|Year : 2016 | Volume
| Issue : 1 | Page : 40-42
Corneal changes in soft contact lens wearers
Reshma Ramakrishnan1, Amol D Kadu2, Abhijit Naik1
1 Department of Ophthalmology, Senior Resident, MGM Medical College & Hospitals, Kamothe, Navi Mumbai, Maharashtra, India
2 DNB Ophthalmology, Consultant Ophthalmologist, Vasan Eye Care, Nagpur, Maharashtra, India
|Date of Submission||25-Jul-2014|
|Date of Acceptance||25-Aug-2014|
|Date of Web Publication||19-Jan-2016|
B-604, Neelsiddhi Splendor, Sector 15, Plot 58 & 65, CBD Belapur, Navi Mumbai - 400 614, Maharashtra
Source of Support: None, Conflict of Interest: None
There is abundance of physiological and pathological evidence of individual variations in response to soft contact lens wear. Purpose of the study was to observe and to measure changes in corneal curvature, corneal endothelium, corneal thickness and tear-film status that might occur following soft contact lens wear over a period of 1 year. A prospective study was conducted from November 2009 to October 2011. Thirty subjects, 20 females and 10 males, in the age group of 15-30 years who were fitted with Bausch & Lomb soft contact lenses for the first time, on a 10-12 hours daily wear basis, were evaluated for changes in corneal curvature, corneal endothelium, corneal thickness and tear-film status that might occur following soft contact lens wear over 1 year. We concluded that soft contact lens used on a daily wear basis induces changes in corneal curvature, endothelium, thickness and tear-film status.
Keywords: Corneal changes, complications, soft contact lens
|How to cite this article:|
Ramakrishnan R, Kadu AD, Naik A. Corneal changes in soft contact lens wearers. J Clin Ophthalmol Res 2016;4:40-2
The soft contact lenses generally in use may lead to decrease corneal sensitivity, cause abnormal metabolism and interfere with cell synthesis, resulting in changes in epithelium, stroma and endothelium. Changes in corneal curvature and subjective refraction were found to occur in some wearers. 
The purpose of the study was to observe and to measure the changes in corneal curvature, corneal endothelium, corneal thickness and tear-film status that might occur following soft contact lens wear over a period of 1 year.
| Materials and Methods|| |
This was a prospective study done over a period of 2 years. Thirty subjects, 20 females and 10 males, in the age group of 15-30 years who were fitted with Bausch and Lomb conventional soft contact lenses for the first time were included in the study after appropriate consent and meeting the adequate criteria. The sample size was decided in consultation with a statistician and as per the feasibility at the institute. For power range up to 3.50 diopter (D), 'B'series lenses were advised and for power more than −3.50D, 'U' series lenses were advised. These were yearly disposable, 14.5 mm diameter hydroxyl ethylmethaacrylate (HEMA) lenses. Patients with simple myopia, hypermetropia and astigmatism not more than 2 D were included in the study. Patients with previous history of contact lens wear, pre-existing corneal or conjunctival diseases, past history of trauma, surgery or laser treatment, diagnosed with dry eyes, and those with systemic diseases like diabetes, keloid, connective tissue diseases were excluded. Corneal topography was done with Keraton Scout Optikon 2000. Specular microscopy and corneal thickness was done with non-contact specular microscope "Topcon SP2000P". Intraocular pressure (IOP) was measured with a Goldmann applanation tonometer. Tear-film breakup time was measured and Schirmer's test was done. Fundus examination was done with +90 D lens. Contact lens fit assessment was done and Bausch and Lomb conventional soft contact lenses were prescribed. The subjects were followed up after 1 week and were periodically checked once in a month for 3 months and thereafter during sixth month and twelfth month.
The tests were done using standard instruments by a single observer before and after fitting contact lens in all the follow-up visits.
Ethical clearance from the local review board was taken prior to the study. Also, informed consent was taken from the patients prior to the study.
| Results|| |
Of the population, a majority, 67%, of the subjects were females.
Also, 60% of the subjects presented to the clinic were in the age group 15-20 years, 33% were in the age group 21-25 years and remaining were in the age group 26-30 years.
The precontact lens values and the values at 6 months and at 12 months in corneal curvature, corneal endothelial cell morphology, central corneal thickness, tear-film changes are given in [Figure 1].
After 6 months of contact lens wear, there was an increase of 0.23% corneal curvature in the flat meridian and 0.21% in the steep meridian. Similarly, after 12 months the increase was by 0.51% in the flat meridian and 0.53% in the steep meridian. Both the changes were found to be statistically significant (P < 0.05) [Figure 2].
After 6 months of contact lens wear, there was an increase of 1.48% in the mean cell area [Figure 3].
Changes in coefficient of variance were statistically insignificant.
Endothelial density decreased by 1.13% after 6 months and by 1.56% after 12 months. Both the changes were statistically insignificant (P > 0.05)
Change in central corneal thickness was statistically insignificant.
The changes in all remaining parameters viz. tear-film breakup time, Schirmer's test were statistically significant. Respective graphical representations are given in [Figure 4] and [Figure 5].
The P values and other important statistical analysis results obtained are tabulated in [Figure 6].
| Discussion|| |
Our study showed steepening of 0.22 D in flat and 0.24 D in the steep meridian. This can be attributed to lens-induced hypoxia. It is well established that traditional hydrogel material fail to deliver oxygen to the cornea at levels sufficient to avoid hypoxic consequences. This is in agreement with the studies done by Schornark et al. 
In another study done by Harris et al.,  27 patients wearing F series Bausch and Lomb Soflens contact lenses regularly for 9 months were examined. During the first month of contact lens wear, a mean corneal steepening of 0.23 ± 0.18 D and an increase in with-the-rule toricity were found, A mean increase in myopia of 0.35 ± 0.211 D was found after 9 months of lens wear for five randomly selected patients. These results were comparable with our study results.
Our study showed no significant change in central corneal thickness due to Bausch and Lomb contact lens wear over a period of 1 year. Gonzalez-Meijome et al. showed a statistically significant reduction in central corneal thickness due to soft contact lens wear. This difference was due to the fact that in this study, the subjects wore contact lens on an extended wear basis.
Our study showed a significant reduction in tear-film breakup time and Schirmer's test values in the patients wearing Bausch and Lomb soft contact lens over a period of 1 year. There was a reduction in tear-film breakup time by 1.13 seconds and reduction in Schirmer's test values by 1.09 mm. But tear-film breakup time and Schirmer's test values were within normal range.
Our results are comparable with the results of the study done by Glasson MJ.  But in this study tests were repeated after 6 hours of contact lens wear.
| Conclusion|| |
From this study we have concluded that soft contact lenses used on a daily wear basis induce changes in corneal curvature, corneal endothelium, and tear-film status. Routine slit-lamp examination alone is not sufficient to evaluate these changes; hence, further investigations such as specular microscopy and corneal topography are recommended for long-term wearers.
| Acknowledgement|| |
- Dr. S. Balasubramanian ( DNB Guide)
- Family & Friends
| References|| |
Stein HA, Freema MI, Stein RM, Maund LD. Contact lenses: Fundamentals and clinical use. New Jersey: Slack Incorporated; 1997.
Schornack M. Hydrogel contact lens-induced corneal warpage. Cont Lens Anterior Eye 2003;26:153-9.
Harris MG, Sarver MD, Polse KA. Corneal curvature and refractive error changes associated with wearing hydrogel contact lenses. Am J Optom Physiol Opt 1975;52:313-9.
Gonzalez-Meijome JM, Gonzalez-Perez J, Cervino A, Yebra-Pimentel E, Parafita MA. Changes in corneal structure with continuous wear high-Dk soft contact lenses, A pilot study. Optom Vis Sci 2003;80:440-6.
Glasson MJ, Stapleton F, Keay L, Wilcox MD. The effect of short term contact lens wear on the tear film and ocular surface characteristics of tolerant and intolerant wearers. Cont Lens Anterior Eye 2006;29:41-7.
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]