**1.2 Refractive index**

Refractive index of a material refers to ratio of velocity of light in vacuum to velocity of light in that medium. It is a measure of bending of light rays when they travel through a particular medium. The refractive index and thickness of the IOL are inversely proportional.

#### **1.3 Size**

The optic diameter and the length of the haptics are taken into consideration when the size of the IOL is to be measured. The size of the incision, the type of injector and methods of introducing the IOL are all based on the size of the IOL.

#### **1.4 Adhesiveness**

Adhesiveness is a property by which the IOL fuses with anterior and posterior capsule and hence reduces the risk of decentration. This property becomes essential in toric IOLs.

#### **1.5 Glistening phenomenon**

Penetration by aqueous humor has been noted to cause small vacuoles within the lens optic. This phenomenon is called 'glistening phenomenon'.

**5**

**Figure 2.**

*to glass.*

*Basic Science of Intraocular Lens Materials DOI: http://dx.doi.org/10.5772/intechopen.92573*

into consideration in designing an intraocular lens.

Based on the materials, intraocular lenses can be classified as:

One of the first materials to be used for the purpose of intraocular lenses, polymethyl methacrylate (PMMA) is a rigid, non-foldable, hydrophobic material (**Figure 2**). Hydrophobic nature of PMMA lenses makes them more likely to adhere to corneal endothelial cells during insertion, thus causing potential endothelial loss. The refractive index is 1.49 and the usual optic diameter is 5–7 mm. They are usually

Due to their property of rigidity, a large incision is required for its implantation. An incision size of about 5.5–6 mm or a large corneoscleral tunnel is required for its

*(a) MMA (methyl methacrylate) forms the basis for acrylic IOLs. (b) Poly(methyl methacrylate) (PMMA) is a transparent thermoplastic; it was initially developed as a lightweight and shatter-resistant alternative* 

The properties of the IOL such as affinity for water, adhesiveness and presence of square edge contribute in prevention of opacification of posterior capsule after

The structure and design of IOL contributes to its ability to remain centered in the capsular bag. The shape and length of haptics and the optical diameter are taken

**1.6 Prevention of PCO**

cataract surgery.

**1.7 IOL design**

**2. Classification**

1.Rigid (PMMA)

2.Flexible (Silicone)

3.Foldable (Acrylic)

single piece and have low memory haptics.

4.Collamer

**2.1 PMMA**
