Abstract
Purpose
To compare the surgical outcomes of phacoemulsification–subscleral trabeculectomy versus phacoemulsification–deep sclerectomy with intraoperative mitomycin C in open-angle glaucoma.
Methods
The study was conducted on 40 chronic primary open-angle glaucomatous eyes with senile cataract. They were divided into two groups: group I (n = 20): eyes undergoing phacoemulsification with subscleral trabeculectomy, and group II (n = 20): eyes undergoing phacoemulsification with deep sclerectomy. Intraoperative mitomycin C (0.4 mg/ml for 3 min) was applied in both groups. Postoperative intraocular pressure (IOP), complications, glaucoma medications, visual outcomes, and the bleb appearance were assessed for 12 months.
Results
The mean postoperative IOP was significantly lower (P < 0.05) in both groups in all time intervals in comparison to their preoperative values. The mean postoperative IOP was 14.1 ± 5.4 mmHg in group I, and 14.8 ± 3.1 mmHg in group II. No major complications were encountered in either procedure, but complications such as shallow anterior chamber, hypotony, and delayed bleb leaks were common in group I, whereas intraoperative perforation of Descemet’s membrane occurred in group II. No significant difference in visual acuity improvement, visual field changes, and surgical success outcome were found between both groups.
Conclusion
There was no significant difference in IOP reduction, surgical complications and visual outcomes between subscleral trabeculectomy, or deep sclerectomy with intraoperative mitomycin C in combination with phacoemulsification and intraocular lens implantations in patients with primary open-angle glaucoma.
Keywords: Phacoemulsification, Subscleral trabeculectomy, Deep sclerectomy
1. Introduction
Ophthalmologists have many options in treating patients with both cataract and glaucoma. Combined cataract and glaucoma surgery decision depends on several individual patients factors including the degree of visual improvement, target IOP, stage of glaucoma, compliance, age and life expectancy (Vass and Menapace, 2004).
Recent advances in cataract incision techniques and in glaucoma medications have changed the indications for surgery by minimizing the severity of complications. In early 1980s, extracapsular cataract extraction with trabeculectomy were reported to be effective but larger wound size was associated with more inflammation and hyphema (McCartney et al., 1988). In 1990s, phacoemulsification and the use of small incision foldable lenses increased the success of combined phacoemulsification trabeculectomy surgery (Friedman et al., 2002). Augmentation of the procedure with mitomycin C (MMC) has been shown to be beneficial when risk factors for failure are present (Shin et al., 1998).
Trabeculectomy has been a standard procedure for medically uncontrollable glaucoma. Friedman et al. (2002) reported the superior hypotensive effect of combined trabeculectomy and phacoemulsification in comparison with cataract surgery alone. However, several studies reported that phacotrabeculectomy provided less intraocular pressure reduction, and smaller success rates compared with trabeculectomy alone (Lochhead et al., 2003).
More recently, non-penetrating procedures as deep sclerectomy with or without an intrascleral implant, as well as viscocanalostomy have been developed as alternative to trabeculectomy. Non-penetrating anti-glaucoma procedures combined with cataract surgery have also been advocated as useful means of treating eyes with open-angle glaucoma and visually significant cataract (D’Eliseo et al., 2003; Shaarawy et al., 2003). The success rates of deep sclerectomy can be improved and IOPs in the low teens achieved by using intraoperative MMC application (Anand and Atherley, 2005).
The aim of this study was to compare the outcomes of phaco-subscleral trabeculectomy and phaco-deep sclerectomy with mitomycin C in eyes with primary open-angle glaucoma.
2. Materials and methods
This is a prospective, comparative randomized study.
2.1. Patients
This study included 40 eyes of 30 patients with visually significant cataract and chronic primary open-angle glaucoma with an IOP of 22 mmHg or more despite medical therapy. A diagnosis of glaucoma was based on the appearance of optic nerve head cupping, gonioscopy results, and visual field alteration.
Eyes included in the study were divided into two groups:
Group I: included 20 eyes of 15 patients undergoing phacoemulsification with subscleral trabeculectomy. Their age ranged from 45 to 62 years.
Group II: included 20 eyes of 15 patients undergoing phacoemulsification with deep sclerectomy. Their age ranged from 45 to 60 years.
In either group I or II, intraoperative mitomycin C (MMC) (0.4 mg/ml (0.04%) for 3 min) was applied.
2.2. Preoperative assessment
All patients were subjected to full ophthalmic examination including; visual acuity assessment, slit-lamp biomicroscopy for (assessment of corneal clarity, anterior chamber depth, noting of lens morphology and grading the nuclear hardness), Goldmann applanation tonometer, Humphery 24-2 visual field analysis, fundus examination, B-scan ultrasonography, keratometry, biometry and refraction (if possible).
In addition, clinical data as age, gender, history of ocular inflammation, history of any surgical intervention, and anti-glaucoma medical regimen were collected.
2.3. Exclusion criteria
Exclusion criteria included eyes with soft nuclei or very hard nuclei, shallow anterior chamber, significant corneal opacity, previous intraocular surgery, congenital or juvenile glaucoma, angle-closure glaucoma, high risk glaucoma patients, and ocular diseases (uveitis and retinopathy).
2.4. Surgical procedures
All surgeries were performed by a single surgeon (A.I.M.). Phacoemulsification and intraocular lens implantation was performed through a temporal corneal incision separate from the subscleral trabeculectomy site or deep sclerectomy site.
A lid speculum was applied in the eye and a superior rectus traction suture used to inferoduct and manipulate the globe during the procedure.
2.5. Phacoemulsification
A fornix-based conjunctival flap was raised at the 12 o’clock position. A 19-gauge keratome was used to create 2 clear corneal incisions at the 10 o’clock and 2 o’clock positions. A curvilinear capsulorhexis was created with a capsulorhexis forceps (Bausch & Lomb surgical) through the 10 o’clock corneal wound under a healon (sodium hyaluronate 1%). Hydrodissection and hydrodelineation were performed. The sleeveless phaco needle entered the anterior chamber through the 10 o’clock corneal wound, while the Aggrawal irrigation chopper (20 gauge or 0.9 mm outer diameter, 0.7 mm bore, 65 cm3/min flow rate) entered the anterior chamber through the 2 o’clock corneal wound.
A standard bimanual phacoemulsification technique was performed using the divide and conquer technique. A deep groove was made within the confine of capsulorhexis. Then, the groove was gradually deepened until it was seen that the epinucleus plate has been penetrated. The nucleus and epinucleus were then fractured using the phaco tip and a nucleus manipulating hook. A second groove was performed perpendicular to the first and each half was fractured into two quadrants. Phaco machine settings during stage 1 were power 45–50%, vacuum 40–80 mmHg, and flow rate 24 ml/min. The bottle height was routinely set 100 cm above eye level to start and then adjusted according to anterior chamber depth. Phaco machine settings during stage 2 were power 45–50%, hyperpulse mode at 50 Hz, vacuum 280 mmHg, and flow rate 24 ml/min. However, these parameters have been changed according to the hardness of the nucleus. Bimanual irrigation/aspiration (I/A) was completed through the 2 corneal wounds, followed by reformation of anterior chamber and capsular bag with a healon. A 3-piece hydrophobic acrylic intraocular lens was implanted in the capsular bag through the 3.0 mm incision. Removal of any residual viscoelastic from the anterior chamber.
2.6. Subscleral trabeculectomy
The surgery was performed as follow: after making a fornix-based conjunctival flap. A limbus-based rectangular scleral flap 3 × 4 mm about half scleral thickness was created to clear cornea. Careful haemostasis of the exposed sclera using wet field cautery was performed. Mitomycin C 0.4 mg/ml (0.04%) soaked sponges were placed underneath the scleral flap for 3 min, then the area irrigated with 500 ml saline. Trabeculectomy was done beneath the scleral flap 1 × 3 mm and peripheral iridectomy was performed (Fig. 1a and b). The lamellar scleral flap was closed with 10-0 nylon sutures adjusted to allow minimal leakage during reformation of anterior chamber. Finally, Tenon’s layer and the conjunctiva were tightly closed separately with 10-0 nylon sutures.
Figure 1.
(a) Excision of trabecular block and (b) peripheral iridectomy.
2.7. Deep sclerectomy
The surgery was performed as follow: after making a fornix-based conjunctival flap, a 5 × 5 superficial scleral flap was dissected. Careful haemostasis of the exposed sclera using wet field cautery was performed. Mitomycin C 0.4 mg/ml (0.04%) soaked sponges were placed underneath the scleral flap for 3 min, then the area irrigated with 500 ml saline.
The superficial scleral flap has to be continued 1–1.5 mm anteriorly into clear cornea. A second deep scleral flap 4 × 4 mm and leaving about 10% of the sclera over the choroid and ciliary body was dissected. A horizontal dissection was performed starting posteriorly and moving anteriorly using a crescent blade. Schlemm’s canal was automatically unroofed near the limbus (Fig. 2a). To facilitate the identification of the Schlemm’s canal, the assistant should keep the dissection area dry. Also, the tissue can be pushed laterally with the cutting blade for a clearer vision of the Schlemm’s canal. The dissection was continued anteriorly using a blunt spatula or sponge to find the natural cleavage plane between Descemet’s membrane and corneal stroma. When Descemet’s membrane has been exposed for 1 mm, the second deep scleral flap was excised (Fig. 2b). At this stage, aqueous was seen percolating through the anterior trabeculum and Descemet’s membrane. The superficial scleral flap was sutured with 10-0 nylon sutures (usually 2 sutures, one at each corner).
Figure 2.
(a) Deroofing of canal of Schlemm and (b) excision of the deep scleral flap.
Following surgery, all eyes received topical antibiotic and corticosteroid three times daily, then they tapered and discontinued after 4–6 weeks. The patients were followed up for 12 months. Patients were examined 1 day postoperative, then every week in the first month, then monthly.
2.8. Follow-up of patients
The outcome of the surgical procedures were evaluated according to:
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Intraocular pressure (IOP) without medication. Three measurements with Goldmann applanation tonometer were recorded in each eye, the mean of which was used in the calculation.
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Visual field testing with a Humphrey automated visual field analyzer (Humphrey Zeiss, Dublin, CA) program 24-2 central threshold was carried out before surgery and 6, 12 months after surgery.
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Best-corrected visual acuity was measured using snellen line chart, and the logarithm of the minimum angle of resolution visual acuity was calculated and used for all statistical analysis. An increase or decrease in visual acuity was defined as a change of more than 0.2 in logarithm of the minimum angle of resolution visual acuity.
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Biomicroscopic classification of the filtering bleb (Picht and Grehn, 1998) into: type 1 bleb, presence of microcysts, diffuse borders and no or little vascularization (favourable bleb). Type III bleb, presence of corkscrew vessels, prominent vascularization, dense scar tissue and demarcation of bleb borders (unfavourable bleb). Type II bleb, intermediate bleb (less favourable bleb).
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Presence of complications such as perforation Descemet’s membrane, shallow anterior chamber, hypotony, IOP spike, hyphema, posterior synechiae, rupture of posterior lens capsule, and vitreous loss were recorded.
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Need for further treatment (needling, 5-fluorouracil injection (0.2 ml/5 mg), and selective argon Laser suturelysis in the subscleral trabeculectomy group, and Nd:YAG Laser goniopuncture in the deep sclerectomy group). Goniopuncture was done using YAG Laser in the free running Q-switched mode, energy ranging from 4 to 8 mj, 4–15 shots were applied. The aiming beam was focused on the semitransparent trabeculodescemetic membrane, with a gonioscopy contact lens.
Success of the procedure was defined as a complete success with an IOP between 6 and 20 mmHg and an IOP reduction of 30% or more without glaucoma medication or additional surgery, compared with the preoperative level with medical therapy. A qualified success was defined as an IOP of between 6 and 20 mmHg with glaucoma medication or an IOP reduction of less than 30% compared with the preoperative level with medical therapy. A failure was defined as an eye requiring further glaucoma surgery.
2.9. Statistical analysis
Was done using SPSS program version 10. Student’s t-test was for comparing means of quantitative data. To evaluate the difference in IOPs between follow-up intervals, the paired t-test was used. All t-test were tailed. Categoric variables were evaluated with the χ2-test, or the Spearman rank correlation as appropriate. A level of P < 0.05 was considered statistically significant. Success was evaluated on the basis of Kaplan–Meier cumulative probability (long-rank test).
3. Results
The study included 40 eyes of total 30 patients had combined cataract and glaucoma surgery, 20 eyes had phacoemulsification with subscleral trabeculectomy (group I), and 20 eyes had phacoemulsification with deep sclerectomy (group II).
Table 1 list preoperative demographic and clinical characteristics of patients in the studied groups. There was no statistically significant difference in age, gender, mean IOP, mean cup:disc ratio, mean deviation, logarithm of minimum angle of resolution of best-corrected visual acuity and number of anti-glaucoma medication between both groups (P = 0.85, P = 0.75, P = 0.68, P = 0.75, P = 0.52, and P = 0.75, P = 0.46, respectively, χ2-test and unpaired t-test).
Table 1.
Preoperative demographic and clinical data of the studied patients.
| Parameters | Group |
Pa | |
|---|---|---|---|
| Phaco-subscleral trabeculectomy | Phaco-deep sclerectomy | ||
| Number of eyes | 20 | 20 | |
| Mean age (years) | 54.5 ± 2.5 | 56.2 ± 3.4 | 0.85 |
| Gender (M:F) | 8:12 | 7:11 | 0.75 |
| Mean IOP (mmHg) | 23.5 ± 2.1 | 24.1 ± 1.5 | 0.68 |
| Mean cup:disc ratio | 0.65 ± 0.21 | 0.66 ± 0.25 | 0.75 |
| Mean deviator (dB) | −17.50 ± 5.41 | −18.83 ± 5.61 | 0.52 |
| Log MAR best corrected V.A | 0.795 ± 0.81 | 0.641 ± 0.28 | 0.75 |
| No. of anti-glaucoma medication | 2.1 ± 0.8 | 2.2 ± 0.6 | 0.46 |
M:F, Male:female; IOP, intraocular pressure; V.A, visual acuity; Log MAR, logarithm of minimum angle of resolution; No., number.
Results of the paired t-test and χ2-test.
Table 2 shows that there was significant reduction (P < 0.01) in IOP at all visit through out the follow-up period in both groups. On the other hand, there was no significant difference in mean postoperative IOP between the two groups at intervals of 1 week, 1 month, 3 months, 6 months, 9 months, and 12 months visits (P = 0.12, P = 0.18, P = 0.16, P = 0.26, P = 0.45, and P = 0.42 respectively), although the IOP was lower in the subscleral trabeculectomy group at every visit.
Table 2.
Postoperative IOP (mmHg) results of the studied patients.
| Parameters | Group |
Pa | |
|---|---|---|---|
| Phaco-subscleral trabeculectomy | Phaco-deep sclerectomy | ||
| Baseline | 23.5 ± 2.1 | 24.1 ± 1.5 | 0.68 |
| One week postop. | 11.1 ± 2.1 | 11.3 ± 3.0 | 0.12 |
| One month postop. | 12.1 ± 2.2 | 12.9 ± 2.9 | 0.18 |
| Three months postop. | 12.4 ± 2.6 | 13.1 ± 3.1 | 0.16 |
| Six months postop. | 12.9 ± 3.4 | 13.6 ± 2.8 | 0.26 |
| Nine months postop. | 13.1 ± 3.1 | 13.8 ± 3.0 | 0.45 |
| Twelve months postop. | 14.1 ± 5.4 | 14.8 ± 3.1 | 0.42 |
mmHg, millimeters of mercury; postop., postoperatively.
Unpaired t-test for intraocular pressure.
Table 3 list postoperative complications and adverse events in both groups. During deep sclerectomy, microperforation of trabeculodescemetic membrane was noted without iris prolapse or shallowing of the anterior chamber in 3 eyes (15%). There was less hypotony and choroidal detachment in the deep sclerectomy group than in the subscleral trabeculectomy; hypotony and choroidal detachment were found in none of the eyes (0%) in the deep sclerectomy group and in 4 eyes (20%) in the subscleral trabeculectomy group. While delayed bleb leaks were found 3 eyes (15%) in subscleral trabeculectomy. All bleb were flat and localized.
Table 3.
Surgical complications and adverse events of the studied patients.
| Parameters | Group |
Pa | |
|---|---|---|---|
| Phaco-subscleral trabeculectomy | Phaco-deep sclerectomy | ||
| Posterior lens capsule tear | 1 (5%) | 0 (0%) | 0.36 |
| Vitreous loss | 0 (0%) | 0 (0%) | |
| Perforation of TDM | 0 (0%) | 3 (15%) | 0.75 |
| Shallow anterior chamber | 2 (10%) | 0 (0%) | 0.64 |
| Hyphema (⩾2 mm) | 2 (10%) | 0 (0%) | 0.71 |
| Hypotony (<5 mmHg) | 3 (15%) | 1 (5%) | 0.35 |
| IOP spikes (⩾30 mmHg) | 0 (0%) | 3 (15%) | 0.65 |
| Posterior synechiae | 2 (10%) | 1 (5%) | 0.15 |
| Fibrin formation | 2 (10%) | 1 (5%) | 0.45 |
| Delayed bleb leaks | 3 (15%) | 1 (5%) | 0.71 |
| IOL decentration | 1 (5%) | 1 (5%) | 0.35 |
| Choroidal detachment | 1 (5%) | 0 (0%) | 0.45 |
| Endophthalmitis | 0 (0%) | 0 (0%) | |
TDM, Trabeculodescmetic membrane.
Results of the paired t-test.
Postoperative IOP spike was found in 3 eyes (15%) in the deep sclerectomy group and 0 eye (0%) in the subscleral trabeculectomy group. There were no cases of bleb infection or endophthalmitis in both groups.
Table 4 shows that mean deviation ± SD in Humphrey visual field analyzer testing results at baseline was −17.50 ± 5.041 dB in the subscleral trabeculectomy group, and −18.83 ± 5.61 dB in the deep sclerectomy group (P = 0.64). Improvement of mean deviation was −16.43 ± 4.49 dB at 6 months and −15.92 ± 5.35 dB at 12 months in the subscleral trabeculectomy group, and −16.95 ± 6.07 dB at 6 months and −16.27 ± 6.12 dB at 12 months in the deep sclerectomy group (P = 0.41 at 6 months; P = 0.86 at 12 months). At 12 months, the mean visual field in the subscleral trabeculectomy group was better than that in the deep sclerectomy group, but this improvement was not statistically significant.
Table 4.
Changes in visual field and best-corrected visual acuity in the studied patients.
| Parameters | Group |
Pa | |
|---|---|---|---|
| Phaco-subscleral trabeculectomy | Phaco-deep sclerectomy | ||
| Mean deviation (dB) | |||
| Baseline | −17.50 ± 5.41 | −18.83 ± 5.61 | 0.64 |
| 6 months | −16.43 ± 4.49 | −16.95 ± 6.07 | 0.41 |
| 12 months | −15.92 ± 5.32 | −16.27 ± 6.12 | 0.86 |
| Best-corrected visual acuity | |||
| Base line (%) | |||
| ⩾0.5 | 5 (25%) | 3 (15%) | |
| 0.1–0.4 | 12 (60%) | 13 (65%) | |
| <0.1 | 3 (15%) | 4 (20%) | |
| Mean ± SD (log MAR) | 0.597 ± 0.81 | 0.641 ± 0.28 | 0.68 |
| 12 months (%) | |||
| ⩾1.0 | 14 (70%) | 16 (80%) | |
| 0.5–0.9 | 4 (20%) | 3 (15%) | |
| 0.1–0.4 | 2 (10%) | 1 (5%) | |
| <0.1 | 0 (0%) | 0 (0%) | |
| Mean ± SD (log MAR) | 0.036 ± 0.061 | 0.029 ± 0.063 | 0.36 |
Log MAR, Logarithm of the minimum angle of resolution; SD, standard deviation.
Results of the paired t-test.
In both groups, all eyes showed an increase of more than 0.2 in logarithm of the minimum angle of resolution best-corrected visual acuity at 12 months compared with the preoperative level. At 12 months, the mean best-corrected visual acuity in the deep sclerectomy group was better than that in the subscleral trabeculectomy group, but this improvement was not statistically significant.
Table 5 revealed the bleb outcomes in both groups. In subscleral trabeculectomy group, a type I filtering bleb was present in 15 eyes, a type II filtering bleb was present in 3 eyes, and a type III bleb was present in 2 eyes. But in deep sclerectomy group, a type I filtering bleb was present in 16 eyes, a type II filtering bleb was present in 3 eyes, and a type III bleb in 1 eye. No significant difference in clinical bleb outcome between the two groups. The favourable bleb appearance in group 1: 8 diffuse, 4 flat, and 3 cystic. But, in group 2: 12 diffuse and 4 flat.
Table 5.
Bleb outcomes in the studied patients.
| Parameters | Group |
Pa | |
|---|---|---|---|
| Phaco-subscleral trabeculectomy | Phaco-deep sclerectomy | ||
| No. of eyes | 20 | 20 | |
| Bleb 1 | 15 (75%) | 16 (80%) | 0.31 |
| Bleb 2 | 3 (15%) | 3 (15%) | 0.61 |
| Bleb 3 | 2 (10%) | 1 (5%) | 0.43 |
Bleb 1, Favourable bleb; Bleb 2, intermediate bleb with scar slight; Bleb 3, unfavourable bleb with progressive scarring.
Results of χ2-test.
Table 6 revealed the surgical outcomes at 12 months in both groups. Eighteen eyes (90%) in the subscleral trabeculectomy group and 19 eyes (95%) in the deep sclerectomy group were considered to be successes, whereas 15 eyes (75%) in the subscleral trabeculectomy group and 16 eyes (80%) in the deep sclerectomy group were considered to be complete successes (P = 0.7). Failure was recorded in 2 eyes (10%) in the subscleral trabeculectomy group, and 1 eye (5%) in the deep sclerectomy group (P = 0.4).
Table 6.
Surgical outcomes at 12 months in the studied patients.
| Parameters | Group |
Pa | |
|---|---|---|---|
| Phaco-subscleral trabeculectomy | Phaco-deep sclerectomy | ||
| No. of eyes | 20 | 20 | |
| Overall success | 18 (90%) | 19 (95%) | 0.35 |
| Complete success | 15 (75%) | 16 (80%) | 0.66 |
| Qualified success | 3 (15%) | 3 (15%) | 1.00 |
| Failure | 2 (15%) | 1 (10%) | 0.36 |
| No. of anti-glaucoma medications | 0.1 ± 0.2 | 0.2 ± 0.4 | 0.41 |
Results of χ2-test.
The mean number of anti-glaucoma medication decreased from a preoperative level of 2.1 ± 0.8 to a postoperative level of 0.1 ± 0.2 in the subscleral trabeculectomy group, and from a preoperative level of 2.2 ± 0.6 to a postoperative level of 0.2 ± 0.4 in the deep sclerectomy group.
Complete success, IOP between 6 and 20 mmHg and IOP reduction >30% without additional medical or surgical treatment. Qualified success, IOP between 6 and 20 mmHg with medical treatment or IOP reduction <30%; failure, new glaucoma surgery required.
4. Discussion
A combined technique of cataract extraction and iridencleisis was first described by Birge (1952). Since then, the optimal surgical approach for cataract patients with coexisting glaucoma has been one of the most discussed topics among ophthalmic surgeons.
Cataract surgery in patients with open-angle glaucoma requires careful monitoring of postoperative pressure spikes; combined procedures can reduce the frequency and magnitude of this complications. Many authors have outlined the indications for a combined procedure, but no simple technique without the use of antimetabolites and with a low complications rate has been presented (McCartney et al., 1988).
The IOP lowering potency of combined phacoemulsification, IOL implantation and trabeculectomy in patients with open-angle glaucoma and cataract is well known. Thus, the procedure is currently considered by most ophthalmic surgeons to be the standard technique for the treatment of uncontrolled glaucoma and cataract. Despite refinements in the phacoemulsification trabeculectomy technique, some authors have reported poor bleb formation and IOP control inferior to that achieved after two-stage surgery or filtration surgery performed alone (Lüke et al., 2007).
Recently, variants of non-penetrating surgery, such as deep sclerectomy with or without an intrascleral implant has been combined with phacoemulsification and IOL implantations (Funnell et al., 2005).
In the current study, we compare the surgical outcomes of phaco-subscleral trabeculectomy and phaco-deep sclerectomy with intraoperative mitomycin C (0.4 mg/ml) in eyes with primary open-angle glaucoma.
The mean IOP at the end of follow-up period in subscleral trabeculectomy (14.1 ± 5.4 mmHg) was comparable to that Kobayashi and Kobayashi (2007). While in deep sclerectomy (14.8 ± 3.1 mmHg) was comparable to that reported by Funnell et al. (2005).
At the end of the follow-up period, the mean IOP was reduced by 60.4% (14.2 mmHg versus 23.5 mmHg) for subscleral trabeculectomy, and reduced by 61.4% (14.8 mmHg versus 24.1 mmHg) for deep sclerectomy, thus showing less intraocular pressure reduction of the mean IOP in subscleral trabeculectomy (Lochhead et al., 2003). But there was no significant difference between the two groups.
IOP outcomes of subscleral trabeculectomy and deep sclerectomy with MMC augmentation were found to be similar in this study. This similarity in outcomes has been previously reported (Funnell et al., 2005), but has not been reported using MMC (Gianoli et al., 1999).
Age, gender, and pretreatment medications were evaluated as potential confounding variables at the end of study, and were not found to be significantly associated with any confounder.
Considering the postoperative complications and adverse events; shallow anterior chamber, hypotony, delayed bleb leaks were observed in subscleral trabeculectomy group. This coincide with Funnell et al. (2005). While microperforation of trabeculodescemetic membrane and postoperative IOP spikes were observed in deep sclerectomy group. But there was no significant difference between the two groups.
Mitomycin C augmentation is associated with thin walled blebs and a high incidence of delayed bleb leaks. In this study, the rates of MMC related complications are low. There was no cases of bleb infection or endophthalmitis. This consistent with Funnell et al. (2005).
Hypotony occurred in three patients who underwent selective argon Laser suturelysis after subscleral trabeculectomy, and in one patient who underwent Laser goniopuncture after deep sclerectomy. The frequency of delayed bleb leaks was higher (15%) with subscleral trabeculectomy group than in deep sclerectomy group (5%).
Gianoli et al. (1999) reported a lower incidence of postoperative inflammation and other immediate complications like hyphema and shallow anterior chamber of deep sclerectomy over subscleral trabeculectomy. In this study, there were a low incidence of postoperative complication in both groups, but the possible benefits of deep sclerectomy were offset by a high incidence of intraoperative microperforation of trabeculodescemetic membrane (15%).
Fibrinous anterior chamber inflammation and/or hyphaema were common in subscleral trabeculectomy group. Hyphema was trivial and resolved quickly. The significance of postoperative hyphema to the final outcome of eyes that have undergone antiglaucomatous surgery is a subject of controversy. In the current study, no significant difference with reference to success criteria was observed between eyes that postoperatively showed a hyphaema and those that presented without bleeding. These results coincide with Lüke et al. (2007), and confirms the need to carefully monitor the complications in the immediate postoperative period.
At last follow-up, mean deviation of subscleral trabeculectomy was −15.92 ± 5.32 dB, and of deep sclerectomy was −16.27 ± 6.12 dB. This difference between both groups was not significant (P = 0.86). In addition, improvement of mean deviation in Humphrey visual field analyzer testing was observed in both groups.
The preoperative range of visual acuity in subscleral trabeculectomy was 0.60 ± 0.81 and in deep sclerectomy was 0.64 ± 0.28. At last follow-up, the preoperative range of visual acuity improved in subscleral trabeculectomy to 0.04 ± 0.06, and in deep sclerectomy to 0.03 ± 0.06 at 12 months. No difference were observed in the improvement of visual acuity between the two groups (P = 0.36). This coincide with Funnell et al. (2005). Failure of visual acuity improvement after surgery included advanced glaucomatous optic neuropathy, macular oedema, and myopic shift (Chan et al., 2006).
Considering the postoperative bleb outcome, the current study found that favourable blebs were 75% in subscleral trabeculectomy and 80% in deep sclerectomy, with no statistically significant difference between both groups. But, unfavourable blebs were more in subscleral trabeculectomy with no statistically significant. Postoperative blebs were flat and localized.
The mean number of the preoperative anti-glaucoma medications was 2.1 in subscleral trabeculectomy, and 2.2 in deep sclerectomy to control. At the last follow-up, average number of medications was 0.1 in subscleral trabeculectomy, and 0.2 in deep sclerectomy at 12 months. The difference between two groups was not significant (P = 0.41). When IOP is well controlled by small number of medications, some surgeons prefer to perform cataract surgery alone for the patients coexisting cataract and glaucoma. However, previous study reported that the subscleral trabeculectomy provided good visual acuity with minimal complications and significantly IOP reduction (Mamalis et al., 1996).
In the current study, the overall success rates of achieving IOP <21 mmHg at postoperative 12 months were 90% in the subscleral trabeculectomy group and 95% in the deep sclerectomy group, with no statistically significant difference between both groups. Gianoli et al. (1999) reported that combined surgery using the same target pressure criteria showed qualified success rate at 12 months of 72% for subscleral trabeculectomy and 88% for deep sclerectomy.
In the current study, during phacoemulsification procedure, a bottle height of approximately 100 cm was used rather than 75 cm bottle height frequently used by surgeons in glaucoma patients having surgery by conventional phacoemulsification techniques. The increase in bottle height was necessary to maintain a safe anterior chamber because of the greater resistance to fluid flow through the irrigation chopper and deliberate allowance of some fluid leakage through the phacoemulsification wound for extra-protection against wound burn. Furthermore, the mean duration the operated eye was connected to the bottle was about 5 min. The effect of this on the optic nerve, specially in those with advanced disease is uncertain (Tham et al., 2006).
The anterior chamber remained reasonably stable with this technique. Thus, the procedure of bimanual phacoemulsification appeared to be safe and effective in eyes with coexisting cataract and glaucoma. Advantages include avoiding US trauma to the glaucoma site and that the phacoemulsification corneal wound size is kept to a minimum.
Jampel et al. (2002) have recently performed an evidence based literature review of the effects of techniques on IOP after combined cataract and glaucoma surgery. Their conclusion based on the literature review was that the strongest evidence of efficacy exists for using (1) MMC, (2) separating the incisions for cataract and glaucoma surgery, and (3) removing the nucleus by phacoemulsification.
5. Conclusion
Combined phaco-subscleral trabeculectomy with MMC resulted in excellent IOP control, substantial visual recovery, a decrease in the number of glaucoma medications and, for complications with no significant difference in comparison to phaco-deep trabeculectomy with MMC in patients with primary open-angle glaucoma.
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