engleski

ECHOBIOMETRY IN DEFINING OCULAR OPTICAL COMPONENTS INTERACTION

Purpose: To prove the hypothesis of existence of certain physiologic variation of emmetropic eye optical components as a part of emmetropization. These variations allow optical components to interact in a way that results in emmetropia. Design: cohort study Participants: Prospective evaluation of both eyes of 1000 healthy emmetrops. Methods: Horizontal-white-to-white reading, corneal radius measurement, keratometry, echobiometry and IOL calculation using SRK II, SRK/T and Holladay formula, with constant A=117,4 and 118,5, were performed. Main Outcome Measures: Horizontal-white-to-white reading, corneal radius, keratometry of horizontal and vertical meridian, anterior chamber depth, lens thickness, vitreous chamber length, axial length, lens capsule diameter, ciliary sulcus, astigmatism, IOL values for emmetropization Results: Corneal radius, keratometry, vitreous chamber length, axial length and lens thickness are the most important optical components and regulators of emmetropization. Ocular optical components in emmetrops correlate with each other following certain pattern. The linear correlation coefficients of the axial length represents the best this pattern. It is positive and the highest for the vitreous chamber length, positive and high for the corneal radius, positive and lower for the anterior chamber depth, negative for the keratometry and the lens thickness. The ocular optical component that changes the most with increase of axial length is the vitreous chamber length. It increases the most. Anterior chamber deepens, probably as a combined result of response to axial length increase and thinning of the lens. Mechanisms that try to maintain emmetropia and fight ametropia are lens thinning, decrease of corneal power and increase of corneal radius on both meridians. Model of healthy emmetropic eye would have optical components median values as follows: corneal radius=7 mm, horizontal-white-to-white=11 mm, lens capsule diameter=10 mm, ciliary sulcus=12 mm, keratometry of horizontal meridian=42,25 D, keratometry of vertical meridian=43 D, astigmatism= -0,75 D, anterior chamber depth=3,33 mm, lens thickness=3,94 mm, vitreous chamber length=16,20 mm, axial length=23,4 mm, IOL Holladay=21 D, IOL SRK II 117,4=20,5 D, IOL SRK II 118,5=21,5 D, IOL SRK/T 117,4=20,5 D, IOL SRK/T 118,5=21,5 D. Conclusion: The existence of certain physiologic variation of ocular optical components in emmetrops has been proven. Because of these variation, optical components are able to bond in a way to create emmetropia.

biometry; emmetrops; optical components

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