Digital Photography in the Diagnosis and Follow-up of Ocular Diseases

Purpose: The aim of the present study was to develop and test new digital imaging equipment and methods for diagnosis and follow-up of ocular diseases. Methods: The whole material comprised 398 subjects (469 examined eyes), including 241 patients with melanocytic choroidal tumours, 56 patients with melanocytic iris tumours, 42 patients with diabetes, a 52-year old patient with chronic phase of VKH disease, a 30-year old patient with an old blunt eye injury, and 57 normal healthy subjects. Digital 50° (Topcon TRC 50 IA) and 45° (Canon CR6-45NM) fundus cameras, a new handheld digital colour videocamera for eye examinations (MediTell), a new subtraction method using the Topcon Image Net Program (Topcon corporation, Tokyo, Japan), a new method for digital IRT imaging of the iris we developed, and Zeiss photoslitlamp with a digital camera body were used for digital imaging. Results: Digital 50° red-free imaging had a sensitivity of 97.7% and two-field 45° and 50° colour imaging a sensitivity of 88.9-94%. The specificity of the digital 45°-50° imaging modalities was 98.9-100% versus the reference standard and ungradeable images that were 1.2-1.6%. By using the handheld digital colour video camera only, the optic disc and central fundus located inside 20° from the fovea could be recorded with a sensitivity of 6.9% for detection of at least mild NPDR when compared with the reference standard. Comparative use of digital colour, red-free, and red light imaging showed 85.7% sensitivity, 99% specificity, and 98.2 % exact agreement versus the reference standard in differentiation of small choroidal melanoma from pseudomelanoma. The new subtraction method showed growth in four of 94 melanocytic tumours (4.3%) during a mean ±SD follow-up of 23 ± 11 months. The new digital IRT imaging of the iris showed the sphincter muscle and radial contraction folds of Schwalbe in the pupillary zone and radial structural folds of Schwalbe and circular contraction furrows in the ciliary zone of the iris. The 52-year-old patient with a chronic phase of VKH disease showed extensive atrophy and occasional pigment clumps in the iris stroma, detachment of the ciliary body with severe ocular hypotony, and shallow retinal detachment of the posterior pole in both eyes. Infrared transillumination imaging and fluorescein angiographic findings of the iris showed that IR translucence (p=0.53), complete masking of fluorescence (p=0.69), presence of disorganized vessels (p=0.32), and fluorescein leakage (p=1.0) at the site of the lesion did not differentiate an iris nevus from a melanoma. Conclusions: Digital 50° red-free and two-field 50° or 45° colour imaging were suitable for DR screening, whereas the handheld digital video camera did not fulfill the needs of DR screening. Comparative use of digital colour, red-free and red light imaging was a suitable method in the differentiation of small choroidal melanoma from different pseudomelanomas. The subtraction method may reveal early growth of the melanocytic choroidal tumours. Digital IRT imaging may be used to study changes of the stroma and posterior surface of the iris in various diseases of the uvea. It contributed to the revealment of iris atrophy and serous detachment of the ciliary body with ocular hypotony together with the shallow retinal detachment of the posterior pole as new findings of the chronic phase of VKH disease. Infrared translucence and angiographic findings are useful in differential diagnosis of melanocytic iris tumours, but they cannot be used to determine if the lesion is benign or malignant.

Tämä väitöskirja koostuu viidestä osatyöstä. Niistä ensimmäisessä käsitellään diabeettisen retinopatian seulontaa digitaalisilla silmänpohjakameroilla. Tutkimuksessa arvioidaan mm. kameran kuvakulman, kuvien arvioijien koulutuksen ja mahdollisesti käytetyn filtterin vaikutusta kuvaustapahtumaan ja saatuun lopputulokseen. Väitöskirjan toisessa osassa arvioidaan silmänpohjan melanosyyttisiä kasvaimia ja niiden tunnistamista muiden leesioiden joukosta. Tutkimuksessa esitellään eri valon aallonpituuksilla saatuja kuvauslöydöksiä sekä menetelmä leesion koon seuraamiseksi digitaalitekniikalla. Väitöskirjan kolme viimeistä osaa muodostavat keskenään tiukemman kokonaisuuden, jossa esitellään uusi silmän etuosan infrapunatransilluminaatiokuvantamismenetelmä ja sillä saatuja tuloksia. Tästä menetelmästä tuodaan esille erityisesti Vogt-Koyanagi-Harada-syndroomasta ja iriksen melanosyyttisistä kasvaimista otettuja kuvia. Väitöskirja keskittyy tuomaan digitaalisen kuvantamistekniikan eri aspekteja ja käyttömahdollisuuksia. Digitaalista kuvantamistekniikkaa on käytetty etuna sekä koejärjestelyjen suunnittelussa, itse kuvien ottamisessa, kuvien varastoinnissa ja analysoinnissa.