Lana A Faraj

Human corneal anatomy redefined: a novel pre-Descemet's layer (Dua's layer).

PURPOSE To define and characterize a novel pre-Descemets layer in the human cornea. DESIGN Clinical and experimental study. PARTICIPANTS We included 31 human donor sclerocorneal discs, including 6 controls (mean age, 77.7 years). METHODS Air was injected into the stroma of donor whole globes (n = 4) and sclerocorneal discs (n = 21) as in the clinical deep anterior lamellar keratoplasty procedure with the big bubble (BB) technique. The following experiments were performed: (1) creation of BB followed by peeling of the Descemets membrane (DM); (2) peeling off of the DM followed by creation of the BB, and (3) creation of the BB and continued inflation until the bubble popped to measure the popping pressure. Tissue obtained from these experiments was subjected to histologic examination. MAIN OUTCOME MEASURES Demonstration of a novel pre-Descemets layer (Duas layer) in the human cornea. RESULTS Three types of BB were obtained. Type-1, is a well-circumscribed, central dome-shaped elevation up to 8.5 mm in diameter (n = 14). Type-2, is a thin-walled, large BB of maximum 10.5 mm diameter, which always started at the periphery, enlarging centrally to form a large BB (n = 5), and a mixed type (n = 3). With type-1 BB, unlike type-2 BB, it was possible to peel off DM completely without deflating the BB, indicating the presence of an additional layer of tissue. A type-1 BB could be created after first peeling off the DM (n = 5), confirming that DM was not essential to create a type-1 BB. The popping pressure was 1.45 bar and 0.6 bar for type-1 BB and type-2 BB, respectively. Histology confirmed that the cleavage occurred beyond the last row of keratocytes. This layer was acellular, measured 10.15 ± 3.6 microns composed of 5 to 8 lamellae of predominantly type-1 collagen bundles arranged in transverse, longitudinal, and oblique directions. CONCLUSIONS There exists a novel, well-defined, acellular, strong layer in the pre-Descemets cornea. This separates along the last row of keratocytes in most cases performed with the BB technique. Its recognition will have considerable impact on posterior corneal surgery and the understanding of corneal biomechanics and posterior corneal pathology such as acute hydrops, Descematocele and pre-Descemets dystrophies. FINANCIAL DISCLOSURE(S) The authors have no proprietary or commercial interest in any materials discussed in this article.

Consensus statement on indications for anti-angiogenic therapy in the management of corneal diseases associated with neovascularisation: outcome of an expert roundtable

The cornea is the clear window at the front of the eye and is the eyes main refractive medium. Its transparency is essential for vision. Corneal neovascularisation is a common clinical problem with serious consequences for vision; it can compromise corneal transparency and plays a major role in corneal graft rejection by breaching corneal immune privilege. In this review, we formulate a consensus on the unmet medical needs in the management of corneal neovascularisation and outline a framework for the clinical research that is needed to identify suitable agents to meet these needs.

In vivo confocal microscopic features of normal limbus

Aim To describe in vivo confocal microscopy (IVCM) features of the limbus in normal eyes as related to the palisades of Vogts. Methods 46 eyes of 29 consecutive volunteers were recruited in this observational study. A detailed examination by IVCM was performed in addition to a routine slit-lamp biomicroscopy. Size and density of corneal and limbal epithelial cells were measured and statistically analysed using SPSS version 8.0 software. Results Anatomical and morphological features were noted between corneal and limbal cells. Size and density differences reached to significant levels (p<0.05). Different shapes of palisades of Vogt have been described clearly by confocal microscope. Cell-like structures were observed in the peripheral end of the palisades which might represent limbal stem cell crypts. Conclusions Laser IVCM can be used to establish the features of the normal limbus. The identified features demonstrate quantitative changes in the basal epithelium between the limbus and the central cornea and morphological differences between pigmented or non-pigmented studied subjects. Further studies should be performed to correlate with histology the possible crypts which were observed in this study.

The collagen matrix of the human trabecular meshwork is an extension of the novel pre-Descemet's layer (Dua's layer)

Background The trabecular meshwork (TM) located at the angle of the anterior chamber of the eye contributes to aqueous drainage. A novel layer in the posterior part of the human cornea has recently been reported (the pre-Descemets layer (Duas layer (PDL)). We examined the peripheral part of this layer in relation to the origin of the TM. Methods The PDL and TM of 19 human donor eyes and one exenterated sample were studied. Samples were examined by light and electron microscopy (EM) for tissue architecture and by immunohistology for four matricellular proteins, five collagen types and CD34. Results EM revealed that beams of collagen emerged from the periphery of PDL on the anterior surface of the Descemets membrane and divided and subdivided to continue as the beams of the TM. Long-spacing collagen was seen in the PDL and TM. Trabecular cells (CD34-ve) associated with basement membrane were seen in the peripheral part of the PDL and corresponded to the start of the separation of the collagen lamellae of PDL. Collagen VI was present continuously in PDL and extended into the TM. Matricellular proteins were seen predominantly in the TM with only laminin extending into the periphery of PDL. Conclusions This study provides an insight into the origins of the collagen core of the TM as an extension of the PDL of the cornea. This finding adds to the knowledge base of the TM and cornea and has the potential to impact future research into the TM and glaucoma.

Fine needle diathermy occlusion of corneal vessels

Aims To evaluate the efficacy of fine needle diathermy (FND) occlusion of corneal vessels in relation to defined clinical indications. Methods A retrospective, consecutive case series including all patients treated by FND for occlusion of corneal vessels between 2004 and 2012. Indications were lipid keratopathy, preparation for keratoplasty to reduce risk of rejection and treatment of recalcitrant corneal graft rejection associated with stromal vessels. Our outcome measures were occlusion of corneal vessels with reduced corneal vascularisation, reduction in amount of lipid deposition, and reduction of graft rejection episodes. Results FND effectively reduced lipid deposition associated with the treated vessels in 14 out of 17 eyes (82.3%). When used to reduce corneal vascularisation before keratoplasty and to reduce intraoperative bleeding, the 1-year survival of the high-risk grafts was (84.6%). FND prevented further rejection episodes in 3 out of 4 corneal grafts. Fourteen eyes required retreatment (2–5 times) of which 9 had lipid keratopathy and 5 were in preparation for corneal grafting. Conclusions FND is effective in occluding established corneal vessels. Corneal microperforation is a potentially serious adverse event, but other adverse events, such as striae, whitening and intracorneal haemorrhages are reversible. It should be considered for established corneal vessels, and can be combined with antivascular endothelial growth factors.

Wavefront-optimized excimer laser in situ keratomileusis for myopia and myopic astigmatism: refractive outcomes and corneal densitometry.

PURPOSE: To determine the refractive outcomes of wavefront‐optimized laser in situ keratomileusis (LASIK) treatments, in particular to measure corneal densitometry after LASIK using the densitometry function of the Pentacam Scheimpflug system. SETTING: Division of Ophthalmology and Visual Sciences, University of Nottingham, United Kingdom. DESIGN: Cohort study. METHODS: Changes in postoperative visual acuity, refraction, and contrast sensitivity were evaluated after wavefront‐optimized laser treatment. Corneal densitometry was evaluated with the Scheimpflug system before and after LASIK. RESULTS: One year postoperatively, the uncorrected distance visual acuity was 6/6 or better in 92% of eyes and 6/9 or better in all eyes. Eighty‐six percent of eyes had no change in the corrected distance visual acuity (CDVA); 4% gained 1 or more lines. Wavefront‐optimized LASIK was stable over 1 year postoperatively. Eighty‐nine percent of eyes were within ±0.50 diopter (D) and 100% were within ±1.00 D of the intended correction 1 year postoperatively. Contrast sensitivity showed a nonsignificant improvement (1.55 ± 0.10 [SD] preoperatively to 1.57 ± 0.09 12 months postoperatively) (P > .05). There was a nonsignificant increase in corneal densitometry 1 year postoperatively (from 12.72 ± 2.43 to 13.04 ± 2.58) (P > .05). No correlation was found between corneal densitometry and contrast sensitivity or CDVA. CONCLUSIONS: Wavefront‐optimized LASIK gave excellent refractive and visual outcomes and did not seem to affect corneal densitometry significantly 1 year postoperatively. However, larger studies may show a masked effect on corneal densitometry. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned.

Big bubble deep anterior lamellar keratoplasty: the collagen layer in the wall of the big bubble is unique

In big bubble (BB), deep anterior lamellar keratoplasty intracorneal injection of air separates Descemets membrane (DM) and the pre‐Descemets layer (Duas layer [DL]) to create a type 1 BB. We tested the hypothesis that air injection after excision or ablation of DL will fail to produce a BB.

The morphologic characteristics of corneal nerves in advanced keratoconus as evaluated by acetylcholinesterase technique.

PURPOSE To study the morphologic characteristics of corneal nerves in patients with advanced keratoconus using the acetylcholinesterase technique in corneal whole mounts. DESIGN Prospective, observational case series. METHODS Fourteen corneal buttons from 14 keratoconic patients (9 males and 5 females; mean age, 34.3 years) who had undergone keratoplasty for advanced keratoconus and 6 corneal buttons from 6 normal corneas were included. Whole mounts were stained for acetylcholinesterase and were scanned with a novel digital pathology scanning microscope. RESULTS Seventy-one percent of keratoconic corneas demonstrated central stromal nerve changes, which included thickening, tortuosity, nerve spouting, and overgrowth. The nerve changes ranged from early to extensive and could be separated into 3 different grades. The central stromal nerves were abnormally thicker (18.9 ± 14.7 μm) than in controls (8.11 ± 3.31 μm; P < .001). The thickness of peripheral stromal nerves (12.6 ± 3.1 μm) was similar to that of controls (14.86 ± 5.60 μm; P = .072). Subbasal nerves showed changes in the form of loss of radial orientation and increased tortuosity, especially at the cone apex. At the cone base, a concentric arrangement of subbasal nerves was found in 43% of cases. Localized thickenings of subbasal nerves also were observed at their origin from the bulbous terminations of sub-Bowman nerves. The terminal bulbs, too, were enlarged. The mean diameter of the subbasal nerves in keratoconus (4.11 ± 0.60 μm) did not differ from that of the controls (4.0 ± 0.61 μm; P = .422). CONCLUSIONS This study provides additional histologic evidence of the involvement of corneal nerves in keratoconus and suggests further that they may play a role in the pathophysiologic factors and progression of the disease.

Profile of sight-threatening infectious keratitis: a prospective study.

Purpose:  To prospectively study patients presenting with sight‐threatening corneal ulcers with a view to identify the predisposing factors, causative organisms, clinical signs and treatment outcomes.

Fibrin glue inhibits migration of ocular surface epithelial cells.

PurposeFibrin glue has been used successfully in numerous ophthalmic surgical procedures. Recently, fibrin glue has been used in limbal stem cell transplantation to reduce both operative time and to negate the need for sutures. The aim of this study was to determine the effects of fibrin glue on epithelial cell migration in vitro.MethodsCorneoscleral rims were split to retain the epithelial layer, Bowman’s layer, and anterior stroma. Rims were cut into eight equal-sized pieces and were placed directly on culture plates or affixed with fibrin glue. Rims were maintained in culture for 25 days and epithelial cell growth was monitored. Cells were photographed to measure area or growth and immunofluorescence staining of explants for fibrin was performed.ResultsExplants that were glued demonstrated significantly delayed epithelial cell growth and migration as compared with explants without glue. By day 16, all fibrin glue had dissolved and coincided with onset of cell growth from glued explants. Cell growth commenced between days 3 and 4 for control explants without glue and around days 14–16 for explants with fibrin glue.ConclusionsFibrin glue delays epithelial cell migration by acting as a physical barrier and can potentially interfere with explant-derived limbal epithelial cell migration on to the corneal surface. We propose that glue should be used to attach the conjunctival frill of the limbal explant but care should be taken to ensure that the glue does not wrap around the explant if used to secure the explant as well. Strategic use of glue, to attach the recessed conjunctiva, can be advantageous in delaying conjunctival cell migration and reducing the need for sequential sector conjunctival epitheliectomy.