Menu

  1. Home
  2. /
  3. Glaucoma–I
  4. /
  5. FP283 : Corneal biomechanics...

Share this post

Dr.Divya kesarwani, 

Dr.VAIBHAV KUMAR JAIN,Dr.Vikas Kanaujia,Dr.Kumudini Sharma

Abstract

Purpose: To evaluate the corneal biomechanical properties in patients with connective tissue disorders (CTD), and compare them with age-matched healthy control.

Methods: In this prospective study, 62 patients (study group) with CTDs and 44 healthy subjects (control) underwent Ocular Response Analyzer and corneal pachymetry measurements. Right eye of a subject was assessed for corneal hysteresis (CH), corneal resistance factor (CRF), corneal-compensated intraocular pressure (IOPcc), and Goldmann-correlated intraocular pressure (IOPg), and central corneal thickness (CCT).

Results: Mean CH [9.54±1.66 mm Hg (study group) and 10.62±1.21 mm Hg (control); P=0.013) and mean CRF [9.95±1.47 mm Hg (study group) and 10.76±1.25 mm Hg (control); P=0.040] were significantly different between groups. Mean IOPcc, IOPg, and CCT were not significantly different between groups.

Conclusion: CH and CRF are altered in CTDs which may underestimate IOP so these should be considered in patients with CTDs.

Keywords: Connective tissue disorders; ocular response analyser (ORA), corneal hysteresis; corneal resistance factor

Introduction

Connective tissue disorders (CTDs) are a group of multisystem disease characterized by chronic inflammation of organs rich in connective tissues such as skin, joints, and eye, usually due to the altered immune response including production of autoantibodies and abnormal cell mediated immunity. They include wide array of disorders including systemic lupus erythematosus, rheumatoid arthritis, ankylosing spondylitis, dermatomyositis, systemic sclerosis, and other disorders [1].

Collagen is a part of connective tissue richly found in eye and particularly in cornea. It is hypothesized that corneal stroma rich in collagen might be be affected in CTDs ultrastructurally even without clinical ophthalmic involvement. Corneal biomechanical properties have been shown to be affected in patients with glaucoma and are important to consider when measuring intraocular pressure in earlier studies [2,3]. The ocular response analyzer (ORA, Reichert Inc., Depew, N.Y.) measures intraocular pressure and various corneal biomechanical properties like corneal hysteresis (CH) which is a measure of viscous dampening of cornea, and corneal resistance factor (CRF) which is a resistance factor for deformation of cornea [4].

Earlier studies have evaluated the corneal biomechanical properties using ORA in rheumatoid arthritis, systemic lupus erythematosus, systemic sclerosis, collagen vascular diseases with various conflicting results [5-7]. This is a first study with the highest number of participants with CTDs in which corneal biomechanical properties have been studied and compared with controls.

Materials & methods

In this study, 62 eyes of 62 patients with CTD were assessed for corneal biomechanical properties using ORA in a tertiary care referral hospital from January 2017 to July 2018. The study was carried out according to the Declaration of Helsinki andethical committee clearance was obtained for the same. All patients gave informed consent for participation in the study.

The study group comprised of 62diagnosed cases of CTDs who were already on treatment from immunology department. Fourty-four subjects formed the age-matched healthy control group without CTDs. All participants enrolled were having age >18 years and were free from any ophthalmic and systemic disorders.All participants under underwent comprehensive ophthalmic examination including best-corrected visual acuity (BCVA), slit lamp examination, and fundus examination with +90 D biomicroscopy. For corneal biomechanical properties measurements, Ocular Response Analyzer and corneal pachymetry measurements were performed. Only one eye (right) of a subject was enrolled in the study. All subjects were assessed for corneal hysteresis (CH), corneal resistance factor (CRF), corneal-compensated intraocular pressure (IOPcc), and Goldmann-correlated intraocular pressure (IOPg), and central corneal thickness (CCT). Four or five measurements were obtained for each eye, and the average of these measurements was taken as a final reading.

Results

Sixty-two eyes of 62 patients with CTDs were included in the study group. The mean age of patients with CTDs was 36.87±14.26 years. There were 33 males and 29 females in the study group. All the parameters were comparable between study group and control group (P >0.05) except steroid intake which was present in cases and not in controls.The most common disorder noticed was Rheumatoid arthritis (29.03%), followed by systemic lupus erythematosus (19.35%) and sarcoidosis (19.35%).

Mean CH of study group patients with CTD was 9.54±1.66 mm Hg which was statistically significantly lower compared to the control group having mean CH of 10.62±1.21 mm Hg (P = 0.013). Also, a statistically significantly lower CRF was found in the study group (9.95±1.47 mm Hg) compared to the control group (10.76±1.25 mm Hg) with ‘P’ value of 0.040. Mean IOPcc in study group was 14.45±2.77 mm Hg which was slightly lower compared to the mean IOPcc in the control group (16.0±4.08 mm Hg) but not statistically significant (P = 0.132). Both the study group and control group had comparable mean IOPgc (16.35±2.93 mm Hg in study group; 15.80±4.36 mm Hg in control group; P = 0.612). The difference in CCT was also not significant between the two groups, though it was slightly higher in the study group (P = 0.073).

Discussion

Corneal biomechanical properties are important to consider in connective tissue disorders as it may affect corneal stroma rich in collagen even with no clinically visible alteration. They are highly important when patient is planned for refractive surgery, and measuring intraocular pressure.

There are limited studies regarding corneal biomechanical properties in these patients which provide conflicting results. Yazici, et al. studied corneal biomechanical properties in 30 patients with systemic lupus erythematosus and found that the mean CH, mean CRF, and goldmann correlated IOP were statistically significantly lower compared to control [5]. Whereas another study of 29 patients with scleroderma showed higher CRF and goldmann correlated IOP but comparable CH [7]. In another study by Colaco, et al. 23 patients of collagen vascular disease had no significant difference in mean CH and CRF [8]. We reported significantly lower CH and CRF in our patients with CTDs with comparable goldmann correlated IOP and corneal compensated IOP.

Lower CH found in our patients with CTDs may underestimate IOP that may have clinical implications in the diagnosis and management of glaucoma.

This study highlights an importance of corneal biomechanical properties in connective tissue disorders.

References:

  1. Yanoff M, Duker JS. Ophthalmology: expert consult; 2009 third Ed. Mosby Elsevier, China (p.286;838-843
  2. Kaushik S, Pandav SS, Banger A, Aggarwal K, Gupta A. Relationship between corneal biomechanical properties, central corneal thickness, and intraocular pressure across the spectrum of glaucoma. Am J Ophthalmol 2012;153:840-849.
  3. Liu J, Roberts CJ. Influence of corneal biomechanical properties on intraocular pressure measurement: quantitative analysis. J Cataract Refract Surg 2005;31:146-55.
  4. Luce DA. Determining in vivo biomechanical properties of cornea with an ocular response analyzer. J Cataract Refract Surg 2005;31:156-62.
  5. Yazici AT, Kara N, Yuksel K, Altinkaynak H, Baz O, Bozkurt E, Demirok A. The biomechanical properties of the cornea in patients with systemic lupus erythematosus. Eye (Lond) 2011;25:1005-9.
  6. Can ME, Erten S, Can GD, Cakmak HB, Sarac O, Cagil N. Corneal biomechanical properties in rheumatoid arthritis. Eye Contact Lens 2015;41:382-5.
  7. Emre S, Kayikcioglu O, Ates H, Cinar E, Iceoglu N, Yargucu F, Pirildar T, Oksel F. Corneal hysteresis, corneal resistance factor, and intraocular pressure measurement in patients with scleroderma using the reichert ocular response analyzer. Cornea 2010;29:628-31.
  8. Colaco ML, Franco M, Pinto R, Seco JM. Corneal structure and biomechanics in collagen vascular diseases. Oftalmologia 2014;38:243-7.

Leave a Comment