Vitreous cavity length in keratoconus: implications for keratoplasty.

PurposeTo compare axial length (AL) with vitreous cavity length (VCL) in patients with keratoconus and to ascertain whether graft size can be tailored to reduce myopic refractive error in patients with keratoconus undergoing penetrating keratoplasty (PK).Patients and methodsThe AL and VCL were measured prospectively in patients with keratoconus not undergoing PK (Group 1) and in normal phakic, emmetropic individuals (Group 2). A retrospective analysis of these measurements in patients with keratoconus who had undergone PK (Group 3) was also performed. The postoperative spherical equivalent (SE) was then correlated to size of donor buttons.ResultsKeratoconus patients tended to have a longer mean VCL than emmetropic normal individuals. The mean VCL of these patients (Group 1) was 16.49 mm±SD 1.13 compared to the mean VCL of 15.94 mm±SD 0.56 in normals (Group 2, P<0.0001). Patients with keratoconus who had an undersized graft showed reduced myopic refractive error compared to those with same size or oversized grafts.ConclusionVCL measurement is more accurate than AL measurement in deciding upon graft-host size disparity for corneal graft in patients with keratoconus. In patients with increased VCL, undersizing the donor button helps in reducing postoperative myopia. We recommend VCL measurement as part of the routine workup in all keratoconus patients undergoing corneal transplants.

Fibrin glue as agent for sealing corneal and conjunctival wound leaks.

PurposeTo describe a novel use of fibrin glue in managing leaking blebs and leaking wounds following trauma or surgery.MethodsInterventional case series.ResultsWe report eight patients, including three where intra-operative or immediate post-penetrating keratoplasty recalcitrant leaks from the graft-host junction and/or openings created by the needle pass, were noted. All three had thin recipient beds in the sector of leak. This was managed by intra-cameral injection of fibrin glue in the affected quadrant. This stopped the leak and allowed the defect to heal. One patient of Descemets-stripping-endothelial-keratoplasty had leak from the surgical wound, which was also sealed with fibrin glue. Two patients with leaking glaucoma-surgery-related blebs were treated with intra-bleb injection of fibrin glue to stop the leak. One patient with a penetrating corneal injury with a metal wire had a brisk leak upon removal of the wire. This was sealed with fibrin glue. Another patient of chemical burn with spontaneous leaks was managed by glue injection in the perforations. Transient rise of intraocular pressure in one patient with a leaking bleb was the only adverse event recorded.ConclusionThis novel adaptation of the application of fibrin glue can help to deal with persistent intra-operative, post-operative and traumatic aqueous and air leaks.

Air pressure changes in the creation and bursting of the type-1 big bubble in deep anterior lamellar keratoplasty: an ex vivo study.

PurposeTo measure the pressure and volume of air required to create a big bubble (BB) in simulated deep anterior lamellar keratoplasty (DALK) in donor eyes and ascertain the bursting pressure of the BB.Patients and methodsTwenty-two human sclera-corneal discs were used. Air was injected into the corneal stroma to create a BB and the pressure measured by means of a pressure converter attached to the system via a side port. A special clamp was designed to prevent air leak from the periphery of the discs. The pressure at which air emerged in the corneal tissue; the bursting pressure measured after advancing the needle into the bubble cavity and injecting more air; the volume of air required to create a BB and the volume of the BB were ascertained.ResultsType-1 BB were achieved in 19 and type-2 BB in 3 eyes. The maximum pressure reached to create a BB was 96.25+/- 21.61 kpa; the mean type-1 intrabubble pressure was 10.16 +/- 3.65 kpa. The mean bursting pressure of a type-1 BB was 66.65 +/- 18.65 kpa, while that of a type-2 BB was 14.77 +/- 2.44 kpa. The volume of air required to create a type-1 BB was 0.54 ml and the volume of a type-1 BB was consistently 0.1 ml.ConclusionsDua's layer baring DALK can withstand high intraoperative pressures compared to Descemet's membrane baring DALK. The study suggests that it could be safe to undertake procedures such as DALK-triple with a type-1 BB but not with a type-2 BB.

Pre-Descemets endothelial keratoplasty: the PDEK clamp for successful PDEK.

PurposeTo design and produce a clamp that enables good handling of donor sclera-corneal disks, allows air to be injected in the corneal stroma and consistently provides pre-Descemets endothelial keratoplasty (PDEK) tissue by creation of a type-1 big bubble (BB) avoiding a type-2BB by shutting the fenestrations in the periphery of the pre-Descemets layer and preventing escape of air.Patients and methodsA clamp with spring loaded handles attached to two rings of 9 mm diameter and 1 mm width with a side port for insertion of a needle for air injection was designed and produced. The clamp was tested in 20 human donor sclera-corneal disks and refined over three prototypes. The final design was used for PDEK in 8 patients.ResultsThe clamp was able to prevent any escape of air or the formation of a type-2BB. By preventing air leak, it provided better control over the volume of air injected allowing for consistent formation of a type-1BB, which could be expanded to its full diameter by advancing the tip of the needle into the bubble cavity. Centration of tissue in the clamp was important. The clamp was used successfully to obtain PDEK tissue from 8 donor sclara-corneal disks for transplant in three eyes with pseudophakic bullous keratopathy and five eyes with pseudophakia and Fuchs' endothelial dystrophy.ConclusionThe PDEK clamp is a simple and useful instrument that will give surgeons the confidence of consistently obtaining PDEK tissue with ease and without the risk of separating the Descemets membrane in a type-2BB.

Deep anterior lamellar keratoplasty--triple procedure: a useful clinical application of the pre-Descemet's layer (Dua's layer).

PURPOSE: To describe a technique which exploits the transparency and toughness of the pre-Descemets layer (Dua's layer) to safely perform deep anterior lamellar keratoplasty (DALK) and phacoemulsification at the same time. METHODS: Three DALK procedures combined with phacoemulsification were performed by the same surgeon using the big-bubble (BB) technique at the Research Institute of Ophthalmology, Cairo, Egypt. In two cases a type-1 BB, baring Dua's layer, was achieved and in one case a type-2 BB, baring the Descemet's membrane (DM), was achieved. The surgeries were video recorded and photo slit-lamp images were taken in the follow-up visits. RESULTS: DALK with phacoemulsification and lens implant was carried out in both patients where a type-1 BB was achieved. At a follow up of 18 months (first case) and 6 months (second case), the best corrected vision was 6/12 for each. In the case where a type-2 BB was achieved, the DM ruptured during injection of viscoelastic prior to capsulorhexis. The procedure was converted to a penetrating keratoplasty without phacoemulsification. CONCLUSION: When a type-1 BB is achieved simultaneous DALK and phacoemulsification can be safely accomplished. Dua's layer allows a clear view for performing phacoemulsification with the added benefit of its toughness, which can maintain a stable anterior chamber for cataract surgery. This should not be attempted when a type-2 BB is achieved.

Intra-lesional 5 fluorouracil for the management of recurrent pterygium.

AIM: Recurrence is the most common complication arising from pterygium surgery. The aim of this study was to investigate the effectiveness of 5 fluorouracil (5FU) in halting the recurrence of pterygium after surgical excision. METHODS: A retrospective review of patients treated for pterygium recurrence was carried out. Patients with recurrent (secondary) pterygium were treated with multiple weekly intra-lesional injections of 0.1-0.2 ml (2.5-5 mg) 5FU post-operatively depending on the size of the recurrence. The treatment was started within 1 month from the date of recurrence. The time from surgery to start of recurrence, previous treatment modalities, and number of recurrences were documented. The number of injections required to induce arrest of progression and/or regression of vascularity and fleshiness of the pterygium and any complications related to 5FU treatment were examined. RESULTS: Fifteen eyes from 14 patients with recurrent pterygium treated with intra-lesional 5FU injections were analysed. Three of the 15 eyes had undergone a secondary excision and 12 had undergone a primary excision. In all, 93.3% of patients showed regression of the fibrovascular tissue (thickness and vascularity) and arrest of progression following a dose of 0.1-0.2 ml (2.5-5 mg) 5FU. Twelve eyes required three injections or fewer, whereas one patient required eight injections. This beneficial effect was maintained over an average follow-up period of 17 months. No complications from 5FU were observed. CONCLUSION: The use of weekly intra-lesional 5FU injections for the treatment of recurrent pterygium is safe and effective in limiting the progression and inducing the regression of recurrent pterygium. The number of injections can be tailored according to clinical need.

Rapid suture management of post-keratoplasty astigmatism.

AIM: Post-keratoplasty astigmatism is managed by topography-guided suture removal. This can take several weeks until satisfactory reduction in astigmatism is achieved. This study aimed to assess whether topography performed 30-40 min after the removal of the first pair of sutures would predict the next set of sutures requiring removal. METHODS: A prospective study of 20 consecutive penetrating keratoplasty patients was carried out. Topography guided suture removal in the steep meridian was carried out. Topography was repeated after 30-40 min and 4-6 weeks later. The tight sutures requiring removal were identified for each occasion and compared. The difference was considered insignificant if the axes of sutures requiring removal was <22.5 degrees. Paired t-test and chi (2) were performed for statistical analysis. RESULTS: In 85% of individuals, the 30-40 min topography gave an accurate indication of the next pair of sutures requiring removal. The difference in mean astigmatism at 30-40 min post suture removal (4.37+/-2.08 D) and at 4-6 weeks (4.24+1.97 D) was not significant (P=0.150). However, the difference between vector-corrected change of topographic astigmatism at 30-40 min after suture removal and at 4-6 weeks (1.72 D) was significant (P<0.001). Improved best-corrected visual acuity was seen in 50% of patients. CONCLUSION: This study showed that corneal topography performed 30-40 min after suture removal can identify the next set of sutures requiring removal. This can be used as a guide to remove more sutures at the same visit, thereby expediting post-keratoplasty visual rehabilitation and reducing the number of follow-up visits.

Amniotic membrane in ophthalmology: indications and limitations.

The amniotic membrane remains a useful tool in the treatment of several ophthalmic conditions, especially those related to the ocular surface. However, the 'success' reported in individual case reports and case series is not substantiated in the few published randomised controlled trials. More often than not, it is not as good as existing alternative options and, at best, is as good but with probably an increased cost. The variable outcomes could be related to inter and intra donor variations in the membrane and the depletion or alterations in its constituents subsequent to processing and storage. The membrane thus is a fairly 'non-standardised product' making comparisons of different applications and indications difficult. The potential for 'epidemic' infections, such as HIV, hepatitis B and C, is a serious issue as, in many parts of the world, fresh unquarantined membrane, at times with no tests for the above infectious agents, is being used. The exact mechanism of action of the membrane is not known but the consensus is that it acts as a substrate or scaffold for host cells to populate and thus facilitate healing and repair. The development of a standard 'synthetic membrane' using collagen or polymer matrices impregnated with putative beneficial ingredients, such as growth factors and antimicrobials, is being considered and may prove to be a step in the right direction.