Chapter 58 - Ocular surgery part II Flashcards
1
Q
What are the risks associated with corneal lacerations?
A
Vision and globe-threatening complications, infection, and compromised eye structure.
2
Q
What do you check in ophtalmic exam when there is corneal laceration?
A
iris involvment
Lens and retina damage
3
Q
How can iris involvement in a corneal wound complicate repair?
A
It increases risks like hyphema and endophthalmitis.
4
Q
How can iris involvement in a corneal wound complicate repair?
A
It increases risks like hyphema and endophthalmitis.
5
Q
concurrent trauma to the lens can result in what?
A
catarat formation and varying degree of uveitis if the lens capsule has been lacerated due to inflammatory reaction
6
Q
Retinal detachmente due to coup-contrecoup injure can result in loss of globe pressure how is anmed?
A
(hypotony) occurring with leakage of aqueous humor and globe deflation when the eye is penetrated.
7
Q
Uncomplicated corneal lacerations may be repaired by primary closure using
A
simple-interrupted absorbable 8-0 to 9-0 sutures of polyglactin 910 with a spatulated needle.
8
Q
Why is foreign body depth assessment crucial in corneal injuries?
A
Removing deep-penetrating foreign bodies can collapse the anterior chamber.
9
Q
What is the preferred anesthetic setting for surgical repair of corneal lacerations?
A
Under general anesthesia with magnification.
10
Q
Describe how the spatulated semi-circular needle is inserted
A
the spatulated semi-circular needle is rotated in a circular path with no linear pushing, beginning with an entry angle of the needle point close to 90 degrees to the corneal surface. Sutures should be placed symmetrically 1 to 2 mm apart, ensuring the anterior chamber is not entered by the suture.
11
Q
What is required to maintain an anterior chamber during corneal repair?
A
Reinflation with balanced salt solution or a viscoelastic agent (sodium hyaluronate 2%).
12
Q
What is the risk if a suture accidentally enters the anterior chamber?
A
Possible damage to the iris and lens, and complications from hypotony
13
Q
What is the recommended tool for manipulating a prolapsed iris?
A
A blunt spatula or muscle hook. Iris prolapsed should be gently manipulated back into the anterior chamber using blunt spatula or muscle hook while the corneal wound is being closed.
14
Q
What should be avoided if the iris is incarcerated in the wound?
A
Excising the prolapsed iris to prevent hyphema and synechia.
15
Q
How can hemorrhage in the iris be minimized during surgery?
A
By applying diluted epinephrine (0.1 mg/mL)
and a viscoelastic agent.
16
Q
What is indicated if corneal tissue is missing and primary closure isn’t possible?
A
A conjunctival graft or other graft materials like amniotic membrane.
17
Q
What postoperative therapy is required if the anterior chamber is opened?
A
Systemic antibiotics and topical anti-inflammatories.
18
Q
What is the prognosis for uncomplicated corneal lacerations without globe penetration?
A
Good, with minimal scarring.
19
Q
Why is prognosis more guarded if there is iris prolapse and large aqueous leakage?
A
There’s a higher risk of damage to intraocular structures and subsequent complications.
20
Q
What postoperative complications are possible in corneal laceration repair?
.
A
Infection, scarring, astigmatism, suture dehiscence, and globe collapse
21
Q
What tools and techniques are essential for advanced surgical corneal repairs?
A
General anesthesia, magnification, good illumination, and microsurgical instruments.
22
Q
What purpose does a conjunctival graft serve in corneal repair?
A
It provides structural support and vascular supply, promoting healing.
23
Q
What kind of corneal issues are conjunctival grafts typically used for?
A
Deep corneal ulcerations, melting ulcers, and corneal lacerations. Where the corneal lesion is deep, or if the dissection inadvertently proceeds to greater than 50% stromal depth, a graft will be indicated.Deep corneal stromal abscessation, corneal malacia, corneal perforations, and iris prolapse.
24
Q
Why is thin conjunctival dissection important in grafting?
A
It reduces the risk of graft dehiscence and improves visual and cosmetic outcomes.
25
How much larger than the defect should a conjunctival graft be?
About 1–2 mm larger to accommodate contraction.
26
What should be removed if the corneal epithelium has grown around an ulcer before grafting?
The overgrown epithelium to expose the corneal stroma.
27
Which suture pattern is preferred for attaching a conjunctival graft?
Simple-interrupted suture pattern with polyglactin 910.
28
How should a defect in the graft created by scissors be addressed?
Close the defect with simple-interrupted sutures.
29
What are some types of conjunctival grafts?
Advancement grafts, hood grafts, and rotational pedicle grafts.
30
What additional materials may be needed for deep corneal defects?
Scaffolding materials like amniotic membrane or porcine submucosa.
31
What medications are typically used postoperatively after conjunctival grafting?
Broad-spectrum topical antibiotics, antifungals, and systemic NSAIDs.
32
What is the main complication associated with conjunctival grafting?
Graft dehiscence due to inflammation and improper grafting technique.
33
What strategy helps minimize graft dehiscence?
Minimizing postoperative inflammation and using proper suture depth.
34
Why is minimizing graft tension important?
It helps prevent graft dehiscence and ensures proper integration.
35
What issue can arise if collagenase activity continues post-grafting?
Melting of the surrounding cornea, leading to graft failure.
36
How can graft-induced scarring affect vision?
Large or centrally located grafts may significantly impair vision.
37
When should the attachment stalk of a conjunctival graft be trimmed?
About 6 weeks postoperatively to reduce scarring.
38
Why should forceps be avoided when trimming the graft stalk?
To reduce risk of trauma from head movement during trimming
39
What is the purpose of applying phenylephrine during stalk trimming?
To control hemorrhage.
40
ow long should postoperative topical antimicrobials be used after grafting?
Typically for about 2 weeks to support healing and prevent infection.
41
what is a rotational pedicle graft commonly used for?
For treating both centrally and peripherally located corneal defects.
42
Why is rotational pedicle graft considered versatile?
It suits various corneal defects and offers flexibility in donor site location.
43
What is essential in planning a rotational pedicle graft?
Ensuring the graft pedicle is of adequate length without excessive tension.
44
Why is the lateral or dorsal bulbar conjunctiva preferred as a donor site?
It is easier to expose and has less risk of trauma, improving graft success.
45
How should the patient be positioned during rotational graft surgery?
In lateral recumbency to centralize the corneal position.
46
Why is graft harvesting typically done before corneal débridement?
To allow rapid closure in case of inadvertent globe penetration.
47
What is the initial incision location in rotational graft harvesting?
Parallel to and 1-2 mm from the limbus at the flap’s apex.
48
Why is it important to maintain a thin flap during harvesting?
To prevent excessive tissue and reduce tension on the graft.
49
What blade is used to prepare the recipient bed?
A 69 Beaver blade.
50
What type of suture is typically used to secure the graft in place?
Simple-interrupted 8-0 to 9-0 polyglactin 910.
51
What additional precaution is needed when placing sutures?
Ensure sutures go through the conjunctiva before the corneal lesion edge.
52
What differentiates an advancement pedicle graft from a rotational graft?
It is used for corneal lesions closer to the limbus.
53
Why aren’t advancement pedicle grafts ideal for central corneal defects?
Limited flap length creates tension, restricting central defect coverage.
54
What is the first incision in an advancement pedicle graft?
Parallel to the limbus, slightly longer than the defect’s width.
55
Why isn’t donor site closure necessary in advancement pedicle grafts?
The advanced conjunctiva naturally covers the site.
56
What is a hood graft mainly used for?
For lesions adjacent to the limbus.
57
What is unique about a hood graft’s attachment process?
It can provide temporary coverage and eventually detaches on its own.
58
How is a hood graft positioned relative to the corneal epithelium?
It may overlay the intact corneal epithelium for temporary protection.
59
What are bipedicle and bridge grafts used for?
For linear corneal defects or axially located lesions.
60
How is a bipedicle graft secured?
By suturing the graft tips over the lesion.
61
What is a potential drawback of a bipedicle graft?
It may offer a less secure attachment than other graft types.
62
How is a bridge graft different from a bipedicle graft?
It anchors on either corneal side, reducing need for central sutures.
63
What should be done after a bipedicle or bridge graft?
Close the donor sites with simple-continuous sutures.
64
What is amniotic membrane transplantation primarily used for?
Promoting corneal wound healing and reducing inflammation.
65
What layers make up the amniotic membrane?
Epithelial layer, basement membrane, and stromal matrix.
66
How should a frozen amniotic membrane be prepared?
Thaw and wash in balanced salt solution for 30 minutes.
67
What are the two main types of amniotic membrane grafts?
Inlay graft and overlay patch.
68
What is the orientation for an inlay graft of the amnion?
Epithelial/basement membrane side facing upwards.
69
What role does an overlay patch serve?
Temporary structural support and inflammation reduction.
70
What is required if the overlay patch does not detach?
Removal from the cornea in about two weeks.
71
What is the primary complication of an amniotic membrane transplant?
Infection spread beneath the membrane.
72
What is the goal of sliding lamellar keratoplasty?
Repair superficial central corneal defects while preserving the conjunctiva or sclera.
73
What is the difference between sliding lamellar and corneoconjunctival transposition?
The latter preserves scleral integrity.
74
How is the recipient bed prepared in sliding lamellar keratoplasty?
Débridement of necrotic cornea to a square recipient bed.
75
What incision tool is recommended for lamellar dissection?
A No. 64 or No. 69 Beaver blade.
76
What is a disadvantage of sliding lamellar keratoplasty compared to pedicle grafts?
Lack of immediate vascular supply to the ulcer bed.
77
Why might partial-thickness grafts be unsuitable for deep lesions?
They lack structural integrity compared to full-thickness grafts.
78
What is a potential consequence of neovascularization in sliding lamellar grafts?
Reduced corneal transparency.
79
Why should conjunctiva trimming be avoided after corneoconjunctival transposition?
It could interfere with graft integration.
80
What is the primary advantage of an inlay amniotic membrane graft?
Less scarring and better corneal transparency than conjunctival grafts.
81
What type of suturing is often used in corneal and conjunctival graft placement?
Simple-interrupted pattern using polyglactin 910.
82
Figure 58-11. 4.0× surgical loupes with light source (Heine).
83
Figure 58-12. Instruments commonly used for conjunctival surgery, from left to right: Westcott tenotomy scissors, Stevens tenotomy scissors, Bishop-Harmon forceps, Derf needle holder.
84
Figure 58-13. Guyton-Park eyelid speculum.
Figure
85
Figure 58-14. Instruments commonly used for corneal surgery, from left to right: Castroviejo needle holder, Colibri corneal forceps, Martinez corneal dissector, Castroviejo corneal section scissors, Castroviejo universal corneal scissors, straight suture-tying forceps, curved suture-tying forceps.
86
Figure 58-15. Beaver scalpel blades and Beaver handle, from left to right: No. 69 blade, No. 65 blade, No. 64 blade, blade handle.
87
Figure 58-16. (A) Correct placement of sutures to a depth of 80% of the cornea. (B) Close-up view.
88
Figure 58-16. (A) Correct placement of sutures to a depth of 80% of the cornea. (B) Close-up view.
89
90
Figure 58-19. Cellulose ocular stick (top), and Weck-Cel cellulose sponge spear (bottom).
91
Figure 58-20. Protective eye-cup mask to prevent damage to the surgical site.
92
Figure 58-21. Intraoperative image of a superficial keratectomy performed with a 69 Beaver blade and Martinez corneal dissector.
93
what is the typical corneal depth?
typical corneal thickness of 0.7 mm
94
Figure 58-22. Ophthalmic cryoprobe tips (Cooper-surgical N2O cryotherapy unit) suitable for direct ocular surface application for adjunctive therapy of ocular surface neoplasia.
95
96
If corneal tissue is missing or primary closure is not possible what should the surgeon consider?
1. placement conjunctival pedicle graft
2. transplanted cornea
3. aminoic membrane
4. porcine small intestine submucosa
97
what does the conjunctival grafting provide as structural support for the corneal defect?
This provides structural support and a vascular supply to the lesion bringing anticollagenases, fibroblasts, and growth factors that facilitate healing
98
how do you collect the conjuntival graft?
the conjunctiva needs to be incised and carefully undermined with fine blunt-tipped tenotomy scissors to create a thin flap of conjunctiva. Using a combination of sharp and blunt dissection, the thin conjunctival flap is separated from underlying Tenon’s capsule
99
how can the risk of dehiscence of the conjunctival graft be avoided?
an also be reduced by ensuring the graft is large enough to cover the defect without being under significant tension
100
the conjuntival graft should be what size ?
To ensure adequate coverage of the corneal lesion, the graft should ideally be slightly larger (1–2 mm) than the defect because it tends to contract.
101
does the conjuntiva adhere to epithelium?
no, conjunctiva will not adhere to an epithelialized surface, so in instances where the epithelium has grown down the edges of an ulcer, it should be carefully removed to expose the corneal stroma to which the conjunctiva can adhere. A 69 Beaver blade can be used to débride the epithelium, or in some instances it can be peeled back using corneal forceps.
102
needle passes through the cornea and then graft or graft and then cornea?
graft and then cornea
103
what is the required depth of the sutures in the corne for adequate anchorage of the graft?
ensuring that the sutures are placed to a depth of 60% to 80% of the cornea for adequate anchorage of the graft along its margins,
104
The main complication associated with conjunctival grafting is
graft dehiscence.
105
which sites are easiest to harvest conjuntiva?
The surgeon will find it is easiest to harvest the graft from lateral and dorsal bulbar conjunctiva, rather than the medial or ventral conjunctiva, because of the presence of the third eyelid and because these aspects of the globe are often easiest to expose as a result of the effects of anesthesia on globe position
106
graft s harvested before or after corneal debridement?
referable that the graft is harvested prior to corneal débridement to allow rapid closure should inadvertent globe penetration occur during this process
107
describe the surgical procedure of harvesting the bulbar conjuntiva
Harvesting of the bulbar conjunctiva is performed using tenotomy scissors and should commence with an incision placed parallel to and approximately 1 to 2 mm from the limbus at the planned apex of the flap
The incision is extended perpendicular to the limbus at a distance 1 to 2 mm greater than the width of the corneal lesion thin flap of conjunctiva is carefully undermined and isolated from underlying Tenon’s capsule. A third incision is made with tenotomy scissors parallel to the first incision to create a three-sided flap of consistent width and a length determined by the distance of the lesion from the limbus (Figure 58-24). The pedicle should be laid over the corneal defect to ensure there is not excessive tension on the graft prior to suturing; the length of the graft can then be extended if necessary. The recipient bed is prepared by removing fibrin, malacic cornea and any epithelium that has grown into the defect using a 69 Beaver blade. The graft is then sutured into the recipient bed with a simple-interrupted pattern of 8-0 to 9-0 polyglactin 910 using the technique of corneal suturing described earlier. the defect created in the conjunctiva should be sutured closed in a simple-continuous pattern using the same suture as for the graft placement (Figure 58-25).
108
109
What are the primary indications for corneal grafting procedures?
Deep corneal stromal abscessation, corneal malacia, corneal perforations, and iris prolapse.
110
What is the main purpose of corneal transplantation?
To restore structural integrity to the globe and facilitate healing after corneal damage.
111
What key complication can arise due to the allografting nature of corneal transplantation?
Graft rejection, marked by edema, vascularization, and scarring.
112
Why does graft rejection occur even though the cornea is an immune-privileged site?
Pre-existing corneal infection and neovascularization increase inflammatory response, triggering rejection.
113
How does graft size and location affect the inflammatory response?
Smaller grafts located in clear cornea, away from the limbus, induce a less severe inflammatory response.
114
What is preferred, fresh or frozen donor corneal tissue, and why?
Fresh tissue is preferred as freezing damages endothelial cells, causing opacification.
115
What role does the viscoelastic agent play during corneal transplantation?
It helps maintain the anterior chamber, reducing the risk of hypotony and facilitating manipulations.
116
How is a donor corneal button oriented in the recipient site?
With the endothelial side facing the anterior chamber.
117
Why might some surgeons add an amniotic membrane or conjunctival graft over the cornea in PK?
For additional security and to aid in graft incorporation, though it may increase scarring.
118
Advancement pedicle grafts are good for central corneal defects?
No, pedicle graft are ideal for corneal lesions located close to the limbus because the length of the flap cannot go to the centre without tension
119
describe surgical tx for advancement of pedicle graft
The procedure commences with an incision made in the bulbar conjunctiva adjacent to the corneal lesionshould be 1 to 2 mm longer than the width of the defect, parallel to the limbus. Subsequently, the bulbar conjunctiva is carefully undermined before the final two incisions are made perpendicular to the limbus and slightly diverging from each other as they extend toward the fornix for a length determined by the distance of the apex of the lesion from the limbus. As the dissection proceeds toward the fornix, maintaining a thin conjunctival graft can become more difficult and attention should be paid to ensure the conjunctiva is isolated from the underlying tissues. Once a graft of appropriate length has been harvested, the mobilized flap of conjunctiva can be sutured to the cornea, utilizing the techniques and principles described earlier. Preparation of the recipient bed should be performed immediately prior to suturing the graft,
Closure of donor site not needed
120
Hood grafts are used to cover lesions adjacent to the
limbus
121
Please describe the hood graft
With this technique, a single incision is made 1 mm from the limbus, and the conjunctiva is undermined and advanced axially to cover the lesion (Figure 58-26). After débridement and removal of the epithelium from the area to be covered, the graft is sutured to healthy cornea just beyond the margin of the lesion. In instances where temporary protection is desired, the underlying corneal epithelium is left intact and the hood graft will often detach from the area over the subsequent weeks.
122
Which situations are ideal the bipedicle and bridge grafts?
linear corneal defects and for axially located lesions
123
Figure 58-26. Hood conjunctival graft. (A) An incision is made 1 mm from the limbus, and the bulbar conjunctiva is undermined toward the fornix. (B) Both ends of the graft are sutured to the adjacent limbus. (C) The hood is advanced and sutured to the cornea.
124
Figure 58-27. Bridge conjunctival graft. (A) Bulbar conjunctival incisions parallel to the limbus, undermined and isolated from underlying Tenon’s capsule. (B) The bridge of conjunctiva is sutured to the cornea along two sides of the corneal ulcer.
125
describe the surgical tx of bipedicle graft
The technique for creating a bipedicle graft involves harvesting two conjunctival pedicle grafts with their bases located 180 degrees apart, allowing the tips of the graft to meet over the center of the lesion without excessive tension on either flap. The grafts are secured to each other by placement of simple-interrupted or continuous sutures between the two graft tips; this results in sutures placed over the lesion and a potentially incomplete seal.
The graft is secured to the cornea on the two remaining sides with interrupted sutures using the technique described earlier, although the result is a less secure attachment relative to the three-sided attachment of a pedicle or advancement graft. The donor sites should both be closed with a simple-continuous suture pattern as described earlier. A bridge graft is similar to a bipedicle graft, being anchored at either side of the cornea and achieving a similar outcome, although it may be a preferable technique. Two 140- to 180-degree bulbar conjunctival incisions are made parallel to the limbus and separated by a distance 1 to 2 mm wider than the lesion. The graft is secured to the cornea on two sides in a similar fashion to a bipedicle graft but without the need for additional sutures located over the lesion. The donor site is closed as described previously (Figure 58-27).
126
Amniotic membrane transplantation can be performed as an inlay graft, as an alternative to a
conjuntival pedicle graft
127
Similar to cornea and conjunctiva it contains collagen
Similar to cornea and conjunctiva it contains collagen IV, V, and VII and growth factors that can stimulate epithelializatio
128
The amniotic membrane graft should be 1 to 2 mm larger than the corneal defect and oriented epithelium/basement membrane side ____________ (upwards/downwards)
The amniotic membrane graft should be 1 to 2 mm larger than the corneal defect and oriented epithelium/basement membrane side upwards
129
Figure 58-28. Sliding lamellar keratoplasty. (A) Diverging corneal incisions extending from the lesion into the conjunctiva, a Martinez corneal dissector is used to elevate the flap of cornea, and tenotomy scissors are used to undermine the bulbar conjunctiva. (B) The graft is advanced over the defect and sutured along the edges of the incisions.
130
what is a sliding lamellar keratoplasty (corneoconjunctival transposition)
A sliding lamellar keratoplasty is the advancement of a partial-thickness graft of healthy peripheral cornea into a central corneal defect while preserving its conjunctival or scleral attachment
131
describe the sliding lamella keratoplasty
The surgeon begins by débriding necrotic cornea from the lesion to create a square healthy recipient bed. A No. 64 or No. 69 Beaver blade is then used to perform two diverging partial-thickness corneal incisions, extending from the site of the lesion 1 mm into the conjunctiva beyond the limbus. Using a Martinez corneal dissector or a Beaver blade, the superficial cornea delineated by the two incisions is separated from the underlying deeper corneal stroma at the required thickness. To facilitate dissection, the leading edge of the cornea can be grasped with corneal forceps, although handling should be minimized. When the dissection has passed the limbus, it is extended into the subconjunctival tissue, leaving the flap of cornea to be advanced attached to the conjunctiva. The conjunctiva is isolated from Tenon’s capsule using blunt dissection with tenotomy scissors. The graft can then be advanced into the lesion and sutured in place with 8-0 to 9-0 polyglactin 910 in a simple-interrupted pattern (Figure 58-28).
132
what is a penetrating keratoplasty (PK)?
A penetrating keratoplasty (PK) is the surgical placement of a full-thickness donor corneal button into the recipient tissue.
133
How is a donor corneal button oriented in the recipient site?
With the endothelial side facing the anterior chamber.
134
what instrument do you use to measure the recipient tissue to prepare corneal donot button?
Jameson calipers
135
Why might some surgeons add an amniotic membrane or conjunctival graft over the cornea in penetrating keratoplasty PK?
o restore structural integrity to the globe and facilitate healing after corneal damage.
136
What is the reasons for penetrating keratoplasty?
lesions involving much thickness of the cornea such as abscessation
or iris prolapse
137
Donor corneal tissue can be harvested fresh from
horses euthanized for nonocular and nonneurologic conditions or stored frozen.
138
how is performed the corneal button harvesting?
the donor cornea should be placed epithelial side down on a Teflon block, and a button should be removed with a corneal trephine or disposable punch biopsy.
139
for focal corneal lesions less than 8 mm in diameter what is the prefereed procedure?
split-thickness procedures, posterior lamellar keratoplasty (PLK - lesions close to central corneal), and deep lamellar endothelial keratoplasty (DLEK - lesions close to the limbus) are preferred
140
In postoperative treatment similar as conjunctival grafting the topical AB antifungal mydriatic and _____ to reduce graft rejection are given for 4 weeks
cyclosporine
141
describe the surgical tecnique of penetrating keratoplasty PK
Before commencing the procedure, the lesion should be measured with Jameson calipers and the prepared corneal donor button should be 1 mm larger in diameter than the intended recipient site. With proper corneal positioning and central globe exposure achieved, a corneal trephine or disposable biopsy punch is used to incise the cornea to a depth of 95% of the stroma. The incision is then continued with a No. 65 or No. 69 Beaver blade to penetrate the anterior chamber and remove the button of diseased corneal tissue. A viscoelastic agent is used to reform and maintain the anterior chamber, facilitating manipulations of the cornea and reducing the risk of hypotony. The donor button is sutured into position as described earlier and the viscoelastic agent is not removed from the anterior chamber (Figure 58-29).
142
How is a donor corneal button oriented in the recipient site?
With the endothelial side facing the anterior chamber.
143
Why might some surgeons add an amniotic membrane or conjunctival graft over the cornea in PK?
For additional security and to aid in graft incorporation, though it may increase scarring.
144
What is the prognosis for horses with inflammatory keratopathy treated with PK?
Generally good, with a visual outcome reported in 78% of cases.
145
Describe the modified PK involving porcine bladder submucosa and its success rate.
It uses porcine bladder submucosa with conjunctival pedicle overlay, with an 86% visual outcome success rate.
146
For which type of lesions is Posterior Lamellar Keratoplasty (PLK) suitable?
Deep stromal abscesses less than 8 mm in diameter affecting Descemet's membrane and endothelium.
147
Why is PLK preferred over PK for certain lesions?
It leaves healthy anterior corneal tissue intact, reducing scarring and dehiscence risk.
148
In PLK, how is the diseased tissue removed?
With a corneal trephine and Beaver blade, along with a viscoelastic agent to maintain chamber integrity.
149
What is the typical outcome for PLK in terms of vision preservation?
Positive visual outcome in 98% of cases.
150
Figure 58-30. Posterior lamellar keratoplasty. A three-sided incision is created with a 69 Beaver blade and undermined with a Martinez corneal dissector. A punch biopsy is used to delineate the circular deep stromal lesion. The lesion is removed and a button of donor tissue is sutured into the resulting defect. The anterior flap is subsequently sutured closed.
151
Where is Deep Lamellar Endothelial Keratoplasty (DLEK) primarily used?
For deep lesions less than 8 mm in diameter near the limbus.
152
What advantage does DLEK offer over PLK?
It avoids central corneal incision, potentially reducing scarring.
153
describe DLEK tx
The procedure utilizes a limbal-based corneal incision avoiding the superficial central corneal incision and sutures of a PLK, which may reduce corneal scarring.137,139 A partial-thickness donor corneal button is prepared as for a PLK. A limbal incision is then made with a No. 64 or No. 69 Beaver blade adjacent to the lesion and undermined with a Martinez corneal dissector to create a superficial corneal flap. The flap is then gently retracted and a corneal trephine and Beaver blade used to excise the diseased cornea from the recipient bed, with a viscoelastic agent used to maintain the anterior chamber. Once the abnormal cornea has been removed, the limbal incision is partially closed and the donor corneal button then inserted with Utrata forceps and manipulated into position with a needle and limbal injection of a viscoelastic agent prior to complete closure of the limbal flap. The donor cornea is left unsutured and adheres to the adjacent healthy corneal stroma. Alternatively, the donor graft can then be sutured in place as for a PLK. The viscoelastic agent is not removed from the anterior chamber (Figure 58-31).
154
Describe the donor corneal button preparation for DLEK.
A partial-thickness donor button is prepared similarly to PLK.
155
How is the anterior chamber maintained in DLEK during excision of diseased tissue?
A viscoelastic agent is used to keep the chamber intact.
156
What is the reported visual outcome success rate for DLEK?
Positive visual outcome in 89% of cases.
157
How does the donor graft adhere in DLEK if left unsutured?
It adheres naturally to adjacent healthy corneal stroma.
158
What alternative approach in DLEK allows for improved adhesion without sutures?
Injection of a viscoelastic agent at the limbus enhances graft position and adherence.
159
What medications are typically used postoperatively to prevent graft rejection?
Topical antibiotics, antifungals, mydriatics, and cyclosporine.
160
Why are systemic antimicrobials administered postoperatively in corneal grafts?
Due to anterior chamber entry, which increases infection risk.
161
How does graft rejection manifest clinically?
As edema, vascularization, and scarring of the graft.
162
Why might PLK be preferred for lesions away from the limbus?
It limits central corneal scarring by preserving anterior corneal stroma.
163
Which surgical tool is used to remove donor corneal buttons?
A corneal trephine or disposable punch biopsy tool.
164
What technique minimizes hypotony risk during penetrating keratoplasty (PK)?
Using a viscoelastic agent in the anterior chamber.
165
How does a conjunctival graft over PK affect visual outcomes?
It increases scarring, potentially limiting vision.
166
What specific depth is typically achieved with the corneal incision in PK?
95% of stromal depth.
167
Why might a surgeon use a full-thickness graft in PK?
For severe corneal lesions, like abscessation or iris prolapse.
168
What condition might necessitate lamellar techniques over PK?
Smaller, localized deep stromal lesions with minimal surface involvement.
169
What is a common postoperative complication of PLK and DLEK?
Vascularization, scarring, and graft ulceration.
170
Why is DLEK preferred for peripheral corneal lesions?
It avoids central corneal incision, preserving visual clarity.
171
What special preparation is required for fresh corneal tissue?
Removal of epithelium if used fresh; otherwise, freezing for later use.
172
What is a critical success factor in all corneal grafting procedures?
Precise suturing to minimize tension and maintain graft stability.
173
What can increase the risk of rejection in corneal grafting?
Pre-existing infection or corneal neovascularization.
174
What is a surgical outcome measure for successful corneal grafting?
clear visual axis with minimal scarring or vascularization.
175
What is the role of Teflon blocks in corneal transplantation?
Support the donor cornea for trephine incision.
176
Figure 58-31. Deep lamellar endothelial keratoplasty. A limbal-based incision is undermined with a Martinez corneal dissector and elevated. A punch biopsy delineates the circular deep stromal lesion. The button of donor tissue is placed into the resulting defect without suturing. The anterior flap is sutured closed at the limbus.
177
t is the visual otucome from DLEK?
a positive visual outcome was reported in 89% of cases.137 A separate study has described a positive visual outcome with minimal scarring in 100% of cases.
