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Year : 2016  |  Volume : 8  |  Issue : 1  |  Page : 20-25

Clinical profile of keratoconus patients in Sudan

1 Department of Contact Lenses, Faculty of Optometry and Visual Science, Al-Neelain University, Khartoum, Sudan
2 Department of Ophthalmology, Faculty of Medicine, Al-Neelain University, Khartoum, Sudan
3 Department of Contact Lenses, Faculty of Optometry and Visual Science, Al-Neelain University, Khartoum, Sudan; Department of Optometry, Faculty of Applied Health Sciences, Qassim University, Qassim, Saudi Arabia

Date of Web Publication17-Jun-2016

Correspondence Address:
Mustafa Abdu
Department of Contact Lenses, Faculty of Optometry and Visual Science, Al-Neelain University, Khartoum
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/1858-540X.184235

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Background: Understanding the clinical profile of keratoconus is important in the diagnosis and management of the disease. Aim: This study aimed to investigate the clinical characteristics of keratoconus patients in Sudan with respect to age and gender. Materials and Methods: Clinical records of keratoconus patients were retrospectively reviewed in a period between April and June 2015. Records were collected from Makkah Eye Complex, Alwaledain Eye Charity Hospital and Sudan Eye Center, Khartoum City. Parameters investigated included patient's demography, keratometric readings, visual acuity, and manifest refraction. Classification of keratoconus was based on Amsler-Krumeich grading system. Results: A total of 208 patients' record was found diagnosed with keratoconus. The mean age of subjects was 21.43 ± 8.91 years. Around 78% of subjects were found with bilateral keratoconus. Analysis showed that keratoconus is more common in males (55.8%) than in females (44.2%) and manifest in young age (late teenage and early 20s). Age was not correlated with disease severity (P > 0.05). No significant difference was found between both genders in term of age, visual acuities, and severity of keratoconus (P > 0.05). Conclusion: Clinical profile of Sudanese keratoconus patients looks similar to that reported earlier worldwide.

Keywords: Keratoconus, keratometric reading, manifest refraction

How to cite this article:
Abdu M, Binnawi KH, Elmadina AM, Hassan R. Clinical profile of keratoconus patients in Sudan. Sudanese J Ophthalmol 2016;8:20-5

How to cite this URL:
Abdu M, Binnawi KH, Elmadina AM, Hassan R. Clinical profile of keratoconus patients in Sudan. Sudanese J Ophthalmol [serial online] 2016 [cited 2023 Jan 31];8:20-5. Available from: https://www.sjopthal.net/text.asp?2016/8/1/20/184235

  Introduction Top

Keratoconus is the most common primary ectasia [1] defined as a noninflammatory degeneration of the central or paracentral cornea of unknown etiology.[2] It is characterized by the formation of a localized protrusion and thinning of the stroma, which is greatest at the apex of the cone, and results in increasing irregular astigmatism.[3]

Estimates of the incidence and prevalence of keratoconus in any population depend heavily on the diagnostic criteria used.[4],[5],[6] The differences in the rates usually attribute to different definitions and diagnostic tools employed between the different studies.[7]

Awareness of the factors influencing the development of keratoconus is important in the prevention, diagnosis, and management of the condition. It is possible that there are some age and gender variation in the incidence and development of keratoconus. Understanding these variations is important for the management of keratoconus in Sudan so that early intervention can be provided and the quality of life can be preserved.

This retrospective study was planned with the aim of understanding the demographic pattern of keratoconus in Sudan with respect to age and gender. This is the first reported data on keratoconus in Sudan.

  Materials and Methods Top

Clinical records from the Cornea Department at Makkah Eye Complex, Alwalidain Eye Hospital and Sudan Eye Centre (from April 2010 to January 2016) were retrospectively reviewed; all subjects who diagnosed as keratoconus or those who were under the treatment of keratoconus were selected and included in the study.

The included patients were diagnosed keratoconus patients who were referred by ophthalmologists and optometrists for further management. Diagnosis of keratoconus in all centers was based on patients' complaints of frequently changing spectacles, slit lamp biomicroscopic findings (either conical protrusion of the cornea at the apex, Fleischer ring, Vogt's striae, or corneal scar) in at least one eye and central corneal curvature measured by keratometers. Any patient with a history of ophthalmic surgery or ophthalmic disease other than keratoconus was excluded from this study.

The parameters reviewed were patient's demographics (age and gender) keratometric reading (steepest, flattest, and mean), slit lamp biomicroscopic findings, manifest refraction, best-corrected visual acuity (BCVA) using Snellen chart, and the type of correction prescribed. For statistical analysis, Snellen visual acuity (VA) values were converted to decimal notation.

Keratoconus can be classified according to the shape of the cone and severity level (based on central keratometric [K] reading). In this study, classification of keratoconus was based on the central corneal curvature values measured by keratometer following the Amsler-Krumeich grading system.[8] Mean K was calculated automatically from the mean value of flattest and steepest central curvatures. Accordingly, keratoconus was classified as mild, moderate, advanced, and severe [Table 1].
Table 1: Keratoconus classification based on the central corneal curvature (a modified Amsler-Krumeich scale)

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Results were evaluated using statistical analysis software (IBM SPSS 20, IBM Corp., Armonk, NY). Descriptive statistics (mean ± standard deviation [SD], frequency) were carried out for all study parameters. Normality of data in every group was tested using the normal probability plots. An independent sample t-test was used to compare the mean of parameters reviewed between both genders. The relationships between age and mean keratometric reading, manifest refraction, and BCVA were analyzed using Pearson's correlation coefficient. For inferential statistics, the right eyes were used in the analysis. Significant level was <0.05.

  Results Top

A total of 208 patients' records (370 eyes) were found diagnosed as keratoconus and retrospectively reviewed. The mean age of subjects was 21.43 ± 8.91 (range: 10-65). Males/females distribution was 116 (55.8%) and 92 (44.2%), respectively. From the total number of subjects, 162 (77.9%) had bilateral keratoconus and 46 (22.1%) were diagnosed as unilateral keratoconus [Table 2].
Table 2: Illustrates the demographic characteristic of the study subjects

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With regard to vision data, mean unaided VA was 0.19 ± 0.18 (range: 0.01-1.00), mean VA with spectacle correction was 0.43 ± 0.27 (range: 0.01-1.00). With contact lenses prescribed mean BCVA was 0.81 ± 0.29 (0.03-1.00). Majority of eyes (286 eyes, 77.29%) showed VA of 0.7 (6/9) or better.

In term of refractive status, mean spherical amount of refractive was −5.59 ± 4.14 (range: −0.50 to −22.00D) and mean cylindrical amount of refraction was −4.34 ± 2.77 (range: 0.00 to −19.00). Mean spherical equivalent (SE) of refraction was −6.93 ± 4.80 (range: −0.50 to −23.00D).

With regard to corneal power and curvature, mean flattest keratometric reading (K1) was 49.63 ± 6.45 (range: 40.63-76.70D). Mean steepest keratometric reading (K2) was 53.14 ± 6.34 (range: 41.63-73.21D). Mean average keratometric reading was 51.43 ± 5.77 (range: 41.63-72.10D) and mean flattest radius of corneal curvature was 6.88 ± 0.79 mm while mean steepest radius of corneal curvature was 6.82 ± 074 mm. Regarding disease severity, 35.68% of subjects were categorized as mild keratoconus, 29.73% as moderate keratoconus, 9.73% as advance keratoconus, while 24.86% were found with the severe stage of keratoconus.

A total of 54.23% (201) of the eyes were treated with different rigid gas-permeable (RGP) contact lenses, and only 8.21% (60) of the eyes were prescribed with spectacles. Regarding surgical intervention, 17.84% (66) of the eyes was underwent corneal cross-linking, 9.46% (35) of eyes underwent penetrating keraoplasty, and only 2.16% (8) eyes were treated with complete intracorneal ring implantation (MyoRing) [Table 3].
Table 3: The type of correction prescribed to the subjects

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An independent sample t-test was used to compare between males and females regarding mean age. Prior to the test, normality and equality of variance were investigated and found not violated. The test showed no significant difference between males (mean = 22.04, SD = 7.42) and females (mean = 20.65, SD = 9.05), t (206) =1.23, P = 0.22.

To assess the size and direction of the linear relationship between subjects age and mean VA (unaided, with spectacle and with RGP lenses), mean refraction (spherical component, cylindrical component, and SE), and mean keratometric reading (Sim K1, Sim K2, and average K), a bivariate Person's correlation coefficient (r) were used. Subjects' right eyes were only used in these correlations. Significant negative correlation was found between age and VA taken without correction (unaided), with spectacles and with RGP contact lenses with P value of 0.03, 0.04, and 0.01, respectively [Figure 1], [Figure 2], [Figure 3]. No significant correlation was found between age and Sim K1, Sim K2, and mean K with P values of 0.89, 0.97, and 0.96, respectively. However, no significant correlation was found between age and all the values of radius of curvature (P > 0.05).
Figure 1: Correlation between age and unaided visual acuity

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Figure 2: Correlation between age and visual acuity with spectacle

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Figure 3: Correlation between age and visual acuity with rigid gas-permeable contact lens

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Statistically significant positive correlation was detected between age and cylindrical component of refraction (r = 0.15, P = 0.04) [Figure 4], while no significant correlation was found between age and spherical component of refraction (r = 0.08, P = 0.36) and between age and SE of refraction SE (r = 0.09, P = 0.28). [Table 4] illustrates the correlation values between age and VA, refraction and mean K readings.
Figure 4: Correlation between age and cylindrical component of refraction

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Table 4: Correlations between age and unaided VA, RGP VA, SE, and mean K

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An independent sample test was used to compare the mean result of unaided VA, spectacle VA, and VA with RGP between males and females. The t-test indicated no significant differences between both genders in unaided VA (P = 0.51), visual acuity with spectacle (SPVA) (P = 0.95), and RGP VA (P = 0.07).

The test was also used to compare the mean of the results of Sim K1, Sim K2, mean K, and SE of refraction SE between males and females. The test showed no significant difference between gender in Sim K1 (P = 0.88), Sim K2 (P = 0.63), and mean K (P = 0.75). The significant differences were found only in SE of refraction SE (P = 0.02). Means of unaided VA, SPVA, RGP VA, keratometric readings, and refractive status regarding both genders were illustrated in [Table 5].
Table 5: Means of parameters investigated in respect to both genders

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  Discussion Top

The prevalence and incidence of keratoconus were variable. Ertan and Muftuoglu [9] estimated the prevalence of 50-230 per 100,000 in the general population (approximately, 1 per 2000-1 per 500) in Turkey, while Nielsen et al.[5] estimated the prevalence of 86 per 100,000 residents in Denmark. In this study, we could not calculate the prevalence and it seems higher than that reported in literature and it could not be the indicator for the frequency of keratoconus in Sudan as patients in this study were referred to these centers for follow-up examinations and contact lens fitting.

Keratoconus usually affects both eyes, but it can affect one eye earlier than the other.[10] The estimated prevalence of unilateral keratoconus ranges from 14.3% to 41% in several earlier studies.[8],[10] The current study showed that 22.1% of the subjects were diagnosed as unilateral keratoconus. This finding was higher compared to Wilson et al.[11] who reported prevalence from only 0.5% to 4% of unilateral keratoconus using computerized videokeratoscopic techniques. Variations between studies may be due to variations in methods used for diagnosing keratoconus. Higher prevalence of unilateral keratoconus found in this study may be due to subjects were recruited from a tertiary center.

No previous studies reported the incidence of keratoconus in Africa. However, several studies were conducted in Asian and Caucasian countries. Kok et al.[12] who studied keratoconus in Asia reported that compared to Caucasian, Asians were younger at diagnosis with a range of 18-24 years old. Georgiou et al.[13] also found that Asian patients with keratoconus in the UK were significantly younger at disease presentation than white patients with the mean age of 21.5 and 26.4 years, respectively. Similarly, the current study showed a mean age of 21.43 ± 8.19 years and this represented mean age detected from records but not the age of onset of keratoconus. However, we can expect that keratoconus onset among Sudanese patients was at late teenage or the early 20s of age.

Older patients were expected to have more severe disease due to the progression of the condition.[14] Wagner et al.[15] reported that early incidence of keratoconus was associated with worsening of disease. However, in this study, there was no statistically significant correlation between age and disease severity, and between age and refractive error, and between age and mean K, but a significant negative correlation was detected between age and VA without correction, with spectacle, and with RGP contact lenses. These results suggest that age may be not a factor in determining the level of severity of the disease but it may be a factor in determining visual outcomes.

Awareness of gender-based difference is important in prevention, diagnosis, and management of conditions or diseases. In this study, a higher percentage of males (55.8%) was found to have keratoconus. This finding supported many recent studies which reported that most keratoconus patients were males.[16],[17],[18] Owens and Gamble [19] found that 59% out of 673 keratoconus patients studied in New Zealand were males. Lim and Vogt [16] also reported a predominance of males (61.5%) in their study on keratoconus at a specialist contact lens clinic in London. Recently, in the Singapore keratoconus study, Khor et al. also found a predominance of males (62.9%) than females.[17]

No statistically significant difference was detected between gender and age. This result indicated that keratoconus affects both genders in a similar age. This is in contrast with a study by Fink et al.[20] who found that the mean age of women at the time of diagnoses was older than that of men. The authors suggested the possibility of keratoconus to develop at an earlier age in men and progresses more rapidly.

Results of unaided VA, spectacle VA, VA with RGP, and mean K showed no statistically significant difference (P > 0.05) between males and females. The significant differences were found only in SE of refraction. Further analysis showed no association between gender and severity of keratoconus. Thus, it can be stated that the disease progresses equally in both genders with same visual and refractive effects which contradict the earlier study reported by Fink et al.[20]

Among the 1209 keratoconus patient in the Collaborative Longitudinal Evaluation of Keratoconus study, 74% were prescribed with different types of contact lenses, while a smaller proportion wore spectacles as their primary vision correction.[15] Approximately, similar results were found in the present study as 54.23% of the total eyes were using different types of contact lenses, while only 8.21% of eyes were prescribed with glasses as they were diagnosed at an early stage of the disease or patients were not keen to wear contact lenses. These findings contrary with many studies in other developing countries, which reported less prevalence in the use of optical corrections, especially contact lenses because of the higher cost of lenses and a relatively lower number of contact lens practitioners.[12],[21] A noticeable number of eyes (approximately, one-third) underwent either corneal cross-linking or corneal graft or intracorneal continuous ring implantation among the study patients as they reached the advanced phase of the condition.

  Conclusion Top

The main results from this study showed that clinical profile of Sudanese keratoconus patients looks similar to that reported earlier in previous studies.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Zadnik K, Barr JT, Gordon MO, Edrington TB. Biomicroscopic signs and disease severity in keratoconus. Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study Group. Cornea 1996;15:139-46.  Back to cited text no. 1
Romero-Jiménez M, Santodomingo-Rubido J, Wolffsohn JS. Keratoconus: A review. Cont Lens Anterior Eye 2010;33:157-66.  Back to cited text no. 2
Rabinowitz YS, Yang H, Rasheed K, Li X. Longitudinal analysis of the fellow eyes in unilateral keratoconus. IOVS 2003;44:1311-5.  Back to cited text no. 3
Zadnik K, Edrington TB. Keratoconus. In: Silbert JA, editor. Anterior Segment Complication of Contact Lens Wear. 2nd ed. Canada: Butterworth-Heinemann; 2000. p. 353-61.  Back to cited text no. 4
Nielsen K, Hjortdal J, Aagaard Nohr E, Ehlers N. Incidence and prevalence of keratoconus in Denmark. Acta Ophthalmol Scand 2007;85:890-2.  Back to cited text no. 5
Ziaei H, Jafarinasab MR, Javadi MA, Karimian F, Poorsalman H, Mahdavi M, et al. Epidemiology of keratoconus in an Iranian population. Cornea 2012;31:1044-7.  Back to cited text no. 6
Zadnik K, Barr JT. Keratoconus. In: Efron N, editor. Contact Lens Practice. New Delhi: Butterworth-Heinemann; 2002. p. 301-12.  Back to cited text no. 7
Krachmer JH, Feder RS, Belin MW. Keratoconus and related noninflammatory corneal thinning disorders. Surv Ophthalmol 1984;28:293-322.  Back to cited text no. 8
Ertan A, Muftuoglu O. Keratoconus clinical findings according to different age and gender groups. Cornea 2008;27:1109-13.  Back to cited text no. 9
Kennedy RH, Bourne WM, Dyer JA. A 48-year clinical and epidemiologic study of keratoconus. Am J Ophthalmol 1986;101:267-73.  Back to cited text no. 10
Wilson SE, Lin DT, Klyce SD. Corneal topography of keratoconus. Cornea 1991;10:2-8.  Back to cited text no. 11
Kok YO, Tan GF, Loon SC. Review: Keratoconus in Asia. Cornea 2012;31:581-93.  Back to cited text no. 12
Georgiou T, Funnell CL, Cassels-Brown A, O'Conor R. Influence of ethnic origin on the incidence of keratoconus and associated atopic disease in Asians and white patients. Eye (Lond) 2004;18:379-83.  Back to cited text no. 13
Zadnik K, Barr JT, Edrington TB, Everett DF, Jameson M, McMahon TT, et al. Baseline findings in the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) study. Invest Ophthalmol Vis Sci 1998;39:2537-46.  Back to cited text no. 14
Wagner H, Barr JT, Zadnik K. Collaborative Longitudinal Evaluation of Keratoconus (CLEK) study: Methods and findings to date. Cont Lens Anterior Eye 2007;30:223-32.  Back to cited text no. 15
Lim N, Vogt U. Characteristics and functional outcomes of 130 patients with keratoconus attending a specialist contact lens clinic. Eye (Lond) 2002;16:54-9.  Back to cited text no. 16
Khor WB, Wei RH, Lim L, Chan CM, Tan DT. Keratoconus in Asians: Demographics, clinical characteristics and visual function in a hospital-based population. Clin Experiment Ophthalmol 2011;39:299-307.  Back to cited text no. 17
Mohd-Ali B, Abdu M, Yaw CY, Mohidin N. Clinical characteristics of keratoconus patients in Malaysia: A review from a cornea specialist center.J Optom2012;5:38-42.  Back to cited text no. 18
Owens H, Gamble G. A profile of keratoconus in New Zealand. Cornea 2003;22:122-5.  Back to cited text no. 19
Fink BA, Wagner H, Steger-May K, Rosenstiel C, Roediger T, McMahon TT, et al. Differences in keratoconus as a function of gender. Am J Ophthalmol 2005;140:459-68.  Back to cited text no. 20
Agrawal VB. Characteristics of keratoconus patients at a tertiary eye center in India. J Ophthalmic Vis Res 2011;6:87-91.  Back to cited text no. 21
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  [Figure 1], [Figure 2], [Figure 3], [Figure 4]

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5]

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