소프트 콘택트렌즈 착용에 관한 부작용

1. 소프트 콘택트렌즈 착용에 관한 부작용 Peter B. Lee, OD 121st General Hospital Seoul, Korea

2. CL 부작용의 위험 요소 • Hypoxia (저산소증) • virtually all CLs reduce O2 supply to cornea • Desiccation / Alteration of tear film(렌즈탈수/각막건조) • CLs are much thicker than tear film • SCLs evaporate to the atmosphere • Deposit build-up(침전) • SCL>RGP, but all develop deposits made of proteins, mucous, lipids, dirt, and microbes

3. CL 부작용의 위험 요소 • Mechanical(물리적 요소) • Tightness & looseness • Abrasions & friction • Inflammatory response(염증) • Proteins and other surface deposits • Microbes and their toxins • Solution preservatives and other components

4. Contributory Factors(문제가 될 수 있는 요소) • Lens material • Dk(산소 침투성) • Wettability and deposit attraction • Stiffness and other physical characteristics • Lens design and fitting • Lens-to-cornea relationship • Position and movement • Thickness profile

5. Wearing time(착용 시간) DW vs. EW Daily vs. part-time Patient’s physiology Patient compliance(착용자의 순응도) Wear time Cleaning and disinfection Lens replacements Follow-up visits

6. Effects of Hypoxia (저산소증에 인한 문제점)

7. Effects of Hypoxia • Epithelial and stromal edema(각막부종) • Decrease in epithelial mitosis(상피 분열) • Increase in stromal lactate accumulation(유산 축적 in anterior chamber) • Decrease in corneal sensitivity

8. Corneal Edema(각막부종) • The cornea requires a certain amount of oxygen to prevent swelling, or edema • During sleep, the oxygen supply is reduced to approx. 8%, compared to about 21% during waking hours • The cornea swells 3% to 4% overnight • Therefore, it appears the cornea needs more than 8% O2 to prevent swelling

9. Corneal sensitivity(각막 민감도) • Millodot and O'Leary (1980) found that the cornea needs at least 8% oxygen to prevent a reduction in corneal sensitivity

10. Oxygen Requirements • The cornea requires 8% to 13% O2 to maintain normal corneal thickness, metabolism, and sensitivity. • What are today’s contact lenses able to deliver?

11. Oxygen Requirements • CLs are not rated by % O2 delivered • Transmissibility (Dk/L) is a rough indicator of how well a CL transmits oxygen • Dk/L is the most common measure to rate how well contact lenses deliver oxygen to the cornea • Other methods have also been developed but are not in widespread use

12. Epithelial Edema(각막 부종)

13. Epithelial Edema(각막 부종) • Epithelial edema manifests as clouding of the epithelial tissue, usually centrally, with associated punctate epithelial staining, steepening of the corneal curvature and possible irregularity of the corneal surface

14. 원인 • Low Dk(산소 침투성) contact lens wear (PMMA more likely than soft lenses) • Long-term, extended hours or extended wear(연속 착용)

15. 증상과 진단 • Poor endpoint visual acuity • Distorted keratometry mires, steepening of K's • Central circular clouding (CCC) • Punctate epithelial staining centrally • Increased minus on refraction

16. 치료/처치법 • Discontinue lens wear or immediate refit to higher Dk material • Refit to higher Dk material • Decrease wear time • Looser fit for better tear exchange • Monitor K and SR changes • Prescribe new spectacles when stable to allow decreased CL wear time

17. Stromal Edema(고유층 부종) • Stromal edema manifests as fine wrinkling (striae) or folds in Descemet's membrane • Striae and folds appear with approx. 6% stromal edema • Stromal clouding requires extensive edema, at least 15%, and is usually not induced by contact lens wear

18. Stromal Edema

19. 원인 • Thick lens design (aphakic, prism ballast), low Dk material or EW

20. 증상과 진단 • Mild edema: 6 to 7% • Striae in deep stroma • Moderate edema: 10 to 15% • Folds in deep stroma • Severe edema: > 18% • Central haze on sclerotic scatter

21. 치료/처치법 • Increase Dk/L: higher water content, thinner design • Looser fit for better tear exchange

22. Microcysts(상피 미세낭종) / Vacuoles(엑포)

23. Microcysts(상피 미세낭종) / Vacuoles(엑포) • Microcysts are tiny cystic bodies containing cellular debris • They form at the basal cells and slowly migrate towards the corneal surface • They are visible with reversed illumination, indicating that the cystic material has a higher index of refraction than the surrounding corneal tissue

24. Microcysts / Vacuoles

25. Microcysts / Vacuoles • Vacuoles form similarly to microcysts but are fluid filled • They are visible with unreversed illumination, indicating that the cystic material has a lower index of refraction than the surrounding corneal tissue

26. Microcysts / Vacuoles • Although they do not induce any symptomalogy, the presence of microcysts and vacuoles indicate a chronic hypoxic condition and a resulting alteration of corneal metabolism • Removal of the offending contact lens will result in their disappearance over the course of several weeks

27. 원인 • Several weeks (6 to 12 or more) of low Dk/L lens wear • Extended Wear

28. 증상 및 진단 • Small cysts in epithelium visible with retroillumination • Microcysts: reversed illumination (higher index than cornea) • Vacuoles: unreversed illumination (lower index than cornea)

30. 치료/처치법 • Increase Dk/L • D/C extended wear • D/C lens wear if more than 50 are observed • Monitor for 3 to 6 months for resolution • # may increase after d/c lens wear due to abnormal processing of epithelial cells

31. Vascularization(혈관신생) • Cellular debris and other metabolic by-products may be other stimuli to vessel growth • Almost all soft lens patients will demonstrate some amount of vascularization

32. Vascularization(혈관신생)

33. Vascularization(혈관신생) • In most cases, vascularization is asymptomatic, but encroachment into the visual axis may result in a reduction in vision • Vascularization can be graded according to the number of quadrants and the extent to which the vessels have grown into the cornea

34. 원인 • Long-term wear of any soft lens, but particularly lenses with low Dk/L (aphakic, prism ballasted, etc.) • Extended wear

35. 진단 • Varying degrees of vessels encroaching into previously avascular cornea • Grade 1: Sectorial or circumlimbal vessel extension less than 0.5 mm, or 1 or 2 vessels extending less than 1.5 mm into cornea. • Grade 2: Sectorial or circumlimbal vessel extension 0.5 to 1.5 mm into cornea.

37. 치료/처치법 • Grade 1 or 2: monitor Q6mos • Grade 3: decrease wear time, increase Dk/L or refit to RGP material • Grade 4: refit to RGP material or D/C lens wear • Though vasc may regress, vessel walls do not disappear • Watch for development of ghost vessels

38. Polymegethism(폴리메가티즘) • A permanent condition of endothelial cell(내피) change such that the cells are no longer uniform but are of varying sizes

39. Endothelial blebs(내피 물집) • Transient, small, dark, non-reflective areas that appear shortly after lens insertion

40. 원인 • Long-term wear of any soft lens, but particularly lenses with low Dk/L (aphakic, prism ballasted, etc.), extended wear

41. 치료/처치법 • Change to higher Dk or RGP • Monitor for further cellular changes, corneal edema

42. DRY EYE / DESICCATION

43. Soft Lens Desiccation(탈수) • Soft lenses dehydrate when exposed to the atmosphere • As the lens dehydrates, it draws water from the post-lens tear film, resulting in dryness of the cornea in these areas • Tear flow dynamics from tight or high modulus soft lenses may contribute to this staining pattern

44. 원인 • Thin, high water soft lens • Borderline dry eye • Extended wear • Incomplete / infrequent blink • Dry environment • Heavy protein deposition

45. 진단 • Inferior central arcuate punctate staining

46. 치료/처치법 • Lubricating drops: unpreserved • Thicker lens design, prism ballast • Lower water content, non-ionic (group 1) • Lenses that have high water retention (Proclear, Extreme H20, Soflens 66) • Frequent replacement (if deposited with protein) • Punctal plugs

47. INFLAMMATION / INFECTION

48. Contact Lens-Induced Papillary Conjunctivitis (GPC)-유두상결막염 • Typical symptoms • Itchiness • Stringy mucous discharge • Lens intolerance • Hallmark sign is large papillae on the superior palpebral conjunctiva

49. A combined immunological and mechanical response to denatured tear proteins that have adhered to the lens surface(렌즈의 침전물에 의한 일종의 알레르기성 반응)

50. 원인 • Aged soft lens • high water content • ionic • Aged rigid lens • silicone acrylate • Poor compliance to cleaning regimen • No enzymatic cleaning