Various studies have demonstrated that patients with keratoconus have significant loss of contrast sensitivity while its value varies in different studies. None of these studies has analysed reduced contrast sensitivity depending on the position of apex of corneal conus. Visual acuity and contrast sensitivity were evaluated for patients with keratoconus using the FrACT software. Contrast sensitivity was assessed at the following frequencies: 1, 3, 5, 7, 9, 11, 13, and 15 cycles per degree (cpd). Twenty-four eyes with keratoconus were analysed. Contrast sensitivity was significantly lower for patients with the apex at the centre compared with apex on the periphery both with (p = 0.0078) and without (p = 0.0078) spectacle correction. For patients with the apex at the centre, contrast sensitivity was significantly different with and without correction (0.02); however, there was no difference for patients with apex on the periphery (p = 0.06). The results showed that if the keratoconus apex is at the centre, then spectacle correction improves contrast sensitivity at lower spatial frequencies (1, 3, and 5 cpd), while it remains unchanged at medium and high spatial frequencies. If the keratoconus apex is on the periphery, spectacle correction does not improve contrast sensitivity.
Bach, M. (2007). The Freiburg Visual Acuity Test-Variability unchanged by post-hoc re-analysis. Graefe's Arch. Clin. Exper. Ophthalmol., 245 (7), 965-971.
Brown, B., Lovie-Kitchin, J. E. (1989). High and low contrast acuity and clinical contrast sensitivity tested in a normal population. Optom. Vis. Sci., 66 (7), 467-473.
Carney, L. G., Lembach, R. G. (1991). Management of keratoconus: Comparative visual assessments. CLAO J., 17 (1), 52-58.
de Freitas Santos Paranhos, J., Avila, M. P., Paranhos, A. Jr., Schor, P. (2010). Evaluation of the impact of intracorneal ring segments implantations on the quality of life of patients with keratoconus using the NEI-RQL (National Eye Institute Refractive Error Quality of life) instrument. Brit. J. Ophthalmol., 94 (1), 101-105.
de Freitas Santos Paranhos, J., Paranhos, Jr. A., Avila, M. P., Schor, P. (2011). Analysis of the correlation between ophthalmic examination and quality of life outcomes following intracorneal ring segment implantation for keratoconus. Arquivos Brasileiros de Oftalmologia, 74 (6), 410-413.
Hess, R. F., Carney, L. G. (1979). Vision through an abnormal cornea: A pilot study of the relationship between visual loss from corneal distortion, corneal edema, keratoconus, and some allied corneal pathology. Investig. Ophthalmol. Vis. Sci., 18 (5), 476-83.
Jinabhai, A., O’Donnell, C., Radhakrishnan, H., Nourrit, V. (2012). Forward light scatter and contrast sensitivity in keratoconus patients. Contact Lens Anterior Eye, 35 (1), 22-27.
Kennedy, R. S., Dunlap, W. P. (1990). Assessment of the Vistech contrast sensitivity test for repeated-measures applications. Optom. Vis. Sci., 67 (4), 248-251.
Kymes, S. M., Walline, J. J., Zadnik, K., Gordon, M. O., the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study Group. (2004). Quality of life in keratoconus. Amer. J. Ophthalmol., 138 (4), 527-535.
Kymes, S. M., Walline, J. J., Zadnik, K., Sterling, J., Gordon, M. O., on behalf of the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study Group. (2008). Changes in the quality of life of people with keratoconus. Amer. J. Ophthalmol., 145 (4), 611-617.
Marsack, J. D., Parker, K. E., Pesudovs, K., Donnelly, W. J. 3rd., Applegate, R. A. (2007). Uncorrected wavefront error and visual performance during RGP wear in keratoconus. Optom. Vis. Sci., 84 (6), 463-469.
Owsley, C. (2003). Contrast sensitivity. Ophthalmol. Clin. North Amer., 16 (2), 171-177.
Rabinowitz, Y. S. (1998). Keratoconus. Survey Ophthalmol., 42 (4), 297-319.
Stein, R., Stein, R. (2011). Corneal collagen crosslinking: A major breakthrough in the management of keratoconus, pellucid marginal degeneration, and ectasia after LASIK. Ophthalmol. Rounds, 9 (1), 1-5.
Jadidi, K., Mosavi, S. A., Nejat, F., Naderi, M., Janani, L., Serahati, S. (2015). Intrastromal corneal ring segment implantation (Keraring 355°) in patients with central keratoconus: 6-month follow-up. J. Ophthalmol., doi: