Virtual Transcanalicular Laser-Assisted Dacryocystorhynostomy
Coauthors: M.A. ALAÑON FERNANDEZ; A. MARTINEZ FERNANDEZ; M. CARDENAS LARA

Abstract:
PURPOSE: To realize a virtual surgery.
MATERIAL AND METHOD: The most developed computer technologies are used to obtain a spatial vision of his basics foundations.
RESULTS: A minimally invasive surgery of the lacrimal surgery in 3D is show.
CONCLUSIONS: The new technologies help us at understanding and to design a surgical technique.

Advanced Techniques in Transcanalicular Laser-Assisted Dacryocystorhynostomy
Coauthors: M.A. ALAÑON FERNANDEZ; A. MARTINEZ FERNANDEZ; M. CARDENAS LARA

Abstract:
INTRODUCTION: The reduction of the surgery time with the utilization of the laser in the DCR has led us to realizing this intervention with topical anesthesia as well as other significant modifications.
PURPOSE: To describe the utilization of topical anesthesia by our technique as well as the parameters, way of utilization of the laser, types of optical fibers and the use of mitomycin C.
RESULTS: The aim of our study in the treatment of the lacrimal system is the search of techniques easiest to realize and less traumatic for the patient, using the innovations that suppose the endoscopy and the laser.

Kinetic Model of the Schirmer-Holly Lacrimation Test
Coauthors: Dry Eye Institute, Yantis, TX75497, U.S.A.

Abstract:
Capillary flow of fluid in porous unbonded paper strips will be shown under three boundary conditions:
1. Unlimited fluid supply, 2. Constant fluid supply, 3. Exponentially decreasing fluid supply, and its mechanism explained by animated schematic drawings. Basically the actual wetting rate of the paper strip is shown as a function of time simultaneously for the various fluid supplies under conditions that exist during the classical Schirmer test. The strip wetting rate during the test will be exhibited and the effect of two important factors: the evaporation rate from the strip surface and the lipid content of the paper will be examined. Frequent mistakes by the administrator of the test will be enumerated and their effects on the final result demonstrated.
The behavior as a function of the boundary conditions will be depicted and the limitation of the test will be shown. The results and different limitation of the thread test will be included.
Then a new method will be suggested and its functioning visualized by animated kinetic drawings which will demonstrate how the method is conducted and what actually happens both in the eye and in the paper strip. Three readings will be taken starting at the appearance of the wetted front (time 0’), then a short time later (t 1), then at a later time (t 2) and at a final time (t 3). These three readings of wetted length employing a specially designed and prepared Schirmer-Holly strip, the initial lacrimation rate and the final basal tear secretion rate can be obtained and the magnitude of the exponential lacrimation decay can be estimated.
These three kinetics parameters can be routinely obtained in the clinic and will enable the physician to characterize the lacrimation kinetics of the patient. Such results in term of the actual tear secretion rates can be used to decide with a greater accuracy and confidence whether the lacrimal secretion kinetic of a given patient is sufficiently abnormal to lead to a dry eye.

Management of Epithelial Adhesive Failure by Osmotic Flow
Coauthors: Dry Eye Institute, Yantis, TX75497, U.S.A.

Abstract:
The tentative mechanism of recurrent epithelial erosion will be reproduced in animation and the weak boundary layer (WBL) hypothesis of adhesive failure expounded. The disjoining pressure of two adjacent solids with a aqueous layer in between will be demonstrated and explained with animated schematic drawings. Its importance in ocular surgery will also be described and the cases illustrated.
Since osmotic processes are part of the healing process, the often mysterious sounding osmotic processes will be depicted and fully explained using animated schematic drawings. The difference between hydraulic and osmotic flow will be explained with animations. The absence of pressure during osmotic flow and the concept of osmotic (and oncotic) pressures will be explained.
Basically the phenomenon occurs when a solution is separated from a solvent of a different solution. The separator is usually a semi-permeable membrane that is not permeable to the solutes.
However, this is not always the case. If one of the compartments is a gel with a small pore size and the other is a solution of macromolecules, then depending on the relation of imbibition pressure of the gel and the colloidal osmolality of the macromolecular solution there may be a net flow into or out of the gel.
The semi-permeable membrane will be represented by a healthy intact epithelium. Such a membrane in the case of diseased, waterlogged (microcystic edema) epithelium cease to exist so the semi-permeability of the epithelium is lost. The stroma, on the other hand, is a meshwork of collagen fibrils imbeded in the ground substance. The tissue is partially dehydrated and thus have a negative swelling (imbibition) pressure.
These concepts will be visualized and explained by animation. The effect of hyperosmotic solutions on healthy corneas and on corneas with injured epithelium will be demonstrated and the concept oncotic pressure defined.
The colloidal osmotic flow across intact and diseased corneal epithelium contrasted to crystaloid osmosis will be explained by the animated view of these processes including the explanation of osmotic versus hydraulic flow.

Mechanism of Lid Lubrication
Coauthors: Dry Eye Institute, Yantis, TX75497, U.S.A.

Abstract:
The actual lubrication mechanism of the rapidly moving superior tarsus is a matter of some controversy. Until 1994 the boundary mechanism was the only mechanism of action proposed by two researchers more than two decades apart. In 1994 it was postulated by Holly and Holly that in the normal eye the lubricating layer is a continuous aqueous tear layer and the mechanism thus is hydrodynamic lubrication.
These latter authors did not completely exclude the presence of boundary lubrication in the eye and suggested that when the continuity of the lubricating tear layer under the lid is interrupted then the default mechanism of the lid lubrication indeed could be a boundary type lubrication mechanism. The magnitude of the drag will be considerably higher damaging the surface epithelium especially under dry eye conditions. Interestingly, the same degree of "wear" can be caused by a sudden increase in the viscosity of the lubricating layer by the instillation of artificial tears with high viscosity.
The video will depict animated version of processes and forces existing during the lid movement. The concept of Derjaguin’s disjoining pressure will be visualized as it applies to the lid-globe system. Changes introduced by contact lens wear and lasik surgery will be shown and their adverse effects demonstrated.
It is of interest to note that the science of lubrication, in existence since the XIXth century, which was almost exclusively concerned with metal surfaces lubricated by oil, has not concerned itself with either the stability of the lubricating layer or with the magnitude of the disjoining pressure in the lubricating layer (which defined only in 1942). It also did not postulate or found necessary to suggest that the lubricating medium should contain surface active properties or posses either visco-elastic or elastico-viscous properties. Such concerns only emerged in medical sciences, more than a century later, where the solids to be lubricated are either tissues as in the eye or bone or cartilage in other moving parts of the body and the lubricating medium has an aqueous character.

Tear Film Formation, Stability, and Rupture
Coauthors: Dry Eye Institute, Yantis, TX75497, U.S.A.

Abstract:
The video will show the schematic representation of the tear film that only exists in the open eye and consists of two fluid layer one aqueous and one lipid at a 100 to one ratio in thickness. The aqueous tear layer continues under the lid filling the fornices while the lipid layer is restrained by the lid edges. In the normal eye the lipid layer is unable to penetrate under the lid, so when the eye is closing, the upper lid edge compresses the lipid layer which will increase in thickness from 1 nm to 100 nm. In the closed eye there is only one intact (continuous) aqueous tear layer under the lid which serves as a lubricating layer providing hydrodynamic lubrication.
The upper lid opens fast and starts to create a tear/air interface. Since the lacrimal surface-active agents in the tears are all macromolecular, upon creation of a new interface with air these molecules are slow to migrate to the surface. So initially there is a pure water surface with high surface tension on which the lipids that had accumulated at the lower lid edge will rapidly spread. As measurements conducted with tear film component analogues indicate the spreading lipid is faster than the opening lid.
It is known that in the open eye is a considerable interaction between the lipid molecules and protein molecules. When this lipid/protein layer is compressed again at the next blink, some of the protein may detach but some will stay. The compression of such a lipid-protein film can lead temporarily to very low surface tension values, low enough to be capable of wetting even Teflon!
The structure of the tear film near and including the tear meniscus will be shown at high magnification and the various events occurring in the open eye will be illustrated as they result in dry spot formation. The phenomenon of the local thinning at the meniscus (black line) will be also shown in animation and its role in dry spot formation demonstrated.

Conjuntivorhinostomy (CR), with Jones tubes, Classic Approach
Coauthors: Guillermo FRIDICH; Juan Pablo ALDECOA

Abstract:
PURPOSE: To present a video of a CR with Jones tubes, in an external approach.
METHODS: We described the surgery, from the nasal incision. The dissection of the soft tissues, the osteotomy, the resection of the sac and the nasal mucosa. After we resected the caruncula and we show the insertion of the tube, through the osteotomy, we mention the helpful of a nasal endoscope, at the end of the procedure, to observe the right position of the tube and finally the post-op, from the nasal and the ocular view.
RESULTS: We can see the technique of a CR, with a Jones tube. Similar as described by Lester Jones, in all his stages.
CONCLUSIONS: CR with Jones tube, has a lot of complications, but we believe is a good technique for canalicular obstructions, or failures of DCR, which need surgery.

Dacriocistorhinostomy (DCR), External Aproach
Coauthors: Julio PEREZ ALVAREZ; Patricio NAVARRO

Abstract:
PURPOSE: To present a video of a DCR technique, with an external approach.
METHODS: We describe an external DCR done with microscope. We show the dacriocistograpy previously and the surgery from the skin incision. The dissection of the soft tissues and the osteotomy, then the opening of the lacrimal sac and nasal mucosa, to make the flaps and the placing of the silicon tube. The suture of the posterior flap and anterior, and the suture of the nasal wound. We show the ostium in the nasal fosa with an endoscope, six months later.
RESULTS: We can observe a DCR surgery done by an external approach, in the classical way.
CONCLUSION: New techniques are looking for his place in DCR prcedures, as transcanalicular laser or endonasal surgerys, but external DCR is always a good chance, especially in great sacs or failures of the other techniques.