FP618 : Unilateral Congenital Nasolacrimal Duct Obstruction (Cnldo) Presents with Refractive Errors (RE).

Dr. Anurag Shandil, Dr. Zia Chaudhuri, Dr. Om Prakash

AnuragShandil (S19529)¹, Om Prakash (O0538)¹, Zia Chaudhuri (C07237)^1,2

Lady Hardinge Medical College (LHMC) & Associated Hospitals ¹, University of Delhi, PGIMER, Dr RML Hospital, ²New Delhi, India (Study conducted at LHMC,)

Introduction

A higher prevalence of anisometropia compared to the general population as also a significantly higher spherical equivalent in the eyes affected by CNLDO, if unilateral, has been reported in literature. ^{1 2}This has lead to the formulation of a hypothesis that there is some form of structural anomaly present on side of the CNLDO resulting in higher refractive errors and anisometropia. ² There have also been anecdotal reports that early syringing and probing results in lesser refractive errors including anisometropia on the side affected with CNLDO than if the condition resolved spontaneously. ³These reports have shown similar results in studies conducted in different ethnic populations all across the world in the past 5 years, be it Iran, Egypt, Turkey or the USA.^4-9A recent study from India confirms the presence of amblyogenic factors in about 14 to 20% children with CNLDO depending on standardized classifications of amblyogenic factors. ¹⁰ However, this study was cross-sectional and the authors reiterate the need for repeated follow-up evaluation of these patients to observe whether they develop amblyopia. ¹⁰All these results are in contradiction to a case control population based study reported in Scotland in 1998 which stated that there was no difference in the incidence of amblyopia in CNLDO children compared with controls.¹¹ Also, there was no difference in refractive errors observed in the affected unilateral eye with CNLDO versus the normal fellow eye, no correlation between the refractive errors or astigmatism present with the CNLDO as also no correlation of strabismus with CNLDO, as reported in this study. ¹¹

We performed an audit of refractive error evaluation in 128 children (82 males) with unilateral and bilateral CNLDO who presented to our institution for management of epiphora.

Materials and Methods

 128 children of average age 8 ± 9.7 months with unilateral and bilateral CNLDO were prospectively evaluated for a complete ophthalmic examination including cycloplegic refraction over a period of 1 year at Lady Hardinge Medical College and Associated Kalawati Saran Children’s Hospital, University of Delhi, New Delhi, India and their results audited for best practices. The group comprised 93cases of unilateral CNLDO and 35 cases of bilateral CNLDO.

Results

93 children of average age 8.1 ± 7.4 months (57 males) had unilateral CNLDO (55 on the right side and 38 on the left side) while the remaining 35 children of average age 7.8 ± 14.2 months (23 males) had bilateral CNLDO.  The average age of presentation was similar in both groups (p=0.4). 20 of 93 children (21.5%) had anisometropia ≥ 1 D. 17 out of these 20 children were significantly more hypermetropiconthesideaffected by CNLDO than the other side (Average: 2 ± 1.2 DS versus 0.8 ± 1.3 DS, p=0.003). The remaining 3 children were significantly more myopic on the affected side as compared to the unaffected side (Average: -0.7± 0.7 DS versus 1.3 ± 1 DS, p=0.03).

29/73 children were completely isotropic in both eyes irrespective of the side of the CNLDO, the average refractive error being 0.7 ± 0.6 DS. 8 children were more myopic on the side of the CNLDO but the inter-eye refractive error difference was less than 1DS. The difference was insignificant (0.19± 0.9 DS versus 0.7 ± 1 DS, p=0.15). In the remaining 36 children, the patient demonstrated more hypermetropia on the side of the CNLDO than the fellow eye though the inter-eye refractive error difference was less than 1DS. The inter-eye hypermetropic refractive error difference though averaging less than 1DS, which classically is considered to be amblyopic was significantly different (1.± 0.8 DS versus 0.6 ± 0.8 DS, p=0.01).

Thus we observed that 53/93 children with CNLDO were more hypermetropic on the side of the CNLDO, 11 were more myopic while 29 were isometropic in both eyes. This difference in distribution was significant (chi², p<0.05). Out of these 53 children, 17 had an inter-eye difference of ≥ 1 D, conforming to standard criteria for defining anisometropia. However, even in the remaining 36 children, the refractive error on the side of the CNLDO remained significantly more hypermetropic than the fellow normal side, though the inter-eye refractive error difference was less than 1 DS.

In bilateral cases, the average age of presentation was 8.3 ± 15.1 months, which was similar to the average age of presentation for the unilateral cases.  3 of these 35 children had an inter-eye refractive error difference of more than 1D. In all these 3 cases, the right eye was more myopic than the left eye though the difference was not significant (1.2± 1.7 DS versus 2.2 ± 1.7 DS, p=0.26). In the remaining 32 children with bilateral CNLDO, the refractive correction in 17 children were isometric and averaged 1.2± 1 DS. All were hypermetropic but one child with bilateral refractive error of -1.5DS. If this child was removed from the average refractive error measurements, the mean refractive error of the remaining 16/17 children averaged 1.3± 0.9 DS. In the remaining 15 children, there were differences in the inter-eye refractive errors but all less than 1 DS. Again only 1 child was myopic in both eyes. The average refractive error was 0.63± 0.95 DS in the right eye and 0.65± 0.91 DS in the left eye. There was no significant difference in the overall refractive errors in the isometric group and the group with some inter-eye difference in refractive errors but less than 1 DS (p=0.48).

Discussion

We observed that hypermetropia was the most common refractive error associated with CNLDO, unilateral or bilateral. A large number of eyes with unilateral CNLDO demonstrated hypermetropic errors comprising spherical equivalents of hypermetropic astigmatism and hypermetropic spherical refractive errors, on the side of the CNLDO. The statistical difference between hypermetropia ipsilateral to the side of the CNLDO as compared to the fellow relatively myopic eye was significant even when the anisometropia between both eyes was less than 1 DS. Hypermetropia has significant potential to cause amblyopia, especially in children. This is similar to many other trans-ethnic studies performed on children with CNLDO, both prospectively and retrospectively. ^{2 4 5 7 9 12} A prospective study has also demonstrated that anisometropia, especially with the eye on the side of the CNLDO being more hypermetropic, is more common in untreated or unsuccessfully treated cases of CNLDO, leading to the formulation of a hypothesis that early management of CNLDO may aid amelioration of amblyogenic refractive errors, especially on the side of the CNLDO.¹However, another study emphasizes a different result by observing that early spontaneous resolution of the unilateral CNLDO begets higher hypermetropic anisometropia on the affected side than if a surgical correction is done later. ³

Amidst all the controversies of this association between CNLDO and refractive errors, especially if the CNLDO is unilateral, and the studies conducted to observe the effect of management of CNLDO on the natural history of the refractive errors, we aim to emphasize that there is a higher prevalence of amblyogenic refractive errors associated with unilateral CNLDO. Thus cycloplegic refraction should be performed in all children presenting with CNLDO, to prevent amblyogenic factors, if any that could later affect the visual acuity of the child. Bilateral CNLDO do not demonstrate a significant degree of differences in inter-eye refractive errors. This is similar to results demonstrated by other authors.

References

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