Trauma and Reconstructive Surgery
Iliff N, Manson PN, et al (Univ of Maryland, Baltimore, Harvard Med School, Boston)
Mechanisms of Extraocular Muscle Injury in Orbital Fractures
Plast Reconstru Surg 103: 787-799, 1999
This was studied in animals, cadavers and at the time of exploration of orbital fractures.
It was found that compartment syndrome supposed to be produced by entrapment of muscles, was not true concept of diplopia, but muscle contusion, scarring and incarceration are the cause of diplopia.
H.S. Dua, A J King, Annie Joseph (Univ. Hospital, Queen’s Medical Centre, Nottingham, UK)
A new classification of ocular surface burns.
BJO, 2001; 85: 1379-1383
Thermal and chemical burns represent potentially blinding ocular injuries.
Thermal burns results from (i) firework explosions (ii) steam (iii) boiling water (iv) molten metal (commonly aluminium).
Chemical burns may be from alkaline or acidic agents. Alkaline agents include (i)Ammonium hydroxide (fertilizer production) (ii) Sodium hydroxide (for cleaning drains and pipes) and (iii) calcium hydroxide (found in lime plaster and cement).
Alkaline agents have both hydrophilic and lipophilic properties and hence rapidly penetrate cell membranes and enter the anterior chamber.
The hydroxyl ion causes saponification of cell membranes, cell death and disruption of the extracellular matrix.
Acidic agents causing injury are sulphuric acid found in car batteries, sulphurous acid found in some bleaches, and hydrochloric acid (swimming pools).
Recovery of ocular surface burns depends upon :
(i) causative agent
(ii) Extent of damage to (a) corneal, (b) limbal and (c) conjunctival tissues at the time of injury.
Understanding and clinical application of the concept of limbal stem cells of the corneal epithelium and forniceal stem cells of the conjunctival epithelium has significantly improved the outcome of treatment.
Limbal based epithelial stem cells provide a steady supply of daughter cells which maintain a constant epithelial cell mass during normal epithelial cell turnover and during epithelial wound healing.
Conjunctival stem cells are located in the forniceal region and migrate away from the fornices to cover bulbar and tarsal conjunctiva.
New developments in the management of severe ocular surface burns include (i)autolimbal transplantation or (ii) allolimbal transplantation with or without amniotic membrane graft.
This is combined with systemic immuno suppression and topical instillation of autologous serum.
The authors have evolved a new classification ranging from grade I (very good) to grade VI (very poor prognosis), based on the following parameters.
(a) Clock-hours of limbal involvement
(b) Percentage of conjunctival involvement.
The presence of any surviving conjunctival epithelium, is a favourable prognostic indicator (when compared with eyes with total loss of corneal, limbal and conjunctival epithelium).
The authors stress the important concept of conjunctivalisation of the cornea which protects against progressive melting and perforation. The ensuing vascularisation promotes healing and facilitates repair, which provides an opportunity to perform restorative procedures later.
The new classification is based on the authors’ experience of 67 cases of ocular surface burns managed over several years (35 retrospective and 32 prospective).
In Grade II of this new classification (when < 3 clock hours of limbus are involved and < 30% adjacent conjunctiva is involved) a good prognosis may be expected with medical management.
(i)copious irrigation soon after injury
(ii) topical vitamin C drops,
(iii) topical citrate drops
(iv) Acetylcysteine drops.
(v) Judicious steroids and
As long as there is even one clock hour of limbal epithelium surviving, there is a chance to re-establish corneal epithelial cover, over at least the visual axis.
When attributing a grade, the extent of the limbal involvement takes precedence over the extent of conjunctival involvement.
M.C. Nishiwaki-Dantas, P E Correa Dantas et al (Ocular Emergency Service, Sao Paulo, Brazil).
Ipsilateral limbal translocation for treatment of partial limbal deficiency secondary to ocular alkali burn.
BJO, 2001; 85: 1031-1033
Alkali burns may result in damage to limbal stem cells which are fundamental in maintaining ocular surface integrity.
Manifestations of limbal deficiency are:
(i) Abnormal conjunctival-corneal healing with peripheral neovascularisation.
(ii) Chronic epithelial defect
(iii) Severe stromal inflammation.
Penetrating keratoplasty has a poor prognosis in these cases.
Ipsilateral limbal autografts were performed in 5 patients with partial limbal deficiency secondary to alkali burn.
All cases had regression of limbal deficiency. Visual acuity improved to a minimum of 20/60 to 20/20 without complications during follow-up ranging from 7 to 11 months.