CLINICAL QUIZ

Year : 2017  |  Volume : 10  |  Issue : 1  |  Page : 56

A case of unilateral non-dilating small pupil

Pratik Yogesh Doshi, Pradnya Jayant Kamat, Ugam P. S Usgaonkar
Department of Ophthalmology, Goa Medical College, Bambolim, Goa, India

Correspondence Address:
Pratik Yogesh Doshi
Department of Ophthalmology, Goa Medical College, Bambolim - 403 202, Goa
India

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/0974-620X.200700

Figure 1: Right pupil under diffuse illumination with patient looking at distance Click here to view

Figure 2: Left pupil under diffuse illumination with patient looking at distance Click here to view

Questions

1. Describe the findings seen in the right eye [Figure 1]?
2. What is the condition called as?
3. Mention some other conditions which can present similarly?
4. Mention the associated features of this condition?
5. How do we manage and monitor such patients?

Answers

1. Figure shows right pupil under diffuse illumination with patient looking at distance, which is one millimeter in size and has a slit-like miotic appearance. The iris is brown in colour, however, the iris stroma is hypoplastic with poor development of collarettes and crypts, and lacks the normal circular contraction furrows
2. This condition has been termed as congenital miosis/microcoria (MCOR). MCOR is a developmental anomaly which has been reported previously from many parts of the world. It has been phenotypically defined as pupils of less than 2 mm diameter when the subject is looking at a distant object. Mydriatics, such as 1.25% epinephrine, 5% neosynephrine, 5% tyramine, and 1% atropine are unable to dilate the pupil fully. MCOR is a defect of intermediate filaments in the terminal fetal stages of differentiation of the anterior pigmented epithelial cell of the iris. This results in the absence of myofilaments and consequent failure of development of a functional dilator pupil muscle. In MCOR, the iris stroma is hypoplastic with poor development of collarettes and crypts, and lacks circular contraction folds, and the dilator myoepithelium is deranged, leading to absence of the contractile processes. Few reports postulate that there is lack of myofilaments and desmin in the stromal cytoplasmic processes of the anterior pigmented cells of the iris in MCOR. On histopathology, in the trabecular meshwork, thick endothelial meshwork with many layers of cells embedded in prominent extracellular materials has been seen on the canal side. On the anterior chamber side, several layers of trabecular sheet have been reported. These findings indicate underdevelopment of the trabecular meshwork. Sporadic as well as autosomal dominant/recessive hereditarily transmitted cases of congenital microcoria have been reported. Linkage analysis has shown loci of the disorder most likely to be located on 13q31-q32. Many familial pedigrees have been genetically analysed most notably a French and an Asian family.
3. Differential diagnosis of this condition would include:
   
   
   • Chronic anterior uveitis with posterior synchiae formation. It is ruled out due to absence of any other tell-tale signs of uveitis
   • Iatrogenic instillation of parasympathomimetic drugs such as pilocarpine which can be accidentally instilled or therapeutically instilled for treatment of conditions like juvenile glaucoma.
   
   
   
4. Associations mentioned in the literature with microcoria are goniodysgenesis, juvenile or late onset glaucoma and myopia. There are no systemic associations known for this condition.
5. No treatment is usually indicated for this condition. Sectoral iridectomy might be very rarely required to increase the pupillary size. Patient, however, needs to follow up regularly for intra-ocular pressure (IOP) measurement, optic disc examinations and automated perimetry to assess any development of associated glaucoma.