FP539 : Mini SLET – A Double Decker on Road to Success for Pterygium Malady

Dr.Shreya Thatte, T04915

Introduction:

Pterygium is a benign, wing-shaped fibrovascular proliferation extending onto the cornea. As of today, there are many approaches to its treatment. The most common  surgical techniques include pterygium excision with conjunctival or conjunctival limbal auto-graft, coverage with amniotic membrane (AM) or the use of adjuncts such as mitomycin C. The main concern of pterygium surgery is recurrence , which is comparable among these techniques with a recurrence rate between 0.003% and 40.9%.^4,5 . Conjunctival-limbal auto-graft offers a low recurrence rate and fewer complications³.However, it cannot be performed in cases where a large defect needs to be covered or in patients where the conjunctiva needs to be preserved for future glaucoma procedure , to avoid conjunctival scarring at the harvesting site. Some advantages of using an AM are inhibition of angiogenesis and the possibility to cover a large area without the need of harvesting healthy conjunctiva.⁶

This innovative technique describes the use of an AM graft to cover the bare sclera area combined

with a minor ipsilateral simple limbal epithelial transplant (mini-SLET) to provide stem cells at the

limbal area.

 Material and method

Pterygium excision with reverse peeling was carried out under sub-conjunctival anaesthesia.

The area of bare sclera was measured with the help of a calliper and an AM graft 1 mm larger than the measurement was placed over the bare sclera. Its edges were tucked under the conjunctival

margins and fixed with fibrin glue . Using a crescent blade, at superior limbus , a shallow cut of

3 mm in length was made on the corneal side of the limbus, followed by two radial cuts from the

corneal to the conjunctival side of the limbus; these cuts were then joint by a 3 mm peritomy. The

crescent blade was then used to create a 2×2 mm strip of limbal tissue by dissecting from the

conjunctival side into the cornea. This limbal tissue  was cut into 8–10 pieces with Vannas

scissors and placed along the conjunctival side of the limbus over the previously fixed AM.

These pieces were glued into place. Finally, a bandage contact lens was left in place. After surgery,

patients were treated with artificial tears, topical moxifloxacin 0.5% drops every 6 h until full

epithelial healing and dexamethasone 0.1% drops every 4 h for one week and followed by  a 1 month taper. Patients werefollowed up  for a minimum of 6 months and observed for epithelial healing , growth of the limbal epithelial cells, anycomplications, recurrences and  cosmetic results . Donor site was examined for healing and stem celldeficiency.

Observations

30 eyes of 29 patients were studied for effect of this technique. The age ranged from 42 to 78 years ,

with male ( 19 ) preponderance (Tables                 1 an 2).

Table 1: Type of pterygium and gender

Type of Pterygium	Male	Female
Nasal Grade 2	4	3
Nasal Grade 3	7	4
Nasal Grade 4	3	3
Temporal Grade 3	3	1
Double	2	0
Total	19	11

Table 1: Type of pterygium and age and gender

Type of Pterygium	40 to 60 years Male                        Female	60 to 80 years Male                     Female
Nasal Grade 2	1                                 2	3                             1
Nasal Grade 3	3                                 2	4                             2
Nasal Grade 4	1                                 1	2                              2
Temporal Grade 3	2                                 1	1                              0
Double	1                                  0	1                              0
Total  30	8                                  6	11                            5

Pterygia were graded according to corneal involvement into fourgrades. They were also divided into nasal , temporal and double pterygium according to site. Nasal pterygium with grade 2 (23.33%), grade3 (36.66%), grade 4(20%), temporal grade3 (13.33%), double

(6.66%) (Table 3)

Table 3: Types of petrygia and number of patients

Type of Pterygium	No. of Pts	Percentage
Nasal Grade 2	7	23.33
Nasal Grade 3	11	36.66
Nasal grade 4	6	20
Temporal Grade 3	4	13.33
Double	2	6.66

Post operatively (Table 4) all the patients acheived good cosmesis. Epithelial healing was noted within 3- 5 days. No recurrences were noted. Only one female patient had persitent inflammation and vascularization.This was following loss of contact lens and displacement of stem cells due to eye rubbing. She was kept on MMC .04% along with fresh stem cells on AM and recovered with a week .

Table 4: Post operative results

Type of Pterygium	Cosmesis At 4 wks	Inflammation	Chemosis	Epi Healing	Recurrence	Donor site
Nasal Grade 2	good	no	no	good	no	Healthy
Nasal Grade 3	good	1	1	good	no	Healthy
Nasal grade 4	good	no	no	good	no	Healthy
Temporal Grade 3	good	no	no	good	no	Healthy
Double	good	no	no	good	no	Healthy

Discussion

Pterygium excision with conjunctival autograft (CAG) is the well accepted technique with lowest recurrence rate and excellent cosmesis¹ Size of conjunctival autograft varies according to size of bare sclera left after pterygium excision. The conjunctival graft should be thin and little larger to fit into bare sclera without any traction². Thick progressive pterygium requires larger size of graft, which affects larger donor area. If graft is taken from the superior quadrant, it may not leave pristine conjunctiva for future surgical procedures (such as a trabeculectomy). Amniotic membrane (AM) reduces inflammation, vascularization, increases epithelization and healing. It also has ability to act as a substrate. These qualities add advantage when used in pterygium surgery. Therefore AM is used in place of conjunctival auto graft, which shows similar effectiveness to cover bare area as with conjunctival autograft, but recurrence was almost double with AM ³.Another concept is of  localised limbal stem cell dysfunction or deficiency at the limbal arearesulting into pterygium⁷. So, when only AM is placed over bare area, it is deficit in local limbal stem cell , therefore showing higher recurrence rate . Hence while using AM requires limbal stem cells to substitute CAG . Sangwan et al described a novel technique ofsimple limbal epithelial transplantation (SLET) for uniocular limbal stem cell deficiency⁸. Erick Hernández-Bogantes in 2015 thought of replacing CAG with AM with minor ipsilateral SLET in cases with primary pterygium Where AM serves as an ideal substrate tosupport the growth of epithelial progenitor cells ⁹with a mini-SLET for pterygium in cases that are not good candidates for a conjunctival autograft¹⁰.  They reported asmall series of 10 patientswith encouraging outcome of the use of AM with mini SLET for pterygium managementIn our hands, this technique showed definite reduction in  recurrence rates as primary objective  and as a secondary benefit, improvement in  the cosmetic outcomes.This technique is espeically of use in cases with requirement of larger donor graft , less availability of conjunctiva due to ocular surface disease or previous multiple surgeries.

Conclusion

This new technique may have some learning curve to harvest limbal epithelial cells , but it is very simple and effective treatment for primary pterygium with minimal or no recurrence with good cosmetic outcome.

References

1. Tan DT, Chee SP, Dear KB, et al. Effect of pterygium morphology on pterygium recurrence in a controlled trial comparing conjunctival autografting with bare sclera excision. Arch Ophthalmol 1997;115:1235–40.
2. Ozer A, Yildirim N, Erol N, et al. Long-term results of bare sclera, limbal-conjunctival autograft and amniotic membrane graft techniques in primary pterygium excisions. Ophthalmologica 2009;223:269–73.
3. Tananuvat N, Martin T. The results of amniotic membrane transplantation for primary pterygium compared with conjunctival autograft. Cornea 2004;23:458–63.
4. Hirst LW. Recurrence and complications after 1,000 surgeries using pterygium extended removal followed by extended conjunctival transplant. Ophthalmology 2012;119:2205–10.
5. Malek I, Zghal I, Chebbi A, et al. [Conjunctival limbal autograft versus simple excision with intra-operative mitomycin C in pterygium surgery: a comparative study]. J Fr Ophtalmol 2013;36:230–5.
6. Kenyon KR. Amniotic membrane: mother’s own remedy for ocular surface disease. Cornea 2005;24:639–42.
7. Cardenas-Cantu E, Zavala J, Valenzuela J, et al. Molecular Basis of Pterygium Development. Semin Ophthalmol 2014:1–17.
8. Sangwan VS, Basu S, MacNeil S, et al. Simple limbal epithelial transplantation (SLET): a novel surgical technique for the treatment of unilateral limbal stem cell deficiency. Br J Ophthalmol 2012;96:931–4.
9. Meller D, Dabul V, Tseng SC. Expansion of conjunctival epithelial progenitor cells on amniotic membrane. Exp Eye Res 2002;74:537–45
10. Hernández-Bogantes E, Amescua G,Navas A, et al. Br JOphthalmol 2015;99:1598–1600.