The selection of right type of lenses is a measure of your level of satisfaction. The lenses contribute greatly to your vision, appearance, comfort and safety.
 

Primarily there are two lens materials: Glass and Plastic

Earlier, all spectacle lenses were made of glass. However, with the advent of superior quality of Plastic or Resin Lenses, the glass lenses have been gradually replaced.

 

 Although glass lenses posses exceptional optical and surface properties, they are heavy and can break easily, posing potential harm to the eye. Because of its light weight (about half the weight of glass), and excellent optical qualities, CR-39 Plastic & Resin are the most popular spectacle lens material today. Given below is suggested sequence to select proper type of lenses:

 

Step-1: Understanding your Lens Prescription Format: Your lens prescription has a specific format, and the most commonly used one is given below:

 

 

R

L

 

Sph

Cyl.

Axis

V/A.

Sph

Cyl.

Axis

V/A.

Distance

 

 

 

 

 

 

 

 

Near

 

 

 

 

 

 

 

 

R is an abbreviation for Right eye and L for Left Eye. Sometimes the Latin abbreviations are used, wherein OD for the right eye and OS for the left eye


Sph. The number written under Sph column is a measure of  long-sightedness or short-sightedness. This could be any number plus or minus or even zero (also called Plano). The numbers go in 0.25 D steps.

Cyl. The number under the Cyl column is a measure of astigmatism. This could be any number plus or minus or even zero. The numbers go in 0.25 steps. If there is no astigmatism then this column will be left blank.

Axis: The  number under the axis column relates to the angle of the astigmatism. This will be a number between 5 and 180. The steps are in 5’s.

V/A: The number under the V/A column refers to Visual Acuity - an indication of the clarity or clearness of vision

 

Step -2. Have a look at your prescription. It may either be for Single Vision Lenses or for Bifocal/ Multifocal or Progressive Lenses.

2.1 If it is a prescription for a person, less than 40 years of age, needing only single vision lenses, the prescription would appear as under:

 

RE

LE

 

Sph

Cyl.

Axis

V/A.

Sph

Cyl.

Axis

V/A.

Distance

+ 1.00

+0.50

180

6/6

+1.00

-0.50

90

6/6P

Near

 

 

 

 

 

 

2.2 However, in case of persons over the age of 40 years, needing additional power for reading, the prescription would appear as under:

 

RE

LE

 

Sph

Cyl.

Axis

V/A.

Sph

Cyl.

Axis

V/A.

Distance

+ 1.00

+0.50

180

6/6

+1.00

-0.50

90

6/6P

Near

+ 3.00

+0.50

180

6/6

+3.00

-0.50

90

 


or it may be written like this:

 

RE

LE

 

Sph

Cyl.

Axis

V/A.

Sph

Cyl.

Axis

V/A.

Distance

+ 1.00

+0.50

180

6/6

+1.00

-0.50

90

6/6P

Near

 

 

Add + 2.00

 

 

 

 

Step – 3: Choose the Type of Lenses: A large variety of Lenses are available both in case of Single Vision or Bifocal / Multifocal Lenses, making decision a bit difficult.

3.1 Common Varieties covered under SV Lenses are:

A. Basic Lenses without any surface coating

 

B. Hard Coated Lenses with Scratch Resistant surface coating

 

C. ARC Lenses with Anti reflection coating to eliminate reflection off the lens surface. With improved transmission, these lenses are very helpful in night driving and also ease eyestrain from working on computers or digital devices. Eyes are clearly visible in photographs.

 

D. Photochromic Lenses: These lenses  darken in the sun's UV rays, and  quickly return to clear (or nearly clear) when indoors.  These are recommended where a person has to frequently go outdoors.

 

E. Polycarbonate Lenses are much more impact resistant and lighter in weight  than other plastic materials. These are recommended for  children's eyewear, safety glasses, sports eyewear and rimless frames

 

F. Higher Index 1.67 & 1.74 For Lens Power exceeding 4 Diopters, higher index plastic of 1.67 and 1.74 index are recommended.  They make the lenses appear 30 to 40% thinner compared to 1.498 Index Basic lenses.

G. Branded Lenses. A large number of Branded spectacle lenses are available, covering the above features. Seiko and Crizal brands remain a preferred choice of customers on account of rigid quality control.