About ''PERRLA''

In our experiment, we are supposed to measure the pupil size using PERRLA in scotopic and photopic conditions.
Some instruments were used to aid us in the experiment. Namely the pen torch, Burton's lamp, digital camera, and the reading chart.

Each alphabet in PERRLA has a meaning; it is stated below together with the steps and questions that are needed to ask one while checking patient’s eyes:

• Pupils - Is the pupil present? We need to check whether if the subject has a pupil or else the 'Perrla' cannot continue.



As seen in the above picture, the above right eye has pupil present and it is round.

• Equal – both pupils must be equal in size.
• Round – both pupils must be round in shape and not any other shape.



the above picture seen above is the left eye and it is as round as the right eye. Both pupil are also round in shape. Thus, we can continue with the PERRLA experiment.

• Reactive to • Light – pupils must be reactive to light. If light is shone directly in the right eye, there must be a constriction of the right and the left pupil. Followed by dilation of both pupils when light is brought away. Direct papillary reflex takes place when light is shone directly on the retina of the same eye. Consensual reflex happened when the left eye constricts when light is flashed into the right eye, because portion of the retina is stimulated when light was flashed onto the right retina.



The above picture shows the pupil constricts when light is shone directly to the right eye. This shows direct pupil reflex.



This pupil, from the left eye has shown constriction even though light was shone on the right eye. This explains consensual pupil reflex.

• Accommodation – allow the subject to focus on an object. The size of subject’s pupil would be more dilated and larger when the object is brought closer to the eye. The size of subject’s pupil would become smaller and constricts as the object is being brought further away from the subject or when the subject is forced to view an object at a far distant. While using PERRLA in a photopic environment.




The picture above shows a Burton's lamp and its used to magnify the pupil to determine if the pupil is round and for measuring the pupil accurately. The picture shows how the burton's lamp is used to magnify the eye. A ruler is placed behind the Burton's lamp for measuring the pupil size.

Sources from: http://rarediseases.about.com/od/medicalterms/g/perrla.htm


http://www.opt.indiana.edu/riley/HomePage/Pupil_Abnormal/1_Saint_Pupil_Abnormal.html


While using PERRLA in a scotopic environment.

Explanation on papillary pathway.

Afferent limb of the parasympathetic pathway.

A light will act as a stimulus. This will trigger the photoreceptors and a signal will be conveyed to the ganglion cells. Their impulse will send through the axons in a similar manner as those carrying information to the optic never head.
However, these information from the ganglion cell passes information to the superior colliculus through the brachium where they synapase on the pretectal olivary nuclei. After the projection to the pretactactal nucleus, these projections will lead to the edinger westphal nucleus by internuncial neurons.

The picture gives an illustration of how the signal is sent.



Efferent limb of the parasympathetic pathway:
After getting the information from the pretactal nucleus, Edinger Westphal nucleus will then send information through fibers to join the oculomotor cranial nerve VIII(8) and follow the course on the dorsomedial surface of the nerve. These fibers will then emerge to enter the orbit with the inferior obliquw branch of cranial nerve III (3) by crossing through the cavernous sinus. The synapses at the ciliary ganglion enter through the short posterior ciliary nerves to distribute fibers to the ciliary body and iris.



The above picture shows the innervation of the cilary muscle from the sideways.

http://www.tedmontgomery.com/the_eye/eyephotos/reflex.html
(Open this link)
As seen in this website, The nerve impulse travels to the pretactal nucleus then to the edinger westphal nucleus.

Efferent sympathetic pathway: It was believe to start in the hypothalamus. It is projected in straight synapses. These neurons project to and synapse upon intermediolateral cell column from the C8-T2 spinal cord. The neurons exit through the superior cervical ganglion. The fibers passes through the internal carotid artery, which enter the cavernous sinus and travel with cranial nerve VI in the cavernous sinus to enter the superior orbital fissure with cranial nerve V.
Next, the fibers will travel with the nasociliary branch of V, and pass through the ciliary ganglion without synapsing. Finally, the fibers pass through the long ciliary nerves to terminate on the dilator muscle.


Source from: http://www.medrounds.org/ocular-pathology-study-guide/2005/11/pupillary-reflex-pathway.html

Explanation on one abnormal papillary condition.

The papillary condition that is going to be covered will be the Marcus Gunn pupil condition. The condition is an afferent papillary defect which means that pathway from the eyes to the brain is in defect.(The Afferent pathway)

When the strength of the sensory detection from one eye is different from the other, it will cause the degree of papillary constriction with light shining on one pupil will be less than with the light shining onto the other eye.



The above diagram shows a normal person and a person who has Marcus Gunn pupil. A normal eye will constrict when swing light test was carried out while a Marucs Gunn pupil will not constrict.

The causes include optic neuritis (Multiple Sclerosis – MS) and retinal injuries. Not only have that, compression of the optic nerve in the orbit also caused an afferent papillary defect. However injuries of the optic pathways that are distal to the lateral geniculate will not produce an afferent papillary defect.


There are several causes of this abnormal papillary condition. They include central retinal artery occlusion, central retinal vein occlusion, optic atrophy, marked retinal detachment, anterior ischemic optic neuropathy, branch retinal vein occlusion and asymmetric primary open angle glaucoma.

Treatment is not usually necessary for this condition but if required surgery with bilateral levator excision and frontalis brow suspension may be used.




Here is a video which can fully explain the Marcus Gunn's pupil defect.

Sources taken from:
http://www.opt.indiana.edu/riley/HomePage/Pupil_Abnormal/1_Saint_Pupil_Abnormal.html
http://rad.usuhs.edu/medpix/parent.php3?mode=single&recnum=273
http://en.wikipedia.org/wiki/Marcus_Gunn_phenomenon#Treatment
http://umed.med.utah.edu/neuronet/lectures/2002/Basics%20in%20Neuro-Ophthalmology.htm