Internal astigmatism and its correlation to corneal and refractive astigmatism.
Article
in English
| IMSEAR
| ID: sea-39267
ABSTRACT
OBJECTIVE:
To evaluate the internal astigmatism and its relationship to corneal and refractive astigmatism in a refractive surgery patient population.METHOD:
Patients who underwent pre-operative evaluation for Laser in situ Keratomileusis (LASIK) at Excimer Laser Clinic, Siriraj Hospital, Mahidol University were included. Pre-operative data including age, manifest refraction and corneal topography obtained by Orbscan Corneal Topography were performed. Regression Analysis was done to find the correlation between refractive and corneal astigmatism.RESULTS:
110 patients (220 eyes 110 right eyes and 110 left eyes) were included. The mean age was 31.14 +/- 7.00 year (range 19 to 48 years). The mean astigmatism measured by manifest refraction (refractive astigmatism) was 0.76 +/- 0.72 diopters (range 0 to 3.50 diopters). The mean astigmatism measured by Orbscan Corneal Topographer (corneal astigmatism) was 1.38 +/- 0.72 diopters (range 0.20 to 5.30 diopters). The mean difference in magnitude of refractive and corneal astigmatism (internal astigmatism) was 0.62 +/- 0.67 diopters (range 0 to 3.00 diopters) and 74 per cent were within +/- 1.00 diopters difference. The mean difference in axis of astigmatism was 0.95 +/- 23 degree (range 0 to 85 degree) and 79.6 per cent were within +/- 15 degree difference. There was low correlation between corneal and internal astigmatism (R2 = 0.12, p < 0.05), also low correlation between refractive and internal astigmatism (R2 = 0.27, p < 0.05). There was a statistically significant difference between magnitude of corneal and refractive astigmatism (p < 0.05) but no difference in the axis of astigmatism (p = 0.55).CONCLUSION:
This study demonstrated non-mutual agreement between refractive and corneal astigmatism (presence of internal astigmatism). High value (> 1.00 diopter) of internal astigmatism was demonstrated in 1/3 of the cases. Kerato-refractive surgery that attempts to correct refractive astigmatism at corneal plane may effect long-term evaluation of the astigmatism.
Full text:
Available
Index:
IMSEAR (South-East Asia)
Main subject:
Postoperative Complications
/
Postoperative Period
/
Refraction, Ocular
/
Astigmatism
/
Severity of Illness Index
/
Preoperative Care
/
Female
/
Humans
/
Male
/
Visual Acuity
Type of study:
Diagnostic study
/
Etiology study
/
Incidence study
/
Observational study
/
Prognostic study
/
Risk factors
Language:
English
Year:
2003
Type:
Article
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