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Contrast sensitivity: sensitive criterion of visual quality evaluation

Poster Details

First Author: O.Klokova RUSSIA

Co Author(s):    S. Sakhnov   I. Geiko           

Abstract Details



Purpose:

A prospective study of visual acuity (VA) and contrast sensitivity (CS) results in different conditions in patients with myopia of mild and average degrees with astigmatism up to 1.5 D before and after refractive femtosecond lenticule extraction (ReLEx) by SMILE (Small Incision lenticule Extraction) surgery.

Setting:

Krasnodar Branch FSBI 'The Academician S.N. Fyodorov IRTC 'Eye Microsurgery' of the Ministry of Public Health of the Russian Federation.

Methods:

The study group included 12 patients (24 eyes) aged from 18 to 38 years (23.5±0.9), the follow-up period was not less than three months. The mean spherical component before the operation was -4.44±0.43D (-2.0D to -6.25D), the mean cylindrical component was -0.75±0.17D (-0.25 to -1.5), mean UCVA and BCVA were 0.11±0.06 and 0.96±0.2 accordingly. All patients were performed femtosecond lenticule extraction by SMILE technology on the laser system VisuMax® (Carl Zeiss Meditec AG, Jena, Germany) with the pulse frequency of 500 kHz. The average lenticule diameter was 6.2±0.33 mm (6.0 mm to 6.5 mm), in the astigmatism correction transition zone was 0.1 mm. CS and VA with glare was carried out at OPTEC 6500 Vision Tester (Stereo Optical Co. Inc., USA) under photopic conditions (85 Cd/m2, with and without glare) and under mesopic conditions (3 Cd/m2, with and without glare) before and 1 day, 2 weeks, 1, 3, 6 months after operation at spatial frequencies 1.5, 3, 6, 12, 18 cycle/degree. Control data were based on healthy group comprised 12 people (24 eyes) with mean age 26.3±1.4 (23 to 34). Before the operation examinations were carried out with optimal spectacle correction, after the operation - without correction.

Results:

After SMILE the study group patients' refraction ±0.5D was achieved in 95.9% of cases, ±1.0D - in 100% of cases. UCVA 0.83±0.18 and BCVA 0.88±0.18 indicators only for the first day after operation were significantly lower (p<0.05) than preoperative values of BCVA (0.96±0.18). Three months after the correction UCVA and BCVA indicators were identical and equal to preoperative BCVA 0.97±0.18 and 0.96±0.18 accordingly. VA with mesopic conditions and glare after 1 day and 1, 3, 6 postoperative months were as follows 0.51±0.14, 0.7±0.17, 0.79±0.18, 0.80±0.18 which are significantly lower (p<0.05) than control data (1.0±0.2). CS in SMILE group under photopic and mesopic conditions before and 1 day, 2 weeks at spatial frequencies 1.5, 3, 6, 12, 18 cycle/degree after correction were significantly lower (p<0.05) than the control group indicators. A comparison of CS before and at different periods after the operation showed that after 3-6 months after SMILE the examined parameters of CS were significantly improved (p<0.01), but didn't reached the control group indicators. For example, in mesopic conditions with glare preoperative indicators were 21.0±0.9, 25.4±1.0, 13.8±0.7, 5.6±0.48, 0.6±0.1 and after SMILE - 31.6±1.1, 35.3±1.2, 22.3±0.96, 8.9±0.6, 1.2±0.22 and in the control group - 51.0±1.4, 66.7±1.6, 50.3± 1.4, 19.3±0.8, 5.9±0.4

Conclusions:

Analysis of the prospective study results allows to regard femtosecond lenticule extraction by SMILE for myopia with astigmatism correction as an effective and safe method that can be considered as an alternative to LASIK traditional technology or femtosecond laser (FemtoLASIK) use. During the operation and postoperative period in none of the cases the complications were noted. Refractive data have stabilized for 1-2 weeks and reached planned emmetropic refraction has been remaining stable during the whole follow-up period. We consider it's necessary to be noted that the average UCVA only in the first days after the operation is slightly lower preoperative indicators of BCVA. In the first month in the majority of cases UCVA reaches or exceeds BCVA level before the operation. At the same time the VA indicators in the examined group with reduced light and intense glare (in real life such conditions are taken place when you are driving at dusk with the headlights of oncoming cars) as before the operation, and at the end of the observation period were lower than in the control group. It can be concluded, that the adaptive possibility of a healthy person's visual analyzer is higher. The study of contrast sensitivity before the operations also showed that patients with myopia of mild and average degree and astigmatism not more than 1.5 D, in spite of optimal spectacle correction, have significantly lower CS indicators than in the control group. The performed study found that the existing differences in visual quality in patients of the examined group from the control group after SMILE are leveled. But it should be noted that visual quality is restored for few months, what agrees with the other authors` data after different methods of laser correction. Our work is continuing in the study of this question. FINANCIAL INTEREST: NONE

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