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Evaluation of Post-Trabeculectomy Visual Function Using Orbscan

Evaluation of Post-Trabeculectomy Visual Function Using Orbscan. Kozue Kasai MD 1 Tadashi Nakano MD 1 Takahiko Noro MD 1 Hideki Matsuda MD 1 Yoshinori Itou MD 1 Masayuki Tatemichi MD 2 Hiroshi Tsuneoka MD 1. 1 The Jikei University School of Medicine

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Evaluation of Post-Trabeculectomy Visual Function Using Orbscan

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  1. Evaluation of Post-TrabeculectomyVisual Function Using Orbscan Kozue Kasai MD1 Tadashi Nakano MD1 Takahiko Noro MD1 Hideki Matsuda MD1 Yoshinori Itou MD1 Masayuki Tatemichi MD2 Hiroshi Tsuneoka MD1 1 The Jikei University School of Medicine Department of Ophthalmology 2 Showa University

  2. 1. To evaluate changes in corneal topographic characteristics of patients after trabeculectomy (LEC). 2. To study the relationship of central corneal thickness using Orbscan. Purpose

  3. Methodsand Patients Post-trabeculectomy group with OAG 24 eyes Control group 16 eyes (nonoperated eyes of post-LEC patients or volunteer eyes) TOTAL 40 eyes (24 patients were examined with Orbscan at our glaucoma outpatient clinic)

  4. Methods * NIDEK ARK-700A ** Mann-Whitney U-test

  5. √ (Standard deviation of Mean power*)2+ (Standard deviation of astigmatic power**)2 Irregularity = ORBSCAN ver 3.0Evaluation items Using an illuminated ring pattern and a beam of light, Orbscan shows surface power and the front and back shapes. Not effected by eye dryness. Time: less than 2 seconds Using two groups (3-mm and 5-mm zone irregularity [ZI]) * Mean power: The average of the maximum and the minimum of the cornea refractivity in the arbitrary measurement point ** astigmatic power: The difference of the maximum and the minimum of the cornea refractivity in the arbitrary measurement point

  6. Methods 1. Zone Irregularity 5-mm ZI Corneal irregularity of paracentral quadrants mydriasis (night condition) 5-3-mm ZI Difference between 5-mm ZI and 3-mm ZI (5-3-mm ZI) as an index of the peripheral area 3-mm ZI Centralcorneal Irregularity miosis (daytime condition) 2. Corneal thickness Corneal thickness was measured by Orbscan slit scan pachymetry. A representation of the central corneal thickness. (within a 3-mm circle from the center)

  7. 7 6 5 4 3 2 1 0 Results 1 Irregularity vs treatment * Irregularity * * Post-LEC Control Post-LEC Control Post-LEC Control 3-mm Zone 5-mm Zone 5‐3-mm Zone Mann-Whitney U-test * P < 0.5 ** P < 0.01 *** P < 0.001 Irregularity was greater in the Post-LEC group than in the control group in all zones.

  8. Results 2 Irregularity vs Corneal thickness Irregularity ** 12 ** 10 * 8 6 4 2 0 <540 m ≧540 m <540 m ≧540 m <540 m ≧540 m 3-mm Zone 5-mm Zone 5‐3-mm Zone Mann-Whitney U-test * P < 0.5 ** P < 0.01 *** P < 0.001 Irregularity was greater with corneal thickness < 540m than with corneal thickness ≧540 m in the zones.

  9. Report of Evaluation of Post-trabeculectomy 1. Video-keratoscopy After LEC, the peripheral parts of the cornea near the scleral flap area become steep. After LEC, visual acuity decreased with topographic changes near the scleral flap. 2. TMS-1 TMS-2 Video-keratoscopy After LEC, there are no changes in SRI or SAI as indexes of astigmatic irregularity. 3. TMS-1 After LEC, The steep area around the cornea does not influence the corneal center. 4. OPD-scan After LEC, surgically induced astigmatism and higher-order aberrations increase significantly. Contrast sensitivity is decreased. Back Ground 1. The importance of quality of vision (QOV) is widely recognized. 2. Towards the Standaridization of QOV (Quality of vision),the list of clinical useful parameters need to be evaluated. 3. Corneal astigmatism is a factor in QOV. It can’t be predicted before surgery. 4. The irregularity astigmatism is important, but postoperative QOV deteriorates because of the regular astigmatism.

  10. Conclusion 1 1. Irregularity was significantly greater in the post-LEC group. ZI may serve as a new index of postoperative quality of vision. 2. Irregularity was significantly greater when corneal thickness was less than 540m. Central cornea thickness may be a useful predictor of surgically induced astigmatism.

  11. Conclusion 2 1. Orbscan is an effective method for evaluating visual function after trabeculectomy. 2. The results of this study suggest that corneal thickness may have a significant effect on changes in corneal shape after glaucoma surgery.

  12. References 1. Rosen WJ, Mannis MJ, Brandt JD : The effect of trabeculectomy on corneal topography. Ophthalmic Surg. 1992 Jun;23(6):395-8. 2. Claridge KG, Galbraith JK, Karmel V, Bates AK : The effect of trabeculectomy on refraction, keratometry and corneal topography. Eye. 1995;9 ( Pt 3):292-8. 3. Vernon SA, Zambarakji HJ, Potgieter F, Evans J, Chell PB : Topographic and keratometric astigmatism up to 1 year following small flap trabeculectomy (microtrabeculectomy). Br J Ophthalmol. 1999 Jul;83(7):779-82. 4. Cunliffe IA, Dapling RB, West J, Longstaff S: A prospective study examining the changes in factors that affect visual acuity following trabeculectomy. Eye. 1992;6 ( Pt 6):618-22. 5. Maeno A, Hayashi K, Oshika T et al : Fourier analysis of corneal astigmatism after trabectomy. Rinsho Ganka (Jpn J Clin Ophthalmol) 54(4): 587-590. 2000 6. Toyokawa N, Miyata M, Kimura H et al : The effect of glaucoma surgery on postoperative visual function. Rinsho Ganka (Jpn J Clin Ophthalmol) 62(4): 461-465. 2008 7. Jordan JF, Joergens S, Dinslage S, Dietlein TS, Krieglstein GK : Central and paracentral corneal pachymetry in patients with normal tension glaucoma and ocular hypertension. Graefes Arch Clin Exp Ophthalmol. 2006 Feb;244(2):177-82. Epub 2005 Aug 2. 8. Radford SW, Lim R, Salmon JF : Comparison of Orbscan and ultrasound pachymetry in the measurement of central corneal thickness. Eye. 2004 Apr;18(4):434-6.

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