Eye (1991) 5, 466-469

The Oval Pupil

H. S. DUA. N. J. WATSON. J. Y. FORRESTER Ahf'/'{/ecn

Summary The dynamics of pupillary dilation induced by Phenylephrine 10% and Cyclopento­ late 1 % have been examined by flash photography. A correlation between anterior chamber depth and the pupil shape on dilation with Phenylephrine Hydrochloride J00/r, is described. It is postulated that these pupillary dilation dynamics support a s)'mpathetic abnormality as a trigger for acute primary angle closure glaucoma.

The oval pupil is a common clinical sign in clinics after ocular and general examination acute prImary angle closure glaucoma had excluded conditions kno wn to affect (APACG ).1 APACG has been shown to occur ocular sympathetic function. Exclusion cri­ more commonly in patients with shallO\v teria included diabetes mellitus. glaucoma or anterior chambers.: The acute attack is pre­ ocular hypertension. previous ocular surgery cipitated by autonomic dysfunction and a (including extraocular muscle surgery). pre­ modification of physiological pupil block,: vious intraocular inflammation and topical During an attack of APACG the pupil is mid­ drug administration. The colour of the iris was dilated and vertically elongated. a preferen­ noted and the anterior chamber depth was tial dilation in the vertical meridian producing measured on a Haag Streit slit lamp using the the oval shape,' Oval or 'tadpole shaped' technique described by Smith,' A tine beam is pupils have also been reported in patients directed horizontally at the eye from 60°, Its with Horner's syndrome.-l As both these con­ length is adjusted until the corneal and iridal ditions with oval pupils have an underlying reflexes meet. The length of the beam sympathetic dysfunction. a cause and effect required is proportional to the depth of the relationship may be inferred. We undertook anterior chamber (1.117 x slit beam this study to examine this relationship further length +0.5(79). by comparing the dilation characteristics of Twenty-eight eyes had anterior chamber Phenylephrine Hydrochloride (a direct acting depths of less than 2.2 mm and the remaining amine) and Cyclopentolate Hydrochloride (a 58 eyes had anterior chamber depths of parasympathetic agonist). Particular atten­ greater than 2,2 mm. Details of the study tion was paid to any differential dilation in the group are shown in Table I. Two drops of Phe­ vertical meridian. nylephrine hydrochloride 10'/;, were instilled into the inferior fornix of one eye and Cyclo­ SUbjects and methods pentolate 1 % into the second eye of each sub­ Informed consent was obtained from 43 sub­ ject. The right and left eyes were randomly jects (86 eyes). There were 17 males and 26 selected for each of these drugs. Pupillary size females between 15 and 89 years of age, was recorded. in dim background illumina­ Recruitment was from general ophthalmic tion, by flash photography at 0,5, 10, 15.20

Correspondence to: N, J, Watson, Department of Ophthalmology. University of Aberdeen. ForesterhilL Aberdeen AB9 2ZB. THE OVAL PUPIL 467

'Yo Table I SlIi>/ecr characrerisrics ride 1 did not show any meridional prefer­ ence during dilation. Twenty-seven of the 43 Age range 15-89 years eyes treated with Phenylephrine hydrochlo­ Sex ride 10% showed a preferential dilation in the Male 17 patients vertical meridian, the pupils becoming ver­ Female 26 patients tically oval, prior to resuming a round contour Chamber depth on complete mydriasis (Figs. 2 and 3). A Anterior chamber <2.2 mm 28 eyes maximum dilation ratio was obtained 15 to 20 Anterior chamber >2.2 111m 58 eyes minutes after drug instillation. The time point Iris colour at which maximal vertical dilation occurred 48 Light eyes with Phenylephrine hydrochloride 10% had Dark 38 eyes no relationship to the anterior chamber depth. The 15 minute dilation ratios of the and 25 minutes. In order to eliminate the right and left eyes of each subject were com­ problems of magnification the pupil dilation pared. The differences in dilation ratio was recorded as the ratio of pupil size ver­ between Cyclopentolate and Phenylephrine tically and horizontally, a vertically oval pupil treated eyes was statistically significant having a pupil dilation ratio> 1 (see Fig. 1). (P<0.05 chi sq test) in subjects with anterior The intraocular pressure was monitored chamber depths less than 2.2 mm (Figs. 4 and throughout the procedurc and pupillary dila­ 5). A significant direct relationship was found tion reversed with Pilocarpine hydrochloride between anterior chamber depth and dilation 4% either after 25 minutes or if there was an ratio, the shallower the anterior chamber, the increase in intraocular pressure. Subjects who greater the dilation ratio (r = 0.526, Fig. 6). showed a rise in intraocular pressure over Other factors like iris colour, age and sex had 30 mm of mercury were excluded from the no relation to the dilation ratio. study, and referred for further ophthalmo­ Discussion logical care. The results of this 'Study indicate that Cyclo­ Results pentolate hydrochloride 1 % and Phenyl­ Eyes treated with Cyclopentolate hydrochlo- ephrine hydrochloride 10')10 have different pupillary dilation dynamics. This has not been previously described. These drugs act on dif­ ferent components of the autonomic nervous system suggesting that differential innerv­ ation is responsible for the oval pupil. A reduction in the autonomic responses with age has been reported both for systemic and

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Dilation Ratio = alb

Fig. I. The dilmion rario is defined w; rhe rario of Fig. 2. Ere IIwlled wirll Phenylephrine Hydro­ pupil size IWlicallr 10 lIorizonlal/r. This eliminalcs chloride 10°/" demonslr(l{eS prererenlial dilalion in lil e problems of magnificariOiL I'erlical meridian. PlloIogrllpil s al () and 15 lI1illliles. 468 H S. DUA ET AL.

tion characteristics observed with Phenyl­ ephrine hydrochloride ]()'/'o. Bienfang et al. x showed that mydriatic applied locally on the limbus causes dilation to occur in that section of the pupil nearest the site of applicatiion. The vertical nature of the oval pupil could. therefore. be attributed to pooling of the mydriatic agent in the tear meniscus. Mechan­ ical apposition of the iris to the anterior lens surface may vary in eyes with differing ' anterior chamber depths. possibly explaining different dilation characteristics. However. both of these factors. namely pooling of drug Fig. 3. Eye treated with Cyc/opentolate Hydro­ chloride I 'y" does not show preFerential dilation. Photo­ in the tear meniscus and mechanical apposi­ graphs at () and 15 minutes. tion. should e4ually affect dilation caused by Phenylephrine hydrochloride IO'X, and Cyc\o­ " pupillary function. Although anterior cham­ pentolate hydrochloride 1%. but this was not 7 ber depth is known to decline with age. in this found to be the case in this study. Moreover. study the relationship between pupil dilation pooling in the tear meniscus would cause pref­ ratio and anterior chamber depth had no cor­ erential dilation at the inferior pole unlike the relation with the age of our subjects. Age preferential dilation at the superior and infer­ therefore cannot account for the pupil dila- ior poles observed in this study. Therefore. neither mechanical apposition of the iris and n ,------,lens or drug pooling would explain vertical preferential dilation with Phenylephrine o P< 0.05

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o C T c � 0 u c o +'" 1 o -m 0 .- 11 10 1 0 - § 0 0 .- tl '.I 1 B I o I I 9 r 8 l i Q.8! B Cl U 11 1.1 " § Phen�ephrine10% Cydopentolate1 % Fig. 4. Dilation ratio for patients with shaflow 10% Cydopentolate1 % anterior cham hers. The anterior chamber depth has a Phenylephrine significant effect on the dilation ratio after 15 minlltes in Fig. 5. Dilation /'iItio ,l(JI' patiellls with Deep allfaior eyes treated with Phmylephrine Hvdrochloride II),Y" chambers. The alllerior chall/ber depth has no Ip

ur------__ � We have shown that sympathetic stimulation ! with Phenylephrine hydrochloride 10% can L I o cause an oval pupil in eyes with a shallow .1 anterior chamber. That a similar vertically a T I oval pupil is usually seen in APACG supports �r the concept that aberrant sympathetic activity (1j 18 � I may be the cause of differential pupil dilation L. I in the vertical meridian. I If the observed effect is due to an abnormal C IIr i I sympathetic innervation it could be part of the :9 i sympathetic abnormalities associated with a I 0 I APACG. The high dilation ratio may suggest o I �1'1 an individual is at risk of APACG and could o 1 also increase the sensitivity of mydriatic test­ - r ! I co l ing in patients with shallow anterior cham­ o 12r bers. Long term observation and controlled L clinical studies will be needed to confirm this. I o I Consent

The results ohtained for this manuscript were obtained after the nature of the procedure had been fully � �'------L------L------L------�explained to the suhjects and consent ohtained. :5 15

Key words: Iris autonomic inervation. Pupil dilation. NC Depth (mm) Acute glaucoma. Anterior chamber depth. LJ Phen�ephnne 10% References � 1 % Cydopentolate I Duke-Elder S and Jay B: Diseases of the lens and vit­ reous. glaucoma and hypotony. In Duke-Elder S Fig. 6. A comparison of dilation ratios with anterior cd. System of Ophthalmology, London. Henry chamber depth. A correlation is shown ill eyes treated Kimpton 1969: Volume XI: 569-71. with Phenyleph rine Hvdrochloride 10% II' = 0.526). • Barkan 0: Glaucoma: classification. causes and sur­ No correlatio/1 was tound in eres treated with gical control. Am J Ophthalmol 1938. 21: Cyclopentolate HI'drochloride I "/0 I;' = 0'()02). 1099-1117 . hydrochloride 10'10 and not with Cyclopento­ .1 Philips: Closed Angle Glaucoma-Significance of sectoral variations in angle depth. Br J Ophthal­ late hydrochloride 1 %. The explanation may mol 1956. 40: 136-40. have an anatomical or physiological basis. 1 Thompson HS. Zackon DH. Czarnecki JSC: Tad­ either a variable sympathetic innervation with pole shaped pupils caused by segmental spasm of a higher intensity of receptors in the superior the iris dilator muscle. Am J Ophthalmol1983.96: and inferior poles of the iris. or a preferential 467-477. 'Smith RJH: A new method of estimating the depth distribution of dilator muscle fibresin the ver­ of the anterior chamber. Rr J Ophthalmol 1979. tical meridian. We are currently investigating 63: 215-20. �hese possibilities using immunocyto­ I, Dorczyn AD. Laor N. Nemet P: Sympathetic pupil­ chemistry and special staining for adrenergic lary tone in old age. Arch Ophthalmol 1976.94: receptors and smooth muscles. 1905-6. 7 Abnormal ocular autonomic function can Wcekers R. Grietcn J. Lavergne G: Study of the dimensions of the human anterior chamber. Oph­ predispose individuals to APACG by modi­ thalmologica 1961. 142: 650. fication of physiological pupil block particu­ , Bienfang DC: Sector pupillary dilation with an epi­ larly in eyes with shallow anterior chambers. 2 nephrine strip. Am J OphthalmoI1973. 75: 883.