Preoperative evaluation

Conjunctival laceration

Most conjunctival lacerations do not require repair and can be treated medically with topical antibiotics. Fluorescein staining and visualization with the cobalt blue filter aids to evaluate the extent of the laceration. Careful evaluation is required to exclude underlying scleral damage especially in the presence of subconjunctival hemorrhage and foreign bodies, which may be frequently present.

Large lacerations (>10 mm) may be sutured with 8-0 polyglactin. Care is taken to approximate the lacerated edges in order to avoid suturing Tenon’s or burying folds of conjunctiva. In patients with extensive ocular injury, manipulation of the conjunctiva should be kept to a minimum given that they may require glaucoma filtration procedures in the future.

Iris trauma

Iris damage may manifest as sphincter tears, iridodialysis or iris prolapse through a full-thickness wound. Sphincter tears and iridodialysis do not necessitate surgical repair in the first instance and are usually managed conservatively. If visual rehabilitation is hindered by significant glare or diplopia after the primary repair, a pupilloplasty or iridodialysis repair may be considered as appropriate.

In the case of iris prolapse, every effort should be made to reposit viable iris tissue that is incarcerated in the wound. Necrotic or infected tissue, however, should be excised. In eyes with long-standing iris prolapse, the iris may be covered with epithelium and care must be taken to remove the epithelium prior to repositing the iris back into the eye.

A blunt cannula and small amounts of viscoelastic may aid the repositioning of iris tissue through the wound. A paracentesis, usually 90° away from the site of the wound, is useful in allowing an iris repositor or cyclodialysis spatula to be introduced into the eye to sweep the incarcerated iris.

Corneal laceration

Not all corneal lacerations require surgical intervention. Small self-sealing or minimally leaking corneal lacerations may be treated with topical antibiotics and cycloplegics. A bandage contact lens or glue may be used in cases where a slow wound leak is present.

Large full-thickness lacerations, or those that continue to leak after 1 or 2 days, are best treated by surgical closure. Surgical intervention should also be considered in large, deep or gaping partial-thickness lacerations in order to minimize corneal scarring and irregularity. In severely traumatized corneas where there is loss of tissue, a donor patch graft or penetrating keratoplasty may be indicated.

Viscoelastic may be injected through the wound or via a paracentesis to reform the anterior chamber if required. 10.0 Nylon is preferably used to close the corneal laceration. The placement of the primary suture depends on the configuration of the wound. When linear, it is placed at the center of the wound with subsequent sutures bisecting the remaining portion. If angulated, the primary suture is placed at the apex of the laceration. Stellate ruptures are difficult to repair and may require triangular, ‘X’ or purse-string sutures (Fig. 21.1). Attempts should be made to place sutures outside the visual axis if possible.

Fig. 21.1 (A: i & ii) A stab incision is made at each of the apices of the stellate wound. A 10-0 nylon suture is passed through each of the incisions and the tension adjusted to oppose the wound prior to tying the ends. (B: i–iv) Appearance after wound closure.

Particular care should be taken when placing sutures in bevelled lacerations. The entry and exit points of the sutures should be appropriately placed in order to avoid overriding of the wound edges or dehiscence secondary to ‘cheese-wiring’ of the tissue (Fig. 21.2).

Fig. 21.2 (A) Suture entry and exit sites should be equidistant for perpendicular wounds. (B) In oblique wounds the distance on the ‘lip’ side (y) should be greater than the opposite side (x).

Any viscoelastic in the anterior chamber must be replaced with balanced salt solution in order to avoid extreme intraocular pressure (IOL) spikes and any anterior synechiae lysed with a cyclodialysis spatula. A Seidel test is performed after closure to ensure a watertight closure.

Corneoscleral lacerations

Lacerations that extend beyond the limbus require a limbal conjunctival peritomy such that the full extent of the laceration can be identified and repaired. Viable uveal tissue that may have prolapsed through the wound should be reposited as excision may cause extensive bleeding. A vitrector or ‘sponge and scissors’ technique may be used to clear incarcerated vitreous.

The primary suture is placed at the limbus to aid as an anatomical landmark and the corneal laceration repaired first. The sclera may be sutured with 8-0 or 9-0 nylon or polyglactin sutures. In order to maintain globe integrity, the scleral laceration should be sutured as soon as it is exposed prior to further exploration.

Lacerations that extend underneath the extraocular muscles require careful assessment. The muscle should be retracted using a hook or sling. If this is not feasible or causes undue pressure on the globe, the muscle should be disinserted as per a strabismus procedure prior to repairing the wound.

Hyphema

Most traumatic hyphemas may be treated medically; however, surgical intervention should be considered in cases with prolonged and severely raised IOP, which may lead to optic nerve damage and corneal staining1. The corneal staining may develop rapidly, especially in younger individuals, but can take several months or years to clear.

Surgical evacuation of the blood is indicated in cases where: (i) early corneal staining is noted, especially in the amblyopic age; (ii) the IOP has been over 40 mmHg for 2 days or over 30 mmHg for 7 days; (iii) the patient has sickle cell hemoglobinopathy or trait and raised IOP. Persistent total hyphemas may also be evacuated to prevent peripheral anterior synechiae and chronic intraocular pressure elevation.

Removal of the blood clot may be carried out with a mechanical vitrector or irrigation and aspiration2. Two paracenteses are made and an irrigation cannula or anterior chamber maintainer placed in one and a vitrector in the other. The aspiration and cutting functions of the vitrector are effective in removing the clot whilst minimizing traction on the iris and iridocorneal angle. Irrigation and aspiration may also be used without the cutter; however, the clot may be too thick to be evacuated and may result in unnecessary traction.

Intraoperative bleeding may occur and adequate tamponade should be applied to stop the bleeding. This may be achieved by elevating the intraocular pressure and/or injecting viscoelastic material at the site of bleeding. Injection of an air bubble into the anterior chamber with intraocular pressure elevation may also be effective. Viscoelastic material if used should be carefully removed in order to prevent postoperative intraocular pressure rise.

Lens trauma

Lens injury following anterior segment trauma may be in the form of cataract, luxation, rupture, or extrusion. In the presence of an intact lens capsule, the cataractous or subluxated lens need not be addressed at the time of primary repair. This allows time to evaluate the extent of injury, carry out appropriate biometry, and plan for elective surgery. Capsular rupture, lens induced inflammation, and secondarily elevated IOP generally necessitate lens removal at the time of primary repair.

In cases where the lens requires extraction, opinions vary on the timing of intraocular lens (IOL) implantation. A posterior chamber IOL may be placed at the time of primary repair if the wounds are clean, the posterior capsule intact, and no posterior segment trauma/foreign body is present. In such cases, biometry of the contralateral eye may be used to gauge the required IOL power.

Poor visualization due to the corneal trauma and uncertainty of the capsular and zonular integrity pose a challenge for cataract extraction at the time of primary repair. A separate limbal incision is created following repair of the corneal laceration. The anterior capsular tear may be converted either to a curvilinear capsulorrhexis or to a ‘can-opener’ type of capsulotomy. Gentle hydrodelineation may be carried out and in most cases the lens can be aspirated with minimal phacoemulsification. Care should be taken to avoid undue stress on the zonules and there should be a high index of suspicion for zonular weakness, anterior and posterior capsular tears, and vitreous prolapse.

Vitreous prolapse

Vitreous prolapse into the anterior chamber is a result of zonular weakness and/or posterior capsular rupture and necessitates an anterior vitrectomy, which is most effectively carried out with a mechanical vitrector. A light pipe, air bubble, or intracameral triamcinolone may be used to visualize the prolapsed vitreous although the latter is usually avoided in cases when there is risk of infection.

A small vitreous prolapse through a scleral wound may be managed using a sponge and scissors technique whereby a dry sponge is used to engage the vitreous strands, which are cut flush with the wound surface.

Intraocular foreign body

When the history suggests a possibility of projectile objects, the conjunctiva and cornea must be carefully inspected as mild epithelial staining or corneal edema may indicate a foreign body entry wound. A thorough search must be carried out as multiple foreign bodies are frequently present. Alignment of wounds may assist location of the foreign body and gonioscopy may aid visualization of foreign bodies that have entered the anterior segment and fallen into the angle recess. Iris transillumination and dilated fundal examination should be carried out to exclude intralenticular and posterior segment foreign bodies.

Whilst small and inert foreign bodies may be left in situ and observed periodically, those that cause visual interference, or have toxic or infective potential, should be surgically extracted.

Foreign bodies embedded in the bulbar/subtarsal conjunctiva and cornea may be removed at the slit lamp. Those in the anterior chamber are removed via a limbal incision, which should be large enough to accommodate the foreign body and the instrument used for removal. Viscoelastic material can be used to mobilize the foreign body that may be attached to the posterior corneal surface, iridocorneal angle, or iris. This would also limit movement of the foreign body and prevent further endothelial or lenticular damage. Forceps or an electromagnet may be used to remove the foreign body.

Postoperative care

Post-traumatic septic endophthalmitis carries a poor prognosis and, given the higher risk as well as the fact that it may be difficult to distinguish from the effects of trauma itself (i.e. pain, redness, inflammation, and reduced vision)3, prophylactic antibiotics must be prescribed in all cases.

Subconjunctival antibiotics are administered after surgical repair. Topical and systemic antibiotics are used for 7–10 days and cycloplegics may help prevent posterior synechiae and improve patient comfort. Steroids are contraindicated in injuries with risk of septic endophthalmitis but may be added to control postoperative inflammation when the risk of infection diminishes.

Beta blockers and aqueous suppressants are used to treat raised IOP, e.g. after lens injuries with dispersion of lenticular material (phakolytic glaucoma). Low pressure consequent to minor wound leakage can be managed by pressure patching or a bandage contact lens, whilst closely monitoring the patient.

All patients should be followed up closely with particular attention to signs of infection. Posterior segment examination must be carried out following repair and visual rehabilitation initiated as soon as practical.

Indications

Conjunctival flaps may be utilized in a variety of corneal diseases that are not responsive to medical management, induced ptosis, or tarsorrhaphy. Chronic ocular surface disease and non-healing corneal epithelial defects are excellent candidates for flap surgery5. It has also been used to stabilize the eye in chronic and non-response viral, bacterial, and fungal corneal infections6–8. In the presence of a descemetocele or perforation, a corneal patch must be carried out prior to considering a conjunctival flap.

Along with providing corneal support and fibrovascular tissue to fill epithelial defects, the associated blood supply aids to bring immunoglobulins, anticollagenases, and systemic antibiotics to the lesion9. This advantage is not afforded when applying non-living tissue such as amniotic membrane. Other indications include neurotrophic ulcers, marginal ulcers, exposure keratopathy, and bullous keratopathy with low visual potential.

Surgical technique

Total conjunctival flap

Peribulbar or retrobulbar anesthesia may be administered and an eyelid speculum creating good exposure of the conjunctiva is inserted. The corneal epithelium is removed with a sharp rounded blade or alcohol. Any necrotic stroma tissue is also removed carefully. The debridement is best performed at the beginning of surgery so as not to neglect to perform it after the flap is created. In addition, any bleeding at the limbus will have had time to undergo hemostasis while the flap is being fashioned.

A 6.0 silk or polyglactin 910 traction suture may be placed through the cornea near the limbus to allow downward rotation of the globe during flap dissection. The superior conjunctiva is dissected from the underlying Tenon’s tissue by injecting 1–2 ml of local anesthesia (e.g. 1–2% lidocaine) or balanced salt solution with a 27 gauge needle. Epinephrine in a dilution of 1 : 100 000 may be added to achieve temporary vasoconstriction. The injection site should be situated away from the conjunctiva intended for flap use so as to prevent creating a ‘buttonhole’. A small horizontal incision is made with Wescott scissors at the fornix through conjunctiva, but not into Tenon’s fascia. Then the blunt and sharp dissection is performed with Wescott scissors and non-toothed forceps, separating conjunctiva from Tenon’s, ideally in the plane created by the local anesthesia. Dissecting the conjunctiva with the scissors placed underneath (Fig. 21.3A and B), as opposed to under direct visualization, ensures that the correct plane is maintained and minimizes the risk of buttonhole formation. The dissection is carried out in a meticulous fashion to the limbus and care is taken to avoid buttonholes, although this may be difficult in eyes that have had chronic inflammation, scarring, surgery, or trauma.

Fig. 21.3 (A) The epithelium has been debrided and the superior conjunctiva ballooned with local anesthesia. While the limbal traction suture is used to pull the eye downward, a small conjunctival incision is made 12–14 mm superior to the limbus, and blunt and sharp dissection are used to create a thin flap. (B) Once the dissection has reached the limbus, the superior incision is extended nasally and temporally. (C) After the entire flap is fashioned, a 360° conjunctival peritomy is performed. The flap is brought down over the cornea and sutured to episclera and conjunctiva inferiorly, and episclera superiorly. Care should be taken to avoid buttonholes and excessive traction on the flap.

Once most of the conjunctiva is dissected down to the limbus, the horizontal incision can be extended several millimeters toward the nasal and temporal canthi (Fig. 21.3B). The nasal and temporal portions of the flap then need to be undermined. Once the entire flap has been created, the conjunctival dissection is continued forward until it comes free at the limbus. A 360° conjunctival peritomy is then performed. A small amount of undermining of the inferior limbal conjunctiva often makes the peritomy and subsequent suturing of the conjunctival edge easier. The limbus is then debrided of any remaining epithelium.

The ocular surface is irrigated and the flap carefully slid over the cornea. It is first sutured inferiorly to episclera and the inferior conjunctiva using interrupted 8-0 absorbable sutures (e.g. Vicryl). Once the flap is secured inferiorly, the superior edge is secured to the Tenon’s and episclera without excessive tension. Care is taken to avoid imbedding a fold of conjunctiva. The crescentic area of bare episclera which remains in the area from where the flap was obtained, usually epithelializes within days. An inferior conjunctival flap may be considered to spare the upper quadrants when filtration surgery is likely to be needed in the future.

Buttonholes of the flap are the most common intraoperative complication and can lead to flap retraction. These should be closed with interrupted or purse string sutures and, if located in an area of flap that covers the cornea, the sutures should be anchored to the underlying cornea. Fig. 21.4 illustrates the pre- and postoperative appearance of a total conjunctival flap. Failure to separate Tenon’s fascia from the overlying conjunctiva leads to fibrovascular proliferation and poor transparency (Fig. 21.5).

Fig. 21.4 (A) Chronic non-healing ulcer in a patient with previous penetrating keratoplasty. (B) Appearance following a total conjunctival flap. (C) Six months postoperatively, the eye remains stable and the anterior chamber can be visualized. The patient maintains a visual acuity of 20/200.

Fig. 21.5 A total conjunctival flap with incomplete Tenon’s dissection. The superior portion of the flap where Tenon’s fascia was not dissected is opaque whereas areas of complete Tenon’s dissection appear translucent.

Partial conjunctival flaps

Localized limbal and paralimbal lesions in an otherwise healthy cornea may occasionally be treated with a partial conjunctival flap. The corneal epithelial debridement is carried out in the area expected to be covered by the conjunctival flap and the conjunctiva is ballooned with local anesthesia as described above. The width of the conjunctival flap should be approximately 1.5 times the width of the lesion to be covered in order to allow for proper suture placement and account for late flap retraction. In order to secure the conjunctival edge onto the cornea and prevent dehiscence and retraction, it is important to create a ledge of cornea into which to suture the conjunctiva. A groove is made into healthy cornea at the edge of the intended extension of the flap with a diamond or metal blade and a small triangular strip of cornea is removed to create a ledge (Fig 21.6).

Fig. 21.6 An inferior partial conjunctival flap has been fashioned. The superior aspect of the flap was sutured to a ledge of cornea. A conjunctival relaxing incision was created inferiorly, and the inferior aspect of the flap was sutured to the episclera inferiorly.

The partial flaps may be fashioned in various ways. A simple advancement flap is created much in the same manner as a total flap; however, the amount of conjunctival dissection is smaller and the edge of the flap is sutured on to the cornea with 10-0 nylon sutures. An advancement flap is prone to retraction with time and a relaxing incision through the conjunctiva and Tenon’s tissue, away from the limbus, may reduce the likelihood and allow the bulbar conjunctiva distal to the incision to retract. A pedicle (Fig. 21.7) or bridge flap (Fig. 21.8) may be considered as alternatives. A bridge flap may be created with a narrow band of conjunctiva that runs across the corneal lesion allowing a greater view of the anterior chamber. Edges of the flap overlying the cornea are sutured with 10-0 nylon and those overlying episclera with 8-0 polyglactin 910 (e.g. Vicryl). Non-absorbable suture knots must be buried.

Fig. 21.7 Pedicle flap. An adjacent area of peri-limbal conjunctiva is dissected and rotated to cover the defect.

Fig. 21.8 Bridge flap. A narrow strip of conjunctiva is dissected as per a total conjunctival flap; however, both edges are sutured onto the cornea.

Postoperative care

Postoperative treatment includes topical antibiotic with or without corticosteroids. A therapeutic bandage contact lens may be applied in the initial postoperative period. Non-absorbable sutures may be removed as early as 6–8 weeks postoperatively.

Postoperative complications include retraction of the flap, more common in case of unrecognized buttonholes or inadequate suturing. Fluid accumulation under the flap can occur when a perforation or leaking descemetocele was not detected preoperatively. Epithelial cysts may form if epithelial cells remain and proliferate under the flap. Excessive conjunctival excision from the superior fornix may lead to ptosis although this is rarely significant.

Conjunctival flaps are generally permanent solutions to chronic problems. However, they may be removed once the underlying condition has resolved. The conjunctiva is strongly adherent in areas where the Bowman’s layer has been breached, but it is easily peeled off from the areas with an intact Bowman’s layer. Some corneal scarring generally remains and a penetrating or lamellar keratoplasty may be performed to improve vision.

Indications

Pterygia are generally managed conservatively and any associated irritation and inflammation may be treated medically with ocular lubricants, non-steroidal anti-inflammatories, or a short course of topical steroids. A thorough history and examination must be performed to exclude the presence of pseudopterygium, e.g. corneal adhesion after chemical burns or marginal ulcers.

Surgical intervention is considered if there is: (a) visual impairment by either direct encroachment onto the visual axis or increasing astigmatism, (b) threat of visual impairment by documented growth, (c) inflammation and irritation not controlled medically, (d) restriction of ocular motility, and/or (e) significant cosmetic concern. Occasionally, pterygia may cause contact lens intolerability and the decision to discontinue lens wear should be weighed against surgical intervention. Pterygium surgery should not be taken lightly as significant potential complications exist, not the least of which is recurrence of the pterygium, occasionally worse than the original disease.

Surgical technique

The goals of pterygium surgery are to remove the lesion, restore the conjunctival anatomy, leave the cornea as smooth and clear as possible, and prevent recurrences. Historically there have been, and there continue to be, numerous techniques to manage pterygia. Techniques described include avulsion or excision of pterygia leaving either ‘bare sclera’, closure with conjunctiva (direct, sliding and auto-grafts) or amniotic membrane and use of peripheral lamellar corneal grafts. Various adjuncts (e.g. mitomycin C) have also been used in combination with the different techniques. The lack of consensus on the preferred surgical approach is due to recognition that no single surgical method has proven to be superior. The following will describe one widely used technique of pterygium excision and conjunctival transplant.

Primary pterygium

Peribulbar anesthesia is most commonly used; however, the procedure may also be performed under topical and/or subconjunctival anesthesia. An eyelid speculum providing good exposure is placed and a limbal traction suture (6.0 silk or polyglactin 910 on a spatulated needle) may be placed at the 12 or 6 o’clock position, or both, to allow more extensive globe rotation and aid rectus muscle identification.

The outline of the pterygium is marked with a gentian violet marker, and anesthetic or balanced salt solution is injected subconjunctivally to balloon the pterygium (Fig. 21.10A). This allows easier dissection and protects the underlying rectus muscle from accidental damage.

Fig. 21.10 Surgeon’s view through the operating miscroscope. (A) The outline of the pterygium is marked with a gentian violet marker. (B) A toothed forceps is used to tent the head of the pterygium whilst using a rounded blade to aid dissection. (C) The traction suture is used to pull the eye up and the area of conjunctival graft measured and outlined prior to ballooning with local anesthesia. (D) Multiple sutures are used to secure the conjunctival graft.

The head of the pterygium is lifted with fine toothed forceps and gentle dissection using a rounded sharp blade (e.g. Beaver No. 57) or Tooke’s knife is employed to roll the tissue towards the limbus (Fig. 21.10B). A superficial keratotomy may be made to outline the leading edge prior to the dissection and a superficial plane of dissection is maintained up to the limbus. Attempts must be made to maintain a level and smooth plane of dissection. On reaching the limbus, the bulbar portion (body) of the pterygium is then excised carefully down to the sclera using Wescott scissors. Particular attention should be paid in dissecting and removing all the underlying Tenon’s tissue. To minimize the risk of recurrence, this dissection should lead to complete removal of all the hypertrophic fibrotic tissue underlying the pterygium and must be carried out up to the recti perimysium, into which it usually blends. The gentian violet marks allow visualization of the margins following the subconjunctival injection and avoid inadvertent excision of the plica semilunaris and caruncle. Wet field cautery may be applied sparingly to achieve hemostasis. Remnant tissue at the limbus and sclera is scraped using a rounded blade or large diamond burr.

The rolled edges of the remaining conjunctiva are unraveled with forceps, and the conjunctival defect is then measured with calipers. The globe is rotated upward with the limbal traction suture and the inferior bulbar conjunctiva away from the pterygium excision is exposed. In general, it is advisable to spare the superior conjunctiva, in case filtration surgery is needed later in life. A limbal edge is preferred and a gentian violet marker is used to mark the outline of the remaining three sides of conjunctival graft to be created (Fig. 21.10C). The conjunctiva is dissected from the underlying Tenon’s tissue by injecting 1–2 ml of local anesthesia (e.g. 1%–2% lidocaine) with a 27-gauge needle. The injection site should be situated away from the conjunctival graft intended for use so as to prevent creating a buttonhole. A small incision is made just peripheral to the superior corner of the marked area. Blunt and sharp dissection is performed with Wescott scissors and non-toothed forceps to ensure that the conjunctiva is separated from Tenon’s, ideally in the plane created by the local anesthesia. The dissection is carried out in a meticulous fashion to the limbus and care is taken to avoid buttonholes. Once the conjunctiva is dissected free from the underlying Tenon’s, the edges of the graft are cut slightly larger than the outline marks. This allows for the natural tissue shrinkage and also incorporates the gentian violet marks, which are useful in aiding graft orientation.

Once the graft is totally free, the area to be grafted is re-examined to make sure it is clear of significant clot or active bleeding. The ocular surface is moistened with balanced salt solution and fine non-toothed forceps are used to slide the graft onto the bare area ensuring that the epithelial side remains up and the limbal areas correspond. The risk of tissue rolling, incorrect orientation and excessive manipulation is minimized by sliding the graft and thus lifting it off the eye should be avoided.

Once the edges of the graft are approximated to the edges of the bulbar conjunctiva, absorbable sutures (e.g. polyglactin) are used to secure the graft. The first sutures are positioned through the two limbal corners of the graft, into sclera, and then into conjunctiva to place the limbal edge of the graft on gentle stretch. If the limbal edge is on good stretch, no additional sutures are required. The next two sutures secure the posterior corners of the graft to the bulbar conjunctiva. Additional sutures are placed to close the wound edges and horizontal mattress sutures may be used to anchor the edges to the underlying sclera (Fig. 21.10D). It is important to suture the graft to conjunctival edges, and not just Tenon’s, as these two tissues may appear similar. A wet swab may be used to distinguish between the two, as Tenon’s tends to stick to the swab whereas conjunctival tissue does not. The conjunctival defect in the area from which the graft is harvested may be sutured, but is usually allowed to re-epithelialize spontaneously. Suture knots are not generally buried and any buttonholes are sutured and anchored to the underlying sclera.

Postoperative care

Postoperative care includes topical antibiotics and corticosteroids. Initially, ointments are preferred over drops 4–6 times a day as they tend to be more comfortable. A therapeutic bandage contact lens may also be applied. Once both corneal and conjunctival re-epithelialization is completed, the medication can be changed to corticosteroid drops, which are tapered slowly over several weeks. Non-absorbable sutures, if used, should be removed between 3 and 6 weeks postoperatively.

During the first two postoperative weeks there is often significant edema of the conjunctival graft. Continued frequent use of topical corticosteroids leads to resolution of the edema, which does not affect graft survival as long as the sutures holding the conjunctival transplant do not loosen prematurely. Significant graft swelling can cause dellen formation, which needs to be treated with aggressive lubrication.

Conjunctival or corneal infections may develop after surgery and should be treated with aggressive topical therapy as appropriate following swabs for microbiology cultures.

Large buttonholes, poor wound apposition, and cheesewiring of sutures due to excessive tension on the graft increase the chances of early graft healing problems. Graft dehiscence may also occur due to infection or loose sutures and may require re-suturing or replacement.

Complications which are generally not debilitating or sight threatening include astigmatism, graft retraction, inclusion cysts, suture granulomas, and hematomas.

The most common complication of pterygium surgery is recurrence. Adjunctive therapies may be applied at the time of recurrent pterygium excision. Although beta radiation, thiotepa, daunorubicin, etc. have been used previously, mitomycin-C application remains popular due to evidence of reducing recurrence. However, the lack of consensus on the precise dose and duration of application, together with the potential adverse effects including scleral perforation, limit its use and call for precautions.

Other significant complications include corneal irregularity and scarring, excision-induced limbal stem cell deficiency, restriction of ocular motility, rectus muscle disinsertion, and infection.

Indications and contraindications

Classically the indications for PTK are anterior (i.e. involving the superficial one third) corneal opacities affecting visual function.

The three diagnostic categories better responding to PTK are:

Before considering PTK, a corneal exam not only by slit lamp but also by anterior segment OCT or by Scheimpflug camera is ideal in order to obtain a pachimetry map of the cornea and to quantify the position of the lesions. The residual stromal bed should be at least 300 μm thick at the end of the surgery. Best results are obtained when the pathology involves no more than the anterior one third of the cornea.

As with any corneal surgery, caution should be taken in patients with potential corneal healing abnormalities, such as neurotrophic corneas (e.g. after herpes simplex or herpes zoster keratitis), exposure keratitis, severe keratoconjunctivitis sicca or blepharitis, collagen vascular conditions (e.g. rheumatoid arthritis) and diabetes mellitus. Additionally, patients with herpes simplex keratitis are at risk14–16.

Elevated lesions

Salzman’s nodular degeneration and keratoconus nodules are the main diagnoses.

These lesions often involve the anterior stroma and so, to obtain a smooth surface after the peeling with a blade, PTK is generally performed with the use of a masking agent to achieve the smoothest surface.

Recurrent corneal erosions

Recurrent corneal erosion syndrome with anterior basement membrane dystrophy was treated in the past with simple epithelial debridement, therapeutic contact lenses, or anterior stromal puncture. However long-term data have proved that diamond burr superficial keratectomy at the slit lamp and, above all, PTK have significantly minor recurrences13,17,18.

Stromal lesions

Dystrophies of Bowman’s layer, such as Reis–Bucklers dystrophy, and stromal dystrophies, such as granular or lattice dystrophy, are the main indications.

Best results are obtained when the opacities are in the anterior 20% of the cornea. It is a general opinion that PTK may be tried in all patients with dense superficial opacities before undergoing a more invasive procedure, such as lamellar or penetrating keratoplasty13,19.

Corneal haze after excimer laser corneal surgery

The most important predictive factor in haze formation has been reported to be the depth of ablation that is linked to the attempted dioptric correction. This could be related to surface irregularities that impede normal corneal repair when higher corrections are performed. In theory PTK could be very useful in preventing haze by obtaining a smoother surface after PRK.

PTK can be also used to treat late haze and subepithelial scarring after PRK (Fig. 21.11). In both cases MMC is utilized because predominant effect of MMC in blocking haze formation was at the level of profound inhibition of the replication of keratocytes and myofibroblast progenitor cells in the corneal stroma that occur following the normal keratocyte apoptosis response to epithelial removal during surface ablation.

Fig. 21.11 (A) Cornea OCT (Optovue) of subepithelial scarring 1 year after PRK. (B) One month after large-area PTK with MMC 0.02% for 120 seconds. Corneal OCT (above) showing the disappearance of superficial stromal scarring. The pachimetry map (below) shows a residual stromal bed >300 µm in all quadrants.

Although its utility and efficacy for haze prophylaxis are well documented, the long-term safety profile of MMC use in refractive surgery is not known and it is still used in an off-label fashion.

Technique

The technique varies according to size, shape, density, and numbers of the cornea lesions (Figs 21.12 and 21.13).

Fig. 21.12 (A) This eye has a relatively smooth, diffuse anterior stromal opacity such as lattice or granular dystrophy. (B) A large central transepithelial excimer laser ablation is being performed. (C) After the PTK laser ablation, most of the opacity has been removed and a smooth stromal bed remains.

Fig. 21.13 (A) This eye has a localized elevated lesion, such as a Salzmann’s nodule. (B) A high- magnification view of an anterior stromal lesion. (C) After removal of the epithelium from the surface of the nodule, excimer laser ablation is applied to ‘shave’ down the lesion. (D) After the PTK laser ablation a smooth stromal bed results.

Thus it can be used for:

• Large area photoablation

• Focal ablation

• PTK with masking fluids

• PTK with MMC

• PTK after PRK ± MMC.

Elevated lesions are generally debulked with a blade before PTK.

The epithelium is generally mechanically removed if loose and irregular, while it is left in place before PTK if it is smooth, because may act as an effective masking agent.

Modulating agents such as artificial tears, also called masking fluid, can be very useful in achieving a uniform corneal surface. For this purpose, variable mixtures of hyaluronic acid solutions were proposed.

The treatment is stopped several times to check, also at the slit lamp, the progress of photoablation.

PTK can be also performed topographically guided or ‘customized’13,21.

Intraoperative mitomycin C (MMC) can be used after PTK to try to decrease postoperative haze and recurrence.

Commonly MMC is used at 0.02% (0.2 mg/ml) concentration, on a 6–8 mm circular sponge for 60 seconds; it is then irrigated with 30 ml of saline13,20,22. Other regimens are also suggested.

Postoperative treatment

Pain is the most important issue in the early postoperative period. Immediately after surgery, the eye is treated with either a bandage soft contact lens or a pressure patch. Ice packs are often very effective in treating the pain. Strong anti-pain medications are also widely used. Eyes with BSCLs are treated with topical antibiotic drops. The pressure patch is removed from the other eyes after 1 day and frequent antibiotic ointment is prescribed. Patients are followed every few days and the antibiotics are continued until the epithelial defect heals. There is a higher risk of postoperative problems such as poor healing, infection, and scarring after PTK than after routine keratorefractive surgery, as these corneas are usually not ‘normal’13.

Summary

PTK is a very versatile technique that is quite effective at treating a wide variety of anterior corneal lesions (Figs 21.14 and 21.15) with a low risk rate if performed properly. In particular elevated lesions and opacities in the top 10–20% of the corneal stroma generally do very well. If unsuccessful, an anterior lamellar graft can almost always be performed and thus PTK may be tried before proceeding to a corneal transplant, considering its excellent risk/benefit ratio13.

Fig. 21.14 Band keratopathy pre (A) and post (B) (3 months) large PTK. Note the cornea transparency after 3 months.

Fig. 21.15 Granular dystrophy pre (A) and post (B) (1 year) large PTK. Note the initial recurrence of the pathology.

Introduction

Corneal graft involves the replacement of host corneal tissue with donor corneal tissue or, in specific cases, with synthetic corneas or autologous non-corneal tissue (keratoprosthesis). Depending on the underlying problem the aim of corneal graft may be to achieve one or more of the following effects: (i) optical, (ii) therapeutic, or (iii) tectonic.

Over the past century, full-thickness (penetrating keratoplasty; PK) and partial-thickness (lamellar keratoplasty; LK) keratoplasty had alternating success in establishing themselves as the procedure of choice. Initially, when the role of endothelial function was yet to be understood, results of PK were extremely poor and LK was more popular.

A few decades ago, the discovery of the endothelial metabolic pump, the development of corneal storage, and advances in surgical technique made penetrating keratoplasty the technique performed by the vast majority of surgeons. The change was prompted mainly by the superior visual outcomes obtainable with PK, at a time when visual acuity post-LK was strongly affected by the poor optical quality of the manually dissected interface then obtainable. Recently, with advances in instrumentation and novel techniques of selectively removing and replacing just the layers of diseased tissue, LK has gained an increasing role.

Historical perspective

There is considerable debate regarding who first came forth with the concept of replacing diseased or scarred corneas with living tissue. Guillaume Pellier de Quengsy first suggested replacing the diseased cornea with a thin glass disc (similar to a keratoprosthesis) in 1789, and Erasmus Darwin, grandfather of the famed Charles Darwin, first suggested replacing a scarred cornea with a small piece of living donor corneal tissue. Franz Reisinger published the results of his experiments on corneal transplantation in rabbits and chickens in Germany in 182423–25. S.L. Bigger successfully replaced the scarred cornea of his pet gazelle with a healthy donor cornea from another gazelle in 183724. Richard Kissam, a New York ophthalmologist and general practitioner, was the first to operate on a human using a pig donor cornea; however, the graft became opaque shortly thereafter24. The advent of ether and chloroform inhalation anesthesia, topical cocaine anesthesia, local infiltrative anesthesia, and antiseptic surgery during this early period revolutionized corneal transplantation, as it also did for many other types of surgery.

These important companion discoveries were undoubtedly instrumental in accelerating the progress of corneal transplantation. Considerable amounts of experimental work using living corneal grafts ensued. Von Hippel was the first to improve vision with LK, consisting of a full-thickness rabbit donor cornea placed into a human recipient lamellar bed24. He was also the first to use a circular trephine. In 1906 successful total penetrating corneal graft in a human was reported by Zirm in a laborer with bilateral lye burns to the cornea26. Ironically, alkali burns like this are now known to have one of the worst transplantation prognoses. Anton Elschnig of Prague, with his extensive experimental and clinical work in the 1920s through the 1930s, is credited with refining the crude technique into an elegant, reliable procedure. Filatov, Tudor Thomas, Paton, Franceschetti, Paufique, Sourdille, Castroviejo, Arruga, and the Barraquer brothers, all eminent surgeons, based much of their knowledge and methodologies on the foundation laid by Elschnig24. Ramon Castroviejo, a Spanish ophthalmologist practicing in New York City, initiated detailed grafting methodologies, expounding the use of the square graft (Fig. 21.16), and developing and refining keratoplasty instrumentation. A. Edward Maumenee extensively studied the immunology and physiology of corneal graft rejection. Claes H. Dohlman came to the United States from Sweden and established the first cornea fellowship program in 1961, emphasizing the importance of both clinical and research training. With more recent ophthalmological advances consisting of microscopic surgery, inert sutures, antiviral and antibiotic medications, topical and systemic corticosteroids, tissue-preservation/eyebanking strategies, and progress in immunology, the success of corneal transplantation has grown rapidly over the last 30 years. Paralleling these advances, clinical indications for corneal transplantation surgery have also expanded considerably.

Fig. 21.16 Square penetrating graft, performed by Dr. Ramon Castroviejo in 1962 for keratoconus, remains clear 33 years later (photograph taken in 1995).

The last decade witnessed a strong expansion in the use of lamellar techniques.

The anterior lamellar keratoplasty performed with deep stromal separation, described by Melles (DALK) enables the surgeon to leave the recipient with healthy endothelium, with good visual results27,28.

Endothelial decompensation being the leading indication for PK procedures29–34, there has been strong interest in developing a technique able to preserve the healthy recipient stroma.

Since the original description of the posterior lamellar keratoplasty (PLK) described by Tillett and Barraquer in the 1950s and 1960s, in 1999 Melles demonstrated the first sutureless PLK35. Since then, numerous modifications in surgical technique and new instruments have led to increasing popularity of PLK.

Indications

Indications for keratoplasty have varied over the decades36–38. Box 21.1 lists the classical indications for PK; today many of these conditions may be effectively treated with LK. The Eye Bank Association of America recorded over 41 000 transplants performed in the United States in 2008, with a simultaneous increase in grafts provided for endothelial keratoplasty38. Whilst keratoconus and aphakic bullous keratopathy were major indications for corneal transplantation three decades ago, pseudophakic bullous keratopathy (PBK) rapidly emerged as a leading indication in the 1980s and 1990s38–41. This coincided with the dramatic increase in the number of cataract extractions performed. Optical indications for transplantation include corneal decompensation (e.g. bullous keratopathy and endothelial dystrophies), ectasia (e.g. keratoconus), scarring (e.g. traumatic, post-infectious or iatrogenic), and stromal dystrophies. Tectonic indications (e.g. melting, descemetoceles, perforation) are aimed primarily at preserving globe integrity and may allow optical improvement simultaneously or at a later stage. Therapeutic indications (e.g. medically unresponsive infections) provide the two-fold advantage of excisional biopsy and of elimination of the infected tissue. Causative organisms in these cases are often fungi or acanthamoeba, however, common pathogens causing microbial keratitis may also necessitate therapeutic keratoplasty.

Eye banking/donor selection

The first successful human corneal transplant by Eduard Zirm in 1905 involved the use of fresh corneal tissue from a boy whose eye was enucleated for a penetrating sclera injury. For approximately the following 30 years, all human keratoplasties were performed using fresh corneal tissue from living donors whose eyes had been enucleated due to trauma or disease not involving the anterior segment. In 1937, Filatov from the Ukraine introduced the use of whole globes from cadavers stored at 4°C in a moist chamber. Paton established in the US the first eye bank that involved procurement, processing, and distribution of donor corneas37.

Today, cold storage, organ culture, or cryopreservation may be used to preserve the corneoscleral buttons. Cryopreservation allows the tissue to stay viable at –70°C for more than 1 year; however, this is seldom used as it is expensive and technically complicated. Both the freezing and thawing procedures in this technique demand fastidious timing and special precautions to avoid damage to endothelial cells.

Thus, cold storage and organ culture are the two main methods for preserving the donor tissue today. Cold storage (2–6°C) was introduced in 197442,43, and is commonly used in the USA. The technique is relatively simple and involves refrigeration with minimal tissue handling. No complex equipment is required. At 2–6°C, the metabolic activity of the endothelial cells is minimal and therefore deturgescent agents (e.g. dextran or chondroitin sulfate) are required to keep the cornea in a relatively dehydrated state and thus maintain corneal thickness. The original McCarey-Kaufman (M-K) medium has been modified with addition of antibiotics, energy sources, antioxidants, growth factors, and membrane stabilizing agents to improve cell survival, reduce autolysis, and maintain ultrastructural integrity. Although endothelial cell loss may be attributable to numerous factors independent of storage technique, corneas stored at 2–6°C show intercellular disruption, reduced cell adhesion as well as endothelial cell loss and death44. Modified storage media have increased the storage time for up 2 weeks, one week being most often recommended. Organ culture (31–37°C) was introduced in 197645 and is commonly used in Europe. During the storage phase in culture medium supplemented with fetal or newborn calf serum, antibiotics and antimycotics, the corneas swell considerably and can reach twice the normal thickness. Dehydrating molecules are not added as they are ingested by the corneal cells and lead to toxicity. Thus, a shorter second phase is required to reverse the swelling prior to transplantation. Dextran (4–8%), is added to the same medium to facilitate de-swelling and transportation. This phase in transport medium varies between 1 and 7 days. Overall, organ culture allows for longer periods of storage (up to 4–5 weeks). Advantages over cold storage include ease of scheduling surgery, allowing time for tissue typing/matching, and more rigorous microbiological testing.

Regardless of the storage methods used, donor and tissue evaluation to assess suitability is critical. It includes obtaining a thorough medical and social history of the donor as well as serological testing, slitlamp biomicroscopy, and endothelial cell examination. The tissue is evaluated for epithelial integrity, epithelial and stromal opacities, presence of foreign bodies and infectious infiltrates, evidence of previous anterior segment surgery, degree of stromal clarity and thickness, presence of Descemet’s membrane folds and extent of endothelial guttae, snail tracks, and precipitates. Specular microscopy provides detailed microscopic analysis of individual cell morphology and an estimate of cellular density (Fig. 21.17A), however for a better and wide examination light microscopy is applied (Fig. 21.17B). The cell counts may be obtained by automated image analysis or manual counting methods.

Fig. 21.17 (A) Specular micrograph and (B) light microscopy showing healthy donor cells with a compact cellular pattern and uniform hexagonal shapes.

Donor tissue has to be considered as non-sterile and effective decontamination must be in the routine. Antibiotics are less effective in cold storage than organ culture as the contaminating microbes are metabolically less active at low temperatures. For this reason, preoperative warming of the storage media is important to enhance the decontamination effect. Individuation of microbial contamination may also be better with organ culture since contamination will become more readily evident and it may therefore be considered as the storage method of choice in circumstances where corneas are suspected of being at a higher risk of contamination. However, stringent screening protocols by eye banks have minimized the risk of microbial transmission from donor to recipient and the accurate valuation of medical and social history of the donor allowed rare incidences of systemic disease like rabies, hepatitis B, Creutzfeldt–Jakob disease (CJD) and malignancies44–48. No case of seroconversion after unplanned transplantation of corneas from human immunodeficiency virus (HIV) positive patients has been reported to date49–51.

Irrespective of the storage methods, prospective studies analyzing short and long-term follow-up after PK have not found any difference in endothelial cell density or clinical outcomes52–54.

Preoperative evaluation

Penetrating keratoplasty

Although the surgical steps vary among surgeons, a preliminary preparation of the recipient eye is usually performed first. The donor tissue should then be completely prepared for transplantation before the recipient eye is surgically opened as an obvious precaution when just one tissue is available in the OR, and in general to minimize the duration of open-globe time.