Glass vs. Plastic

The glass eye

Advantages

• natural inorganic material, cryolite glass (Na6 Al2 F12)
• fire baked surface on front and back side, good wettability with tear film and resistant to liquids
• Colour stable, no fading of the colours
• very light prostheses due to thin walls, an important feature especially with large prostheses due to better wearing comfort (hollow body, not solid)
• the gloss is very close to the natural eye due to the good light reflection
• the preparation takes place in the presence of the patient and, after cooling, the glass eye can be worn immediately (total duration approx. 1-2 hours)
• since only few tools and equipment are necessary, ocularists can be active with their speiialist art in many places, short distances for patients

Disadvantages

• fragile when handled carelessly
• can only be corrected or reworked to a limited extent after completion
• repair of damaged glass prostheses is not possible
• at very cold outside temperatures there can, depending on the sensitivity and condition of the orbit, be a cold sensation

Das Kunststoffauge

Advantages

• unbreakable (except under extreme loads, as PMMA is made of PolyMethylMethAcrylate)
• no feeling of cold in cold outside temperatures
• can be further altered after production
• wearable for up to 5 years with annual polishing

Disadvantages

• less wettability with tear film due to slightly duller surface
• significantly longer production time, (2 days, several visits necessary)
• Reactions with the conjunctiva may occur
• The matte surface has little light reflection even after polishing (mechanically)
• Colour may change over time (fading of the plastic)
• Often heavier than glass prostheses because of thicker or completely solid construction
• A lot of tools and equipment necessary, therefore usually can only be manufactured at a fixed location, often resulting in long distances for patients
• Prostheses made of plastic require an approval procedure with the cost bearers