الفهرس | Only 14 pages are availabe for public view |
Abstract Cataract is the leading cause of reversible blindness worldwide. Cataract extraction with implantation of an intraocular lens (IOL) is the most frequently performed ophthalmic surgical procedure worldwide. Accurate calculation of the IOL power for attaining the desired postoperative refraction remains a research issue. Precise measurement of eye parameters is critical in modern ophthalmology. Several factors affect the refractive outcome after cataract surgery, including axial length, keratometry, and lens formulas. Of these factors the preoperative axial length measurement is a key determinant in the choice of intra-ocular lens (IOL) power. Traditionally, contact A-scan ultrasonography is used. This measures the time taken for sound to traverse the eye and converts it to a linear value (spikes) using a velocity formula. The distance between the corneal and retinal spikes gives the axial length of the eye. Keratometry reading (K1&K2) taken by autokeratometer data is entered into a-scan software to calculate the Iol power. silicone oil strongly absorbs and thus weakens the ultrasonic beam, echo signals from the retina are usually weak and sometimes even absent, so silicon filled eyes presents many technical and theoretical challenges to IOL power calculations. The IOL master 500 device is a computerized biometry device consisting of an OCT system to measure distances within the human eye along the visual axis, a Keratometer system to measure the corneal surface. This study aimed to compare the axial length change before silicon oil injection, 3 months after vitrectomy and silicon oil injection and 1 month after combined silicon oil and phacoemulsification procedure. A prospective clinical study that included 100 eyes of 100 consented patients undergoing retinal detachment repair via 3-port vitrectomy with silicon oil injection and combined silicon oil removal with phacoemulsification with in the bag foldable IOL implantation after 3-6 months will be included in our study. There were no significant differences in the mean values of axial length by IOL master at different times of assessment (P=0.137). Otherwise, there was a significant higher mean values of the axial length measured by IOL master in silicon filled eyes than before operation (P1=0.053). On the other hands, there were no significant differences in the axial length either after silicon removal than before operation (P2=0.577) or after silicon removal than in silicon filled eyes (P3=0.167). There were no significant differences in the mean values of axial length by Ascan at different times of assessment (P=0.075). Otherwise, there was a significant higher mean values of the axial length measured by A- scan in silicon filled eyes than before operation (P1=0.025). On the other hands, there were no significant differences in the axial length either after silicon removal than before operation (P2=0.577) or after silicon removal than in silicon filled eyes (P3=0.167). There were no significant differences between the axial length measured by IOL master or the axial length measured by A-scan at different times of assessment. Summary 63 There is a mean increase of 0.71 mm in original axial length (ie measured after 3 months from the primary procedure of RD repair and silicon injection). Then amean decrease by 0.51 mm in comparing preremoval status and 1 month post silicon oil removal axial lengths .While, an overall mean increase of 0.20 mm comparing axial length state before silicon oil injection and finally after silicon oil removal. Also, The IOL master was found to be superior to A-scan as IOL master is less time consuming and more patient friendly than is A- scan ultrasound. However, IOL master has a failure rate, particularly in the presence of dense cataracts. That IOL powers should be increased by 2.16 D (when using traditional formulas based on 987m/s speed of ultrasonic waves used by IOL master and ultrasound machines) to anticipate the decrease of axial length (0.51 mm) and avoid post operative 2.16 D hyperopic shift |