|Year : 1979 | Volume
| Issue : 2 | Page : 26-31
Steroid pentetration in human aqueous with 'Sauflon 70' lenses
MR Jain, Veena Batra
Department of Ophthalmology, Ravinder Nath Tagore Medical College, Udaipur, India
M R Jain
Department of Ophthalmology, Ravinder Nath Tagore Medical College, Udaipur
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Jain M R, Batra V. Steroid pentetration in human aqueous with 'Sauflon 70' lenses. Indian J Ophthalmol 1979;27:26-31
|How to cite this URL:|
Jain M R, Batra V. Steroid pentetration in human aqueous with 'Sauflon 70' lenses. Indian J Ophthalmol [serial online] 1979 [cited 2020 Sep 23];27:26-31. Available from: http://www.ijo.in/text.asp?1979/27/2/26/31234
Soft contact lenses has remarkable ability to absorb water with a concomitant swelling to a soft mass of good mechanical strength and complete transparency, in addition to their ability to retain shape and dimensions when equiliberated in a given fluid. Therefore this is used as an adjuant for drug delivery for the last decade or so. Sedlacek used the soft lens technique for the application of homatropine and mesocain. Wattman and Kaufman used fluorescein as a model drug with Bionite (Grifin) and softens (Bausch & Lomb) lenses in rabbit eyes and obtained an aqueous concentration four times greater than with frequent drops and observed that the amount of drug taken up by a lens varied with the material of the lens, primarily depending upon its free water content.
Various other workers,,,, have worked with different soft lenses and agree that in most of the eyes, the lenses presoaked in 1 percent pilocarpine controls the intraocular pressure more effectively as well as for much longer duration as compared to frequent instillation of 4 or even 8 per cent pilocarpine drops.
Steroids have been widely employed in ophthalmology to treat various inflammatory conditions of the eye. Sustained high intraocular concentration may produce miraculous results in anterior segment involvement. The study which is probably the first in the literature aims to assess the aqueous concentration of dexamethasone sodium phosphate at various time intervals after applying a presoaked "Sauflon 70" lens on the cornea of normal human beings.
| Material and Methods|| |
Sauflon 70 lenses are Vinyl Pyrollidone Acrylic copolymer with 68 per cent water. Out of this total water, 30 per cent is free and 70 per cent is bound into the structure. The lenses have good oxygen permeability. The lenses used were afocal, 0.22 mm thick, of uniform diameter of 13.50 mm and of various back central radii varying from 7,80 mm to 8.8 mm.
Steroid used was 0.4 per cent solution of dexamethasone sodium phosphate. Solution was prepared fresh every 2nd day and stored in refrigerator. No preservatives were used.
Subject of study were 89 ideal senile cataract cases admitted to S.M.S. Hospital for cataract surgery None of the case had Schiotz intra-ocular pressure more than 22 mm Hg. Keratometry was performed and a lens chosen was 0.2 to 0.5 mm flatter than the flattest meridian so as to have reasonable mobility. Lenses of same diameter and thickness were used in all cases with an aim to avoid the factor of variation in lens volume and surface area.
The lenses were soaked for a minimum of 12 hours in sterile isotonic saline to remove any monomer residue and then placed for 1 minute on a sterile filter paper to remove excess of saline. Thereafter, the lens was soaked in 1 ml of 0.4 per cent dexamethasone solution for 30 minutes, removed, kept for 15 seconds on sterile blotting paper so as to absorb surface coating of the drug and then applied on to the cornea. The lens was kept in position for 30 minutes and then removed. With all sterile precautions, 0.2m1 of aqueous was aspirated with a 26 gauge needle attached to a tuberculin syringe at various time intervals after removal of soft lens i.e. immediately after 15, 30, 45, 60 minutes, 2, 3, 4, 6, 12 and 24 hours. Depending upon the time of removal of aqueous, these 73 cases were classified in 11 groups. The first six groups had 8 cases each and next five had 5 cases each. Removal of aqueous was so timed that it was usually done slightly before cataract surgery or while doing the surgery.
Rest of the 16 cases were labelled as 'Reapplication cases' and grouped separately as group A, B, C and D, each group had 4 cases. In group A & B, the lens was applied for 30 minutes, removed and after 15 minutes another presoaked lens was applied for 30 minutes. In group A, aqueous was aspirated immediately after removal of second lens and in group B, 15 minuters after. In group C and D, first lens was applied for 30 minutes and the next lens was applied after 30 minutes for half an hour. Aqueous was removed immediately after (group C) and 15 minutes after removal of the lens (group D).
The aqueous samples removed were put in autoclaved vials and mixed with 0 .sub 8 ml of methanol to make 1 ml of solution, If required, the samples were stored 4 -sub C till they were estimated.
For estimation purposes, a SYSTRONICS type 103 Spectrocalorimeter which provided continuously variable wavelength of 400 to 700 ηm, was used. Dexamethasone concentration was estimated at the wavelength of 410 nm by the method of Porter and Silber modified by Lawhart and Mattox.
| Results|| |
Males dominated the series with a sex incidence of 7 to 5. Mean age was 58.5 years with a range of 45 to 75 years.
A very high concentration of dexamethasone was obtained in all the aqueous samples aspirated upto 4 hours after removal of soft contact lens [Table l] and [Figure - 1]. The maximum mean concentration noted was 199.37±2.96 microgram/ml in the aqueous samples aspirated immediately after removal of the lens and the concentration persisted to more than 100 microgram/ml upto 2 hours. Samples at 12 hour interval too showed reasonably high concentration of 20.2±2.28 microgram/ml but none of the samples at 24 hour interval showed any evidence of steroid.
Drug concentration in individual cases at various time intervals is shown in [Figure - 2]. The difference in the maximum and minimum steroid concentration at various time intervals noted are 9, 24, 40, 10, 14, 6, 20, 8, 6 micrograms/ml respectively [Figure - 3].
'Reapplication cases' [Figure - 4] demonstrate that by this technique the penetration of the drug can be marginally improved. The maximum mean concentration is achieved in group A cases which is higher by 12.23 microgram/ml from maximum mean figure of single application cases and 5.85, 20.15 and 29.80 microgram/ml higher than group B, C, and D respectively.
| Discussion|| |
Topically applied dexamethasone is reported to penetrate the eye with varying concentration of nil to 4.27 microgram/ml 6, 7, 13, 15. Much better penetration can however, be achieved by prolonging the contact time of the drug to the eye 2sub associated with its slow release. Soft contact lenses due to their approximation with cornea and conjunctiva as well as their quality to imbibe varying amount of drug associated with their unique feature of releasing the drug slowly make them ideal adjuant to drug therapy.
Drugs penetrate hydrophilic contact lenses at a rate which depends upon the pore size between the cross linkages of the three dimensional lattice structure of the lens, upon the concentration of the drug in the soaking solution and upon the molecular size of the drug, Sauflon 70 lenses with high water content lenses, of large pore size, 30 percent of the total 30% free water content is ideal for this.
Most of the studies about soaking time have been confined to pilocarpine solution only. Podos et al observed that with 0.5 percent solution of pilocarpine, the drug uptake appears to increase with time of immersion to approach a maximum after soaking the lens for 30 to 60 minutes. Some of the biochemical studies state that approximately 24 hours soaking is necessary to saturate the Sauflon lens which then holds 400 to 500 microgram of pilocarpine. The release rate of pilocarpine from the soft lens in vivo and in vitro approximates a half life of 30 minutes and almost all pilocarpine is gone after 4 hours of lens wear. We chose half an hour's soak period for its practicability and half an hour's wear since it is optimum to provide maximum concentration of the drug in the shortest period.
No study of presoaked soft contact lenses is available to compare our results of very high concentration of 199.37 + 2.96 microgram/ml immediately after removal of the soft lens and also quite high in consequent samples upto 4 hours. Mean concentration of 20.2±2.28 microgram/ml noted by us even at 12 hours interval is 3 to 4 times higher than the results reported by various teams of workers,,, after frequent instillation of drops. Absence of steroids in 24 hours' samples conclude that single application effect of presoaked soft lens lasts less than 24 hours. It also confirms the earlier observation that the normal human aqueous is devoid of steroids.
Reapplication of presoaked soft contact lenses marginally improves the penetration by a mean figure of 12.23 microgram/ml. Maximum increase was noted in those cases in which the lens was initially applied for half an hour, removed for 15 minutes and another presoaked lens applied for 30 minutes and the samples collected immediately after its removal [Figure - 4] Group A. This mode of drug delivery can certainly be used to provide more intensive and more sustained therapy in some of the severe cases of anterior segment inflammation.
When compared to the drug penetration achieved after subconjunctival injection of 0.5 ml of 0.4 percent dexamethasone sodium phosphate as operated by Jain and Srivastava we noticed that the concentration recorded by us with presoaked soft contact lenses is appreciably low and less sustained. Jain and Srivastava 4 reported a maximum concentration of 268 ± 3.35 microgram/ml within 10 minutes of injection and a high concentration of 123±8.23 microgram/ml upto 24 hours [Figure - 5] Forty eight hours samples, however, showed its complete absence.
Superiority of subconjunctival injections, hence, cannot be disputed and should be a choice of therapy in all cases of severe inflammations of anterior segment of eye. However, in less severe cases, presoaked soft lenses should be the treatment of choice since subconjunctival injection involves an inevitable discomfort, apprehension, medical attendance, and bandaging, of the eyes which imposes psychological restrictions on patients free movement and routine duties whereas, soft lens therapy is devoid of these problems and can be conveniently instituted by the patient himself. To make this mode of therapy more practical, it is suggested that soft contact lens banks should be in vogue so that the lenses can be loaned out to the patients and the steroids without preservative be made commercially available in single dose form.
| Summary|| |
89 senile cataract cases before surgery were the subject of this study. In 73 eyes, 'Sauflon 70' lenses of uniform thickness and diameter soaked in lml of 0. 4 percent dexamethasone sodium phosphate for 30 minutes were applied for half an hour and removed. Aqueous concentration of the drug in samples taken out at various intervals was estimated by colorimetric technique and the maximum mean concentration recorded was 199.37±2.96 microgram/ml. In 16 cases, presoaked lens was reapplied and a marginally higher concentration of the drug was noted. The results have been compared with subconjunctival therapy and the merits and demerits of each discussed.
| Acknowledgement|| |
We are highly indebted to M/S Contact Lens (Manufacturing) limited, London for their supply of 'Sauflon 70' lenses and M/S Cadila Laboratories (India) for the supply of Dexamethosone Sodium Phosphate powder. We are also thankful to Dr. (Miss) Meera Singhal for her keen interest in getting the illustrations prepared.
| References|| |
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Jain, M.R. & Srivastva, S. 1978. Annual congress O.S.U.K. London, April, 1978
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[Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4], [Figure - 5]
[Table - 1]