The Prevalence of Refractive errors Among a Sample of Syrian Population with Keratoconus

Abstract

Abstract Introduction: Keratoconus is an ectatic disease of the cornea characterized by central or paracentral thinning and steepening that causes a cone-like protrusion of the cornea resulting in reduction in patient's visual acuity usually with progressive myopia and astigmatism. This study was conducted to investigate the prevalence of refractive errors and grading among a sample of Syrian patients with Keratoconus. Methods and Materials: It is a prospective cross-sectional study conducted at Damascus hospital in Syria between the period (September 2021 till the end of April 2022). The study included both newly diagnosed patients as well as patients doing checkups for their previously diagnosed KCN at the time of study. The topographical variables studied are as follows: Kmax, TL, Pachy apex, and maximum posterior and anterior elevation data measured with (BFTE) reference body within the 8-mm diameter zone. Uncorrected and best corrected distal visual acuities were determined by subjective refraction tests. A phoropter was used to subjectively define the patient's eyeglass prescription and refraction errors. All done without cycloplegic drugs Results: The sample size analyzed was 93 patients corresponding to 173 eyes. Unilateral involvement was (7.5%) and bilateral KCN was (92.5%) with a male to female distribution (44.1%) to (55.9%) respectively. Mean age was 29.7 ±10.9 within the range of [ 9 - 72 years]. The mean values for topographical variables measured were as follows: K.max (52.7 ± 6.07 D [range; 43 - 74.5]), TL (473.3 ± 43.1 µm [range; 343 - 609]), Pachy (486.05 ± 41.17 µm [range; 369 - 612]), Maximum anterior elevation (14.53 ± 10.08 µm [range; 2 - 48]) and Maximum posterior elevation (31.05 ± 19.36 µm [range; 5 - 93]). Regarding refractive status, mean spherical refraction was: -1.87 ± 3.69 [range: 10.25 to −17.00 D], mean cylindrical refraction was: -2.85 ± 1.9 [range: 0.00 to −10.00] and mean SE refraction was: -3.30 ± 3.98 [range: 8.75 to −20.50 D]. The mean values of the measured UDVA (log Mar) for 149 eyes was 0.5 ± 0.4 [range: 0 to 1.30] and of BCVA (log Mar) with spectacles was 0.14 ± 0.19 [range: 0 to 1.00]. In terms of KCN grading moderate grade was the most common (43.1%) followed by mild grade (45.1%) as for severe grade it accounted for (11.0%) in total. Compound myopic astigmatism (57.2%) constituted the majority of cases followed by Simple myopic astigmatism (23.1%) and Mixed astigmatism (9.9%). Correlation between absolute value of SE and Kmax (r = 0.669, P-value = 0.000) and with TL (r = -0.393, P-value = 0.000) Conclusion: The clinical profile of keratoconus in Syrian patients is comparable to other studies worldwide with it being more frequent in females and having Compound myopic astigmatism being the most common refractive error related to eyes with keratoconus.