ORIGINAL ARTICLE Year : 2023  |  Volume : 37  |  Issue : 1  |  Page : 6-9

The use of occlusive contact lenses after failure of conventional for treatment of amblyopia

Mohammad S Abu-Ain1, Patrick Watts2
1 Department of Special Surgeries, Faculty of Medicine, The Hashemite University, Zarqa, Jordan; Department of Ophthalmology, University Hospital of Wales, Cardiff, Wales
2 Department of Ophthalmology, University Hospital of Wales, Cardiff, Wales

Date of Submission08-Feb-2021Date of Decision30-Jun-2022Date of Acceptance26-Jul-2022Date of Web Publication22-Nov-2022

Correspondence Address:
Mohammad S Abu-Ain
Department of Special Surgeries, Faculty of Medicine, The Hashemite University, P.O. Box 330127, Zarqa 13133

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/sjopt.sjopt_25_21

PURPOSE: The purpose of this study was to evaluate the usefulness and assess the risks associated with occlusive contact lenses (OCLs) use to treat refractory amblyopia in children who failed the conventional amblyopia treatment with patching and atropine penalization.
METHODS: This was a retrospective case series of all children treated with an OCL in the sound eye over an 8-year period. Data were collected on the age, gender, and type of amblyopia, previous treatment received, and its duration. The compliance, tolerance, and adverse effects of OCL were recorded.
RESULTS: There were 12 patients of which 10 were male. The mean age at the time of OCL use was 47.3 months (range 26–86 months). Anisometropic amblyopia was present in 1, combined anisometropia and strabismus in 3, strabismic amblyopia in 5, and stimulus deprivation amblyopia in 3. All patients had conventional patching for a mean period of 14 months, followed by atropine penalization in nine patients for a mean period of 4 months. The mean duration of OCL use ranged from 2 weeks to 6 months. There were nine patients with visual improvement (75%). The mean improvement seen was 0.4 log of the minimum angle of resolution. There was no occlusion amblyopia. Four patients had conjunctivitis; one had a peripheral corneal abrasion.
CONCLUSION: The OCL is a useful adjunct in the treatment of amblyopia that is refractory to conventional treatment. The side effect profile is acceptable, but patients require close monitoring.

Keywords: Amblyopia, conventional amblyopia treatment, occlusive contact lens

How to cite this article:
Abu-Ain MS, Watts P. The use of occlusive contact lenses after failure of conventional for treatment of amblyopia. Saudi J Ophthalmol 2023;37:6-9
  Introduction 

Amblyopia is a leading cause of monocular visual impairment in children and young adults.[1] The prevalence of amblyopia reported varies between 1.8% in preschool children and 5.3% of ophthalmic patients.[2],[3] Successful conventional treatment of amblyopia with patching is dependent on the compliance of a child and his/her carers. The use of atropine in the sound eye is well established either as a first-line treatment or when patching fails or is not acceptable to the child or his/her carers.[1],[4],[5]

When the treatment of amblyopia below the age of 7 years is refractory to either patching or atropine, other methods have been used to achieve occlusion of the sound eye. These include ptosis induced by chemodenervation and the use of occlusive contact lenses (OCLs).[6],[7] In addition, more extreme measures of a sutured occluder to the brow and cheek have been reported to improve visual acuity (VA) in children where compliance to conventional methods has failed.[8]

The use of OCL in the treatment of amblyopia has reported not only improvement in VA but also improvement in subsequent occlusion compliance.[6],[9] In this study, we evaluate the effectiveness and complications of the use of OCL in the treatment of refractory amblyopia that has failed to improve with either patching or the use of atropine in the sound eye.

  Methods 

Children treated for amblyopia with OCLs were identified from a pediatric database over an 8-year period at the University Hospital of Wales. The study was considered as a service evaluation, and hence, ethical approval was not required; however, the principles of the Declaration of Helsinki were adhered to.

Children aged between 2 and 7 years whose VA failed to improve with patching and/or atropinization of the sound eye were offered treatment with an OCL (no combined atropine–optical penalization was tried in this cohort). Data were collected on the type of amblyopia, the age at the time of use of occlusive lenses, the gender, the duration of previous patching and atropine use, the VA pre- and post-contact lens use, and any complications encountered.

A hydrogel extended wear contact lens with a Diffusionskonstante value of 43 and water content of 75% (Contaflex, David Thomas™, Northampton, UK) with a power of +10 was used. The lens was 12 mm in diameter and had 9 mm occlusive zone, with a 7.4 base curve. The lens was prescribed for continuous wear and was inserted in the clinic. Prophylactic use of preservative-free chloramphenicol drops (twice daily) was used in the latter cases to prevent an infection [[Table 1]; cases 4, 6, 7, 10 and 11]]. Those children who continued to use contact lens after 8 weeks had a gap of 1 week before restarting contact lens use for every 8 weeks of continuous wear.

The patients were followed up every week to assess the improvement and monitor for occlusion amblyopia. The carers were instructed to report back any unusual signs or symptoms of redness, irritation, and watering and to make sure they observed the occlusive zone was centered over the eye. Otherwise, the contact lens was removed, cleaned, and re-inserted in the clinic every 4 weeks of continuous wear.

  Results 

There were 12 children identified during the study period. At the time of the use of OCL, the mean age was 47.3 ± 19 months (median 38 months; range 26–86 months). There were 10 males and the type of amblyopia was anisometropic in 1 case, mixed anisometropia and strabismus in 3 cases, strabismic in 6 cases (one with a third nerve palsy), and sensory due to unilateral cataract surgery with intraocular lens in 2 cases [Table 1].

The anisometropic, mixed, and strabismic groups were treated initially with best refractive correction until VA is stable followed by patching. All patients had previous conventional treatment of amblyopia with patch occlusion. The mean duration of patching was 14 months (range 5–24 months), with the patching time ranging from 2 h daily up to 12 h daily depending on the age of the patient and density of amblyopia. There was no improvement in the amblyopia as a result of patching which may have been due to poor compliance by child or parents/carers or patch intolerance. Poor compliance was noted in all cases and was defined as repeated failure to comply with hours of patching prescribed.

Nine of the patients had further treatment with atropine penalization of the sound eye. None of the patients demonstrated any visual improvement in the amblyopic eye. The mean duration of atropinization was 4 months (range 2–9 months).

All children involved were wearing their refractive error correction prescription during the treatment trial which was updated 6 monthly. The mean duration of OCL use was 9.3 weeks (median 4 weeks; range from 2 to 24 weeks). The total duration of contact lens wear was dictated by the VA improvement; if there was no improvement, the contact lens was discontinued at 8 weeks; however, one patient discontinued OCL wear after 2 weeks (Patient 11). Three patients, one with mixed amblyopia (Patient 3), another with strabismic amblyopia (Patient 4), and a third with visual deprivation amblyopia due a unilateral cataract surgery (Patient 7), have their treatment continued for 24 weeks.

The mean pretreatment (with OCL) VA of the amblyopic eye was 1.38 log of the minimum angle of resolution (LogMAR) (range 0.6–1.9 LogMAR). Improvement in VA of the amblyopic eye after OCL use was noticed in nine patients (75%), no change in vision noticed in two patients, and one patient has worsening of his vision in his amblyopic eye. There was no occlusion amblyopia induced in the occluded eye in any of the patients after cessation of treatment. The mean posttreatment VA was 0.99 LogMAR (range 0.1–1.7 LogMAR). The average improvement was 0.4 LogMAR.

The patient who has worsening of his vision had the OCL used for 2 months, and there was no reason to explain this worsening of vision in the amblyopic eye. The two patients who had no change in their VA with the use of the OCL were treated for 8 and 24 weeks, respectively.

The complications related to OCL use were infection in 5 patients; conjunctivitis with discharge in 4 patients, peripheral keratitis in 1 patient, which was treated successfully with topical levofloxacin. Hence, the duration of OCL use in this subgroup (Patients 5, 8, 9, and 12) was limited to an average of 3.25 weeks excluding Patient 3 where the infection occurred later in the course of treatment (duration of OCL use was 24 weeks).

Other issues seen with the use of OCL included that two patients reported being able to see through the contact lens after 2 weeks of wear as some of the pigments in the contact lens had faded. These patients had OCLs without the + 10 power. Another issue was that 4 of the younger patients (Patients 1, 2, 3, and 5) learned to rub the contact lens out of their visual axis.

  Discussion 

Children who either noncompliant or refractory to patching and atropine penalization can be offered OCLs in an attempt to improve VA. In this study, 75% of the patients had some improvement in VA with a mean improvement of 0.4 LogMAR. One patient improved from 0.6 to 0.1 LogMAR, who had previously failed patch occlusion and atropine penalization. There was no case of occlusion amblyopia. There were 33% (4 children) who developed conjunctivitis and one patient developed peripheral keratitis, which was successfully treated with no residual scarring. As the OCL use was discontinued after developing an infection, this subgroup of patients had shorter duration of OCL use and limited improvement in their amblyopia (excluding Patient 3 where the infection developed later in the treatment course).

Eustis and Chamberlain[6] reported 92% of children who improved at least 1 line of acuity with 36% improving greater or equal to 2 octaves. The study reports a high rate of recidivism of amblyopia when occlusion was stopped. These results appear to achieve better results than our study; however, the group of children was not comparable as starting VA was significantly better even though the average age of the children was older. In addition, the study used a larger lens diameter with a bigger occlusive zone and a few number of lenses were used per patient. This may explain the difference in our results. A further study in older children showed a mean improvement of 0.52 LogMAR in 7 patients as a primary treatment to avoid the "social stigma" of patching in school-going children between 5.7 and 8.7 years, and the average duration of wear was 9 months with no complications.[10] This study was on naïve older children who had no previous patching or atropine penalization. Our study differs from this study as we had a younger patient population who had amblyopia refractory to patching or atropine penalization. Hence, it is possible that children naïve to any amblyopia treatment would achieve better visual results with good compliance.

Joslin et al.[9] reported the use of part-time OCL in a group of children with predominantly visual deprivation amblyopia from unilateral aphakia. In this series, there was 30% who wore the lens successfully and further 30% had partial success. The group of children differs from our study in the type of amblyopia, the age of the patients, and the type of occlusion prescribed which was part time and relied on parents inserting and removing the lens. This study does demonstrate that vision can be improved in a third of children with OCL where all other methods have failed.

Our study presents results in the real world and demonstrated a high proportion of children who improved when conventional methods failed. The patients in our study had only one occlusive lens; therefore, when the child developed an infection or rubbed the lenses out, this represented the end of their treatment with OCLs; hence, the provision of more occlusive lens may improve the visual results. Further, the larger lens diameter and larger occlusive zone used in previous studies may allow better retention and remain to be tested. Our study has all the drawbacks of a retrospective study with a small sample size and heterogeneous types of amblyopia.

Further research on the type of contact lens used shows that OCL could be tailored to the density of amblyopia, which allows some peripheral fusion and binocularity to occur during the use of the occlusive lens.[11] The use of OCLs on naïve amblyopic subjects, which may achieve better visual results in a short occlusive period, remains to be tested. The cost of multiple contact lenses may be a factor that limits its use in routine practice.

  Conclusion 

Our experience with the use of OCLs in patients where conventional methods of treatment have failed demonstrates that it provides useful visual improvements in some patients. This study provides pilot data for further prospective work on a large more homogenous sample of similar types of amblyopia with the use of a larger lens with a bigger occlusive zone and regular use of preservative-free antibiotics.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 

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  [Table 1]