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Determination of the effect of various biometric parameters on the optic power of IOL and algorithms of the sensitivity of some calculating formulas

Poster Details

First Author: B.Babayeva AZERBAIJAN

Co Author(s):    L. Bilandarli              

Abstract Details



Purpose:

Age of high computer research and nanotechnology necessitates extending the active life and permanently high level of its quality . In this regard, it is difficult to overstate the importance of good vision. Taking into account the bad ecology, increased solar insolation, permanent visual load, we must regretfully assert: cataract is significantly younger now. It therefore becomes particularly relevant IOL calculation precision with which surgeons can bring the patients back to their normal life and activities. In the literature there are reports in which the authors argue that the main factor for the accurate intraocular lens (IOL) calculation is axial length (AL) , while other indicators, such as average keratometry (AvgK), anterior chamber depth (ACD) , lens thickness and white-to-white (WTW) have much less influence. Based on the foregoing, it seems relevant statistically determine how different biometrics components affect the calculation of the IOL power.

Setting:

National Centre of Ophthalmology named after academician Z.A.Aliyeva, Baku, Azerbaijan.

Methods:

To implement this task we will theoretically analyzed the following data: 1) Constant AL and AvgK at variable ACD; 2) Constant AL and ACD at variable AvgK; 3) Constant ACD and AvgK at variable AL.

Results:

Analyzing the data 1, we can say that preoperative ACD virtually no effect on the optical power of the IOL. We have been calculated 21 IOLs at constant AL=23,5mm and AvgK=43,5D using Holladay 2 and SRK-T formulas. The optical power of the IOL has not changed in any case. Calculating the optical power of the IOL at constant AL=23,5mm and ACD=3,0mm and AvgK ranging from 42,0 to 44,0D using either of the formulas it was observed 5 changes. In this situation algorithm changes using Holladay was: {4-5-3-5-4}, using SRK-T: {2-4-5-5-5}. It can be assumed that the eye with low values of AvgK more sensitive is the SRK-T, because lens changes in this segment sampling occurs more frequently. Data 3 shows that at constant ACD=3,0 mm and the AvgK 43,5D and AL, varying from 22,5 to 24,5 mm optical power of the IOL changes occur at 15 times counting on Holladay and 14 times - when SRK-T. In the first case, the algorithm was as follows : { 1-1-2-1-2-1-1-2-1-2-2-1-2-1-2 }; in the second case: {1-2-1 -2-1-2-1-2-2-1-2-1-2 } . Obviously, the sensitivity of both formulas in the sample is almost the same, although there is a slight advantage counting on Holladay.

Conclusions:

In summary, we can draw the following conclusions: 1. The major role in the IOL power calculation for medium proportional eye belongs to AL and AvgK values, whereas the ACD has no effect on the calculation. 2. The degree of influence of the AL and AvgK on the IOL optical power can be defined as 1:3. 3. Analysis of the sensitivity of formulas Holladay and SRK-T for eyes with constant average AL and ACD and varying AvgK in the range 42,0 - 44,0 D, give us the opportunity to recommend for eyes with low AvgK use formula SRK-T, for eyes with high AvgK - Holladay. 4. Analysis of the sensitivity of formulas Holladay and SRK-T for eyes with constant ACD and AvgK and AL varying in the range 22,5 - 24,5mm not determined a clear advantage of one over the other formulas. FINANCIAL INTEREST: NONE

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