REFRACTIVE SURGERY & STRABISMUS:

1. REFRACTIVE SURGERY & STRABISMUS: PREDICTING & AVOIDING COMPLICATIONS Lionel Kowal, Ravindra Battu, Burton Kushner

2. Lionel Kowal‘Straight [ening] guy for the queer eye’ Ocular motility clinic RVEEH Senior Clinical Fellow, U of Melbourne 1st Vice President ISA Private Eye Clinic

3. Lionel Kowal$ interest

4. MODERN REFRACTIVE SURGERY > 12 yrs old n = millions Huge refereed literature • Patient satisfaction & visual symptoms after LASIKOphthalmology (2003) 110: 1371-1378 • 97% would recommend LASIK • Halos 30% Glare 27% Starbursts 25% !!

5. GUIDELINES FOR REF SURGEON / STRABISMOLOGIST • PROTECT PTS & REF SURGEONS FROM COMPLICATIONS THAT CAN BE ANTICIPATED • NOT DENY PTS Q-O-L ENHANCING PROCEDURE

6. GUIDELINES FOR REF SURGEON / STRABISMOLOGIST • SCREENING TECHNIQUES – FOR ALL PTS See Kowal [2000] and Kowal & Kushner [2003] 2. THIS TALK: MODERATE / HIGH RISK GROUPS ONLY

7. REFRACTIVE SURGERY & STRABISMUS AT RISK GROUPS 1.HYPEROPIA 2.MONOVISION 3. ANISOMETROPIA 4. KNOWN / PAST STRAB.

8. IMPORTANT MESSAGE HYPEROPIA IS NOT THE MIRROR IMAGE OF MYOPIA

9. Population of hyperopes ≠ Population of myopes •  mild amblyopia • Predisposed to esodeviation • Mild hyperopes: good UCV most of their lives

10. CONSIDER IN EVERY HYPEROPE Habitual hyperopic spectacle correction is being worn for good vision and possibly for control of esodeviation

11. PREDSIPOSITION TO STRAB IN HYPEROPES If recognised before RS: patient’s problem Not recognised before RS: your problem

12. Success of RS in myopia Primary factor : change in corneal curvature 2° factors : 2° aberrations, pupil, late ectasia

13. Factors for Success in hyperopiaALL OF : Change in corneal curvature & Amount & symmetry of residual hyperopia & Pre-existing predisposition to esodeviation & Effect of RS on fusional reserve & Decay of accom amp in future & Amount of latent hyperopia 2° factors: Acquired astigmatism, ↑ flap problems, 2° aberrations, loss of prismatic effects of spectacles, …

14. Treatment target in Myopia = Cyclo refraction Cyclo Ref should = Manifest Ref [within 0.5 DS] MR > CR : rule out underlying eXodeviation

15. Treatment target in hyperopia? No easy answer VISUAL PHYSIOLOGY LESSON #1 TYPES OF HYPEROPIA

16. Treatment target in hyperopia? Need to know ALL the H subtypes Absolute: min + for D T-hold Will allow good UCV Manifest: max + for D T-hold Max effect of H on D & N vision and on alignment Total H = Cyclo Ref Latent[TOTAL – MANIFEST] : will become manifest

17. TYPES OF HYPEROPIA TOTAL = Cyclo Ref PROBABLY STAYS STABLE FOREVER DS Years

18. TYPES OF HYPEROPIA DS TOTAL ACCOM AMP Years

19. TYPES OF HYPEROPIA DS TOTAL MANIFEST ABSOLUTE Years

20. TYPES OF HYPEROPIA DS TOTAL MANIFEST LATENT: ONLY REVEALED BY CYCLO Years

21. TYPES OF HYPEROPIA DS TOTAL Latent M FACULTATIVE A

22. FACULTATIVE HYPEROPIA Easily handled by patient’s normal accommodation ANY result in this range → good UCV If symmetric, good & comfortable UCV

23. HYPEROPIA TOTAL DS Z Latent Manifest Y Facultative X Absolute X : D age 20 : N 40 : N Y : D 20 : N 40 : N

24. HYPEROPIA TOTAL DS Z Latent Manifest Y Facultative X Absolute Z : RISK OF VISUAL DISCOMFORT, I/MITT BLUR RE ≠ LE : RISK OF ABNORMAL BINOCULAR VISION. ACCOM SPASM  INCREASING ESODEVIATION.

25. HYPEROPIA Any uncorrected H [short of full manifest H] → accommodation → accom conv → eso tendency if motor fusion is inadequate With time, any Latent H → Manifest [=‘Recurrent H’] → accommodation → accom conv → eso tendency .. Asymmetric accommodation→ accom spasm / [varying] accom convergence → eso tendency ..

26. Short term patient satisfaction after RS: Abs H → good UCV. Show that with this minimum vision - improving correction in place there is still adequate control of any latent E

27. MEASURING FUSIONAL RESERVES

28. Medium term patient satisfaction Correction > Abs H is required : Manifest Hyperopia Max effect on D & N vision and E

29. REFRACTIVE SURGERY & STRABISMUS Assessing results : VISUAL PHYSIOLOGY LESSON #2

30. Assessing resultsUse GOOD vision charts Test monocularly for D to T-hold : ETDRS / NVRI / Bailey Lovie Snellen: not enough crowding 6/6 – 6/12 Test monocularly for N to T-hold : Rosenbaum J cards / usual cards → N5 OK to assess strength of near add NOT OK to test to T-hold

31. Psychophysically valid near tests * NVRI near [ETDRS]: 25cm : N 2.5 Can be used @ 40 cm * Lea : 40 cm : 20/20 Can be used @ 25 cm * M cards : American MA Evaluation of Impairment 5th Edn T-hold : 0.3

32. NVRI NEAR TEST BAILEY LOVIE / ETDRS

33. LEA NEAR TEST

34. Case 1 : 32 yo WCF Wearing +4.75, + 5 DS OU no h/o strab Lasik → residual +2.25, +2 DS < AH UCV 6/7.5very happy BUT …… develops ET! No gls worn : accom amp fine for +2 DS BUT accomm conv  ET : not happy

35. Case 2 : 24 yo WCFWearing PALs to control near ET PALs NOT RECOGNISED ‘Successful’ RS: ET’ returns LESSON: look @ the glasses! Mark Optical Centers Use automated vertometer that will automatically detect PALs and Δs

36. REFRACTIVE SURGERY AND STRABISMUS

37. Case : 50 yo WCF Wearing +5 DS OU CR +7 DS OU Uncorrected H : + 2DS Ref lensectomy / Array → plano UCV 6/6 OU very happy 2 DS accomm → accomm conv to control XT 20∆ XT very unhappy

38. The safe hyperope for RS With AH correction in place: phoria ≤ 5 ∆ BIFR > 5 ∆ LH ≤ 1 DS MANY [?most] low hyperopes

39. REFRACTIVE SURGERY & STRABISMUS AT RISK GROUPS 1.HYPEROPIA 2.MONOVISION 3. ANISOMETROPIA 4. KNOWN / PAST STRAB.

40. MONOVISION Fawcett n = 118 48 : PLANNED MV 11/48 : ABNORMAL BINOCULAR VISION [ABV] ∑ 23% * intermittent or persistent diplopia * visual confusion * “binocular blur requiring occlusion to focus comfortably” NON - MV PTS : 2/70 [3%] HAD ABV p significant ∑13 pts with ABV

41. HOW MUCH ANISOMETROPIA TO PRODUCE ABV ? 13 pts with ABV : 1.8 DS 105 pts with no ABV : 0.5 DS P < 0.001

42. MONOVISION Fawcett JAAPOS 2001: SURGICAL MV  UNCORRECTABLE DEFICIENCY OF HIGH QUALITY STEREO Also seen in k/conus

43. MONOVISION #1 55 yo PRE - REF SX R -2.75/-1x85 6/9 L -2.25/-0.25x180 6/9 D: Ortho. N : 8 Δ Esophoria. 60” stereo POST LASIK : diplopia / visual confusion R: P 6/6 L sc 6/15 Rx -1.75 DS intermittent near ET 6 Δ MV: ↓ motor fusion phoria → tropia Glasses to correct MV: symptoms fixed

44. MONOVISION #2 52 yo PRE-REF SX R -4.00/-0.75x180 L-3.00/-1.5x160 6 Δ exophoria 60” stereo POST LASIK : blur, i/mitt diplopia R +0.25/-0.75x50; L -0.75/-0.25x130 [XT] D: 2 Δ, N: 10 Δ MV reduces motor fusion; phoria → tropia Lasik reversal of MV : now asymptomatic

45. MONOVISION→ FIXATION SWITCH DIPLOPIA Amblyopic eye [with scotoma] becomes fixing eye in some situations. Habitually fixing eye is now the deviating eye in those situations : no scotoma  diplopia no definite cases in this series

46. UNPLANNED MONOVISION 50 PRK PTS [White; ESA,1997] 3 MO. DELAY B/W EYES 1/50: FUSIONAL CONV ↓ FROM 35 TO 5Δ 0/50 HAD SYMPTOMS TEMPORARY MV ≠ PERMANENT MV

47. MONOVISION:PROBLEMS ? 20+% LONG STANDING SURGICAL MV DEGRADES SENSORY / MOTOR FUSION MORE THAN CL MV AND TEMPORARY SURGICAL MV

48. REFRACTIVE SURGERY & STRABISMUS AT RISK GROUPS 1.HYPEROPIA 2.MONOVISION 3. ANISOMETROPIA 4. KNOWN / PAST STRAB.

49. Knapp’s Law Axial a’metropia not / less aniseikonogenic c.f. corneal a’metropia OTHER FACTORS: RETINAL STRETCHING SENSORY ADAPTATIONS

50. CORNEAL REFRACTIVE SURGERY CONVERTS AXIAL A’METROPIA SAFE ACCORDING TO KNAPP → CORNEAL A’METROPIA AT RISK ACCORDING TO KNAPP