Management of ocular aberration and convergence excess after laser-assisted in situ keratomileusis with vision therapy

Abstract

Decentered ablation after laser-assisted in situ keratomileusis (LASIK) and a large pupil size can cause higher-order aberrations, leading to glare and halos [1, 2]. In this case report, we present a noninvasive approach that normalizes accommodative and binocular functions, thereby regulating pupil size and ocular aberrations.

A 27-year-old male computer science student presented to our hospital with diminished vision in both eyes, frontal headache, and the appearance of glare and halos around lights, which began 1 month after femtosecond (FS-200) LASIK. Following surgery to correct a −5.75 diopter sphere (DS) error in both eyes, the patient reported ongoing visual discomfort for 3 months, necessitating the use of glasses. He also reported that his discomfort persisted even after using 0.4% hydroxypropyl methylcellulose eye drops three times daily for dry eyes. However, he did not experience discomfort during 12–14 h of daily computer use. Consequently, he visited our hospital for a second opinion.

During the optometric examination, uncorrected visual acuity (VA) was 20/80 and 20/30 in the right eye (RE) and 20/30 in the left eye (LE). With his current glasses, the VA improved to 20/30, with a prescription of −1.25 DS in the RE and −1.00 DS in the LE. Upon manifest refraction, VA further improved to 20/25 with −1.50 DS in the RE and −1.25 DS in the LE. Both the anterior and posterior segments appeared normal. The Rosenbaum pupillometry card read the pupil size measured to be approximately 7 mm. The insignificant misalignment in the ablation zone detected by the Oculus Pentacam (Figure 1) invalidated the diagnosis of myopic regression post-LASIK surgery. The ray-tracing aberrometer (Figure 2, Table 1) detected notable ocular aberrations, including increased internal defocus and larger pupil size. Cycloplegic refraction with 1% cyclopentolate solution revealed a refractive error of −1.00 DS in the RE and −0.75 DS in the LE. The patient was advised to return for a post-mydriatic test after 2 days given the 0.50 DS discrepancy between manifest and cycloplegic refractions.

A final spectacle prescription was recommended in both eyes with a −0.75 DS following binocular balancing, achieving VA of 20/20. Following a 2-week adaptation period with the new prescription, an orthoptic evaluation was conducted. The patient was diagnosed with a convergence excess (Table 2) associated with a high accommodative convergence/accommodation (AC/A) ratio (10:1). The reported Convergence Insufficiency Symptom Survey score was 34. Initially, it was recommended to begin with +1 sphere bifocal spectacles, followed by in-office therapy. However, the patient declined bifocal glasses and opted for vision therapy as the primary treatment.

The vision therapy program was designed to be performed 3 days a week, for 45–60 min, encompassing 24 sessions and 30 min of home therapy (Table 3). The therapy progressed with improvements in both monocular and binocular visual skills. The main goal of the program was to educate patients about the awareness, sensations, and skills required to effectively diverge. Subsequently, the aim turned to voluntarily control the convergence and divergence at varying distances, normalizing the fusional vergence and accommodative amplitudes [3].

Following 24 in-office therapy sessions over 2 months, orthoptic reassessment showed that both accommodative and vergence parameters were within normal limits. Distance VA improved to 20/20 with −0.50 DS for the RE and −0.25 DS for the LE. The esophoria frequency significantly decreased to 2∆, and accommodation amplitude increased by 3.40 diopter. The pupil diameter was measured at 5.00 mm. Ray-tracing aberrometer analysis revealed a significant reduction in ocular aberrations, including the total root mean square (RMS) and both lower-order and higher-order aberrations (Figure 3, Table 1).

The patient, with no major complaints, revisited the clinic 3 months later with distance VA at 20/25 and 20/20 for each eye (Table 2). Orthoptic reassessment showed that the treatment was effective and did not induce headache, minimal glare, or halos during nighttime. The symptom score was further reduced to 14.

The literature review indicates that residual refractive errors following LASIK can be attributed to inaccurate manifest refraction or errors in data entry. However, scant preoperative data do not support postoperative refractive errors. Aligning the ablation zone accurately with the visual axis is vital for obtaining an optimal post-LASIK visual outcome. Ablation that is decentered by >0.3 mm can lead to higher-order aberrations, astigmatism, and coma [4]. In our study, minimal decentered ablation might have caused visual discomfort, but the Pentacam results were insignificant.

In cases in which a large pupil size and small-zone myopic ablation are simultaneously present, the peripheral rays interact with the steeper corneal region outside the ablation zone, leading to spherical aberrations [5]. Consequently, a larger pupil size (7 mm) may intensify higher-order aberrations, particularly spherical aberrations. Both lower-order and higher-order aberrations were detected using the ray-tracing aberrometer results. The total RMS for normal eyes is ≤0.30 μm, yet the total RMS of the patient was 10 times greater than the expected. Hence, the decision to perform an orthoptic evaluation at this point was crucial. Convergence excess, often seen in individuals who perform extended near-work activities with an AC/A ratio of >7:1 [3], could have predated the surgery in this patient, who was a frequent computer user [6, 7]. However, the lack of asthenopic symptoms has masked its detection.

Following the recommendations [3, 8], in-office therapy was chosen to manage binocular dysfunction and its associated symptoms. The convergence and accommodative functions showed significant improvement. Synkinesis of convergence, accommodation, and pupillary constriction is necessary to preserve the near-triad. Aberrometry is therefore crucial for assessing changes in pupil size, accommodation [9], and higher-order aberration [10] before and after therapy. Consequently, the patient reported enhanced depth of field and focus, absence of headache, and decreased glare, halos, and refractive error.

This case report highlights the effect of vision therapy in managing convergence excess after LASIK surgery, diminishing ocular aberrations, enhancing visual quality, and alleviating headache. The current study emphasizes the importance of thorough preoperative assessments and additional research to confirm the effectiveness of vision therapy for ocular aberrations after LASIK.

Prithwis Manna: Conceptualization (lead); investigation (equal); methodology (equal); visualization (equal); writing—original draft (lead). Sourav Karmakar: Methodology (lead); supervision (equal); visualization (equal); writing—review & editing (equal). Animesh Mondal: Data curation (equal); formal analysis (equal); methodology (equal); writing—review & editing (equal). Puja Sarbajna: Formal analysis (equal); investigation (equal); supervision (lead); writing—review & editing (equal). Rikta Paul: Formal analysis (equal); supervision (supporting); writing—review & editing (equal). Mahesh Mudi: Investigation (equal); writing—review & editing (equal).

The authors do not have any conflicts of interest or funding sources to declare.

The need for ethical approval was waived off by the Narayana Nethralaya Ethics Committee for the case reports.

Informed consent to participate and publication was obtained from the patient prior to submission.

The authors declare no competing interests relevant to the content of this article.