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   Table of Contents      
ORIGINAL ARTICLE
Year : 2006  |  Volume : 54  |  Issue : 2  |  Page : 89-94

Asian experience with the Pintucci keratoprosthesis


Maskati Eye Clinic, Mumbai, India

Correspondence Address:
Quresh B Maskati
Harishankar Bldg. 1st Floor Near Saifee Hospital, 23. M. Karve Marg. Opp. Charni Road. Stn. (E) Mumbai - 400 004
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0301-4738.25828

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  Abstract 

Purpose: To report the outcome of a retrospective study of the Pintucci Biointegrable Keratoprosthesis (PBIKP) in Asian eyes.
Materials and Methods: This was a retrospective analysis of 31 eyes of 31 consecutive patients, who underwent surgery with implantation of the PBIKP. The age ranged from 7 years to 65 years, with a mean age of 34 years. The indications for the PBIKP were chemical burns (11 cases); highly vascularized failed grafts (11 cases); severe dry eyes with total vascularized cornea (6 cases); miscellaneous (3 cases). Twenty eight bilaterally blind Asian patients, with vision not exceeding hand motion close to face in the better eye, underwent the classical two-stage procedure to implant the PBIKP. In another three patients, the PBIKP was implanted as a one-stage procedure. All 31 eyes were unsuitable for keratoplasty or had repeated failed keratoplasties.
All patients were followed up for periods ranging from 6 months to 7 years, with a mean of 3.2 years.
Results: No eye had infection or retro prosthetic membrane, which were common complications in other Keratoprostheses designs. Twenty-four of 31 eyes improved to greater than finger counting at 1.5 metres, enabling the patients to function independently. Four of 31 eyes (13%) improved to 20/200 or better. Twelve of 31 eyes had significant complications. However only a few were vision- threatening.
Conclusion
: With careful patient selection, the PBIKP could prove to be a useful modality of treatment for bilaterally corneally blind Asian patients, whose vision cannot be improved with conventional medical or surgical treatments.

Keywords: Pintucci, biointegrable, keratoprosthesis, asian eyes


How to cite this article:
Maskati QB, Maskati B T. Asian experience with the Pintucci keratoprosthesis. Indian J Ophthalmol 2006;54:89-94

How to cite this URL:
Maskati QB, Maskati B T. Asian experience with the Pintucci keratoprosthesis. Indian J Ophthalmol [serial online] 2006 [cited 2020 Jun 3];54:89-94. Available from: http://www.ijo.in/text.asp?2006/54/2/89/25828



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Improvements in eye banking, tissue preservation techniques and corneal grafting surgery, have increased the number of successful corneal transplants being done worldwide. However, not all cases are suitable for keratoplasty. Those with severe stem cell deficiency, severe dry eyes, badly deformed eyelids or highly disfigured anterior segments, are unsuitable candidates for corneal transplants. Sometimes, even suitable candidates for corneal transplants end up with repeated failed grafts due to various reasons.[1] These corneas get highly vascularized, rendering the chances of success of future grafts very poor. Stem cell and amniotic membrane transplants have managed to salvage some of the eyes previously considered unmanageable and render the eyes fit for keratoplasty or even restored corneal clarity without the need for a corneal graft.[2] These procedures too have their limitations. They need some degree of tear production for success. At the 5th international Keratoprosthesis (KPRO) and international ocular surface society meeting held at Ft. Lauderdale in May 2001, it was agreed that eyes with profound corneal blindness, coupled with insufficient tear production, are not suitable candidates for any other procedures, except KPRO.[3] KPRO with rigid optics certainly can be considered to restore vision in such patients.

We have come a long way since the first artificial corneal implant in a human eye by Nussbaum, 150 years ago. Till 1997, only a total of 3000 cases had been reported worldwide. A wide variety of materials were used earlier, including metals, ceramics, glass, plastics and biological tissue, for the anchoring skirts or plates or haptic. For the optic, however, only medical grade Polymethylmethacrylate (PMMA) has been used since the last 50 years.[4] The three most commonly reported KPROs in the world today, are the Dohlman collar button type,[4] the Osteo-Odonto KPRO (OOKP) by Strampelli,[5] Falcinelli in Italy and Liu in UK[6] and the Pintucci biointegrable KPRO (PBIKP) by Pintucci in Italy.[7],[8] The latter two rely on the concept of bio-integration for success.To the best of our knowledge (Medline search), there has been no published report on use of the PBIKP in Asian eyes. We evaluated the PBIKP in a clinic based practice in the Indian context to determine the safety, efficacy and success rate of the PBIKP in Asian eyes.


  Materials and Methods Top


A retrospective analysis of thirty-one eyes of thirty-one consecutive patients who underwent PBIKP surgery for various indications [Table - 1] during the period between 1997 to 2004, was carried out. A single surgeon (QBM) did all surgeries, after obtaining informed consent. Twenty-eight surgeries were done as classical two-stage procedures,[7] with the second stage being done at least two months after the first surgery. Three surgeries were done as a single stage procedure. Follow up ranged from six months to seven years, with a mean of 3.2 years.

All eyes were tested for visual acuity, including ability to perceive the direction from which the torchlight was being shone. Schiotz tonometry when possible or digital tonometry when there were ankyloblephara, which precluded placement of the Schiotz tonometer, was relied on to rule out pre-existing glaucoma. B scan was done in all cases to rule out retinal pathology and to look for optic nerve head cupping. Slit-lamp biomicroscopy, whenever possible, was carried out to note the degree of dryness and the extent of vascularization of the cornea. Schirmer's test without instillation of anesthetic drops, was done in all cases. Severely dry eyes (less than 2 mm wetting in five minutes), eyes with considerable anterior segment disorganization, including symblephara and eyes with incomplete vascularization of the cornea, were selected for the two-stage procedure.

The following inclusion criteria were considered:

1. Best corrected visual acuity, not exceeding hand movement close to face in the better eye.

2. Accurate perception of light in all quadrants in the eye to be operated.

3. B-scan showing attached retina and an axial length not less than 18mm.

4. No history or evidence of long standing glaucoma. (evaluated by Schiotz or digital tonometry and optic nerve head cupping on ultrasound).

5. An interval of at least 6 months after any previous surgery in the same eye. In cases of trauma, an interval of at least 6 months after the trauma.

The surgical technique was the same as reported by Pintucci, for the two-stage technique.[7],[8],[9]

Stage 1: The lower lip was everted, held in a special clamp and a large free graft was harvested from the mucosal side. Gauze soaked in hydrogen peroxide was used to seal bleeders on the raw donor surface and a tincture benzoin dressing was applied on the bare area. No sutures were taken. This graft contained mucosa, as well as sub-mucosal connective tissue. The graft was then placed on a flat surface and visible fibres of the orbicularis oris muscle were trimmed off. The eye was opened, symblephara were released and a speculum inserted. The corneal epithelium and any conjunctival overgrowth on to the cornea were scraped off. A three hundred and sixty degrees peridectomy was done. A single half corneal depth 10/0 nylon stitch was taken in the centre of the cornea, to serve as a marker in the second stage. The buccal mucosal free graft with epithelial surface facing anterior, was placed over the cornea and sutured with interrupted 7/0 vicryl sutures to the surrounding conjunctiva. Some anchoring sutures were taken to the recti muscles as well.

The PBIKP was removed from its sterile packaging, washed with saline and placed under the orbicularis oculus muscle, after making a linear incision through skin and orbicularis below the lower lid. This PBIKP was then left in place for a minimum period of 2 months.

Stage 2: At least two months later, the PBIKP was removed after making an incision similar to the earlier one, under the lower lid. The PMMA cylinder was cleaned of all connective tissue and the Dacron mesh (now fully covered with connective tissue and blood vessels on both surfaces and around the edge), was inspected. The dacron mesh that was soft and pliable at insertion was now fairly firm, but still allowed easy passage of vicryl sutures. The PBIKP was cleaned on a wooden block, so that the PMMA cylinder was devoid of any connective tissue elements. The eyelids were then opened, a speculum inserted and the buccal mucosal flap was reflected back to be hinged in the upper temporal quadrant. Using the central corneal suture as a centration point, a 3.5 mm trephine was used to make a partial thickness circular groove in the cornea. Three radial partial thickness cuts were made on the cornea at the 12, 4 and 8 o'clock positions, extending from the circular groove to 1mm within the limbus. The central 3.5 mm button was then excised, as done in penetrating keratoplasty, with a full thickness knife entry, followed by excision with corneal extension scissors. The three radial cuts were now made full thickness with corneal scissors. The iris was held with strong-toothed forceps, after reflecting the 3 corneal flaps. Multiple cuts were made from the pupil to the iris root and the iris was removed segment by segment. The crystalline lens if present, was extracted intra-capsularly with cryoprobe. If there was an intraocular lens in place, it was removed. Open sky central vitrectomy was done with a vitrector.

The 3 corneal radial incisions were sutured with 8/0 vicryl. The PBIKP was then inserted through the central 3.5 mm corneal opening. The posterior end of the PMMA cylinder projected into the vitreous cavity. The vascularized, colonised, bio-integrated dacron mesh could now sit on top of the patient's cornea. This mesh was sutured to the cornea with 7/0 vicryl sutures. The buccal mucosal flap, which had been reflected earlier, was now brought back and sutured to its original position, after carefully noting the position of the projecting anterior end of the PMMA cylinder. The same trephine was used to carefully trephine the central 3.5 mm of the buccal mucosa. This allowed the PMMA cylinder to project approximately 1.0 mm anterior to the buccal mucosa. The eye was then patched for 48 hours.

In three patients with 360 degrees vascularized opaque grafts and normal tear production, the two stages were combined into a single procedure. In these cases, the PBIKP was directly placed from its sterile packing into the eye, without being placed for two months in the lower lid. The rest of the procedure, including harvesting buccal mucosal tissue from the lower lip, remained the same.

Routine, post-operative care included oral Ciplox tablet. (500 mg 'Cipla Laboratories, Mumbai') thrice daily for five days; Combiflam tablet (Aventis Pharmaceuticals-Ibuprofen 400 mg + Paracetamol 375 mg), twice daily for five days and Betnesol 0.5 mg tablet (Glaxo Laboratories, Mumbai), twice daily for five days. All patients were given a liquid diet through a drinking straw for the first three days, followed by a soft, bland diet for another four days. The raw surface on the lower lip healed in a week to ten days, in all cases.

On removal of the eye patch, the patients were instructed to put antibiotic drops (Oflox Eye Drops, Cipla laboratories), four times a day for one month with reduction of one drop per day every month and then to continue once a day for rest of the life. Prednisolone acetate eye drops, (Allergan India P Ltd.) were started thrice a day for one month and reduced to twice daily in the next month before being discontinued. All patients were advised to continue using their own lubricating drops as frequently as necessary. Patients were told to clean their PMMA cylinders using cotton buds moistened with the same lubricating drops daily, to prevent discharge accumulating on them causing reduction in vision. Corrected visual acuity was recorded at every visit. The optic disc was photographed for evidence of increase in cupping and the fundus was examined at every visit. Digital tonometry was done by asking the patient to turn his/her gaze as inferiorly as possible. By this technique, the sclera was felt through the lid and not the PBIKP, which would give a false impression of very high intra-ocular pressure (IOP) in every case. B scan ultrasonography was done annually. Patients were asked about their ability to function independently, in terms of activities of daily living, at each post-operative visit.


  Results Top


A summary of the results segregated indication-wise, is given in [Table - 2]. None of the patients who completed 3 years follow-up, showed any decrease of best-corrected visual acuity thereafter, till their respective follow-up periods. None suffered any new or additional major complication after three years.

Several of the patients had more than one complication [Table - 3], which were tackled appropriately. For example, two eyes had choroidal detachments due to massive choroidal effusion, which were successfully tapped. The two retinal detachments were operated in conjunction with a retinal surgeon, using a binocular indirect operating microscope system, with a 3-port vitrectomy, with the use of intra-ocular per fluorocarbons with fluid-gas exchange in one case and silicon oil injection in another. Both retinal detachments settled anatomically, though one of the 2 subsequently developed optic atrophy (the patient with the silicon oil injection). The buccal mucosal graft infection was salvaged by intense topical and systemic antibiotic treatment (Oflox Eye Drops and Ciplox Tablets) in one case, while the other case had complete sloughing off of the graft, with exposure of the dacron mesh haptic. Attempted coverage of the defect with amniotic membrane was a failure. Fresh buccal mucosa was harvested after an adequate period of oral antiseptic gargles (AMPM Mouthwash, Elder Pharmaceuticals - Triclosan 0.03%) and placed successfully over the dacron mesh and sutured in place. IOP was virtually impossible to measure accurately, in cases of PBIKP. Progression of glaucoma was assumed from digital tonometry, serial optic disc photography and ultrasound measurement of disc cupping. One of the 3 patients with glaucoma lost vision due to glaucomatous optic atrophy.

In two patients, both in the early part of the series, the buccal mucosa taken was too thick. After the second stage surgery, the PMMA cylinder was flush with the buccal mucosal opening, instead of jutting forward by a millimetre or so. Within 4 months, the buccal mucosa had grown over the PMMA cylinder, reducing the vision from 20/200 in both cases to perception of light. The patient was then treated with surgical excision of the overgrowth, with restoration of vision. The process had to be repeated after 3 months, when re-growth of the mucosa occurred in both cases. In the first case, an attempt was made to cauterize the edges of the buccal mucosa with a heat cautery, to prevent overgrowth. Improper application of the heat cautery resulted in burning off the haptic-optic junction, causing "dropped optic" in the vitreous cavity. The dropped optic was still in the vitreous cavity, 3 years later, with the vision maintained at 20/200 (a new PBIKP was implanted; the buccal mucosa was thinned and re-sutured) [Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4]. In the second case, the entire buccal mucosal flap was reflected back on a hinge. It was considerably thinned from the inner side and sutured back to its original position. This ensured that the PMMA cylinder projected in front of the buccal mucosa. In this case too, final visual acuity was maintained at 20/200. [Figure - 5] shows inner surface of buccal mucosa and [Figure - 6] shows a case with PBIKP, 4 years postoperatively. [Table - 4] depicts the various types of resurgeries done in this series.

Twenty-four of 31 (77.4%) patients were able to perform basic activities of daily living, such as eating food independently and visiting the toilet unaided.


  Discussion Top


There is as yet, no KPRO available that is perfect or complication free and ensures predictable good visual acuity in all cases. Though the OOKP has been reported to attain a vision of 20/40 or better in a majority of cases,[7] the choice of cases tackled is different from those tackled in this series. Also, the OOKP is technically more demanding, requiring excellent teeth and an additional dental surgeon, thus pushing up the expense (over 13,000 Pounds sterling).[7] The Dohlman KPRO does have unacceptably high incidence of glaucoma, as compared to the PBIKP. Dohlman now does the Ahmed Glaucoma Valve procedure in almost every case, before implanting the KPRO (personal communication). We feel that the low incidence of glaucoma in our series, is due to the fact that we excise the iris by pulling it out, thus causing a partial cyclodialysis, resulting in less than 10% incidence of glaucoma.

The key to success of the PBIKP, is the fact that it is bio-integrated with the patient's own tissue. Blood vessels and connective tissue fill the 0.6 mm thickness dacron mesh completely, sealing its pores. These blood vessels link up with the patient's own blood vessels from his ocular tissue, making the dacron haptic a part of the patient's ocular tissue. This prevents epithelial down growth as ectodermal tissue (epithelium) cannot penetrate through mesodermal tissue (connective tissue filling the dacron mesh).[8],[9],[10] This causes an extremely low rate of retro-prosthetic membrane (nil in our series) and extrusion (nil in our series). This bio-integrated mesh also acts as a barrier against infection (nil endophthalmitis and panophthalmitis in our series).

Dohlman did find better prognosis with keratoprosthesis, in cases of Ocular Pemphigoid, as compared to Stevens Johnson (S-J) syndrome.[11] Our number of Ocular Pemphigoid cases were too small to come to any conclusion. However, both cases of ocular pemphigoid were able to carry out activities of daily living independently. Of the 6 cases of S-J syndrome in our series, 5 had vision of greater than 10/200 (83.3%), while only one (16.7%) developed phthisis.

Various factors influence the outcome of KPRO implantation.[6] An intact posterior segment and retinal function is a necessity for attaining some visual acuity. A good pre-operative work-up to evaluate the posterior segment and retinal function is essential,and a close watch is kept to look for complications in the post-operative period. Keeping the KPRO temporarily buried beneath tissue (conjunctiva or skin), application of collagenase-suppressing medication and reduction of evaporative damage to the wound around the device, are other factors that influence the outcome.[12]

Yaghouti et al[12] studied the outcome of KPRO surgery in relation to the pre-operative diagnosis. Most favourable outcomes seen by them were graft failures in non-cicatricizing conditions, whereas S-J syndrome had the worst outcome. Ocular Pemphigoid and chemical burns had intermediate results. The difference between the groups seemed to correlate with the degree of past pre-operative inflammation. We noted a similar trend in the PBIKP implant as well, as is evident from the results.

Pintucci et al had initially implanted twenty transoral mucous PBIKP with the same technique, in severely vascularized corneas, from 1985 to 1991, with a follow-up ranging from 48 to 85 months.[8] In another study, the same authors noted that the 0.25 mm thick fabric was coated only on the surface by connective tissue; the 0.6 mm and the 1.4 mm thick fabrics were perfectly three dimensionally colonized, but that the 1.4 mm thick dacron mesh showed a substantial loss of pliability. Hence the 0.6 mm thick dacron fabric haptic was preferred for all subsequent PBIKP implanted over 19 years in 159 eyes with good results, overcoming the apparently insurmountable difficulties represented by mechanical anchorage and bio-integrability of a KPRO.[10]

We used the 0.6 mm thick dacron haptic and our results compare well with those seen by them. Glaucoma was found in the majority (64%) of eyes treated with KPROs by Netland et al ;[6] identified in 20 eyes (36%) before surgery and an additional 15 eyes (28%), after surgery. Of the 36 eyes they treated with glaucoma drainage devices, IOP was controlled in 29 eyes (81%) and 9 eyes (25%) required additional medications. Continued progression of glaucoma occurred in 5 (14%) of 36 eyes with KPROs and glaucoma drainage implants (Four of these eyes had advanced glaucomatous optic nerve damage before surgery). In our patients, we did not have a high incidence of glaucoma pre-operatively, hence we did not do a drainage implant procedure.

Several of the patients in our series required subsequent surgical procedures. Once we had 2 buccal mucosal overgrowths, we realized that the buccal mucosal graft has to be of an optimum thickness and that it should be thinned on table during the second stage if necessary, so that the PMMA optic projects forward by at least a millimetre. Once this precaution was taken, we had no further problem with pre-prosthetic membrane formation, in any of the subsequent cases. We also learned that a PMMA cylinder floating in the vitreous cavity does not appear to cause any complications, such as retinal detachment, presumably because of smooth rounded edges. An exhaustive search (Medline) revealed that this is a unique case, hence, it may be premature to reach the conclusion that dropped PMMA cylinders may be safely left in the vitreous and a second PBIKP implanted, unlike dropped IOLs which require removal. Unlike Pintucci's series in Europe, where there is a higher incidence of ocular and systemic pemphigoid,[9] this formed only a small percentage of our series (6.4%). Severe chemical burns, which have a uniformly poor prognosis worldwide, formed 35% of our caseload. Both Pintucci and Liu have access to different dioptric powers of KPROs with complex formulae available, to calculate the best power to be used in each case. All our cases were implanted with a uniform 55 D PBIKP. No attempt was made to calculate the actual power required in any case.


  Conclusion Top


The PBIKP with a uniform 55D gives reasonably satisfactory results in Asian eyes. Over 77% patients had vision of counting fingers at greater than 1.5 meters, with which they were able to function independently at home in carrying out activities of daily living. If cases are selected well with a good pre-operative work up to evaluate the posterior segment and retinal function and a close watch is kept to look for complications in the post-operative period, the results may be satisfactory. Secondary glaucoma in this patient group does not frequently develop post-operatively. We have come a long way from what was started by Singh et al , [13] but there is need for greater co-operation between those doing KPRO work to amalgamate the good features of the different designs in our search for the perfect KPRO.

 
  References Top

1.
Gloor P. Complicated Penetrating Keratoplasty. In : 'Cornea', Krachmer, Mannis: Holland, Mosby; 1997. p. 1731-811.  Back to cited text no. 1
    
2.
Kenyon KR, Wagoner MD, Shore JW. Ocular Surface Transplantation, In : 'Cornea', Krachmer, Mannis: Holland, Mosby; 1997. p. 1887-901.  Back to cited text no. 2
    
3.
Dohlman CH. Keratoprosthesis, In : 'Cornea', Krachmer, Mannis: Holland, Mosby; 1997. p. 1855-62.  Back to cited text no. 3
    
4.
Cardona H. Keratoprosthesis. Am J Ophthal 1962;54:284.  Back to cited text no. 4
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5.
Strampelli B. Osteo-odonto-Keratoprosthesis. Ann Ottalmol Clin Ocul 1963;89:1029-39.  Back to cited text no. 5
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6.
Liu C. Tighe B. Striving for the perfect KP, editorial. BJO 1998;82:3-4.  Back to cited text no. 6
    
7.
Geerling G, Liu C, Collin J, Dart J. Cost and gains of complex Procedures to rehabilitate end stage Ocular Surface Disease. BJO 2002;86:1220-1.  Back to cited text no. 7
    
8.
Pintucci S, Pintucci F. The Dacron Felt colonisable KP. Refract Corn Surg 1993;9:196-7.  Back to cited text no. 8
    
9.
Pintucci S, Pintucci F, Caiazza S, Cecconi M. The Dacron felt colonisable Keratoprosthesis after 15 years. Eur J Ophthalmol 1996;6:125-30.  Back to cited text no. 9
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10.
Pintucci S, Pintucci F. New Dacron Colonisable KP. BJO 1995;79:825-9.  Back to cited text no. 10
    
11.
Dohlman CH, Terada H. Keratoprosthesis in Pemphigoid and Stevens-Johnson syndrome. Adv Exp Med Biol 1998;438:1021-5.  Back to cited text no. 11
[PUBMED]    
12.
Yaghouti F, Nouri M, Abad JC, Power WJ, Doane MG, Dohlman CH. Keratoprosthesis: Preoperative prognostic categories. Cornea 2001;20:19-23.  Back to cited text no. 12
[PUBMED]  [FULLTEXT]  
13.
Singh D, Bansel DC, Singh A. Keratoprosthesis: A clinical study. Indian J Ophthalmol 1973;21:112-6.  Back to cited text no. 13
[PUBMED]    


    Figures

  [Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4], [Figure - 5], [Figure - 6]
 
 
    Tables

  [Table - 1], [Table - 2], [Table - 3], [Table - 4]


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