Dr.Gitansha Sachdev, S15438, Dr. Ramamurthy D
Cataracts are a major public health issue, especially in developing countries.1Approximately 39 million people are blind worldwide.2According to a 2004 World Health Organization report, 47.8% of blindness worldwide is due to cataract.3 Of the disability-adjusted life years due to cataract more than 90% are in the developing world.4 Cost of surgery and lack of awareness are the most commonly cited barriers to patients obtaining surgery in developing countries Cataract surgery has become the most commonly performed intraocular procedure, with constantly improving outcomes. The intra-capsular technique had been popular until the early 1980s. Planned extra-capsular cataract extraction gradually became more widespread; it was then further refined by phacoemulsification.5
Methods to increase accuracy and precision in cataract surgery are being investigated because, as lens implants become more advanced, patient expectations for near-perfect vision are increasing. The premium intraocular lenses (IOLs) also depend more on precise centration for optimal performance. The new femtosecond laser systems usher in the future of cataract surgery and bring us one step closer to an ideal surgery that corrects cataract and astigmatism.
The introduction of femtosecond laser to the field of cataract surgery offers many potential benefits. Although evidence in support of its efficacy is accumulating, there is a surgical learning curve that needs to be addressed.
Femtosecond lasers produce a more accurate and precise anterior capsulotomy, improve intraocular lens centration and reduced intraocular lens tilt. Visual and refractive outcomes, although in limited number of studies, have been shown to be at least as good as conventional phacoemulsification. The impact of reduced phacoemulsification energy on the corneal endothelium is still being investigated
The femtosecond laser is able to perform three important steps in cataract surgery: capsulotomy, lens fragmentation and corneal incisions.
In addition to creating the main cataract surgical wound, femtosecond lasers are used to create limbal relaxing incisions (LRIs). When placed in specific areas of the cornea, LRIs can reduce the amount of astigmatism present, which can, and often does, improve post-operative uncorrected visual acuity. Typically, corneal incisions to control astigmatism have been performed by hand held blades. The major factors determining LRI effectiveness are the incision length, depth, and uniformity, the location relative to the center of thecornea, the incision geometry, the patient’s age, and the amount of astigmatism. The precision of the laser created incisions should allow the surgeon greater control over the final refractive endpoint possibly leading to improved visual outcomes.
AIMS AND OBJECTIVES
Does femtosecond laser assisted cataract surgery improve visual performance and patient satisfaction?
Visual acuity – To assess the visual outcomes with laser refractive cataract surgery.
To measure other parameters affecting visual performance such as Contrast sensitivity and Residual refractive error. To assess the effect of femtosecond laser assisted cataract surgery on Endothelial cell count, Intra operative and Post operative complications and Overall Patient satisfaction.
MATERIAL & METHODS
Prospective longitudinal single center before and after descriptive study.
55 eyes of 33 patients who satisfied the selection criteria of the study, were recruited and underwent femtosecond laser assisted cataract surgery. These patients had a femtosecond laser assisted procedure performed first, followed by removal of lens matter by phacoemulsification and implantation of PCIOL. They were recruited over a period of 8 months.
Place of study:
The Eye Foundation, Post-graduate Institute of Ophthalmology, Coimbatore.
The study was carried out over a period of 9 months (July 2015 to March 2016). Recruitment from July 2015 to Feb 2016 and follow up for 6 weeks.
Material used: The LenSxR Laser is a CDRH CFR 1040 class 4 and an IEC
60825-1 class 4 laser system for ocular surgery consisting of the following components:
1.A laser source to produce femtosecond laser pulses;
2.An aiming device to localize specific targets in the eye;
3.An optical delivery system to precisely deliver laser pulses to desired targets in the eye.
4.Computer controllers to perform clinical procedures;
5.A disposable patient interface optically coupling the eye tothe optical delivery system in order to hold the eye.
1.Age of the patient – 15 years and above (compliant for surgery under local anesthesia)
2.Patients with reduction in visual acuity primarily due to cataract.
3.Availability,willingnessandsufficientcognitiveawarenesstocomplywith examination and undergo the procedure.
1.Cataracts due to secondary causes
2.Poor patient mobility, inability to lie flat
3.Poorly dilating pupils,corectopia
5.Missed follow up
8.Phacodonesis / zonular dialysis
10.Ocular surface disorders
11.History of uveitis
13.Vision hampering retinal or macular pathology
14.Optic Atrophy, Neuropathies
16.One eyed patients
The study protocol and consent form were approved by the Institutional ethical committee of THE EYE FOUNDATION, Coimbatore. All patients fulfilling the study selection criteria as given above were selected for the study. Patients were recruited from July 2014 to February 2015 and followed up for 6 weeks postoperatively. Following recruitmentand after getting valid informed consent, the participants were subjected to a series of pre operative investigations, after which they underwent a femtosecond laser procedure followed by removal of lens matter by phacoemulsification and in-the-bag implantation of the Posterior Chamber Intra Ocular Lens. Postoperatively they were subjected to a series of investigations to assess their visual performance on day 1, week 1 and at 6 weeks. Endothelial cell count (at 1 and 6 weeks) and K- reading (at 6 weeks) were measured. A note of intra and post operative complications (if any) were made at each visit. The pre operative & post operative results were compared.
The overall satisfaction of the participants was assessed through a quality of life questionnaire (at 6weeks follow up visit)
The subjects underwent the following pre-operative evaluation:
2.Slit lamp examination
5.Spectral Domain Ocular Coherence Tomography :
OCT using Cirrus HD-OCT system Model 4000 SW version 22.214.171.124, Carl Zeiss MeditecInc, Dublin ,CA was done pre-operatively to ascertain a normal macular status.
6.Specular microscopy using a non-contact specular microscope (EM 3000, TOMY ) with the cell count imaging system.
7.K- READING : Manual K reading K1 and K2 were obtained with the BAUSH AND LOMB
keratometer and was measured pre operatively and at 6 weeks post operatively. The relative change in the corneal curvature following the procedure was compared
BIOGRAPH (Wavelight ALLEGRO) and immersion biometry was used for all the patients to determine the axial length. The IOL’s were selected according to the patients’ preference. All three available third-generation IOL formulas (SRK/T, Hoffer Q, and Holladay 1) and optimized IOL constants were used for IOL calculation.
The corneal topography was assessed with WAVELIGHT OCULYSER II pre operatively. The pre-operative keratometric readings and amount of astigmatism were reconfirmed, as they are the key factors in planning the femtosecond laser assisted corneal arcuate keratotomy incisions.
Measured with Bausch and Lomb F.A.C.T chart pre-operatively and at 1 and 6 weeks post operatively.
Post-op medication: Prednisolone acetate eye drops tapered over a period of 8 weeks; eye drops Ketorolac with ofloxacin combination for 1 week; Bromfenac eye drops for 5 weeks.
Patients were then followed up on the 1stday and at the end of 1stweek, and 6thweek post-operatively and the following parameters were assessed:
At 1ST day post-operatively:
- Uncorrected Visual Acuity ( UCVA)
- Best Corrected Visual Acuity (BCVA)
- Anterior segment examinations with slit lamp .Any evidence of
immediate post operative complications were noted.
At 1 week post-operatively:
- Specular microscopy
- Contrast sensitivity
- Complications (if any) were noted
At 6weeks post-operatively:
- Specular microscopy
- Contrast sensitivity
- K- reading
- Quality of life questionnaire
- Complications (if any) were noted.
The femtosecond laser assisted cataract surgery requires the use of highly sophisticated machinery and is a financially demanding procedure, which cannot be afforded by all. Our hospital is a tertiary care centre performing an average of 180 FLACS cases per year. Affordable patients who presented to us from July 2014 to February 2015 with diminished vision primarily due to cataract and satisfying the inclusion and exclusion criteria were enrolled in our study after obtaining informed consent.
Thus 55 eyes were recruited for the study.
Using the sample size determination for a descriptive study of a continuous variable parameters are taken as follows: standardised width of the confidence interval (w/s) = 0.70 and with 99% confidence interval, the sample size required is 55
The data was collected and entered onto the Microsoft excel 2007 spread sheet. Statistical analysis was performed by the statistical software SPSS version 21.0. Continuous variables are represented as ‘Mean (SD)’, and categorical variables are represented as ‘Frequency (percentage)’. Comparison of mean was done using the Paired‘t’ test. P <0.05 was considered as statistically significant.
OBSERVATIONS AND RESULTS
Table-1: Gender Distribution in the study population:
|Gender||Number of eyes||Percent|
The percentage of males in the study population was 66.7 % and the percentage of females in the study population was 33.3 %.
Table-2: Age-wise distribution of the study population:
|AGE GROUP||NO. OF EYES||PERCENTAGE|
The age wise distribution shows 45.5% of patients between the age group 61-70 years and 40% between the ages of 51- 60 years, with a mean of 55.45 ± 8.05 years (range 40 to 73 years)
Table-3: Grouping of the study population based on laterality:
|Laterality||No. of subjects||Percentage (%)|
The percentage of study population with right eye surgery was 50.91% and with left eye surgery was 49.09 %
Table-4: Grouping of the study population based on the nature of cataract:
|Type of cataract||No of eyes||Percentage|
Majority of the study eyes, 87.2% had immature cataracts with 5.4 % having posterior polar cataract. Brown and mature cataracts were seen in 3.6% of the eyes each.
Table-5: Grouping of the study population based on the type of IOL
|Type of IOL||Number of eyes||Percentage|
|Aspheric single piece||27||49|
Among the IOLs, a majority of the eyes were implanted with Aspheric Single piece IOL (49%) and the Restor Multifocal IOL (45.4%).A small percentage (5.4%), had a ToricMonofocal lens implanted
Thus a majority of the post operative UCVA was in the 6/7.5-6/9 range. A significant number of eyes were found to have an unaided vision of 6/6 when compared to none pre-operatively
Grouping of study population on the basis of their (UCVA) – represented in logMAR
|UNCORRECTED VISUAL ACUITY||MEAN IN LOGMAR||SD|
The mean pre-operative UCVA was 0.50 ± 0.39 (represented in logMAR) which reduced to 0.22 ± 0.18 on the first day, 0.21 ± 0.14 at one week and to 0.17 ± 0.14 at 6 weeks (represented in logMAR).The mean pre-operative value was compared to the mean 6 weeks post-operatively, and was found to bestatistically significant (p value<0.05) There was a progressive improvement in UCVA in patients after FLACS on subsequent post-operative visits.
Grouping of study population on the basis of their BCVA
Thus significant number of eyes (50), were found with a post-operative BCVA of 6/6 when compared to 13 eyes pre-operatively. The BCVA was seen to improve progressively with no one <6/7.5at 6 weeks.
OUTCOMES BASED ON RESIDUAL SPHERE
Six weeks post –operatively, 40 eyes (72.7%) had no residual sphere, 4 eyes (7.27%) had a residual of 0.25D; 9 (16.36%) had
0.50D ; 1 eye(1.81%) had 0.75D and 1 eye (1.81%) continued to have a residual of 1D. (Table 11 and Graph 17).
Thus a large number of eyes, 72.75% had no residual sphere at 6 weeks.23.63% of the eyes had a residual sphere within 0.50D
MEAN RESIDUAL CYLINDER
6 weeks post –operatively, 50 eyes (90.92%) had a minimal cylinder of ≤ 0.5D;2 eyes (3.63%) had residual cylinder between 0.75D – 1.25D and 3eyes(5.45%) ≥1.5D(Table 13 and Graph 19).The calculated SIA was 0.4D.The mean pre operative cylinder was compared with the mean at 6 weeks post operatively, and was found to be statistically significant ( p <0.05)
MEAN RESIDUAL SPHERICAL EQUIVALENT
The mean pre-operative spherical equivalent was -0.067±1.81 with a range of (-4.25 to +3.5).At one week it was -0.353 ± 0.36 with a range of (-1.25 to +0.37) and at 6 weeks it was -0.385 ± 0.322 with a range of (-1.25 to 0).(Table 14)
There was a marked reduction in the range of the spherical equivalent at 6 weeks post operatively compared to the pre operative values.
ENDOTHELIAL CELL COUNT
The pre – operative mean endothelial cell count was 2516±208.23;at one week post op it was 2193±423.62 and at six weeks post op it was 2244±385.53 On comparing the preoperative and post operative values we found the difference to be statistically significant, p< 0.05 (Table 15 and Graph 20)
There was an improvement in contrast sensitivity, evidenced by a progressive reduction in mean form 0.281 pre-operatively to 0.036 at one week and 0.027 at 6 weeks post-operatively. (Table 16 and Graph 21).The pre operative and post operative values were compared, and found to be statistically significant (p<0.05)
Intra operatively 4 eyes (7.27%) had a sub-conjunctival haemorrhage when the docking procedure was repeated; 1eye (1.81%) had a posterior capsular rent; the remaining 50 eyes (89.09%) had no intra-operative complications.
Post operatively, on the first day,7 eyes (10.91%) had descemet membrane folds; 2 eyes (3.64%) had striate keratopathy and 1 eye (1.81%) had corneal edema. However, they were found to resolve by the end of one week.
QUESTIONNAIRE: RESPONSE FROM PATIENTS WHO CHOSE MULTIFOCAL IOL
QUESTIONNAIRE: RESPONSE FROM PATIENTS WHO CHOSE OTHER IOL
When presented with a questionnaire on the 6thpost operative week we received a positive response from most of the patients who had chosen a multifocal IOL. (Table 20 and Graph 25)Among the patients with other IOLs (i.e single piece and toric), few patients had difficulty in performing near tasks without their presbyopic correction. (Table 21 and Graph 26)
However, 31/33 (94%) of the patients were satisfied with the overall outcome, while 2 patients (6 %) were not totally satisfied.
This was a prospective longitudinal single center before and after descriptive study conducted at The Eye Foundation and Post-graduate Institute of Ophthalmology, Coimbatore, South India to analyse the outcomes of Laser Refractive Cataract Surgery in a hospital based Indian population. A total of 55 eyes of 33 patients underwent FLACS, satisfying the study selection criteria. These patients were recruited in our study over a period of 8 months (from July 2014 to February 2015) and followed up for 6 weeks.
Pre-operatively, determination of UCVA, BCVA, slit lamp examination, IOP with applanation tonometry, Indirect Ophthalmoscopy, Ocular Coherence Tomography, specular microscopy, manual K-reading, A-scan, contrast sensitivity and corneal topography were done in all patients. The patients underwent an initial procedure under the femtosecond laser in a separate room after which routine phacoemulsification was performed.
Patients were followed up post-operatively on the 1stday, 1stweek, and at 6weeks. On the 1stday UCVA and BCVA were measured. At one week UCVA, BCVA, contrast sensitivity and specular microscopy were done and at 6 weeks, along with these investigations, manual k reading was also done. The patient satisfaction was assessed through a quality of life questionnaire at 6 weeks. At each visit a note of any post operative complications was made.
This study analyzed the various outcomes of femtosecond laser assisted cataract surgery. A majority of the patients had immature cataracts (87.2%) Aspheric single piece (49%) and multifocal IOL (45.4%) were the most commonly IOLs. Pre-operatively, 13 eyes (23.64%) had 6/7.5-6/9;20 eyes (36.36%) between 6/12- 6/18; 12 eyes (21.82%) between 6/24-6/60 and 10 (18.18%) less than 6/60.
At 6 weeks post op 15 eyes (27.27%) had a UCVA of 6/6; 26 eyes (47.27%) had 6/7.5-6.9 and 14 eyes (25.45%) between 6/12 – 6/18. A majority of the post operative UCVA was in the 6/7.5-6/9 range, with no eyes having < 6/18. The post-operative mean logMAR values showed a significant decrease (0.17±0.14) compared to the pre-op values (0.50±0.39) suggesting a statistically significant improvement in vision.(p<0.05)
Pre-operatively, 13 eyes (23.64%) had a BCVA of 6/6, 20 eyes (36.36%) 6/7.5-6/9; 12eyes (21.82%) between 6/12- 6/18; 5 eyes(9.09%) between 6/24- 6/60 and 5 (9.09%) less than 6/6. At six weeks, 90.91% ( 50 eyes) had a BCVA of 6/6 and the remaining 5 eyes had 6/7.5 pre-operatively. The BCVA was seen to improve progressively with each visit, with no one <6/7.5 at 6 weeks. The mean value of pre-operative BCVA was 0.27 ± 0.34 which reduced to 0.01 ± 0.03 at 6 weeks (represented in logMAR).Thus, there was a statistically significant improvement in post operative BVCA when compared to the pre operative values.(p<0.05)
At six weeks 72.75% (40 eyes) had no residual sphere, 23.63% (13 eyes) had a residual sphere within 0.50D, with no one having a sphere of more than 1D at the final visit.
Pre –operatively, (based on manual k-reading ) 37 eyes (67.27%) had an astigmatism of ≤ 0.5D; 14 eyes (25.45%) between 0.75D-1.25D and 4 eyes (7.27%) ≥ 1.5D. 6 weeks post –operatively, 50 eyes (90.92%) had ≤ 0.5D; 2 eyes (3.63%) had a residual astigmatism between 0.75D – 1.25D and 3 eyes(5.45%) had ≥1.5D.The calculated SIA was 0.4D.The FSL created arcuate keratotomy incisions were found to be highly effective in those patients who had a pre-operative astigmatism ranging from 0.75 – 1.25D. The mean pre operative cylinder 0.51±0.52 (range 0.25-3.00) was compared with the mean 6 weeks post operatively 0.31±0.36 (range 0.00 – 1.25)., and was found to be statistically significant (p <0.05)
The range of the spherical equivalent reduced from (-4.25 to +3.5 ) to (-1.25 to 0) at 6 weeks post operatively.
The pre – operative mean endothelial cell count was 2516±208.23 and at six weeks post op it was 2244±385.53. We found the difference to be statistically significant p< 0.05, however the change in mean was small.
Contrast sensitivity was found to improve, evidenced by a progressive reduction in mean from 0.280 pre-operatively to 0.027 at 6 weeks post-operatively, which was statistically significant.(p<0.05)
The most common intraoperative complication encountered in our study was sub-conjunctival haemorrhage seen in 4 eyes (7.27%) which occurred when the docking procedure was repeated more than once. It did not have any impact on the final visual outcome. Post operatively the most common complication was DMF (10.91%), which resolved within a week of surgery. 90.91% of the patients in our study did not have any intra operative complications and 81.82% were free of post operative complications. When presented with a quality of life questionnaire on the 6thpost operative week, 94% of the patients were satisfied with the overall outcome.
Thus, from the analysis of our study we report good visual outcomes with minimal residual refraction, increased contrast sensitivity, a low complication rate and a high level of patient satisfaction.
The Femtosecond Laser Assisted Cataract Surgery is a viable option for cataract surgery over routine phacoemulsification. The post-operative UCVA and BCVA was better than the pre-operative values in majority of patients. Almost all the patients achieved a final visual acuity of 6/6, with a minimal residual refractive error, with significant reduction in keratometric astigmatism, with increase in contrast sensitivity, a low complication rate and a high level of overall patient satisfaction.
The major advantages of FLACS are its precise clear corneal incisions, accurate and reliable LRI’s, reproducible and predictable capsulotomies and fragmentation of the lens nucleus.The rate of intra-operative and post-operative complications are also low.
Hence FLACS provides good visual outcomes with a low complication rate for a wide range of cataracts.It is safe and effective. However, the high cost proves to be a barrier to effectively introduce this technology to patients on a larger scale in our country. More long-term studies on FLACS need to be performed to determine the impact of femtosecond lasers on a long term basis.
LIMITATIONS OF THE STUDY
3.This study was conducted in a single centre and should be conducted as a multi- centric study.
4. Further, a study with a larger sample size would have been more beneficial to assess the outcomes of FLACS.
5. Our follow-up period was short, a longer follow up period is required to analyse the long term outcome of FLACS.
6. Our study did not do a comparative analysis of FLACS with routine phacoemulsification, which is necessary to establish the clinical superiority of FLACS over routine phacoemulsification.
7. As the selection of the IOL was determined by the patient, uniformity could not be maintained
8. The surgeries in this study have been done by multiple surgeons and it would help to analyse the results of a single surgeon.
- Femtosecond Laser Assisted Cataract Surgery is a viable option in terms of good visual outcomes and low rate of intra-operative and post- operative complications.
- FSL created arcuate incisions are effective in reducing astigmatism in the range of 0.75D-1.25D
- FLACS can be considered for various grades of cataract
- The financial considerations should be borne in mind before transitioning to the femtosecond laser assisted cataract surgery.
- A randomised comparative analysis of FLACS with routine phacoemulsification is required in-order to compare the results.
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