Peripheral Corneal Incisions Research Articles

Early corneal pachymetry maps after cataract surgery and influence of 3D digital visualization system in minimizing corneal oedema.

To describe the early topography of corneal swelling occurring after cataract surgery and to evaluate the impact of the three-dimensional (3D) digital visualization system in minimizing corneal oedema. Prospective observational, single-centre, consecutive case series of 134 patients undergoing cataract surgery performed by the same surgeon, with either 3D or conventional visualization systems. Eyes were assigned to two groups based on their anterior chamber depth (group ACD ≤3 mm and group ACD >3 mm). Optical coherence tomography was performed to evaluate postoperative corneal swelling. Three corneal swelling profiles were identified on the first postoperative day type 1, limited corneal oedema near peripheral corneal incisions; type 2, dome-shaped corneal swelling spreading from the principal corneal incision and reaching the paracentral cornea; type 3, continuous oedema spreading from the principal incision to central cornea, with a generalized oedema predominating in the upper part of the cornea. On the first day after surgery, in group ACD ≤3 mm, visual acuity was significantly better in patients undergoing surgery with 3D visualization (0.023 vs 0.072 logMar, p = 0.014) with reduced central corneal thickening 17.3 µm (±3.2) in comparison with conventional visualization 44.0 µm (±9.3) (p = 0.0082). In group ACD >3 mm, no significant association was found between the use of the 3D system and pachymetry changes and early visual rehabilitation. On day 21 after surgery, no significant differences in corneal pachymetry values were observed between the two surgical approaches in both groups. We describe early postoperative corneal map profiles providing insight into the pathogenesis of postoperative corneal swelling and possible prevention strategies. By improving visualization of the narrow surgical space in patients with shallow anterior chambers, the 3D system could help to minimize postoperative corneal oedema.

A New Technique for Diode Laser Cyclophotocoagulation

Destruction of the ciliary body, an option in glaucoma surgical treatment, can be performed using various methods. Laser energy, now the principle source for cyclodestruction, can be delivered in a transpupillar, transvitreal in conjunction with a vitrectomy and transscleral manner. The current technique for endocyclophotocoagulation requires of an endoscopic probe. We describe an accessible and inexpensive alternative. Gonioprism-assisted diode cyclophotocoagulation (GADC) with a peripheral corneal approach is a new surgical technique for pseudophakic and aphakic patients that uses a manual gonioprism, iris hooks, ophthalmic operating microscope, and an 810-nm laser diode probe. GADC is performed under topical and intracameral anesthesia, prior pupil dilation. First, 4 iris hooks are placed to expose the posterior chamber. The ciliary processes are viewed through a Swan-Jacob gonioprism and the diode laser probe is inserted through a peripheral corneal incision. The energy of the laser is set at 250 mW and the duration of the application to each process is variable, from 500 to 800 ms, until shrinkage and whitening occur. We apply this technique in approximately 360 degrees of the ciliary processes. Subconjunctival dexamethasone phosphate is administered at the end of the surgery prior subconjunctival injection of lidocaine. GADC has a relatively quick learning curve, allows direct visualization with less energy delivered to the ciliary processes and obviates the acquisition of a new endoscopic device.

Management of post-goniopuncture iris herniation: a two-step procedure

A 38-year-old male presented to the emergency room suffering acute pain in his left eye. Two months before he had been submitted to uneventful non-penetrating deep sclerectomy and one month before to YAG-laser goniopuncture. Examination showed iris herniation into the trabeculo-descemet's window. Surgical reduction was carried out through a peripheral corneal incision, and a large air bubble was injected into the anterior chamber. Four days later a wide laser peripheral iridotomy was performed. This technique can transform a non-penetrating technique into a full-trabeculectomy, without reopening the superficial flap.

Analysis of aqueous humour proteins in patients with retinoblastoma

To investigate aqueous humour protein composition from retinoblastoma patients. Prospective, hospital-based study. Eighteen retinoblastoma patients (Reese-Ellsworth stage V or ABC classification group E RB) undergoing ocular enucleation, and 10 normal subjects undergoing cataract surgery. Five of 18 patients presented with associated secondary glaucoma whereas 13 had no secondary glaucoma; 5 of 13 patients with no secondary glaucoma received chemotherapeutical treatment with melphalan. Aqueous humour samples were collected by limbal paracentesis of the anterior chamber after ocular enucleation in patients and after the stab peripheral corneal incision in controls. Total protein concentration according to Bradford method and sodium dodecyl sulphate-polyacrylamide gel electrophoresis of the samples were performed. Aqueous humour protein concentration. Aqueous humour protein concentration was significantly higher in retinoblastoma patients than controls (P < 0.01); patients with secondary glaucoma presented the highest values (P < 0.05 vs. controls); patients treated with melphalan presented a significant decrease (P < 0.01) versus non-treated; controls did not significantly differ from treated patients. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis pattern in retinoblastoma patients who did not receive any treatment was very different either from treated or from controls. This study represents a preliminary step towards a more accurate two dimensional electrophoresis (2DE) pattern, which will be combined with mass spectrometry analysis to clarify the potential role of specific proteins in tumour development and progression; although these results suggest that aqueous humour protein pattern in retinoblastoma is characteristic, several aspects of the study are still under investigation.

Early Bubble Modification of the Big Bubble Technique for Deep Anterior Lamellar Keratoplasty

We modified the deep anterior lamellar keratoplasty big bubble technique to improve safety and ease of performance. We describe a modification of the big bubble technique that involves injecting the air bubble through a peripheral corneal incision 1 mm from the limbus. The incision is made with a limbal relaxing incision knife. This is done before trephination of the recipient cornea, hence the name "early bubble." The goal of this technique is to reduce the risk of intraoperative corneal perforation and to obtain a large air bubble between Descemet membrane and the corneal stroma. We report outcomes of this technique in 21 eyes. At 6 months, 16 eyes showed a best-corrected visual acuity of 20/50; the remaining eyes had a best-corrected visual acuity of 20/80 or better. The postoperative corneal astigmatism was 3.6+/-0.9 diopters at 3 months and 3.15+/-0.67 diopters at 6 months. The rate of conversion to penetrating keratoplasty was 14%. We found that the "early bubble" technique improved the ease of performance, safety, and predictability of deep anterior lamellar keratoplasty.

Using the Second Instrument Peripheral Corneal Incision in Phacoemulsification as a Blow-Off Valve

To assess the rise in intraocular pressure following phacoemulsification and whether it can be modified by the architecture of the peripheral corneal incision for the second instrument. Frimley Park Hospital, Frimley, United Kingdom. Forty-two patients had intraocular pressures measured from both eyes preoperatively, then underwent routine scleral section phacoemulsification. They were randomly assigned to perpendicular (blow-off valve) and oblique (water-tight) peripheral corneal incision groups. Postoperative intraocular pressures were measured at 3, 6, 12 and 18 hours. Pressures from the unoperated eyes were used as controls. Aqueous release from the second instrument peripheral corneal incisions and frown scleral incision were assessed using the Seidel's test. There was a rise in intraocular pressure in both groups compared to the control eyes (mean 10.95+/-2.19 mmHg, P<0.00005) at 6 hours. The difference between the groups was significant at 12 hours (mean difference 3.35 mmHg, P<0.05); 63.6% of the perpendicular incisions and 15% of the oblique incisions were Seidel's positive. The frown incision did not leak. This study documents the natural history of the rise in intraocular pressure following phacoemulsification peaking at 6 hours. Pharmacological agents should be administered to cover this period. The perpendicular peripheral corneal incision had a tendency to act as a blow-off valve allowing release of aqueous when intraocular pressures were elevated in the first 18 hours following phacoemulsification. This phenomenon is likely to result in a reduction in rise of intraocular pressure compared to the oblique peripheral corneal incision group which tended to be water-tight.

Differential Distribution of Subchains of the Basement Membrane Components Type IV Collagen and Laminin Among the Amniotic Membrane, Cornea, and Conjunctiva

Amniotic membrane transplantation has been reported to be an effective surgical procedure for the reconstruction of the anterior segment of the eye. To understand better the function of transplanted amniotic membrane, we compared the distributions of subchains of type IV collagen and laminin in the amniotic membrane to those in the cornea and conjunctiva. Five human corneas with conjunctivas and three human amniotic membranes were frozen in OCT compound. Cryosections were cut with a cryostat and stained by an indirect immunofluorescent microscopy. We used antibodies of the collagen alpha2(IV) and alpha5(IV) subchains, laminin-1, laminin-5, fibronectin, and type VII collagen. In the conjunctival basement membrane and the amniotic membrane, fluorescence was evident for collagen alpha2(IV) but not for collagen alpha5(IV). By contrast, in the corneal basement membrane, fluorescence was apparent for the collagen alpha5(IV) subchain but not for the collagen alpha2(IV) subchain. Laminin-1, laminin-5, fibronectin, and type VII collagen were present in all the basement membranes examined. The distribution of alpha subchains of type IV collagen in the amniotic membrane was identical to that in the conjunctiva but different from that in the cornea. No difference in the distribution pattern of other basement membrane components was observed. These results demonstrate that the basement membrane of the amniotic membrane and the conjunctiva might share the same components; therefore, the amniotic membrane might be useful as a replacement for the basement membrane of the conjunctiva.

Removal of a Corneal Foreign Body Through a Lamellar Corneal Pocket

A piece of glass was found in the posterior central cornea of a 43-year-old victim of a motor vehicle accident. The original entry of the foreign body had healed and epithelialized. This foreign body was removed through a peripheral corneal incision and corneal stromal pocket extended to the glass particle. This technique avoids creation of a corneal incision near the optical axis and prevents unwanted distortion of the corneal topography. The authors report this case to emphasize the importance of preserving corneal topography in corneal surgery.

Experimental myopia in chickens induced by corneal astigmatism.

Astigmatism has been suggested to be an important factor in the production and/or progression of myopia. Chickens have been used as a myopic animal model for several years. In the present investigation our aim was to evaluate the importance of surgically induced corneal astigmatism by peripheral corneal incision with compression suture in one eye, the right, of 3-day-old chicks. Vertical incision (2 mm) with compression suture (nylon 9-0, one stitch) induces against-the-rule astigmatism, horizontal incision with compression induces with-the-rule astigmatism. Four groups were studied 1) with one vertical cut, 2) one horizontal cut, 3) two vertical cuts, 4) two horizontal cuts. The eyes were measured by caliper after 8 weeks. Eye enlargements were induced in all groups, however, less by one cut (astigmatism around 5 diopters) than by two cuts (astigmatism 10 diopters, or more). In the latter groups the pattern of equatorial eye enlargement depended on the axis of the induced astigmatism, the greater elongation being associated with the strongest refracting corneal meridian. All considered, the results suggest that significant corneal astigmatism could be another factor in the production of myopia, possibly acting by way of optical degradation of retinal image quality.