Objective study of accommodation in keratoconus

Background. Keratoconus (KC) is the most commonly diagnosed corneal ectasia among young adults today. The asymmetric process of progression of the KС determines the occurrence of anisometropia, which in a compartment with increased audience and the absence of proper optical correction leads to a violation of the accommodation function that has not previously studied with this pathology.

Purpose: to study the work of accommodation using an objective method of computer accommodation in young people with newly diagnosed keratoconus (КC).

Material and methods. Thirty (60 eyes) people were included in the study, of which 15 people (30 eyes) formed the main group and 15 (30 eyes) formed the control group. The main group consisted of patients with newly diagnosed bilateral KC: 15 eyes – stage 1, 13 eyes – stage 2, 2 eyes – stage 3 of the disease). Patients of the control group had a history of mild myopic astigmatism of the direct type. The average age of the patients was 23.5 ± 3.1 years. All patients underwent standard ophthalmological examination: autorefkeratometry, visometry and biomicroscopy. In addition, the main keratometric parameters of the cornea were examined using the Scheimpflug analyzer Pentacam. An objective assessment of the indicators of the accommodative ability of the eye was carried out using computer accommodation on the Righton Speedy-I device. The statistical processing was carried out in the IBM SPSS Statistics 23 program.

Results. The results of the analysis of accommodograms in both groups demonstrate the predominance of disorders of the ciliary muscle, which manifested themselves in the form of habitual-excessive accommodation tension (HEAT) and accommodative asthenopia of a spasmodic nature. In the control group, in 76% of cases, there was a pattern of excessive accommodative response by the type of HEAT. The state of accommodation in the group with KC in 68% of cases was characterized by an excessive and unbalanced accommodative response, with an unstable course of the curve. The average indicator and the curve of the accommodogram significantly exceeded the indicators of the control group, which proves an unstable state of accommodation in KC. In comparison with the control group, a decrease in coefficient of growth of the accommodogram (CR) by 37% (p < 0.05) was recorded, confirming the absence of a smooth and increasing course of the accommodative response following the stimulus. Analysis of high-frequency the coefficient of microfluctuation (CMF) demonstrated a 10% increase in the work of the ciliary muscle (p < 0.001). The correlative dependence of these parameters with visometry and autorefractometry data has been established.

Conclusion. The objective method of accommodation assessment revealed abnormalities of ciliary muscle functioning in patients with a first-time diagnosis of KC, which correspond to the phenomena of spasmodic accommodative asthenopia. The established correlation between CR and CMF with the data of visometry and autorefractometry suggests a potential improvement of accommodation functioning under conditions of optical correction with contact lenses.

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