The relationship between the sagitta of the anterior corneal surface and refractive error of the eye.
Optom Vis Sci
; 81(8): 636-9, 2004 Aug.
Article
en En
| MEDLINE
| ID: mdl-15300123
ABSTRACT
Changes in the sagitta of the anterior corneal surface associated with a change in the corneal radius of curvature have been used to calculate the change in refractive error of the eye in two areas the ablation depth for laser surgery, and the change in corneal thickness associated with orthokeratology lens wear. An approximate formula known as Munnerlyn's formula is commonly used to calculate the refractive error change from sagittal data. This article compares the change in refraction calculated using the approximate formulae with the change calculated from a formula based on an elliptical corneal section. The approximate formula underestimates the ablation depth for a given refractive change and overestimates the refractive change for a given change in corneal thickness, assuming a constant asphericity. When the corneal asphericity increases together with an increase in radius of curvature, a suggested mechanism in orthokeratology, the approximate formula underestimates the change in ocular refraction.
Buscar en Google
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Errores de Refracción
/
Córnea
Límite:
Humans
Idioma:
En
Revista:
Optom Vis Sci
Asunto de la revista:
OPTOMETRIA
Año:
2004
Tipo del documento:
Article
País de afiliación:
Nueva Zelanda