Elsevier

Ophthalmology

Volume 111, Issue 3, March 2004, Pages 440-446
Ophthalmology

Original article
Longitudinal study of the normal eyes in unilateral keratoconus patients

https://doi.org/10.1016/j.ophtha.2003.06.020Get rights and content

Abstract

Purpose

To determine the rate at which clinically normal eyes in unilateral keratoconus (KC) patients progress to KC and to identify the risk factors that might predict the development of KC in a longitudinal study.

Design

Prospective observational study.

Participants

We recruited 778 patients with KC and 252 normal controls in Los Angeles, California. One hundred sixteen of 778 patients (14.9%) were diagnosed with clinically unilateral KC at baseline.

Methods

Both eyes of these unilateral KC patients were examined at baseline, and 85 patients were followed up with clinical evaluation and videokeratography for a period ranging from 6 months to 8 years.

Main outcome measures

Progression to clinical KC from previously normal fellow eyes. Quantitative and qualitative videokeratography variables, contact lens wear, and demographic variables were analyzed as potential predictive factors for this progression.

Results

During the follow-up period, 30 of 85 (35.3%) clinically normal fellow eyes had KC develop, and 25 of these 30 (83.3%) had KC develop within the first 6 years after the initial KC diagnosis. By use of the time period from the patients' first diagnosis of unilateral KC to the end of the follow-up period (range, 6 months–41 years), the median time (estimated from the survival analysis) to the development of KC was 16.7 years (95% confidence interval, 11.34, 28.91). Fellow eyes with higher inferior-superior dioptric asymmetry value (I-S) or KC percentage index (logKISA) values had higher risk for KC developing (I-S, risk ratio [RR] = 1.348, P = 0.022; log(KISA), RR = 4.245, P = 0.003). Asymmetric patterns also showed an increased risk for KC developing (P = 0.03), especially the asymmetric bowtie with skewed radial axes (AB/SRAX) pattern.

Conclusions

Approximately 50% of clinically normal fellow eyes will progress to KC within 16 years. The greatest risk is during the first 6 years of the onset. Quantitative indices (I-S and KISA values) and qualitative patterns (AB/SRAX) might predict this progression.

Section snippets

Subjects

We prospectively recruited 778 patients with clinically diagnosed KC and 252 normal patients as controls as a part of a longitudinal videokeratography and genetic study at the Cedars-Sinai Medical Center, Los Angeles, California. Institutional Review Board/Ethics Committee approval was obtained.

The diagnosis of KC was made on the basis of clinical examination. Any patient who had 1 or more of the following clinical signs with no other pathology was classified as having KC: obvious corneal

Comparison between normal fellow eyes of KC patients and normal controls

The mean age at baseline in the unilateral KC patient group was lower than that in normal controls (34.28±12.24 vs. 38.81±12.18; P<0.001). There were more males in the unilateral KC patient group (62.9%) than in the controls (40.5%; P<0.0001). No significant difference in race was found between the 2 groups.

The clinically normal fellow eyes had higher I-S and logKISA values compared with normal controls at baseline (Table 1).

Estimated median time for the fellow eyes developing KC

Among 85 patients with at least 2 visits, the years of follow-up

Discussion

In this longitudinal study, we have provided new information regarding: (1) the incidence and duration of the progression of clinically normal fellow eyes to development of KC; (2) the predictive factors for developing KC in the normal eye; and (3) the distribution of qualitative and quantitative factors in normal eyes of KC patients.

As previously discussed, KC is most commonly bilateral, and the prevalence and incidence of unilateral KC varies, depending on the methods used for diagnosis. By

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  • Cited by (0)

    Manuscript no. 230075.

    Supported by the National Eye Institute (grant no.: NEI 09052, GCRC), the National Institutes of Health (grant no.: NIH 50091-06), the Eye Birth Defects Research Foundation Inc., and Center for Keratoconus.

    The authors have no financial interest in the Topographic Modeling System (Computed Anatomy, Inc., New York, NY).

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