Histopathological changes after deep anterior lamellar keratoplasty using the ‘big‐bubble technique’

Purpose: During deep anterior lamellar keratoplasty (DALK), endothelium and Descemet’s membrane are separated from the corneal stroma by intrastromal air injection (‘big‐bubble technique’). The aim of our study is to analyse histopathological changes in host corneal tissue caused by air insufflation in patients with keratoconus, their variability in 10 patients and their possible clinical implication. Methods: The excised anterior corneal lamellae of 10 patients with keratoconus having undergone DALK using the ‘big‐bubble technique’ were analysed by light and transmission electron microscopy as well as immunohistochemistry. In addition, intrastromal air accumulations were quantified morphometrically. Results: Intrastromal air was detected in all examined excised lamellae (8% of stromal volume), but with large variability (SD 8.8). It was detected preferentially in the inner layer of the corneal stroma and represented there up to 39% of the stromal volume. In addition, the air was predominantly located at one periphery of the excised lamellae. Intrastromal air bubbles were larger in the inner than in the superficial stromal layer and characterized by round shape and a CD68‐negative collagenous ‘pseudocapsule’. We detected no air‐injection‐induced alterations in Bowman’s layer and epithelium. Conclusion: Our results show that ‘big‐bubble DALK’ causes significant intrastromal air accumulations in the cornea. Pathologists should be conscious of this phenomenon and the high topographic variability. Intrastromal air in the recipient rim may be accompanied by a decrease in mechanical stability and could contribute to postoperative suture loosening.     

Role of corneal elasticity in damping of intraocular pressure

PURPOSE: To determine corneal elasticity and its contribution in damping acute intraocular pressure spikes. METHODS: Twenty corneas with intact scleral rims were excised from human donor eyes and mounted on an artificial anterior chamber. A watertight seal was obtained with 17 corneas. Saline was infused into the chamber at a rate of 10 mL/h, and subsequent changes in pressure were measured to generate a pressure-volume relationship. Real-time anterior segment OCT was used to measure the change in radius of curvature and corneal thickness in nine eyes. RESULTS: The pressure-versus-volume curves of all corneal-scleral buttons were concave-up asymptotes, demonstrating elasticity. The range of the slope was 0.34 to 1.6 +/- 0.29 mm Hg/microL. The mean change in the radius of curvature in the nine eyes that were visualized by optical coherence tomography (OCT) was 247 +/- 106 microm (range, 168-412 microm). The OCT image was centered on the epithelial surface. In two eyes, the entire cornea was visible by OCT throughout the course of the experiment, and corneal thickness was measured and found to decrease by 116 +/- 4 microm. CONCLUSIONS: Human eye bank corneas demonstrate elasticity ex vivo, with expansion and thinning in response to increases in anterior chamber pressure. These elastic properties may serve as a buffering mechanism for microvolumetric changes in the eye, thus protecting the eye from intraocular pressure surges in vivo.     

Predictability of donor lamellar graft diameter and thickness in an artificial anterior chamber system

PURPOSE: To identify factors affecting the predictability and report results of donor lamellar graft diameter and thickness in an artificial anterior chamber obtained with a microkeratome. METHODS: Lamellar lenticules were obtained from 25 human corneoscleral rims mounted in an artificial anterior chamber. Lenticules measuring 9 mm were attempted at two thicknesses (250 microm and 350 microm heads). Intrachamber pressure of 65 mm Hg was confirmed with Barraquer tonometry. Keratometry, pachymetry, limbal white-to-white, and qualitative mires with the diameter applanation lens were evaluated as possible factors predictive of lenticule diameter and thickness. Diameters and thicknesses were measured with calipers and pachymetry, respectively.RESULTS Ninety-two percent (23/25 lenticules; 14/15 in 250 microm, 9/10 in 350 microm) were +/- 0.25 mm of the intended diameter and 76% (19/25 lenticules; 12/15 in 250 microm, 7/10 in 350 microm) were within +/- 100 microm of the intended thickness. Ovoid applanation mires with the diameter applanation lens represented tissue herniation within the artificial anterior chamber and led to ovoid lenticules (2/25). CONCLUSIONS: Lenticules of 9 mm +/-0.25mm in diameter were highly reproducible with proper corneoscleral rim seating. Intrachamber pressure confirmed with Barraquer tonometry is important in obtaining lenticules of consistent diameter and adequate thickness. Ovoid applanation mires may herald improper corneoscleral rim seating and result in a similarly shaped lenticule. A 2 mm or greater corneoscleral rim is recommended to prevent tissue herniation within the artificial anterior chamber used in this study.     

Donor tissue preparation for Descemet membrane endothelial keratoplasty

PURPOSE: To evaluate a technique for preparing a donor Descemet membrane carrying autologous endothelium for transplantation in Descemet membrane endothelial keratoplasty (DMEK). SETTING: Netherlands Institute for Innovative Ocular Surgery, Rotterdam, The Netherlands. METHODS: A 9.5 mm diameter DM carrying autologous endothelium was stripped from 10 corneoscleral rims that had been organ cultured for 1 week. The endothelial cell density (ECD) was evaluated with light microscopy before and immediately after DM was stripped and during 4 additional weeks of organ culture. RESULTS: The mean ECD was 2701 cells/mm(2) +/- 302 (SD) before and 2719 +/- 322 cells/mm(2) immediately after DM was stripped and declined from 2604 +/- 352 cells/mm(2) after 1 week to 2190 +/- 768 cells/mm(2) after an additional 4 weeks of organ culture (n = 10). Typical "endothelial streaks," ie, linear cellular disruptions observed immediately after DM was stripped, showed complete regeneration after the second culture period. CONCLUSIONS: Descemet grafts for transplantation in DMEK procedures can be surgically prepared from organ-cultured corneal rims and stored for an additional 3 weeks with acceptable endothelial cell loss. Because the donor tissue can be dissected directly from organ-cultured corneoscleral rims, donor preparation for DMEK can be readily accessible to most corneal surgeons.     

Intradescemetic air bubble trapping during deep anterior lamellar keratoplasty

We describe a case of a 52-year-old man in whom the appearance of an air bubble developed, trapped within the Descemet membrane (DM), that occurred during a planned deep anterior lamellar keratoplasty using the "big bubble" technique. This situation can occur because Descemet membrane's anatomic structure can be opened by the gas dissection; this complication may result in unanticipated results during and after this type of surgery. Surgeons should be aware of this specific risk, so they will recognize it when it occurs. Optical coherence tomography (OCT) imaging and surgical management are presented.     

Corneal optical coherence tomography before and after phototherapeutic keratectomy for recurrent epithelial erosions(2)

PURPOSE: To study the representation of corneal structures with optical coherence tomography (OCT) before and after excimer laser phototherapeutic keratectomy (PTK) for recurrent epithelial erosions. SETTING: Departments of Ophthalmology, Vivantes Klinikum Neuk?lln, Berlin, and Medizinische Universit?t, Lübeck, Germany. METHODS: This prospective study comprised 15 eyes of 14 patients with recurrent epithelial erosions. The central corneal and epithelial thickness as well as the wound-healing response in the anterior corneal stroma were assessed with slitlamp-adapted OCT before and after PTK. RESULTS: After PTK, the symptoms improved in all patients without loss of best corrected, glare, or low-contrast visual acuity. The mean central corneal OCT thickness was 540 microm +/-28 (SD) preoperatively, 492 +/- 36 microm immediately after epithelial debridement and PTK, and 519 +/- 25 microm after 7 weeks (P <.01). The mean central epithelial OCT thickness changed from 70 +/- 13 microm preoperatively to 60 +/- 7 microm after 7 weeks (P >.01). Changes in the light-scattering properties in the anterior subepithelial stroma revealed a hyperreflective area with a mean thickness of 46 +/- 13 microm after 7 weeks. CONCLUSIONS: Using noncontact corneal OCT, corneal and epithelial thickness changes and the wound-healing response in the anterior corneal stroma could be evaluated after PTK in patients with recurrent epithelial erosions.     

Descemet membrane endothelial keratoplasty (DMEK)

PURPOSE: To describe Descemet membrane endothelial keratoplasty (DMEK) with organ cultured Descemet membrane (DM) in a human cadaver eye model and a patient with Fuchs endothelial dystrophy. METHODS: In 10 human cadaver eyes and 1 patient eye, a 3.5-mm clear corneal tunnel incision was made. The anterior chamber was filled with air, and the DM was stripped off from the posterior stroma. From organ-cultured donor corneo-scleral rims, 9.0-mm-diameter "DM rolls" were harvested. Each donor DM roll was inserted into a recipient anterior chamber, positioned onto the posterior stroma, and kept in position by completely filling the anterior chamber with air for 30 minutes. RESULTS: In all recipient eyes, the donor DM maintained its position after a 30-minute air-fill of the anterior chamber followed by an air-liquid exchange. In the patient's eye, 1 week after transplantation, best-corrected visual acuity was 1.0 (20/20) with the patient's preoperative refraction, and the endothelial cell density averaged 2350 cells/mm. CONCLUSION: DMEK may provide quick visual rehabilitation in the treatment of corneal endothelial disorders by transplantation of an organ-cultured DM transplanted through a clear corneal tunnel incision. DMEK may be a highly accessible procedure to corneal surgeons, because donor DM sheets can be prepared from preserved corneo-scleral rims.     

眼前节OCT在圆锥角膜急性角膜水肿中的运用

目的：探讨圆锥角膜急性水肿的眼前节OCT影像学特征,分析角膜水肿发生发展的原因。方法：收集8例急性角膜水肿的圆锥角膜患者,行常规眼部检查及眼前节OCT检查。结果：角膜基质层内形成一裂隙与前房相沟通。角膜基质层的厚度在发生裂隙的部位十分菲薄,甚至穿孔,发生虹膜组织嵌顿。结论：角膜基质层裂隙的形成可能是导致急性角膜水肿的一个重要原因,裂隙还可能导致持续的水肿及后弹力层的延迟愈合,严重者甚至造成角膜穿孔。     

Treatment of Inferior Descemet Membrane Detachment Secondary to Cataract Surgery with Air Injection and Supine Head Position

Purpose: To describe a case of a patient with inferior Descemet membrane detachment that resolved after injection of small air bubble and supine positioning.

Methods: A patient presented two weeks after cataract surgery with inferior persistent corneal edema. A Descemet membrane detachment involving the inferior cornea was revealed. Injection of small air bubble was performed and the patient was advised to stay in a supine position for the next two hours and then as much as reasonably possible to allow the air bubble to press the Descemet to the posterior corneal stroma.

Results: Five days after injection, the Descemet membrane was reattached to the corneal stroma and the cornea became clear without any evidence of edema. One month post-air injection the cornea remained clear and the Descement membrane attached.

Conclusions: Air injection with supine position was efficient for the resolution of inferior partial Descemet detachment after cataract surgery. The edema resolved without any further intervention.     

Preliminary clinical results of Descemet membrane endothelial keratoplasty

PURPOSE: To describe the preliminary clinical results of selective transplantation of organ cultured, donor Descemet membrane (DM) carrying autologous corneal endothelium through a 3.5-mm incision, tentatively named Descemet membrane endothelial keratoplasty (DMEK), for the management of corneal endothelial disorders. DESIGN: Nonrandomized clinical study. METHODS: In 10 patients with Fuchs endothelial dystrophy or pseudophakic bullous keratopathy, DMEK was performed. A 3.5-mm clear corneal tunnel incision was made, the anterior chamber was filled with air, and DM was stripped off from the posterior stroma. A 9.0-mm diameter DM roll was harvested from an organ cultured donor corneo-scleral rim, and inserted into a recipient anterior chamber. The donor tissue was gently unfolded, positioned onto the posterior stroma, and secured by completely filling the anterior chamber with air for 30 minutes. RESULTS: At one month, six eyes had a best-corrected visual acuity of 0.5 (20/40) or better, and three eyes reached 1.0 (20/20). At six months, the endothelial cell density averaged 2030 (+/-373) cells/mm(2) (n = 7). Three eyes showed a complete detachment of the donor tissue in the early postoperative course that was managed by removal of the transplant and a secondary Descemet stripping endothelial keratoplasty procedure. CONCLUSION: DMEK may have potential to become the most preferable technique to manage corneal endothelial disorders, because it provides quick and nearly complete visual rehabilitation. Because the donor tissue required can be prepared from organ cultured corneo-scleral rims, the procedure may be readily accessible to most corneal surgeons.     

Descemet membrane detachment caused by hydrogen peroxide injury

OBJECTIVE: To describe a patient who developed a Descemet membrane detachment after hydrogen peroxide injury with successful reattachment by intracameral injection of sulfur hexafluoride gas. METHODS: Case report. RESULTS: The right eye of a 40-year-old man was exposed to 35% hydrogen peroxide. This resulted in a central corneal epithelial defect, corneal edema, a localized detachment of Descemet membrane, and a gas bubble between the posterior corneal stroma and Descemet membrane. The Descemet membrane detachment persisted after reabsorption of the gas bubble. Successful reattachment of Descemet membrane was achieved with injection of 0.15 mL of 20% sulfur hexafluoride gas into the anterior chamber. CONCLUSION: Hydrogen peroxide ocular injury may cause Descemet membrane detachment, and successful reattachment may be achieved with intracameral injection of 20% sulfur hexafluoride gas.     

Corneal imaging with anterior segment optical coherence tomography for lamellar keratoplasty procedures

PURPOSE: To assess and describe the uses of anterior segment optical coherence tomography (OCT) in the evaluation of the cornea before and after lamellar corneal transplantation procedures. DESIGN: Prospective, noncomparative, observational case series. METHODS: Seven eyes of seven patients undergoing anterior and posterior lamellar corneal transplantation procedures at the Singapore National Eye Centre were included in the study. High-resolution anterior segment OCT scans of the cornea and anterior segment were performed both before and after lamellar transplantation procedures on the cornea with the Visante anterior segment OCT system (Visante OCT; Carl Zeiss Meditec, Inc, Dublin, California, USA), and the imaging findings were correlated with the clinical picture. Measurements of lamella thickness were performed with the software provided. RESULTS: Anterior segment OCT images were able to provide valuable information on donor apposition, Descemet membrane detachment after deep anterior lamellar keratoplasty (DALK), posterior lamellar dislocation, primary graft failure, and anterior chamber crowding with consequent chamber angle encroachment and pupillary block after Descemet stripping automated endothelial keratoplasty (DSAEK). CONCLUSIONS: Anterior segment OCT is a valuable imaging tool for assessing the feasibility of lamellar transplantation surgery in the diseased cornea and in the management of surgical complications after such procedures.     

Imaging of the anterior eye chamber with optical coherence tomography

BACKGROUND: Optical coherence tomography (OCT) represents a high-resolution diagnostic method which can be used to precisely image the anterior eye segment. Further developments in scanning technology and data evaluation allowed to visualize the entire anterior eye segment in one image, and the purpose of this study was to clinically evaluate this new system. PATIENTS AND METHODS: The studied OCT system was adapted to a slit-lamp and allowed us to image the anterior segment with an axial resolution of 10 microm at a scanning rate of 200 Hz with a depth of 7 mm and a maximal width of 15 mm. In selected cases the clinical value of anterior segment OCT was assessed. The reproducibility and level of agreement of anterior chamber depth measurements were assessed during the preoperative examination in 49 cataract surgery patients and compared to ultrasound (US) biometry (10 MHz). RESULTS: The studied anterior segment OCT allowed the cross-sectional imaging of the entire anterior eye segment. Changes of the anterior chamber before and after cataract surgery or surgical iridectomy were visualised. Furthermore, the findings of the anterior chamber after implantation of an iris-fixated intraocular lens (IOL) and an iris prosthetic system could be assessed. The reproducibility of the anterior chamber depth measurement was +/- 22 microm (OCT) and +/- 76 microm (US). The mean difference between optical and acoustic values was 1 microm (0.03 % p = 0.921) and the limits of agreement (95 % confidence interval) were 260 microm (8.58 %). CONCLUSIONS: The anterior segment OCT proved to be a helpful diagnostic method. The cross-sectional visualisation of the entire anterior chamber allowed us to assess important values for the implantation of iris-fixated IOL and other changes after surgical procedures. The resolution and reproducibility were higher than for conventional ultrasound biometry.     

Visante<Superscript>®</Superscript> anterior segment OCT in a patient with gas bubbles in the anterior chamber after femtosecond laser corneal flap formation

A patient with anterior chamber gas bubbles after LASIK flap formation with femtosecond laser is presented. A 33-year-old male patient had LASIK for myopia with corneal flap formation with IntraLase FS30 femtosecond laser. In the right eye, air bubbles were observed in anterior chamber after successful flap formation. Laser correction was completed successfully, by Wavelight Allegretto Wave Eye-Q excimer laser, without eye-tracker. Visante anterior segment optical coherence tomography imaging displayed that the pocket extended to limbal area, with stromal bed thickness of >600 microm at that area. We propose as possible causes of the air bubbles scattering of femtosecond laser beam producing direct photodissociation of aqueous humor, or direct cavitation effect in aqueous humor due to rapid pressure changes in corneal lamellar interface during the femtosecond laser procedure. Other causes such as migration of intrastromal bubbles through peripheral corneal stroma and trabecular meshwork, or through posterior stroma and endothelium, seem to be unlikely.     

Permanencia de la membrana de Descemet y del endotelio receptor tras queratoplastia penetrante. A propósito de un caso clínico

A case is presented of a retained Descemet's membrane after penetrating keratoplasty, highlighting the importance of the anterior segment optical coherence tomography (OCT) in the diagnosis and treatment planning of keratoplasty complications.A review of literature is also presented.An 88 year-old man underwent penetrating keratoplasty for bullous keratopathy.A retained host Descemet's membrane was detected. The retained membrane went unnoticed until the visual acuity decreased. The ophthalmological examination showed the presence of an opalescent membrane located below the endothelium, and was identified as the Descemet membrane of the receptor. Nd:YAG laser membranotomy was performed after the diagnosis.To conclude, it is noted that the inadvertent retention of the host Descemet membrane is a rare complication in penetrating keratoplasty. The anterior segment OCT was used to determine the diagnosis, and Nd:YAG laser membranotomy is an indicated treatment in these cases.     

Variation in central corneal thickness during open- or closed-eye riboflavin instillation for corneal collagen cross-linking

OBJECTIVE:To assess the effect of having an open or closed eye on the variation in central corneal thickness during riboflavin instillation for corneal collagen cross-linking (CXL).;METHODS:Thirty eyes of 15 New Zealand White rabbits underwent an in vivo anterior segment optical coherence tomography (OCT) examination at 0, 10, 20, and 30 min after riboflavin instillation on the de-epithelialized corneal surface. Each eye of every rabbit was randomly placed into one of two different treatment groups (open-eye or closed-eye) during the instillation; the examinations were performed one after the other. After instillation for 30 min, the changes in the corneal stroma and anterior chamber were observed by slit lamp.;RESULTS:A significant decrease in the central corneal thickness (CCT) was demonstrated during riboflavin instillation; the variations were smaller in the measurements performed with the eye closed than with the eye open (81.36 +/- 15.13 microm and 129.20 +/- 12.05 microm respectively). Both methods turned the corneal stroma and anterior chamber yellow.;CONCLUSIONS:Keeping the eye closed during riboflavin instillation reduced the decrease in the CCT. The same yellow change in the corneal stroma and anterior chamber occurred, but the exposure time of the ocular surface was shorter. Therefore, keeping the eye closed was a more effective and safer method than keeping the eye open.     

'Expanding bubble' modification of 'big-bubble' technique for performing maximum-depth anterior lamellar keratoplasty

Purpose

To describe a new technique for performing maximum-depth anterior lamellar keratoplasty.

Methods

This was a case series study using a novel method. We introduce and describe a new sign (sunny-side up sign) that reveals the presence and extent of the air bubble at the Descemet membrane (DM)–stroma interface. We also report a novel technique to expand the bubble by injecting viscoelastic material into the bubble cavity and to excise the stromal tissues within the trephination area almost completely. The follow-up period ranged from 12 to 16 months. In all patients we recorded the best spectacle-corrected visual acuity, keratometry, and endothelial cell count preoperatively and postoperatively and the air bubble diameter using the sunny-side up sign.

Results

In eight of nine patients, a big bubble formed. The size of the air bubble ranged from 2 to 7 mm. All the bubbles were expanded to 8 mm and the bare DM throughout the trephination area was obtained in all cases. The postoperative mean keratometric readings were reduced compared with the preoperative mean keratometric readings. The BSCVA was increased postoperatively compared with the preoperative acuity. The difference between the preoperative and postoperative endothelial cell counts was not statistically significant.

Conclusions

The early outcomes in our series using the expanding bubble technique suggest that it is safe and easy in performing maximum-depth anterior lamellar keratoplasty.     

Corneal lenticule harvest using a microkeratome and an artificial anterior chamber system at high intrachamber pressure

PURPOSE: To evaluate the safety and accuracy of a manual microkeratome and an artificial anterior chamber used at high intrachamber pressure to harvest corneal lenticules for lamellar keratoplasty. SETTING: Department of Ophthalmology, University of California, Irvine, California, USA. METHODS: Forty-seven human eye-bank corneoscleral rims were mounted on an artificial anterior chamber. A manual microkeratome was used to perform lamellar keratectomy at a mean intrachamber pressure of 95.8 mm hg +/- 4.8 (sd). Two thicknesses (300 microm and 360 microm microkeratome heads) and diameters (8.0 mm and 9.0 mm) were attempted, and the resultant lenticules were analyzed by pachymetry and digital photography. RESULTS: In the 9.0 mm/360 microm group, corneal perforation occurred in 12 of 17 lenticules (71.2%). Except for this group, 24 of 30 corneas (80.0%) showed a less than 0.5 mm deviation from the expected diameter. Neither the horizontal nor the vertical diameter differences were statistically significant (P >.05). The difference between the horizontal and vertical diameters was within +/-0.2 mm in 23 corneas (76.7%). Three (10.0%) corneal beds contained a slightly uneven keratectomy margin. CONCLUSIONS: This system provided accurate and smooth lenticules for lamellar keratoplasty. The precision and accuracy of the obtained corneal lenticules were better than those in previous reports. However, the 9.0 mm diameter/360 microm thickness head with high intrachamber pressure should not be applied in the clinical setting without further testing. In this laboratory study, a minimal corneal thickness of 588 microm was required to avoid perforation.     

Descemet's membrane perforation during deep anterior lamellar keratoplasty: prognosis

PURPOSE: To evaluate the functional and endothelial prognosis after Descemet's membrane perforation during deep anterior lamellar keratoplasty (DALK). SETTING: Private practice, Siena, Italy. METHODS: A retrospective study evaluated a series of 35 eyes that had DALK using the big-bubble technique. RESULTS: Intraoperative perforation occurred in 8 eyes (23%), in 5 eyes during manual deep dissection and in 1 eye each during trephination, as the air needle was introduced in the stroma, and as the big bubble was punctured. In all 8 eyes, DALK could be completed. In 1 case, pupillary block was caused by air left in the anterior chamber, resulting in permanent mydriasis and anterior subcapsular opacity. In another case, a double anterior chamber persisted and penetrating keratoplasty was later required. In the other 6 cases, the postoperative course was uneventful. The mean postoperative best spectacle-corrected visual acuity was 0.8 +/- 0.13 (SD) and the mean postoperative refractive astigmatism, 2.09 +/- 0.98 diopters. The mean endothelial cell loss, evaluated in 7 eyes, was 12% +/- 11% at 1 month (P<.05) and 14% +/- 12% at 12 months. The mean cell loss was 25% +/- 2.7% in eyes in which intraoperative reformation of the anterior chamber with air was required and 6% +/- 7.5% in eyes in which it was not (P< .05). CONCLUSIONS: Despite 2 complicated cases, intraoperative perforation during DALK had a good final functional prognosis. However, eyes in which the perforation required reformation of the anterior chamber had a mean endothelial cell loss greater than 20%. When air is left in the anterior chamber, close monitoring is required to avoid pupillary block.     

Use of a "small-bubble technique" to increase the success of Anwar's "big-bubble technique" for deep lamellar keratoplasty with complete baring of Descemet's membrane

PURPOSE: To describe a quick and simple "small-bubble" technique to immediately determine the success of attaining complete Descemet's membrane (DM) separation from corneal stroma through Anwar's "big-bubble" technique of deep anterior lamellar keratoplasty (DALK) for complete stromal removal. METHODS: A partial trephination was followed by a lamellar dissection of the anterior stroma. Deep stromal air injection was then attempted to achieve the big bubble to help separate the stroma from the DM. To confirm that a big bubble had been achieved, a small air bubble was injected into the anterior chamber (AC) through a limbal paracentesis. If the small bubble is then seen at the corneal periphery, it confirms that the big-bubble separation of DM was successful because the convex nature of the bubble will cause it to protrude posteriorly, forcing the small AC bubble to the periphery. If the small AC bubble is not seen in the corneal periphery, this means that it is present in the centre, beneath the opaque corneal stroma, and therefore the big bubble has not been achieved. RESULTS: We used the small-bubble technique to confirm the presence of the big bubble in three (one keratoconus, one interstitial keratitis and one dense corneal scar) out of 41 patients who underwent DALK. The small-bubble technique confirmed that the big bubble was achieved in the eye of all three patients. Complete stromal removal with baring of the DM was achieved, and postoperatively all three eyes achieved best corrected vision of 6/6. CONCLUSION: The small-bubble technique can be a useful surgical tool for corneal surgeons attempting lamellar keratoplasty using the big-bubble technique. It helps in confirming the separation of DM from the deep stroma, which is important in achieving total stromal replacement. It will help to make the transition to lamellar keratoplasty smoother, enhance corneal graft success and improve visual outcomes in patients.