Axial length and Refractive Status of Adults in South Western Nigeria

Author: Onabolu Oluwatoni1, Jagun Omodele2, Ajibode Haruna3, Fakolujo Victoria4

Category: Ubitech

Abstract:

Background: The axial length of the eye is the distance between the centre of the cornea and the retina. This is one of the determinants of the refractive state of the eye and a knowledge of this is useful in intraocular lens power calculation during cataract surgery. The main objective of this study is to report the normal distribution of axial length and refractive. Status of the adult eye in South Western Nigeria.

Methods: A multistage cluster random sampling technique was used to select participants. In Sagamu Local Government, who had axial length determination, automated refraction and biometry done.

Results: Three hundred and two adults participated in this study. There were 121 (40%) males. In 83% the axial length ranged between 22 mm and 24.5 mm. The mean axial length was 23.31---PlusMinusSymbol---0.91mm with males being significantly longer [p<0.001] and a progressive increase noted between 18 to 40 years of age. There were 213 participants with refractive errors, 55% were hyperopic while 16% were myopic. Axial length also showed a statistically significant but weak [R2 = 0.07] inverse correlation with the refractive states of the eye.

Conclusion: Axial length of the adult eye in South Western Nigeria was found to be inversely related to; but not an independently strong determinant of the refractive state of the eye..

Keywords: Axial length, Refractive, Nigerians

Full Text:

At birth, the average axial length [AL] of the eye is 17.0mm and this increases with age following a triphasic pattern1-3. The first phase of increase occurs within the first two years of life with an average growth of 4.4mm, the second increase of about 1.5mm occurs between ages 2 to 6 years, while the last phase extends into adulthood with another 1.0mm, resulting in an average adult eye of 23.9mm1, 4. The eye is able to form clear images by the process of refraction where light rays from infinity enter the eye and are bent mainly by the cornea and lens to form a clear image on the retina4 . The average refractive power of the adult human eye is +60.0 D5 and axial errors of refraction [myopia and hyperopia] are major causes of visual impairment and are correctable by lenses4 . Previous studies in different races have documented average AL diameters ranging from 22.61mm to 23.57mm.6-11 These values are higher in individuals with myopia as compared to emmetropia and hypermetropia.6-10 AL has also been shown to accounts for variability in the refractive state of the eye in different studies7,9,12 The purpose of this population based study is to determine the relationship between axial length and refractive status of normal adult eyes in South Western Nigeria as a possible predictive indices of the refraction of the eye. Materials and Methods: The study area was Sagamu Local Government Area [SLGA] which is one of the twenty local government areas in Ogun state located in the South western region of Nigeria. SLGA has a population of 253,421 people with 51% females and is divided into two health districts –

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