Title Page

Title: Surgical Outcome of Scleral Tunnel Cataract Surgery.

Authors: Yasser Mohamed Khalifa (1), Khaled Abd Al Salam Zaky (2)

Author: (1)

Academic degree: Doctorate of Ophthalmology

Academic affiliation: Lecturer of Ophthalmology, Faculty of Medicine, Suez Canal

University, Egypt.

Address: Ophthalmology department, Faculty of Medicine, Suez Canal University

Hospital, Ismailia, Egypt.

Telephone: 0020114039301

e-mail: yakhalifa@hotmail.com

Author: (2)

Academic degree: Doctorate of Ophthalmology

Academic affiliation: Assistant professor of ophthalmology, Faculty of Medicine,

Suez Canal University, Egypt.

Address: Ophthalmology department, Faculty of Medicine, Suez Canal University

Hospital, Ismailia, Egypt.

Telephone: 0020145581511

e-mail: khaledzaky11@hotmail.com

Corresponding author: Yasser Mohamed Khalifa,

Telephone: 0020114039301

Address: Ophthalmology department, Faculty of Medicine, Suez Canal University

Hospital, Ismailia, Egypt.

E mail: yakhalifa@hotmail.com

Word count in manuscript: 1715

Word count in abstract: 191

The authors indicate no financial support or financial conflict of interest involved

in design of study; collection, management, statistical analysis, and interpretation

of data; collection of data; preparation and writing of the article; and critical

revision of the article.

Concerning the patients involved in this article, Informed consents were taken

conformed to local laws and in compliance with the principles of the Declaration

of Helsinki.

ABSTRACT:

PURPOSE: To evaluate the surgical outcome of scleral tunnel cataract surgery

regarding postoperative visual outcome, intraoperative complications,

postoperative complications and surgically induced astigmatism.

MATERIALS & METHODS: An interventional non controlled case series study

was conducted at Suez Canal University Hospital. Seventy patients underwent

cataract surgery through superior scleral tunnel approach. Postoperative outcomes

including visual acuity, slit lamp examination and keratometry were assessed for

three months postoperatively. Intraoperative and postoperative complications were

recorded.

RESULTS: At 3 months postoperatively best-corrected visual acuity was achieved

as 6/9 or better in 84.2% patients and as 6/18 or better in 97.1% patients. The main

intraoperative complication was posterior capsular tear in 3 eyes (4.2%). While

postoperative complications included transient corneal edema in 5 eyes (7.1%),

postoperative uveitis in 3 eyes (4.2%) and posterior capsule opacification in 2 eyes

(2.8%). The mean corneal astigmatism was 1.9 + 0.8D preoperatively and 2.3 +

0.6 D at 3 months postoperatively with surgically induced astigmatism of 0.4 + 0.3

D.

CONCLUSION: Scleral tunnel cataract surgery achieves good visual outcomes at

low cost with minimal complications. The technique is easy and safe especially

with mature and hyper mature cataracts when phacoemulsification is considered

difficult.

KEY WORDS: Cataract surgery, Scleral Tunnel, Surgical outcome, surgically

induced astigmatism.

Introduction

Cataract extraction constitutes the largest surgical workload in ophthalmic units

throughout the world and is one of the most cost effective of all surgical

interventions (1).

The two main objectives of modern cataract surgery are to minimize surgically

induced astigmatism and to achieve rapid visual rehabilitation. Clear corneal or

scleral tunnel incisions of the minimum possible size are the key to achieving these

objectives (2).

Phacoemulsification is considered the standard of care for cataract surgery in the

world, however, the technique has a prolonged and sometimes traumatic learning

curve and secondly, it requires expensive and complex equipments (3, 4).

Kansas, 1988 first reported the non- phacoemulsification small incision extra

capsular cataract extraction and intraocular lens implantation (5). Manual small

incision cataract surgery (SICS) provides preservation of the limbal anatomy,

faster recovery, minimum learning curve, cost effectiveness. Also, it can be

performed easily for mature and hypermature cataract, hard nuclei and with

incomplete capsulorrhexis (6, 7).

Material and Methods

An interventional non controlled case series study was conducted in the

Ophthalmology Department, Suez Canal University Hospital between October

2009 to December 2010. Seventy patients undergoing cataract surgery were

randomly selected for manual SICS. The conditions likely to influence the visual

prognosis like previous intraocular surgery, corneal opacity, uveitis,

glaucoma/ocular hypertension, exfoliation syndrome and diabetes mellitus were

excluded from the study.

Complete preoperative ophthalmic examination was done including automated

keratometery (Nidek ARK - 510, Nidek Inc, Japan) to measure the pre-operative

corneal astigmatism and intraocular lens.

Intervention

The surgery was performed under peribulbar anesthesia. After making a fornix

based conjunctival flap, a frown incision 6.5 mm long and 1/2 thickness of sclera

was made about 1 mm behind the limbus at 12 o‘clock position. A cresent blade

was used for fashioning the tunnel extending into 1-1.5 mm in the clear cornea. At

the internal incision, dissection was extended laterally 0.5-1 mm to create the

pockets on both sides. Capsulotomy (continuous capsulorrhexis or cane-opener)

was done using a cystitome fashioned from a 26 G needle. Side port incision was

performed in the clear cornea at about 9 o‘clock position with 20 G MVR. Anterior

chamber was entered with 3.2 mm keratome through the scleral tunnel and the

tunnel was extended laterally throughout the length of the internal lip of the

incision so the wound act as corneal valve. Hydrodissection was performed

through the tunnel wound and the nucleus was dislocated into the anterior chamber

using a viscoelastic substance. Based on hydrodynamic expression, using an

irrigating vectis, the nucleus was expressed out. After cleaning the residual cortex

using irrigation/Aspiration cannula through the side port incision, a posterior

chamber intraocular lens was implanted in-the-bag.

Finally the main incision was secured with single figure of 8 suture and the side

port incision was hydrated and the conjunctiva was ballooned with subconjunctival

injection of garamycin and fortacortin combination to cover the main incision

(Figures 1 & 2 illustrate the technique of scleral tunnel cataract surgery in mature

and hypermature cataract).

Post-operatively, patients’ received topical antibiotic and steroid eye drops (4

times/day) for a minimum period of 4 weeks.

Follow-up was done at 1st day, 1st week, 3rd week, 6th week and 3rd month

postoperatively.

Main outcome measures

Surgical outcome following SICS including intraoperative complications, visual

outcome, corneal astigmatism and postoperative complication were recorded.

Corneal astigmatism was calculated from the difference between the steepest and

flattest keratometric readings

All collected data were computed for statistical analysis. Continuous variables

were described as mean ± standard deviation (SD). Comparisons between

preoperative and postoperative data were performed by paired t tests for

continuous data and Fisher exact probability test was used for non parametric data.

P value <0.05 was considered statistically significant.

Results

The study included 70 patients 37 (52.9%) male and 33(47.1%) female with mean

age 63 + 8.6 years (range 52 - 77 years). The study included 70 patients with

varying grades of senile cataract divided into 21 (30%) immature, 36 (51.5%)

mature and 13 (18.5%) hypermature cataract.

Visual outcome:

All patients had improved postoperative uncorrected visual acuity with 15 eyes

(21.4%) achieving 6/9 or better and 57 eyes (81.4%) achieving 6/18 or better by

the end of follow up period. The best corrected visual acuity was improved with 59

eyes (84.2%) achieving 6/9 or better and 68 eyes (97.1%) achieving 6/18 or better

by the end of follow up.

The commonest cause of an uncorrected vision was astigmatism. Other causes

included posterior capsule opacification, age related macular degeneration, myopic

degeneration and cystoid macular edema.

Intraoperative complications:

Intraoperative complications included posterior capsular tear in 3 eyes (4.2%), iris

trauma in 1 eye (1.4%) and mild hyphema in 1 eye (1.4%).

Posterior capsule tear was noted in 3 eye with vitreous prolapsed in only one eye

which was managed by anterior vitrectomy and sulcus fixated intraocular lens. Iris

trauma occurred in one eye with large hypermature cataractous lens during

delivery and was managed successfully with repositioning of the iris. Hyphema

from the lips of the scleral tunnel occurred in one eye and was managed

successfully with intracameral air tamponade and cauterization.

Postoperative complications:

Postoperative complications included transient corneal edema in 5 eyes (7.1%),

postoperative uveitis in 3 eyes (4.2%) and posterior capsule opacification in 2 eyes

(2.8%). There was no reported vision threatening complications in the study group.

Transient corneal edema occurred in 5 eyes and postoperative uveitis in 3 eyes

which resolved gradually within 10 days with intense medical treatment. Posterior

capsule opacification was noted in 2 eyes which required YAG laser capsulotomy

in the 2 postoperative month.

Surgically induced astigmatism:

The mean corneal astigmatism was 1.9 + 0.8D preoperatively and 2.3 + 0.6 D at 3

months postoperatively with mean surgically induced astigmatism of 0.4 + 0.3 D.

there was statistically significant difference between the preoperative and

postoperative corneal astigmatism (P value 0.008).

Classification of the corneal astigmatism revealed that preoperatively there were

59 (84.2%) eyes from the total study group with varying degrees of corneal

astigmatism; classified as 14(23.7%) eyes with the rule, 27 (45.8%) eyes against

the rule and 18(30.5%) eyes oblique astigmatism.

Postoperatively, there were 65 (92.8%) eyes from the total study group with

corneal astigmatism; divided as 11(16.9%) eyes with the rule, 41 (63.1%) eyes

against the rule and 13 (20%) eyes oblique astigmatism.

There was a statistically significant difference between the preoperative and

postoperative corneal astigmatism regarding the total study group (P value

0.000001). However, the noted shift for against the rule astigmatism was

statistically insignificant between the preoperative and postoperative results (P

value 0.15).

Discussion

Cataract is a major cause of blindness worldwide. Although phacoemulsification is

the main line of treatment, it will not be suitable for many patients due to lack the

funds for treatment and delayed presentation with hard cataract.

Manual small incision surgery through a scleral tunnel may be a more appropriate

technology for such settings. It needs similar equipment and facilities like the

conventional extra capsular cataract extraction that are readily available in most

centers (7, 8).

In this case series good visual outcomes with minimal complications have been

reported following scleral tunnel cataract surgery comparable to other studies,

however accurate comparisons should be based on the criteria of patient selection

regarding the age, level of cataract and other ocular conditions.

Ahmed and coworkers reported their series of 70 eyes with 60.8% of patients

obtained 6/12 or better vision in the first 3 weeks only. They attributed quick visual

restoration to little inflammation and less surgically induced astigmatism (SIA)

following SICS. They stated that their patients had fewer complaints regarding

ocular discomfort in terms of pain, foreign body sensation and redness following

SICS and complications like posterior capsular rupture, dropped nucleus and

bullous keratopathy are less common with SICS. They reported 5 patients, whose

best corrected visual acuity was less than 6/12 at 12 weeks, the causes were

posterior capsular opacification in 2 patients and age related macular degeneration,

cystoid macular edema and central choroiditis in 1 patient each (2).

Guzeh and coworkers in their study on 200 eyes undergoing small incision manual

extra capsular cataract surgery found that 90% of eyes achieved a final best

corrected visual acuity of at least 6/12. In addition, patients had a faster visual

recovery and lower incidence of ocular inflamation particularly fabrinous iritis (9).

Hepsen and coworkers also achieved a post-operative best spectacle corrected

visual acuity of 6/9 or better in 83% of eyes undergoing small incision extra

capsular cataract surgery (10).

Khanday and coworkers, in their study stated that the manual SICS group clearly

demonstrated an early visual rehabilitation when compared to the standard ECCE

group. Most of the patients in the former group had attained good working vision

within three weeks post operatively. The fundamental difference between the two

techniques resulting in rapid visual recovery is the induced astigmatism which is

far less in the SICS group (11).

Surgically induced astigmatism was attributed to several factors like incision size,

sutures, wound healing, wound position and configuration. The incision is a major

cause of these shifts. This effect is directly related to the length, location and depth

of the incision (12, 13, 14, 15).

In our series there was a statistically significant difference between the

preoperative and postoperative corneal astigmatism regarding the total study group

with shift toward against the rule astigmatism postoperatively. However, that noted

shift was statistically insignificant between the preoperative and postoperative

results.

Ahmed and coworkers found that 74% of patients demonstrated against the rule

shift in post operative astigmatism and which is explained by sutureless incision.

These changes in the curvature are explained by the law of “elastic domes” and

which states that for every change in curvature in one meridian, there is an even

and opposite change 90 degree away (2).

Henning and coworkers in their study on 500 patients undergoing sutureless

cataract surgery found that 85.5% of the eyes had against the rule astigmatism and

which was the major cause of uncorrected visual acuity of less than 6/18 (16).

The difference between our results and the previous studies could be attributed to

the single suture that was added to secure the wound; it might partly neutralized

the flattening effect of the incision and reduced the shift toward against the rule

astigmatism in our patients.

In conclusion; scleral tunnel cataract surgery achieves good visual outcomes at low

cost with minimal complications. However further work needs to be done to reduce

post operative astigmatism which still exists to be the main cause of poor

uncorrected visual acuity.

References

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Legends of figures

Figure 1: Scleral tunnel cataract surgery for mature senile cataract

Video captured images of scleral tunnel cataract surgery for mature cataract

illustrating the steps of surgery; construction of the scleral tunnel (top left),

dislocating the nucleus into the anterior chamber (top right), extraction of the

nucleus (bottom left) and removing viscoelastics after IOL implanataion (bottom

left).

Figure 2: Scleral tunnel cataract surgery for hypermature senile cataract

Video captured images of scleral tunnel cataract surgery for hypermature cataract

illustrating the steps of surgery; construction of the scleral tunnel (top left),

dislocating the nucleus into the anterior chamber (top right), extraction of the

nucleus (bottom left) and removing viscoelastics after IOL implanataion (bottom

left).