Contact lenses in Ophthalmology

A DETAILED PRESENTATION COVERING ALL ASPECTS OF CONTACT LENSES.TYPES, USES , MAKE, CARE AND MATERIAL.

1. CONTACT LENS : OVERVIEW Dr. ARVIND KUMAR MORYA MBBS,MS OPHTHALMOLOGY (GOLD MEDALIST),MNAMS,CATARACT(MICS),GLAUCOMA,PAEDIATRIC OPHTHALMOLOGY,STRABISMUS,REFRACTIVE AND MEDICAL RETINA SERVICES . ASSOCIATE PROFESSOR AND UNIT HEAD DEPARTMENT OF OPHTHALMOLOGY AIIMS JODHPUR

2. DEFINITION Artificial visual device Correct refractive error by substitute anterior surface of cornea .

3. HISTORY OF CONTACT LENS 1508, L eonardo D a Vinci used bowl half filled with water. 1637, Descartes used tube filled with water. 1887, Muller used glass shell.

4. 1888 , F ick formulated term C.L. Initially 2 types were available- - Blown glass lens from Muller - G round glass lens from Zeiss 1937, Feinbloom 1 st used plastic polymer for manufacture. HISTORY OF CONTACT LENS

5. IDEAL MATERIAL BIOCOMPATIBILITY Should not harmful. OPTICAL PROPERTY T ransparency R efractive index

6. PHYSICAL PRORERTIES Wettability Porosity & permeability High water content Heat resistance Specific gravity Scratch resistance IDEAL MATERIAL

7. OXYGEN TRANSMISSIBILITY DK/K D= Diffusion coefficient (cm/sec) K=solubility of gas in material(cm3/cm2mmhg) L= thickness of material(mm) Depends on: permeability of lens material Thickness of lens Temperature at which test is performed

8. OXYGEN PERMEABILITY Low Dk material -Below 20 Mid Dk material -20 to 40 High Dk material -40 to 60 Hyper Dk material -Above 60

9. OXYGEN PERMEABILITY Daily wear , the recommended Dk /t of a contact lens is around 30 Low oxygen transmissibility can result in corneal changes: - Microcysts - Polymegathism - Corneal Ph - Edema - Blebs

10. WETTABILITY The angle that the edge of a bead of water makes with the surface of a contact lens called a wetting angle. The smaller the wetting angle the greater the wettability of lens.

11. Meets corneal ’s oxygen requirements Physiologically inert Biocompatibility Excellent in vivo wetting Resists spoliation IDEAL CONTACT LENS MATERIAL

12. Dimensionally s table Durable Optically transparent Requires minimal patient care Cost effective Easily moldable IDEAL CONTACT LENS MATERIAL

13. CONTACT LENS DESIGN Monocurve / single-cut lens Bicurve Tricurve Multicurve Toric lens- has toric back surface Bitoric lens - Prism blast lenses Truncated lenses Lenticular lenses Bifocal lenses

14. INDICATIONS Patient best suited to Contact Lens is one who wants TO SEE BETTER and BE SEEN BETTER without glasses.

15. OPTICAL INDICATIONS Myopia / Hypermetropia / Astigmatism Presbyopia Aphakia Anisometropia & Anisoconia Keratoconus

16. COSMETIC INDICATON Aniridia Albinism Coloboma / L arge iredectomy Heterochromia Microcornea / M icrophthalmos Corneal scars Inoperable cataract

17. OCCUPATIONAL INDICATION Actors / public speakers People using telescope / microscope Sportsman Protection from steam, spray , mist etc.

18. THERAPEUTIC [ BANDAGE SOFT C.L.] Decreases pain Prevent mechanical trauma by touch Increases proper hydration and proper healing Corneal edema Corneal perforation Corneal burns Corneal grafts

19. Bullous keratopathy Leaking conjunctival blebs Keratitis Symblepharon Lagophthalmos Chronic and indolent ulcer THERAPEUTIC [ BANDAGE SOFT C.L.]

20. THERAPEUTIC [ BANDAGE SOFT C.L.] Trichiasis / entropion Post pterygium operation Dry eye syndrome For drug delivery(glaucoma) Melenosis of conjunctiva – use to deliver high dose continuous to conjunctiva

21. ORTHOKERATOLOGY (obsolete concept) Believe to mould cornea & control high myopia / astigmatism RGP with progressive flat fitting DIAGNOSTIC USE Fundoscopy Gonioscopy Applanation tonometry A-scan biometry

22. RESEARCH Corneal temp. measurement

23. CONTRAINDICATIONS OCULAR PATHOLOGIES Blepharitis Chalazion / stye Conjunctivitis Large pterygium / pinguecula Chronic hyperemia

24. OCULAR PATHOLOGIES Pannus Corneal anesthesia Tear film abnormalities Epithelial dystrophies Scleritis, Episcleratis I ritis CONTRAINDICATIONS

25. C ONTRAINDICATION S SYSTEMIC DISORDERS Diabetes Oral contraceptive use Pregnancy Perimenopausal ALLERGIES Contact dermatitis Asthma Atrophic rhinitis

26. OCCUPATIONAL HAZZARD Smoky, dusty hot environment Chemical fumes & irritants High altitude flyers Construction worker / automobile mechanics. C ONTRAINDICATION S

27. C ONTRAINDICATION S OTHER Poor general health Clumsy patient Low hygienic standards Old patient with low motivation Arthritis

28. ADVANTAGE No peripheral aberration No chromatic aberration Prism distortion can be controlled Less minification / magnification Astigmatism can controlled No fogging Increases field of vision Cosmetically more pleasant

29. DISADVANTAGE Problem for old / very young patient Require a lot care Supervision required Rides low Costly

30. CLASSIFICATION ANATOMICAL POSITION Scleral contact lens Semi-scleral contact lens Corneal contact lens NATURE OF LENS MATERIAL Rigid non-gas permeable/hard C.L. (PMMA) Rigid gas permeable/semi-soft C.L. (CAB) Soft C.L. (HEMA)

31. MODE OF WEAR Daily wear Extended wear Disposable PURPOSE OF USE Optical Therapeutic C osmetic CLASSIFICATION

32. HARD CONTACT LENS (RIGID NON-GAS PERMEABLE LENS) Made of PMMA. Confirm to the cornea . ADVANTAGE Light in weigh High optical quality Non toxic Easy to manufacture

33. HARD CONTACT LENS (RIGID NON-GAS PERMEABLE LENS) DISADVANTAGE Low wettability Low O2 permeability (DK value = 0) Hard Now obsolete

34. RIGID GAS PERMIABLE LENS (RGP) / SEMI SOFT LENS Initially made of Cellulose A cetate B utyrate. Silicon Acrylate Copolymer of PMMA & Silicon containing vinyl monomer Styrene Fluropolymers -for extended wear. Size- usually 9-10mm. Best in high myopes , astigmatism >2d, keratoconus.

35. SOFT CONTACT LENS HIGH WATER CONTENT LOW WATER CONTENT Up to 85 % of H2O Made of hydrogel HEMA HEMA-VP LENSES MMA-PVD LENSES Glycidyl methacrylate 38 – 45 % of H2O Made of silicone hydrogel .

36. LOW WATER CONTENT HIGH WATER CONTENT Advantage Less susceptible to environment changes Low protein deposition Ease of manufacture More wettable Compatible with all lens care product Disadvantage Low DK Less flexible Thin lens difficult to handle Advantage Higher DK More flexible Faster restoration of shape following deformation. Disadvantage More fragile More deposit prone Difficult to manufacture Lower tensile strength Cannot be made too thin SOFT CONTACT LENS

37. ADVANTAGES OF RIGID CONTACT LENS Better quality of vision More durable Correction of astigmatism Deposit resistance Less of chance of infection Cost of lens Less comfortable, tough adaptation

38. ADVANTAGE OF SOFT CONTACT LENS Very comfortable and easy to adapt Larger & adhere more tightly to the cornea No spectacle blur Doesn’t correct astigmatism

39. HYBRID RGPs Central optical zone, formed by Rigid GP ,surrounded by peripheral soft contact lens material. Second generation silicone hydrogel CL, called Duette , having highly oxygen-permeable GP centre , surrounded by a soft silicone hydrogel “skirt” for comfort.

40. WEAR AND REPLACEMENT SCHEDULE DW-daily wear: Traditional replacement cycle> 3 months Monthly replacement Daily replacement EW-extended wear: Allowing lenses to be worn for 7 days/6 nights without removal. D uring one night per week the eyes are free of lenses. W eekly replaced by new lenses

41. WEAR AND REPLACEMENT SCHEDULE FW-Flexible wear: Compromise between DW & EW. Depending upon the demand of the patient to once a while sleep in lenses

42. TERMINOLOGY USED FOR C.L. TERM SYMBOL ALTERNATE TERM / ALTERNATE NAME BOZR (Back optical zone radius) ro BC-Base curve BCOR-back central optical radius PCCR-posterior central curve radius BOZD (Back optical zone diameter ) Ɵ 0 BCOZ-back central optic diameter POZD-posterior optical zone diameter OZ-optic zone BPR (Back peripheral radius) r1 , r2 BPOR- back peripheral optic radius PCR-peripheral curve radius BPZD (Back peripheral zone diameter) Ɵ1 , Ɵ2 BPOD-back peripheral optic radius PCD-peripheral curve radius TD (Total diameter) ƟT OS-overall size OD-overall diameter

43. CONTACT LENS FITTING PRE-FIT CONSULTATION Complete history Detailed eye examination KERATOMETRIC METHOD Pupil diameter [with IPD scale] is measured. HVID is measured. Corneal diameter is measured. Radius of curvature is measured with a keratometer.

44. KERATOMETRIC METHOD BASE CURVE, back surface of lens. Rest on cornea responsible for good fit. Long radius of curvature – flatter base curve. TD depends upon lid diameter & corneal diameter OR HVID. Optical zone should be at least 7 mm. Posterior surface – Aspheric. Anterior surface –convex with power . CONTACT LENS FITTING

45. TRIAL LENS METHOD Various lens from trial set tried until appropriate B.C. achieved. Very tedious and cumbersome A large trial set has to be maintained INVENTORY FITTING METHOD Combination of both above More time efficient and more convenient to patient. CONTACT LENS FITTING

46. FACTORS TO BE KEEP IN MIND The total diameter should 1-1.5 mm greater than HVID. BC should be 0.3-0.6 mm flatter than the flattest k reading. DETERMINATION OF LENS POWER Spherical power + ½ cylindrical power [ if cyl is b/w 0.5D to 2.00D ] If cyl is < 0.5D Drop cylinder. If cyl is > 2.00D , go for toric CL.

47. Lens coverage-uniform Movement <0.5 mm Fluctuating vision clears on blinking Progressive discomfort on wearing Circumciliary congestion Edge indentation of limbus Retinoscopic image is fuzzy To correct this- Increase B.C. by 0.2-0.3 mm Decrease T.D. by 0.5 mm SIGN OF TIGHT FIT

48. SIGN OF LOOSE FIT Poor centration Movement >1 mm Variable vision blurs on blinking Edges stand off , ejection of lens Retinoscopic image blur on blinking To correct this- Increase T.D. by 0.5-1 mm Decrease B.C. by 0.2-0.3 mm

49. After fitting ½ hour to 1 hour should be given for subside reflex lacrimation. TOTAL PUPILLARY CAPTURE should be. Movement of lens- opposite the movement of eye On blinking lens should move upward . CONTACT LENS FITTING

50. Schematic flow chart of soft contact lens fitting procedure 2. Slit lamp examination -Corneal coverage -Edge alignment -Primary gaze movement -Centration -Push-up test 1. Insert trial lens symptom -comfort -visual Assessment of initial fit -vision assessment -visual acuity -over refraction Sub-optimal result

51. SPECIAL CONTACT LENS COSMETIC CONTACT LENS 1. TINTED LENS- Can be opaque OR transparent Used for cosmetic purpose 2. PAINTED LENS- Painted with pigment to stimulate iris Useful in occlusion therapy, disfigured cornea, vision-disturbing conditions such as albinism, aniridia , iris coloboma .

52. TYPES OF COSMETIC LENSES A. Iris painted with clear pupil [ Albinotic lens] B. Black pupil and iris painted C. Pupil painted DISADVANTAGE- Toxic effect Corneal edema

53. CONTACT LENS FOR COLOUR BLINDNESS Using customize filters to change the wavelength of each color. Example- X-Chrome lens Golden yellow lens

54. G OO GLE CONTACT LENS G oogle C ontact L ens is a smart contact lens project announced by google on 16 J anuary 2014. The project aims to assist people with diabetes by constantly measuring the glucose levels in their tears.

55. G OO GLE CONTACT LENS CONTENT THE LENS CONTAINS : Soft contact lens : Encapsulates electronic signals Sensors : Detects glucose in tears Chip & Antenna : Receives power and sends information

56. MISCELLANEOUS KERATOPHAKIA- - High power lens implanted inside corneal stroma . EPIKERATOPHAKIA- - High power lens implanted in corneal epithelium. KERATOMILEUSIS- - Corneal sculpting to correct refractive error.

57. HYPER OSMOTIC CONTACT LENS A NEW TREATMENT MODALITY FOR CORNEAL EDEMA

58. CORNEAL EDEMA Incidence: 2,000,000 new patients annually . Causes Cataract surgery, Trauma, Infection, or secondary to a genetic defect in the corneal endothelium. To date, there is no effective treatment for corneal edema besides transplant from a human donor. HYPER OSMOTIC CONTACT LENS

59. Optical performance is diminished because : Shape and size of epithelial cells change to close the gap created by the destroyed cells. The light-bending properties of the endothelial cells changed. The excess fluid in stroma scatters incoming light  R educes the ability of the cornea to focus the light properly. HYPER OSMOTIC CONTACT LENS

60. HYPER CL It is a hyperosmotic contact lens act as a therapeutic soft contact lens with unique capability of increasing eye drops contact time Improve vision and facilitate corneal healing And also proven to relieve corneal edema .

61. It enables extraction of fluid from the corneal stroma, combined with increased evaporation over the lens surface. It is disposable and reusable up to two weeks. HYPER CL

62. The dual base curve combined with the groove and the holes inside the lens creates a micro-environment above the center of cornea that holds fluid with high ionic concentration and thereby absorbs fluids from the cornea. HYPER CL

63. HYPER CL DESIGN The Hyper-CL™ design includes the following characteristics : 1) Two different base curves , which create a tear reservoir. 2) A peripheral groove including 4-16 fenestrations , which increase tear exchange and accessibility.

64. The application of hyper osmotic drops result in extraction of fluids from the cornea, reducing corneal edema OPERATION PRINCIPLE

65. INDICATION FOR USE Therapeutic use in Acute or chronic ocular pathologies such as corneal erosions,entropion,corneal edema & corneal dystrophies . In post-surgical conditions resulting from cataract extraction and corneal surgery . It can provide optical correction during the healing process if required.

66. CONTRAINDICATIONS Any eye disease , injury, or abnormality that affects the cornea, conjunctiva, or eyelids, Dry eye disease . Any systemic disease (exaggerated by wearing contact lenses). Patients unable to follow lens care regimen or unable to obtain assistance to do so. Allergic to lens material

67. HYPER CL TREATMENT MODALITIES To treat corneal edema awaiting corneal transplantation or patients unsuitable for corneal transplantation. As Drug delivery contact lens Miniscleral lens for ocular surface problems.

68. Acknowledgements Dr. Anju Singh, Senior Resident, Department Of Ophthalmology, AIIMS Jodhpur Mr. Raghuveer Singh Udawat , Senior Optometrist, Department Of Ophthalmology, AIIMS Jodhpur Mr. Sampat Choudhary , Optometrist, Department Of Ophthalmology, AIIMS Jodhpur