Functional spasm of accommodation: Changes on scheimpflug imaging.

Spasm of accommodation is a rare condition characterized by a sudden increase in myopia. It can occur in emmetropes, hypermetropes and myopes. All the physiological changes that occur in normal accommodation are exaggerated. Mostly the cause is functional disorder and the condition gradually improves. We hereby present the changes occurring in spasm of accommodation as seen on Scheimpflug imaging.

Introduction

Spasm of accommodation is characterized by intermittent and usually painful convergence, accommodation, and miosis in varying combinations with variable amount of time.[1] Various etiologies have been implicated, including functional spasm of oculo-motor muscle, hysterical convergence spasm and emotional distress.[2] The excessive accommodative tone usually causes pseudomyopia.[3] We herein report scheimpflug imaging in a patient with spasm of accommodation.

Case Report

A 17-year-old girl complained of sudden onset blurring of vision in both eyes following prolonged reading under a dim light. It was associated with mild headache and eye strain. She was a known case of myopia. Her refractive error was –2 diopters in both eyes. Her records showed that her refractive error increased to –4 dioptre sphere on the day of her complaint and she was prescribed spectacles on the same day. She was on salbutamol inhaler for bronchial asthma.

At presentation to us on the third day of her symptoms, visual acuity was 6/36 and 6/24 in the right and the left eye with –4 dioptre spherical correction which she was wearing in both eyes. BCVA (Best corrected visual acuity) was 6/6 with manifest refraction of –7 diopter sphere OD and – 7.5/–0.5 × 70 OS. Anterior segment examination revealed miosis, shallow anterior chamber in both eyes. Intra-ocular pressure on applanation tonometry was 14 and 16 mmHg in right and left eye, respectively. On Pentacam examination after dilatation with phenylepherine 5% drops, the anterior chamber depth was 1.64 mm OD and 1.57 mm OS. The crystalline lens thickness was 4.01 mm in the right eye and 4 mm in the left eye and the distance between the cornea and posterior pole of the lens was 5.65 mm OD and 5.57 mm OS [Figure 1a and 1b]. Cycloplegic refraction under cyclopentolate 1% done 1 day later showed –1.5 dioptre sphere in the right and –1.75 dioptre sphere in the left eye and visual acuity of 6/6 OU. At this time scheimpflug imaging showed an anterior chamber depth of 2.98 mm OD and 2.95 mm OS with a lens thickness of 3.7 mm in the right eye and 3.62 mm in the left eye and the distance between the cornea and posterior pole of the lens was 6.68 mm OD and 6.57 mm OS [Figure 2a and 2b]. No supraciliary effusion could be documented on ultrasound biomicroscope. A diagnosis of accommodative spasm was thus made clinically and morphological changes were documented by pentacam. The patient was put on cyclopentolate 1% drops once a day.

Figure 1

(a) Scheimpflug image of the right eye during accommodative spasm after dilatation with phenylepherine 5% drops objectively reveals shall anterior chamber along with lenticular parameters. (b) Scheimpflug image of the left eye showing a similar picture

Figure 2

(a) Scheimpflug image of right eye after dilatation with cyclopentolate 1% drops. Note the increase in the anterior chamber depth with a decrease in lens thickness and posterior movement of the crystalline lens. (b) Scheimpflug image of the left eye with similar findings

Discussion

Accommodative spasm is a condition where there is an involuntary, sustained accommodation in the absence of an accommodative stimulus. The anterior lens becomes more sharply curved, moving closer to the cornea.[4] Baikoff et al. analyzed the anterior segment changes during accommodation using optical coherence tomography (OCT).[5] They found that the anterior pole of crystalline lens moves forward during accommodation and there is a linear relationship between this movement and anterior radius of curvature. Accordingly the posterior curvature decreased proportionally. Controversy still exists as to the movement of the posterior lenticular surface during accommodation. Recent study by Strenk et al. reported no movement of the posterior lenticular surface during accommodation whereas Bolz et al. have showed posterior movement.[67] Koretz et al. showed that in young adults the posterior lens surface may tend to move posteriorly a short distance as well, so that total anterior segment length may increase slightly whereas in adults this surface moves forward adding to the decrease in anterior chamber depth.[4] Tsorbatzoglou et al. found by partial coherence interferomtery that the decrease in ACD was greater than the increase in anterior segment length (ASL) and thus hypothesized that the crystalline lens move forward simultaneously during accommodation.[8] Dubbelman et al. found significant anterior movement of the human lens during accommodation.[9] In our young patient we observed forward movement of the posterior lenticular surface as well. It may be hypothesized that this anterior movement of the posterior surface of the crystalline lens occurs in accommodative spasm which contributes to the increase in accommodative amplitude. A myopic patient will appear to be more myopic, a hyperopic patient will appear to be less hyperopic and an emmetropic patient will appear to be a myopic.

Scheimpflug imaging is an important tool in objectively quantifying the changes in accommodative spasm.