The pH of multi-purpose soft contact lens solutions

Osmolality and pH of commercially available contact lens care solutions and eye drops

PURPOSE

The physical properties of contact lens care solutions and Eye Drops (ED) may affect initial comfort and dry eye symptomatology in contact lens wearers, although these properties are not always provided by manufacturers. The present study aimed to measure and compare the osmolality and pH of commercially available contact lens care solutions and ED.

METHODS

Forty-four solutions were tested (17 lens care solutions and 27 ED) and classified by the presence and/or combination of the viscosity/lubrication-enhancing ingredients. Solution osmolality was obtained with the Fiske 110 osmometer and pH was measured with a micro-pH 2000. Each measurement was taken ten times, following the manufacturer's instructions, while controlling for room temperature and humidity. Differences between the values of the physical properties of the solutions were analysed by type and viscosity/lubrication-enhancing agent subclassification.

RESULTS

Osmolality ranged from 192.6 ± 2.17 to 364.6 ± 2.88 mOsm/Kg, while pH ranged from 6.35 [6.35-6.26] to 7.99 [7.99-8.00]. A significant difference in the osmolality and pH values of contact lens care solutions and ED was found when classified by type or viscosity/lubrication-enhancing agent (ANOVA and Kruskal-Wallis respectively, both p < 0.001).

CONCLUSIONS

The physical properties of some contact lens care solutions and ED are not readily available. The osmolality and pH values of various commercially available lens care solutions and ED vary significantly both by type and viscosity/lubrication-enhancing ingredients.

Physical properties of soft contact lens solutions

PURPOSE

To investigate the physical properties of commercially available soft contact lens solutions.

METHODS

The pH, osmolality, surface tension (ST), and viscosity of various soft contact lens solutions were measured at room temperature. Viscosity measurements were also taken at 34 degrees C. The solutions examined were Opti-Free Express (OFX), Opti-Free RepleniSH (OFR), Complete Moisture Plus (COM), UltraCare (UC), ReNu MultiPlus, Sensitive Eyes, AOSept (AO), Clear Care, SoloCare Aqua, and SoftWear saline. The peroxide solutions were measured before and after neutralization.

RESULTS

The pH of most solutions was close to neutral (range 7.00-7.36), except for OFX and neutralized AO and Clear Care. The osmolality values of most solutions were in the 275 to 310 mOsm/kg range. OFX exhibited a significantly lower osmolality (225 mOsm/kg; p < 0.001), whereas UC was significantly higher (329 mOsm/kg; p < 0.001). Neutralized AO and SoftWear saline had ST values of approximately 67 mN/m. OFX, OFR, and SoloCare Aqua exhibited low ST values in the 30 to 35 mN/m range. The remaining solutions exhibited intermediate ST values of approximately 40 mN/m. These three groupings were significantly different (p < 0.001). The average viscosity of most solutions at room temperature was between 0.95 and 1.26 cP, except for COM (3.02 cP; p < 0.001). At 34 degrees C, the average viscosity of most solutions was between 0.70 and 0.83 cP, except for COM, which had a viscosity of 1.92 cP (p < 0.001). The un-neutralized peroxide solutions had very different pH and osmolality values from all the solutions that would directly contact the eye (p < 0.001). Their viscosity and ST values were similar (p = NS).

CONCLUSIONS

This study detailed many physical properties of soft lens solutions that are not readily available and indicated that certain properties vary significantly among these products.

Cataract and glaucoma after wear of contact lens soaked in steroid solution: a rare complication

PURPOSE

To report an unusual case of steroid-induced cataract and glaucoma after wearing soft contact lens soaked in steroid solution.

METHODS

Case report of a 28-year-old man who presented with progressive decrease in vision of both the eyes of 2 years' duration. He was wearing conventional soft contact lens from the past 3 years. He used to buy the lenses from an optician and started storing the lenses in steroid solution overnight for the last 2 years.

RESULTS

His best-corrected visual acuity was 20/40 in both the eyes. Anterior segment evaluation revealed posterior subcapsular cataract in both the eyes. IOP was 12 mm of Hg in the right eye and 22 mm of Hg in the left eye. Fundus examination showed a cup disc ratio 0.9:1 in the right eye and 0.8:1 in the left eye. Humphrey visual fields revealed incomplete biarcuate scotoma in both the eyes.

CONCLUSIONS

Steroid-induced cataract and glaucoma in a contact lens wearer is an extremely rare complication. To our knowledge, there is no previous case of steroid-induced cataract and glaucoma in a conventional soft contact lens wearer. This case emphasizes the role of optometrists and ophthalmologists in patient education while dispensing contact lenses, especially in developing countries.

Contact lens-associated chemical burn

We present the case of a young man who presented as an ophthalmic casualty after inserting a pair of bizarre-effect cosmetic hydrogel contact lenses while in a night-club. He failed to follow the manufacturer's guidelines and inserted the lenses before neutralising the storage solution. On presentation he was found to have bilateral corneal epithelial defects which required hospital treatment for 4 days. He appears to have suffered no long-term sequelae.