Corneal topographic changes after trabeculectomy and deep sclerectomy in patients with primary open angle glaucoma.

INTRODUCTION

Glaucoma is  the second most common cause of worldwide blindness following cataract, and is the main reason of non-reversible visual disability ,mainly because of POAG.¹ Elevated intra-ocular pressure (IOP) is the main risk factor of glaucoma and present glaucoma treatments are entirely pointed to decreasing IOP. ²

Surgery is offered in POAGif there is advanced glaucoma at presentations, especially in younger patients, or if glaucoma is progressing despite 2-3 classes of drugs or after laser trabeculoplasty. Surgery may be offered earlier in the developing world because of lack of availability or affordability of medications, and lack of regular long term access medical care as in remote communities. ³

The golden standard in glaucoma operation still the SST. It is a penetrating filtration operation that efficiently decrease IOP by permitting aqueous drainages via a sclerostomy, with  complete penetrations of the  anterior chamber creating a linking with the sub-conjunctival space.⁴  Following decrease in IOP as well depend on sub-conjunctival bleb formation.⁵ Non penetrating deep sclererectomy

(NPDS) is another, nonpenetrating filtration operation, that preserve the trabeculo‐Descemet membrane.⁶ The former is conventionally accompanied with an elevated rate of complications.⁷

The influence of glaucoma  operations on refraction, predominantly astigmatism, aren’t entirely explained. It is frequent for cases experiencing glaucoma operations to have a shorter time of decreased visual acuity in the earlier post-operative time, and for some cases, this may persevere longstanding. While the variation in vision may be because of the reduction in IOP, numerous reports have investigated the direct impact of glaucoma surgeries on astigmatism, signifying that variations in corneal topography and refractive conditions may have a function. ⁸

PATIENTS AND METHODS

A randomized prospective observational study was carried out from March 2021 to Sept 2021.The study was conducted on 30 eyes of 30 patients suffering from POAG with uncontrolled IOP by maximum tolerable antiglaucoma therapy and operations has been done in in the departments of ophthalmology at Al- Azhar University hospitals.

All patients had normal corneal topographic parameters before operation. The research excepted cases with neo-vascular glaucoma, congenital and juvenile glaucoma, ocular pathology rather than glaucoma such as (corneal dystrophies and uveitis), history of ocular trauma, history of intraocular surgeries, or any systemic diseases that could affect the eye such as uncontrolled diabetes and hypertension. Patients who failed to complete the follow-up examinations after the surgery were also excluded.

Informed agreement was attained from all cases pre any operation. The dangers, profits, substitutes and restrictions of the intervention were explained to them .

Patients were allocated into 2 similar groups:

Group A:15-eye of 15 cases who had SST with adjuvant intra-operative usage of 0.2 mg/ml (MMC) for 2 mins.

Group  B:15 eyes of 15 cases who had NPDS with adjuvant intra-operative usage of 0.2 mg/ml (MMC) for 2 mins.       

Preoperative Assessment

A detailed medical and surgical history,including: history of prior ocular inflammation ,trauma or infection  and  history of bleeding disorders and medications.

Complete ophthalmological examination, including: measurement of  BCVA, slit-lamp  bio-microscopy  , IOP measurements with Goldman applanation tono-metry, dilated fundoscopy and corneal topography by SIRIUS Topographer® (CSO, Firenze, Italy).

Surgical Techniques

All operations have been done underneath Peri bulbar anesthesia. The site of the operation, whether for trabeculectomy or deep sclerectomy was be at superior half of the globe for all eyes. A corneal traction suture was taken  using a silk 8/0 and a conjunctival fornical based flap was made .

In SST with MMC: a superficial scleral flap (6x4mm) half thickness of the sclera  was shaped. Afterward, MMC (0.2 mg/mL) has been utilized underneath the scleral flap and the conjunctiva for 2 mins, and then it was cleaned. A sclerostomy and marginal iridectomy  was created then suturing the scleral flap by 10/0 nylon sutures. Lastly, conjunctival closure with a 8/0 virgin silk sutures. 

In NPDS with MMC: a superficial scleral flap (5x5mm) one-third of the sclera was shaped. Afterward, MMC (0.2 mg/mL) was utilized underneath the scleral flap  and the conjunctiva for 2 mins, and then it was cleaned. The deep flap (4x4mm) was shaped after that it was excised. Schlemm’s canal was unroofed followed  by removal of juxtacanalicular trabeculum. Suturing the scleral flap by 10/0 nylon sutures then conjunctival closure with a 8/0 virgin silk sutures.

Post-operative Follow Up

All cases were inspected on the 1^st day post-operatively, 7 days and then once-a-month for 3-mths. Examinations involved measuring the BCVA, slit-lamp examinations and IOP measurements with Goldman applanation tonometry. Furthermore, corneal topography was obtained using SIRIUS Topographer® (CSO, Firenze, Italy) 3 months post-operatively.

Topical corticosteroid was given heavily then reduced gradually as the clinical course dictated. Topical anti-biotics and  cycloplegic agents  were as well be utilized.

Statistical Analysis:

Collected data analysis was done via SPSS-24.  Quantitative data have been introduced as mean ±SD (data with normal distribution) and median (IQR) (data with abnormal distribution).Qualitative data have been introduced as frequency and percentages.

The next tests were performed:

Independent-samples t-testing: was utilized for comparison among 2 means (normal distribution).

Mann–Whitney U testing: was utilized for comparison among 2 means (abnormal distribution).

A one-way analysis of variance (ANOVA): was utilized for comparison among more than 2 means (normal distribution).

Kruskal Willis test (KW): was utilized for comparison among more than 2 means (abnormal distribution).

Chi-square test: was utilized for comparison among non-parametric data..     

Probability (P-value)

P < 0.05 result has significance.

P < 0.001 result has high significance.

P > 0.05 result has no significance.

RESULTS

This prospective observational  study was carried out from March 2021 to Sept 2021, patients were admitted to Ophthalmology department of Al-Azhar university hospitals at Cairo through the outpatient clinic scheduled for glaucoma filteration surgery.

In this study, 30 patients (with 30 eyes) were allocated into 2 similar groups: (Group A) comprised cases who  had SST with adjuvant intra-operative usage of 0.2 mg/ml Mito-mycin C (MMC) for 2-min, and (Group B) comprised cases who had NPDS with adjuvant intra-operative usage of 0.2 mg/ml MMC for 2 mins.

Corneal topography was obtained using SIRIUS Topographer® (CSO, Firenze, Italy) preoperatively and 3 months post-operatively.

Demographic data:

T: independent sample T testing.                            

X2: Chi-square testing.

Table 1: comparing among the study groups regarding Age and Sex

This table shows nonsignificant change among the study groups regarding demographic data (age and sex).

Clinical data:

1. BCVA:

T: independent sample T test.

Table 2: comparison of BCVA (pre & post) in studied groups.                           

This table shows nonsignificant change among Pre-BCVA and Post-BCVA in group A and group B. (p-value > 0.05)

2. Intraocular Pressure (IOP):

T: independent sample T test.

Table 3: comparison of IOP (pre & post) in studied groups                 

This table shows:

Highly statistical significant (p< 0.001) decreased post IOP (14.07 ± 2.91) when compared with pre IOP (28.13 ± 4.26) in group A.

Highly significant (p< 0.001) decreased post IOP (13.33 ± 2.89) when compared with pre IOP (26.9 ± 3.95) in group B.

Corneal parameters:

1.Flat K (K1) :

T: independent sample T test.

Table 4: comparison of K1 (pre & post) in studied groups.                  

This table shows nonsignificant change (p > 0.05) among (pre) K1 and (post) K1  in group A and group B.

2.Steep K (K2):

T: independent sample T test.

Table 5: comparison of K2 (pre & post) in studied groups.

This table shows:

Highly significant increased post K2 (44.29 ± 0.57) when compared with pre K2 (43.43 ± 0.46) in group A.

Nonsignificant change among K2 (pre) and K2 (post) in group B.

 3. Average Keratometry (Avg K):

T: independent sample T test. 

Table 6: comparison of Avg K (pre & post) in studied groups.            

This table shows nonsignificant difference among AVG K (pre) and AVG K (post) in group A and group B.

4.Apical Keratometry Front (AKF):

T: independent sample T test.

Table 7: comparison of AKF (pre & post) in studied groups.                               

This table shows nonsignificant difference among AKF (pre) and AKF (post) in groups A and B.

5.Corneal Astigmatism :

T: independent sample T test.

Table (8): comparison of astigmatism (pre & post) in studied groups.                   

This table shows:

Highly significant increased astigmatism post (2.38 ± 0.7) when compared with astigmatism pre (1.06 ± 0.75) in group A.

Statistically significant (p-value = 0.005) increased astigmatism post (2.3 ± 0.61) when compared with astigmatism pre (1.61 ± 0.62) in group B.

6.Axis Of Flat k:

T: independent sample T test.

Table 9: comparison of axis (pre & post) in studied groups.                

This table shows nonsignificant change among axis (pre) and axis (post) in group A and group B.

Amount of Changes in studied parameters (Δ):

MW: Mann Whitney U testing.

Table 10: comparing among the study groups regarding changes in studied parameters.                     

This table shows:

Highly statistical significant increased Δ K1 (0.47 ± 0.09) in group A when compared with Δ K1 (0.22 ± 0.09) in group B.

Highly statistical significant (p-value < 0.001) increased Δ K2 (0.86 ± 0.18) in group A when compared with Δ K2 (0.46 ± 0.08) in group B.

Highly statistical significant (p-value < 0.001) increased Δ astigmatism (1.32 ± 0.13) in group A when compared with Δ astigmatism (0.69 ± 0.1) in group B.

Nonsignificant change among group A and group B regarding Δ (BCVA, IOP, AVG K and AKF).