A Critical Assessment of Friedenwald’s Technique for Estimating the Coefficient of Rigidity of the Cornea
Purpose. To determine if Friedenwald’s technique for estimating the coefficient of corneal rigidity (Ko, units mmHg/μL), could differentiate between the cornea in keratoconus, normal eyes, and after crosslinking (CXL). Methods. Two operators (1 and 2) independently measured Ko in three groups (kerat...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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Wiley
2022-01-01
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| Series: | Journal of Ophthalmology |
| Online Access: | http://dx.doi.org/10.1155/2022/6775064 |
| _version_ | 1826834992318119936 |
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| author | Larysa Tutchenko Sudi Patel Mykhailo Skovron Olha Horak Oleksiy Voytsekhivskyy |
| author_facet | Larysa Tutchenko Sudi Patel Mykhailo Skovron Olha Horak Oleksiy Voytsekhivskyy |
| author_sort | Larysa Tutchenko |
| collection | DOAJ |
| description | Purpose. To determine if Friedenwald’s technique for estimating the coefficient of corneal rigidity (Ko, units mmHg/μL), could differentiate between the cornea in keratoconus, normal eyes, and after crosslinking (CXL). Methods. Two operators (1 and 2) independently measured Ko in three groups (keratoconus, normal, and post-CXL corneas), and repeated the procedure in some where their care remained unchanged and others after routine CXL (>28 days postop, epi-off treatment, 3.0 mW/cm2, 30 min). The data were subsequently used to quantify interoperator error, test-retest/intersessional reliability for estimation of Ko, the significance of intergroup differences, and the effect of CXL on Ko. Results. The major findings were: (i) Ko values were not normally distributed; (ii) mean (±sd, 95% CI) interoperator error was -0.002 (±0.019, −0.006 to 0.003, n = 95) and the limit of agreement between the operators was ±0.039; (iii) RMS differences in the intersessional estimation of Ko values were 0.011 (operator 1) and 0.012 (operator 2); (iv) intergroup differences in Ko were not significant (p>0.05); (v) intersessional change in Ko (y) was linearly related to Ko estimated (x) at 1st session (for operator 2 y = 1.187x−0.021, r = 0.755, n = 16, p<0.01); and (vi) change in Ko (y1) after CXL was linearly related to Ko (x1) at preop (for operator 2 y1 = 0.880x1−0.016, r = 0.935, n = 20, p<0.01). Conclusion. Friedenwald’s technique for estimating the Ko is prone to substantial interoperator error and intersessional differences. According to the technique, the change in Ko following CXL is on par with the expected intersessional change observed in controls. |
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| format | Article |
| id | doaj.art-1800602067c3455f837fae90b9dfaee2 |
| institution | Directory Open Access Journal |
| issn | 2090-0058 |
| language | English |
| last_indexed | 2025-02-16T11:02:25Z |
| publishDate | 2022-01-01 |
| publisher | Wiley |
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| series | Journal of Ophthalmology |
| spelling | doaj.art-1800602067c3455f837fae90b9dfaee22025-02-03T01:21:04ZengWileyJournal of Ophthalmology2090-00582022-01-01202210.1155/2022/6775064A Critical Assessment of Friedenwald’s Technique for Estimating the Coefficient of Rigidity of the CorneaLarysa Tutchenko0Sudi Patel1Mykhailo Skovron2Olha Horak3Oleksiy Voytsekhivskyy4Kyiv City Clinical Ophthalmological Hospital “Eye Microsurgical Center”Specialty Eye Hospital SvjetlostKyiv City Clinical Ophthalmological Hospital “Eye Microsurgical Center”Kyiv City Clinical Ophthalmological Hospital “Eye Microsurgical Center”Kyiv City Clinical Ophthalmological Hospital “Eye Microsurgical Center”Purpose. To determine if Friedenwald’s technique for estimating the coefficient of corneal rigidity (Ko, units mmHg/μL), could differentiate between the cornea in keratoconus, normal eyes, and after crosslinking (CXL). Methods. Two operators (1 and 2) independently measured Ko in three groups (keratoconus, normal, and post-CXL corneas), and repeated the procedure in some where their care remained unchanged and others after routine CXL (>28 days postop, epi-off treatment, 3.0 mW/cm2, 30 min). The data were subsequently used to quantify interoperator error, test-retest/intersessional reliability for estimation of Ko, the significance of intergroup differences, and the effect of CXL on Ko. Results. The major findings were: (i) Ko values were not normally distributed; (ii) mean (±sd, 95% CI) interoperator error was -0.002 (±0.019, −0.006 to 0.003, n = 95) and the limit of agreement between the operators was ±0.039; (iii) RMS differences in the intersessional estimation of Ko values were 0.011 (operator 1) and 0.012 (operator 2); (iv) intergroup differences in Ko were not significant (p>0.05); (v) intersessional change in Ko (y) was linearly related to Ko estimated (x) at 1st session (for operator 2 y = 1.187x−0.021, r = 0.755, n = 16, p<0.01); and (vi) change in Ko (y1) after CXL was linearly related to Ko (x1) at preop (for operator 2 y1 = 0.880x1−0.016, r = 0.935, n = 20, p<0.01). Conclusion. Friedenwald’s technique for estimating the Ko is prone to substantial interoperator error and intersessional differences. According to the technique, the change in Ko following CXL is on par with the expected intersessional change observed in controls.http://dx.doi.org/10.1155/2022/6775064 |
| spellingShingle | Larysa Tutchenko Sudi Patel Mykhailo Skovron Olha Horak Oleksiy Voytsekhivskyy A Critical Assessment of Friedenwald’s Technique for Estimating the Coefficient of Rigidity of the Cornea Journal of Ophthalmology |
| title | A Critical Assessment of Friedenwald’s Technique for Estimating the Coefficient of Rigidity of the Cornea |
| title_full | A Critical Assessment of Friedenwald’s Technique for Estimating the Coefficient of Rigidity of the Cornea |
| title_fullStr | A Critical Assessment of Friedenwald’s Technique for Estimating the Coefficient of Rigidity of the Cornea |
| title_full_unstemmed | A Critical Assessment of Friedenwald’s Technique for Estimating the Coefficient of Rigidity of the Cornea |
| title_short | A Critical Assessment of Friedenwald’s Technique for Estimating the Coefficient of Rigidity of the Cornea |
| title_sort | critical assessment of friedenwald s technique for estimating the coefficient of rigidity of the cornea |
| url | http://dx.doi.org/10.1155/2022/6775064 |
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