Surgical outcome of eyelid retraction correction using novel spacer filamentous knitted polyester fabric in thyroid eye disease

Abstract

Purpose:

To assess use of the novel spacer filamentous knitted polyester fabric (FKPF) in lid retraction correction in thyroid eye disease (TED) as an effective surgical method to preserve eyelid function and cosmesis.

Methods:

A prospective, non-comparative interventional study of surgical outcomes in 30 patients with TED cases over a period of 3 years. The upper and lower eyelid retraction was corrected surgically with FKPF material. All intervention performed in the inactive phase of Rundle’s curve plotting. LPS was partially recessed and resected from the central part of the tarsal plate to implant the FKPF material. Pre- and post-operative evaluation parameters were marginal reflex distance-1 (MRD-1), MRD-2, upper and lower scleral show, palpebral fissure height (PFH), and LPS action. All the patients were post-operatively followed up on the 1^st week, 3 months, 6 months, and 1 year.

Results:

Pre-operative measurements to post-operative results revealed: MRD-1 was reduced from 9.73 ± 0.71 mm to 3.85 ± 0.51 mm; scleral show of upper lid reduced from 3.70 ± 0.71 mm to no scleral show; MRD-2 was reduced from 6.40 ± 1.18 mm to 5.38 ± 0.41 mm; scleral show of lower lid improved from 1.93 ± 0.36 mm to no scleral show. PFH was reduced from 16.07 ± 1.42 mm to 9.23 ± 0.73 mm. LPS action was pre-operatively 19.08 ± 1.20 mm to 14.40 ± 0.73 mm post-operatively.

Conclusion:

FKPF is an inert, readily available, cost-effective material that shows promise in lid retraction correction. In our study, all lid retractions were repaired with no post-operative complications and met the functional and cosmetic purposes of the intervention. All patients reported high satisfaction with the outcome of the procedure. Due to its availability and non-reactive nature, FKPF offers a potential alternative to underserved areas to increase accessibility.

The orbit is the second most targeted organ in thyroid eye disease (TED).[1] Although the etiology of this complex disease remains unclear, it is known that it is a chronic autoimmune inflammatory disorder. Thyroid profile test of patients with Thyroid associated ophthalmopathy (TAO) shows hyperthyroidism in 77% cases, hypothyroidism in 3% cases, and euthyroidism in 20% cases.[2,3,4,5] TAO has a prolonged quiescent phase, which is preceded by an active inflammatory phase. This active phase usually undergoes remission after 18 months.[6,7] Serious complications like compressive optic neuropathy and exposure keratopathy are likely to arise during this phase. Lid retraction is the most common finding in TAO. In the early phase of the disease, lid retraction may arise secondary to a sympathomimetic overactivity, while in the later stages, it may be associated with fibrosis of the lid retractors. Two other significant eyelid features of TAO are upper lid lag in down gaze and lagophthalmos. This may impair vision due to exposure keratopathy and the psychosocial implications may constrain the quality of life.[8,9]

Treatment of upper lid retraction includes graded Müller’s and levator aponeurosis weakening, and the criterion for a successful correction is enclosing of 1–2 mm of the superior cornea. Lower lid lengthening is indicated in lower lid retraction and inferior scleral show. Recession of only lower lid retractors is not sufficient to correct more than 1 mm of lid retraction and hence an interposition graft or spacer is needed for a notable lower lid retraction.[9,10,11]

In our study, we are primarily concerned with the use of filamentous knitted polyester fabric (FKPF) to correct the amount of upper lid retraction after central disinsertion and partial resection of the levator muscle. It creates a semilunar space that is filled with novel spacer material. In lower lid retraction, the inferior retractor is detached from the tarsal plate and retracted distally to create a semilunar space where FKPF is placed as spacer material.[12,13,14,15]

Aims

We aim to evaluate the functional and cosmetic outcomes of upper and lower eyelid retraction corrected by using FKPF as a novel spacer material and to assess the safety, efficacy, and durability of the FKPF.

Methods

This is a prospective, non-comparative, interventional study conducted over 3 years in 30 different patients. Institutional Ethical Committee Clearance with Ref no. MC/KOL/IEC/NON-SPON/1921/05/2023 dated 19/05/2023 was obtained, and informed written consent was taken from each participant in accordance with the Declaration of Helsinki prior to intervention. The study included euthyroid patients with clinical activity scoring (CTS) system 0/7 and in the inactive phase of Rundle’s curve plotting, TED having upper lid minimum 3 mm and lower lid retraction with a minimum of 2 mm scleral show, limited proptosis ≤22 mm or less, and retraction due to any cause. The study excluded patients with a deranged thyroid profile, active disease, huge proptosis >23 mm, significant squint and restriction of ocular movement, exposure keratitis, thyroid malignancy, systemic skin disorders like Stevens-Johnson syndrome, widespread psoriasis, toxic epidermal necrolysis, local infection of the eyelid, trauma, burn, or chemical injuries involving the lids. Evaluation parameters were pre- and post-operative comparison of patients’ photographs, LPS action, corneal status, marginal reflex distance (MRD-1 and MRD-2), palpebral fissure height (PFH), symmetry of both eyes with eyelid crease height, eyelid closure, and patient satisfaction.

The shape of the FKPF is semilunar. The proximal tarsal border is straight, and the distal border, where LPS is intercepted, is curved. The horizontal length is 26-30 mm, which is kept fixed for the upper lid. The central width of the spacer is determined by the following formula. The central width of the spacer = A + X + 5, where A is the constant factor of 3, which is fixed for every case, and X is the amount of upper lid scleral show in the greatest dimension, varying from case to case. We are inducing moderate ptosis measuring 5 mm from the surgical limbus (2 mm of surgical limbus covered by upper lid + 3 mm drop of upper lid for moderate ptosis). The dimension of the spacer for the lower lid, horizontal length is 17–20 mm, and central width is 6–7 mm, which is fixed in all cases. The shape of the lower lid spacer is semilunar, with the tarsal or proximal end straight, and the distal end toward the inferior retractor site is curved.

Surgical procedure

All the surgical procedures were performed under a frontal block and local infiltration at the incision site for the upper lid. Local infiltration of an esthetic agent is given along the whole length of the lower lid by conjunctival or skin approach. Under the microscope, LPS and Müller’s muscle are disinserted from the central part of the tarsal plate meticulously, ensuring not to injure the conjunctiva. The central part of the LPS muscle was resected approximately 15–17 mm. Then, the lateral and medial parts of the LPS resection are approximately 9-11 mm, respectively. A protective eye shield is mandatory to protect the cornea in each case. A semilunar gap is created between the tarsal border and the redundant part of LPS, keeping the conjunctiva intact for implantation of FKPF spacer material and inducing moderate ptosis [Fig. 1].

Figure 1.

Schematic diagram of upper and lower lid retraction showing MRD-1, MRD-2, and scleral show. MRD-1 = marginal reflex distance-1, MRD-2 = marginal reflex distance-2

The upper lid lifting is only by the lateral and medial horns of LPS, which are kept intact. In the sitting posture, peroperative examination is done in primary gaze, where the upper eyelid height and contour are observed to confirm induction of moderate ptosis. Careful partial resection of the lateral and medial horns is performed to adjust the contour of the eyelid in primary gaze. According to published literature, the lateral horn is very strong in TED patients. Special care is to be taken during partial resection of the lateral horn. Adequate resection of the lateral horn is ensured by allowing the patient to sit in a primary gaze to check the lid contour, particularly on the lateral side, repeatedly. Thus, lateral flare is well controlled. A semilunar gap is created between superior border of the tarsal plate and the distally retracted, redundant part of LPS, where FKPF is implanted to prevent reattachment of LPS to the tarsal plate. The novel FKPF spacer material is fixed with the superior border of the tarsal plate with continuous interlocking 7-0 polypropylene suture. Even the distal part of the spacer material is also fixed with the redundant part of LPS by an interlocking suture. Eventually, the redundant LPS muscle spontaneously attaches to the overlying orbicularis muscle complex. Finally, the skin wound is repaired with an interrupted 5-0 silk suture. In the lower lid through a conjunctival approach, an incision is made to expose the lower border of the tarsal plate. The inferior retractor is exposed, which is detached from the tarsal plate and retracted distally to create a semilunar gap where FKPF is inserted and sutured with the inferior border of the tarsal plate with continuous interlocking 7-0 polypropylene suture. This results in lengthening of the lower lid, thus preventing the reattachment of the inferior retractor. The conjunctival wound is closed with an interrupted 5-0 polyglactin suture. A Frost suture is applied, and it is kept for 4 days to ensure lengthening of the lower lid [Figs. 2 and 3].

Figure 2.

Schematic diagram of the surgical step of implantation of the novel spacer FKPF material between the tarsal plate and the retracted redundant part of LPS, with lateral and medial horns kept intact. FKPF = filamentous knitted polyester fabric

Figure 3.

Surgical steps of eyelid retraction correction with the novel FKPF spacer material – (a) Skin incision given along the marked area. (b) Partial recession and resection of the central part of LPS from the tarsal plate. (c) Preparation of semilunar FKPF spacer. (d) Spacer material is fixed to the tarsal plate with continuous interlocking 7-0 polypropylene suture. (e) Conjunctival incision for approaching the lower tarsal plate. (f) Fixation of FKPF spacer to the lower border of tarsal plate using interrupted Polyglactin suture. (g) Upper lid skin closure after achieving moderate ptosis. (h) Frost suture applied and kept for 4 days for lower lid lengthening. (i) Multiple holes created in FKPF spacer material preparation for increased vascularity of the skin for better healing. FKPF = filamentous knitted polyester fabric

Analysis of data

The collected data were analyzed following the standard statistical protocol. Data were entered in an MS Excel Sheet and analyzed by SPSS v26 PC version. Quantitative data will be expressed in mean + SD or median + interquartile range. Qualitative data will be expressed in proportions and percentages. Associations will be calculated using the Chi-square test or Fisher’s exact test. ‘P’ value < 0.05 will be considered statistically significant.

Results and Observation

In this study, the age of the patients ranged from 30 to 65 years. The mean age with standard deviation of the patients was 43.7 ± 9.94 years. The males were (14) 46.66%, the females were (16) 53.33%, and the M: F ratio was 7:8. In all, the patient socioeconomic status is low to middle as they attended a free government hospital. Six patients (20%) in the male population had a smoking history. All the patients were from different districts of West Bengal state, India. Here, 30 patients were operated, where upper and lower lid retraction were corrected by novel spacer FKPF material. Pre-op mean MRD-1 value was 9.73 ± 0.71 mm to post-op 3.85 ± 0.51 mm, which is statistically significant (P < 0.0001, t = 36.49). Pre-op mean sclera show of upper lid was 3.70 ± 0.71 mm, to post-op nil (no scleral show), it is statistically significant (P < 0.0001, t = 28.38). Pre-op mean MRD-2 value was 6.40 ± 1.18 mm, to post-op 5.38 ± 0.41 mm, found to be statistically significant (P < 0.0001, t = 4.17). Pre-op mean scleral show of the lower lid was 2.21 ± 0.21 mm, to post-op it, the value was nil; it is statistically significant (P < 0.0001%). Pre-op mean PFH value was 16.07 ± 1.42 mm, to post-op 9.23 ± 0.73 mm, and is statistically significant (P < 0.0001, t = 54.91) [Figs. 4 and 5]. Pre-op mean LPS action was 19.08 ± 1.20 mm to post-op 14.40 ± 0.73 mm, which is statistically significant (P < 0.0001, t = 19.47). Proptosis measured in the Hertel Ex ophthalmometer is 19.70 ± 2.13 mm [Table 1]. Symmetry of both eyelid creases is maintained. The lid height difference is 0.5 mm, which is cosmetically accepted. Patients were followed up after 1 week, 1 month, 3 months, 6 months, and 1 year to evaluate MRD-1, MRD-2, PFH, and LPS action, and also to look at corneal status for erosion and exposure, any acute signs of infection and material extrusion, wound status, and granuloma formation [Table 2]. All the patients in the 2-month follow-up period had no complications. From the third month onward, some patients had complications. Wound gaping in 7 (23%) patients with mild exposure of the spacer. Wound infection with discharge in 3 (10%) patients, which is well controlled by systemic antibiotics. A total of 2 (6%) patients had granuloma formation. A total of 4 (13%) patients had partial 2–3 mm extrusion of the distal end of FKPF spacer material in the upper lid, which was trimmed and re-sutured, but all the lid contour and height were well maintained throughout the follow-up period. No such total extrusion of the spacer was reported for any case. None of the patients had a corneal problem, e.g., erosion, keratitis. All the patients were followed up for 1 year without any loss to follow-up.

Figure 4.

Pre- and post-operative image of the patient showing marked improvement of eyelid retraction correction after 3-month early post-op days with visible suture marking

Figure 5.

Pre- and post-operative image of the patient showing marked improvement of eyelid retraction correction after 4 months of early post-op days with visible suture marking

Table 1.

Shows pre-operative MRD-1, upper scleral show, MRD-2, lower scleral show and palpebral fissure height and LPS action values

Sex		Eye		Lid operated		MRD-1 (in mm)		Upper Scleral Show		Proptosis in mm		MRD-2 (in mm)		Lower Scleral Show		PFH (in mm)		LPS Action
						Pre-op		Pre-op				Pre-op		Pre-op		Pre-op		Pre-op
M		RE		Upper		9		3		18		5.5		0		14.5		19
M		LE		Upper+Lower		8.5		2.5		17		7		2.5		15.5		20
F		LE		Upper		9		3		18		5		0		14		18.5
F		LE		Upper+Lower		9.5		3.5		18		7.5		2		17		20.5
F		LE		Upper+Lower		10		4		19		7.5		2		17.5		20.5
M		LE		Upper+Lower		10		4		19		7		2		17		19.5
F		LE		Upper+Lower		8.5		2.5		17		7.5		2		16		18
M		LE		Upper+Lower		10.5		4.5		19		8		2.5		18.5		20
F		RE		Upper		9		3		17		5		0		14		17
M		LE		Upper		9.5		3.5		18		5.5		0		15		19
M		LE		Upper		10		4		18		6		0		16		20
F		RE		Upper+Lower		10.5		4.5		20		8		2.5		18.5		21
F		RE		Upper		9.5		3.5		18		5		0		14.5		19
F		RE		Upper+Lower		9		3		19		7.5		2		16.5		20
F		RE		Upper		8.5		2.5		18		5		0		13.5		16.5
M		RE		Upper+Lower		11		5		24		7		2.5		18		19
F		RE		Upper+Lower		10.5		4.5		23		7.5		2		18		19.5
M		LE		Upper+Lower		10		4		22		8		2.5		18		20
M		RE		Upper		10		4		21		5		0		15		18
F		LE		Upper+Lower		9		3		19		7.5		2		16.5		20
M		RE		Upper+Lower		9.5		3.5		18		7.5		2		17		21
F		LE		Upper+Lower		10		4		22		7		2.5		17		20
F		LE		Upper		10.5		4.5		23		5		0		15.5		18.5
F		LE		Upper		10.5		4.5		22		5.5		0		16		19
M		RE		Upper		11		5		24		4.5		0		15.5		18
M		RE		Upper		10		4		22		5		0		15		17
F		LE		Upper		10		4		21		5.5		0		15.5		17.5
M		LE		Upper+Lower		9.5		3.5		19		7.5		2		17		20
M		LE		Upper+Lower		9		3		19		7		2.5		16		18.5
F		LE		Upper		9.5		3.5		19		4.5		0		14		18

F=female, LE=left eye, M=male, MRD-1=marginal reflex distance-1, MRD-2=marginal reflex distance-2, PFH=palpebral fissure height, RE=right eye

Table 2.

Shows post-operative after one year MRD-1, Upper scleral show, MRD-2, Lower scleral show, palpebral fissure height, LPS action values

Sex		Eye		Lid operated		MRD-1 (in mm)		Upper Scleral Show		MRD-2 (in mm)		Lower Scleral Show		PFH (in mm)		LPS Action
						3 month post-op		3 month post-op		3 month post-op		3 month post-op		3 month post-op		3 month post-op
M		RE		Upper		3.5		NIL 0		5.5		0		9		14
M		LE		Upper+Lower		4		NIL 0		5		-0.5		9		15
F		LE		Upper		4		NIL 0		5		0		9		14.5
F		LE		Upper+Lower		3		NIL 0		5.5		0		8.5		14
F		LE		Upper+Lower		3.5		NIL 0		5.5		0		9		14.5
M		LE		Upper+Lower		4		NIL 0		6		0.5		10		15
F		LE		Upper+Lower		4.5		NIL 0		6		0.5		10.5		15
M		LE		Upper+Lower		3		NIL 0		5.5		0		8.5		14.5
F		RE		Upper		3.5		NIL 0		5		0		8.5		14
M		LE		Upper		4		NIL 0		5.5		0		9.5		15
M		LE		Upper		4.5		NIL 0		6		0		10.5		14
F		RE		Upper+Lower		4		NIL 0		5.5		0		9.5		14
F		RE		Upper		4		NIL 0		5		0		9		14
F		RE		Upper+Lower		4.5		NIL 0		6		0.5		10.5		14.5
F		RE		Upper		3.5		NIL 0		5		0		8.5		15
M		RE		Upper+Lower		3.5		NIL 0		5.5		0		9		15
F		RE		Upper+Lower		3		NIL 0		5.5		0		8.5		14
M		LE		Upper+Lower		4		NIL 0		5.5		0		9.5		15.5
M		RE		Upper		4		NIL 0		5		0		9		14
F		LE		Upper+Lower		4.5		NIL 0		6		0.5		10.5		14
M		RE		Upper+Lower		4.5		NIL 0		5.5		0		10		14
F		LE		Upper+Lower		3		NIL 0		5.5		0		8.5		13.5
F		LE		Upper		3		NIL 0		5		0		8		13.5
F		LE		Upper		3.5		NIL 0		5.5		0		9		14
M		RE		Upper		4		NIL 0		4.5		0		8.5		15
M		RE		Upper		4		NIL O		5		0		9		15
F		LE		Upper		4.5		NIL 0		5.5		0		10		15
M		LE		Upper+Lower		4.5		NIL 0		5.5		0		10		14.5
M		LE		Upper+Lower		4		NIL 0		5.5		0		9.5		14
F		LE		Upper		4		NIL 0		4.5		0		8.5		14

F=female, LE=left eye, M=male, MRD-1=marginal reflex distance-1, MRD-2=marginal reflex distance-2, PFH=palpebral fissure height, RE=right eye, LPS: Levator palpabre superioris

Discussion

A spacer is implanted in the semilunar space created after recession and partial resection of retractors, which enables lengthening of the eyelid and maintenance of its desired contour by joining with the tarsal plate and the retractor. The intended skin crease height can be controlled by the spacer material such that the levator muscle attaches to the overlying skin-orbicularis complex at the desired level, creating the new skin crease.

Various spacer materials have been used to correct lid retraction, e.g., autogenous fascia lata, banked sclera, turnover orbital septum, and hard palate mucosa, but with unsatisfactory results. In 1999, Koorneef for the first time did graded full-thickness anterior blepharotomy, but recurrence was the main complication. Elner et al. reported 15 cases with 93% patient satisfaction.[16,17,18,19] Hintschich and Haritoglou, in a case series, reported 95% success rate with full-thickness blepharotomy in TED patients.[20,21] Morists and Sasim performed a modified Harvey’s technique, where satisfaction was 50%, 32% had an acceptable outcome, and 18% had an unacceptable outcome.[7,22] Looi et al. in their study showed graded LPS, and Müller’s muscle recession and resection reported improvement of MRD from 7.3 mm to 4.3 mm after a single procedure with average post-operative asymmetry of 0.2 mm.[23,24]

In our study, we did a skin approach for central detachment and partial recession and resection of LPS and Müller’s muscle with novel spacer FKPF material implantation. In the upper lid, the mean MRD-1 value improved from 9.70 ± 0.71 mm pre-operatively to 3.85 ± 0.51 mm. The success rate is 96.67%. One of the patients with upper lid retraction correction had partial extrusion of FKPF, and despite repeat intervention, which resulted in inadequate correction, the probable cause being the patient was still in the active phase of the disease. It is almost similar to other studies.

Watanabe A et al.,[25] in their study, based on the turnover orbital septal flap for upper lid retraction, reported good control and stability of skin crease position in 83% cases. In their study, 92% cases showed good symmetry of eyelids with a contoured margin.

In our study, there is good stability of skin crease, and in the post-operative period, there is also similarity of the contour of both eyelids within a 1 mm difference. There was no scleral show of both the upper and lower lids. In our study, four (13.3%) cases had partial extrusion of the spacer material, which was trimmed and re-sutured. In spite of partial extrusion, four cases could maintain the intended lid contour, MRD-1, MRD-2, and PFH within normal values at 1-year follow-up [Figs. 6 and 7]. Regarding the extrusion of the spacer, it is not total in nature. It is only a partial extrusion of 1–3 mm at some part of the spacer from the skin wound. It is observed that patients with TED have a tendency for wound gaping because of poor healing capability. Suture removal was done after 2 weeks. Some patients having intolerance or allergy to polyester material may cause partial extrusion and exudation, which is why we prescribed Montelukast and bilastine combination for the first 10 days, and when wound gaping and clear discharge persisted at any time again, antiallergic drugs were prescribed for another 7 days. Another probable cause for partial extrusion after a 3-month post-operative period, when the patient is allowed to do normal activity, is due to constant blinking, resulting in movement of the spacer material. Here, the tarsal border of the spacer is fixed with 7-0 Prolene suture, but the distal part is free. The central LPS is giving a continuous forward thrust to expel the spacer material, ultimately after 3 months, causing a partial extrusion from the skin wound. Now, we modify the technique for the fixation of the spacer. The distal part of the spacer is fixed with the redundant part of the LPS by continuous interlocking suture with 7-0 Prolene to prevent this complication. Another probable cause of extrusion of the spacer is the creation of an avascular zone at the spacer bed, which reduces the blood supply of the overlying skin, resulting in wound dehiscence. In order to prevent this complication, we create multiple holes in the spacer material to facilitate vascularization between the skin and the posterior lamella. Further study is being conducted using Doppler flowmetry to compare pre- and post-operative vascularity after implantation of spacer material. In this study, two (6%) patients had small granuloma formation; it was managed by hot compression, analgesics, and steroids. In this study, wound gaping in seven (23%) patients with mild exposure of the spacer was quickly managed by skin margin trimming for rawness and re-suturing. The complications observed were reported individually and showed overlap among the patients. Moreover, the complications were transient and easily mitigated by medical or minor surgical interventions, and the resultant long-term outcome was very satisfactory. Only seven (23%) patients showed a complication of wound gaping, three of whom had wound infection with discharge. Among them, two patients had granuloma after systemic antibiotics. The rest of the four patients had only partial extrusion of the implant. Only one patient had an unfavorable outcome in the long term.

Figure 6.

Pre and after 1-year post-operative image of the patient showing marked improvement of eyelid retraction correction with no scar, with satisfactory esthetic outcome

Figure 7.

Pre and after 1-year post-operative image of the patient showing marked improvement of eyelid retraction correction with no scar, with satisfactory esthetic outcome

The use of spacer material like orbital septum to lengthen the levator aponeurosis may not possible in all patients. The orbital septum is a multilayered sheet with variable strength. It is reinforced by ligament below its posterior surface and submuscular fibro adipose tissue in front. It is thicker in young and easy to identify, and thinner in older patient may cause dehiscence.[26]

In our study, FKPF material is 0.6 mm thick, flexible in all directions, inert, non-absorbable, biocompatible; thus, it is compatible in all cases. It is a synthetic material, easily available, with no donor area morbidity. As it is very thin and has negligible weight, the lid thickness is similar to the opposite eye, and lid movement is easier.

Lai et al. suggested that the length of the flap was determined by the formula as 2 × (degree of retraction in mm) +2 mm, a modification from the Piggot et al. In our study, the measurement of the applied spacer material has a defined formula in the upper lid (A + X + 5) mm, where A is a constant factor for FKPF material = 3 mm, X is the amount of scleral show expressed in mm, and the induced moderate ptosis measures 5 mm length from the superior limbus.[27,28,29]

In our study, we did anterior approach to clearly understand the LPS and Müller’s muscle anatomy. Peroperative adjustment of lid height is done for better correction. This novel spacer material causes not only lengthening of the lid, but also prevents reattachment of LPS and the inferior retractor to the tarsal plate. FKPF material is readily available and does not require local tissue harvesting.

Wearne MJ et al. in their study using hard palate mucosal graft as spacer material for lower eyelid retraction surgery noted its effectiveness; however, they pointed out the most important disadvantage of the technique being donor site morbidity and requirement of meticulous surgical dissection and knowledge of the anatomy of the donor site.[30,31,32]

In contrary in our study, as the novel FKPF material is readily available there is no risk of donor site morbidity and related complications. The effectivity of the spacer material is similar to hard plate mucosal graft.

Downes RN et al.[33] conducted a study for eyelid retraction surgery using Mersilene mesh as spacer material. Mersilene mesh is an interlocking polyester material similar to FKPF which shows ingrowth of fibrovascular tissue into the open meshwork. This causes intense tissue reaction resulting in localized eyelid tenderness, prolonged mucoid discharge, and irritation. It has unfavorable long-term stability with chances of surgical site infection and complete extrusion, even though the initial correction is satisfactory. In our study, FKPF material is tissue-friendly, with no post-operative edema, infection, or discharge noted. Only partial extrusion of FKPF material has been reported in four cases. Trimming of exposed spacer material with re-suturing enabled long-term lid height and contour with no recurrence of retraction.

Chau Vo TB et al.[34] used autogenous auricular cartilage for upper lid retraction correction in TED, and the success rate of lid lengthening is 95.65%. The recurrence rate is 4.34%. This procedure is not popularized as it is time-consuming, with donor site morbidity. The nature of cartilage varies for shaping of spacer and complications, e.g., lid thickening, temporal lid retraction, deformed lid contour, superior marginal keratitis, blepharitis, and granulomatous conjunctivitis. In our study material is synthetic and readily available, tissue-friendly. In all the cases, lid eversion was done to observe any visible part of FKPF, but in none of the cases, it is visible. One of the cases had superior limbic kerato-conjunctivitis, but it managed with antibiotic and lubricant drops, but it is transient. The long-term success rate is very high 96% with no other complication mentioned.

Mourits MP et al. used a scleral graft for upper and lower lid lengthening in Graves’ orbitopathy. However, they noted only 50% success rate in a single procedure due to several unfavorable complications, e.g., variable resorption, lid edema, antigenic response, overlying skin changes, cyst formation, preparation and pretreatment of scleral graft, risk of HIV transmission, and corneal irritation.[35,36]

The selection criteria for the spacer are the novel FKPF, which is a synthetic, inert, non-reacting, tissue-friendly material. It is 0.6 mm thick and flexible in all directions. It is a fabric material. Lid thickness, architecture, and contour are well maintained throughout post-op period. TED has upper and lower lid retraction with a minimum of 3 mm scleral show, limited proptosis < 22 mm, and retraction due to any cause. All patients must be euthyroid with CAS scoring system 0/7 and in the inactive phase of Rundle’s curve plotting. It is observed that recession of LPS even in mild cases causes recurrence of retraction after 2–3 months. That is why it is better to reinforce with a spacer material to prevent LPS reattachment to the tarsal plate.

Limitation of the study: Longer time to wait for the inactive phase of the disease in Rundle’s curve plotting. Always disease activity controlled by an Endocrinologist to consult. Careful dissection of LPS under a microscope is mandatory which is time-consuming. The patient needs longer follow-up. Appropriate time to operate on the patient for a satisfactory outcome.

Future plan: early detection of lid retraction, make the patient biochemically euthyroid with good control of thyroid profile by drugs. Lid retraction correction by spacer material and switching the patient to monoclonal antibody for the rest of their life is recommended, to prevent the development of squint and proptosis.

Conclusion

Novel FKPF is an inert, non-reacting tissue-friendly material; hence, there is no chance of graft failure. Thus, tissue acceptance is excellent. None of the cases had total extrusion. As it has 0.6 mm thickness and is flexible in all directions, the fabric material, lid thickness, architecture, and contour are well maintained throughout its life. Thus, FKPF is the ideal spacer material for future generation upper and lower lid retraction correction in TED.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.