FP1039 : Outcomes of Coaxial Microincision Cataract Surgery Versus Conventional Phacoemulsification Surgery

Dr.Anu Malik, M12959, Dr. Yogesh Kumar,

Dr. Alka Gupta

INTRODUCTION

Cataract is the main cause of curable blindness worldwide, with developing world accounting for approximately three fourth of this blindness.1,2  Cataract has been  reported  to be responsible for 50-80% of  bilaterally  blind in India. There are 100 million eyes with cataract causing vision of <6/60 and number is increasing because of population growth and increasing life expectancy.3

In 1967, the introduction of phacoemulsification by Kelman represented the beginning of a revolution in cataract surgery that made it possible to abandon more invasive procedures.4 In particular, incision size decreased from 10.0 mm required for the intracapsular cataract extraction to 7.0 mm for extra capsular cataract extraction and ultimately to the small incisions (3.2 to 2.8mm) used for phacoemulsification.4,5

Micro incision cataract surgery (MICS) was described first time by one of the authors named Jorge Alio in 2002 in Spain, as a new concept of cataract surgery based on bimanuality, new tools, fluidics and new concept of surgery technique.6

Agarwal et al. and Tsuneoka et al. described in parallel this surgical approach to cataract surgery with other denominations such as Phaconit or bimanual phacoemulsification-aspiration.7,8.

Microincision cataract surgery was originally developed as a biannual technique, which had many disadvantages, including a steep learning curve, anterior chamber instability due to leakage through 2 incision sites, and limitation in infusion due to small instruments. 9

In addition, mechanical wound trauma can occur secondary to the angular movement of the instruments through the tight incision sites.9 To overcome these problems, micro coaxial cataract surgery was developed. The main advantage of the new technique is that it uses the same methods as conventional method, but with smaller incisions; thus, learning curve is less steep.10,11

Microincision cataract surgery has many advantages. It reduces surgically induced astigmatism (SIA), intraoperative and postoperative inflammation, and the time required for visual function.12,13 In addition, because MICS requires a smaller wound and decreased tissue healing, the possibility of postoperative  leakage and endophthalmitis is also decreased.14

AIMS AND OBJECTIVES

1. To compare the surgical parameters of coaxial microincision cataract surgery with the standard phacoemulsification surgery.
2. To assess and compare the relation of visual outcome and surgically induced astigmatism of the two surgical techniques.

MATERIALS AND METHODS

The prospective, randomized interventional study was conducted on 60 patients having significant cataract. The patients were selected from the outpatient department of Ophthalmology Department, Hindu Rao Hospital, Delhi. Informed consent was taken from the patient for participating in the study. The patients were randomized in two groups of 30 patients each.

Group 1(30 eyes) – Standard phacoemulsification.

Group 2(30 eyes) -Coaxial Microincision Cataract Surgery (coaxial MICS).

Inclusion criteria: Age-  >40yrs, Sex-  either sex, uncomplicated senile cataract with nuclear sclerosis of grade II and III, preoperative astigmatism of 1.5 dioptre or less, Consent and willingness for follow up

Exclusion criteria: Patients having lid abnormalities (ectropion, entropion, lagophthalmos, trichiasis), poor tear film status, active inflammation, lacrimal sac disorder, preoperative astigmatism, more than 1.5 diopter cylinder, corneal   opacity, dystrophy or any other pathology, subluxated lens or zonular dehiscence, hypermature senile cataract, nuclear sclerosis more than grade IV and traumatic cataract, preoperative mydriasis less than 5 mm, any evidence of glaucoma, uveitis, or retinopathy, patients having systemic illness like diabetes mellitus, hypertension, or tuberculosis

A detailed history of patients was taken and history of Diabetes mellitus, Hypertension or Coronary artery disease or any other systemic illness was elicited, allergies to medications such as antibiotics, systemic medications, and anaesthetics, Ofdrug intake like aspirin, NSAIDS, and other medications that interfere with blood coagulability.

Uncorrected visual acuity (UCVA) was estimated using standardized Snellen chart or ‘E’ chart.

Slit lamp grading of nuclear sclerosis was done using Lens Opacities Classification System III (LOCS III),             Fundoscopy to rule out any posterior segment pathology, Intra ocular pressure was measured using Applanation tonometer, Syringing was done to check the patency of nasolacrimal system, keratometry by using Bausch and Lomb keratometer. Estimation of axial length and IOL power by using ultrasonic biometer.

Surgical procedure:

An informed consent was taken from the patient. All operations were performed by a single surgeon. The Oertli System and coaxial MICS phaco tip and sleeve from the same manufacturer were used for phacoemulsification.

Group 1 – Standard phacoemulsification (i.e. phaco tip with sleeve) through a 3.2 mm clear corneal incision was performed using stop and chop nucleotomy technique. A flexible hydrophilic acrylic IOL with optics 5.5 mm was then implanted using injector system after inflating the capsular bag with viscoelastic.

Group 2 – Coaxial microincision cataract surgery (i.e. a sleeved thinner phaco tip) through the incision of 1.8 mm was performed using stop and chop nucleotomy technique. A flexible hydrophilic acrylic IOL with optics of 5.5 mm was then inserted with an injector system after inflating the capsular bag with viscoelastic.

Intraoperative operations:

Following intraoperative parameters was assessed for all patients:

• Effective phacoemulsification time.
• Mean Total phacoemulsification percent.
• Total Balanced Salt Solution (BSS) volume (initial volume in infusion bottle minus residual BSS volume).
• Intra operative complications like wound burns, hydration of wound, posterior capsule ruptures, IOL damage and IOL decentration.

Postoperatively patients in both groups received:Topical combined drops (Prednisolone acetate 1% and Gatifloxacin 0.3%) every 6 hours per day for 4 weeks, Topical lubricant (Carboxy Methyl Cellulose 0.5 times per day for 4 weeks, Topical NSAID drops (Ketorolac Tromethamine 0.5 %) 3 times per day for 4 weeks, Topical cycloplegics (Tropicamide 1%) twice a day for 2 weeks

All patients who had undergone surgery were regularly followed up. Their post operative visual acuity was recorded by means of Snellen’s chart.  Visual acuity and keratometry were assessed for all patients on day 1, 1st week, 2 weeks, 4weeks and 6 weeks post operatively. Retinoscopy was performed and trial lenses were attempted in order to achieve final visual acuity of 6/6 or at least 6/9. Surgically induced astigmatism was calculated by subtraction method.

Pre op K1 = Vertical meridian

K2 = Horizontal meridian

K1-K2 = K (Preoperative astigmatism)

Similarly post operative K1 and K2 will also be taken.

K1*(Post op) – K2* (Post op) = K* (Post operative astigmatism)

Surgically induced astigmatism was calculated by subtraction of pre operative astigmatism from post operative astigmatism without assigning any sign.

Surgically Induced Astigmatism (SIA)

= Pre op astigmatism (K) – Post operative astigmatism (k*)

OBSERVATION AND RESULT

Sixty eyes of 60 patients fulfilling the inclusion criteria attending the outpatients department of Hindu Rao Hospital were selected for our study. They were randomly divided into two groups. Thirty eyes underwent standard phacoemulsification and another 30 eyes of thirty patients underwent coaxial microincision cataract surgery.(WAS IT DONE BY SAME SURGEON?)

Group 1 :  Standard phacoemulsification (standard phaco)

Group 2  : Coaxial  Microincision cataract surgery (coaxial MICS)

The patients in two groups were followed up at 1st post-operative day, 1 week, 2 week, 4 week, 6 weeks post-operatively.

Age Distribution

Maximum numbers of patients were in the age group of 51-60 years whereas in group 2 the oldest patient was 72 years old and the youngest 45 years old.  Maximum numbers of patients were in the age group of 61-70 years. Mean age of the patients was 60.43 ± 7.03 years ( range 45-80 years) and the maximum number of patients were in the age group 51-60  years in group 1(standard phaco) and 61-70  years in group 2(coaxial MICS).

Sex Distribution

The distribution of males and females is illustrated in Table 3 and figure 2. There were 16 (53.3%) males and 14 (46.7%) females in group 1 and 11 (36.7%) males and 19 (63.3%) females in group two.

Grades of cataract

Distribution of various grades of cataract is shown in table 4 and figure three. (NO TABLES AND  FIGURE AVAILABLE) There were 13 (43.3%) patients of grade II and 17 (56.7%) patients of grade III cataract in each group.

Preoperative IOP

Preoperative Intra Ocular Pressure in Group 1 was 14.67 ± 2.19 mm Hg where as in Group 2 was 15 ± 2.02 mm Hg

Preoperative visual acuity

The majority of patients 12(40%) had visual acuity of 6/60 in group 1 whereas 13 cases (41.7%) of group 2 had vision 6/60 whereas 13.33% of cases in each group had vision <6/60.

It was seen that post operatively after 4 weeks, 80% i.e 24 of them had vision 6/6 and 20% of cases had vision 6/9 and remain same after 6 week follow up period.

(IN WHICH GROUP ?)

It was seen that pre (?)post(?) operatively 73.3% of cases had visual acuity 6/6 and 26.6% of cases had visual acuity 6/9 at 2 weeks, 4 weeks and 83.33% of cases had visual acuity 6/6  at  6 weeks  follow up period.

It was observed that there was no clinically significant difference in visual acuity both pre operatively and post operatively.

The mean K1 of group 1 was 44.22±1.29D whereas in group 2 it was 44.25±1.33D pre operatively. At 6 weeks post operatively it was 43.15±0.89D in group 1 and 43.66±1.37D in group 2 respectively .The difference in these two groups was not clinically significant.

The mean K2 of group 1 was 43.90±1.31D whereas in group 2 it was 43.86±1.31D pre operatively. At 6 weeks post operatively it was 43.77±0.81D in group 1 and 44.12±1.33D in group 2 respectively. The difference in these two groups was not clinically significant.

Surgically induced astigmatism (SIA)

It was observed that SIA changes gradually over the follow-up period of 6 weeks .The mean SIA was 0.54±0.37 in group 1(standard phaco) and 0.49±0.33 in group 2(coaxial MICS) preoperatively which changed to 1.20±0.76, 1.05±0.73, 0.70±0.31 in group 1 whereas it was changed to 0.82± 0.60, 0.62± 0.45, 0.58± 0.37 in group 2 at post op day 1, 1 week and 6 weeks respectively. The difference was significant in post day 1 and 1 week in both the groups. At 6 weeks the difference between these two groups was not clinically significant.

The mean total balanced salt solution used in group 1 was 128.83± 19.81 ml whereas in group 2 it was 139.33 ± 13.57 ml. The p value was 0.020 which was statistically significant.

The mean total phaco power used in group 1 was 35.77± 5.17% and in group 2 it was 33.70 ± 3.05%. The p value was 0.027 as there was a statistically significant difference found in two groups.

It was observed that the mean effective phaco time (EPT) in group 1 was 29.80 ± 3.67 seconds whereas in group 2 it was 31.93 ± 4.08 seconds. The(??)

DISCUSSION

We conducted a prospective randomized study in 60 eyes, which were randomly categorized to undergo either of the two surgeries. In this study phacoemulsification was performed with IOL implantation in patients having cataract with significantly poor vision. The surgery was performed with incision size 3.2 mm for standard phacoemulsification and 1.8 mm for coaxial Microincision Cataract Surgery and foldable IOL was implanted.

Thus sixty eyes were studied with a 6 weeks follow up. The various parameters that were assessed were UCVA, BCVA for distance, SIA, pre operatively and at day 1, 1 week, 2 weeks, 4 weeks, and 6 weeks postoperative follow up visits. Intraoperative parameters such as effective phacoemulsification time, total phacoemulsification percent, total balanced salt solution used and surgical complications like wound burn, IOL damage, IOL decentration, PC rupture, wound hydration were also studied.(THERE IS NO MENTION OF INTRAOP COMPLICATIONS IN THE RESULTS SECTION)

The data was collected and analyzed at the end of 6 weeks follow up using the “Student’s  t test” to compare the various parameters between the two groups and general linear model repeated measure analysis was used to know the trend over time.

The mean age of the patient in standard phaco group was 64.4±7.10 years and that for MICS was 58.8±6.96 years. There was no statistically significant difference in the age groups of both groups.

Lens Opacities Classification System (LOCS III) has been used in our study for grading of nuclear hardness. We selected cataracts from grades II to III and the cataract grades were similar in both the groups; the difference between groups was not statistically significant.

All the patients irrespective of their group showed significant improvement in visual acuity after surgery. The mean UCVA preoperatively was 0.88± 0.17 in the standard phacoemulsification group and 0.90±0.15 in the coaxial microincision phacoemulsification group. Postoperative day 1 the mean BCVA in the standard phacoemulsification group was 0.20±0.14 and 0.20±0.05 in the coaxial microincision phacoemulsification group. At the end of 6 weeks the mean BCVA was 0.04 ± 0.07 and 0.05 ± 0.08 in the standard phacoemulsification and the coaxial MICS groups respectively. In our study the difference between the groups was not statistically significant at any of the follow up visits (p>0.05).

In the standard phacoemulsification group 80% achieved a BCVA of 6/6 at 6 weeks and similarly 83.33% had BCVA of 6/6 in the coaxial microincision cataract surgery group.

Dossoet al10 in their study found no significant difference in postoperative best corrected visual acuity in coaxial MICS and conventional coaxial group.  Agarwal et al7 in their study described “phakonit” technique using Staar sub 2.0 mm clear corneal incision and implantation of  IOL. They also reported that 87% of the patients who underwent the surgery achieved 20/40 or better vision at 3 months follow up. Kurz et al 18 in their study showed postoperative best corrected visual acuity (BCVA) was found to be statistically better with MICS than standard phacoemulsification. Alioet al11, Crema et al18 in their studies did not find any statistical differences between the two techniques. The findings in our study corroborate with that of various studies in literature.

In our study the result varied, the amount of mean surgically induced astigmatism for standard phacoemulsification at day 1 was 1.20±0.76 which reduced to 1.05±0.73 at 1week and further reduced to 0.70±0.31 at 6 weeks. In coaxial MICS group it was 0.82±0.60 at day 1, 0.62±0.45 at 1 week and 0.58±0.37 at 6 weeks follow up period. There was statistically significant difference (p<0.05) in SIA between the two groups at day 1 and 1 week follow up period, but no significant difference at 2 weeks, 4 weeks and 6 weeks follow up visits.

Coaxial MICS, performed through an incision of approximately 2 mm, also demonstrates good results with low surgically induced astigmatism.

A recent study reported no significant difference in surgically induced astigmatism between the two microincision techniques; however astigmatic control is not the only requirement for faster visual rehabilitation. Trauma to the corneal endothelial cells must also be minimized to ensure the best optical outcomes.19

The great advantage of MICS is the reduction of SIA and that the microincisions do not produce an increase in astigmatism when compared with conventional 3 mm phacoemulsification. The shorter the incision, the less the corneal astigmatism, as it was estimated that the magnitude of the SIA studied by vector analysis was around 0.44 and 0.88 D, rising as the size of the incision increased. This is considered important because cataract surgery today is considered more and more a refractive procedure. Also, small incision surgery (3.5-mm incision without suture) does not systematically degrade the optical quality of the anterior corneal surface. However, it introduces changes in some aberrations, especially in no rotationally symmetric terms such as astigmatism, coma and trefoil. Therefore, one has to expect better results and lesser changes with sub 2 mm incision (MICS).

Alio et al10 demonstrated a statistically significant difference (p<0.05) in SIA between the two groups at 1 month, 3 months and 6 months follow up period. However, such a difference was not seen in the comparative study done by Dogruet al.13

Wilczynskaet al25 in their study did not find any significant difference in SIA during the whole follow up period between bimanual MICS and coaxial phacoemulsification.

In our study,we observed that the mean effective phacoemulsification time in the standard phacoemulsification group was 29.80±3.67 seconds and 31.93±4.08 seconds in the coaxial microincision cataract surgery group. There was statistically significant difference between the two groups (p<0.05). The studies done by Dogruet al17, also did not show any significant difference in the mean effective phacoemulsiflcation time. However, Alio et al11 in their study showed a lesser mean phacoemulsification time, total phacoemulsiflcation percent, effective phacoemulsiflcation time in the micro incision group whereas in the study conducted by Dosso et al10 found statistically significant higher mean ultrasound time in coaxial MICS than conventional phacoemulsification group, which did not correlate with our study.

Kurz et al19 indicated decrease of phacoemulsification time in MICS group compared with coaxial surgery. Kahraman et al23showed decrease of phacoemulsification time in the MICS group compared with coaxial group (p = 0.001).

The mean total phacoemulsification power/percent in standard phacoemulsification was 35.77± 5.17% whereas 33.70± 3.05% in coaxial MICS group. Our study showed that there was lesser power used in coaxial MICS in comparison to standard phacoemulsification.

Alioet al11 showed large difference between amounts of energy delivered into the eye. In MICS, phacoemulsification parameters were adjusted to overcome the possibility of wound burn and anterior chamber instability. The need for decreasing the power and vacuum was thought to be associated with increase in the effective phaco time, average percentage power, phacoemulsification time and surgery time.

Other studies Mencucciet al23, Kurz et al19, Wilczynski et al20 found no statistical differences between the two techniques. In a study comparing microincision (2.2 mm) versus standard (2.8 mm) clear corneal cataract surgery, mean cumulative dissipated energy was 6.64±3.82 in the 2.8 mm incision group and 5.07±3.14 in the 2.2 mm group; the difference was significant but this could be attributed to the use of different phaco tip configurations in between two groups.24

Tanaka et al24 showed lower ultrasonic output in the bimanual group than in the coaxial group. Tanaka et al correlated it with better efficiency of nuclear treatment, including nuclear compliance, crushing and flexor hinge in the case of bimanual procedure. Cremaet al18 showed the mean US power was similar between groups (mean 10.1 ± 3.76% and 10.0 ± 4.0%, respectively).

In our study the mean total balanced salt solution used in standard phaco group was 128.83±19.81ml whereas 139.33±13.57ml in coaxial MICS group which was statistically significant. Alioet al11 observed no significant difference in total BSS used in both MICS and coaxial phacoemulsification group. Dossoet al10 also did not find any statistically significant difference between total BSS used in coaxial MICS and conventional coaxial cataract surgery.

No early intraoperative or postoperative occurred that require a change in therapy. No eye showed signs of corneal thermal burn, zonular dehiscence, posterior capsular ruptures, 1OL decentration, IOL pigmentation, and IOL discoloration. Only one case had minor damage to IOL but did not show any IOL decentration and was excluded from the study.

Alioet al11, Dogru et al17, Agarwal et al7 also did not report any significant wound burn in their respective case studies.

CONCLUSION

In Standard phacoemulsification the mean best corrected visual acuity at the end of6 weeks was 0.04±0.07 and 0.05±0.08 in the coaxial Microincision Cataract Surgery group. The difference between the two groups was not significant.

The mean SIA showed statistically significant difference between the two groups at 1st post-operative day was 1.20±0.76 in the Standard phacoemulsification group whereas 0.82± 0.60 in coaxial MICS group   and at 1 week was 1.05± 0.73 in Standard phaco group, whereas 0.62± 0.45 in coaxial MICS group post operatively. There was no significant difference between SIA in two groups at 2 weeks, 4 weeks and 6 weeks follow up visits.

There was significant statistical difference between the two groups in mean effective phacoemulsification time which was 29.80± 3.67 seconds in the Standard phacoemulsification group and 31.93± 4.08 seconds in coaxial MICS group.

The mean total phacoemulsification power in the Standard phacoemulsification group was 35.77±5.17%,  whereas 33.70± 3.05% in coaxial MICS group which was statistically significant.

The mean total BSSV used in the Standard phacoemulsification group was 128.83±19.81 ml, whereas 139.33±13.57ml in coaxial MICS group and was statistically significant.

The main advantage of coaxial MICS is that it uses the same methods as the standard technique but with smaller incisions. As the surgeon does not need to change his or her technique, the learning curve is short.Today; there is a clear trend towards smaller incisions and the discussion that because of small learning curve, better fluidics, same instrumentation, and the same IOL inserted through a sub-2mm incision, coaxial microincision cataract surgery is an ideal surgery technique.

Thus, it is concluded that Coaxial Microincision Cataract Surgery is a safe and effective technique for cataract surgery. Coaxial MICS can be used by all surgeons who are familiar with conventional phacoemulsification. Although effective phacoemulsification time and total volume of BSS used were significantly higher in coaxial MICS than with standard phacoemulsification group, the postoperative results of the two techniques were comparable.

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