¡¡¡¡The mean refractive error detected 4.60¡À1.90D, in male patients were 4.70¡À1.90D and 4.59¡À1.90D in female patients. We have found a correlation between corneal thickness and refractive error severity (P=0.000, r=0.28), a reverse significant relation between corneal thickness and keratometry (P=0.005, r=0.16), a positive relation between corneal thickness and pupil diameter (P=0.013, r=0.144), a reverse correlation between refraction error severity and depth of anterior chamber (P=0.132, r=ª² 0.87) and a significance relation between refraction error severity and keratometry(P=0.061, r=ª² 0.108).

¡¡¡¡DISCUSSION

¡¡¡¡Corneal topography is widely used to interpret corneal morphologic patterns and the Orbscan II seems to be a predictable and useful device for measuring corneal topography[6,7]. Hyperopia has been less studied because of its lower prevalence in developed countries, relative stability, and difficulties in measuring its magnitude accurately in young subjects[8].

¡¡¡¡In our study, the mean corneal thickness differs significantly between age group of 17ª²29 years old and other age groups. It also appears the corneal thickness in female differs to male. These indicate that the young hyperopes in our study have a good balance of corneal and internal spherical aberration in compration of older hyperopes. Ocular aberrations have been reported to increase with age[9ª²12] and Artal et al[9,13] showed that aging disrupts the balance between corneal and internal optics found in young eyes.

¡¡¡¡Cho et al[14] reported that central corneal thickness decreased with increasing age but appeared to be due to female subjects only. In a study by Cosar et al[15] on 1341 eyes of 688 consecutive patients who had a LASIK evaluation; age was correlated with corneal thickness, spherical equivalent, and inversely correlated with corneal diameter, anterior chamber depth and pupil size: males had larger corneas and deeper anterior chambers than females. These underline the influence of age, sex, and refractive state of the eyes on dimensions of anterior structures of the human eye.

¡¡¡¡Reverse correlation between refractive error severity and depth of anterior chamber and a mild difference of the depth of anterior chamber in female and age group of 45ª² 67 years old in our study detected; Dacosta et al[16] also reported mean central anterior chamber depth(ACD )decreased with age and was shallower in females than in males. It was highest in myopes and lowest in hypermetropes this relationship between a shallow anterior chamber and a thick cornea may be explained by the fact that a thick cornea takes away some space from the anterior chamber so that the chamber depth becomes shallower[17]. In a study by Hosnyet al[18], The ACD was found to correlate significantly with both the average corneal diameter and the axial length of the globe and was also found to correlate through an inverse relation with both age and spherical equivalent refraction. Corneal thickness and keratometric power did not correlate with the anterior chamber depth. This relation between age, gender and depth of anterior chamber also has been suggested in an Populationª²based study on Chinese adults by Xu et al[17]. Rabsilber et al[19] also reported significantly lower ACD values in the hyperopia group than in emmetropia and myopia groups when they assess the reliability of repeated anterior chamber depth measurements using the Orbscan II Topography System.

¡¡¡¡A significance relation between refraction error severity and keratometry (P=0.061,r=ª² 0.108 )in our findings can be explained the findings of Rabsilber et al[19] in a corneal topography measurement using the Orbscan II topography system referring to different refractive conditions; for keratometry in particular, patients with hyperopia had significant differences (P<0.01)and patients with astigmatism and especially hyperopia showed significantly higher SD values in peripheral zones for anterior elevation and keratometry, indicating a lower reliability, compared with the emmetropic cohort.

¡¡¡¡CONCLUSION

¡¡¡¡This article provides a description and analysis of Orbscan II corneal topography of a normal population with hyperopia. The findings suggest some normal values of Orbscan II corneal topography in hyperopic patients that will aid in preoperative assessment in refractive surgery.

¡¡¡¡Acknowledgements: This manuscript provided based on results of graduating thesis titled in "Topography evaluation in patients with hyperopia refractory disease referal to LASIK center during 2005ª²2006"by Mrs. Dehyadegari.

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