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she had no underlying disease but complained of slight muscle and general weakness , and her brother had died of myotonic dystrophy several years earlier .
her best - corrected visual acuity was 16/20 in both eyes , and intraocular pressure was 12 mmhg in the right eye and 13 mmhg in the left eye .
she had mild bilateral ptosis with margin reflex distance 1 of 0.5 mm in both eyes , and levator function test of 9 mm in both eyes [ fig . 1 ] .
alternative covering tests found orthophoria in her primary gaze , while ocular motility was normal .
poor response to mydriatics was noted , and characteristic bilateral snowflake cataracts were observed on the slit lamp examination [ fig . 2 ] . dilated fundus examination found an increased cdr of 0.5/0.5 , vertical / horizontal in both eyes , and a defect in the inferotemporal retinal nerve fiber layer in her right eye [ fig . 3 ] .
( b ) characteristic snowflake cataract high cup - to - disc ratio with inferotemporal retinal nerve fiber layer defect in the right eye we noticed ptotic appearance in her 14-year - old daughter , who was also present and who did not have any systemic or ocular complaints , which suggested ophthalmic examination .
the examination found the visual acuity of 20/20 in the right eye and 18/20 in the left eye , and intraocular pressure of 13 mmhg in the right eye and 16 mmhg in the left eye .
similar to her mother , mild bilateral ptosis with levator function of 9 mm in both eyes , poor response to mydriatics , and bilateral snowflake cataracts were noted [ fig . 4 ] .
( c ) characteristic snowflake cataract based on these ophthalmic findings , the patient and daughter were referred to the department of laboratory medicine for genetic evaluation for myotonic dystrophy using the southern blot polymerase chain reaction .
unstable repeats of 550 cytosine - thymine - guanine ( ctg ) units in the 3 untranslated region of the dm - protein kinase ( dmpk ) gene were found in both patients , indicating classic myotonic dystrophy type 1 [ fig . 5 ] . based on ophthalmic indications ,
both patients were diagnosed with myotonic dystrophy type 1 on genetic examination before the manifestation of other systemic changes [ fig . 6 ] .
( a ) the patient 's southern blot polymerase chain reaction finding consistent with myotonic dystrophy type 1 .
note the unstable expansion of 550 cytosine - thymine - guanine repeats of the dystrophia myotonica - protein kinase gene .
( b ) the daughter 's southern blot polymerase chain reaction finding . the same finding as her mother was noted pedigree of the myotonic dystrophy family .
circle , female ; square , male ; filled symbol , symptomatic ; open symbol , asymptomatic ; shaded symbol , affected status not known
myotonic dystrophy has heterogeneous clinical features including myotonia , progressive muscle weakness and atrophy , heart conduction abnormalities , insulin resistance , premature balding , and cataracts .
myotonic dystrophy is inherited in an autosomal dominant fashion via unstable expansions of specific nucleotide sequences , the number of which influences clinical features .
dm is classified as two clinical disorders , such as type 1 and type 2 , caused by an unstable expansion of the ctg trinucleotide repeat in the dmpk gene , or a similar expansion of the cytosine - ctg repeat in intron 1 of the cellular nucleic acid binding protein gene .
ocular symptoms are more severe in dm1 and include ptosis , external ophthalmoplegia , epiphora , pupillary light - near dissociation , early - onset cataract , pigmentary degenerative retinopathy , bilateral optic nerve atrophy , and hypotony .
nearly , all dm1 patients have bilateral iridescent cortical and subcapsular cataracts before the age of 50 years . in early phases ,
fine iridescent opacities develop in the cortex , which grow into a stellate cataract in the posterior subcapsular region . when more advanced , these are difficult to differentiate from other cortical cataracts .
ocular muscles degenerate just as other skeletal muscles , resulting in external ophthalmoplegia , motility disorder , weakness of orbicularis oculi and levator muscle , and ptosis .
retinal pigment epithelium changes can occur , including peripheral retinal degeneration , and result in decreased visual acuity .
hypotony could be related to increased outflow or decreased aqueous secretion although the pathogenic mechanism remains unclear .
our cases presented with cataracts , ptosis , weak pupillary response to mydriatics , low intraocular pressure , increased cdrs , and retinal nerve fiber layer defects .
glaucoma has not previously been associated with myotonic dystrophy , and if it is related to this disorder , the exact pathophysiology should be studied in greater depth . because the first patient we examined had ocular complications indicative of myotonic dystrophy , we recommended ophthalmic examination of her daughter despite the lack of systemic symptoms , and she also had ptosis and bilateral iridescent cataracts . genetic examination revealed the expansion of ctg repeats in the dmpk gene corresponding with myotonic dystrophy and both were diagnosed with dm1 .
early - onset iridescent cataracts are a characteristic finding in myotonic dystrophy , so this symptom could help in its diagnosis prior to the manifestation of systemic symptoms . even though there is no definite cure for myotonic dystrophy and management
is symptom based , a precise and early diagnosis is necessary for appropriate medical monitoring and management of symptoms .
this could slow disease progression and lower the mortality , therefore improving the quality of life . in this case ,
myotonic dystrophy was diagnosed earlier through clinical symptoms with the assistance of genetic evaluation , suggesting that ophthalmic evaluation could help in diagnosing systemic diseases .
the authors certify that they have obtained all appropriate patient consent forms . in the form the patient(s )
has / have given his / her / their consent for his / her / their images and other clinical information to be reported in the journal .
the patients understand that their names and initials will not be published and due efforts will be made to conceal their identity , but anonymity can not be guaranteed .
the authors certify that they have obtained all appropriate patient consent forms . in the form the patient(s )
has / have given his / her / their consent for his / her / their images and other clinical information to be reported in the journal .
the patients understand that their names and initials will not be published and due efforts will be made to conceal their identity , but anonymity can not be guaranteed .
we report two cases of myotonic dystrophy in one family ; both diagnosed from genetic analysis following ophthalmic indications , but before the manifestation of systemic symptoms . 
 a 39-year - old female visited our clinic for routine examination . 
 mild ptosis , sluggish pupillary response , and bilateral snowflake cataracts were found . 
 fundus examination revealed an increased cup - to - disc ratio ( cdr ) in both eyes and a defect in the retinal nerve fiber layer in the right eye . 
 intraocular pressure was low , but within the normal range in both eyes . because cataracts are characteristic of myotonic dystrophy , we suggested that her 14-year - old daughter , who did not have any systemic complaints , undergo ophthalmic examination . 
 she also had mild ptosis and snowflake cataracts . 
 both patients underwent genetic evaluation and were diagnosed with myotonic dystrophy caused by unstable expansion of cytosine - thymine - guanine trinucleotide repeats in the dystrophia myotonica - protein kinase gene . 
 ophthalmologists can diagnose myotonic dystrophy based on clinical and genetic findings , before the manifestation of systemic abnormalities .