Dr. Savio Pereira, P17052, Dr.
Sri Ganesh, Dr. Sheetal Brar
Title: Clinical outcomes and quality of vision with new Extended Range of Vision (ERV) Intraocular Lenses
Purpose: To evaluate the visual outcomes, quality of vision and patient satisfaction with new ERV Intraocular Lenses.
Methods: All patients underwent bilateral implantation with Tecnis Symfony IOL with micromonovision, where the dominant eye was targeted at emetropia and non dominant eye targeted at -0.75 D . The main outcome measures were postoperative uncorrected and corrected distant, intermediate and near visual acuity , defocus curve and contrast sensitivity. The Salzburg Reading Desk (SRD) was used to assess reading performance at 40, 60 and 80cm. Mean follow up was 180±11 days.
Results: 50 eyes from 25 patients with mean age of 62.6±9.1 years were included. At 6 month post-operative, the mean binocular UDVA, CDVA, UCNVA and DCNVA were ± , , , and , logMAR respectively. The binocular UCIVA and DCIVA were and log MAR at 60 and and log MAR at 80 cm. All patients had ≥ 0.2 logMAR UDVA and UCNVA. Reading acuity and reading speeds showed improvement over time . Mean visual acuity in the defocus range of +1.5 to -1.5D was between 6/9-6/6. All patients had contrast sensitivity values within normal range. 95% patients reported seeing a single halo/circle around light at night, which did not seem to bother them. 4 patients reported using reading glasses for very fine print.
Conclusion: Satisfactory outcomes were achieved at far, intermediate and near distances, with good tolerance to micro-monovision. Results were best for intermediate followed by distance and near range of vision. Patient satisfaction was good with minimal spectacle dependence and complaints of dysphotopsia.
Key words: Extended Range Vision, ERV, micro-monovision.
Trial registration number:
Introduction
Materials and Methods
This prospective comparative study included 50 eyes from 25 patients undergoing bilateral cataract surgery with implantation of the Tecnis Symfony IOL which is an extended range of vision IOL (Abbott Medical Optics, Inc.).
This prospective, single centre study was approved by the hospital ethics committee of Nethradhama Superspeciality Eye hospital and performed in accordance with the principles of the Declaration of Helsinki. All patients provided written informed consent.
Inclusion criteria were healthy eyes besides senile cataract, corneal astigmatism equal to or less than 0.75 diopters (D), IOL power calculation resulting in diopters between +10.00 D to +32.00 D,in capsular bag IOL implantation and ability to read English language fluently.
Exclusion criteria were patients with corneal astigmatism of more than 0.75 D, irregular astigmatism, corneal dystrophy, tear-film or pupillary abnormalities, history of glaucoma or intraocular inflammation, macular disease or retinopathy, neuro-ophthalmic diseases and intraoperative or postoperative complications.
Preoperative assessment
Preoperatively, all patients underwent a complete ophthalmologic examination including uncorrected distance visual acuity(UDVA), corrected distance visual acuity (CDVA), uncorrected near visual acuity (UNVA), distance-corrected near visual acuity (DCNVA )at 40 cm (all measured using logMAR acuity charts under photopic conditions at 85 candelas [cd]/m2), manifest refraction, slit lamp biomicroscopy, non-contact tonometry, and dilated fundus examination.
Preoperative evaluation
Axial length was measured with the IOL Master 700 (Carl Zeiss Meditec, Jena, Germany) and IOL spherical power was calculated using the SRK-T formula.
Dominance of the eye was tested using the shooting / camera test. In all patients, dominant eye was targeted at emmetropia and the non- dominant eye was targeted at a myopia of -0.75D.
Postoperative follow-up examinations were performed the day after surgery and at 1 and 3 months after surgery. The anterior segment and the intraocular pressure were evaluated the day after surgery. The following tests were performed at the other two postoperative visits: measurement of monocular and binocular UDVA and CDVA, monocular and binocular uncorrected near visual acuity (UNVA) measured at 40 cm, monocular and binocular uncorrected intermediate visual acuity (UIVA) measured at 60cm, contrast sensitivity testing (F.A.C.T. STEREO OPTICAL CO., INC. Chicago) under photopic conditions (85 cd/m2) , and measurement of monocular and binocular defocus curves. Monocular and binocular defocus curves were done with best distance correction. Different levels of defocus were introduced in 0.50 D steps from +2.50 to -2.50 D.
Reading performance was evaluated using the Salzburg Reading Desk (University Eye Clinic, Paracelsus Medical University of Salzburg, Austria) which provides for controlled reading distance, and automated calculation of the reading speed and Logarithmic reading acuity. Postoperative follow up from one month onwards, reading acuity, reading speed (speed associated with maximum reading acuity), and the smallest print size that could be read with a minimum reading speed of 80 words per minute (wpm), which represents the lower limit for recreational sense-capturing reading were evaluated. All measurements of reading performance were performed with and without distance correction.
Concerning the ocular optical quality, the following variables were evaluated with the iTrace aberrometery(Tracey Technologies, Houston, TX) : modulation transfer function cut-off point, which represents the maximal spatial frequency (cycles per degree [cpd]) that can be resolved by the ocular optical system (theoretically in relation to visual acuity, assuming a good macular and neuroprocessing function), Strehl ratio, which is defined as the ratio of the peak of the eye’s image intensity from a point source compared to the maximum attainable intensity for an ideal eye limited only by diffraction (ranging from 0 to 1).
IOL
The Tecnis Symfony IOL is an extended range of vision lens based on diffractive achromatic technology. The lens has a biconvex wavefront-designed anterior aspheric surface and a posterior achromatic diffractive surface. The total diameter of the IOL is 13 mm and the optic zone diameter is 6 mm. It is made of an ultraviolet-blocking hydrophobic acrylic material, with a refractive index of 1.47 at 35°C. The lens is currently available in powers from +5.00 to +34.00 D in 0.50-D increments.
Surgical technique
All surgeries were performed by a single experienced refractive surgeon(S.G.), using a standard phacoemulsification technique under topical anesthesia. The IOLs were inserted into the capsular bag using the UNFOLDER Platinum 1 Series Screw-Style Inserter (Abbott Medical Optics, Inc.) through the main incision. Postoperative topical therapy included topical Prednisolone(Predforte), Moxifloxacin(Vigamox) and nepafenac(Nevanac).
Statistical Analysis: SPSS software for Windows version 17.0.0 (IBM Corp., Armonk, NY) was used for statistical analysis.Normality of data samples was evaluated by the Kolmogorov–Smirnov test. When parametric analysis was possible, the Student’s t test for paired data was used, whereas the Wilcoxon signed ranks test and Mann–Whitney test was applied to assess the significance of such differences when parametric analysis was not possible. All values were expressed as mean ± standard deviation (SD). A p-value of 0.05 or less was considered statistically significant.
Results
Table 1 shows preoperative and demographic data of all the eyes(n=50) included in the study. A total of 25 patients with mean age of 60.76±10.74 years, undergoing bilateral Tecnis Symfony implantation were recruited in the study. Since micromonovision was performed, the post-operative visual outcomes and reading performance was evaluated binocularly.
Distance Visual Acuity and Refraction
Figure 1 shows the cumulative percentage of eyes with LogMAR UDVA and CDVA, 6 months after the surgery. 80 % patients (20/25) had binocular UDVA of ≤0 logMAR .The UDVA was ≤0.1 logMAR in all 25 (100%) patients. All eyes achieved ≤0 logMAR CDVA.The binocular CDVA, however was significantly better compared to UDVA(p=0.007). Postoperatively, the UDVA and CDVA did not change significantly between 1 week, 1 month and 6 months (p-values >0.05 for all post op visits compared to 1 week), (Table 2).
At 6 months, the binocular UNVA at 40 cm was ≤0.3 logMAR in all 25 (100%)patients with a mean UNVA of 0.157 ±0.11 (Fig 1). There was a significant improvement in binocular UNVA at the last follow-up compared to one week(p=0.05).However, the binocular DCNVA was significantly worse compared to UNVA ,(p=0.05).
In the intermediate range, the UCIVA at 80 cm measured with ETDRS chart was significantly better compared to 60 cm at all post op visits (p-value<0.05)(Table 3). At 6 months, the UCIVA showed a statistically significant improvement at both distances compared to 1 week (p-values= 0.02 for 60 cm and 0.05 for 80 cm). However, the DCIVA was significantly worse compared to UCIVA for both distances(p<0.05)(Table2).
Reading Acuity and Reading speeds
Binocular UCRA ,DCRA, UCRS and DCRS showed improvement from one week through 6 months post-operatively for all distances ,the improvement being statistically significantly better for UCRA at 40 cm at the last visit (Table 4). In general, the binocular DCRA and DCRS for all distances were worse compared to uncorrected values at all visits, the DCRA being significantly worse compared to UCRA at 40 cm at the last follow-up,(Table 4) . Binocular intermediate UCRA , DCRA, UCRS and DCRS were comparable at both 60 and 80 cm, with no statistically significant differences between the values of these parameters at all post-op visits,(Table 3).
Stability of SE refraction over time
Post-operatively at one week, for both dominant and non-dominant eyes, there was a statistically significant reduction in SE after surgery compared to pre-operative SE.(P<0.05) (Table 5).The values of mean SE in the dominant and non-dominant eye at 1 week were -0.25± 0.32 D and -0.75±0.37D, which slightly reduced to -0.22±0.37 D and -0.74±0.44D respectively, at the end of 6 months. However, there were no statistically significant differences in spherical equivalent between 1 week through 6 months postoperatively (P>0.05).(Fig 2).
Defocus Curves
Fig 3 shows the binocular uncorrected and distance corrected defocus curves under photopic conditions. The uncorrected defocus curve showed visual acuity of 0 log MAR or better between the defocus range of -1.5 to 0 D, with a distinct peak observed at -0.5 D. However, throughout the defocus range of -2.5 to +1 D, the visual acuity remained 0.2 logMAR or better. The distance corrected defocus curve also showed a peak at -0.5 D, which coincided with the peak of uncorrected defocus curve.The uncorrected defocus curve at the defocus of -2.5,-2,-1.5 and -1D, was significantly better compared to distance corrected, with no significant difference in the mean visual acuity at subsequent levels of defocus beyond -0.5D
We also compared the defocus curves of dominant and non-dominant eyes uniocularly at the last visit. The UCVA in the non-dominant eye was better than dominant eye from -2.50 to -1.50 D and was significantly better at -2.5D defocus . However beyond the defocus of -1.50D, the dominant eye showed better UCVA which was significantly better for the defocus range of 0 to 1 D(p=0.00) (Fig 3) Although the non-dominant eye was aimed for -0.75 D myopia,the mean UCVA in these eyes was 0.2 logMAR or better through a defocus range from -2.5 to 0.5D.
Contrast Sensitivity
Fig 4 shows the binocular distance corrected contrast sensitivity under photopic conditions at 1 week and 6 months post operatively. At 1 week contrast sensitivity was within the normal range and a significant improvement at 6 months was observed especially for higher sptatial frequencies.(Table 6)
Dysphotopic Phenomena and Spectacle Independence Evaluation
At the end of 6 months, 36%(9/25 ) patients did not complain of dysphotopsia, while the rest 64% (16/25) patients complained of dysphotopsia varying from mild to severe. For both distance and intermediate range activities such as watching TV and computer respectively, 96% ( 24/25) patients were highly satisfied and spectacle free. However, for near vision this number was 64%(16/25) and 16%(4/25) patients were using glasses for reading fine print(Fig 5).
Table shows the results of the subjective questionnaire.
Long term complications
No visually significant complications such as posterior capsular opacification, cystoid macular oedema, post op uveitis or glaucoma occurred in any of the eyes at the end of 6 months follow-up.
Discussion
Recently, Peddar et al have compared the outcomes of Tecnis Symfony IOL with Tecnis monofocal IOL, and concluded that the extended range of vision IOL provided
better distance, intermediate, and near visual acuity than the aspheric monofocal IOL, while maintaining the same level of visual quality(ref).However, both eyes were targeted for emmetropia in their study and no micromonovision was performed.
Comparing our results with the binocular outcomes reported by Peddar et al, we observed (Table 7)
In our study, the binocular distance corrected near and intermediate visual acuities were found to be worse compared to the uncorrected values at all post-operative visits. This was due to the reason that the post-operative refractive error was slightly myopic in the dominant eyes and more myopic in the non dominant eye( due to micromonovision), hence when corrected for distance , an expected deterioration in near and intermediate visual acuities was observed.
Reading performance was assessed using the SRD, which is designed to simultaneously measure reading acuity and speed. Many studies have evaluated reading performance with various multifocal IOLs using SRD . We also observed constant improvement in the uncorrected reading acuity and reading speed over time for all distances, both being highest at the end of 6 months. This can partially be attributed to neural adaptation process and the learning curve effect that occurs when patients take the same test again.
Although the uncorrected near visual acuity and reading performance at 40 cm showed significant improvement over time, patient satisfaction was least for near compared to distance and intermediate range activities. This may suggest that micro-monovision may not be a perfect strategy for enhancing near vision with this intraocular lens. Alternatively, as shown by et al, it may be possible that the near focal point of the multifocal IOL may change depending upon the preoperative anterior chamber depth and keratometery. It was proposed that caution must be exercised while using MFIOLs with low add especially in patients with large anterior chamber depth . This point, however, needs further justification.
Nevertheless, to our knowledge, this is the first report on the outcomes of Extended range of vision IOLs with micromonovision. Preliminary results suggest that micromonovision with this IOL was well tolerated and lead to satisfactory outcomes for most activities at all distances. However, further research is required to verify these results. Future studies comparing the outcomes of micromonovision with the extended range of vision lens and low add multifocal IOLs is suggested to evaluate their performance and patient satisfaction.
Legends:
Figure 1- Cummulative binocular visual results
Figure 2- Stability of SE
Figure 3- Binocular and uniocular defocus curve
Figure 4 – Contrast sensitivity over time
Figure 5- Patient satisfaction
Table 1 – Binocular corrected and uncorrected visual results
Table 2- Comparison of Intermediate visual performance at 60cm and 80cm
Table 3- Binocular Reading acuity and Reading Speeds
Table 4 – Refractive outcomes
Table 5 – Contrast sensitivity
Table 6- Comparison of binocular visual results