A Comparative Study to Evaluate The Role of Amniotic Membrane Transplant and Anterior Stromal Puncture in Painful Pseudophakic Bullous Keratopathy

Purpose: To evaluate the role of Anterior stromal puncture (ASP) and Amniotic membrane transplant (AMT) in providing symptomatic relief to the patients of painful pseudophakic bullous keratopathy (PBK). Methods: 40 patients of PBK were divided into two groups of 20 each. Group A underwent AMT and Group B underwent ASP. Ocular pain score was assessed by using the Visual Analogue Scale preoperatively and post operatively. Results: This prospective study analysed ocular pain based on visual analogue score (VAS). At the end of 12 weeks, the final VAS was Grade 1 in 14 patients (70%) in both the groups, Grade 2 in 5 patients (25%) in group A and in 3 patients (15%) in group B, Grade 3 in 1 patient (5%) in group A and in 2 patients (10%) in group B and Grade 4 in 1 patient (5%) in group B. Corneal surface regularity was disturbed only in 20% and maintained in 80% of Group A patients. In group B, corneal surface regularity was disturbed in 75% and maintained in only 25% patients. At the end of 12 weeks recurrence of bullae was observed in 20% in group A and in 15% in group B. Conclusion: AMT and ASP are equally effective procedures for management of symptomatic PBK in patients with poor visual potential. Both AMT and ASP lead to amelioration of clinical symptoms. AMT has slightly better clinical outcome than ASP but ASP is an OPD procedure and inexpensive.


Introduction
Bullous keratopathy is a painful condition in which small vesicles or bullae are formed on the cornea due to endothelial dysfunction. Endothelial failure leads to loss of corneal stromal deturgescence, an increase in stromal hydration, damage to bowman's layer, loss of epithelial basement membrane and alteration of the glycosaminoglycan component of stroma. 1 When there is good visual potential, Penetrating keratoplasty or endothelial keratoplasty may alleviate pain and restore vision. 2,3 When there is limited visual potential and corneal transplantation is no longer a feasible choice, ocular pain and surface breakdown can be treated with bandage contact lens, anterior stromal puncture, 4 annular keratotomy, 5 epikeratophakia, 6 excimer laser phototherapeutic keratetectomy, 7 or a conjunctival flap. 8 Amniotic membrane is the innermost layer of placenta, 0.2 to 0.5 mm in thickness. It is believed to be non-immunogenic due to its low antigenicity. It can be used as an alternative to conjunctival flap in treating persistent corneal defects with ulcerations. 9 When used for corneal 10 and conjunctival 11 reconstruction Amniotic membrane has also been shown to facilitate epithelialisation and to reduce inflammation and scarring. Anterior stromal puncture involves multiple micro punctures. The subsequent healing response leads to the alteration of extracellular matrix and enhances attachment of epithelial cells to underlying connective tissue at the puncture sites. 12 Majority of the patients with painful bullous keratopathy require keratoplasty. As the donor cornea is not available in adequate quantity so the patients of PBK have to wait for a long time. Therefore, the present study was planned to evaluate the role of AMT and ASP in providing symptomatic relief in such patients.

Material and Methods
The present prospective study was conducted on 40 patients of pseudophakic bullous keratopathy. All the patients were divided into two groups of 20 each. Group A underwent amniotic membrane transplantation and Group B underwent anterior stromal puncture. Ocular pain score was assessed by using the Visual Analogue Scale with following grades. 13 Grade 1 = None Grade 2 = Mild (requiring no medication) Grade 3 = Moderate (requiring occasional medication) Grade 4 = Severe (requiring constant medication) Slit lamp examination of patient's both the eyes was done to look for epithelial bullae, stromal edema and descemets folds. Specular microscopy of both the eyes was done using Topcon SP 3000P specular microscope. Fresh human amniotic membrane was obtained from the department of obstetrics and gynaecology of our institute after elective caesarean deliveries of those mothers who had been screened for HIV, HBV, HCV and syphilis during their regular follow up in antenatal clinic. The maternal donors were again screened serologically for HIV, HBV, HCV and syphilis at the time of caesarean section. The human fresh amniotic membrane was prepared using the standard protocol proposed by Kim. 14 It was used within 24 hours for transplantation. AMT and ASP in diagnosed patients of pseudophakic bullous keratopathy were done in eye OT under aseptic conditions.
Amniotic membrane transplant-Following peri-bulbar anaesthesia, the corneal epithelium was debrided with a sponge up to limbus. The prepared amniotic membrane was placed over the entire cornea with the basement membrane

Results
In the present study at the end of 12 weeks, improvement from Pre-Operative visual acuity was observed in 50% patients in group A and in 40% in group B. No change from      pre-operative visual acuity was observed in 45% patients in both the groups and deterioration was observed in 5% patients in group A and 15% in group B although visual rehabilitation was not the objective of this study and the difference between the two groups was not statistically significant. (Table 1)

Figure 3.2: weeks after AMT
In our study patients were observed for corneal surface regularity at the end of the study period of 12 weeks. Corneal surface regularity was disturbed only in 20% and maintained in 80% of Group A patients. In group B corneal surface regularity was disturbed in 75% and maintained in only 25% patients. This difference was statistically significant with a p value of less than 0.05. (Table 2)

Visual Analogue Score
At the end of 12 weeks, the final VAS was Grade 1 in 14 patients (70%) in both the groups, Grade 2 in 5 patients (25%) in group A and in 3 patients (15%) in group B, Grade 3 in 1 patient (5%) in group A and in 2 patients (10%) in group B and Grade 4 in 1 patient (5%) in group B. In group A none of the patients had VAS of Grade 4 at the end of study period. This difference was statistically non-significant. (Table 3)

Epithelial Bullae
By the end of 1 week, complete regression of bullae was observed in all the patients in both groups. However, at the end of 12 weeks recurrence of bullae was observed in 20% in group A and in 15% in group B. (Table 4) There was no statistically significant difference between the two groups. (Figure 3.1, 3.2, 4.1, 4

Discussion
Bullous keratopathy is a result of corneal endothelial dysfunction. In healthy cornea, endothelial cells prevent the tissue from excess fluid absorption, pumping it back into the aqueous. When endothelial cell count falls too low, the fluid moves anteriorly in the stroma and epithelium. As fluid accumulates between the basal epithelial cells, bullae are formed and they undergo painful rupture. The bullae not only cause pain but also impair vision. Penetrating keratoplasty and more recently Descemet Stripping Endothelial keratoplasty (DSEK) is treatment of choice for PBK. However, ASP and AMT are also useful techniques for Original Article managing painful PBK in eyes with limited visual prognosis. These procedures alter the pathogenic mechanisms of PBK.
One of the physiological factors that draws fluid into the stroma in PBK, is the stromal osmotic pressure rendered by the extracellular matrix components. The amniotic membrane with its avascular stromal matrix, thick continuous basement membrane and thick epithelial monolayer may act as a barrier when incorporated in the subepithelial location. Another factor that contributes to the formation of bullae is poor epithelial attachment. Immune histological evidence suggest that key matrix proteins such as fibronectin, laminin and type 4 collagen, which are essential for epithelial anchorage to the stroma, are altered in PBK. 1,12 Basal membrane of Amniotic membrane acts as a scaffolding, encouraging epithelial differentiation and migration. Its basement membrane also contains collagen types IV, V and VI as well as fibronectin and laminin 15 and this may help to establish a favourable micro-environment for the epithelial basement membrane adhesion complexes. 16 In our study at the end of 12 weeks 70% of the eyes in which AMT was done had amelioration of clinical symptoms of pain, photophobia, watering and foreign body sensation with VAS grade 1 . In a study conducted by Pires et al. during the follow up period of 33.8 weeks (3 -96 weeks) after AMT, 43 (90%) of 48 eyes with intolerable pain preoperatively became pain free post operatively. 17    performing a non-preserved human AMT in 9 eyes. Mean follow up time was 40 weeks. Symptoms of PBK resolved completely in 8 (88%) patients and partially in 1 patient. 18 Anterior stromal puncture involves multiple micro punctures. The subsequent healing response leads to alteration of extracellular matrix by increasing the expression of fibronectin, laminin and collagen IV at the puncture sites. This enhances the attachment of epithelial cells to the underlying connective tissue at the puncture sites. The subsequently formed scar tissue has low osmotic pressure and therefore, it acts as a barrier to fluid flow. 1 In our study at the end of 12 weeks following ASP 70% of the patients had VAS of grade 1 while rest of the 30% had VAS between grade 2 to 4. In a similar study by Cormier et al., 27 patients of PBK, who underwent ASP, a significant reduction in pain was noted after 3 months of treatment. 4 In another study by Shridhar et al. in 28 patients of PBK, complete relief was observed in 20 patients (71.4%), whereas 8 patients (28.6%) experienced mild symptoms such as tearing and occasional pain. 19 It can be concluded that both AMT and ASP are suitable options in patients with painful PBK. AMT can be done when facilities for surgery are available, patient can afford treatment and can follow up regularly whereas ASP is preferred where facilities are deficient, patient is poor and non-compliant.