| With the fast development and expanding of laser in situ keratomileusis(LASIK), new technologies such as Corneal topography system, Orbscan slit scanning cornealtopography system which aimed to exam corneal morphology and thickness were also developed and became more perfectely. Compared with Corneal topography system, Orbscan slit scanning corneal topography system has more powerful functions in evaluating corneal morphology, pachymetry, anterior chamber depth, diameter of cornea and so on. In this study, we plan to investigate the corneal morphology and thickness in myopias with the Orbscanll corneal topography system to supply more useful information for the diagnosis of corneal disease and refractive surgery. 1. Materials and Methods200 cases of myopia (353eyes) and 200 young men and women (381 eyes) were involved in this study. Aaccording to refractive error, the myopic eyes were divided into 4 groups, low myopia group: -1.00~ - 3. OOD in 85 eyes; moderate myopia group: -3.25~-6.00 D in 95 eyes;high myopia group: -6.25 ~-10.00 D in 90 eyes; severe myopia group:- 10. 00~-15. 00 D in 83 eyes. Anterior corneal surface elevation map, posterior corneal surface elevation map, value and location of posterior corneal protrusive pole, and corneal thickness were examined by the Orbscanll corneal topography system.The results were analysed with SPSS10. 0. 2. ResultsIn the normal eyes, the island type was the the most commonly observed pattern(72%)in the anterior corneal surface elevation map, but in myopic eyes, incomplete ridge was the most common type, the rate of incomplete ridge in the different myopia groups were 48%, 65%, 60% and 61% respectively. For posterior corneal surface elevation map,island type was the most common pattern both in normal and myopic eyes. The value of posterior corneal protrusive pole was 28. 05 +10. 05 m in normanl eyes and 27.66 8. 31 m, 29. 0 9. 62 m, 26. 88 + 9. 10 u m and 29. 90 9. 51 u m in the diferrent groups of myopic eyes. There were significantdifferences between normal eyes and the different myopic group eyes(P>0. 05). The posterior corneal protrusive pole both in normal and myopic eyes were mostly located at the inferotemporal quarter, followed by inferonasal , superotemoral and superonasal quarter, but, with the increase of myopia, it shifted to the inferonasal quarter.In normal eyes, the central corneal thickness was 556. 1 + 33. 7 m, in the different myopia groups, the central corneal thickness were 554. 2 + 33. 9 m, 551. 6 + 32. 7 m, 549. 1 30. 2um and 548. 5 + 31. 6 m respectively. There was no significant difference between normal and myopia groups(P>0. 05). The thinnest corneal point was 533. 6 + 32. 7 m, in myopia groups, it was 534. 6+33. 9 m, 532, 6+34. 7 m, 530. 1 + 29. 2 m and 535. 5 27. 6 m respectively. There was also no significant difference between normal and myopia groups(P>0. 05).3. Conclusions(1) Orbscanll corneal topography system can provide useful and accurate information in defining the morphology and thickness of myopia, which is important in the diagnosis of corneal diseases and refractive surgery.(2) In myoic eyes, the incomplete ridge was the most common pattern in the anterior corneal surface elevation map.(3) There is no relationship between the refractive error and the value of the posterior corneal protrusive pole in myopic eyes.(4) In myopic eyes, the posterior corneal protrusive pole is mostly located at the the the inferotemporal quarter, with the increase of myopia, it shifts to the inferonasal quarter.(5) Between normal and myopic eyes, there is no significant difference both in the central corneal thickness and the thinnest corneal point. |
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