Glaucoma is a condition in which increased intraocular pressure leads to alteration in the visual function. The symptoms of glaucoma are believed to be caused due to pressure on the posterior part of the eye, especially the lamina cribrosa, which is a part of the back of the eye where the sclera gives way to the retinal ganglion cell axon to leave the eye.

It is essential for the people undergoing treatment for glaucoma to get their IOP (INTRA OCULAR PRESSURE) checked at frequent intervals to evaluate the efficacy of the treatment. Almost all the patients undergo a daytime intraocular pressure measurement at the doctors office due to its convenience. However, the efficacy of the daytime measurement of IOP is under serious debate as people who have well-managed daytime intraocular pressure also complain about the development of the symptoms of progression of glaucoma including visual field defects. Intraocular pressure does not remain the same throughout the day and measuring the extent of fluctuation during 24 hours is the mainstay in deciding the treatment strategy for controlling this risk factor.

Various studies have indicated that patients with low IOP have their disease progressing leading to reduced eyesight. This is supposed to be due to variation in IOP which makes optic nerve vulnerable to increased mechanical stress and strain. The stress on the optic nerve is measured far better through 24- hour variability rather than measuring the IOP only during office hours.

Common methods used for measuring IOP include handheld applanation tonometry, Goldman applanation tonometry (GAT), and pneumotonometry. These methods are largely used in day time settings and are not implemented in 24-hour IOP measurement because they are time-consuming and inconvenient to the patient. Various ambulatory methods for measuring 24-hour IOP have been developed. These methods include permanent IOP monitoring, self-tonometry, and temporary IOP monitoring.

The researchers found that IOP is a principal and only modifiable risk factor for the progression of glaucoma. However, the lack of effective methods for IOP data collection reduces the efficacy of strategies for managing IOP. Various decisions related to the management and surgery for glaucoma are based on ambiguous and unauthenticated IOP data leading to poor outcomes. The IOP characteristics such as mean, peak and fluctuations in IOP should be accurately measured to improve therapeutic efficacy.

A study was done to determine the use of a contact lens sensor device in measuring the 24-hour IOP in the patients who had undergone various interventions in the management of glaucoma. The contact lens sensor device works on the mechanism that fluctuations in intraocular pressure change the curvature of cornea which is measured by this device. This device provides a 24-hour data related to changes in IOP. The study also determines which intervention is the most effective in providing minimum IOP fluctuations.

The study includes 30 centers from sixteen countries and a total of 182 patients were involved. The number of eyes undergone interventions was 182. IOP in 60 eyes was managed through topical medications, incisional surgery was done in 53 eyes, and 69 eyes were with laser trabeculoplasty. The ocular dimensional profile was measured before and after the interventions through CLS (CONTACT LENS SENSOR )

Patients with ocular hypertension, open-angle glaucoma and who are glaucoma suspects were included in the study with a provison that they must have reliable and sufficient CLS readings. Patients who do not have complete and sufficient readings were excluded from the study. Various statistical tools were used during the study such as linear regression and Benjamini-Hochberg approach. Spearman rank correlation coefficient was used to analyze the relationship between changes in CLS parameters and GAT ( GOLDMAN APPLANATION TONOMETER) IOP.

The study concludes that all three interventions, viz, the medications, laser trabeculoplasty and, incisional surgery were effective in managing the IOP. In the patients with incisional surgery, the IOP before and after the intervention was 21.4 mm Hg and 14.7 mm Hg respectively, indicating a mean reduction of 6.8 mm Hg. In the laser trabeculoplasty patients, there was a mean reduction of 2.7 mm Hg with before and after the intervention, IOP measured 17.2 mm Hg and 14.6 mm Hg respectively. The topical medications lower the IOP by 0.97 mm Hg with measured IOP before intervention 18.1 mm Hg and after intervention 17.1 mm Hg.

Incisional surgery was found to be significantly effective on 20 CLS parameters as compared to the other two methods while on one parameter, laser trabeculoplasty was more effective than topical medications. Incisional surgery was found to be predictive for most of the changes in CLS parameters. The researchers indicated that contact lens sensor is an effective method to monitor the 24-hour IOP fluctuations as compared to GAT which is mostly used for day time IOP measurement. The researchers also found that sensitivity was more in nocturnal CLS parameters as compared to diurnal parameters. The authors concluded that this device is effective in measuring the efficacy of the treatment.

A multicenter, retrospective cohort study was conducted on 445 patients at 50 centers in 13 countries. The study also advocates the used of CLS in measuring the IOP. The study indicates that the 24-hour CLS measurements may be associated with previous rates of progression of glaucoma. It is a more convenient and effective method than Goldman which requires multiple time measurements during office hours. The CLS, according to the study, is a useful tool in analyzing the future progression of glaucoma.

In a prospective, cross-sectional study done on forty treated patients, it was found that CLS parameters were related to the field of progression in treated eyes. The device is effective, especially in high-risk eyes, in monitoring IOP while receiving treatment.

Author's Bio: 

Dr. Niteen Dedhia is a Best Eye Surgeon in Mumbai & Best Lasik Specialist Mumbai. He specializes in Cataract Surgery, Bladeless Lasik, LASIK Treatment, Refractive Surgery, Retina Surgery, Custom Blade free Lasik treatment and other eye care services