Anterior chamber fluid

Another formulation variable that must be considered is that of the solution pH and bulfer capacity. Since the anterior chamber fluid (aqueous humor) contains essentially the same buffering systems as the blood, products with a pH outside the physiological range of 7.0-7.4 are converted to this range by the buffering capacity of the aqueous humor if a relatively small volume of the solution is introduced. Often,... 

FIGURE 23.5 The eye is effectively a sphere within a sphere with radii of 7.8 and 11.5 mm as shown. The relative volumes of vitreous humor and anterior chamber fluid are indicated. 

Penetration of Proteolytic Drugs, Administered by Different Methods, into Anterior Chamber Fluid... 

Drugs were administered by means of topical instillation, subconjunctival injection or electrophoresis (current 0.5 mA, exposure 10 min). A combination of the above mechanisms was employed as well. Anterior chamber fluids were extracted by way of syringe with puncturing of the anterior chamber at hourly intervals following the administration of the drugs. Anson s biochemical method was used for assessing the proteolytic activity of anterior chamber fluid. 

As a result of our experiments, we established (Tab. 1) that the peak activity of anterior chamber fluid was attained following administration of direct action enzyme drugs of vegetable (lekosim) and microbial (protelin) origin. 

Direct action enzyme drugs of animal origin (chymotrypsin) and plasmin activator (streptase) produced a moderate increase of activity of anterior chamber fluid. Peak proteolytic activity was recorded one hour following administration of drugs irrespective of the mechanisms by which enzymes were introduced, high proteolytic concentrations occurred for an average of 3 hours and then started to decrease drastically. 

Subconjunctival injection of 1.0 Fip lekosim with subsequent electrophoresis proved to be the means of attaining maximum proteolytic activity of anterior chamber fluids. 

The penetration into the tissue follows the initial breakdown of the epithelial barrier. This results in an immediate and strong edema of the conjunctiva, known as chemosis, due to a water influx from the surrounding tissue, vascular leakage, tears, and applied fluids. The cornea itself loads up with ions to a measured osmolarity of 1,830 mOsmol/kg after a 1 mol NaOH bum for 30 s [24]. The penetration of strong alkali has been systematically tested on sodium hydroxide by means of evaluation of the anterior chamber pH. This pH change typically occurs within 2 min after exposure of the comeal surface. The change of the cornea... 

The comparison of all rinsing fluid based on their effect on the anterior chamber pH is presented in the following figures. All experiments were repeated five times and mean and standard deviation are given to elucidate the variance of the experimental set up. There is clear evidence that only some solutions buffer acids and alkali (Eigs. 6.11-6.13). These solutions are polyvalent and are Diphoterine and the phosphate buffer of higher concentration like the plum pH neutral. Borate buffer has a high capacity to buffer alkali but a low capacity to buffer acids. 

Reversible cholinesterase inhibitors find their greatest clinical use in the treatment of open-angle glaucoma. Relief is achieved by enhancing the contraction of the ciliary muscle and the iris sphincter. This contracture pulls the iris off the lens and facilitates fluid movement through the canal of Schlemm. The result is decreased pressure with reduced distortion of the lens and increased movement of aqueous humor out of the anterior chamber of the eye. 

When a choroidal effusion (Figure 30-4) is detected without a wound leak, the patient can be treated with topical corticosteroids, such as 1% prednisolone acetate, one drop every 2 to 4 hours, with or without cycloplegia, such as homatropine 5% or atropine sulfate 1%, one drop two to four times daily. Routine topical antibiotics should be continued. When medical management fails to resolve the choroidal detachment (effusion) or if anterior synechiae form, consideration should be given to draining the fluid and re-forming the anterior chamber. 

The available evidence suggests that gold is deposited in the cornea and lens by circulation in the aqueous fluid in the anterior chamber. 

The presence of protein in the cerebrospinal fluid in one patient with bilateral conjimctivitis, areflexic mydriasis, severe anterior chamber shallowing, myopic shift, and vitritis suggests that a common inflammatory mechanism may occur due to the topiramate use. 

CARBONIC ANHYDRASE INHIBITORS (e.g. acetazolamide and dichlorphenamide) are weak diuretics, but are now rarely used to treat S3tstemic oedema, though useful in reducing fluid in the anterior chamber of the eye where it is causing raised intraocular pressure (glaucoma). 

The importance of viscosity at rest in ophthalmic surgery lies in the fact that viscoelastic fluids with a high viscosity value are particularly effective in deepening the anterior chamber, especially with raised vitreous pressure. Fluids with a very low value, such as irrigation solutions, require a constant flow to deepen the anterior chamber. 

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