Comparison of pupil expansion devices in small pupil phacoemulsification

Abstract

Purpose:

To study the outcomes of phacoemulsification in small pupils (≤4 mm) using pupil expansion devices at a tertiary eye care center in South India.

Methods:

The study design is prospective, randomized, comparative, and interventional. Mechanical pupil dilatation with iris retractors (group I), B-HEX ring (group II), and Gupta ring (group III) was compared with respect to pupil size achieved (intraoperative), total surgical time, device addition time, complications, endothelial cell loss, and postoperative best corrected visual acuity.

Results:

Among 36 participants (12 in each group), the mean pupil size, total surgical time, and device addition time were maximum with iris retractors. Intraoperatively, sphincter tear was seen in two eyes in the iris retractors group and one eye in the Gupta ring group. In the B-HEX ring group, only two flanges of the ring could be engaged in two participants, one patient had iris bleeding (during stretching of the iris), and one patient had anterior lens capsular tear. Among all three groups, there was no statistically significant difference in best corrected visual acuity (BCVA), endothelial cell count, and coefficient of variation obtained in the preoperative period, postoperative Day 7 and Day 30, respectively.

Conclusion:

In our study, in more than 50% of cases, the cause of small pupil was idiopathic/senile. Among nonidiopathic causes, PXF was the most common association. Although iris retractors are cost-effective and give maximum intraoperative dilatation, there is a need of four additional side ports to be made, thus increasing the total surgical time and device addition time. On the other hand, B-HEX and Gupta ring provide comparable intraoperative dilation and device addition time and also have comparable postoperative outcomes in terms of postoperative pupil size and complications.

According to the World Health Organization reports, cataract is the leading cause of blindness all over the world, being responsible for 47.8% of blindness, that is, 17.7 million blind people. In India, the reported prevalence of cataract is 58% in North India and 53% in South India among older age group (>60 years) people, with nuclear cataract being the most common type of cataract in both parts of the country.[1] Cataract extraction with intraocular lens (IOL) implantation is the most commonly performed surgical procedure. For successful cataract surgery, an adequate pupil dilation of ≥4 mm (usually achieved with conventional mydriatics) is of paramount importance.[2,3] The study conducted by Gimbel shows an incidence of 1.6% small pupils (≤4 mm) among 1880 eyes with cataract.[4] A poorly dilated pupil is associated with an increased incidence of intraoperative complications such as capsular rupture, iris prolapse, iris trauma, vitreous loss, and endothelial cell loss.[3,5,6,7] In patients with poor pupil dilation, the complication of vitreous loss is increased by a factor of two.[8,9]

There are numerous factors which lead to poor pupil dilation, such as preexisting ocular conditions (chronic iritis, posterior synechiae, pseudoexfoliation syndrome, glaucoma, patients on long-term miotic therapy like pilocarpine, uveitis, senile miosis), systemic disorders (diabetes mellitus), and intraoperative floppy iris syndrome (IFIS).[3] IFIS is strongly associated with the intake of alpha-1A-specific blockers like tamsulosin (used in the management of benign prostatic hyperplasia [BPH]). It is characterized by progressive intraoperative miosis and iris prolapse, and complication rates can increase up to 12.5%.[10]

Small, fixed pupils restrict the surgeon’s view and working space during phacoemulsification, which can lead to inadequate staining of the capsule, compromised capsulorrhexis, difficulty in making trench of sufficient length, iris getting caught in the probe, iris trauma, and trace amount of cortex being left.[3] Hence, while performing surgery, appropriate modifications are adopted to ensure adequate mechanical mydriasis. Some of the methods that have been reported to be useful for phacoemulsification in small pupil include modification of the phacoemulsification technique with minimal iris manipulation,[3,11] use of iridectomy,[12] multiple small sphincterotomies,[13] stretch pupilloplasty,[14] iris retractors, B-HEX pupil expander,[15] and Malyugin ring.[16]

We aimed to study the outcomes of phacoemulsification in small pupil by comparing the B-HEX ring, Gupta ring, and iris retractors concerning their intraoperative pupil size achieved, total surgical time, device addition time, specular count, best corrected visual acuity (BCVA), and complications.

Methods

This prospective, randomized interventional, and comparative study was conducted after obtaining clearance from the Institutional Ethical Committee (IEC). Written and informed consent was taken from the patients. The study period was 17 months and included a total of 36 eyes with post-dilatation pupil size (post-peribulbar block) less than or equal to 4 mm. We compared the outcomes of phacoemulsification in small pupil by comparing the following pupil expansion devices: iris retractors, B-HEX ring, and Gupta ring. All grades of cataract were included in this study.

We excluded patients with active iritis in the past 3 months, posterior synechiae >1 clock hour, advanced glaucoma with macular threat, specular endothelial cell count <2000/mm³, subluxated lens, traumatic cataract, corneal disorders, anterior segment anomalies, and history of previous retinal surgeries. All patients underwent standard cataract evaluation, and cataract grading was done using lens opacities classification system (LOCS) - III. Intraocular pressure (IOP) was measured by non-contact tonometer (NCT), and applanation tonometry was done in patients with glaucoma. Investigations were carried out to screen diabetes mellitus and systemic hypertension in all patients. Appropriate control of systemic conditions was achieved before surgery.

The 36 selected patients with post-dilatation (and post- peribulbar block) pupil diameter ≤4 mm were randomized by block randomization technique into three groups: group I- iris retractors (IrisCare by Madhu Instruments. Pvt. Ltd), group II- B-HEX ring (Med Invent Devices Pvt. Ltd.), and group III- Gupta ring (Madhu Instruments. Pvt. Ltd). All the surgeries were performed by a single surgeon who is experienced in all three techniques, using the ZEISS Lumera microscope and the Alcon Infiniti type of phaco unit. The preoperative pharmacological regimen consisted of moxifloxacin 0.5% eye drops which was instilled 4 times at two hourly intervals (starting 8 h before the surgery), Nepafenac 0.1% eye drops was instilled 3 times at one hourly intervals (starting 3 h before the surgery). Preoperative pupillary dilatation was achieved by instilling tropicamide 0.8% with phenylephrine 5%, 3 times at 20-min intervals starting 1 h before the surgery. The handmade scale [Fig. 1] was used to screen patients with preoperative pupil diameter (post-pharmacological dilatation and post-peribulbar block) less than or equal to 4 mm. The intraoperative pupil diameter was measured to the nearest millimeter using Castroviejo calipers under the surgical microscope following these four steps: before beginning the surgery before beginning the surgery (i.e. before entering AC), post-ophthalmic viscosurgical devices (OVD) injection, after device insertion, and at the end of the surgical procedure. A clear corneal temporal incision of 2.8 mm was made followed by staining of the anterior capsule with trypan blue (0.06%) dye and the OVD (hydroxypropyl methylcellulose 2%) was injected.

Figure 1.

Printed digital custom-made scale used for screening

In group I (iris retractors), four limbal incisions (1 mm each) were placed at a gap of 3 clock hours from each other, followed by insertion of four flexible iris retractors (made up of polypropylene) through these sites. The pupil is stretched for adequate space for phacoemulsification. In group II, the pupil was bimanually stretched with the help of Kuglen hooks, followed by the insertion of a B-HEX ring with the help of 23 G micro-forceps. Alternate flanges are tucked under the iris, with notches engaged to the margins of the pupil. In group III, a Gupta ring was inserted via a disposable injector into the anterior chamber through the main port and attached to the pupillary margin in a circular manner with the help of Sinskey hook. All the above techniques were followed by careful and well-centered continuous curvilinear capsulorrhexis. After a careful hydrodissection and hydrodelineation, the cataractous nucleus was fragmented and emulsified by phaco probe, followed by a cortical wash by bimanual irrigation/aspiration probe and implantation of foldable IOL in the capsular bag. Iris retractors, B- HEX ring, and Gupta ring were removed in group I, II, and III, respectively. Thereafter, OVD was thoroughly aspirated using the irrigation/aspiration system. Total surgical time, that is, the duration of time taken from the start of making the main incision to the removal of the eye speculum, was noted down. Device addition time, that is, the duration of time taken from when the device was taken by the surgeon in his hand up to completion of device insertion, was also noted down. Postoperative pharmacological regimen consisted of moxifloxacin (0.5%) eye drops 4 times per day for 2 weeks, prednisolone (1%) eye drops given for 6 weeks in tapering dose, and nepafenac (0.1%) eye drops instilled 3 times per day for 6 weeks.

All patients were followed up on day 1, day 7, and 1 month postoperatively and any intra- or postoperative complications, if present, were noted. The pupil diameter, visual acuity, pachymetry, and specular microscopy counts were recorded on day 7 and 1 month postoperatively. All data was entered into a proforma from which a master chart was prepared and the data was analyzed using the computer software IBM Statistical Package for the Social Sciences (SPSS) version 22.

Results

Our study was conducted to compare three pupil expansion devices, that is, iris retractors, B-HEX ring, and Gupta ring, for successful phacoemulsification in patients with small pupil ≤4 mm (i.e., dilated pupil which is ≤4 mm). The final analysis included a total of 36 subjects, with 12 participants in each group. Out of 36 participants, 24 participants were male (66.67%) and 12 were female (33.33%). The mean age of the study population was 69.61 ± 7.34 years, with the range being 53–86 years (95% confidence interval [CI] 67.1–72.1). Twenty-two eyes were right sided (61.11%), while 14 eyes were left sided (38.89%). Among 36 participants, 15 participants (41.67%) were known cases of DM, nine participants had Pseudo-exfoliation (PXF) (25%), four participants (11.11%) were on antiglaucoma medications (AGM), one participant had IFIS (2.78%), three participants (8.33%) had posterior synechiae <1 clock hour, and 19 participants had idiopathic/senile cause (52.78%).

The dilated pupil sizes before entering the anterior chamber in iris retractors, B-HEX ring, and Gupta ring groups were 3.92 ± 0.19, 4 ± 0, and 3.92 ± 0.19 mm, respectively. On measuring post-device insertion distance between two parallel sides and applying paired t-test, a significant difference was obtained when iris retractors (7 ± 0.64 mm) were compared to B-HEX ring (6.21 ± 0.33 mm, P = 0.000) and Gupta ring (6.21 ± 0.4 mm, P = 0.000), respectively. There was also statistically significant difference in diagonal measurement of pupil size on post-device insertion, where the maximum size was achieved by iris retractors (maximum 8.29 ± 0.75 mm) when compared to B-HEX ring (7.21 ± 0.4 mm, P = 0.000) and Gupta ring (7.67 ± 0.49 mm, P = 0.011). [Summary of pupil dilatation post-device insertion values is given in Table 1]. There was a statistically significant difference in intraoperative pupil size after removal of the device in iris retractors (5.83 ± 0.81 mm; maximum residual effect) when compared to B-HEX ring (4.83 ± 0.83 mm, P = 0.007) and Gupta ring (4.83 ± 0.91 mm, P = 0.007).

Table 1.

Comparison of mean dilated intraoperative pupil size (across study groups): post-device insertion

Group		Mean±SD		Mean difference		95% CI				P
						Lower		Upper
Post-device insertion between two parallel sides (mm)
Group I iris retractors (baseline)		7±0.64
Group I versus group II B-HEX ring		6.21±0.33		0.792		0.397		1.187		0.000
Group I versus group III Gupta ring		6.21±0.4		0.792		0.397		1.187		0.000
Group II versus group III				0.00		0.00		0.39		1.000
Post-device insertion diagonal (mm)
Group I iris retractors (baseline)		8.29±0.75
Group I versus group II B-HEX ring		7.21±0.4		1.083		0.612		1.555		0.000
Group I versus group III Gupta ring		7.67±0.49		0.625		0.154		1.096		0.011
Group II versus group III				-0.46		-0.93		0.01		0.056

CI=Confidence interval, SD=Standard deviation

On applying paired t-test, it was observed that there was a statistically significant difference in preoperative versus postoperative undilated pupil size in all three groups. The difference was highly significant with iris retractors (P < 0.05). B-HEX ring caused the least trauma, whereas Gupta ring provided comparable results when compared to B-HEX ring [Table 2].

Table 2.

Comparison of mean preoperative and postoperative UNDILATED pupil size (in mm) in groups (n=36)

UNDILATED pupil size (in mm)		Pre-op		Post-op 1 month		P
Group I iris retractors		1.79±0.33		3.79±0.89		<0.001
Group II B-HEX ring		1.75±0.4		2.38±0.53		0.004
Group III Gupta ring		1.79±0.45		2.63±0.68		0.003

It was observed that there was no statistically significant difference in pupil size within all three groups before entering the anterior chamber and post-OVD injection.

We also observed a statistically significant difference in total surgical time [Table 3] with iris retractors (25.83 ± 7.02 min) when compared to B-HEX ring (20.42 ± 3.34 min, P = 0.013), but there was no statistically significant difference in total surgical time when either of the above groups was compared with Gupta ring (22.08 ± 3.96 min). There was also a statistically significant difference in device addition time with iris retractors (308.5 ± 84.04 sec) when compared to B-HEX ring (239.75 ± 77.55 sec, P = 0.025) and Gupta ring (231.92 ± 48.2 sec, P = 0.013).

Table 3.

Comparison of mean total surgical time and device insertion time across study groups

Group		Mean±SD		Mean difference		95% CI				P
						Lower		Upper
Mean total surgical time (min)
Group I iris retractors (baseline)		25.83±7.02
Group I versus group II B-HEX ring		20.42±3.34		5.42		1.232		9.601		0.013
Group I versus group III Gupta ring		22.08±3.96		3.75		-0.434		7.934		0.077
Group II versus group III				1.67		-2.52		5.85		0.424
Mean device addition time (sec)
Group I iris retractors (baseline)		308.5±84.04
Group I versus group II B-HEX ring		239.75±77.55		68.75		9.240		128.260		0.025
Group I versus group III Gupta ring		231.92±48.2		76.58		17.073		136.093		0.013
Group II versus group III				7.83		-51.68		67.34		0.791

CI=Confidence interval, SD=Standard deviation

Among all three groups, there was no statistically significant difference in BCVA and endothelial cell count obtained in the preoperative period and on postoperative Day 7 and Day 30, respectively [Table 4].

Table 4.

Comparison of specular microscopy – cell density (cells/mm²) and BCVA among groups

Specular microscopy
Parameter		Group						F		P
		Iris retractors		B-HEX ring		Gupta ring
Cell density (cells/mm2)
Pre-op		2421.02±286.31		2730.39±479.07		2603.68±225.37		2.40		0.106
Post-op-Day 7		1936.64±392.82		2050.95±266		1894.38±314.91		0.682		0.513
Post-op 1 month		1956.71±367.88		1975.6±405.68		1876.03±257.17		0.275		0.761
BCVA (LogMAR)
Pre-op		1.35±0.87		1.01±0.77		1.01±0.84		0.654		0.526
Post-op Day 7		0.24±0.17		0.2±0.18		0.19±0.15		0.315		0.732
Post-op Day 30		0.11±0.15		0.1±0.12		0.12±0.15		0.062		0.940

BCVA=Best corrected visual acuity, logMAR=Log of minimum angle of resolution

In our study, sphincter tear was seen with iris retractors in two participants and with Gupta ring in one participant. In B-HEX ring, only two flanges of the ring could be engaged in two participants, one patient had iris bleeding (during stretching of the iris), and one patient had anterior lens capsular tear.

Discussion

A well-dilated pupil is one of the most important requirements for safe and successful phacoemulsification surgery. Hence, it is important to find a pupillary dilation device which provides adequate dilatation during phacoemulsification. In this study, we compared three pupil expansion devices – iris hooks, B-HEX ring, and Gupta ring. At present, there is no study comparing these three devices in India. We compared their outcomes in terms of intraoperative pupillary dilatation, total surgical time, device addition time, BCVA, endothelial cell loss, and intraoperative and postoperative complications. A total of 36 patients, with 12 patients each in iris hooks (group I), B-HEX ring (group II), and Gupta ring (group III), were studied between November 2020 and March 2022. All grades of cataract were included in our study.

Among 36 participants, the most common association with small pupil, among non-idiopathic causes, was PXF and among systemic illnesses, it was diabetes mellitus (41.67%), which correlates with other studies.[5,17,18,19]

Among the three devices studied, intraoperatively, maximum pupillary size both in terms of diameter (7 ± 0.64 mm) and area (44.27 ± 7.67 mm²) was achieved with iris retractors. Usage of both B-HEX ring and Gupta ring resulted in intraoperative pupillary diameter of 6.21 ± 0.33 and 6.21 ± 0.4 mm, respectively. Thus, usage of both B-HEX ring and Gupta ring resulted in equal intraoperative pupillary dilatation in terms of diameter, but B-HEX resulted in more intraoperative pupillary area (42.6 ± 3.47 mm²). Among the three devices, minimum pupillary area post-device insertion was seen with Gupta ring (37.23 ± 6.66 mm²). In our study, iris hooks provided maximum dilatation (7 ± 0.64 mm), which is comparable to Akman et al.’s[20] study, in which maximum dilatation was provided by Polymethyl-methacrylate (PMMA) ring (5.9 ± 0.6 mm) and iris hooks (5.6 ± 0.6 mm). All three devices provided stable intraoperative pupillary dilatation, which is comparable to the study conducted by Wang et al.[21]

Among the three devices included in our study, the mean total surgical time was maximum with iris retractors (25.83 ± 7.02 min) and minimum with B-HEX ring (20.42 ± 3.34 min). The mean total surgical time in Gupta ring group was 22.08 ± 3.96 min. We found a statistically significant difference in the mean total surgical time between iris retractors and B-HEX ring. The mean device addition time was maximum with iris retractors (308.5 ± 84.04 sec). In our study, both the mean device addition time (308.5 ± 84.04 sec) and the mean total surgical time (25.83 ± 7.02 min) were significantly higher with iris hooks, which is comparable to the studies of Akman et al. (297 ± 51 sec)[20] and Nderitu et al. (30 min),[22] respectively. The technique using iris retractor was the most time-consuming because of the time taken to create four additional stab incisions followed by inserting and positioning them. The location and direction of the stab incisions are important in obtaining the desired outcome in terms of stable intraoperative dilatation, and therefore, use of these hooks requires a certain level of experience. In addition, the requirement for four stab incisions and four instruments placed in the eye increases the level of risk involved, especially for novice surgeons. Whereas both B-HEX ring and Gupta ring provided comparable mean device addition time of 239.75 ± 77.55 and 231.92 ± 48.2 sec, respectively.

In our study, we compared the preoperative and postoperative undilated pupil size at the end of 1 month in each group. We observed that there was statistically significant difference in all groups, but the difference was highly significant in iris retractor group (with a P value < 0.001) [Table 2]. Thus, all devices showed residual effect of stretching on undilated pupil size; the maximum effect was seen with iris retractors group. Gross irregular pupils were seen in three cases of iris retractors group and one case of Gupta ring. Among the four irregular pupils, three sphincter ruptures were seen as follows: two cases of iris retractors group and one case of Gupta ring. There was no association of B-HEX ring with either sphincter tear or irregular pupil. Balal et al.[23] reported overall increased incidence of sphincter tear with Malyugin ring (six cases) compared to iris hooks (one eye), but this can be attributed to their large sample of 469 eyes and 194 eyes in Malyugin ring and iris hooks groups, respectively. There is no comparable data of complications with regards to Gupta ring. It was also observed that patients whose eyes were affected with sphincter rupture presented with the complaint of glare. The physiological function was comparable in all 33 remaining eyes.

In our study, B-HEX ring was associated with incomplete device insertion in two cases, iris bleeding (during stretching of the iris), and anterior lens capsular tear in one case. There was one case of small posterior capsular rent (PCR) in the iris retractor group (PCIOL placed in the bag), which occurred during cortical wash, and hence, we do not attribute this complication to the device insertion and manipulation. The additional complications noted in other studies include zonular fiber rupture with or without vitreous loss,[22] cystoid macular edema (CME), and uveitis.[13] These complications were not seen in our study.

Among all three groups in our study, there was no statistically significant difference in BCVA recorded at 1-month postoperative period. This is comparable to other studies.[21,22,23] In our study, there was comparatively less endothelial cell density (ECD) loss in iris retractors group (19.64% ±13.83%), but this difference was not statistically significant when compared to the other two pupil expansion rings – B-HEX ring (26.57% ± 15.37%) and Gupta ring (27.35% ± 12.31%). This is comparable to Wang et al.’s study,[21] but not comparable to the study conducted by Wilczynski et al.,[24] in which ECD loss was significantly higher with iris hooks when compared to pupil expansion (Malyugin) ring.

It can also be noted that, the cost of iris retractors is INR 800/- for five pieces, B-HEX ring is INR 2995/-, and Gupta ring is INR 2500/-. Although iris retractors are cost-effective and give maximum intraoperative dilatation, there is a need of four additional side ports to be made, thus increasing the total surgical time and device addition time.

Conclusion

In our study, in more than 50% of cases, the cause of small pupil was idiopathic/senile. Among nonidiopathic causes, PXF was the most common association. Among the three expansion devices, iris retractors are cost-effective and also provide maximum intraoperative dilatation, but there is a need for four additional stab incisions, which increases device addition time and the risk of intraoperative complications, especially for novice surgeons. We observed that the B-HEX pupil expander was very thin and difficult to maneuver. On the other hand, Gupta ring requires a disposable injector for insertion, but is sturdy in comparison to B-HEX ring. Both the pupil expansion rings provide comparable intraoperative and postoperative outcomes in terms of pupil size achieved and occurrence of complications.

Financial support and sponsorship:

Nil.

Conflicts of interest:

There are no conflicts of interest.