A pinboard by
Andrew Ross

PhD student , University of Nottingham


Corneal transplants are commonly used to replace diseased corneal tissue with healthy ones. There are two main types of cornea transplants: full thickness cornea transplant and partial (lamellar) one.

In full thickness grafts the whole cornea is replaced with a new one. The new cornea is fixed in place with multiple sutures. The main problem with this procedure is the high rate of rejection. In partial transplants only the diseased layers of the cornea are replaced. This allows rapid rehabilitation of vision and carries minimal risk of rejection. However there are some technical difficulties which sometimes hinder the success of partial grafts surgeries.

My research area focuses on understanding how the partial grafts work at the cellular level, the reason as to why they are not always successful and strategies to improve the tissue harvesting conditions to obtain better results.

This particular paper, I am presenting at Lisbon, is the first study to investigate the changes made by a certain surgical technique at the histological/cellular level. The results observed in our study were novel and not consistent with the common unstudied belief. This study can enable further improvement of the surgical techniques for partial grafts.


Salvaging deep anterior lamellar keratoplasty with microbubble incision technique in failed "big bubble" cases: an update study.

Abstract: To report the achievement rate of bare Descemet membrane (DM) dissection with the help of microbubble incision technique in eyes with failed big bubble formation and to investigate the mechanism of the microbubble rescue technique through ex vivo imaging of human cadaver corneas.This retrospective clinical study included 80 eyes of 80 patients that underwent deep anterior lamellar keratoplasty (DALK). In 22/80 (27.5%) cases, big bubble dissection failed. After puncturing the microbubbles, viscodissection helped to achieve separation of DM from the remaining stroma. In addition, an ex vivo study with human cadaver cornea specimens, gross photography, and anterior segment optical coherence tomography imaging was accomplished ex vivo to explore the mechanism of this method.Microbubble dissection technique led to successful DALK in 19 of 22 cases of failed big bubble. Microperforation occurred in 3 eyes. Deep anterior lamellar keratoplasty was completed without any complications in 2 out of the 3 eyes with microperforation. In 1 eye, conversion to penetrating keratoplasty was required. Microbubble-guided viscodissection achieved 95.4% (21/22) success in exposing bare DM in failed big-bubble cases of DALK. Anterior segment optical coherence tomography imaging results of cadaver eyes showed where these microbubbles were concentrated and their related size.Microbubble-guided DALK should be considered an effective rescue technique in achieving bare DM in eyes with failed big bubble. Our ex vivo experiment illustrated the possible alterations in cornea anatomy during this technique.

Pub.: 18 Jun '16, Pinned: 31 Aug '17

Visual outcomes of successful versus failed big-bubble deep anterior lamellar keratoplasty for keratoconus

Abstract: Mohammad Ali Javadi, Hossein Mohammad-Rabei, Sepehr Feizi, Seyed-Hashem Daryabari Journal of Ophthalmic and Vision Research 2016 11(1):32-36 Purpose: To compare the visual outcomes of deep anterior lamellar keratoplasty (DALK) for keratoconus with and without successful big-bubble formation. Methods: In this retrospective comparative study, a total of 289 consecutive eyes from 257 patients underwent DALK using the big-bubble technique. In cases where the big bubble could not be accomplished, manual stromal dissection down to Descemeton membrane (DM) was performed using a crescent knife. Visual acuity and refractive outcomes were compared between the bare DM group (Group 1) and manual dissection group (Group 2). Results: A bare DM was successfully achieved in 229 (79.2%) eyes and manual dissection was performed in 60 (20.8%) eyes. The study groups were comparable in terms of age (P = 0.79), preoperative best-spectacle corrected visual acuity (BSCVA) (P = 0.15), and follow-up duration (P = 0.73). Postoperative BSCVA was significantly better in Group 1 than in Group 2 throughout follow-up (P < 0.05). In Group 2, BSCVA was significantly lower in eyes with advanced keratoconus as compared to those with moderate keratoconus (P = 0.007). At final follow-up, BSCVA ≤ 0.30 logarithm of minimum angle of resolution (logMAR) was achieved in 82.1% of eyes in Group 1 versus 54.5% of eyes in Group 2 (P < 0.001). Groups 1 and 2 were comparable in terms of postoperative spherical equivalent refractive error (P = 0.61) and keratometric astigmatism (P = 0.39). Conclusion: Retention of the posterior corneal stroma which occurs with manual dissection during failed big bubble formation in DALK is associated with lower visual acuity as compared to achieving a bare DM.

Pub.: 20 Apr '16, Pinned: 31 Aug '17

Histopathological changes after deep anterior lamellar keratoplasty using the 'big-bubble technique'.

Abstract: 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.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.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.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.

Pub.: 13 Aug '11, Pinned: 31 Aug '17

Trends in penetrating and anterior lamellar corneal grafting techniques for keratoconus: a national registry study

Abstract: Keratoconus is a progressive disorder and one of the primary indications for corneal transplantation. Anterior lamellar keratoplasty offers several advantages over other techniques, including endothelial preservation and longer graft survival. In this study, we examined the recent trend of using lamellar techniques for keratoconus at a national level.Data were obtained from the Dutch national organ transplant database regarding corneal transplants for keratoconus performed in 2005 through 2014. Baseline characteristics for patients undergoing various techniques were obtained, and temporal trends were analysed.A total of 1041 operations were performed, including 736 penetrating keratoplasties (PKPs) and 297 anterior lamellar keratoplasties (ALKs). The mean age of the total surgical group was 37.4 ± 13.4 years, and 68% of patients were male (p = 0.0001). Preoperative patient characteristics were reported in all 1041 cases. The relative proportion of ALKs increased from 2005 (19% of cases) to 2010 (39% of cases) and remained approximately 30–40% thereafter. Descemet baring or deep anterior lamellar keratoplasty (DALK) was increasingly applied and was the predominant anterior lamellar technique performed from 2009 onwards.The number of corneal transplantations performed annually for keratoconus decreased during the past 10 years. Lamellar techniques were increasingly performed, accounting for approximately 35% of keratoplasties in 2010 and thereafter. Among ALK techniques, maximal depth DALK is the most prevalent keratoplasty performed for keratoconus in most recent years. Penetrating keratoplasty (PKP) is still common, with a stable frequency from 2010 onwards.

Pub.: 07 Apr '16, Pinned: 31 Aug '17

Outcomes of Air Injection Within 2 mm Inside a Deep Trephination for Deep Anterior Lamellar Keratoplasty in Eyes With Keratoconus.

Abstract: To evaluate the outcomes of a new technique for deep anterior lamellar keratoplasty (DALK) employing the injection of air up to 2 mm inside a deep trephination (intended within 100 μm from the endothelial surface) obtained with a guarded trephine set by means of anterior segment optical coherence tomography (AS OCT).Retrospective, noncomparative, interventional case series.The success rate and learning curve of pneumatic dissection in one clinical practice were analyzed in nonscarred keratoconic eyes undergoing a standardized DALK including 9-mm trephination intended to a depth within 100 μm from the endothelial surface, based on the thinnest AS OCT measurement at this site; and injection of air through a cannula advanced 1-2 mm centripetally from the bottom of the trephination. Surgical parameters, success rate of pneumatic dissection, and complications were recorded.Eighty-eight eyes of 88 patients were included in the study. Pneumatic dissection succeeded in 75 of 88 eyes (85%). No significant correlation could be found between number of cases performed and success rate for this surgeon. Complications included loss of suction during trephination (n = 2, 2.3%) and perforation (n = 4, 4.6%). Conversion to penetrating keratoplasty was necessary in 1 case (1.1%).Setting an adjustable trephine to a depth within 100 μm from the endothelial surface eliminates the need for reaching the central cornea for successful pneumatic dissection and substantially flattens the learning curve of DALK, while achieving a constant success rate above 80% and minimizing complications.

Pub.: 17 Jan '16, Pinned: 31 Aug '17

The Big-Bubble Full Femtosecond Laser-Assisted Technique in Deep Anterior Lamellar Keratoplasty.

Abstract: To describe the big-bubble full femtosecond laser-assisted (BBFF) technique, which could be helpful in standardizing the big-bubble technique in deep anterior lamellar keratoplasty (DALK).Ten eyes of 10 consecutive patients affected by keratoconus underwent the BBFF technique using the 150-kHz IntraLase femtosecond laser (Intra-Lase FS Laser; Abbott Medical Optics, Inc., Santa Ana, CA). A 9-mm diameter metal mask with a single fissure 0.7 mm wide oriented at the 12-o'clock position was positioned into the cone, over the laser glass. The laser performed a ring lamellar cut (internal diameter = 3 mm; external diameter = 8 mm) 100 µm above the thinnest point, with the photodisruption effectively occurring only in the corneal stroma corresponding to the fissure to create a deep stromal channel; subsequently, an anterior side cut created an arcuate incision, from the corneal surface to the deep stromal channel on the mask's opening site. The mask was removed and the laser performed a full lamellar cut 200 µm above the thinnest point to create a lamella. After the removal of the lamella, the air needle was inserted into the stromal channel and air was injected to achieve a big bubble.The big bubble was achieved in 9 eyes (all type 1 bubbles) and all procedures were completed as DALK.Preliminary results suggest that the BBFF technique could help in standardizing the big-bubble technique in DALK, reducing the "learning curve" for surgeons who approach this technique and the risks of intraoperative complications.

Pub.: 15 Dec '15, Pinned: 31 Aug '17

Needle Depth and Big-Bubble Success in Deep Anterior Lamellar Keratoplasty: An Ex Vivo Microscope-Integrated OCT Study.

Abstract: To examine big-bubble (BB) formation success rates in deep anterior lamellar keratoplasty (DALK) at various corneal depths using real-time guidance from swept-source, microscope-integrated optical coherence tomography (SS-MIOCT).The DALK procedure was performed ex vivo with 34 human donor corneoscleral buttons on pressurized artificial anterior chambers using the BB technique employed by Anwar and Teichmann. We inserted a needle under controlled ex vivo conditions to corneal depths ranging from 40% to ≥90% using real-time guidance from SS-MIOCT and injected air. BB success was then determined for each injection.The average needle depth for successful full BB formation was 79.9% ± 3.0% compared with 66.9% ± 2.6% for partial BB formation and 49.9% ± 3.4% for no BB formation (P < 0.0001). Expressed as stroma below the needle tip, this corresponded to 123.9 ± 20.0 μm for successful full BB formation compared with 233.7 ± 23.8 μm for partial BB formation and 316.7 ± 17.3 μm for no BB formation (P < 0.0001). All other variables tested (sex, race, age, endothelial cell density, air injected, needle angle, and central corneal thickness) did not significantly affect BB formation success rates.BB formation in DALK is more successful if needle insertion and air injection occur at deeper corneal depth. However, ≥90% corneal depth was not necessary in this ex vivo model of DALK. SS-MIOCT can be used to accurately guide the needle in real time.

Pub.: 22 Jul '16, Pinned: 31 Aug '17

Cannula DALK Versus Needle DALK for Keratoconus.

Abstract: To evaluate outcomes and possible advantages of 2 different techniques of deep anterior lamellar keratoplasty (DALK) in patients with keratoconus: cannula big-bubble DALK and needle big-bubble DALK (Anwar technique).This is a retrospective, nonconsecutive, comparative study of 507 eyes affected by keratoconus that underwent DALK between 2002 and 2012. Needle DALK and cannula DALK techniques were performed in 266 eyes and 241 eyes, respectively. When big bubble (BB) failed, air viscobubble (AVB) was used as a rescue bubble technique. When AVB failed, manual dissection was performed. Main outcomes analyzed were the frequency of descemetic deep anterior lamellar keratoplasty (dDALK) and predescemetic deep anterior lamellar keratoplasty (pdDALK), BB and AVB formation, Descemet membrane rupture, and penetrating keratoplasty conversion.The rate of dDALK achieved was higher (P < 0.01) in the cannula DALK group (94%; 198 BB and 28 AVB) than in the needle group (78%; 161 BB and 46 AVB). The remainder of cases involved pdDALK: 59 cases (22%) and 15 cases (6%) of the needle DALK group and cannula DALK group, respectively. Microperforation occurred in 18 cases spread between both groups. Macroperforation occurred in 5 cases in the needle DALK group. A double chamber occurred in seven cases, between both groups. No penetrating keratoplasty conversion was needed.The use of a smooth cannula during the DALK procedure yields a statistically higher percentage of dDALK and makes the maneuver more manageable compared with air injection with a needle. When BB fails, AVB seems to be a good rescue technique to achieve dDALK.

Pub.: 18 Oct '16, Pinned: 31 Aug '17

Deep Anterior Lamellar Keratoplasty After Descemet Stripping Automated Endothelial Keratoplasty.

Abstract: To report the indications and long-term outcomes of deep anterior lamellar keratoplasty (DALK) performed after Descemet stripping automated endothelial keratoplasty (DSAEK) in cases of visually significant stromal opacities.Retrospective, interventional, consecutive case series.Setting: Private hospital. Study populationThirteen eyes that underwent DALK after DSAEK at our Institution. Indications for DALK after DSAEK included both stromal opacities persisting after DSAEK and stromal opacities occurring secondarily in post-DSAEK corneas. DALK was always performed in a standardized fashion including exchange of a disc of full-thickness recipient cornea (up to the DSAEK stromal surface),7.0 mm in diameter, with a donor lamella obtained by microkeratome-assisted dissection, punched to 7.0 mm and sutured into place with a double running 10-0 nylon suture.Best spectacle-corrected visual acuity (BSCVA), manifest refraction and endothelial cell density (ECD).Mean follow-up was 26±18 months (range=6-60 months). Indications for DSAEK were: full-thickness graft failure (n=8), DSAEK graft failure (n=3) and pseudophakic bullous keratopathy (n=2).Indications for subsequent DALK were: persisting stromal opacity (n=9) and stromal opacities newly occurred after DSAEK as a result of HSV keratitis (n=2) or interface infection (n=2). After complete suture removal, mean BSCVA was 20/28 (0.14±0.8logMAR) in eyes without ocular comorbidities affecting visual acuity (n=7), while refractive astigmatism was within 4 Diopter(D) in all but one eye (average= 3.2±1.4 D). No intraoperative complications were recorded.Performing DALK on DSAEK eliminates the need for open-sky surgery, achieving visual results comparable to those of penetrating keratoplasty, while sparing a healthy endothelial graft.

Pub.: 27 Dec '16, Pinned: 31 Aug '17

Vision-Related Quality of Life Before and After Deep Anterior Lamellar Keratoplasty.

Abstract: To determine changes in the vision-related quality of life in patients undergoing deep anterior lamellar keratoplasty (DALK) by using the 25-item National Eye Institute Visual Function Questionnaire (NEI VFQ-25).Thirty-five patients who were scheduled for DALK between March 1, 2013, and March 1, 2014 were asked to complete the NEI VFQ-25. NEI VFQ-25 was administered again at 6 months and at 1 year postoperatively. Data on patients' age, sex, preoperative diagnosis, preoperative and postoperative best-corrected visual acuity, and postoperative astigmatism were recorded.Successful DALK with the Anwar big bubble technique was achieved in 23 of 35 (65.7%) patients. The indications for surgery were keratoconus in 15 patients (62.2%), stromal corneal dystrophies in 4 (17%), and corneal scar in 4 (17%). The mean preoperative NEI VFQ-25 composite score (55.2±19.7) improved significantly (76.9±11.6) at 6 months after DALK and continued to improve (84.3±6.6) at 1 year postoperatively (Friedman test, P=0.001). All NEI VFQ-25 subscale item scores increased significantly after surgery. The patients' age was significantly correlated with the NEI VFQ-25 subscale score of mental health at 6 month and at 1 year postoperatively (r=0.92, P=0.008 and r=0.94, P=0.005, respectively). There was a negative relationship between postoperative astigmatism at 1 year and NEI VFQ-25 ocular pain, social functioning, peripheral vision, and mental health subscale scores (r=-0.76, P=-0.07; r=-0.53, P=0.2; r=-0.53, P=0.27; r=-0.80, P=0.05).Vision-related quality of life improved significantly after DALK and continued to improve after suture removal.

Pub.: 19 Jan '17, Pinned: 31 Aug '17

Dynamics of big bubble formation in deep anterior lamellar keratoplasty by the big bubble technique: in vitro studies.

Abstract: To examine the movement of air injected in the cornea in simulated deep anterior lamellar keratoplasty (DALK), from the needle tip to the formation of different types of big bubbles (BB) and to ascertain how air travels through the stroma and pre-Descemet's layer [Dua's layer (PDL)] to create a type-1 (air between PDL and deep stroma) and type-2BB (air between PDL and Descemet's membrane).Air was injected in 57 sclerocorneal discs and the passage recorded. Leaking points and sites of commencement of type-1 and type-2BB were examined by scanning electron microscopy. Stromal distribution of air pockets was studied by light microscopy. Uninjected corneas served as controls.Injected air followed a consistent pattern, initially as radial tracks to the limbus, then as circumferential bands along the limbus and finally centripetally to create predominantly a type-1BB. Type-2BB started at the periphery, by air emerging through clusters of tiny fenestrations discovered in the periphery of PDL. Fifteen to 20 such clusters were also seen in control samples on either side of the Descemet's attachment. Type-1BB was formed by air emerging through wide spaces between lamellae of deep stroma. Histologically, the circumferential band revealed an aggregation of air pockets in the mid-stroma.The consistent pattern of passage of air is indicative of the architecture and microanatomy of the corneal stroma where collagen lamellae are orthogonally arranged centrally and as a circular annulus at the periphery. The novel peripheral fenestrations explain the peripheral commencement of a type-2BB and the escape of air into the anterior chamber during DALK.

Pub.: 10 May '17, Pinned: 31 Aug '17

Comparison of outcomes and complications of deep anterior lamellar keratoplasty and penetrating keratoplasty performed in a large group of patients with keratoconus.

Abstract: To compare visual acuity, refraction, topography, and complications of deep anterior lamellar keratoplasty (DALK) and penetrating keratoplasty (PKP) performed in patients with keratoconus (KCN).In this retrospective interventional non-randomized clinical study, patients with moderate to severe KCN that underwent either PKP or DALK for optical corrections were enrolled. The final outcome analysis was performed after complete suture removal for both groups of patients. Best corrected visual acuity, spherical equivalent, refractive cylinder, average keratometry, corneal astigmatism, and endothelial cell density as well as early and late complications such as cataract, glaucoma, corneal edema, elevated intraocular pressure without visual field defect or optic disk changes, rejection, loose suture, and re-suturing were compared.Two hundred and seven eyes were enrolled: 108 eyes underwent DALK, and 99 eyes underwent PKP for keratoconus. The mean follow-up time was 28.06 ± 12.62 months for DALK group and 29.29 ± 12.71 months for PKP. The study groups demonstrated comparable final outcome in terms of best corrected visual acuity: 0.25 ± 0.22 LogMAR and 0.28 ± 0.24 LogMAR (p = 0.415), spherical equivalent: -4.80 ± 4.55D and -3.58 ± 3.58D (p = 0.067), refractive cylinder: -3.37 ± 2.00D and -4.00 ± 2.15D (p = 0.061), average keratometry: 45.51 ± 2.30D and 44.85 ± 2.36D (p = 0.077), corneal astigmatism: 4.89 ± 3.07D and 4.63 ± 2.61D (p = 0.569) in DALK (n = 85) and PKP (n = 72), respectively. However, the postoperative endothelial cell density in DALK (n = 61) 2250 ± 450 cell/mm(2) differs significantly from it in PKP (n = 55) 1795 ± 616 cell/mm(2) p < 0.001. Eyes that had DALK (n = 99) had significantly more risk of loose suture (RR 5.2) and re-suturing (RR 3.6) than PKP (n = 108). However, the risk of cataract following DALKs was less than PKP (OR 0.4).The vision, refractive error, and corneal astigmatism following DALK and PKP were comparable; however, DALK had lower incidence of long-term complications.

Pub.: 24 May '17, Pinned: 31 Aug '17

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

Abstract: 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.Eye advance online publication, 30 June 2017; doi:10.1038/eye.2017.121.

Pub.: 01 Jul '17, Pinned: 31 Aug '17

The "Blue Bubble" technique: an ab-interno approach for Descemet separation in Deep Anterior Lamellar Keratoplasty (DALK) using Trypan Blue Stained Viscoelastic Device.

Abstract: In this study we examined a novel variant of "Big-Bubble" Deep Anterior Lamellar Keratoplasty (DALK) using trypan-blue-stained viscoelastic device for the creation of a pre-Descemetic bubble.Ten corneoscleral rims were mounted on an artificial anterior chamber (AC). The anterior chamber was filled with air through a limbal paracentesis. A Melles' triangulated spatula was inserted through the paracentesis, with its tip penetrating the AC, was then slightly retracted and pushed into the deep stroma above the roof of the paracentesis. A mixture of trypan blue and viscoelastic device (Healon, Abbott Medical Optics, Abbott Park, Illinois) was injected into this intra-stromal pocket using a 27G cannula to create a pre-Descemetic separation bubble. Bubble type and visualization of dyed viscoelastic device were noted. The method was later employed in three cases.In all ten corneoscleral rims the technique successfully created a visible pre-Descemetic (Type 1) bubble that could be expanded up to the predicted diameter of trephination. Subsequent trephination and the removal of corneal stroma were uneventful. In two out of four clinical cases, a type 1 bubble was created, while in two others, visco-dissection failed, and dyed viscoelastic was seen in the AC.The presented technique holds promise of being a relatively easy to perform, predictable and well-controlled alternative for achieving a type 1 bubble during DALK surgery. The trypan-blue-stained viscoelastic device facilitates proper visualization and control of the separation bubble and assists in identifying the penetrance to the separation bubble prior to removal of the stromal cap.

Pub.: 04 Jul '17, Pinned: 31 Aug '17