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A comparative study of free conjunctival autograft versus conjunctival autograft with stem cell transfer in primary pterygium.

INTRODUCTION: Pterygium is a triangular fibrovascular subepithelial ingrowth of degenerative bulbar conjunctival tissue over the limbus onto the cornea (1).

The first described surgical removal of a pterygium was by Susruta 2. Since then, a considerable number of surgical techniques have been described for its management: simple resection or bare sclera technique, (3,4) avulsion, (5) removal and primary closure, (3,6,7) pterygium head transplant, (8-10) concomitant beta irradiation (13), conjunctival autograft (15,19), limbal conjunctival autograft 15-18, and the use of amniotic membrane with and without conjunctival grafts 20 . Also attempted are adjunctive therapies aiming at suppressing regrowth of subconjunctival tissue, such as--beta irradiation, thiotepa, and topical postoperative mitomycin C (21, 22) ; these are associated with complications such as disfiguring skin depigmentation, cataract formation, severe secondary glaucoma, uveitis, corneal perforation, and scleral necrosis, resulting in perforation and endophthalmitis (11-13). Thus, compared with other techniques, conjunctival autografting after pterygium excision is associated with lower rates of recurrence and complications.

In 1985, Kenyon et al (19) described their procedure of conjunctival autograft for the management of recurrent or advanced pterygium with a low recurrence rate of 5.3%. Although more time consuming, this surgical technique was found to be safe and effective in reducing the number of recurrences while avoiding the risk of potentially serious complications (23,24). Most reports also advocate a thin graft devoid of Tenon's fascia but one which is large enough to completely cover the bare scleral defect (19). However, studies performed in high-risk populations (people residing in tropical countries, working outdoors) observed higher recurrence rates using the same surgical technique (25).

Once it was established that corneal epithelial stem cells are located at the limbus, it was suggested that healthy limbal epithelium acts as a junctional barrier to conjunctival migration onto the corneal surface (26,27). Also, pterygium was speculated to represent a "local limbal stem cell deficiency (LSD]" (28). Accordingly, inclusion of limbal epithelium in the conjunctival graft for pterygium surgery would achieve better anatomic and functional reconstruction after pterygium removal and, by restoring barrier function of the limbus, could reduce recurrence. Limbal autograft transplantation has been used successfully for treating chemical, thermal, or contact lens associated corneal injury (29). The method has been reported to be more effective for establishing a healthy ocular surface than conjunctival transplantation in rabbits (30). Recent studies have reported the effectiveness of limbal conjunctival autograft transplantation in the prevention of recurrence of pterygia (31,32).

Recurrence is defined and graded in the following manner: Grade 1 indicates that the appearance of the operated site was not different from the normal appearance. Grade 2 indicates some fine episcleral vessels in the excised area extending up to, but not beyond, the limbus and without any fibrous tissue. Grade 3 indicates additional fibrous tissues in the excised area that did not invade the cornea. Grade 4 represents a true recurrence, with fibrovascular tissue invading the cornea.

AIMS & OBJECTIVES:

1. To know the outcome of free conjunctival autograft versus autologous limbal stem cell graft surgery.

2. To study the outcome in terms of cosmetic appearance and visual acuity.

3. To study the complications in terms of recurrence.

MATERIALS AND METHODS:

INCLUSION CRITERIA: Patients with primary pterygium with less than 3 mm encroachment upon the cornea (Grade I & II).

EXCLUSION CRITERIA:

1. Primary pterygium with more than 3 mm encroachment upon the cornea (Grade III).

2. Recurrent pterygium.

3. Pseudo pterygium

4. Preexisting ocular surface and intra ocular diseases were excluded.

The study was conducted at K.R.HOSPITAL from Jan 2012 to June 2012, 100 patients who fulfill the inclusion criteria were selected and they were divided into two groups (Group A & B). Routine ophthalmic examinations including visual acuity, slit lamp examination, fundus evaluation and keratometric readings were taken in all patients.

Preoperatively 45% had Astigmatism. Out of which 44.4% (20 eyes) had WTR astigmatism, 35.6% (16 eyes) had oblique, 20% (9 eyes) had ATR astigmatism.

50 patients underwent pterygium excision with free conjunctival auto grafting using 10-0 nylon sutures, 50 patients underwent pterygium excision with conjunctival auto grafting with stem cell transfer using 10-0 nylon sutures.

The operations were performed under peribulbar anesthesia with lidocaine hydrochloride 2% and 0.5% bupivacaine. A solid lid speculum was used to expose the surgical field. Superior rectus bridle suture was put to improve exposure. Westcott scissors were used to excise the pterygium from the surrounding conjunctiva. The body of the pterygium was lifted from the conjunctival surface, and the head of the pterygium was then avulsed and the remaining tissue was scraped from the corneal surface with a No 15 blade. Any episcleral scarring was removed.

At this stage, using a random number table with blocked randomization, patients were randomly assigned to undergo either free conjunctival autograft transplantation (group A) or limbal-conjunctival autograft transplantation (group B). The main difference between the two groups was inclusion of the limbal stem cells in the conjunctival autograft in group B.

The conjunctival graft was dissected from the superotemporal bulbar conjunctiva. A caliper was used to measure the area of conjunctiva and limbal stem cells were resected with the pterygium. The intended graft area (1 mm larger than the area resected in the pterygium site) was marked in the superotemporal zone with a gentian violet marker pen. Dissection began with the use of conjunctival scissors and forceps from the fornix to approximately 1.5 mm from the limbus, keeping Tenon's capsule intact. In the case of limbal-conjunctival transplantation (group B), a crescent knife was used to create a superficial circumferential incision in the cornea 0.5 mm from the limbus, equal in length to the resected limbus. This step was performed before harvesting the conjunctival flap. As soon as the conjunctival part was dissected, limbal dissection was carried forward to include 0.5 mm of peripheral cornea with the conjunctival graft. At the limbus, the graft was flipped over on to the cornea and the tenon's attachments at the limbus were meticulously dissected. The flap was then excised with approximately 20% of corneal stroma, extending 0.5 to 1 mm in to the clear cornea, using a Vannas scissors, taking care to include the limbal tissue. The free graft was placed in the correct orientation onto the scleral bed.

The limbal and conjunctival sides of the graft were sutured to the recipient bed with 4-6 interrupted 10.0 nylon sutures. The area of the graft was left with Tenon's capsule exposed. 0.5 ml Subconjunctival dexamethasone and gentamicin was administered.

After surgery, a pressure patch was used for the first 24 hours, and patients were treated with topical dexamethasone and tobramycin eye drops on a tapered regimen (six times daily, tapering over 2 months) and flurometholone eye ointment (at bedtime for 3weeks). Patients were evaluated and photographed on postoperative days 1, 7, 14, 30 and 45, then at 6 months.

Change in astigmatism was documented on 45th postop day.

Recurrence of pterygia was defined as any fibrovascular proliferation encroaching more than 1 mm onto the cornea from the original pterygium site.

RESULTS:

Table-1: Demographic Data of the Study (n=100)

VARIABLE            NUMBER   %

SEX

Male                  68     68
Female                32     32

TYPE OF PTERYGIUM

Grade I               31     31
Grade II              69     69

MEAN AGE            42.6 yrs


1. Astigmatism decreased

Table 2: Preoperative astigmatism GROUP A

Amount of astigmatism   WTR   ATR   OBLIQUE

0.5-0.75 D               6     3       5
0.75-1.5 D               4     1       3
                        10     4       8

Table 3: Preoperative astigmatism GROUP B

Amount of astigmatism   WTR   ATR   OBLIQUE

0.5-0.75 D               6     3       5
0.75-1.5 D               4     2       3
                        10     5       8

Table 4: Post operative Astigmatism GROUP A

Amount of astigmatism   WTR   ATR   OBLIQUE

0.5-0.75 D               4     2       4
0.75-1.5 D               2     1       1
                         6     3       5

Table 5: Post operative Astigmatism GROUP B

Amount of astigmatism   WTR   ATR   OBLIQUE

0.5-0.75 D               5     2       4
0.75-1.5 D               2     0       2
                         7     2       6

Table 6: Comparison of Preoperative and postoperative
Astigmatism (p value = 0.909)

Astigmatism   Group A            Group B

              Pre op   Post op   Pre op   Post op

0.50-0.75 D   14       10        14       11
0.75-1.5 D    8        4         9        4


(p value = 0.909)

The study showed decrease in astigmatism of all 3 types (WTR, ATR, and Oblique). The decrease in astigmatism was irrespective of whether the patients belonged to group A or B i.e. no significant difference in decrease in astigmatism in the two groups (p value = 0.909).

2. The cosmetic appearance was ge nerally good.

3. Complications developed were as follows: 4 patients (4%) developed granuloma formation (2 from Group A and 2 from Group B); 6 patients(6%) had recurrence (3 from group A and 3 from group B).

DISCUSSION: In our prospective, randomized study, we found that both techniques were effective, with no statistically significant difference (p value =0.909) in terms of decrease in astigmatism or recurrence. Our study included 100 patients with pterygia surgically treated with conjunctival and limbal stem cells autograft. The results showed that after a period of follow up of 6 months, 90% of cases were successfully treated without recurrence of pterygial growth or significant complications. Only 6% of cases showed recurrence of pterygial growth.

Since the report by Kenyon et al (9) of low recurrence associated with conjunctival autografting after pterygium excision, the method became one of the procedures of choice for the surgical management of pterygium. However, prospective, randomized studies of conjunctival autografting after pterygium have shown higher recurrence rates (16%-39%) in high-risk populations. (33)

The recurrence rate reported in our study was 6% is comparatively les as compared to the other similar studies. The low recurrence rate is encouraging considering the strict definition of recurrence used and the high rate of recurrence in the population. An adequately sized and shaped graft that fits well in the host bed is also important. The graft is dissected as thin as possible avoiding button holing. The use of peribulbar anaesthesia is also important as the longer duration of the procedure (Approximately 45 minutes) can be comfortably tackled without compromising the surgical technique. There was reduction in preexisting astigmatism. The cosmetic results were fairly acceptable.

CONCLUSION: Despite the fact that limbal stem cell containing conjunctival autograft and free conjunctival autograft transplantation are time consuming procedures, both are safe and equally effective techniques for the treatment of pterygia. Hence, probably the 'barrier effect' of the autograft is the one responsible for the decrease in recurrence rate rather than the limbal stem cells transferred during the procedure.

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K. Satish (1), D.N. Prakash (2), Meghana Tanwar (3), Madhumita Gopal (4), Savita Patil (5), Ambika A Acharya (6), Amar Kulkarni (7), Mohan Setlur (8)

PARTICULARS OF CONTRIBUTORS:

(1.) Associate Professor, Department of Ophthalmology, K.R. Hospital, Mysore Medical College and Research Institute, Mysore.

(2.) Assistant Professor, Department of Ophthalmology, K.R. Hospital, Mysore Medical College and Research Institute, Mysore.

(3.) Resident, Department of Ophthalmology, K.R. Hospital, Mysore Medical College and Research Institute, Mysore.

(4.) Resident, Department of Ophthalmology, K.R. Hospital, Mysore Medical College and Research Institute, Mysore.

(5.) Resident, Department of Ophthalmology, K.R. Hospital, Mysore Medical College and Research Institute, Mysore.

(6.) Resident, Department of Ophthalmology, K.R. Hospital, Mysore Medical College and Research Institute, Mysore.

(7.) Resident, Department of Ophthalmology, K.R. Hospital, Mysore Medical College and Research Institute, Mysore.

(8.) Resident, Department of Ophthalmology, K.R. Hospital, Mysore Medical College and Research Institute, Mysore.

NAME ADDRESS EMAIL ID OF THE CORRESPONDING AUTHOR:

Dr. K. Satish,

Department of Ophthalmology, MMC & RI, K.R. Hospital, Irwin Road, Mysore--570001. Email--drsatishkeshav@gmail.com

Date of Submission: 07/10/2013.

Date of Peer Review: 08/10/2013.

Date of Acceptance: 26/10/2013.

Date of Publishing: 06/11/2013

Table 7: Complication rates in the two groups

Complications         GROUP A   GROUP B

Granuloma formation      2         2
Recurrence               3         3

Table-8: Reported recurrence rates following
conjunctivo-limbal auto grafting in pterygium surgery

Author           Year   Number    AvG Follow-up    Recurrence
                        of eyes      (Months)       Rate (%)

Kenyon (19)      1985     57            24            5.3
Koch (34)        1992     22           8.7             9
Guler (35)       1994     31            10            13.3
Shimazaki (36)   1996     27           10.9           7.4
Rao (37)         1998     53           18.9           3.8
Pulte (38)       1998     70            45            2.9
Mutlu (39)       1999     41            16            14.6
Our study        2012     100           6              6

FIG 1: Gender distribution

Male     8%
Female   32%

Note: Table made from pie chart.

FIG 2: Type of pterygium

Grade II   69%
Grade I    31%

Note: Table made from pie chart.
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Title Annotation:ORIGINAL ARTICLE
Author:Satish, K.; Prakash, D.N.; Tanwar, Meghana; Gopal, Madhumita; Patil, Savita; Acharya, Ambika A.; Kul
Publication:Journal of Evolution of Medical and Dental Sciences
Article Type:Clinical report
Date:Nov 11, 2013
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