1. FAULT MADE BY : SWATI PANARA FROM : BHARTIMAIYA COLLEGE OF OPTOMETRY 2nd YEAR 3rd SEMESTER

2. OPHTHALMIC LENS It is the portion of the transparent medium bounded by two refracting surfaces of at least one of which is curved. 3. FAULT Fault is a defect before manufacture or after manufacture. 4. MANUFACTURING OF AN OPTICAL GLASS BATCH PROCESS CONTINOUS FLOW PROCESS 5. DEFECT Defect in the material of the lens Defect on the surface of the lens 6. DEFECT IN THE MATERIAL OF THE LENS By looking directly through the lens transmission (T) By using the technique shadowing (S) Viewing the light reflected from the lens surfaces reflection (R) 7. TRANSMISSION SHADOWING REFLECTION 8. TRANSMISSION BAD METAL BUBBLE FEATHERS 9. TRANSMISSION 10. BAD METAL Also known as bad stock or stones. The material must be free from any inclusions or foreign particles that may appear in generally due to portion of the batch material remaining undissolved during the melt. 11. BUBBLE Formed by the large volume of gas given off during the melting period. size 1 mm diameter seeds. They are as small as droplets in the glass. They are escaped and their escape is promoted in the process of rapid stirring. 12. BUBBLE 13. FEATHERS A cluster of bubbles or seeds often around bad metal takes on the appearance of a small white feather in the glass. 14. SHADOWING COLOUR STRAIN VEIN 15. VEIN Fine thread or streak of glass of slightly different refractive index to the surrounding glass caused usually by stirring. like a thin empty tube running through the glass. There are caused by the insufficient mixing of bad metal 16. TYPES CORD STRIA 17. Two types: a) Cord (S) Heavy or pronounced veins. b) Stria (S) A very fine vein 18. COLOUR The medium from which a spectacle lens is made have a high degree of clearness & transparency The defect Color is defined as any unintended coloration in a medium which is supposed to be white generally arises from the use of impure materials in the composition of the medium 19. Any stress of iron oxide in silica, the manufacturing glass causes unwanted Green tinting. Certain high index material ingredients will show slight yellowishness. Best detected on a matt white paper. 20. STRAIN If molten glasses allowed to cool too rapidly the outer surfaces solidify before the hotter inner portion. As the inner portion then cools, it tends to shrink setting up tension within the glass. The resulting stress is called strain. May also arise if external forces are allowed to compressed the glass. 21. Glass may be inspected by means of polariscope. The similar type of strain is seen if a tight glazed glass is fitted in Frame. 22. DEFECT ON YHE SURFACE OF THE LENS Defects caused by chemical or thermal action During the production Maltreatment of the finished surface 23. DURING THE PRODUCTION HOLE GREYNESS POLISHING BURN WAVE ORANGR PEEL DEFECT GENERATOR MARK RING ROUNDING CLOTHMARK DRAG MARK PAD MARK 24. HOLE (R) It is also called as PIT. A pit in the lens surface which may be caused by breaking into a bubble, or more frequently by insufficient smoothing. It can lead to drag marks. It can be caused by breaking into covers. 25. HOLE 26. GREYNESS (R) The appearance of a surface after incomplete polishing. The surface still appear smooth. Polishing process should be continued until all signs of greyness disappear. It appears to be grey 27. POLISHING BURN (T) Heat is generated during the polishing pad. It is very common defect. Appearance of transparent blister or group of blister on surface. During polishing if the lens surface is allowed to get too hot, then by lack of lubrication between the polishing pad and lens, the polishing burn of glisters can occur. 28. WAVE (T) (S) A wave is a surface undulation or ripple, the surface changing curvature in the region of the wave. It indicates not only the nature of the surfaces, but also the method by which they were produced. Can be attributed to faulty machine motion or by polishing on a badly smoothed surface or even over polishing. 29. ORANGE PEEL DEFECT (S) A form of waviness' named after its appearance usually extending over the entire surface of the lens. A defect that is closely related to a wave is called as orange peel defect. Some say that this type of surface is a water polish. The defect is really a type of wave and looks like the peel of a orange. 30. GENERATOR MARK The most common type of unwanted patterned surface marks are generator marks. Generator marks are parallel , curved marks across the surface of the lens. 31. They are caused by the generator wheel. Light generator marks are normal after generating. 32. After fining and polishing, they should not be visible. If generator marks do not disappear after fining and polishing it is usually because of one of the three problems: 33. 1. A lap tool that does not match the curve of the lens. 2. A generator that is cutting off curve 3. Incomplete fining 34. RING (T) (S) concentric waves produced on a spherical surface. 35. RING 36. CLOTH MARK the weave of the polishing pad on the lens surface. Found on badly polished toroidal surfaces, the surface appearing to have a diamond shaped pattern following the base curve meridian. 37. ROUNDING (S) A defect of figure at the edge of a lens generally caused by excessive pressure from a soft polishing pad towards the edge of the lens. 38. DRAG MARK (S) A local wave usually associated with an edge chip, the drag mark extending from the chip & following the machine motion. 39. PAD MARK Can be experienced the form of the wave duplicating the surface of the pad. 40. DEFECT CAUSED BY CHEMICAL OR THERMAL ACTION CRASING TARNISH 41. CRAZING (R) presenting the appearance of criss-cross cracks in the surface. Usually caused in GLASS by sudden chilling but in PLASTIC lenses it results either from stress or solvent action. 42. Criss cross cracks- surface 43. TARNISH (R) Chemical chances at the surface of the lens, brought about by extreme atmospheric conditions Flint glasses are particularly prone to this defects Chemical changes at the surface. 44. Lead in the material gets oxidized and lead oxide is formed thus giving yellowish colour High index lenses are particularly prone to tarnish 45. MALTREATMENT OF THE FINISHED SURFACE SCRATCH DIG SLEEK BRUISE CHECK CHIP 46. SCRATCH It may be found at any stage in the grinding process. Elongated penetration on the surface with jugged edge. 47. SCRATCH 48. CAUSED BY Penetration of surfaces characterized by sharp edges Incorrect handling Contamination of polishing liquid Splintering of material. 49. DIG (R) A short scratch usually caused by striking the lens with a sharp object or as a result of dropping the lens. 50. SLEEK (R) an elongated penetration of the surface without producing jagged edges. It may occur if a lens is cleaned with a rough or dirty cloth. 51. CHIP (R) it occur at the edge of A Lens produced either by impact on the edge or by tension being applied by a spectacle frame. 52. BRUISE CHECK (R) it is a surface crack or fracture due to impact on the surface of the glass. Crescent shape incomplete. 53. ABUSE MARK Term applied to cover surface defect caused by bad handle. 54. NO TRANSMISSION [T] SHADOWING [S] REFLECTION [R] 1. BAD METAL VEINS TARNISH 2. BUBBLES CORD CRAZING 3. FEATHERS STRIA HOLE 4. POLISHING BURN CLOTH MARKS GREYNESS 5. WAVES WAVES SCRATCH 6. RINGS RINGS DIG 7. DRAG MARKS SLEEK 8. ORANGE PEAL BRUISE CHECK 9. ROUNDING CHIPS 10. ABUSE MARKS 55. THANK YOU