressives, involve essentially no adaptation period since the two zones are clearly separated, and some long-time bifocal wearers actually prefer the defined line over a progressive's blended transition. The trade-off is the visible line itself (a cosmetic concern for some) and the lack of any correction for the middle-distance range — arm's length, a computer screen — that falls between the two zones.
Progressive lenses blend distance, intermediate, and near corrections into one continuous lens with no visible dividing line, giving the wearer a full range of focus by simply shifting where they look through the lens. They're the closest a corrective lens gets to natural, pre-presbyopia vision, and have become the default recommendation for most new presbyopic wearers. The trade-off is price — progressives cost meaningfully more than bifocals due to the more complex lens design and manufacturing — and a genuine adaptation period, typically one to two weeks, during which new wearers need to learn where to look through the lens for each distance.
A full-service optical range needs all three: single vision as the volume category, bifocal as the value multifocal option, and progressive as the premium multifocal recommendation for anyone spending significant time at a computer or wanting the line-free cosmetic result. Retailers who only offer progressives lose price-sensitive multifocal customers to competitors stocking bifocals; retailers who skip progressives lose the growing share of presbyopic customers who specifically want the no-line look.
Browse Salvador Eyewear's Single Vision, Bi-Focal, and Progressive lens ranges.