Ординатура / Офтальмология / Английские материалы / Basic Principles of Ophthalmic Surgery_Arnold_2006
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Figure 14.2 Tensile strength of healing central corneal wounds expressed in percentage of value for intact tissue. The numbers in parenthesis are error scores. (Reproduced with permission. From Gasset AR, Dahlman CH. The tensile strength of corneal wounds. Arch aphtha/mol.
1968;79:595-602.)
fills the wound site, proper careshould be givento apposethe wound edges to prevent epithelial down growth. A stromal reactionensueswith production of ECM by fibroblasts. The endotheliumhealsin a similar mannerto that describedfor all epithelial tissue.Initially, there is a migration of cells over the wound site.If there is compromise of the basementmembrane,in this case Descemet'smembrane,there is synthesisof a new one.
Due to the avascularnature of the cornea,incisionalwounds tend to heal slowly. Animal models show that centralcornealwounds with respectto time havelessthan 5% tensile strengthcomparedto that of intact tissueat1 week and 45% at2 months time (Figure 14.2).Also of importance is the fact that a denudedcornea significantly slowed underlying stromalhealing,demonstrated by a delay in gain of tensile strengthascomparedto wounded nondenuded corneas.Highlighting the importance of vascularsupply with respectto speed of healingis the fact that corneoscleralwounds showed 14% to 24% tensile strengthto that of intact tissue at1 weekand by 6weeksthe wound strength wasrecorded at 50% that of intact tissue.
Practical Considerations
Due to the nature of the tissueand its anatomicfunction, healingby primary intention (suture or glue closure)is required in full- andpartial-thickness cornealwounds. Epithelial injury, however,is usually left to healby secondary intention sincethe epithelial cellsmigrate overdenudedareasin a very short period. In fact, most epithelial injury is fully healedin 72hours.
As previously mentioned,the avascularnature of the corneais the single greatestobstacleto wound healingin this tissue.Therefore,the surgeonmust accountfor this fact in the choice of suture and technique. For instance,central
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MODIFYING WOUND HEALING
Scarringof any oculartissuecanresult in decreasedvision and a subsequent increasein patient morbidity. Current researchincludesmethodsto modify the stepsof wound healingto reducepoor visualoutcomes.
Suture Materials
A simple meansof modifying wound healingis in the choice of suture materials. If more rapid healingis desired,then suturescapableof inducing an inflammatory reactionareused.Theseinclude Vicryl, gut, and silk. If inflammation is not desirable,monofilament suturessuchasProleneand nylon may beused. In somesurgeriesit maybe desirableto do both. For example,in a limbal-basedtrabeculectomy,nylon suturesareusedto closethe scleralflap, asinflammation and scarringin this areaareundesirable,inhibiting aqueous flow around the flap. However, when closingthe conjunctiva, a Vicryl suture is usedto encourageinflammation atthe incision site to promote scarringand a watertight closure.Table14.1comparessuture materials.Also seeChapter 6 for additional information.
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