The pupil is the mirror of various diseases. The various reflection of pupil shape, size and reaction represent the various disease. Many ocular diseases are diagnosed by the pupillary reaction and structure.
By the torch light examined we easily find lots of ocular problem.
This is how I discussed some various shape,size and reaction of the pupil .

The discussion topics are โ€”โ€”
~ ๐˜ž๐˜ฉ๐˜ข๐˜ต ๐˜ช๐˜ด ๐˜—๐˜ถ๐˜ฑ๐˜ช๐˜ญ
~ ๐˜•๐˜ฐ๐˜ณ๐˜ฎ๐˜ข๐˜ญ ๐˜—๐˜ถ๐˜ฑ๐˜ช๐˜ญ ๐˜ด๐˜ฉ๐˜ข๐˜ฑ๐˜ฆ & ๐˜ด๐˜ช๐˜ป๐˜ฆ
~ ๐˜Š๐˜ฉ๐˜ข๐˜ฏ๐˜จ๐˜ฆ ๐˜ฐ๐˜ง ๐˜—๐˜ถ๐˜ฑ๐˜ช๐˜ญ ๐˜ด๐˜ช๐˜ป๐˜ฆ ๐˜ฅ๐˜ถ๐˜ฆ ๐˜ต๐˜ฐ ๐˜ท๐˜ข๐˜ณ๐˜ช๐˜ฐ๐˜ถ๐˜ด ๐˜ฅ๐˜ช๐˜ด๐˜ฆ๐˜ข๐˜ด๐˜ฆ๐˜ด ๐˜ข๐˜ฏ๐˜ฅ ๐˜ด๐˜ต๐˜ข๐˜ต๐˜ฆ
~ ๐˜Š๐˜ฉ๐˜ข๐˜ฏ๐˜จ๐˜ฆ ๐˜ฐ๐˜ง ๐˜—๐˜ถ๐˜ฑ๐˜ช๐˜ญ ๐˜ด๐˜ฉ๐˜ข๐˜ฑ๐˜ฆ ๐˜ฅ๐˜ถ๐˜ฆ ๐˜ต๐˜ฐ ๐˜ท๐˜ข๐˜ณ๐˜ช๐˜ฐ๐˜ถ๐˜ด ๐˜ค๐˜ฐ๐˜ฏ๐˜ฅ๐˜ช๐˜ต๐˜ช๐˜ฐ๐˜ฏ & ๐˜ฅ๐˜ช๐˜ด๐˜ฆ๐˜ข๐˜ด๐˜ฆ๐˜ด
~ ๐˜—๐˜ถ๐˜ฑ๐˜ช๐˜ญ๐˜ญ๐˜ข๐˜ณ๐˜บ ๐˜ญ๐˜ช๐˜จ๐˜ฉ๐˜ต ๐˜ณ๐˜ฆ๐˜ข๐˜ค๐˜ต๐˜ช๐˜ฐ๐˜ฏ
~ ๐˜๐˜ข๐˜ณ๐˜ช๐˜ฐ๐˜ถ๐˜ด ๐˜ค๐˜ฐ๐˜ญ๐˜ฐ๐˜ถ๐˜ณ ๐˜ฐ๐˜ง ๐˜ฑ๐˜ถ๐˜ฑ๐˜ช๐˜ญ๐˜ญ๐˜ข๐˜ณ๐˜บ ๐˜ณ๐˜ฆ๐˜ง๐˜ญ๐˜ฆ๐˜ค๐˜ต๐˜ช๐˜ฐ๐˜ฏ
~ ๐˜—๐˜ถ๐˜ฑ๐˜ช๐˜ญ๐˜ญ๐˜ข๐˜ณ๐˜บ ๐˜ญ๐˜ช๐˜จ๐˜ฉ๐˜ต ๐˜ณ๐˜ฆ๐˜ง๐˜ญ๐˜ฆ๐˜น ๐˜ฑ๐˜ข๐˜ต๐˜ฉ๐˜ธ๐˜ข๐˜บ.
1) แดกสœแด€แด› ษชs แด˜แดœแด˜ษชสŸ?

Ans:- In the centre of the iris there is a round shape opening structure called pupil.
๐˜š๐˜ช๐˜ป๐˜ฆ- Normally, it varies between 2-4 mm. It may be smaller ( ๐˜ฎ๐˜ช๐˜ฐ๐˜ด๐˜ช๐˜ด) or may be larger ( mydriasis).

For the refractive status size of the pupil is normally changed.
In ๐˜”๐˜บ๐˜ฐ๐˜ฑ๐˜ช๐˜ค ๐˜ฑ๐˜ข๐˜ต๐˜ช๐˜ฆ๐˜ฏ๐˜ต, the size of the pupil > equal to 4 ๐˜ฎ๐˜ฎ ( Mydriasis).
In ๐˜๐˜บ๐˜ฑ๐˜ฆ๐˜ณ๐˜ฎ๐˜ฆ๐˜ต๐˜ณ๐˜ฐ๐˜ฑ๐˜ช๐˜ค ๐˜ฑ๐˜ข๐˜ต๐˜ช๐˜ฆ๐˜ฏ๐˜ต, the size of thr pupil < equal to 2 ๐˜ฎ๐˜ฎ ( ๐˜”๐˜ช๐˜ฐ๐˜ด๐˜ช๐˜ด).
In ๐˜Œ๐˜ฎ๐˜ฎ๐˜ฆ๐˜ต๐˜ณ๐˜ฐ๐˜ฑ๐˜ช๐˜ค ๐˜ฑ๐˜ข๐˜ต๐˜ช๐˜ฆ๐˜ฏ๐˜ต, the size of the pupil lying between (2 to 4 )mm.
The reaction of pupil in ๐˜”๐˜บ๐˜ฐ๐˜ฑ๐˜ช๐˜ค ๐˜ฑ๐˜ข๐˜ต๐˜ช๐˜ฆ๐˜ฏ๐˜ต is good and fast and in ๐˜๐˜บ๐˜ฑ๐˜ฆ๐˜ณ๐˜ฎ๐˜ฆ๐˜ต๐˜ณ๐˜ฐ๐˜ฑ๐˜ช๐˜ค ๐˜ฑ๐˜ข๐˜ต๐˜ช๐˜ฆ๐˜ฏ๐˜ต is normal and slow.
๐˜ž๐˜ฉ๐˜ข๐˜ต ๐˜ข๐˜ณ๐˜ฆ ๐˜ต๐˜ฉ๐˜ฆ ๐˜ค๐˜ข๐˜ถ๐˜ด๐˜ฆ๐˜ด ๐˜ฐ๐˜ง ๐˜ฎ๐˜ช๐˜ฐ๐˜ด๐˜ช๐˜ด ๐˜—๐˜ถ๐˜ฑ๐˜ช๐˜ญ?– small pupil

=Including thypermetropia there are lot of factor which are responsible for the miosis Pupil.these are —


(1) แด‡xแด›ส€แด‡แดแด‡ แดา“ แด€ษขแด‡s = In the older of size of pupil becomes gradually decreasing. For this recover in extreme of age the size of Pupil miosis.

(2) ษชษด ส™ส€ษชษขสœแด› สŸษชษขสœแด›= sunlight or bright light the Pupil is constricteal for this recover Size of pupil become small.

(3) แดแดส€แด˜สœษชษดแด‡ ษชษดsแด›ส€แดœแด„แด›ษชแดษดs= morphine is a very story painkiller when is talles. By the reaction of it’s the size of the Pupil become miosis.

(4) แด˜แดษดแด›ษชษดแดœแด‡ สœแด‡แดแด€ส€แด€ษขแด‡=pontinue hemarage is a form of a intra cranial hemarage the most common cause of this problem is long standing poorly uncontrol chronic hypertension.

(5) แด€แด„แดœแด›แด‡ ษชส€ษชแด›ษชs= iritis is intranation of the iris ,when the iritis develops suddenly,over .for the acute iritis pupil become miosis.
Acute Iritis – Iritis is the inflammation of the iris, when the Iritis develops suddenly , over hours and days is known as acute Iritis. For the acute Iritis pupil become miosis.
Use of Miotic drug- Use of Miotic drug the size of the pupil become smaller ( eg – Pilocarpine ).
2) แดกสœแด€แด› แด€ส€แด‡ แด›สœแด‡ แด„แด€แดœsแด‡ แดา“ แดสแด…ส€ษชแด€sษชs? (big pupil size>4mm)

Ans:- Including moderate high myopia there are lot of factors which are responsible for ๐˜ฑ๐˜ถ๐˜ฑ๐˜ช๐˜ญ ๐˜ฎ๐˜บ๐˜ฅ๐˜ณ๐˜ช๐˜ข๐˜ด๐˜ช๐˜ด, they are :

i) ๐˜–๐˜ฑ๐˜ต๐˜ช๐˜ค ๐˜ˆ๐˜ต๐˜ณ๐˜ฐ๐˜ฑ๐˜ฉ๐˜บ – When the optic nerve gets damage anywhere along the path from retina to LGB(Lateral Geniculate Body), then ๐˜ฎ๐˜บ๐˜ฅ๐˜ณ๐˜ช๐˜ข๐˜ด๐˜ช๐˜ด takes place.

ii) ๐˜ˆ๐˜ค๐˜ถ๐˜ต๐˜ฆ ๐˜ข๐˜ต๐˜ต๐˜ข๐˜ค๐˜ฌ ๐˜ช๐˜ฏ ๐˜ข๐˜ฏ๐˜จ๐˜ญ๐˜ฆ ๐˜ค๐˜ญ๐˜ฐ๐˜ด๐˜ถ๐˜ณ๐˜ฆ ๐˜จ๐˜ญ๐˜ข๐˜ถ๐˜ค๐˜ฐ๐˜ฎ๐˜ข – It occurs when the iris bulges forward due to narrow or blockage in the drainage angle ,fluid can’t circulate through the eye and pressure increases resulting in ๐˜ฎ๐˜บ๐˜ฅ๐˜ณ๐˜ช๐˜ข๐˜ด๐˜ช๐˜ด.

iii) ๐˜ˆ๐˜ฃ๐˜ด๐˜ฐ๐˜ญ๐˜ถ๐˜ต๐˜ฆ ๐˜Ž๐˜ญ๐˜ข๐˜ถ๐˜ค๐˜ฐ๐˜ฎ๐˜ข – It is the end stage in all types of glaucoma. The eye has no vision, there is totally absence of pupillary light reflex and pupillary response, due to this size of pupil increases.

iv) ๐˜Š๐˜ฐ๐˜ฎ๐˜ข๐˜ต๐˜ฐ๐˜ด๐˜ฆ ๐˜ฑ๐˜ข๐˜ต๐˜ช๐˜ฆ๐˜ฏ๐˜ต –
Coma is a state of prolonged unconsciousness with dilated pupil.

v) ๐˜๐˜ฆ๐˜ข๐˜ฅ ๐˜ช๐˜ฏ๐˜ซ๐˜ถ๐˜ณ๐˜บ – It sometimes results in ๐˜ฎ๐˜บ๐˜ฅ๐˜ณ๐˜ช๐˜ข๐˜ด๐˜ช๐˜ด.

vi) 3๐˜ณ๐˜ฅ ๐˜ฏ๐˜ฆ๐˜ณ๐˜ท๐˜ฆ ๐˜ฑ๐˜ข๐˜ญ๐˜ด๐˜บ- The pupil becomes fixed and dilated due to paralysis of ๐˜ด๐˜ฑ๐˜ฉ๐˜ช๐˜ฏ๐˜ค๐˜ต๐˜ฆ๐˜ณ ๐˜ฑ๐˜ถ๐˜ฑ๐˜ช๐˜ญ๐˜ญ๐˜ข๐˜ฆ, pupil become larger.

vii) ๐˜œ๐˜ด๐˜ฆ ๐˜ฐ๐˜ง ๐˜ฎ๐˜บ๐˜ฅ๐˜ณ๐˜ช๐˜ข๐˜ต๐˜ช๐˜ค๐˜ด – Pupil gets dilated due to the use of drugs like atropine, homatropine, phenylphrine.

viii) ๐˜๐˜ฏ ๐˜ฅ๐˜ข๐˜ณ๐˜ฌ ๐˜ฑ๐˜ญ๐˜ข๐˜ค๐˜ฆ๐˜ด – The pupil gets larger in dark areas to allow more amount of light.
๐˜›๐˜ฉ๐˜ฆ ๐˜ด๐˜ฉ๐˜ข๐˜ฑ๐˜ฆ ๐˜ฐ๐˜ง ๐˜ต๐˜ฉ๐˜ฆ ๐˜ฑ๐˜ถ๐˜ฑ๐˜ช๐˜ญ ๐˜ค๐˜ฉ๐˜ข๐˜ฏ๐˜จ๐˜ฆ๐˜ด ๐˜ฃ๐˜บ ๐˜ต๐˜ฉ๐˜ฆ ๐˜ท๐˜ข๐˜ณ๐˜ช๐˜ฐ๐˜ถ๐˜ด ๐˜ฐ๐˜ค๐˜ถ๐˜ญ๐˜ข๐˜ณ ๐˜ฅ๐˜ช๐˜ด๐˜ฆ๐˜ข๐˜ด๐˜ฆ๐˜ด. ๐˜๐˜ฆ๐˜ณ๐˜ฆ ๐˜ ๐˜ฅ๐˜ช๐˜ด๐˜ค๐˜ถ๐˜ด๐˜ด๐˜ฆ๐˜ฅ ๐˜ช๐˜ฏ ๐˜ท๐˜ฆ๐˜ณ๐˜บ ๐˜ด๐˜ฉ๐˜ฐ๐˜ณ๐˜ต๐˜ญ๐˜บ โ€”โ€”

(๐˜ˆ) ษชส€ส€แด‡ษขแดœสŸแด€ส€ ๐˜ดสœแด€แด˜แด‡ :- ๐˜›๐˜ฉ๐˜ฆ ๐˜ด๐˜ช๐˜ป๐˜ฆ ๐˜ฐ๐˜ง ๐˜ต๐˜ฉ๐˜ฆ ๐˜ฑ๐˜ถ๐˜ฑ๐˜ช๐˜ญ ๐˜ฃ๐˜ฆ๐˜ค๐˜ฐ๐˜ฎ๐˜ฆ ๐˜ช๐˜ณ๐˜ณ๐˜ฆ๐˜จ๐˜ถ๐˜ญ๐˜ข๐˜ณ ๐˜ข๐˜ง๐˜ต๐˜ฆ๐˜ณ ๐˜ต๐˜ฉ๐˜ฆ ๐˜ต๐˜ณ๐˜ข๐˜ถ๐˜ฎ๐˜ข ๐˜ฐ๐˜ณ ๐˜ช๐˜ณ๐˜ช๐˜ต๐˜ชs.

(๐˜‰) แด…-๐˜ดสœแด€แด˜แด‡แด… แด˜แดœแด˜ษชสŸ :- ๐˜›๐˜ฉ๐˜ฆ ๐˜ด๐˜ช๐˜ป๐˜ฆ ๐˜ฐ๐˜ง ๐˜ต๐˜ฉ๐˜ฆ ๐˜ฑ๐˜ถ๐˜ฑ๐˜ช๐˜ญ ๐˜ข๐˜ฑ๐˜ฑ๐˜ฆ๐˜ข๐˜ณ๐˜ด ๐˜ข๐˜ด ๐˜‹- ๐˜ด๐˜ฉ๐˜ข๐˜ฑ๐˜ฆ๐˜ฅ, ๐˜ธ๐˜ฉ๐˜ฆ๐˜ฏ ๐˜ช๐˜ณ๐˜ช๐˜ฅ๐˜ฐ๐˜ค๐˜บ๐˜ค๐˜ญ๐˜ช๐˜ต๐˜ช๐˜ด ๐˜ฑ๐˜ณ๐˜ฐ๐˜ฃ๐˜ญ๐˜ฆ๐˜ฎ ๐˜ข๐˜ณ๐˜ฆ ๐˜ฑ๐˜ณ๐˜ฆ๐˜ด๐˜ฆ๐˜ฏ๐˜ต.

(๐˜Š) ส™แดแด€แด› แดส€ สœแด€แดแดแดแด„แด‹ ๐˜ดสœแด€แด˜แด‡แด… :- ๐˜ž๐˜ฉ๐˜ฆ๐˜ฏ ๐˜ท๐˜ช๐˜ต๐˜ณ๐˜ช๐˜ฐ๐˜ถ๐˜ด ๐˜ญ๐˜ฐ๐˜ด๐˜ด ๐˜ฅ๐˜ถ๐˜ณ๐˜ช๐˜ฏ๐˜จ ๐˜ค๐˜ข๐˜ต๐˜ข๐˜ณ๐˜ข๐˜ค๐˜ต ๐˜ด๐˜ถ๐˜ณ๐˜จ๐˜ฆ๐˜ณ๐˜บ, ๐˜ต๐˜ฉ๐˜ฆ๐˜ฏ ๐˜ต๐˜ฉ๐˜ฆ ๐˜ฑ๐˜ถ๐˜ฑ๐˜ช๐˜ญ ๐˜ฃ๐˜ฆ๐˜ค๐˜ฐ๐˜ฎ๐˜ฆ ๐˜‰๐˜ฐ๐˜ข๐˜ต ๐˜ฐ๐˜ณ ๐˜ฉ๐˜ข๐˜ฎ๐˜ฎ๐˜ฐ๐˜ค๐˜ฌ ๐˜ด๐˜ฉ๐˜ข๐˜ฑ๐˜ฆ๐˜ฅ.

(๐˜‹) แด˜แด‡แด€ส€ ๐˜ดสœแด€แด˜แด‡แด… แด€ษดแด… แดœษดแด…ส€แด€แดกษด แด˜แดœแด˜ษชสŸ :- ๐˜๐˜ฏ๐˜ค๐˜ข๐˜ณ๐˜ค๐˜ฆ๐˜ณ๐˜ข๐˜ต๐˜ช๐˜ฐ๐˜ฏ ๐˜ฐ๐˜ง ๐˜ช๐˜ณ๐˜ช๐˜ด ๐˜ธ๐˜ช๐˜ต๐˜ฉ ๐˜ค๐˜ฐ๐˜ณ๐˜ฏ๐˜ฆ๐˜ข๐˜ญ ๐˜ธ๐˜ฐ๐˜ถ๐˜ฏ๐˜ฅ.

(๐˜Œ) า“แด‡๐˜ดแด›แดแดษดแด‡แด… แด˜แดœแด˜ษชสŸ :- ๐˜๐˜ณ๐˜ช๐˜ฅ๐˜ฐ๐˜ค๐˜บ๐˜ค๐˜ญ๐˜ช๐˜ต๐˜ช๐˜ด (๐˜ข๐˜ค๐˜ถ๐˜ต๐˜ฆ ๐˜ช๐˜ฏ๐˜ง๐˜ญ๐˜ข๐˜ฎ๐˜ข๐˜ต๐˜ช๐˜ฐ๐˜ฏ ๐˜ฐ๐˜ง ๐˜ต๐˜ฉ๐˜ฆ ๐˜๐˜ณ๐˜ช๐˜ด ๐˜ข๐˜ฏ๐˜ฅ ๐˜ค๐˜ช๐˜ญ๐˜ช๐˜ข๐˜ณ๐˜บ ๐˜ฃ๐˜ฐ๐˜ฅ๐˜บ) ๐˜ช๐˜ด ๐˜ต๐˜ฉ๐˜ฆ ๐˜ฎ๐˜ฐ๐˜ด๐˜ต ๐˜ค๐˜ฐ๐˜ฎ๐˜ฎ๐˜ฐ๐˜ฏ ๐˜ง๐˜ฆ๐˜ข๐˜ต๐˜ถ๐˜ณ๐˜ฆ๐˜ด ๐˜ฐ๐˜ง ๐˜ถ๐˜ท๐˜ฆ๐˜ช๐˜ต๐˜ช๐˜ด.

(๐˜) แดษชแด… – แด…ษชสŸแด€แด›แด‡แด… & แดแด แด€สŸ แด˜แดœแด˜ษชสŸ :- ๐˜๐˜ฐ๐˜ณ ๐˜ต๐˜ฉ๐˜ฆ ๐˜ข๐˜ฏ๐˜จ๐˜ญ๐˜ฆ ๐˜ค๐˜ญ๐˜ฐ๐˜ด๐˜ถ๐˜ณ๐˜ฆ ๐˜ฑ๐˜ข๐˜ต๐˜ช๐˜ฆ๐˜ฏ๐˜ต ๐˜จ๐˜ญ๐˜ข๐˜ถ๐˜ค๐˜ฐ๐˜ฎ๐˜ข ๐˜ฑ๐˜ข๐˜ต๐˜ช๐˜ฆ๐˜ฏ๐˜ต๐˜ด ๐˜ฑ๐˜ถ๐˜ฑ๐˜ช๐˜ญ .

(๐˜Ž) แดษชแด… แด…ษชสŸแด€แด›แด‡ แดแด แด€สŸ แด€ษดแด… ษชษดา“แด‡ส€๐˜ดแดษดแด€สŸ :- ๐˜ž๐˜ฉ๐˜ฆ๐˜ฏ ๐˜ต๐˜ฉ๐˜ฆ ๐˜ช๐˜ณ๐˜ช๐˜ด ๐˜ช๐˜ด ๐˜ข๐˜ฃ๐˜ด๐˜ฆ๐˜ฏ๐˜ต (๐˜ช๐˜ณ๐˜ช๐˜ด ๐˜ค๐˜ฐ๐˜ญ๐˜ฐ๐˜ฃ๐˜ฐ๐˜ฎ๐˜ข), ๐˜ต๐˜ฉ๐˜ฆ ๐˜ด๐˜ฉ๐˜ข๐˜ฑ๐˜ฆ ๐˜ฐ๐˜ง ๐˜ต๐˜ฉ๐˜ฆ ๐˜ฑ๐˜ถ๐˜ฑ๐˜ช๐˜ญ ๐˜ค๐˜ฉ๐˜ข๐˜ฏ๐˜จ๐˜ฆ ๐˜ข๐˜ฏ๐˜ฅ ๐˜ช๐˜ต ๐˜ค๐˜ฐ๐˜ฏ๐˜ท๐˜ฆ๐˜ณ๐˜ต ๐˜ช๐˜ฏ๐˜ต๐˜ฐ ๐˜ข ๐˜ฐ๐˜ท๐˜ฆ๐˜ณ ๐˜ด๐˜ฉ๐˜ข๐˜ฑ๐˜ฆ.

Key hole appeance- After optical iridectomy key hole apperance are seen in the pupil.

๐˜๐˜ข๐˜ณ๐˜ช๐˜ฐ๐˜ถ๐˜ด ๐˜ค๐˜ฐ๐˜ญ๐˜ฐ๐˜ถ๐˜ณ ๐˜ณ๐˜ฆ๐˜ง๐˜ญ๐˜ฆ๐˜น ๐˜ฐ๐˜ง ๐˜ต๐˜ฉ๐˜ฆ ๐˜—๐˜ถ๐˜ฑ๐˜ช๐˜ญ๐˜ญ๐˜ข๐˜ณ๐˜บ ๐˜ข๐˜ณ๐˜ฆ๐˜ข

(1) แดŠแด‡แด› ส™สŸแด€แด„แด‹ แด˜แดœแด˜ษชสŸสŸแด€ส€ส ส€แด‡า“สŸแด‡x :- For the aphakic eye the reflection of the pupil is jet black colour.
(2) แดกสœษชแด›แด‡ แด˜แดœแด˜ษชสŸสŸแด€ส€ส ส€แด‡า“สŸแด‡x :- White pupillary reflex are seen in the cataract eye.
(3) ษขสŸแด€sส แด˜แดœแด˜ษชสŸสŸแด€ส€ส ส€แด‡า“สŸแด‡x :- For pseudophekic eye glasy pupillary reflex are visible.
(4) แด€แดแด€แดœส€แด€แด›ษชแด„ แด„แด€แด›’s แด‡สแด‡ ส€แด‡า“สŸแด‡x :- If the Retiono blastoma, eongenital cataract, PHPV, Endopthalmitis, coloboma of Choroid like these type of problem present then the Amauratic cat’s eye reflex are visible.
๐™‹๐™๐™‹๐™„๐™‡๐™‡๐˜ผ๐™๐™” ๐™‡๐™„๐™‚๐™ƒ๐™ ๐™๐™€๐™๐™‡๐™€๐™“

In this topic, I will dicsuss —
~~Pupillary Light Reflex Pathway.
~~How To Localize The Site Of Lesion In Cases Of Abnormal Pupillary Reflex.

So I will start with the very basics.

This is the diagram of the eye. This circular brown structure is the Iris and this round gap in the center of the Iris is known as the Pupil.
The normal size of the Pupil ranges from 2-4 mm in diameter. Light enters our eye through the Pupil.
Now, when bright light is shone on the Pupil, the Pupil responds by decreasing in size. This is known as “Constriction of the Pupil” and this constriction of the Pupil in response to light stimulus is known as “Pupillary light reflex”.
Pupillary light reflex can be a Direct light reflex or it can be an Indirect light reflex which is also known as Consensual light reflex.

๐˜‹๐˜Œ๐˜™๐˜Œ๐˜Š๐˜› ๐˜“๐˜๐˜Ž๐˜๐˜› ๐˜™๐˜Œ๐˜๐˜“๐˜Œ๐˜Ÿ

Direct light reflex is when constriction of the Pupil is seen in response to light shone in the ๐˜š๐˜ข๐˜ฎ๐˜ฆ ๐˜ฆ๐˜บ๐˜ฆ, that is the Ipsilateral eye.

For example, if this the right eye of the patient and we shine light in this right eye & in response we see the Pupil of the right eye constricting, it is known as Direct light reflex because the response is occurring in the same eye that is receiving the stimulus.
๐˜Š๐˜–๐˜•๐˜š๐˜Œ๐˜•๐˜š๐˜œ๐˜ˆ๐˜“ / ๐˜๐˜•๐˜‹๐˜๐˜™๐˜Œ๐˜Š๐˜› ๐˜“๐˜๐˜Ž๐˜๐˜› ๐˜™๐˜Œ๐˜๐˜“๐˜Œ๐˜Ÿ

The other reflex is the consensual light ๐˜ณ๐˜ฆ๐˜ง๐˜ญ๐˜ฆ๐˜น. Consensual light reflex when the light stimulus is given to one eye but the response to that stimulus is seen in the opposite eye that is the Contralateral eye.
So, again in this patient, when we show light in the right eye, we will see constriction of the Pupil in the opposite eye that is the left eye. So this constriction of Pupil that occurs in response to light stimulus given in the contralateral eye is known as Consensual light reflex.
Both of these responses that is the direct light reflex as well as the consensual light reflex they occur simultaneously that is they occur together at the same time. So, if we shine light in the right eye, we will see both pupils constricting together, which means that the right eye will show direct light reflex and the left eye will show consensual light reflex and both of these reflexes are seen in response to the same light stimulus that was given in the right eye.


So how do you perform pupillary light reflex test?

First of all, it should be done in a semi dark room. ‘Semi dark’ so that you are able to observe the response in the contralateral eye. So we ask the patient to fixate on a distant object . If the patient fixate on a near object, the near reflex pathway will get activated which will cause pupillary constriction.
So we want to eliminate any cause of pupillary constriction when we are checking the pupillary light reflex pathway.
So we first observe the position, size and shape of the pupil in each eye. Then we shine the torch in one eye and we observe the response of the pupil in the same eye. This is the Direct light reflex. Then again we shine light in the same eye but this time we observe the response in the opposite eye. That is the contralateral eye & this is the consensual light reflex. And then we repeat the procedure on the other eye to check the direct & the consensual light reflex to light stimulus given on the opposite side.


Before proceeding further, we need to be absolutely clear about certain terminologies. Suppose in a patient, light is shone in the left eye and both pupils constrict, we document it as left direct light reflex present and light consensual light reflex present. So the nomenclature is with respect to the eye which is responding to the stimulus and not with respect to the eye which is receiving the stimulus.
Suppose in a patient’s case sheet it written that right direct light reflex and right consensual light reflex is present, it means that the right eye constricts to light stimulus given to the right eye which is the direct reflex and it also constricts to light stimulus given in the left eye which is the consensual reflex. So, right consensual reflex doesn’t mean that light stimulus is given in the right eye. It means that the pupillary response to light stimulus is seen in the right eye.
I hope this is clear for you now.

ษชส€ษชs แดแดœsแด„แดœสŸแด€แด›แดœส€แด‡

Now the storma of the iris has 2 muscles. The “Sphincter pupillae” and the “Dilator pupillae”.

sแด˜สœษชษดแด„แด›แด‡ส€ แด˜แดœแด˜ษชสŸสŸแด€แด‡

Sphincter pupillae muscle is circulary arranged at the border of the pupil. So when the sphincter pupillae contracts it leads to constriction of the pupil & this occurs via the parasympathetic pathway. This constriction of the pupil is known as Miosis.

แด…ษชสŸแด€แด›แดส€ แด˜แดœแด˜ษชสŸสŸแด€แด‡

The dilator pupillae muscle is inserted at the root of the iris and from there it extends radially to 2 mm from the pupillary margin. So, the dilator pupillae muscle gets activated by the dark reflex pathway which is a Sympathetic pathway and this results in dilatation of the pupil & dilatation of the pupil is known as Mydriasis.

Now the diameter of the pupil the result of the balance between these two antagonistic muscles of the iris that is the sphincter pupillae and the dilator pupillae of the iris.

Since in this topic I am talking about the light reflex pathway I will be restricting ourselves to only parasympathetic pathway that results in constriction of the pupil via the sphincter pupillae muscle.

แด˜แดœแด˜ษชสŸสŸแด€ส€ส สŸษชษขสœแด› ส€แด‡า“สŸแด‡x

So, Pupillary light reflex pathway is a parasympathetic pathway with an afferent limb and an efferent limb.

“Afferent limb” means that Sensory stimulus is carried to the brain via this route.
“Efferent limb” means that this route carries signals from the brain to the effector organ, that is the sphincter pupillae muscle in this case.

แด˜แดœแด˜ษชสŸสŸแด€ส€ส สŸษชษขสœแด› ส€แด‡า“สŸแด‡x แด˜แด€แด›สœแดกแด€ส

As we all know, Light enters the eye through pupil. Then it falls on the Retina of the eye. From the retinal gangionic cells, the information is carried by the the optic nerve. Optic nerve is the second cranial nerve. Optic nerve carries impulses from the nasal half of the retina and the temporal half of the retina. So the fibers here that are arranged laterally represent the temporal fibers and the fibers that are present medially represent the nasal fibers. Then the optic nerve reaches the optic chiasma. Optic chiasma is located just above the Pituitary gland. At the optic chiasma, decussation of these nerve fibers takes place. Now what is the meaning of decussation?
~ Decussation means that the nerve fibers from one side cross over to the opposite side. So the fibers that were carrying signals from the nasal half of Retina on the right side cross over to the left side but the fibers that were carrying from the temporal half of the Retina do not cross. They continue to travel along the same side that is along the right side. It is seen that the ratio of crossed to uncrossed fibers is approx 53:47 which means that more fibers cross over than those that stay on the same side. This decussation occurs on both the sides. So nasal fibers of the right eye cross over to the left side and then they continue with the temporal fibers of the left eye. While the nasal fibers of the left eye cross over to the right side and then they continue with the temporal fibers of the right eye. They continue as optic tracts. Thus each optic tract contains ipsilateral temporal fibers and contralateral nasal fibers. Now the pathway that we are discussing here is the pupillary light reflex pathway. But we also know that it is the same optic nerve that carries signals to the optical cortex of the brain via the visual pathway and this is how image processing takes place and I am able to see things. This means that the optic nerve carries afferents for vision as well as for pupillary constriction. Now how are these two pathways separate from each other?
So most of the nerve fibers that are carried by the optic tracts synapse in the lateral geniculate body. Lateral geniculate body is located in the thalamus and from the lateral geniculate body, the signals are carried to the visual centre which is located in the occipital lobe of the brain. So this is the visual pathway in brief. However a small number of these fibers- they don’t go to the lateral geniculate body. They exit from the optic tract and instead of going to the lateral geniculate body, they go to the pretectal nucleus. Pretectal nucleus is located in the midbrain at the level of the superior colliculus.

SK Samiul Haque

I am an Optometrist. Primary Eye Care Professional. Proud to be an Optometrist.

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