The Clinical Significance of Changes in the Precorneal Tear Film in Keratoconus in the Interpretation of Tomographic Methods of Corneal Examination

Relevance. Modern methods of corneal keratotopography and tomography play a key role in the diagnosis, monitoring, and surgical treatment planning of keratoconus (KC). However, the accuracy of measurements in KC may be affected by instability of the precorneal tear film (PTF) induced by dry eye syndrome (DES). Purpose: to evaluate the clinical significance of PTF changes in KC on the interpretation of corneal tomographic data and to develop an optimized diagnostic protocol for minimizing their impact. Patients and methods. The study included 115 patients (230 eyes) with bilateral non-operated KC. A comprehensive assessment of PTF status was performed (biomicroscopy of the anterior segment using vital dyes, tear film break-up time — Norn’s test, total and basal tear secretion — Schirmer’s and Jones’ tests), followed by Scheimpflug tomography (evaluating key topographic indices, kerato- and pachymetry, as well as elevation, asphericity, and wavefront aberrations) before and after instillation of sodium hyaluronate-based artificial tears. Results. The results revealed significant PTF instability in KC patients, manifested by reduced tear film break-up time and high corneal staining intensity. After temporary PTF stabilization with artificial tears, a significant decrease was observed in anterior corneal surface indices (ISV, IVA, KI, CKI, IS, IHD), keratometry values (K1, K2, Kmean, Kmax), and aberrations (RMS total, LOA, HOA). Strong correlations were found between PTF status and topographic parameters: positive with staining (r = 0.621–0.787) and negative with tear film break-up time (r = –0.334 to -0.787). Conclusion. PTF impairment in KC significantly distorts tomography results, potentially leading to misdiagnosis of disease progression. Instillation of artificial tears prior to examination improves measurement accuracy by minimizing PTF instability-related artifacts. Implementing standardized PTF assessment and correction in the diagnostic algorithm for KC patients enhances data reproducibility and clinical decision-making reliability.

1. Roberts C. Corneal topography: a review of terms and concepts. J Cataract Refract Surg. 1996 Jun;22(5):624–629. doi: 10.1016/s0886-3350(96)80022-8.

2. Read SA, Collins MJ, Iskander DR, Davis BA. Corneal topography with Scheimpflug imaging and videokeratography: comparative study of normal eyes. J Cataract Refract Surg. 2009 Jun;35(6):1072–1081. doi: 10.1016/j.jcrs.2009.01.020.

3. Feinbaum С. “Wet and Dry Corneal Topography? — A New Contraindication for the LASIK Procedure in Refractive Surgery”. EC Ophthalmology 5.3. 2017:121–128.

4. Klokova OA, Damashauskas RO, Geidenrich MS. Ocular surface treatment in dry eye patients before corneal refractive surgery. Russian Journal of Clinical Ophthalmology. 2020;20(4):180–186. doi: 10.32364/2311-7729-2020-20-4-180-186.

5. Siyahkamari M, Asharlous A, Mirzajani A, Koohian H, Jafarzadepour E, Ostadimoghaddam H, Babaei N, Yekta A, Khabazkhoob M. Effect of Dry Eye Disease on Central Corneal Thickness and Corneal Topometric Indices Measured by Scheimpflug Tomography. Acta Med Iran. 2023;60(12):777–781. doi: 10.18502/acta.v60i12.11831.

6. Kundu G, Shetty R, Khamar P, Gupta S, Mullick R, Ganesan VL, D’Souza S. Impact of tear optics on the repeatability of Pentacam AXL wave and iTrace in measuring anterior segment parameters and aberrations. Indian J Ophthalmol. 2022 Apr;70(4):1150–1157. doi: 10.4103/ijo.IJO_2153_21.

7. Koh S, Maeda N, Ikeda C, Asonuma S, Mitamura H, Oie Y, Soma T, Tsujikawa M, Kawasaki S, Nishida K. Ocular forward light scattering and corneal backward light scattering in patients with dry eye. Invest Ophthalmol Vis Sci. 2014 Sep 18;55(10):6601–6606. doi: 10.1167/iovs.14-15125.

8. Thibos LN, Hong X. Clinical applications of the Shack-Hartmann aberrometer. Optom Vis Sci. 1999 Dec;76(12):817–825. doi: 10.1097/00006324-199912000-00016.

9. Himebaugh NL, Nam J, Bradley A, Liu H, Thibos LN, Begley CG. Scale and spatial distribution of aberrations associated with tear breakup. Optom Vis Sci. 2012 Nov;89(11):1590–600. doi: 10.1097/OPX.0b013e31826cfae5.

10. Liu Z, Pflugfelder SC. Corneal surface regularity and the effect of artificial tears in aqueous tear deficiency. Ophthalmology. 1999 May;106(5):939–943. doi: 10.1016/S0161-6420(99)00513-8.

11. Epitropoulos AT, Matossian C, Berdy GJ, Malhotra RP, Potvin R. Effect of tear osmolarity on repeatability of keratometry for cataract surgery planning. J Cataract Refract Surg. 2015 Aug;41(8):1672–1677. doi: 10.1016/j.jcrs.2015.01.016.

12. Hiraoka T, Asano H, Ogami T, Nakano S, Okamoto Y, Yamada Y, Oshika T. Influence of Dry Eye Disease on the Measurement Repeatability of Corneal Curvature Radius and Axial Length in Patients with Cataract. J Clin Med. 2022 Jan 28;11(3):710. doi: 10.3390/jcm11030710.

13. Yang F, Yang L, Ning X, Liu J, Wang J. Effect of dry eye on the reliability of keratometry for cataract surgery planning. J Fr Ophtalmol. 2024 Feb;47(2):103999. doi: 10.1016/j.jfo.2023.04.016.

14. Taneja M. Commentary: Effect of dry eyes on the corneal diagnostic measurements. Indian J Ophthalmol. 2022 Apr;70(4):1157–1158. doi: 10.4103/ijo.IJO_3119_21.

15. Kim J, Kim MK, Ha Y, Paik HJ, Kim DH. Improved accuracy of intraocular lens power calculation by preoperative management of dry eye disease. BMC Ophthalmol. 2021 Oct 13;21(1):364. doi: 10.1186/s12886-021-02129-5.

16. Montés-Micó R, Alió JL, Charman WN. Dynamic changes in the tear film in dry eyes. Invest Ophthalmol Vis Sci. 2005 May;46(5):1615–1619. doi: 10.1167/iovs.05-0017.

17. Koh S, Maeda N. Wavefront sensing and the dynamics of tear film. Cornea. 2007 Oct;26(9 Suppl 1):S41–S45. doi: 10.1097/ICO.0b013e31812f69e8.

18. Denoyer A, Rabut G, Baudouin C. Tear film aberration dynamics and vision-related quality of life in patients with dry eye disease. Ophthalmology. 2012 Sep;119(9):1811– 1818. doi: 10.1016/j.ophtha.2012.03.004.

19. Kasem AMM, Awara AM, Shafik HM, Shalaby OE. Corneal topography and wavefront data changes in dry eye. Tanta Medical Journal. 2021;49(1):31–36 doi: 10.4103/tmj.tmj_199_20.

20. Rochet E, Levron A, Agard E, Chehab HE, Plas H, Bouvarel H, Chirpaz N, Billant J, Dot C. Should Artificial Tears Be Used During the Preoperative Assessment of Toric IOLs Before Age-Related Cataract Surgery? The TORIDE Study. J Refract Surg. 2021 Nov;37(11):759–766. doi: 10.3928/1081597X-20210826-01.

21. Diaz-Valle D, Arriola-Villalobos P, García-Vidal SE, Sánchez-Pulgarín M, Borrego Sanz L, Gegúndez-Fernández JA, Benitez-Del-Castillo JM. Effect of lubricating eyedrops on ocular light scattering as a measure of vision quality in patients with dry eye. J Cataract Refract Surg. 2012 Jul;38(7):1192–1197. doi: 10.1016/j.jcrs.2012.02.040.

22. Montés-Micó R, Cerviño A, Ferrer-Blasco T, García-Lázaro S, Ortí-Navarro S. Optical quality after instillation of eyedrops in dry-eye syndrome. J Cataract Refract Surg. 2010 Jun;36(6):935–940. doi: 10.1016/j.jcrs.2009.12.044.

23. Avetisov SE, Averich VV, Pateyuk LS. Keratoconus: main lines of research. Russian Annals of Ophthalmology 2023;139(3.2):11–20 (In Russ.). doi: 10.17116/oftalma202313903211.

24. Dogru M, Karakaya H, Ozçetin H, Ertürk H, Yücel A, Ozmen A, Baykara M, Tsubota K. Tear function and ocular surface changes in keratoconus. Ophthalmology. 2003 Jun;110(6):1110–1118. doi: 10.1016/S0161-6420(03)00261-6.

25. Carracedo G., Recchioni A., Alejandre-Alba N., Martin-Gil A., Crooke A., Morote I.J., Pintor J. Signs and Symptoms of Dry Eye in Keratoconus Patients: A Pilot Study. Curr Eye Res. 2015;40(11):1088–1094. doi: 10.3109/02713683.2014.987871.

26. Bubnova IA, Averich VV. State of the precorneal tear film in keratoconus. Modern technologies in ophthalmology. 2020;4:319–320 (In Russ.). doi: 10.25276/2312-4911-2020-4-319-320.

27. Constantin MM, Corbu C, Potop V. Evaluation of Dry Eye Symptomatology at Patients with Keratoconus. Revista de Chimie. 2019;70(1):92–95. doi: 10.37358/RC.19.1.6858.

28. Bubnova IA, Egorova GB, Averich VV, Mitichkina TS. Medical treatment for dry eye in patients with keratoconus after corneal cross-linking. Russian Journal of Clinical Ophthalmology. 2020;20(2):67–71 (In Russ.). doi: 10.32364/2311-7729-2020-20-2-67-71.

29. Averich VV, Bubnova IA. Changes in the precorneal tear film at various stages of keratoconus. Russian Annals of Ophthalmology. 2024;140(3):43–49 (In Russ.). doi: 10.17116/oftalma202414003143.

30. Rattan SA, Anwar DS. Comparison of corneal epithelial thickness profile in dry eye patients, keratoconus suspect, and healthy eyes. Eur J Ophthalmol. 2020 Nov;30(6):1506– 1511. doi: 10.1177/1120672120952034.

31. Averich VV. Dry eye disease in keratoconus: etiology and medical treatment. Russian Journal of Clinical Ophthalmology. 2022;22(2):122–126 (In Russ.). doi: 10.32364/2311-7729-2022-22-2-122-126.

32. Mirza E, Oltulu R, Oltulu P, Mirza GD, Okka M. Dry eye disease and ocular surface characteristics in patients with keratoconus. Saudi J Ophthalmol. 2022 Jul 11;36(1):117–121. doi: 10.4103/sjopt.sjopt_37.

33. Zemova E, Eppig T, Seitz B, Toropygin S, Arnold S, Langenbucher A, Gräber S, Szentmáry N. Interaction between topographic/tomographic parameters and dry eye disease in keratoconus patients. Curr Eye Res. 2014 Jan;39(1):1–8. doi: 10.3109/02713683.2013.798667.

34. Brzhesky VV, Egorova GB, Egorov EA. Dry eye syndrome and diseases of the ocular surface: clinical features, diagnostics, treatment. Moscow: GEOTAR-Media; 2016 (In Russ.).