Hydrogel Lens Materials Done By : Fazeela , Rose , Xue Ya , Shanise

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Hydrogel Lens Materials Done By : Fazeela , Rose , Xue Ya , Shanise by Mind Map: Hydrogel Lens Materials Done By : Fazeela , Rose , Xue Ya , Shanise

1. More Info on pHEMA

1.1. 1962

1.1.1. Sold in Europe Disappointing sales

1.2. 1965

1.2.1. licence for American rights to technology bought over from Czechs

1.3. 1971: Bausch & Lomb

1.3.1. Refined spin-casting techniques

1.3.2. Obtained FDA approval

1.3.3. Became widely popular!!! PROBLEMS Hypoxia Solution toxicity Lens spoilage

2. Conventional Hydrogel Materials

2.1. Low Water Content

2.1.1. Advantage Higher Refractive Index More Rigid , Easier To Handle More Wettable

2.1.2. Disadvantage Low DK More Rigid , Less Comfortable Thin Lens , Difficult To Handle

3. Silicone Hydrogel

3.1. High Water Content

3.1.1. Advantage High DK More Flexible Returns Back To Original Shape After Deformation

3.1.2. Disadvantage Tear Easily Lower Refractive Index More Deposit Prone

4. Soft Lens Material Classification

4.1. USAN Identity

4.1.1. each chemical entity given a name

4.2. FDA Classification Scheme (water content and ionic content) - Group I, II, III, IV

4.2.1. Group I, II, III, IV

4.2.2. Low water content materials (group i, iii) ADVANTAGES more rigid, easier to handle any manufacturing method can be used DISADVANTAGES less flexibility (more rigid, less comfortable) thin lens, difficult to handle restore shape fast after deformation

4.2.3. High water content materials (ii, iv) ADVANTAGES more flexible DISADVANTAGES tears easily higher dehydration rate on the eyes thicker lens, due to high water

4.2.4. Non- ionic materials (i, ii) (<0.2% ionic material) ADVANTAGES less deposit prone do not bind charge particles DISADVANTAGES denature tear proteins more less wettable ( no - charge on lens surface)

4.2.5. Ionic materials (iii, iv) (>0.2% ionic material) ADVANTAGES more wettable ( - charge on lens surface) denature tear protein less DISADVANTAGES temperature sensitive deposits more readily more susceptible to pH changes deposits may be bound

5. How is it formed?

5.1. HEMA

5.1.1. Hydroxyl group

5.1.2. PMMA

5.2. pHEMA

5.2.1. polymerising 2 or more HEMA monomers