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.

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.