Orthoptic relevance of refractive correction in the phakic plane in unilateral high refractive errors in adults.

Sir,

Anisometropia is the condition in which the two eyes have unequal refractive power. A disparity in focus and the difference in clarity and size of the image on retina results in the impairment of fusion, often leading to strabismus.[1] Ocular deviation associated with anisometropia in adults is a common presentation in strabismus practice. Half-hearted efforts, if at all, are made for refractive correction before ocular alignment as it is largely believed that the deviation remains largely unchanged with use of glasses.[2]

Refractive correction by means other than spectacles has been known to significantly improve the quality of vision, enhance binocular functions, and also have a positive impact on ocular deviations.[34] We report a series of three patients proving the orthoptic relevance of surgical refractive correction in unilateral high refractive errors in young adults. The patients underwent surgery after informed consent.

The first patient was a 21-year-old male who presented to our strabismus clinic for cosmetic correction of the left exotropia (LXT) of 35 prism diopters (PD) [Figure 1a]. His uncorrected visual acuities (UCVA) were 0.0 (logarithm of the minimal angle of resolution) right eye (RE), and 1.34 left eye (LE). LE improved to 0.78 with + 8D sphere. A diagnosis of severe anisohypermetropic amblyopia LE with sensory LXT was made.[5] Surprisingly, a momentary control of XT was noted during subjective improvement which we attributed to improved visual acuity (VA) in LE and some preexisting binocularity. His control was even better (Newcastle control score 5/7) with contact lens (CL).[6] LE amblyopia therapy trial for 3 months showed no change in best-corrected VA (BCVA) or ocular deviation. Binocular functions could not be elicited by any standard test. As the patient desired permanent solution, refractive surgery followed by ocular alignment for residual deviation was planned. A clear lens extraction with multifocal intraocular lens (refractive-diffractive multifocal intraocular lens (IOL) (iDIFF, Intra Ocular Care Pvt. Ltd., Vadodara, Gujarat, India) implantation was done in LE, due to nonsuitability for implantable collamer lens (ICL) (anterior chamber depth = 2.432 mm).[7] Our decision to implant a multifocal IOL (MFIOL) was influenced by the patient's motivation to be spectacle free and possibly greater pseudo-accommodative effort.[8] Postoperatively, he was controlling the XT most of the times (NCS 5/7) [Figure 1b]. Postoperative UCVA and BCVA were 0.60. Binocular functions (160 s of arc on randot stereo test) were observed.[9] The patient was comfortable, and strabismus surgery was deferred.

Figure 1

(a) Preoperative photograph of case 1 showing exotropia (35 prism diopters). (b) Postoperative photograph of case 1 after clear lens extraction with multifocal intraocular lens implantation with control of exotropia

The second patient was a 20-year-old, male medical student who presented with difficulty in enjoying binocular vision while looking through a microscope. He had undergone a repair of corneal penetrating injury with lens aspiration and in the bag-IOL implantation LE 8 years back. His RE was emmetropic with a UCVA of 0.0. LE had a UCVA of 1.30 and BCVA of 0.30 with 8.0 D sphere. He had a leukoma adherans about 3.5 mm away from the center at 10 O' clock which made him intolerant to CL [Figure 2a]. He showed LE suppression with standard tests and desired binocular vision. Sulcoflex® (Rayner Intraocular Lenses Limited, East Sussex, United Kingdom) piggyback IOL was implanted, and the patient had a postoperative UCVA and BCVA of 0.3 [Figure 2b and c]. He demonstrated a binocularity of 100 s of arc on randot stereo test and a fusional range of − 4-+4 on the synoptophore.[8]

Figure 2

(a) Preoperative photograph of case 2 showing leukoma adherans. (b) Postoperative photographs of case 2 after piggyback intraocular lens implantation. (c) Postoperative photographs of case 2 after piggyback intraocular lens implantation

A 21-year-old female who came for cosmetic correction of the left XT was the third patient. Her UCVA was 1.0 RE and 1.5 LE. She had left XT of 30 PD with no variability or incomitance [Figure 3a]. BCVA of RE was 0.0 with − 4.5 D sphere; LE was 1.1 with − 20.0 D sphere. Both eyes had myopic degeneration with no staphyloma or treatable lesions. LE amblyopia therapy trial for 3 months caused no change in VA or ocular deviation. Simultaneous macular perception without fusion was present. Refractive correction followed by ocular alignment was planned. The patient underwent implantable Collamer lens (visian implantable Collamer lens (ICL) – STAAR Surgical, CA, USA) implantation simultaneously in both eyes (−6.5 D RE, −23.0 D LE). Postoperatively, the uncorrected VA improved to − 0.1 RE. The BCVA in LE was 0.6 (20/80) with − 0.75 D Sphere. She was orthophoric for distance and near with fusion with a limited range [Figure 3b].

Figure 3

(a) Preoperative photograph of case 3 (with contact lenses) showing left exotropia (30 prism diopters). (b) Postoperative photograph of case 3 after bilateral implantable Collamer lens implantation with control of exotropia

Tables 1 and 2 summarize the clinical details of the cases.

Table 1

Preoperative details with the intervention done

Table 2

Postoperative orthoptic details (12-week postprocedure)

These cases highlight the following points:

Refractive correction closer to the nodal point improves VA.[10] A clearer and lesser aniseiokonic image would stimulate and enhance binocularity

For high refractive errors, glasses create significant peripheral distortion. Surgical correction of the refractive error provides the patient with a larger distortion-free peripheral field and stronger stimulus for fusion[11]

A greater accommodative effort would help in controlling the XT. Greater pseudo-accommodative effort with MFIOL in the 1st case and enhanced effort by phakic IOL in the 3rd case would play a role.

These cases demonstrate orthoptic relevance of surgical refractive correction in unilateral high refractive errors in young adults as an essential part of their initial management.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.