Keratometric changes after pterygium excision
Keywords:Conjunctival autograft, Corneal astigmatism, Keratometry, Pterygium
Background: A pterygium is a wing-shaped growth of conjunctiva and fibrovascular tissue on the superficial cornea. The pathogenesis of pterygia is strongly correlated with UV light exposure and environmental factors. The prevalence of pterygia increases steadily with proximity to the equator, and the condition is more common in men than women. It is well established fact that before entering the optical zone pterygium causes flattening of the cornea in horizontal meridian with the more normal side of the cornea usually temporally, resulting in with-the-rule astigmatism.
Methods: The study included 80 patients of primary pterygium who underwent pterygium excision with conjunctival autograft adhered by autologous blood surgery. After performing routine ocular examination which includes visual acuity without and with pinhole and pre-operative keratomery was assessed by autokeratorefractometer. Repeat examination was performed after 6 weeks of surgery. Patients with recurrent pterygium, pseudo-pterygium, and history of previous ocular surgery were excluded.
Results: The pre‑ and postoperative corneal astigmatism were compared after 6 weeks of surgery. The changes in corneal astigmatism were statistically significant p value <0.001. The preoperative mean corneal astigmatism of 3.41 D was reduced to 1.59 D (p value <0.001) 6 weeks after surgery, but maximum change in astigmatism was seen in Grade IV >Grade III >Grade II >Grade I.
Conclusions: Primary pterygium of all grades treated with well accepted technique pterygium excision with conjunctival autograft with autologous blood gives promising results in terms of improvement in corneal astigmatism and hence visual acuity as well.
Lin A, Stern G. Correlation between pterygium size and induced corneal astigmatism. Cornea. 1998 Jan;17(1):28-30.
Fong KS, Balakrishnan V, Chee SP, Tan DT. Refractive change following pterygium surgery. CLAO J: Office Publicat Contact Lens Assoc Ophthalmol, Inc. 1998 Apr;24(2):115-7.
Saw SM, Tan D. Pterygium: prevalence, demography and risk factors. Ophthal Epidemiol. 1999 Jan 1;6(3):219-28.
Seitz B, Gütay A, Küchle M, Kus MM, Langenbucher A. Impact of pterygium size on corneal topography and visual acuity-a prospective clinical cross-sectional study. Klinische Monatsblatter fur Augenheilkunde. 2001 Sep;218(9):609-15.
Maheshwari S. Effect of pterygium excision on pterygium induced astigmatism. Ind J Ophthalmol. 2003 Jun 1;51(2):187-8.
Gumus K, Erkilic K, Topaktas D, Colin J. Effect of pterygia on refractive indices, corneal topography, and ocular aberrations. Cornea. 2011;30(1):24-9.
Kheirkhah A, Safi H, Molaei S, Nazari R, Behrouz MJ, Raju VK. Effects of pterygium surgery on front and back corneal astigmatism. Canadian J Ophthalmol. 2012 Oct 1;47(5):423-8.
Mohammadi SF, Tahvildari M, Z-Mehrjardi H. Physiology of Astigmatism, Astigmatism - Optics, Physiology and Management. In: Goggin M. eds. ISBN: 978-953-51-0230-4, InTech; 2012:1-14.
Bhandari V, Rao CL, Ganesh S, Brar S. Visual outcome and efficacy of conjunctival autograft, harvested from the body of pterygium in pterygium excision. Clini Ophthalmol (Auckland, NZ). 2015;9:2285.
Mohite US, Dole NB, Jadhav SS. Effectiveness of pterygium surgery on corneal astigmatism. Med Pulse Int J Ophthalmol. 2017;3:12-7.
Pajic B, Aebersold DM, Eggspuehler A, Theler FR, Studer HP. Biomechanical Modeling of Pterygium Radiation Surgery: A Retrospective Case Study. Sensors. 2017 Jun;17(6):1200.